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PRACTICE GUIDELINE: FULL TEXT

2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease

American College of Cardiology Foundation American Heart Association Task Force on Practice Guidelines American Association for Thoracic Surgery American College of Radiology American Stroke Association Society of Cardiovascular Anesthesiologists Society for Cardiovascular Angiography and Interventions Society of Interventional Radiology Society of Thoracic Surgeons Society for Vascular Medicine North American Society for Cardiovascular Imaging, Loren F. Hiratzka, MD, Chair^_*, George L. Bakris, MD, WRITING GROUP MEMBER, Joshua A. Beckman, MD, MS, WRITING GROUP MEMBER, Robert M. Bersin, MD, WRITING GROUP MEMBER, Vincent F. Carr, DO, WRITING GROUP MEMBER^||, Donald E. Casey, Jr, MD, MPH, MBA, WRITING GROUP MEMBER^¶, Kim A. Eagle, MD, WRITING GROUP MEMBER^_*,#, Luke K. Hermann, MD, WRITING GROUP MEMBER^_**, Eric M. Isselbacher, MD, WRITING GROUP MEMBER^_*, Ella A. Kazerooni, MD, MS, WRITING GROUP MEMBER, Nicholas T. Kouchoukos, MD, WRITING GROUP MEMBER, Bruce W. Lytle, MD, WRITING GROUP MEMBER, Dianna M. Milewicz, MD, PhD, WRITING GROUP MEMBER, David L. Reich, MD, WRITING GROUP MEMBER^||||, Souvik Sen, MD, MS, WRITING GROUP MEMBER^¶¶, Julie A. Shinn, RN, MA, CCRN, WRITING GROUP MEMBER, Lars G. Svensson, MD, PhD, WRITING GROUP MEMBER^##, David M. Williams, MD, WRITING GROUP MEMBER^#,_***

Key Words: ACC/AHA Clinical Practice Guideline • thoracic aortic disease • thoracic aortic dissection • thoracic aortic aneurysm • intramural hematoma • genetic syndromes associated with thoracic aortic aneurysm • emergency department • acute thoracic aortic disease presentation and evaluation

	ACCF/AHA Task Force Members

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

	Table of Contents

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 

Preamble.......e31

1 Introduction.......e31

1.1 Methodology and Evidence Review.......e31

1.2 Organization of the Writing Committee.......e32

1.3 Document Review and Approval.......e32

1.4 Scope of the Guideline.......e33

1.4.1 Critical Issues.......e35

1.5 Glossary of Terms and Abbreviations Used Throughout Guideline.......e35

2 The Thoracic Aorta.......e36

2.1 The Normal Aorta.......e36

2.2 Normal Thoracic Aortic Diameter.......e36

3 Thoracic Aortic Histopathology.......e37

3.1 Atherosclerosis.......e37

3.2 Aneurysms and Dissections.......e37

3.3 Vasculitis and Inflammatory Diseases.......e38

4 Imaging Modalities.......e39

4.1 Recommendations for Aortic Imaging Techniques to Determine the Presence and Progression of Thoracic Aortic Disease.......e39

4.2 Chest X-Ray.......e40

4.3 Computed Tomographic Imaging.......e40

4.3.1 Computed Tomographic Imaging Technique.......e42

4.4 Magnetic Resonance Imaging.......e42

4.4.1 Magnetic Resonance Imaging Technique .......e43

4.4.2 Black Blood Imaging.......e43

4.4.3 Noncontrast White Blood Imaging.......e43

4.4.4 Contrast-Enhanced Magnetic Resonance Angiography.......e43

4.4.5 Phase Contrast Imaging.......e43

4.5 Standards for Reporting of the Thoracic Aorta on Computed Tomography and Magnetic Resonance Imaging.......e43

4.6 Angiography.......e44

4.7 Echocardiography.......e45

4.7.1 Echocardiographic Criteria for Thoracic Aortic Aneurysms.......e45

4.7.2 Echocardiographic Criteria for Aortic Dissection.......e45

4.7.2.1 Diagnostic Accuracy of Echocardiography for Aortic Dissection.......e46

4.7.2.2 Diagnostic Accuracy of Echocardiography for Acute Intramural Hematoma.......e46

4.7.2.3 Role of Echocardiography in Following Patients With Chronic Aortic Disease.......e47

5 Genetic Syndromes Associated With Thoracic Aortic Aneurysms and Dissections.......e47

5.1 Recommendations for Genetic Syndromes.......e47

5.1.1 Marfan Syndrome.......e48

5.1.2 Loeys-Dietz Syndrome.......e49

5.1.3 Ehlers-Danlos Syndrome, Vascular Form or Type IV.......e49

5.1.4 Turner Syndrome.......e49

5.1.5 Other Genetic Syndromes With Increased Risk for Thoracic Aortic Aneurysms and Dissections.......e50

5.1.6 Recommendations for Familial Thoracic Aortic Aneurysms and Dissections.......e50

5.2 Summary.......e51

6 Other Cardiovascular Conditions Associated With Thoracic Aortic Aneurysm and Dissection.......e52

6.1 Recommendations for Bicuspid Aortic Valve and Associated Congenital Variants in Adults.......e52

6.2 Aberrant Right Subclavian Artery.......e53

6.3 Coarctation of the Aorta.......e53

6.4 Right Aortic Arch.......e53

7 Inflammatory Diseases Associated With Thoracic Aortic Disease.......e53

7.1 Recommendations for Takayasu Arteritis and Giant Cell Arteritis.......e53

7.2 Takayasu Arteritis.......e54

7.3 Giant Cell Arteritis.......e56

7.4 Behçet Disease.......e57

7.5 Ankylosing Spondylitis (Spondyloarthropathies) .......e57

7.6 Infective Thoracic Aortic Aneurysms.......e57

8 Acute Aortic Syndromes.......e58

8.1 Aortic Dissection.......e58

8.1.1 Aortic Dissection Definition.......e58

8.1.2 Anatomic Classification of Aortic Dissection.......e58

8.1.3 Risk Factors for Aortic Dissection.......e61

8.1.4 Clinical Presentation of Acute Thoracic Aortic Dissection.......e62

8.1.4.1 Symptoms of Acute Thoracic Aortic Dissection.......e62

8.1.4.2 Perfusion Deficits and End-Organ Ischemia.......e62

8.1.5 Cardiac Complications.......e64

8.1.5.1 Acute Aortic Regurgitation.......e64

8.1.5.2 Myocardial Ischemia or Infarction.......e64

8.1.5.3 Heart Failure and Shock.......e64

8.1.5.4 Pericardial Effusion and Tamponade.......e64

8.1.6 Syncope.......e64

8.1.7 Neurologic Complications.......e65

8.1.8 Pulmonary Complications.......e65

8.1.9 Gastrointestinal Complications.......e65

8.1.10 Blood Pressure and Heart Rate Considerations.......e65

8.1.11 Age and Sex Considerations.......e65

8.2 Intramural Hematoma.......e66

8.3 Penetrating Atherosclerotic Ulcer.......e67

8.4 Pseudoaneurysms of the Thoracic Aorta.......e67

8.5 Traumatic Rupture of the Thoracic Aorta.......e67

8.6 Evaluation and Management of Acute Thoracic Aortic Disease.......e68

8.6.1 Initial Evaluation and Management.......e68

8.6.1.1 Recommendations for Estimation of Pretest Risk of Thoracic Aortic Dissection.......e68

8.6.1.2 Laboratory Testing.......e68

8.6.1.3 Recommendations for Screening Tests.......e69

8.6.1.4 Recommendations for Diagnostic Imaging Studies.......e69

8.6.1.5 Recommendations for Initial Management.......e69

8.6.1.6 Recommendations for Definitive Management.......e69

8.6.2 Evaluation and Management Algorithms.......e70

8.6.3 Initial Management.......e71

8.6.3.1 Blood Pressure and Rate Control Therapy.......e71

8.6.3.2 Additional Antihypertensive Therapy.......e73

8.6.3.3 Pain Control.......e73

8.6.3.4 Hypotension.......e73

8.6.3.5 Determining Definitive Management.......e73

8.6.4 Recommendation for Surgical Intervention for Acute Thoracic Aortic Dissection.......e73

8.6.5 Endovascular Interventions.......e73

8.6.6 Principles of Treatment for Intramural Hematoma and Penetrating Atherosclerotic Ulcer.......e74

8.6.6.1 Intimal Defect Without Intramural Hematoma.......e74

8.6.6.2 Intimal Defect With Intramural Hematoma.......e74

8.6.6.3 Recommendation for Intramural Hematoma Without Intimal Defect.......e74

8.7 Treatment for the Management of Traumatic Aortic Rupture.......e74

9 Thoracic Aortic Aneurysms.......e75

9.1 General Approach to the Patient.......e76

9.1.1 Recommendation for History and Physical Examination for Thoracic Aortic Disease.......e76

9.1.1.1 Coronary Artery Disease.......e77

9.1.1.2 Emboli.......e78

9.1.1.3 Associated Renal Ischemia.......e78

9.1.1.4 Associated Mesenteric Ischemia.......e78

9.1.1.5 Associated Peripheral Ischemia.......e78

9.1.2 Differential Diagnosis.......e78

9.1.2.1 Symptoms.......e78

9.1.2.2 Physical Findings.......e78

9.1.3 Considerations for Imaging.......e79

9.2 General Medical Treatment and Risk Factor Management for Patients With Thoracic Aortic Disease.......e79

9.2.1 Recommendation for Medical Treatment of Patients With Thoracic Aortic Diseases.......e79

9.2.1.1 Recommendations for Blood Pressure Control.......e80

9.2.1.2 Recommendation for Dyslipidemia.......e80

9.2.1.3 Recommendation for Smoking Cessation.......e80

9.2.2 Surgical and Endovascular Treatment by Location of Disease.......e81

9.2.2.1 Ascending Aorta and Aortic Sinuses.......e81

9.2.2.1.1 Recommendations for Asymptomatic Patients With Ascending Aortic Aneurysm.......e81

9.2.2.1.2 Recommendation for Symptomatic Patients With Thoracic Aortic Aneurysm.......e81

9.2.2.1.3 Endovascular Grafting for Ascending Aortic Aneurysm.......e82

9.2.2.1.4 Recommendations for Open Surgery for Ascending Aortic Aneurysm.......e82

9.2.2.2 Recommendations for Aortic Arch Aneurysms.......e84

9.2.2.2.1 Open Surgery.......e84

9.2.2.3 Descending Thoracic Aorta and Thoracoabdominal Aorta.......e84

9.2.2.3.1 Recommendations for Descending Thoracic Aorta and Thoracoabdominal Aortic Aneurysms.......e84

9.2.2.3.2 Endovascular Versus Open Surgical Approach.......e85

9.2.2.3.3 End-Organ Preservation During Thoracic Endograft Implantation.......e86

9.2.2.3.4 Periprocedural Complications of Endograft Procedures.......e87

9.2.2.3.5 Open Surgical.......e88

9.2.2.3.6 End-Organ Preservation During Open Thoracoabdominal Repairs.......e89

9.2.2.3.7 Aortic Dissection With Malperfusion.......e89

10 Special Considerations in Pregnant Patients With Aortic Disease.......e89

10.1 Effects of Pregnancy on the Aorta.......e89

10.2 Epidemiology of Chronic and Acute Aortic Conditions in Pregnancy.......e89

10.3 Counseling and Management of Chronic Aortic Diseases in Pregnancy.......e90

10.3.1 Recommendations for Counseling and Management of Chronic Aortic Diseases in Pregnancy.......e89

10.4 Evaluation and Management of Acute Aortic Syndromes During Pregnancy.......e90

11 Aortic Arch and Thoracic Aortic Atheroma and Atheroembolic Disease.......e90

11.1 Recommendations for Aortic Arch and Thoracic Aortic Atheroma and Atheroembolic Disease.......e90

11.2 Clinical Description.......e90

11.3 Risk Factors.......e91

11.4 Diagnosis.......e91

11.5 Treatment.......e91

11.5.1 Anticoagulation Versus Antiplatelet Therapy.......e91

11.5.2 Lipid-Lowering Agent.......e92

11.5.3 Surgical and Interventional Approaches.......e92

12 Porcelain Aorta.......e92

13 Tumors of the Thoracic Aorta.......e93

14 Perioperative Care for Open Surgical and Endovascular Thoracic Aortic Repairs.......e93

14.1 Recommendations for Preoperative Evaluation.......e93

14.1.1 Preoperative Risk Assessment.......e94

14.2 Recommendations for Choice of Anesthetic and Monitoring Techniques.......e95

14.2.1 Temperature Monitoring.......e95

14.2.2 Hemodynamic Monitoring.......e95

14.2.3 Transesophageal Echocardiography.......e96

14.2.4 Transesophageal Echocardiography for Endovascular Repairs of the Descending Thoracic Aorta.......e96

14.3 Airway Management for Descending Thoracic Aortic Repairs.......e96

14.4 Recommendation for Transfusion Management and Anticoagulation in Thoracic Aortic Surgery.......e96

14.5 Organ Protection.......e97

14.5.1 Recommendations for Brain Protection During Ascending Aortic and Transverse Aortic Arch Surgery.......e97

14.5.2 Recommendations for Spinal Cord Protection During Descending Aortic Open Surgical and Endovascular Repairs.......e98

14.5.2.1 Monitoring of Spinal Cord Function in Descending Thoracic Aortic Repairs.......e99

14.5.2.2 Maintenance of Spinal Cord Arterial Pressure.......e99

14.5.2.3 Cerebrospinal Fluid Pressure and Drainage.......e99

14.5.2.4 Hypothermia.......e100

14.5.2.5 Glucocorticoids and Mannitol.......e100

14.5.3 Recommendations for Renal Protection During Descending Aortic Open Surgical and Endovascular Repairs.......e100

14.6 Complications of Open Surgical Approaches.......e100

14.7 Mortality Risk for Thoracic Aortic Surgery.......e101

14.8 Postprocedural Care.......e102

14.8.1 Postoperative Risk Factor Management.......e102

14.8.2 Recommendations for Surveillance of Thoracic Aortic Disease or Previously Repaired Patients.......e102

15 Nursing Care and Patient/Family Education.......e103

15.1 Nursing Care of Medically Managed Patients.......e103

15.2 Preprocedural Nursing Care.......e103

15.3 Postprocedural Nursing Care.......e103

15.4 Nursing Care of Surgically Managed Patients.......e104

16 Long-Term Issues.......e105

16.1 Recommendation for Employment and Lifestyle in Patients With Thoracic Aortic Disease.......e105

17 Institutional/Hospital Quality Concerns.......e106

17.1 Recommendations for Quality Assessment and Improvement for Thoracic Aortic Disease.......e106

17.2 Interinstitutional Issues.......e107

18 Future Research Directions and Issues.......e107

18.1 Risks and Benefits of Current Imaging Technologies.......e107

18.2 Mechanisms of Aortic Dissection.......e108

18.3 Treatment of Malperfusion and Reperfusion Injury.......e108

18.4 Gene-Based Mechanisms and Models.......e108

18.4.1 Aortic Disease Management Based on the Underlying Genetic Defects.......e108

18.4.2 Biomarkers for Acute Aortic Dissection.......e108

18.4.3 Genetic Defects and Molecular Pathway Analyses.......e108

18.4.4 Clinical Trials for Medical Therapy for Aortic Aneurysms.......e108

18.5 Aortic Atheroma and Atherosclerosis Identification and Treatment.......e108

18.6 Prediction Models of Aortic Rupture and the Need for Preemptive Interventions.......e108

18.7 National Heart, Lung, and Blood Institute Working Group Recommendations.......e108

References.......e109

Appendix 1. Author Relationships With Industry and Other Entities.......e126

Appendix 2. Reviewer Relationships With Industry and Other Entities.......e128

Appendix 3. Abbreviation List.......e130

	Preamble

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

The American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) have jointly engaged in the production of guidelines in the area of cardiovascular disease since 1980. The ACCF/AHA Task Force on Practice Guidelines is charged with developing, updating, and revising practice guidelines for cardiovascular diseases and procedures, and the Task Force directs and oversees this effort. Writing committees are charged with assessing the evidence as an independent group of authors to develop, update, or revise recommendations for clinical practice.

Experts in the subject under consideration have been selected from both organizations to examine subject-specific data and write guidelines in partnership with representatives from other medical practitioner and specialty groups. Writing committees are specifically charged to perform a formal literature review, weigh the strength of evidence for or against particular treatments or procedures, and include estimates of expected health outcomes where data exist. Patient-specific modifiers, comorbidities, and issues of patient preference that may influence the choice of tests or therapies are considered. When available, information from studies on cost is considered, but data on efficacy and clinical outcomes constitute the primary basis for recommendations in these guidelines.

The ACCF/AHA Task Force on Practice Guidelines makes every effort to avoid actual, potential, or perceived conflicts of interest that may arise as a result of industry relationships or personal interests among the writing committee. Specifically, all members of the writing committee, as well as peer reviewers of the document, are asked to disclose all current relationships and those 24 months prior to initiation of the writing effort that may be perceived as relevant. All guideline recommendations require a confidential vote by the writing committee and must be approved by a consensus of the members voting. Members who were recused from voting are noted on the title page of this document. Members must recuse themselves from voting on any recommendation where their relationships with industry (RWI) apply. If a writing committee member develops a new relationship with industry during his/her tenure, he/she is required to notify guideline staff in writing. These statements are reviewed by the Task Force on Practice Guidelines and all members during each conference call and/or meeting of the writing committee, updated as changes occur, and ultimately published as an appendix to the document. For detailed information regarding guideline policies and procedures, please refer to the methodology manual for ACCF/AHA Guideline Writing Committees (1). RWI and other entities pertinent to this guideline for authors and peer reviewers are disclosed in Appendixes 1 and 2, respectively. Disclosure information for the ACCF/AHA Task Force on Practice Guidelines is also available online at (http://www.acc.org/about/overview/ClinicalDocumentsTaskForces.cfm).

These practice guidelines are intended to assist healthcare providers in clinical decision making by describing a range of generally acceptable approaches for diagnosis, management, and prevention of specific diseases or conditions. Clinicians should consider the quality and availability of expertise in the area where care is provided. These guidelines attempt to define practices that meet the needs of most patients in most circumstances. The recommendations reflect a consensus after a thorough review of the available current scientific evidence and are intended to improve patient care. The Task Force recognizes that situations arise where additional data are needed to better inform patient care; these areas will be identified within each respective guideline when appropriate.

Patient adherence to prescribed and agreed upon medical regimens and lifestyles is an important aspect of treatment. Prescribed courses of treatment in accordance with these recommendations are effective only if they are followed. Because lack of patient understanding and adherence may adversely affect outcomes, physicians and other healthcare providers should make every effort to engage the patient's active participation in prescribed medical regimens and lifestyles.

If these guidelines are used as the basis for regulatory or payer decisions, the goal should be improvement in quality of care and aligned with the patient's best interest. The ultimate judgment regarding care of a particular patient must be made by the healthcare provider and the patient in light of all of the circumstances presented by that patient. Consequently, there are circumstances in which deviations from these guidelines are appropriate.

The guidelines will be reviewed annually by the ACCF/AHA Task Force on Practice Guidelines and considered current unless they are updated, revised, or withdrawn from distribution.

Alice K. Jacobs, MD, FACC, FAHA

Chair, ACCF/AHA Task Force on Practice Guidelines

Sidney C. Smith, Jr, MD, FACC, FAHA

Immediate Past Chair, ACCF/AHA Task Force on Practice Guidelines

	1. Introduction

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
1.1 Methodology and Evidence Review.   The writing committee conducted a comprehensive search of the medical and scientific literature through the use ofPubMed/MEDLINE. Searches were limited to publications written in the English language. Compiled reports were reviewed and additional articles were provided by committee members. Specifically targeted searches were conducted on the following subtopics: acute aortic dissection, ankylosing spondylitis, aortic dissection and litigation, aortic neoplasm, aortic tumors, Behçet disease, bicuspid aortic valve, calcified aorta, chronic dissection, coarctation of the aorta, D-dimer, dissecting aneurysm, Ehlers-Danlos syndrome, endovascular and aortic aneurysms, medial degeneration, porcelain aorta, giant cell arteritis, imaging and thoracic aortic disease, inflammatory disease, intramural hematoma, Loeys-Dietz syndrome, Marfan syndrome, Noonan syndrome, penetrating aortic ulcer, polycystic kidney disease, thoracic and aortic aneurysms, thoracic aortic disease and patient care, thoracic aortic disease and surgery, thoracic aorta and Kawasaki disease, Takayasu arteritis, thoracoabdominal and aorta or aortic disease, and Turner syndrome. More than 850 references were reviewed, with 829 used as the primary evidence base for the final guideline. The ACCF/AHA Task Force on Practice Guidelines methodology processes were followed to write the text and recommendations. In general, published manuscripts appearing in journals listed in Index Medicus were used as the evidence base. Published abstracts were used only for emerging information but were not used in the formulation of recommendations.

The committee reviewed and ranked evidence supporting current recommendations with the weight of evidence ranked as Level A if the data were derived from multiple randomized clinical trials or meta-analyses. The committee ranked available evidence as Level B when data were derived from a single randomized trial or nonrandomized studies. Evidence was ranked as Level C when the primary source of the recommendation was consensus opinion, case studies, or standard of care. In the narrative portions of these guidelines, evidence is generally presented in chronological order of development. Studies are identified as observational, retrospective, prospective, or randomized. For certain conditions for which inadequate data are available, recommendations are based on expert consensus and clinical experience and are ranked as Level C. An analogous example is the use of penicillin for pneumococcal pneumonia, where there are no randomized trials and treatment is based on clinical experience. When recommendations at Level C are supported by historical clinical data, appropriate references (including clinical reviews) are cited if available. For issues where sparse data are available, a survey of current practice among the clinicians on the writing committee formed the basis for Level C recommendations and no references are cited. The schema for classification of recommendations and level of evidence is summarized in Table 1, which also illustrates how the grading system provides an estimate of the size of the treatment effect and an estimate of the certainty of the treatment effect.

The writing committee recognized that the evidence base for this guideline is less robust in terms of randomized clinical trials than prior ACCF/AHA guidelines, particularly those focused on coronary artery disease (CAD) and heart failure. As the reader will discern, much of the evidence base for this topic consists of cohort studies and retrospective reviews, which largely emanate from centers with a specialized interest in specific types of thoracic aortic disease. The writing committee attempted to focus on providing the practitioner with recommendations for evaluation and treatment wherever possible and where controversy exists, identified as such in the text.

The writing committee acknowledges the expertise of the highly experienced and effective practice guidelines staff of the ACCF and AHA. The writing committee chair also acknowledges the commitment and dedication of the diverse writing committee members who were able to put aside issues of specialty "turf" and focus on providing the medical community with a guideline aimed at optimal patient care.

1.2 Organization of the Writing Committee.   The guideline was written by a committee comprised of experts in cardiovascular medicine, surgery, radiology, and nursing. For many of the previous ACCF/AHA practice guidelines, writing expertise has been available within these 2 organizations. Because of the broad scope and diversity of thoracic aortic diseases, as well as the specialists who treat such patients, the ACCF and AHA sought greater involvement from many specialty organizations. Most, but not all, specialty organizations that represent the major stakeholders caring for patients with thoracic aortic diseases provided writing committee members and financial support of the project, and they are recognized as marquee level partners with the ACCF and AHA. These organizations included the American Association for Thoracic Surgery (AATS), American College of Radiology (ACR), American Stroke Association (ASA), Society of Cardiovascular Anesthesiologists (SCA), Society for Cardiovascular Angiography and Interventions (SCAI), Society of Interventional Radiology (SIR), Society of Thoracic Surgeons (STS), and Society for Vascular Medicine (SVM). The American College of Emergency Physicians (ACEP) and the American College of Physicians (ACP) were also represented on the writing committee. Where additional expertise was needed, the scientific councils of the AHA were contacted for writing committee representatives. Representation was provided or facilitated by the Councils on Cardiovascular Nursing, Cardiovascular Surgery and Anesthesia, Cardiovascular Radiology and Intervention, and Clinical Cardiology, Council for High Blood Pressure Research, and Stroke Council.

1.3 Document Review and Approval.   This document was reviewed by 3 outside reviewers nominated by the ACCF and 2 outside reviewers nominated by the AHA, as well as 1 or 2 reviewers from each of the following organizations: the AATS, ACP, ACEP, ACR, ASA, SCA, SCAI, SIR, STS, and the SVM. It was also reviewed by 6 individual content reviewers—2 content reviewers from the ACCF Catherization Committee and 1 content reviewer from the ACCF Interventional Council. All reviewer RWI information was collected and distributed to the writing committee and is published in this document (see Appendix 2).

This document was approved for publication by the governing bodies of the ACCF and the AHA and the AATS, ACR, ASA, SCA, SCAI, SIR, STS, and SVM and was endorsed by the North American Society for Cardiovascular Imaging.

1.4 Scope of the Guideline.   The term "thoracic aortic disease" encompasses a broad range of degenerative, structural, acquired, genetic-based, and traumatic disease states and presentations. According to the Centers for Disease Control and Prevention death certificate data, diseases of the aorta and its branches account for 43 000 to 47 000 deaths annually in the United States (2). The precise number of deaths attributable to thoracic aortic diseases is unclear. However, autopsy studies suggest that the presentation of thoracic aortic disease is often death due to aortic dissection (AoD) and rupture, and these deaths account for twice as many deaths as attributed to ruptured abdominal aortic aneurysms (AAAs) (3). The diagnosis of acute thoracic AoD or rupture is often difficult and delayed, and errors in diagnosis may account for deaths otherwise attributed to cardiac arrhythmia, myocardial infarction (MI), pulmonary embolism, or mesenteric ischemia.

The University HealthSystem Consortium (UHC) is an alliance of more than 100 academic medical centers and affiliate hospitals. UHC's Clinical DataBase/Resource Manager allows comparison of patient-level risk-adjusted outcomes for performance improvement. The UHC provided the writing committee with a summary of recent information based on ICD-9 codes for thoracic aortic disease–related hospitalizations from the Clinical DataBase/Resource Manager (Tables 2A and 2B). This data table demonstrates a high number of hospital discharges (more than 135 000) for thoracic, abdominal, thoracoabdominal, and "unspecified" aortic aneurysms in the 5-year period between 2002 and 2007. Subcategories include those with dissection, those with rupture, and those with neither. In the most recent 1-year period assessed (fourth quarter 2006 through third quarter 2007), there were nearly 9000 cases representing all patients with thoracic aortic disease discharged from UHC hospitals. Although these data are unavailable for the entire United States, they provide important estimates of the magnitude of the prevalence of thoracic aortic disease. Additional information regarding the patient admission source, particularly those with acute presentations, is pertinent to the discussion regarding interinstitutional transfer (see Section 17.2).

Other practice guidelines developed by ACCF and AHA address the management of patients with cardiac and vascular diseases. The ACCF/AHA guidelines on peripheral arterial disease (4) include recommendations for lower extremity, renal, mesenteric, and abdominal aortic diseases. Data standards on this topic are currently in development, as is a practice guideline on extracranial carotid and vertebral artery diseases. The ACCF/AHA guidelines are published in the Journal of the American College of Cardiology and Circulation and are available on both the ACC (www.acc.org) and AHA (my.americanheart.org) Web sites.

This guideline includes diseases involving any or all parts of the thoracic aorta with the exception of aortic valve diseases (5) and includes the abdominal aorta when contiguous thoracic aortic diseases are present. Specific disease states are described in the following sections, and the reader is referred to the glossary of terminology in Section 1.5 and Appendix 3 for abbreviations used throughout the guideline.

The reader will note that several topics or referenced areas may appear more than once throughout the guideline. This will appear to be redundant to those who choose to read the entire document, but the writing committee believed that because of the multidisciplinary nature of and organizational involvement in this project, individuals representing specific disciplines may choose to read and extract portions of the document for their own use. Inclusion of the narrative text and references was thought to be appropriate to facilitate a more complete understanding for these disciplines and individuals. Accordingly, the organization of the guideline is meant to be less of a textbook presentation of the various topics but rather a more clinically oriented document applicable to a variety of disciplines.

1.4.1 Critical Issues
As the writing committee developed this guideline, several critical issues emerged:

• Thoracic aortic diseases are usually asymptomatic and not easily detectable until an acute and often catastrophic complication occurs. Imaging of the thoracic aorta with computed tomographic imaging (CT), magnetic resonance imaging (MR), or in some cases, echocardiographic examination is the only method to detect thoracic aortic diseases and determine risk for future complications (see Section 4).

• Radiologic imaging technologies have improved in terms of accuracy of detection of thoracic aortic disease. However, as the use of these technologies has increased, so also has the potential risk associated with repeated radiation exposure, as well as contrast medium–related toxicity. Whether these technologies should be used repeatedly as a widespread screening tool is discussed in Section 4. In addition, the writing committee formulated recommendations on a standard reporting format for thoracic aortic findings as discussed in Section 4.5.

• Imaging for asymptomatic patients at high risk based on history or associated diseases is expensive and not always covered by payers.

• For many thoracic aortic diseases, results of treatment for stable, often asymptomatic, but high-risk conditions are far better than the results of treatment required for acute and often catastrophic disease presentations. Thus, the identification and treatment of patients at risk for acute and catastrophic disease presentations (e.g., thoracic AoD, thoracic aneurysm rupture) prior to such an occurrence are paramount to eliminating the high morbidity and mortality associated with acute presentations (see Section 8.1).

• A subset of patients with acute AoD are subject to missed or delayed detection of this catastrophic disease state. Many present with atypical symptoms and findings, making diagnosis even more difficult (see Sections 8.1.4 and 8.6). This issue has come under greater medical-legal scrutiny, and specific cases have been widely discussed in the public domain. Widespread awareness of the varied and complex nature of thoracic aortic disease presentations has been lacking, especially for acute AoD. Risk factors and clinical presentation clues are noted in Section 8.1.4. The collaboration and cosponsorship of multiple medical specialties in the writing of this guideline will provide unique opportunities for widespread dissemination of knowledge to raise the level of awareness among all medical specialties.

• There is rapidly accumulating evidence that genetic alterations or mutations predispose some individuals to aortic diseases (see Section 5). Therefore, identification of the genetic alterations leading to these aortic diseases has the potential for early identification of individuals at risk. In addition, biochemical abnormalities involved in the progression of aortic disease are being identified through studies of patients' aortic samples and animal models of the disease (6,7). The biochemical alterations identified in the aortic tissue have the potential to serve as biomarkers for aortic disease. Understanding the molecular pathogenesis may lead to targeted therapy to prevent aortic disease. Medical and gene-based treatments are beginning to show promise for reducing or delaying catastrophic complications of thoracic aortic diseases (see Section 9.2).

• As noted in Section 18, there are several areas where greater resources for research and both short- and long-term outcomes registries are needed.

1.5 Glossary of Terms and Abbreviations Used Throughout Guideline.  

Aneurysm (or true aneurysm): a permanent localized dilatation of an artery, having at least a 50% increase in diameter compared with the expected normal diameter of the artery in question. Although all 3 layers (intima, media, and adventitia) may be present, the intima and media in large aneurysms may be so attenuated that in some sections of the wall they are undetectable.

Pseudoaneurysm (or false aneurysm): contains blood resulting from disruption of the arterial wall with extravasation of blood contained by periarterial connective tissue and not by the arterial wall layers (see Section 8.4). Such an extravascular hematoma that freely communicates with the intravascular space is also known as a pulsating hematoma (8–10).

Ectasia: arterial dilatation less than 150% of normal arterial diameter.

Arteriomegaly: diffuse arterial dilatation involving several arterial segments with an increase in diameter greater than 50% by comparison to the expected normal arterial diameter.

Thoracoabdominal aneurysm (TAA): aneurysm involving the thoracic and abdominal aorta (see Section 9.2.2.3).

Abdominal aortic aneurysm (AAA): aneurysm involving the infradiaphragmatic abdominal aorta.

Aortic dissection (AoD): disruption of the media layer of the aorta with bleeding within and along the wall of the aorta. Dissection may, and often does, occur without an aneurysm being present. An aneurysm may, and often does, occur without dissection. The term "dissecting aortic aneurysm" is often used incorrectly and should be reserved only for those cases where a dissection occurs in an aneurysmal aorta (see Section 8.1).

	2. The Thoracic Aorta

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
2.1 The Normal Aorta.   The thoracic aorta is divided into 4 parts: the aortic root (which includes the aortic valve annulus, the aortic valve cusps, and the sinuses of Valsalva); the ascending aorta (which includes the tubular portion of the ascending aorta beginning at the sinotubular junction and extending to the brachiocephalic artery origin); the aortic arch (which begins at the origin of the brachiocephalic artery and is the origin of the head and neck arteries, coursing in front of the trachea and to the left of the esophagus and the trachea); and the descending aorta (which begins at the isthmus between the origin of the left subclavian artery and the ligamentum arteriosum and courses anterior to the vertebral column, and then through the diaphragm into the abdomen).

The normal human adult aortic wall is composed of 3 layers, listed from the blood flow surface outward (Figure 1):

Intima: endothelial layer on a basement membrane with minimal ground substance and connective tissue.

Media: bounded by an internal elastic lamina, a fenestrated sheet of elastic fibers; layers of elastic fibers arranged concentrically with interposed smooth muscle cells; bounded by an external elastic lamina, another fenestrated sheet of elastic fibers.

Adventitia: resilient layer of collagen containing the vasa vasorum and nerves. Some of the vasa vasorum can penetrate into the outer third of the media.

View larger version (75K): [in this window] [in a new window] [Download PPT slide]   Figure 1 Aortic pathology associated with thoracic aortic aneurysm involving the ascending aorta. All panels are identically oriented with the adventitia at the top and the intima at the bottom. H&E staining of aortic sections from a control (a) and a patient (b) with a TAA demonstrates medial degeneration with the fragmentation of elastic fibers, accumulation of proteoglycans, and regions of smooth muscle cell loss. Movat staining of aortic sections from control (c) and patient with an aneurysm (d) shows fragmentation of elastic fibers (stained black), loss of smooth muscle cells (cells stained red and nuclei stained violet), and accumulation of proteoglycans (stained blue) in the medial layer. 40x magnification; scale bars represent 500 mcg. H&E indicates hematoxylin and eosin; and TAA, thoracic aortic aneurysm. Modified from Milewicz et al (11).

View larger version (36K): [in this window] [in a new window] [Download PPT slide]   Figure 2 Normal diameter and upper limit of ascending and descending aorta related to age. Reprinted with permission from Hannuksela et al (13).

View larger version (21K): [in this window] [in a new window] [Download PPT slide]   Figure 3 Mean aortic diameters (in cm) at various levels measured by helical CT in 70 adults. Thin lines represent ±2 SDs, representing 95% reference area. CT indicates computed tomographic imaging; and SD, standard deviation. Reprinted with permission from Hager et al (14).

View larger version (65K): [in this window] [in a new window] [Download PPT slide]   Figure 4 Sinus of Valsalva diameter, by body surface area. Left, The 95% normal confidence limits for aortic root diameter at the sinuses of Valsalva in relation to body surface area in adults <40 years of age. Right, The 95% normal confidence limits for the proximal ascending aortic diameter in relation to body surface area in adults <40 years of age. SEE indicates standard error of the estimate. Reprinted with permission from Roman et al (15).

	3. Thoracic Aortic Histopathology

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
3.1 Atherosclerosis.   Atherosclerosis is characterized by intimal lesions called atheromata, or atheromatous or fibrofatty plaques, which protrude into the arterial lumen and weaken the underlying media often associated with calcification. With aging, presence of risk factors, and genetic predisposition, this progresses to complicated lesions with surface defects, hemorrhage, and/or thrombosis. A 1995 consensus document from the AHA defines the types and histologic classes of atherosclerosis (17) (Figure 5).

View larger version (63K): [in this window] [in a new window] [Download PPT slide]   Figure 5 Atherosclerotic lesions. Flow diagram in center column indicates pathways in evolution and progression of human atherosclerotic lesions. Roman numerals indicate histologically characteristic types of lesions defined at the left of the flow diagram. The direction of the arrows indicates the sequence in which characteristic morphologies may change. From Type I to Type IV, changes in lesion morphology occur primarily because of increasing accumulation of lipid. The loop between Types V and VI illustrates how lesions increase in thickness when thrombotic deposits form on their surfaces. Thrombotic deposits may form repeatedly over varied time spans in the same location and may be the principal mechanism for gradual occlusion of medium-sized arteries. Adapted from Stary et al (17).

3.2 Aneurysms and Dissections.   The pathology associated with thoracic aortic aneurysms and dissections was initially termed cystic medial necrosis but this term is a misnomer; the disease is not associated with necrosis of the aorta or with cyst formation. Aortic aneurysm histopathology, more accurately termed medial degeneration, is characterized by disruption and loss of elastic fibers and increased deposition of proteoglycans (Figure 1). Typically, there are areas of loss of smooth muscle cells in the aortic media, but whether there is a total loss of smooth muscle cells in the aortic wall is not clear. There can be atherosclerosis lesions present, but again, these changes are typically superimposed on medial degenerative disease. Although medial degeneration was initially described as a noninflammatory disease, recent literature supports the presence of inflammatory cell infiltration in this disease (18,19).

The biochemical pathways and proteins involved with medial degeneration have not been clearly delineated. However, multiple studies have found increased immunostaining for a subset of matrix metalloproteinases (MMPs) in the media of thoracic aortic aneurysms, particularly MMP-2 and MMP-9 (20–23). Immunostaining of aortic media from patients with Marfan syndrome has demonstrated increases in MMP-2 and MMP-9, which were associated with smooth muscle cells at the borders of areas of medial degeneration and on the surface of disrupted elastic fibers. Elevated MMP-2 and MMP-9 immunostaining has been demonstrated in ascending aneurysms from patients with either tricuspid or bicuspid aortic valves (21,23) and inconsistently in ascending aortic tissue from patients with tricuspid aortic valves (22). These 2 MMPs are known to have elastolytic activity. Variable expression of MMPs and tissue inhibitors of MMPs has also been demonstrated in aortic tissue of patients with Marfan syndrome versus patients without Marfan syndrome (24). Although accumulation of proteoglycans in the aortic media is another consistent finding in thoracic aortic aneurysms, no studies have determined why this accumulation occurs or whether these are causative in nature.

Medial degeneration is also associated with focal loss of vascular smooth muscle cells. Although there are regions of smooth muscle cell loss, morphometric analysis of aortic tissue has suggested that hyperplastic cellular remodeling of the media in ascending thoracic aortic aneurysms may be an initial adaptive response to minimize increased wall stress resulting from vascular dilatation (25). More recent studies of the aortic pathology associated with myosin heavy chain 11, smooth muscle (MYH11), and actin, alpha 2, smooth muscle aorta (ACTA2) mutations leading to ascending aortic aneurysms demonstrate a hyperplastic response by smooth muscle cells in the aortic media. The aortic media in aneurysm tissue taken from patients harboring mutations in these genes demonstrated focal hyperplasia associated with smooth muscle cells that were remarkable for a lack of structured orientation parallel to the lumen of the aorta, but instead, the smooth muscle cells were oriented randomly with respect to one another (26,27).

3.3 Vasculitis and Inflammatory Diseases.   A variety of inflammatory vasculitides may also result in thoracic aortic disease. These include giant cell arteritis (GCA), Takayasu arteritis, and Behçet disease (see Section 7). The pathophysiology of GCA shares important features with Takayasu arteritis (28). T-cell clonal expansion suggests a specific antigenic response, which currently remains unelucidated. The inflammatory response, which begins in the adventitial layer, is marked by augmented cytokine and MMP production causing granuloma formation. Granuloma formation both shields the vessel from the inciting antigen and causes vessel destruction (29). Behçet disease is a vasculitis affecting both arteries and veins, of all sizes.

	4. Imaging Modalities

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
4.1 Recommendations for Aortic Imaging Techniques to Determine the Presence and Progression of Thoracic Aortic Disease.   Class I

1 Measurements of aortic diameter should be taken at reproducible anatomic landmarks, perpendicular to the axis of blood flow, and reported in a clear and consistent format (seeTable 5). (Level of Evidence: C)

2 For measurements taken by computed tomographic imaging or magnetic resonance imaging, the external diameter should be measured perpendicular to the axis of blood flow. For aortic root measurements, the widest diameter, typically at the mid-sinus level, should be used. (Level of Evidence: C)

3 For measurements taken by echocardiography, the internal diameter should be measured perpendicular to the axis of blood flow. For aortic root measurements, the widest diameter, typically at the mid-sinus level, should be used. (Level of Evidence: C)

4 Abnormalities of aortic morphology should be recognized and reported separately even when aortic diameters are within normal limits. (Level of Evidence: C)

5 The finding of aortic dissection, aneurysm, traumatic injury and/or aortic rupture should be immediately communicated to the referring physician. (Level of Evidence: C)

6 Techniques to minimize episodic and cumulative radiation exposure should be utilized whenever possible. (30,31) (Level of Evidence: B)

1 If clinical information is available, it can be useful to relate aortic diameter to the patient's age and body size. (Level of Evidence: C)

Definitive identification or exclusion of thoracic aortic disease or one of its anatomic variants requires dedicated aortic imaging. Selection of the most appropriate imaging study may depend on patient-related factors (i.e., hemodynamic stability, renal function, contrast allergy) and institutional capabilities (i.e., rapid availability of individual imaging modalities, state of the technology, and imaging specialist expertise). Consideration should be given to patients with borderline abnormal renal function (serum creatinine greater than 1.8 to 2.0 mg/dL)—specifically, the tradeoffs between the use of iodinated intravenous contrast for CT and the possibility of contrast-induced nephropathy, and gadolinium agents used with MR and the risk of nephrogenic systemic fibrosis (32).

Radiation exposure should be minimized (31,33–36). The risk of radiation-induced malignancy is the greatest in neonates, children, and young adults (31). Generally, above the age of 30 to 35 years, the probability of radiation-induced malignancy decreases substantially (30,31). For patients who require repeated imaging to follow an aortic abnormality, MR may be preferred to CT. MR may require sedation due to longer examination times and tendency for claustrophobia.

CT as opposed to echocardiography can best identify thoracic aortic disease, as well as other disease processes that can mimic aortic disease, including pulmonary embolism, pericardial disease, and hiatal hernia. After intervention or open surgery, CT is preferred to detect asymptomatic postprocedural leaks or pseudoaneurysms because of the presence of metallic closure devices and clips.

We recommend that external aortic diameter be reported for CT or MR derived size measurements. This is important because lumen size may not accurately reflect the external aortic diameter in the setting of intraluminal clot, aortic wall inflammation, or AoD. A recent refinement in the CT measurement of aortic size examines the vessel size using a centerline of flow, which reduces the error of tangential measurement and allows true short-axis measurement of aortic diameter. In contrast to tomographic methods, echocardiography-derived sizes are reported as internal diameter size. In the ascending aorta, where mural thrombus in aneurysms is unusual, the discrepancy between the internal and external aortic diameters is less than it is in the descending or abdominal aorta, where mural thrombus is common. Standardization of aortic diameter measurements is important to the planning of endovascular treatment of an aneurysm, where the diameter of the aorta in the seal zone must be matched to the diameter of an endograft. Here, the choice of internal or external diameter is specified by the manufacturer of the endograft.

4.2 Chest X-Ray.   Routine chest x-ray may occasionally detect abnormalities of aortic contour or size that require definitive aortic imaging. Chest x-ray often serves as a part of the evaluation of patients with potential acute AoD, primarily to identify other causes of patient's symptoms, but also as a screening test to identify findings due to a dilated aorta or bleeding. However, chest x-ray is inadequately sensitive to definitively exclude the presence of AoD in all except the lowest-risk patients and therefore rarely excludes the disease. Pooled data from 10 studies places the predictive sensitivity of a widened mediastinum or an abnormal aortic contour associated with significant thoracic aortic disease at 64% and 71%, respectively (37). In the same analysis, however, including all abnormal radiographic findings increased the sensitivity to 90%, suggesting that a completely normal chest x-ray does lower the likelihood of AoD and may provide meaningful clinical information in very low-risk patients (37). The presence of a widened mediastinum or other radiographic findings suggestive of thoracic aortic disease increases the likelihood of AoD, particularly among patients who lack a clear alternative source for their symptoms. In a blinded prospective study of 216 patients who underwent evaluation for acute thoracic aortic disease, the specificity of chest x-ray for aortic pathology was 86% (38).

For patients with chest trauma, chest x-ray is a poor screening test for the diagnosis of aortic injury (39–41). A sharply demarcated normal mediastinal contour is sometimes used to exclude mediastinal hematoma (suggesting a wide mediastinum, abnormal mediastinal contour, left apical cap, loss of the aortic knob, depression of the left main bronchus, and deviation of an indwelling esophageal tube). However, these signs of hemomediastinum are more often false positive than true positive for aortic injury (40). Figure 6 illustrates the normal appearance of the thoracic aorta, and its components, on a posteroanterior chest x-ray.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 6 Chest x-ray of a normal thoracic aorta. Arrows indicate arch, and arrowheads show ascending and descending aorta.

Reports of newer-generation multidetector helical CT scanners show sensitivities of up to 100% and specificities of 98% to 99% (43–46). Data from the International Registry of Acute Aortic Dissection (IRAD) show that for patients with aortic dissection, CT was the initially used diagnostic modality in 61% of patients and transthoracic echocardiography (TTE) and/or transesophageal echocardiography (TEE) was used first in 33% of patients. Whether this was because the first test was insufficient to diagnose dissection or because additional information about cardiac and aortic valve function was required is unclear (47).

The sequence for CT performed in the potential setting of acute AoD generally would include a noncontrast study to detect subtle changes of IMH (Figure 7), followed by a contrast study to delineate the presence and extent of the dissection flap, identify regions of potential malperfusion, and demonstrate contrast leak indicating rupture. Imaging of the vascular tree from the thoracic inlet to the pelvis, including the iliac and femoral arteries, provides sufficient information to plan surgical or endovascular treatment, if needed. Prompt interpretation and communication of findings to the appropriate treating physicians are essential in the acute setting.

View larger version (72K): [in this window] [in a new window] [Download PPT slide]   Figure 7 Axial CT images demonstrating the value of noncontrast images. Top, Precontrast image demonstrates a high-attenuation aortic hematoma indicating an acute aortic event. Bottom, Images obtained with intravenous contrast material demonstrate the contrast-filled aortic lumen and the hematoma as a relatively lower attenuation band. CT indicates computed tomographic imaging.

View larger version (92K): [in this window] [in a new window] [Download PPT slide]   Figure 8 Traumatic aortic rupture secondary to a motor vehicle crash. Top, Axial CT image demonstrates a traumatic injury with pseudoaneurysm (T) in the proximal descending thoracic aorta, numerous bilateral rib fractures, and small bilateral pleural effusions, with no significant mediastinal hematoma. Bottom, Still image through the thorax further demonstrates the extent of the aortic trauma. See the accompanying full cine video for the bottom panel. CT indicates computed tomographic imaging.

Regarding other thoracic aortic diseases, CT has been shown to have a 92% accuracy for diagnosing abnormalities of the thoracic aorta, in a series of examinations that included 33 thoracic aneurysms, 3 ruptured thoracic aortic aneurysms, 6 PAUs, 5 AoDs, and 2 pseudoaneurysms. In addition, CT correctly predicted the need for hypothermic circulatory arrest during surgical repair in 94% of patients (54). For congenital and inflammatory conditions of the thoracic aorta, the literature is primarily descriptive, and accuracy data are not available.

4.3.1 Computed Tomographic Imaging Technique
Although nonhelical CT scanners are capable of diagnosing thoracic aortic disease, the technique used is axial step-and-shoot technology. Inherent limitations include slow scan speed, relatively poor spatial resolution given thicker collimation used to extend the needed craniocaudal coverage, and inherently a noncontiguous dataset. Any patient motion, even minimal, between the acquisition of each image or cluster of images creates a stair-step artifact on multiplanar and 3-dimensional renderings. Helical CT scanners of 4 and greater detector rows consistently provide volumetric acquisitions of the thoracic aorta. Scanners with 16 and greater detector rows provide isotropic resolution in the x, y, and z axes, which allows the datasets to be reconstructed in the optimum imaging plane best suited to any individual vessel.

Technical parameters recommended for image reconstruction are slices of 3-mm or less thickness with a reconstruction interval of 50% or less than the slice thickness at 50% or greater overlap, tube rotation of 1 second or less, and 120 to 140 kVp (55). ECG gating is particularly useful for ascending aortic disease, eliminating motion artifact at the aortic root that can simulate an AoD (Figure 9), and allowing evaluation of aortic valve morphology and function, as well as evaluation of the proximal coronary arteries. If appropriately acquired, an aorta CT and a complete CT coronary angiogram can be obtained in 1 CT acquisition. For AoD, the scan coverage should start above the aortic arch and extend at least to the aortoiliac bifurcation, and probably the groin. This is important to determine both branch vessel involvement, such as lesion extension into the abdominal aorta and iliac arteries and characterization and diagnosis of malperfusion syndrome, and to evaluate access for percutaneous repair when transluminal therapy is being considered. (For further information on technique parameters and anatomic coverage, see the online-only Data Supplement.)

View larger version (84K): [in this window] [in a new window] [Download PPT slide]   Figure 9 Mimic of aortic dissection created by motion of the aortic root. Top left, Image at the level of the right pulmonary artery demonstrates a normal descending thoracic aorta and pseudodissection of the ascending aorta due to motion artifact that occurs on non–ECG-gated CT examinations (arrow). Top right, Image at the aortic root shows a double contour to the aortic root that may simulate a dissection flap (arrow). Bottom, Still image through the thoracic aorta further delineates the extent of the motion artifact. See the accompanying full cine video. CT indicates computed tomographic imaging; and ECG, electrocardiogram.

Although axial sections remain the mainstay of interpretation, 2- and 3-dimensional reconstructions, such as maximum intensity projection, multiplanar and curved multiplanar reformations, and volume rendering, may augment interpretation and improve communication of the findings (54). To our knowledge, it has not been scientifically shown that the use of these tools increases diagnostic accuracy or diagnostic confidence among specialists. For example, in 1 study multiplanar reconstructions when added to axial images alone changed the interpretation in only 1 case (54). However, 3-dimensional reconstruction is likely to play an important role in the planning of surgical or endovascular approaches.

4.4 Magnetic Resonance Imaging.   MR has been shown to be very accurate in the diagnosis of thoracic aortic disease, with sensitivities and specificities that are equivalent to or may exceed those for CT and TEE (44,58–62). Like CT, MR provides a multiplanar evaluation of the thoracic aorta, and the examination can be extended in coverage to include the length of the aorta and branch vessels, from skull base to the toes. Advantages of MR include the ability to identify anatomic variants of AoD (IMH and PAU), assess branch artery involvement, and diagnose aortic valve pathology and left ventricular dysfunction without exposing the patient to either radiation or iodinated contrast. Disadvantages include prolonged duration of imaging acquisition during which the patient is inaccessible to care providers; inability to use gadolinium contrast in patients with renal insufficiency; contraindication in patients with claustrophobia, metallic implants, or pacemakers; and lack of widespread availability on an emergency basis. Although time-resolved MR techniques are improving, MR often cannot clearly characterize the relationship of an intimal flap and aortic root structures, specifically the coronary arteries. Likely as a result of these considerations, data from IRAD found that MR was the least-used imaging study, used in only 1% of patients as the initial diagnostic study (63). For traumatic injury and congenital and inflammatory conditions of the thoracic aorta, the literature is primarily descriptive, and accuracy data are not available.

4.4.1 Magnetic Resonance Imaging Technique
A comprehensive MR examination of the thoracic aorta may include many components, including black blood imaging, may include basic spin-echo sequences, noncontrast white blood imaging, contrast-enhanced MR angiography using gadolinium based agents, and phase-contrast imaging. MR of the thoracic aorta in the acute setting can be shortened to meet urgent patient assessment needs. The use of each is described more specifically later. MR examinations have become faster, with advances in gradient hardware that have significantly reduced repetition times, resulting in ultrafast MR angiography techniques. However, MR examinations remain 2 to 4 times longer than CT examinations. MR terminology across imaging vendors is less consistent than that of CT; therefore, imaging sequences are described later as general types of sequences without vendor-specific details (58,59).

4.4.2 Black Blood Imaging
Black blood imaging, using spin-echo sequences, is used to evaluate aortic anatomy and morphology (such as aortic size and shape), and the aortic wall for hematoma or other causes of thickening such as vasculitis. They may be repeated after the administration of gadolinium-based contrast agents to identify wall enhancement. These sequences should use ECG gating at end-diastole and may be performed with or without double inversion recovery techniques that null the signal from blood. These sequences generate 2-dimensional images that can be obtained in the axial, sagittal, and coronal planes, as well as the oblique sagittal or "candy cane" view. T1-weighted gradient echo sequences may be used in place of black blood images and are usually performed both before and after contrast administration. They can be obtained in the axial, sagittal, and coronal planes.

4.4.3 Noncontrast White Blood Imaging
This is performed using either basic gradient echo sequences or the more advanced balanced steady-state free precession techniques (SSFP) that are T2*weighted and generate images with subsecond temporal resolution. Signal is generated from blood, making it appear white in the absence of contrast. SSFP techniques use ultrashort repetition times that require MR scanners with high-performance gradients. For the latter, an in-plane resolution of approximately 2.0x1.5 mm² can be obtained using a repetition time of 3.2 ms, TE of 1.6 ms, flip angle of 60 to 70 degrees, and a 256x256 matrix. SSFP techniques can be performed to generate 2-dimensional, 3-dimensional, and cine images; the 2-dimensional images are usually performed in the axial, sagittal, and coronal planes in an interleaved manner and use ECG gating with triggering at end-diastole to generate images in less than 500 ms that do not require breath holding. Cine SSFP sequences require 7- to 9-second breath holding and are usually only performed at specific anatomic locations of interested, as determined by the findings on the previously generated images. For patients who cannot hold their breath, cine SSFP sequences can be performed without using ECG gating or breath holding but with substantially lower spatial and temporal resolution.

4.4.4 Contrast-Enhanced Magnetic Resonance Angiography
For the thoracic aorta, contrast-enhanced MR angiography is usually performed with ECG gating. Although this increases acquisition time, it provides motion-free images of the aortic root and ascending aorta. For patients without a contraindication to receiving a gadolinium-based contrast agent, contrast-enhanced MR angiography is often the sequence of choice from which most of the diagnostic information is obtained. Contrast-enhanced MR angiography images are obtained as a 3-dimensional volumetric dataset, which can be manipulated and viewed in much the same manner as CT scan datasets. Advances in MR, particularly gradient strength, have markedly reduced the acquisition times of contrast-enhanced MR angiography possible to subsecond acquisition times. This temporally resolved subsecond contrast-enhanced MR angiography is particularly useful in critically ill patients or patients who cannot hold their breath, where motion artifact can degrade other sequences that take longer to acquire, with the tradeoff being a reduction of in-plane resolution.

4.4.5 Phase Contrast Imaging
These sequences are usually performed to evaluate gradients across an area of stenosis, across an intimal or cardiac valve. Image contrast is produced by differences in velocity. Images are obtained using ECG gating or triggering. Two-dimensional images are generated that center on the area of concern. Peak flow and velocity measurements may be calculated, and time–flow and time–velocity curves are generated.

4.5 Standards for Reporting of the Thoracic Aorta on Computed Tomography and Magnetic Resonance Imaging.   Viewing and measuring are best accomplished at a picture archiving and communications system workstation or an independent computer workstation, in which the aorta can be rotated into the best orientation to review each segment of the aorta and the aortic branches. This minimizes the chance of inadvertently confusing normal structures for vascular abnormality (Figure 10).

View larger version (93K): [in this window] [in a new window] [Download PPT slide]   Figure 10 Left brachiocephalic vein mimics an intramural hematoma on CT. Axial CT image demonstrates a low-attenuation crescent of material anterior to the innominate artery. CT indicates computed tomographic imaging.

Diameter measurements taken from axial images are inherently incorrect unless the artery being measured is perfectly aligned in cross section on the image (Figure 11). It is preferable to make diameter measurements perpendicular to the longitudinal or flow axis of the aorta to correct for the variable geometry of the aorta. Suggested standard anatomic locations are noted in Figure 12. The use of standardized measurements helps minimize errant reports of significant aneurysm growth due to technique or interreader variability in measuring technique.

View larger version (79K): [in this window] [in a new window] [Download PPT slide]   Figure 11 Markedly tortuous aorta with thoracoabdominal aortic aneurysm demonstrated on (A) 3-dimensional shaded surface display rendering. B and C represent incorrect measurement of the aorta on standard coronal and axial images respectively, while D is an image of the aorta perpendicular to the centerline or axis of the aorta, with the arrow demonstrating the correct location for diameter measurement, which in this case was 7.8 cm.

View larger version (32K): [in this window] [in a new window] [Download PPT slide]   Figure 12 Normal anatomy of the thoracoabdominal aorta with standard anatomic landmarks for reporting aortic diameter as illustrated on a volume-rendered CT image of the thoracic aorta. CT indicates computed tomographic imaging. Anatomic locations: 1, Aortic sinuses of Valsalva; 2, Sinotubular junction; 3, Mid ascending aorta (midpoint in length between Nos. 2 and 4); 4, Proximal aortic arch (aorta at the origin of the innominate artery); 5, Mid aortic arch (between left common carotid and subclavian arteries); 6, Proximal descending thoracic aorta (begins at the isthmus, approximately 2 cm distal to left subclavian artery); 7, Mid descending aorta (midpoint in length between Nos. 6 and 8); 8, Aorta at diaphragm (2 cm above the celiac axis origin); 9, Abdominal aorta at the celiac axis origin. CT indicates computed tomographic imaging.

Disadvantages of angiography compared with other less invasive modalities include 1) not being universally available because it requires the presence of an experienced physician to perform the study; 2) being an invasive procedure that is time consuming and requires exposure to iodinated contrast; 3) having poor ability to diagnose IMH given a lack of luminal disruption; 4) potentially producing false negative results when a thrombosed false lumen prevents adequate opacification to identify the dissection; and 5) reported sensitivities and specificities of angiography for the evaluation of acute AoD that are slightly lower than those for the other less invasive modalities (42,64,65). Thus, CT, MR, and TEE have replaced catheter-based angiography as the first-line diagnostic tests to establish the presence of the acute aortic syndrome (60,63,66,67). Multidetector CT has also largely replaced angiography for the anatomic studies required for treatment planning and monitoring of aortic disease (68).

4.7 Echocardiography.   The aorta and its major branches can be visualized with echocardiography using a variety of imaging fields as well as methods of ultrasound. The suprasternal view is best for visualizing the aortic arch, whereas the aortic root and ascending aorta are best seen in the left (and sometimes right) parasternal projection. When involvement of the innominate artery, left subclavian artery, or left common carotid artery is suspected, orthogonal and longitudinal scanning planes are helpful. Imaging of the descending thoracic aorta is less easily accomplished with echocardiography compared with other imaging modalities. Abdominal scan planes can be used to visualize the caudal descending aorta.

In general, TEE is superior to TTE for assessment of the thoracic aorta. Through the use of multiplane image acquisi-tion, 3-dimensional Doppler TEE is safe and can be performed at the bedside, with a low risk of complications (less than 1% overall, less than 0.03% for esophageal perforation), most of which are related to conscious sedation (69,70). Reconstruction of the aorta can be performed. Intraoperative use of TEE is noted in Sections 14.2.3 and 14.2.4.

4.7.1 Echocardiographic Criteria for Thoracic Aortic Aneurysms
The echocardiographic diagnosis of thoracic aortic aneurysms is determined on demonstration of aortic enlargement relative to the expected aortic diameter, based on age- and body size–adjusted nomograms (Figures 2, 3, 4, and 13). For other aortic segments, such nomograms have not been developed, so aortic dilatation is diagnosed when the aorta exceeds a generally agreed to standard diameter (Table 3) or when a given aortic segment is larger than contiguous aortic segment(s) of apparently normal size. Beyond establishing the presence of aortic enlargement, echocardiography may reveal associated cardiac pathology that suggests the underlying etiology of the aortic disease (e.g., bicuspid aortic valve).

View larger version (70K): [in this window] [in a new window] [Download PPT slide]   Figure 13 Transthoracic echocardiogram of a patient with Marfan syndrome with mitral valve prolapse and 4-cm ascending aortic aneurysm.

View larger version (59K): [in this window] [in a new window] [Download PPT slide]   Figure 14 Arch aneurysm with dissection flap. Top, Arch dissection, 2-dimensional view. Bottom, Arch dissection (arrow) with color-flow Doppler margination.

View larger version (61K): [in this window] [in a new window] [Download PPT slide]   Figure 15 Artifact mimicking dissection. Top left, 2-dimensional view. Top right, Color-flow Doppler without margination. Bottom, Artifact not seen in this view.

4.7.2.1 Diagnostic Accuracy of Echocardiography for Aortic Dissection
TTE has a sensitivity of 77% to 80% and a specificity of 93% to 96% for identification of proximal AoD. For distal AoD, the sensitivity of TTE is lower. TEE improves the diagnostic accuracy substantially, particularly when a patient's body shape, chest wall, or concomitant pulmonary disease restricts the transthoracic windows for aortic imaging. With TEE, sensitivity for proximal AoD is 88% to 98% with a specificity of 90% to 95% (46). A 2006 meta-analysis that evaluated the diagnostic utility of TEE in suspected thoracic AoD included 630 patients from 10 different studies. TEE was shown to both accurately identify and rule out acute AoD with sensitivities and specificities of 98% (95% CI 95% to 99%) and 95% (95% CI 92% to 97%), respectively (46).

Major advantages of TEE include its portability (allowing for bedside patient evaluation), rapid imaging time, and lack of intravenous contrast or ionizing radiation. Additionally, dissection-related cardiac complications can be evaluated including aortic regurgitation, proximal coronary artery involvement, and the presence of tamponade physiology. Disadvantages of TEE include a potential lack of availability (particularly at small centers and during off hours) and sedation requirements that may include endotracheal intubation (73). The accuracy of TEE can be quite operator dependent. For the very distal ascending aorta and the proximal aortic arch, TEE may be limited by a blind spot caused by interposition of the trachea and left main bronchus between the esophagus and aorta. Small, circumscribed AoDs or IMHs in this region are less well visualized by TEE. Another limitation of TEE is its inability to visualize the abdominal aorta; if there is concern of a malperfusion syndrome, an abdominal CT may also be required.

4.7.2.2 Diagnostic Accuracy of Echocardiography for Acute Intramural Hematoma
IMH of the aorta has a distinctly different appearance on echocardiography. In contrast to classic AoD, in IMH there is no mobile intimal flap within the aortic lumen, and in most cases the aortic lumen has a relatively normal round appearance. Instead, in IMH there is thickening of the aortic wall that is typically crescentic in shape and extends along a length of the aorta. In some cases it can be difficult to distinguish the wall thickening of IMH from diffuse aortic atherosclerosis or mural thrombus lining an aortic aneurysm. However, atheroma and mural thrombus protrude from the aortic intima into the lumen, thus giving both the aortic wall and the lumen an irregular shape, whereas in IMH the inner lining of the aortic lumen remains smooth. Moreover, in the presence of intimal calcification, intramural thrombus will present as thickening external to calcification, whereas mural thrombus will be internal to calcification.

4.7.2.3 Role of Echocardiography in Following Patients With Chronic Aortic Disease
Given that TEE is a semi-invasive procedure; it is usually not preferred for surveillance of patients with thoracic aortic diseases. Also, although TTE is noninvasive, its failure to visualize consistently and measure accurately the tubular portion of the ascending thoracic aorta is problematic. It is not typically used to follow aneurysms in that aortic segment. However, because TTE does accurately visualize the aortic root, its primary role as an imaging method for serial follow-up is in patients with aortic disease limited to the root, particularly those with Marfan syndrome. It is also used, often in conjunction with CT or MR, to observe patients with concomitant structural heart disease, such as bicuspid aortic valve, mitral valve prolapse, cardiomegaly, or cardiomyopathy.

	5. Genetic Syndromes Associated With Thoracic Aortic Aneurysms and Dissection

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
5.1 Recommendations for Genetic Syndromes.   Class I

1 An echocardiogram is recommended at the time of diagnosis of Marfan syndrome to determine the aortic root and ascending aortic diameters and 6 months thereafter to determine the rate of enlargement of the aorta. (Level of Evidence: C)

2 Annual imaging is recommended for patients with Marfan syndrome if stability of the aortic diameter is documented. If the maximal aortic diameter is 4.5 cm or greater, or if the aortic diameter shows significant growth from baseline, more frequent imaging should be considered. (Level of Evidence: C)

3 Patients with Loeys-Dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11) should undergo complete aortic imaging at initial diagnosis and 6 months thereafter to establish if enlargement is occurring. (74–77) (Level of Evidence: C)

4 Patients with Loeys-Dietz syndrome should have yearly magnetic resonance imaging from the cerebrovascular circulation to the pelvis. (23,78,79) (Level of Evidence: B)

5 Patients with Turner syndrome should undergo imaging of the heart and aorta for evidence of bicuspid aortic valve, coarctation of the aorta, or dilatation of the ascending thoracic aorta. (80) If initial imaging is normal and there are no risk factors for aortic dissection, repeat imaging should be performed every 5 to 10 years or if otherwise clinically indicated. If abnormalities exist, annual imaging or follow-up imaging should be done. (Level of Evidence: C)

Class IIa

1 It is reasonable to consider surgical repair of the aorta in all adult patients with Loeys-Dietz syndrome or a confirmed TGFBR1 or TGFBR2 mutation and an aortic diameter of 4.2 cm or greater by transesophageal echocardiogram (internal diameter) or 4.4 to 4.6 cm or greater by computed tomographic imaging and/or magnetic resonance imaging (external diameter). (78) (Level of Evidence: C)

2 For women with Marfan syndrome contemplating pregnancy, it is reasonable to prophylactically replace the aortic root and ascending aorta if the diameter exceeds 4.0 cm. (74) (Level of Evidence: C)

3 If the maximal cross-sectional area in square centimeters of the ascending aorta or root divided by the patient's height in meters exceeds a ratio of 10, surgical repair is reasonable because shorter patients have dissection at a smaller size and 15% of patients with Marfan syndrome have dissection at a size less than 5.0 cm. (16,76,81) (Level of Evidence: C)

Class IIb

1 In patients with Turner syndrome with additional risk factors, including bicuspid aortic valve, coarctation of the aorta, and/or hypertension, and in patients who attempt to become pregnant or who become pregnant, it may be reasonable to perform imaging of the heart and aorta to help determine the risk of aortic dissection. (Level of Evidence: C)

5.1.1 Marfan Syndrome
Marfan syndrome is a heritable disorder of the connective tissue with a high penetrance but variable expression. Approximately 25% of patients do not have a family history and represent new cases due to sporadic mutations for the condition. Marfan syndrome results from mutations in the FBN1 gene, with over 600 mutations currently entered into the FBN1 mutation database causing Marfan syndrome or related conditions (http://www.umd.be/). The FBN1 gene encodes fibrillin-1, a large glycoprotein that is secreted from cells and deposited in the extracellular matrix in structures called microfibrils. Microfibrils are found at the periphery of elastic fibers, including the elastic fibers in the medial layer of the ascending aorta, and in tissues not associated with elastic fibers (82). Only 12% of FBN1 mutations causing Marfan syndrome have been observed more than once in unrelated individuals, a fact that complicates using mutational detection for diagnosis. A second locus for Marfan syndrome, termed MFS2, was recently identified to be caused by mutations in the transforming growth factor-beta type II receptor (TGFBR2) (83). The phenotype of this locus may overlap for Loeys-Dietz syndrome. The criteria for Marfan syndrome is based primarily on clinical findings in the various organ systems affected in the Marfan syndrome, along with family history and FBN1 mutations status (84).

The cardinal features of Marfan syndrome involve the cardiovascular, ocular, and skeletal systems. Patients with Marfan syndrome are highly predisposed to thoracic aortic aneurysm and/or dissection, with virtually every patient with the syndrome having evidence of aortic disease at some point during their lifetime. Other cardiovascular manifestations include valvular disease, primarily mitral valve prolapse and regurgitation (85). Aortic regurgitation can result from distortion of the aortic valve cusps by an enlarged aortic root. The skeletal manifestations reflect overgrowth of the long bones and include arachnodactyly, dolichostenomelia, kyphoscoliosis, dolichocephaly, and pectus deformities. Abnormalities in the connective tissues are also manifested as joint laxity, recurrent or incisional hernias, striae atrophica, and dural ectasia (84). The ocular manifestation that is both sensitive and fairly specific for Marfan syndrome is ectopia lentis or lens dislocation. The presence of ectopia lentis is a particularly useful clinical finding to differentiate Marfan syndrome from Loeys-Dietz syndrome (78).

Most patients with Marfan syndrome present with dilatation of the aortic root/ascending aorta or Type A dissection. Internal aortic diameter measured at the sinuses of Valsalva provides a baseline for future evaluations because this is the aortic segment that dilates in Marfan syndrome. Of note, echocardiographic studies measure the internal diameter, whereas most patients undergo definitive imaging by CT and/or MR, which measures the external diameter (expected to be 0.2 to 0.4 cm larger than internal diameter), and external diameter is the measurement used in most cases to determine the threshold for surgical repair. There is growing awareness of the importance of relating this measurement to normal values based on age and body surface area (15) (Table 4). The severity of the aortic disease is related to the degree and segment length of aortic dilatation with dilatation limited to the sinuses of Valsalva having a less malignant prognosis than dilatation that extends to the aortic arch (86). After diagnosis, follow-up imaging studies are recommended at 6 months and then annually if stability is documented based on the high likelihood of aortic disease progression. In most cases, TTE can be used to monitor the size of the sinuses of Valsalva.

A subset of patients present with Type B dissection, and a rare patient will present with AAA. The poor outcome of patients with Marfan syndrome with acute Type B dissections has led some to advocate early surgical repair (87).

Studies addressing the efficacy of beta blockade in patients with Marfan syndrome have shown slower aortic root growth, fewer cardiovascular end points (defined as aortic regurgitation, dissection, surgery, heart failure, or death), and improved survival (88). Patients continue to enlarge their aorta and dissect on therapy, so such medication does not preclude the need for routine imaging and prophylactic aortic repair when the diameter of the aorta warrants repair. It is also important to note that significant aortic root dilatation is correlated negatively with therapeutic response (88). Recent studies in a mouse model of Marfan syndrome with aortic disease similar to that seen in humans showed that treatment with losartan normalized aortic root growth (6), and a clinical trial using losartan in Marfan syndrome patients under the age of 25 years is in progress (89,90) (see Section 9.2.1.1).

Surgical repair of the dilated aortic root/ascending aorta for patients with Marfan syndrome is usually performed at a threshold of a external diameter of 5.0 cm (91), smaller than that for other patients because of the greater tendency for AoD at a smaller diameter (see Section 9.2.2.1). Factors that will prompt repair at an external diameter of less than 5.0 cm are rapid growth defined as greater than 0.5 cm/y, family history of AoD at a diameter less than 5.0 cm, or the presence of significant aortic regurgitation.

After prophylactic repair of the ascending aorta, the arch and descending aorta are sites for later-onset aneurysms and dissections in patients with Marfan syndrome, prompting the need for routine imaging of the arch and descending aorta. Survival in patients with Marfan syndrome has been significantly improved with medical and surgical management of the aortic disease (76,92,93). The David valve sparing reimplantation operation for suitable patients undergoing elective aortic root surgery at centers with a high volume of these cases has become standard practice (76,92–99), although some have reported less-optimal long-term results with valve-sparing procedures (100,101).

Pregnant patients with Marfan syndrome are at increased risk for AoD if the aortic diameter exceeds 4 cm (102) (see Section 10). All women with Marfan syndrome warrant frequent cardiovascular monitoring throughout pregnancy and into the puerperium. Limited data on the treatment of women with Marfan syndrome who experience dissections during pregnancy suggest a better outcome with cesarean section with concomitant aortic repair (103).

5.1.2 Loeys-Dietz Syndrome
The Loeys-Dietz syndrome is an autosomal dominant aortic aneurysm syndrome with involvement of many other systems (78,104). Loeys-Dietz syndrome results from mutations in either the transforming growth factor receptor Type I or II (TGFBR1 or TGFBR2) genes and the diagnosis is confirmed through mutational analysis of these genes (105).

The disease is characterized by the triad of arterial tortuousity and aneurysms, hypertelorism and bifid uvula or cleft palate, or a uvula with a wide base or prominent ridge on it. The arterial tortuousity is most commonly observed in the head and neck vessels but can occur in other vessels. These patients also have a spectrum of other features, which include the following: velvety and translucent skin, craniosynostosis, malar hypoplasia, retrognathia, blue sclera, patent ductus arteriosus, skeletal features similar to Marfan syndrome, dural ectasia, atrial septal defects, developmental delay, cervical spine abnormalities, and joint laxity. The vascular disease in these patients is particularly aggressive with a mean age of death of 26 years (78). Most patients have aortic root aneurysms (98%) that lead to AoD. Because there are multiple reports of AoD occurring in patients with Loeys-Dietz when the aortic diameter was less than 5.0 cm, repair is recommended at smaller diameters (78) (see Section 5.1). For young children with severe systemic manifestations of Loeys-Dietz syndrome, specifically prominent craniofacial features that are associated with more severe aortic disease, once the aortic diameter exceeds the 99th percentile for age and the aortic valve annulus reaches 1.8 to 2.0 cm, prophylactic surgery allows for the placement of a graft of sufficient size to accommodate growth. Of note, echocardiographic examinations that measure the internal aortic diameter were used in these studies to determine the threshold for surgical repair.

Patients with Loeys-Dietz also develop aneurysms of other vessels (53%), leading to the recommendation that they have yearly MR imaging from the cerebrovascular circulation to the pelvis. Current studies indicate that aggressive surgical management of the aneurysms in these patients can be achieved with few complications (23,78). Surgical procedures in patients with Loeys-Dietz syndrome are not complicated by tissue fragility (23,79).

5.1.3 Ehlers-Danlos Syndrome, Vascular Form or Type IV
The vascular form of Ehlers-Danlos syndrome is a rare autosomal dominant disorder characterized by easy bruising, thin skin with visible veins, characteristic facial features, and rupture of arteries, uterus, or intestines. Rupture of the gastrointestinal tract is more likely to occur prior to arterial rupture, and the majority of patients survive the gastrointestinal rupture (106). Most of the fatal complications are caused by arterial rupture, with most deaths attributable to arterial dissections or ruptures involving primarily the thoracic or abdominal arteries, including AoDs and ruptures. These arterial ruptures lead to reduced life expectancy, with the median survival of only 48 years, and often no aneurysms are documented. If the rupture of an artery is life threatening, it can be surgically repaired, but tissue fragility, tendency to hemorrhage extensively, and poor wound healing may complicate the surgical repair (107). Whether there is a role for the repair of unruptured aneurysms in patients with this syndrome is not clear, which is in contrast to Loeys-Dietz syndrome, where a role for prophylactic surgical repair of aneurysms is already well established. Nevertheless, when these patients present with AoD or aortic root aneurysms, successful aortic surgery can be achieved with careful handling of tissues and resewing of anastomoses with pledgeted sutures (76). Noninvasive vascular imaging is preferred as fatal complications have been associated with invasive imaging in these patients (106). The outcome of pregnancy in women with Ehlers-Danlos syndrome is poor because of rupture of the gravid uterus and vessel rupture at delivery or in the postpartum period. The diagnosis of vascular Ehlers-Danlos syndrome is based on DNA or protein studies identifying a defect in type III collagen, encoded by the COL3A1 gene.

5.1.4 Turner Syndrome
Turner syndrome is defined as complete or partial absence of 1 sex chromosome in a phenotypic female, most commonly 45, X. Short stature and ovarian failure are the most prevalent finding, but women with Turner syndrome have an increased cardiovascular mortality rate from both structural and ischemic heart disease, especially AoD (108,109). Between 10% and 25% of patients with Turner syndrome have a bicuspid aortic valve. Aortic coarctation is present in approximately 8% of patients. Determining aortic dilatation in patients with Turner syndrome is difficult because aortic dilatation is based on body surface area so the aortas of patients with Turner syndrome are expected to be smaller than those of the general population because of the patient's short stature. If one defines aortic dilatation as an ascending-to-descending aortic diameter ratio of greater than 1.5, then 33% of women with Turner syndrome had aortic dilatation (110).

The average age of AoD in Turner syndrome was 31 years, and less than half of the patients survived the event (111). Data indicate a population-based AoD incidence of 36:100 000 Turner syndrome years (1.4% among individuals with Turner syndrome) compared with 6:100 000 in the general Danish population (112). Therefore, the risk of AoD is much lower in patients with Turner syndrome compared with patients with Marfan syndrome or Loeys-Dietz syndrome. The majority of dissections in women with Turner syndrome occur in patients with known risk factors for dissection, such as cardiovascular malformations (bicuspid aortic valve or coarctation of the aorta), systemic hypertension, or both. Therefore, the evidence base regarding the value of screening for aortic disease in women with Turner syndrome is not available. However, there appears to be an increased risk for dissection in these women, suggesting that imaging of the heart, aorta, and pulmonary veins at the time of diagnosis might be valuable (80,113). For patients with no risk factors for AoD (bicuspid aortic valve, coarctation, dilated aorta), re-evaluation of the aorta has been suggested every 5 to 10 years or if clinically indicated (e.g., attempting pregnancy (114) or transition to an adult clinic). Patients with risk factors for AoD should undergo more frequent imaging. Recently, studies have not shown an effect of growth hormone treatment in women with Turner syndrome on either ascending or descending aortic diameter (113). In addition, studies have not found any evidence of left ventricular hypertrophy in patients with Turner syndrome who were treated with growth hormone (115,116).

5.1.5 Other Genetic Syndromes With Increased Risk for Thoracic Aortic Aneurysms and Dissections
A substantial proportion of patients with Ehlers-Danlos syndrome who do not have the vascular form also have aortic root dilatation, but the progression of this dilatation to AoD is rare (76,117). Similarly, patients with congenital contractural arachnodactyly or Beals syndrome due to mutations in FBN2 have had aortic root enlargement without documented progression to dissection (118,119).

There are other genetic syndromes that have multiple reports or documentation of thoracic aortic aneurysms leading to Type A dissections. There are multiple case reports of AoD in patients with autosomal dominant polycystic kidney disease (120,121). Although AoD is a complication of autosomal dominant polycystic kidney disease, it is less common than cerebral aneurysms leading to subarachnoid hemorrhage in this population. There is insufficient information to gauge the value of routine or screening imaging for these patients.

Similar to autosomal dominant polycystic kidney disease, there are multiple reports in the literature of patients with Noonan syndrome who are experiencing AoDs (122–124). The value of imaging or routine monitoring of these patients is unknown. A review of 200 patients with Alagille syndrome also identified thoracic aortic disease in a small subset of these patients (125).

5.1.6 Recommendations for Familial Thoracic Aortic Aneurysms and Dissections
Class I

1 Aortic imaging is recommended for first-degree relatives of patients with thoracic aortic aneurysm and/or dissection to identify those with asymptomatic disease. (126,127) (Level of Evidence: B)

2 If the mutant gene (FBN1, TGFBR1, TGFBR2, COL3A1, ACTA2, MYH11) associated with aortic aneurysm and/or dissection is identified in a patient, first-degree relatives should undergo counseling and testing. Then, only the relatives with the genetic mutation should undergo aortic imaging. (Level of Evidence: C)

Class IIa

1 If one or more first-degree relatives of a patient with known thoracic aortic aneurysm and/or dissection are found to have thoracic aortic dilatation, aneurysm, or dissection, then imaging of second-degree relatives is reasonable. (126) (Level of Evidence: B)

2 Sequencing of the ACTA2 gene is reasonable in patients with a family history of thoracic aortic aneurysms and/or dissections to determine if ACTA2 mutations are responsible for the inherited predisposition. (26,27,77,78,128,129) (Level of Evidence: B)

Class IIb

1 Sequencing of other genes known to cause familial thoracic aortic aneurysms and/or dissection (TGFBR1, TGFBR2, MYH11) may be considered in patients with a family history and clinical features associated with mutations in these genes. (26,27,77,78,128,129) (Level of Evidence: B)

2 If one or more first-degree relatives of a patient with known thoracic aortic aneurysm and/or dissection are found to have thoracic aortic dilatation, aneurysm, or dissection, then referral to a geneticist may be considered. (Level of Evidence: C)

A genetic basis of nonsyndromic familial thoracic aortic aneurysms and dissection has only recently been defined. Familial aggregation studies of patients referred for repair of thoracic aortic aneurysm and dissection that did not have a genetic defect have indicated that between 11% and 19% of these patients have a first-degree relative with thoracic aortic aneurysms and dissection (127,130). Patients with a family history of thoracic aortic aneurysm and dissection present at a younger mean age than do sporadic patients but at a significantly older age than patients with Marfan or Loeys-Dietz syndrome. The disease is primarily inherited in an autosomal dominant manner with decreased penetrance primarily in women and variable expression (131). These mapping studies have firmly established that there is significant genetic heterogeneity for familial thoracic aortic aneurysm and dissection (i.e., many different genes can be mutated and cause the same clinical condition) (27,77,129,132–134). The causative gene has been identified for the following loci: TAAD2 is due to TGFBR2 mutations, the mutant gene at 16p is the MYH11 gene, and the TAAD4 defective gene is ACTA2.

The defective gene at the TAAD2 locus for familial thoracic aortic aneurysms and dissection was identified as TGFBR2, which is the same gene that is mutated in approximately two thirds of patients with Loeys-Dietz syndrome. Genetic testing of unrelated families with familial thoracic aortic aneurysm and dissections demonstrated that TGFBR2 mutations were only present in 1% to 5% of families (26). All 4 families had mutations that affected TGFBR2 arginine 460 of the receptor, suggesting that missense mutation was associated with familial thoracic aortic aneurysm and dissection (i.e., genotype-phenotype correlation). Although the majority of vascular disease in these families involved the ascending aorta, affected family members also had descending aortic disease and aneurysms of other arteries, including cerebral, carotid, and popliteal aneurysms. It is notable that similar to Loeys-Dietz syndrome, AoDs occur in patients with TGFBR2 mutation at diameters less than 5.0 cm, leading to the recommendation that aortic repair be considered at a internal diameter by echocardiography of 4.2 cm or greater (78) (see Section 5.1).

A large French family with thoracic aortic aneurysm and dissection associated with patent ductus arteriosus was used to map the defective gene causing this phenotype to 16p (135). The defective gene at this locus was identified as the smooth muscle cell–specific myosin heavy chain 11 (MYH11), a major protein in the contractile unit in smooth muscle cells (77). Subsequent analysis of DNA from 93 unrelated families with thoracic aortic aneurysm and dissection failed to identify any MYH11 mutations. Sequencing DNA from 3 unrelated families with thoracic aortic aneurysm and dissection associated with patent ductus arteriosus identified MYH11 mutations in 2 of these families (26); the remaining family had a TGFBR2 mutation as the cause of the thoracic aortic aneurysm and dissection and patent ductus arteriosus. Therefore, MYH11 mutations are responsible for familial thoracic aortic aneurysm and dissection associated with patent ductus arteriosus and a rare cause of familial thoracic aortic aneurysm and dissection.

A defective gene at the locus 10q23–24 was identified in a large family with multiple members with thoracic aortic aneurysm and dissection as ACTA2, which encodes the the smooth muscle-specific alpha-actin, a component of the contractile complex and the most abundant protein in vascular smooth muscle cells (27,136). Approximately 15% of families with thoracic aortic aneurysm and dissection have ACTA2 mutations (27). Features identified in some families with ACTA2 mutation included livedo reticularis and iris flocculi, although the prevalence of these features has not been determined. The majority of affected individuals presented with acute Type A or B dissections or Type B dissections, with 16 of 24 deaths occurring due to Type A dissections. Two of 13 individuals experienced Type A dissections with a documented ascending aortic diameter less than 5.0 cm. AoDs occurred in 3 individuals under 20 years of age, and 2 women died of dissections postpartum. Finally, 3 young men had Type B dissection complicated by rupture or aneurysm formation at the ages of 13, 16, and 21 years.

Identification of the underlying genetic mutation leading to familial thoracic aortic aneurysms and dissections provides critical clinical information for the family. First, only family members who harbor mutations need to be routinely imaged for aortic disease. Second, identification of the underlying mutation may lead to different management of the aortic disease, as is the case for TGFBR2 mutations. In addition to providing information to families, identification of genes leading to familial thoracic aortic aneurysms and dissections has emphasized the roles of smooth muscle contractile function in preventing aortic diseases (11). Individuals who undergo genetic testing for thoracic aortic disease should receive genetic counseling prior to the testing to explain the implications for the testing for their medical follow-up and implications for family members.

5.2 Summary.   The genes leading to nonsyndromic forms of aortic aneurysms and dissections are in the early stages of identification. Tables 6 and 7 summarize the current clinical features associated with mutations in these genes and recommendations for when to sequence these genes in families with multiple members with familial thoracic aortic aneurysm and dissection.

Because thoracic aortic disease is typically asymptomatic until a life-threatening event (e.g., AoD) occurs, evaluating other family members can potentially prevent premature deaths. Most syndromes and familial forms of thoracic aortic disease are inherited in an autosomal dominant manner. Therefore, an individual with an inherited predisposition to thoracic aortic aneurysm and dissections has up to a 50% risk of passing on this predisposition to their children, which is the basis for genetic evaluation of the offspring. In addition, siblings and parents of the patient need to be evaluated for possible predisposition to thoracic aortic aneurysm and dissections. Because of the variable age of onset of aortic disease in familial thoracic aortic aneurysms and dissections, the writing committee believes that imaging of family members at risk of the disease every 2 years is warranted.

	6. Other Cardiovascular Conditions Associated With Thoracic Aortic Aneurysm and Dissection

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
6.1 Recommendations for Bicuspid Aortic Valve and Associated Congenital Variants in Adults.   Class I

1 First-degree relatives of patients with a bicuspid aortic valve, premature onset of thoracic aortic disease with minimal risk factors, and/or a familial form of thoracic aortic aneurysm and dissection should be evaluated for the presence of a bicuspid aortic valve and asymptomatic thoracic aortic disease. (Level of Evidence: C)

2 All patients with a bicuspid aortic valve should have both the aortic root and ascending thoracic aorta evaluated for evidence of aortic dilatation. (137–140) (Level of Evidence: B)

Bicuspid aortic valves is the most common congenital abnormality affecting the aortic valve and the aorta and is found in 1% to 2% of the population (137). Nine percent of patients have family members who also have bicuspid aortic valves (141). The ACC/AHA Valvular Heart Disease Guidelines specifically address this condition (5). Of importance to this guideline, bicuspid aortic valves can be inherited in families as an autosomal dominant condition and may be associated with thoracic aortic aneurysm formation. It is important to note that in these families, members can have thoracic aortic aneurysms in the absence of bicuspid aortic valves (142). The valves are prone to either aortic valve regurgitation, most commonly seen in younger patients, or aortic valve stenosis, more common in older patients. Bicuspid aortic valve repair for regurgitation has excellent long-term results, an important consideration in the absence of prosthetic aortic valve alternatives in this young population (99,139,140,143). The most common site of fusion of the leaflets is at the left and right leaflet commissure, and less so at the right noncoronary leaflet commissure. The latter is typically more often associated with aortic valve stenosis. In a study of 2000 patients at the Cleveland Clinic who underwent bicuspid aortic valve surgery, 20% had concurrent ascending aortic aneurysms that required repair (139,140). AoD is also common, and as many as 15% of patients with acute AoD have bicuspid aortic valves (144), a frequency more common than Marfan syndrome. AoD was present in 12.5% of patients with bicuspid valves with an aortic diameter less than 5 cm, reminiscent of patients with Marfan syndrome in whom 15% had AoD at a size less than 5 cm (16,143).

The writing committee discussed the potential need to screen relatives of patients who have undergone aortic valve replacement before age 70, as these younger patients were more likely to have had bicuspid aortic valve as their primary pathology. However, 40% of women and around one third of men over age 70 undergoing aortic valve replacement have bicuspid aortic valve disease (145). The yield from screening relatives of younger patients with bicuspid aortic valve disease compared with relatives of older patients is not known.

6.2 Aberrant Right Subclavian Artery.   Aberrant right subclavian artery, which arises as the fourth branch from the aorta, courses behind the esophagus in approximately 80% of patients and causes dysphagia in many patients (146–149). The dysphagia usually occurs in adults as the artery enlarges (Kommerell diverticulum) (150,151). In most adult patients, the aorta is also abnormal and is prone to aneurysm formation, dissection, and rupture. Surgical treatment in adults involves resection of the aneurysmal segment of the subclavian artery (the diverticulum) and the adjacent aorta and replacement of the aorta with a graft (152). An alternative treatment is exclusion of the right subclavian artery origin and adjacent aorta using an aortic endograft, although long-term follow-up of this endovascular approach is not available and the compression and aneurysm growth may continue (153). The distal normal segment of the subclavian artery is usually not reimplanted into the descending aorta directly but rather revascularized using an interposition graft or carotid-subclavian bypass. Alternatively, the subclavian artery can be ligated or coiled distal to the aneurysm, implanting the distal segment into the adjacent carotid artery in the neck and thus restoring flow to the upper extremity and the ipsilateral vertebral artery (148,149,152).

6.3 Coarctation of the Aorta.   Coarctation of the aorta is a relatively common abnormality that occurs in about 40 to 50 of every 100 000 live births, with a 2:1 ratio in males versus females. Most lesions are treated soon after birth or in childhood, and adults presenting with untreated coarctation of the aorta are rare. More often, patients have had previous procedures and present with later problems such as heart failure, intracranial hemorrhage, hypertension particularly with exercise, aneurysm formation, AoD, rupture of old repairs, undersized grafts of previous repairs, and infections. It is of particular importance in previously treated patients with some aortic narrowing to check for a gradient across the stenosis and for hypertension during exercise testing (154).

Untreated coarctation of the aorta has a dismal prognosis, with 80% of patients dying from complications associated with the coarctation. Approximately one quarter will die from AoD or rupture, one quarter will die from heart failure, one quarter will die from intracranial hemorrhage, and the remainder will die from other complications.

Surgical options, depending on the lesion, include subclavian artery patch aortoplasty, patch aortoplasty, bypass of the coarctation, tube graft replacement, aneurysm replacement, 2-stage combined bicuspid valve surgery, and arch and descending aorta replacement or ascending aorta–to–descending aorta bypass (3). Endovascular balloon dilatation and stent placement has been used successfully and is becoming a less invasive alternative to conventional open surgical procedures (155). Occasionally, the adult aorta may be redundant and kinked opposite the ligamentum arteriosum without any pressure gradient, the so-called pseudocoarctation. Aneurysms that require surgical treatment may develop proximal and distal to the kinked area (156).

6.4 Right Aortic Arch.   A right-sided aortic arch is present in approximately 0.5% of the population and rarely requires surgical repair. However, some patients present with dysphagia or asthma-like symptoms with expiratory wheezing. CT or MR readily diagnoses the problem of either tracheal compression or esophageal compression with the esophagus enlarged and filled with gas above the level of the arch. Felson and Palayew described 2 types (157).

In Type I, the great vessels come off the right-sided arch in a manner that is a mirror image to normal anatomy; however, compression of the esophagus or trachea is caused by an enlarged aorta where it crosses the vertebral bodies or by the vascular ring formed by the atretic ductus arteriosus. In Type II, the aberrant left subclavian artery comes off the descending aorta and typically runs posterior to the trachea and compresses the trachea. As with an aberrant right subclavian artery, the proximal segment of the subclavian artery may enlarge and form a Kommerell diverticulum. Other variations are also seen but are exceedingly rare. A separate trunk may arise from the arch, and from this trunk, the innominate, carotid, and subclavian arteries arise. Another rare finding is a right-sided arch with a stump of left-sided aorta joining the right-sided arch after it crosses into the left chest. The stump of the left-sided aorta gives off a branch to the left subclavian artery. The aorta with right-sided arches is also abnormal and typically very fragile and prone to AoD, rupture, or aneurysm formation. Surgical repair involves resection of the aorta and, if needed, reimplantation or bypass of the aberrant left subclavian artery.

	7. Inflammatory Diseases Associated With Thoracic Aortic Disease

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
7.1 Recommendations for Takayasu Arteritis and Giant Cell Arteritis.   See Table 8.

1 Initial therapy for active Takayasu arteritis and active giant cell arteritis should be corticosteroids at a high dose (prednisone 40 to 60 mg daily at initiation or its equivalent) to reduce the active inflammatory state. (158,159) (Level of Evidence: B)

2 The success of treatment of patients with Takayasu arteritis and giant cell arteritis should be periodically evaluated to determine disease activity by repeated physical examination and either an erythrocyte sedimentation rate or C-reactive protein level. (160,161) (Level of Evidence: B)

3 Elective revascularization of patients with Takayasu arteritis and giant cell arteritis should be delayed until the acute inflammatory state is treated and quiescent. (162) (Level of Evidence: B)

4 The initial evaluation of Takayasu arteritis or giant cell arteritis should include thoracic aorta and branch vessel computed tomographic imaging or magnetic resonance imaging to investigate the possibility of aneurysm or occlusive disease in these vessels. (Level of Evidence: C)

Class IIa

1 It is reasonable to treat patients with Takayasu arteritis receiving corticosteroids with an additional anti-inflammatory agent if there is evidence of progression of vascular disease, recurrence of constitutional symptoms, or re-elevation of inflammatory marker. (158) (Level of Evidence: C)

7.2 Takayasu Arteritis.   Takayasu arteritis, also known as pulseless disease, is an idiopathic vasculitis of the elastic arteries, involving the aorta and its branches. Initially described in Japan, the disease is found worldwide. In the United States, a review of cases in Olmsted County, Minn, reported a rate of 2.6 cases per million persons (158). In the United States, the disease affects all ethnic and racial groups in proportion to the census with a moderate Asian overrepresentation. The disease affects women approximately 10 times more often than men. Most commonly diagnosed in the third decade (i.e., the 20s) of life, the disease has been found in children and adults in the fifth decade (i.e., the 40s). Two specific disease distributions have been reported: Japanese and Indian (167,168).

In the Japanese distribution, the thoracic aorta and great vessels are most commonly affected. In contrast, in the Indian type, the disease most commonly affects the abdominal aorta and the renal arteries (28). The pathogenesis of Takayasu arteritis remains poorly defined. A T-cell–mediated panarteritis, the disease proceeds from adventitial vasa vasorum involvement inward. The antigen for the localized inflammatory process is undefined but likely specific as the T cells undergo clonal expansion. The outcome process of destruction and fibrotic repair depends on the dominant pathophysiologic process: destruction yields aneurysms while fibrosis causes stenosis.

The diagnosis of Takayasu arteritis may be made using the 1990 American College of Rheumatology criteria: 1) age of onset younger than 40 years, 2) intermittent claudication, 3) diminished brachial artery pulse, 4) subclavian artery or aortic bruit, 5) systolic blood pressure variation of greater than 10 mm Hg between arms, and 6) angiographic (CT, MR) evidence of aorta or aortic branch vessel stenosis (163) (Figure 16). When 3 of the criteria are manifest, the sensitivity and specificity for diagnosis are 90.5% and 97.8%, respectively. Laboratory testing may aid in diagnosis. Markers of inflammation, such as C-reactive protein and erythrocyte sedimentation rate, are elevated in approximately 70% of patients in the acute phase and 50% in the chronic phase of disease (158).

View larger version (84K): [in this window] [in a new window] [Download PPT slide]   Figure 16 Takayasu arteritis with involvement of the thoracoabdominal aorta and great vessels as shown on contrast-enhanced CT and MR examinations. Note narrowing of the arterial lumen and circumferential soft tissue thickening of the walls of the great vessels and thoracic and abdominal aorta. Panel A, Image through the great vessels with narrowing of the left common carotid and left subclavian arteries. Panel B, Mid descending thoracic aorta (arrowheads). Panel C, Aorta just above the diaphragm (arrowheads). Panel D, Infrarenal aorta. Panel E, Volume-rendered image from CT demonstrates the extent of involvement. Panel F, Oblique sagittal MR of the thoracic aorta. Panel G, Coronal MR of the abdominal aorta. CT indicates computed tomographic imaging; and MR, magnetic resonance imaging.

The aorta itself may develop either aneurysm or stenosis. In a Japanese series of 116 patients with Takayasu arteritis, nearly 32% of the patients had aortic aneurysm formation (170). Most commonly, aneurysm formation developed in the descending aorta, followed by the abdominal, then ascending aortic segments. In the National Institutes of Health series of 60 patients with Takayasu arteritis, 23% had aortic aneurysm formation (158). Aneurysms most commonly formed in the aortic arch or root, abdomen, and then other thoracic segments. Stenosis of the aorta is more common than is aneurysm formation, occurring in 53% of patients in the National Institutes of Health series. Any segment of the aorta may be involved, but the abdominal aortic segment is affected more than 70% of the time if stenosis is found.

Treatment of Takayasu arteritis begins with inflammation reduction with corticosteroids. Steroids are typically started at high dose, 40 to 60 mg daily at initiation to lower the erythrocyte sedimentation rate or C-reactive protein to normal, and are required for 1 to 2 years to ensure proper disease treatment (169). Despite the prolonged regimen, nearly half of the patients will relapse during tapering, requiring additional immunosuppression. Second-line agents that have been used include methotrexate, azathioprine, and antitumor necrosis factor-alpha agents (158,169). Unfortunately, markers of inflammation are imperfect barometers of disease activity. Disease progression has been shown to occur in the setting of normal marker levels (158).

Revascularization for aortic stenosis or aneurysm occurs for the same indications as in noninflammatory disorders: secondary organ vascular insufficiency or risk of rupture. There are no randomized trials of percutaneous or surgical intervention in this disease (158,171–173). Nonrandomized reports have shown that revascularization of either variety may be appropriate, with one caveat. The risk of graft failure is higher in patients with active local inflammation (162). Moreover, the presence of aneurysmal disease itself may be problematic. One report documented a 12% incidence of anastomotic aneurysms over 2 decades of follow-up related to the presence of aneurysms at surgery (174).

7.3 Giant Cell Arteritis.   GCA, also known as temporal arteritis, is an elastic vessel vasculitis involving the aorta and its secondary and tertiary branches. Distinguishing it from Takayasu arteritis, GCA affects patients above the age of 50 years, with an incidence peaking in the eighth decade of life (175). The disease affects women in a 3:2 ratio to men and has a predilection for those of northern European ancestry (29). In the United States, epidemiologic investigation reports a prevalence of 20 cases per 100 000 persons. The incidence is higher in Scandinavian nations but lower in southern Europe, suggesting a genetic predisposition in certain populations (176).

The clinical presentation of GCA is varied, requiring a heightened suspicion by clinicians for early diagnosis. Half of the patients report constitutional symptoms, such as weight loss, night sweats, malaise, and fever (177). Because of the predilection for secondary and tertiary thoracic branches of the aorta, cranial symptoms are common. Scalp tenderness and headache are present in two thirds of patients and in up to 90% of patients with biopsy-proved disease (177). Jaw claudication is common and affects half of the patients, 20% develop visual changes, and other neurologic symptoms such as stroke or neuropathy occur in nearly one third (29). Visual changes are particularly important to notice, because early treatment may prevent permanent blindness. Patients may report diplopia, amaurosis fugax, or blurriness prior to blindness. Polymyalgia rheumatica characterized by a generalized inflammatory state with proximal muscle involvement is found in nearly half of patients with GCA (29). Patients with polymyalgia rheumatica report muscular pain and stiffness, particularly on initiation of movement.

Extracranial vascular involvement is less common in GCA than in Takayasu arteritis, occurring in 25% of patients. In a 50-year study of Olmsted County, Minn, that included 168 patients with GCA, aortic aneurysm/dissection was found in 18% of the subjects, whereas large-artery stenosis was noted in 13% of patients (178). No patient had stenosis of the aorta. Aortic aneurysm formation represents an important marker. Although aneurysm formation per se does not reduce survival compared with the GCA cohort as a whole, AoD in the setting of an aneurysm reduces survival to an average of 1.1 years (178). Similarly, aortic aneurysm rupture or dissection caused two thirds of deaths in a series of patients with GCA in California (179).

The American College of Rheumatology diagnostic criteria for GCA include 1) age older than 50 years, 2) recent-onset localized headache, 3) temporal artery pulse attenuation or tenderness, 4) erythrocyte sedimentation rate greater than 50 mm/h, and 5) an arterial biopsy demonstrating necrotizing vasculitis (164). Three or more criteria confer a sensitivity and specificity above 90% for the disease. With intracranial disease, temporal artery biopsies are diagnostic in up to 80% of cases (180). The rate of positivity declines with initiation of glucocorticoid therapy, but this should not delay treatment to avoid GCA complications. Biopsies performed within 7 days of steroid initiation retain a high diagnostic yield (181).

The pathophysiology of GCA shares important features with Takayasu arteritis (28). GCA is marked by a T-cell clonal expansion suggesting a specific antigenic response, which currently remains unelucidated. The inflammatory response, which begins in the adventitial layer, is marked by augmented cytokine and MMP production causing granuloma formation. Granuloma formation both shields the vessel from the inciting antigen and causes vessel destruction. The inflammatory environment within the vessel wall with the possible formation of aneurysms or vessel stenosis is histologically identical to that of Takayasu arteritis. Because of the multiyear cyclical nature of disease incidence, some have posited an infectious etiology (29).

Corticosteroids represent the standard in therapy for patients with GCA (182). The typical treatment regimen includes starting prednisone dose of 40 to 60 mg daily, although recent evidence suggests a similar efficacy with 30 to 40 mg daily (183). Therapy is typically required for 1 to 2 years to avoid recurrence, although the dose may be tapered beginning 2 to 3 months after initiation. Patients commonly report feeling much better rapidly but, as with Takayasu arteritis, new vascular involvement may occur in up to half of patients treated with steroids (184). In contrast to Takayasu arteritis, additional immunomodulatory agents do not seem to modulate the disease's progress. Methotrexate studied in a double-blind, placebo-controlled study as an adjunct to prednisone did not reduce morbidity, erythrocyte sedimentation rate level, or cumulative prednisone dose (184a). Revascularization recommendations follow the same pattern as in Takayasu arteritis.

7.4 Behçet Disease.   In 1937, Hulusi Behçet described his eponymous syndrome based on a set of 3 symptoms: uveitis, aphthous stomatitis, and genital ulcers. Most common in Turkey, with a prevalence of 80 to 370 cases per 100 000 persons (185,186), the disease is much less common in the United States, with an estimated prevalence of 1 to 3 cases per million persons (187). The diagnostic criteria were established by the International Group for Behçet's disease and require oral ulceration and 2 of these 3 lesions: recurrent genital ulceration, uveitis or retinal vasculitis, or skin lesions, such as erythema nodosum, pseudofolliculitis, or pathergy (188). In addition to these cardinal manifestations, vascular involvement may occur in one third of patients. A small vessel vasculitis commonly associated with the human leukocyte antigen (HLA) B51 allele (187), Behçet disease is 1 of 2 vasculitides that may also involve veins. Venous involvement is most commonly superficial thrombophlebitis, but deep vein thrombosis in the vena cava, varices, and cerebral sinuses has been reported (189). The small vessel involvement of Behçet disease may result in nonvascular complaints, such as erythema nodosum, arthritis, and gastrointestinal involvement with diarrhea, gastrointestinal bleeding, or perforation (187). Treatment of Behçet disease varies based on the manifestation of disease. Systemic corticosteroids are the typical therapy for those with vascular involvement.

Specifically with regard to vascular manifestations of Behçet disease, any artery or vein, large or small, systemic or pulmonary, may be involved by the vasculitic process. Aortic histopathology shows lymphocytic infiltration mixed with histiocytes and eosinophils with giant cells around vasa vasorum of media and adventitia. Destruction of media leads to aneurysm formation and may proceed to pseudoaneurysm formation and rupture. Aneurysm formation may occur in multiple sites and in different sites over a period of follow-up. Aneurysm, stenotic lesions, and occlusion of brachiocephalic arteries may occur with or without aortic involvement. Although aortic involvement is unusual for patients with Behçet vasculitis, aneurysm rupture can be unpredictable and fatal (190,191). With regard to surgical repair, anastomotic pseudoaneurysms often occur (12.9% within 18 months in 1 series) and may be related to ongoing inflammatory changes in the area of anastomotic suture lines (192). Endovascular repair with stent grafts has also been described (193).

7.5 Ankylosing Spondylitis (Spondyloarthropathies).   The group of diseases labeled spondyloarthropathies are linked by the strong association of major histocompatibility complex HLA B-27 and the absence of rheumatoid factor (194,195). Several features are common to the spondyloarthropathies, including sacroilitis, inflammatory arthritis or enthesitis (inflammation of tendon insertions), associations with inflammatory bowel disease or psoriasis, and aortitis and heart block (195).

Ankylosing spondylits is the most common variant and often begins with back pain and stiffness in the second or third decade of life. It affects men 2 to 3 times as often as women, worsens with inactivity, and commonly takes years for the diagnosis to be made (196). The diagnosis requires 4 of the 5 criteria: onset of pain at younger than 40 years, back pain for longer than 3 months, morning stiffness, subtle symptom onset, and improvement with exercise (197). Patients may also report constitutional symptoms, such as malaise or fever. Acute anterior uveitis is reported in up to 40% of patients. Aortic root and aortic valve involvement are reported in up to 80% of patients (198). When involved, the aortic valve may have a nodular appearance, and aortic valvular regurgitation is present in nearly half of the patients (198). Treatment of aortic root expansion and aortic valvular abnormalities is the same as for other conditions.

7.6 Infective Thoracic Aortic Aneurysms.   Infection (due to bacterial, fungal, viral, spirochetal, or tubercular organisms) is a rare cause of thoracic aortic aneurysms. Originally named mycotic endarteritis by Osler (199), the terms infected aneurysm or infectious aortitis are now used more commonly, because the majority of etiologic agents are nonfungal. Saccular aneurysms are most common, but infected aneurysms can be fusiform and often even pseudoaneurysms. The ascending thoracic aorta, aortic arch, and descending thoracic aorta can all be affected, as can prosthetic aortic grafts and aortic homografts. Typically, the sites of infected aneurysms are opposite the great vessels in the aortic arch or opposite the visceral ateries in the abdomen. There are several mechanisms by which the aortic infection may arise. First, there may be contiguous spread from adjacent thoracic structures, such a mediastinitis, abscess, infected lymph nodes, infectious pericarditis, empyema, or paravertebral abscess. Second, there may be septic emboli from underlying bacterial endocarditis. Third, there may be hematogenous dissemination of bacteria in the setting of sepsis or intravenous drug abuse. Infection most often arises in a diseased aorta, either in a preexisting aneurysm, at the site of an atherosclerotic plaque, or at the site of some accidental or iatrogenic aortic trauma. Indeed, infected thoracic aortic aneurysms may arise as a late complication of cardiac surgery, often associated with postoperative mediastinitis, typically at the sites of aortic cannulation or anastomotic suture lines (200,201).

Various organisms can infect the aorta, with most infections being bacterial. Staphylococcus aureus and Salmonella are the organisms most commonly identified (202–204). Pneumococcus and Escherichia coli are relatively common gram-positive and gram-negative pathogens, respectively.

Treponema pallidum, the gram-negative spirochete bacterium that causes syphilis, as well as other Treponema species, can cause infected aortitis, with the ascending thoracic aorta most often involved. However, in syphilitic aortitis, thoracic aortic aneurysm does not appear for 10 to 25 years after the initial spirochetal infection. Fungal infections of the aorta, with either Candida or Aspergillus, occur less often (205) and typically occur in the setting of impaired immunity, such as patients with systemic illness, human immunodeficiency virus, or prior organ or bone marrow transplant.

Indeed, patients with impaired immunity are also at increased risk of tuberculous aortitis attributable to mycobacterium tuberculosis. Tuberculous aortitis has until now been exceedingly rare, but the incidence may rise as the prevalence of tuberculosis rises worldwide. Tuberculous aortitis typically affects the distal aortic arch and descending thoracic aorta, likely because the aorta is thought to become infected via direct extension from continuous infected lymph nodes, empyema, or pericarditis (206).

Finally, there appears to be an independent association between human immunodeficiency virus and ascending thoracic aortic dilatation, although its mechanisms are poorly understood (207,208). Moreover, the incidence of frank aneurysms remains extremely low.

	8. Acute Aortic Syndromes

Top ACCF/AHA Task Force Members Table of Contents Preamble 1. Introduction 2. The Thoracic Aorta 3. Thoracic Aortic... 4. Imaging Modalities 5. Genetic Syndromes Associated... 6. Other Cardiovascular... 7. Inflammatory Diseases... 8. Acute Aortic Syndromes 9. Thoracic Aortic Aneurysms 10. Special Considerations in... 11. Aortic Arch and... 12. Porcelain Aorta 13. Tumors of the... 14. Perioperative Care for... 15. Nursing Care and... 16. Long-Term Issues 17. Institutional/Hospital... 18. Future Research Directions... Staff References

 
Acute aortic syndromes consist of 3 interrelated conditions with similar clinical characteristics and include AoD, IMH, and PAU (209).

8.1 Aortic Dissection.   8.1.1 Aortic Dissection Definition
AoD is defined as disruption of the media layer of the aorta with bleeding within and along the wall of the aorta resulting in separation of the layers of the aorta. In the majority of patients (90%), an intimal disruption is present that results in tracking of the blood in a dissection plane within the media. This may rupture through the adventitia or back through the intima into the aortic lumen (Figure 17). This classic dissection results in a septum, or "flap," between the 2 lumens (Figure 18). The false lumen may thrombose over time (Figure 19). While on noninvasive imaging, 15% of patients with aortic dissection syndromes have an apparent IMH without evidence of an intimal tear, autopsy studies show only 4% have no visible intimal tear; indeed, at the time of surgery a tear is found in most patients (210,211). Occasionally, AoD originates from a small atheromatous ulcer that is difficult to identify. On the other hand, extensive atheromatous disease of the aorta may lead to PAU or a localized IMH.

View larger version (79K): [in this window] [in a new window] [Download PPT slide]   Figure 17 Classes of intimal tears. I. Classic dissection with intimal tear and double lumen separated by septum. Communication between lumens is typically in descending aorta at sheared-off intercostal arteries or distal reentry site. II. IMH. No intimal tear or septum is imaged but is usually found at surgery or autopsy. DeBakey Types II and IIIa are common extent of this lesion. III. Intimal tear without medial hematoma (limited dissection) and eccentric aortic wall bulge. Rare and difficult to detect by TEE or CT. Patients with Marfan syndrome prone to this type. May result in aortic rupture or extravasation. IV. PAU usually to the adventitia with localized hematoma or saccular aneurysm. May propagate to Class I dissection, particularly when involving ascending aorta or aortic arch. V. Iatrogenic (catheter angiography or intervention)/traumatic (deceleration) dissection. CT indicates computed tomographic imaging; IMH, intramural hematoma; PAU, penetrating atherosclerotic ulcer; and TEE, transesophageal echocardiography. Figure reprinted with permission from the Cleveland Clinic Foundation. Legend adapted from Svensson et al (212), Chirillo et al (213), and Murray et al (214).

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 18 Type A aortic dissection and extent of involvement depicted on axial CT images from the cranial to caudal direction. Although the flap appears to disappear in the infrarenal, it is actually compressed against the anterior wall of the aorta in Panel G (arrowheads) and it is clearly present caudally in the common iliac arteries in Panel H. Hemopericardium (asterisk) is visible in Panel D. Bowel wall thickening (arrowheads) indicates ischemia in Panel I. Panel A, Aortic arch. Panel B, Mid thorax. Panel C, Aortic root. Panel D, Just above the diaphgram. Panel E, At the level of the celiac axis. Panel F, Mid kidneys. Panel G, Infrarenal aorta. Panel H, Proximal common iliac arteries. Panel I, Image through the mid abdomen at narrow window/level settings demonstrates small bowel wall thickening due to bowel ischemia caused by apposition of the flap against the origins of the celiac axis and superior and inferior mesenteric arteries. CT indicates computed tomographic imaging; F, false lumen; and T, true lumen.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 19 Type A Aortic dissection with thrombosed false lumen and left renal artery involvement depicted on axial CT images. Demonstrates marked narrowing of the true lumen, patent right renal artery arising from the true lumen (bottom left, arrow), and narrow left renal artery compressed by thrombus in the false lumen, with secondary decreased enhancement of the left kidney compared with the right kidney. Top left, At the level of the left main coronary artery. Top right, At the celiac axis. Bottom left, At the right renal artery (arrow). Bottom right, At the left renal artery (arrow). *Thrombus in false lumen. CT indicates computed tomographic imaging; L, left kidney; and R, right kidney.

Regarding time from onset of initial symptoms to time of presentation, acute dissection is defined as occurring within 2 weeks of onset of pain; subacute, between 2 and 6 weeks from onset of pain; and chronic, more than 6 weeks from onset of pain.

8.1.2 Anatomic Classification of Aortic Dissection
Anatomically, acute thoracic AoD can be classified according to either the origin of the intimal tear or whether the dissection involves the ascending aorta (regardless of the site of origin). Accurate classification is important as it drives decisions regarding surgical versus nonsurgical management. The 2 most commonly used classification schemes are the DeBakey and the Stanford systems (Figure 20). For purposes of classification, the ascending aorta refers to the aorta proximal to the brachiocephalic artery, and the descending aorta refers to the aorta distal to the left subclavian artery.

View larger version (55K): [in this window] [in a new window] [Download PPT slide]   Figure 20 Aortic dissection classification: DeBakey and Stanford Classifications. Reprinted with permission from the Cleveland Clinic Foundation.

• Type I: Dissection originates in the ascending aorta and propagates distally to include at least the aortic arch and typically the descending aorta (surgery usually recommended).

• Type II: Dissection originates in and is confined to the ascending aorta (surgery usually recommended).

• Type III: Dissection originates in the descending aorta and propagates most often distally (nonsurgical treatment usually recommended).

– Type IIIa: Limited to the descending thoracic aorta.

– Type IIIb: Extending below the diaphragm.

The Stanford classification system divides dissections into 2 categories, those that involve the ascending aorta and those that do not.

• Type A: All dissections involving the ascending aorta regardless of the site of origin (surgery usually recommended) (Figures 18 and 20).

• Type B: All dissections that do not involve the ascending aorta (nonsurgical treatment usually recommended). Note involvement of the aortic arch without involvement of the ascending aorta in the Stanford classification is labeled as Type B (Figure 21).

View larger version (67K): [in this window] [in a new window] [Download PPT slide]   Figure 21 Type B aortic dissection with mediastinal hematoma and pleural blood. Ruptured Type B aortic dissection with mediastinal hematoma (*) and pleural blood. Left, Flap arises in the proximal descending thoracic aorta, with faint contrast-enhanced blood adjacent to the site of rupture outside the confines of the aortic wall (arrow). Right, At the level of the aortopulmonary window. FL indicates false lumen; PL, pleural blood; and TL, true lumen.

The intimal tear and AoD can also be categorized into classes that may have a bearing on treatment (212,213) (Figure 17).

8.1.3 Risk Factors for Aortic Dissection
Risk factors for AoD include conditions that result in aortic medial degeneration or place extreme stress on the aortic wall (Table 9). Two thirds to three quarters of patients have hypertension, which is often uncontrolled. Genetic predisposition (see Section 5) to AoD can occur in the context of a syndrome, such as Marfan syndrome or Loeys-Dietz syndrome, or can be inherited in families in the absence of syndromic features (3). IRAD data showed that of patients under 40 years of age with AoD, 50% had a history of Marfan syndrome (223). Other congenital or genetically based diseases as well as inflammatory conditions associated with a higher risk of AoD are noted in Sections 6.3, 6.4, and 7.

The history may reveal syndromic causes of thoracic aortic aneurysm and dissections, especially Marfan, Loeys-Dietz, and vascular Ehlers-Danlos syndromes. In some cases, patients have only some of the features of Marfan or Loeys-Dietz syndrome, rather than the full-blown clinical syndrome, so a history of any phenotypic features, such as mitral valve prolapse or pectus excavatum, should prompt consideration of thoracic aortic aneurysms or dissections (224,225). Bicuspid aortic valve is a strong risk factor for ascending thoracic aortic aneurysms, as well as coarctation of the aorta. In addition, a history of extreme exertion or emotional distress may preceed the onset of pain (226).

8.1.4 Clinical Presentation of Acute Thoracic Aortic Dissection
The clinical presentation of acute AoD spans a spectrum from the overt with classic pain and physical examination findings to the enigmatic as a painless process with few physical manifestations of the disease (Table 10). Given its exceedingly high mortality, clinicians must maintain a high index of suspicion for acute AoD, as noted in Section 8.6 (Figure 22).

View larger version (33K): [in this window] [in a new window] [Download PPT slide]   Figure 22 Acute surgical management pathway for AoD. *Addition of ‘if appropriate' based on Patel et al. (226a) AoD indicates aortic dissection; CABG, coronary artery bypass graft surgery; CAD, coronary artery disease; TAD, thoracic aortic disease; and TEE, transesophageal echocardiogram.

Pain location and other associated symptoms reflect the site of initial intimal disruption and may change as the dissection extends along the aorta or involves other arteries or organ systems (236). Data from 464 patients enrolled in IRAD found that patients with Type A dissections most frequently present with chest pain (80%), more commonly described as anterior (71%) than as posterior (32%) (228). Although less common, patients with Type A dissection report back pain (47%) and abdominal pain (21%), presumably as a result of antegrade dissection into the descending aorta (228). In contrast, patients with Type B dissections are most likely to present with back pain (64%) followed by chest and abdominal pain (63% and 43%, respectively) (228). Some patients present with abdominal pain in the absence of chest pain or with only painful or numb lower extremities related to end-organ ischemia. In 1 retrospective study of 44 patients ultimately diagnosed with acute thoracic AoD, the location of the patient's pain was highly predictive of the clinician's suspicion for acute AoD; dissection was suspected in 86% of patients who presented with chest and back pain, 45% of those who presented with chest pain alone, and only 8% of those primarily abdominal pain (237).

Although uncommon, acute AoD may present without pain (238–240). In a separate analysis of 977 IRAD patients, 63 patients (6.4%) presented without pain (241,242). This group of patients was noted to be older and more likely to present with syncope, stroke, or congestive heart failure than were patients with painful dissection (241). Patients on steroids and patients with Marfan syndrome may be more prone to present without pain (243).

8.1.4.2 Perfusion Deficits and End-Organ Ischemia
Perfusion deficits as a result of dissection-related obstruction of aortic branch vessels have long been recognized as a common clinical manifestation, resulting in organ complications at initial presentation (Table 11). End-organ involvement in acute thoracic AoD can occur via several mechanisms. Most occlusions are caused by obstruction by the dissection flap, which can either prolapse across a vessel origin without entering it (dynamic obstruction) or directly extend into a vessel (static obstruction) (244) (Figure 18). Other causes include postobstructive arterial thrombosis, embolism to branches of either the true or false lumen, direct compression of an aortic branch artery or adjacent structures by an expanding false lumen (245), rupture or leakage of the false lumen into contiguous structures, and occlusion or dissection of coronary arteries and/or aortic valve distortion leading to heart failure.

Combined data from over 1500 patients in 16 studies found that pulse deficits were present in 31% of cases (95% CI 24% to 39%) and, when present, were strongly suggestive of AoD (positive likelihood ratio 5.7; 95% CI 1.4 to 23) (37) and predict increased risk. Of 513 cases of Type A dissection, patients with perfusion deficits were more likely to present with hypotension, shock, neurologic deficits, and tamponade and were more likely to have higher rates of hospital complications and mortality (41% versus 25%, P=0.0002) (246). Furthermore, overall mortality rates correlated with the number of pulse deficits present, likely as a reflection of the extent of vascular compromise and associated end-organ ischemia (246). Similarly, of 118 patients with Type A acute dissection, limb ischemia (defined as loss of pulse with associated pain and neurologic symptoms) was present in 38 cases (32%) (247). The presence of limb ischemia was associated with an increased likelihood of other end-organ ischemia (i.e., cerebral, visceral, or coronary) and a significant increase in overall mortality (247). Among the 38 patients with limb ischemia, in-hospital mortality was 45% compared with 15% among the 61 patients without organ malperfusion (247).

These studies underscore the clinical importance of an adequate vascular examination to help both identify the disease and stratify risk once the diagnosis is established. Every patient being evaluated for possible acute AoD should have pulses checked in all extremities to identify the presence of perfusion deficits. In patients with acute limb ischemia versus those without, renal and mesenteric malperfusion were nearly 2-fold more frequent and mortality was twice as high, further highlighting the importance of this finding (248).

8.1.5 Cardiac Complications
The heart is the most frequently involved end organ in acute AoD involving the ascending aorta. In distinction to other end-organ pathology, most cardiac complications are a direct result of dissection-related disruption of normal anatomic relationships (215,245).

8.1.5.1 Acute Aortic Regurgitation
Acute aortic regurgitation is the most commonly recognized cardiac complication of Type A dissection (228–234), occurring in 41% to 76% of cases (228–232). Three distinct dissection-related mechanisms for acute aortic valve incompetence have been identified, and they can occur in combination: 1) acute dilatation of the aortic root by an expanding false lumen, resulting in incomplete aortic valve closure; 2) a dissection extending into the aortic root and disrupting aortic valve commissural attachments, resulting in valve leaflet prolapse; and 3) a portion of dissection flap prolaping through the aortic valve in diastole, preventing adequate leaflet closure (235). Clinical manifestations of dissection-related aortic regurgitation span the spectrum from only a hemodynamically insignificant diastolic murmur to congestive heart failure and cardiogenic shock (236,249).

8.1.5.2 Myocardial Ischemia or Infarction
Myocardial ischemia or infarction is an infrequent but serious complication of acute AoD. Registry and review data suggest that ECG evidence of myocardial ischemia was present in up to 19% of patients with acute AoD, whereas pooled data from 988 patients in 9 different studies found that acute MI was present in 7% of cases (95% CI 4% to 14%) (37,47,250). Coronary artery flow can be compromised by an expanding false lumen compressing the proximal coronary or by extension of the dissection flap into the coronary artery ostium (251).

Clinically, a dissection-related cardiac malperfusion syndrome may present with ECG changes that are indistinguishable from those of primary myocardial ischemia or infarction, increasing the likelihood of misdiagnosis and inappropriate therapeutic intervention (252).

8.1.5.3 Heart Failure and Shock
Heart failure is a relatively uncommon complication of AoD, found to occur in approximately 6% of cases (236). In this setting, heart failure may result from acute aortic insufficiency, acute myocardial ischemia or infarction, or cardiac tamponade. Registry data suggest that patients with acute AoD complicated by heart failure are often atypical in their presentation, frequently leading to a delay in diagnosis (236). The largest study to evaluate heart failure in acute AoD included 1069 patients from the IRAD database and found that patients with AoD and concomitant heart failure were more likely to present in shock but were less likely to complain of chest pain and that, when chest pain was present, the pain was more often mild and less often abrupt in onset (236).

8.1.5.4 Pericardial Effusion and Tamponade
Pericardial pathology is a frequent complication of acute Type A AoD and can occur via 2 distinct mechanisms (37,253–256). Most commonly, transudation of fluid across the thin wall of an adjacent false lumen into the pericardial space leads to a hemodynamically insignificant pericardial effusion (256), which is present in about one third of patients (257). Less often, the dissected aorta ruptures directly into the pericardium, leading rapidly to tamponade physiology and hemodynamic compromise (245,258,259). Cardiac tamponade is diagnosed in 8% to 10% of patients presenting with acute Type A AoD and is an ominous clinical predictor of poor outcomes (260), as well as the leading cause of mortality in this group (47,215,231). Consequently, the presence of cardiac tamponade should prompt truly urgent aortic repair (260).

8.1.6 Syncope
Syncope is a well-recognized dissection-related complaint occurring in approximately 13% of cases (242,261) with multiple potential etiologies, including: 1) cardiac (e.g., severe aortic regurgitation, ventricular outflow obstruction, cardiac tamponade), 2) vascular (e.g., impaired cerebral blood flow and aortic baroreceptor activation); 3) neurologic (e.g., vasovagal in response to pain), and 4) volume-related (e.g., false lumen rupture into the pleural space) causes (240,261–267). Regardless of its etiology, syncope in the setting of AoD increases the risk of near-term adverse events. In a review of 728 cases of acute AoD, patients with a history of syncope were significantly more likely to die than were those without syncope (34% versus 23%, respectively; P=0.01) (242). Additionally, patients who presented with syncope more frequently had associated cardiac tamponade, stroke, decreased consciousness, and evidence of spinal cord ischemia (242).

8.1.7 Neurologic Complications
Acute AoD frequently presents with dissection-related neurologic complications. Pooled data from more than 1300 patients in 13 studies that included both Type A and B dissections found that neurologic symptoms were reported in 17% (37). Neurologic complications may result from hypotension, malperfusion, distal thromboembolism, or nerve compression (251,253,254). In a recent study of 102 patients with Type A AoD, 29% had neurologic symptoms on initial presentation (253); of those with neurologic symptoms, 53% had ischemic stroke (predominantly right hemispheric) and 37% had ischemic neuropathy (described as limb pain with sensory or motor deficit) (253).

Last, although uncommon, acute paraplegia as a result of spinal cord malperfusion has been described as a primary manifestation of thoracic AoD, occurring in 1% to 3% of patients (215,251,253,254,268,269).

Of clinical note, up to 50% of dissection-related neurologic symptoms may be transient and as many as one-third of patients with neurologic symptoms present without complaints of chest pain, complicating appropriate diagnosis and treatment (253,255,256,262,269–271).

8.1.8 Pulmonary Complications
Pleural effusion, the most common pulmonary complication of acute AoD, is noted in 16% of cases at presentation (37); whereas large effusions may result from leaking of blood from the aorta into the pleural space, small effusions are typically a nonhemorrhagic exudate believed to be inflammatory in origin (37,272–275).

Other pulmonary complications of acute AoD include dissection-related compression of the pulmonary artery and development of an aortopulmonary fistula, either of which may present with dyspnea as a prominent symptom (276–278). Hemoptysis, noted in 1 study in 3% of patients presenting with thoracic AoD, may result from compression of lung parenchyma by an expanding false lumen or via direct aneurysmal rupture into the lung, leading to massive hemoptysis and death (215,279,280).

8.1.9 Gastrointestinal Complications
Mesenteric ischemia is the most common gastrointestinal complication of acute AoD (228) and can result from malperfusion or systemic hypotension. It is the most common cause of death among those with Type B AoD. Mesenteric ischemia is associated with abdominal pain, but pain may be nonspecific and out of proportion to the physical examination of the abdomen, so the cause of pain often goes unrecognized early on. Unfortunately, by the time serum markers of bowel ischemia or infarction turn positive, it is often too late to salvage the bowel or the patient. Therefore, it is essential to be viligant for mesenteric ischemia in every patient with acute AoD and associated abdominal pain.

Gastrointestinal hemorrhage is a rare but potentially catastrophic complication of acute AoD (281–283). Dissection-related gastrointestinal bleeding may present with limited bleeding as a result of mesenteric infarction or as massive hemorrhage secondary to an aortoesophageal fistula or false lumen rupture into proximal small bowel (281–283). Although rare, dissection-related gastrointestinal hemorrhage should be in the differential of all patients presenting with bleeding and complaints of thoracic or abdominal pain.

8.1.10 Blood Pressure and Heart Rate Considerations
Blood pressure abnormalities are common in patients presenting with acute thoracic AoD. About half of patients are hypertensive at presentation, with 71% of Type B patients having a systolic blood pressure greater than 150 mm Hg versus only 36% of Type A patients (284–287). Conversely, nearly 20% present with either hypotension or shock (37). Hypotension and shock can result from cardiac tamponade, aortic hemorrhage, severe aortic insufficiency, myocardial ischemia or infarction, true lumen compression by distended false lumen, or an intra-abdominal catastrophe. Of more than 1000 patients with acute AoD, those with hypotension on admission were found more likely to have neurologic complications; myocardial, mesenteric, or limb ischemia; and death (249).

Accurate systemic blood pressure measurement may be complicated by dissection-related occlusion of aortic branch arteries, resulting in erroneously low blood pressure readings in the affected limb. Accordingly, blood pressures may need to be measured in both arms and, at times, both legs to determine the highest central blood pressure.

8.1.11 Age and Sex Considerations
Acute AoD presentation varies with patient age and sex. In 951 IRAD patients, 7% were younger than 40 years. Compared with patients 40 years of age and older, this group was less likely to have a history of hypertension and significantly more likely to have Marfan syndrome, bicuspid aortic valve, or a history of prior aortic surgery (223). Clinically, young patients in this study were more likely to describe pain as abrupt in onset but less likely to be hypertensive at presentation (25% versus 45%) (223). In contrast, a separate study of IRAD data evaluating 550 patients with Type A dissection found that among patients more than 70 years of age (32% of total), typical symptoms (abrupt onset of pain) and signs (murmur of aortic regurgitation or pulse deficits) were significantly less common, suggesting that extra vigilance may be required to identify acute AoD in young and elderly patients (288).

Sex appears to affect the presentation of acute AoD as well. In a study of 1078 patients enrolled in IRAD, 32% were women. Women were older; were less likely to present within 6 hours of symptom onset, to complain of abrupt onset of pain, and to have a pulse deficit; and were more likely to present with either altered mental status or congestive heart failure. Consequently, women were less likely to be diagnosed within 24 hours of symptom onset and had significantly higher in-hospital mortality (30% versus 21%, P=0.001) than men (289).

8.2 Intramural Hematoma.   Among acute aortic syndromes, acute dissection is the most common, but approximately 10% to 20% of patients (290–292) with a clinical picture of dissection exhibit an IMH via imaging without identification of blood flow in a false lumen or an intimal lesion. Some believe IMH arises from hemorrhage of the vasa vasorum located within the medial layer of the aorta (293,294), whereas others argue that the hematoma arises from microscopic tears in the aortic intima. The resulting hematoma may then propagate in an antegrade or a retrograde manner, producing symptoms that may be impossible to differentiate clinically from those of a classic AoD (61). IMH has a variable radiologic appearance (Figure 23) according to the area of the aorta involved. In some cases, IMH may be associated with a PAU (see Section 8.2 or 8.3).

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 23 Intramural hematoma demonstrated as a low-attenuation band of hematoma (arrows) in the aortic wall on CT images. Top left, Axial image at the level of the aortic arch. Top middle, Through the mid thorax. Top right, At the level of the superior mesenteric artery with narrowing of the aortic lumen. Bottom left, Oblique sagittal reformatted image through the thorax (note band artifact evident without the use of ECG gating). Bottom right, Coronal reformatted image through the abdomen demonstrate the length of the hematoma, and an incidental infarenal aortic aneurysm. CT indicates computed tomographic imaging; and ECG, electrocardiogram.

Imaging criteria of IMH are based on the appearance of fresh thrombus in the aortic wall. These include crescentic or circular thickening of the aortic wall with maximal thickness greater than or equal to 7 mm on TEE without intimal flap or tear or longitudinal flow in the false lumen. The thickened wall has a higher tissue density than unenhanced blood on CT and is without enhancement after contrast on the CT/MR (290,296–298). When the term IMH is used strictly, no intimal defect such as a tear or an ulcer is present. But in practice, the term is used loosely to mean a thrombosed false lumen regardless of a small intimal defect. The distinction is further blurred by the facts that the intimal defect may be subtle and difficult to exclude and that some patients with IMH begin with a CT scan that shows a thrombosed false lumen with no apparent intimal defect and then over the course of 1 or 2 months develop 1 or more distinct ulcerlike communications (299,300). Because of this overlap in imaging findings, it is difficult and perhaps somewhat arbitrary to base treatment on the appearance of the CT snapshot of the aorta in its disease progression.

The natural history of IMH is variable. The hematoma may entirely resolve (10%) (301), it may convert to a classic dissection, or the aorta may enlarge and potentially rupture. The clinical behavior of IMH varies according to the location and mimics that of classic AoD. IMH involving the ascending aorta has a high, early risk of complication and death with medical treatment alone, and surgery is usually indicated. IMH involving the descending aorta may be treated with blood pressure control, and the use of beta blockers has been shown to improve the long-term survival rate (296). Conversion of the IMH to a more classic picture of dissection occurs in 3% to 14% of cases involving the descending aorta (297,298,302,303) and in 11% to 88% of cases involving the ascending aorta (302–305), with that figure increasing with increased length of follow-up. Progressive increase in aortic diameter has been demonstrated by serial imaging studies (298,306). In 1 study, the mortality after 2 years of patients with acute proximal Type A IMH versus that of patients with classic dissection was not significantly different (307). Another group found improved actuarial survival rates at 1, 2, and 5 years in patients with IMH versus classic dissection: 90%, 90%, and 90% versus 67%, 66%, and 62%, respectively, for Type A (304), and 100%, 97%, and 97% versus 83%, 79%, and 79%, respectively, for Type B (297). Song et al also described increased risk for complications or mortality for patients with IMH involving the ascending aorta when ascending aortic diameter is greater than 4.8 cm or IMH thickness is greater than 11 mm (308).

8.3 Penetrating Atherosclerotic Ulcer.   PAU refers to an atherosclerotic lesion with ulceration that penetrates the internal elastic lamina and allows hematoma formation within the media of the aortic wall (309). This lesion sets the stage for development of IMH, AoD, or frank vessel rupture (309) (Figure 24). Anatomically PAUs develop in aortic segments where atherosclerotic changes are most common and therefore are localized to the descending thoracic aorta in over 90% of cases (310). When viewed tangentially, the classic appearance of the lesion is a mushroom-like outpouching of the aortic lumen with overhanging edges, resembling a gastric ulcer, as depicted on a barium study (Figure 24). The typical patient is elderly (usually over 65 years of age) and has hypertension and diffuse atherosclerosis, who presented with chest or back pain but without signs of aortic regurgitation or malperfusion. Less commonly, patients presented only with signs of distal embolization (311). Asymptomatic patients may also be found with aortic lesions that are indistinguishable, by imaging criteria, from PAUs (310,311).

View larger version (45K): [in this window] [in a new window] [Download PPT slide]   Figure 24 Penetrating atherosclerotic ulcer of the proximal descending thoracic aorta. Axial CT images at the level of the aortopulmonary window (left) and at the level of the left pulmonary artery (right) demonstrate a small penetrating ulcer (long arrow, U) that extends beyond the expected confines of the aortic lumen with adjacent IMH both at the level of the ulcer itself and that extends a few centimeters caudally in the wall of the descending thoracic aorta (short arrows). CT indicates computed tomographic imaging; IMH, intramural hematoma; and U, penetrating ulcer.

8.4 Pseudoaneurysms of the Thoracic Aorta.   Pseudoaneurysms of the thoracic aorta are frequently related to deceleration or torsional trauma to the aorta from motor vehicle accidents, falls, and sports injuries (3,313–319). Aortic pseudoaneurysms are relatively rare, with posttraumatic pseudoaneurysms having an incidence of 3% to 4% after blunt trauma (51). Other pseudoaneurysms may occur following aortic surgery, catheter-based interventions, or penetrating trauma. Pseudoaneurysms often have a slim "neck" that leads to the "aneurysm" that corresponds to points of penetration and containment (320). Aortic infections (mycotic aneurysms) and penetrating ulcers may also result in pseudoaneurysms (see Section 9.2.2). Penetrating injuries are usually repaired immediately whenever recognized and feasible (317,318,321).

8.5 Traumatic Rupture of the Thoracic Aorta.   A UK survey of all motor vehicle accident fatalities found that approximately 20% of patients had an autopsy finding of a ruptured aorta, emphasizing the importance of traumatic rupture of the aorta (TRA). In the United States, there are around 40 000 motor vehicle deaths annually, and it is likely that around 8000 of the victims had TRA. It is estimated that only 9% to 14% of patients with TRA reach a hospital alive and only 2% ultimately survive. In this survey, 29% were involved with frontal impact crashes and 44% were involved with side impact crashes (318,319).

Parmley and colleagues (318) noted the correlation of high risk of early death and the sites of TRA on the basis of autopsies in 275 deaths from unrelated aortic rupture. In 45%, the tear was at the aortic isthmus; 23%, in the ascending aorta; 13%, in the descending aorta; 8%, in the transverse aorta; 5%, in the abdominal aorta; and 6%, multiple sites.

Examination of the patient usually reveals signs similar to those of coarctation of the aorta with arm blood pressure higher than leg blood pressure, delay between radial versus femoral artery pulsation, and a harsh interscapular murmur (3). Evidence of polytrauma is, however, common.

The best method for detection of a TRA is debated. A chest x-ray with a nasogastric tube in position has 80% sensitivity for suggesting TRA by showing displacement of the nasogastric tube by the hematoma. However, signs of hemomediastinum are more often false positive than true positive (40). Even when present, mediastinal blood is less likely to be due to arterial/aortic injury than to less-consequential venous bleeding. A biplane contrast aortogram may fail to detect the tear until the development of a pseudoaneurysm. TEE may be used, but if dilatation has not occurred, the diagnosis may still be in doubt. CT is used but is not absolutely certain to establish the diagnosis. In questionable cases, intravascular ultrasound can also be used (3,322,323) (Figure 8). Realistically, the imaging sequence often depends on the stability of the patient and the need for the diagnosis of concomitant injuries. Sometimes, this may even fail to detect the tear, and the study may have to be repeated at a later date to detect the tear.

8.6 Evaluation and Management of Acute Thoracic Aortic Disease.   8.6.1 Initial Evaluation and Management
8.6.1.1 Recommendations for Estimation of Pretest Risk of Thoracic Aortic Dissection
Class I

1 Providers should routinely evaluate any patient presenting with complaints that may represent acute thoracic aortic dissection to establish a pretest risk of disease that can then be used to guide diagnostic decisions. This process should include specific questions about medical history, family history, and pain features as well as a focused examination to identify findings that are associated with aortic dissection, including:

a High-risk conditions and historical features (47,127,223,261) (Level of Evidence: B):

• Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, Turner syndrome, or other connective tissue disease.

• Patients with mutations in genes known to predispose to thoracic aortic aneurysms and dissection, such as FBN1, TGFBR1, TGFBR2, ACTA2, and MYH11.

• Family history of aortic dissection or thoracic aortic aneurysm.

• Known aortic valve disease.

• Recent aortic manipulation (surgical or catheter-based).

• Known thoracic aortic aneurysm.

b High-risk chest, back, or abdominal pain features (37,47,215,223,261,264,288) (Level of Evidence: B):

• Pain that is abrupt or instantaneous in onset.

• Pain that is severe in intensity.

• Pain that has a ripping, tearing, stabbing, or sharp quality.

c High-risk examination features (37,47,253,257,261,324) (Level of Evidence: B):

• Pulse deficit.

• Systolic blood pressure limb differential greater than 20 mm Hg.

• Focal neurologic deficit.

• Murmur of aortic regurgitation (new).

2 Patients presenting with sudden onset of severe chest, back, and/or abdominal pain, particularly those less than 40 years of age, should be questioned about a history and examined for physical features of Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, Turner syndrome, or other connective tissue disorder associated with thoracic aortic disease. (223) (Level of Evidence: B)

3 Patients presenting with sudden onset of severe chest, back, and/or abdominal pain should be questioned about a history of aortic pathology in immediate family members as there is a strong familial component to acute thoracic aortic disease. (223) (Level of Evidence: B)

4 Patients presenting with sudden onset of severe chest, back, and/or abdominal pain should be questioned about recent aortic manipulation (surgical or catheter-based) or a known history of aortic valvular disease, as these factors predispose to acute aortic dissection. (Level of Evidence: C)

5 In patients with suspected or confirmed aortic dissection who have experienced a syncopal episode, a focused examination should be performed to identify associated neurologic injury or the presence of pericardial tamponade (seeSection 8.1.6). (Level of Evidence: C)

6 All patients presenting with acute neurologic complaints should be questioned about the presence of chest, back, and/or abdominal pain and checked for peripheral pulse deficits as patients with dissection-related neurologic pathology are less likely to report thoracic pain than the typical aortic dissection patient (253) (seeSection 8.1.7). (Level of Evidence: C)

8.6.1.2 Laboratory Testing
Several plasma markers have been investigated for their utility in the evaluation of acute AoD. Plasma smooth muscle myosin heavy chain protein, D-dimer, and high-sensitivity C-reactive protein have shown diagnostic promise, although a lack of large prospective studies precludes a recommendation regarding their use (325–328).

Elevation of D-dimer levels occurs with intravascular activation of the coagulation cascade and secondary fibrinolysis and in conditions such as venous thromboembolism, sepsis, disseminated intravascular coagulation, malignancies, recent trauma or surgery, and acute MI and following fibrinolytic therapy. The ACEP has published guidelines regarding the use of certain D-dimer assays to rule out pulmonary embolism in low-risk patients (329).

Regarding the potential role of plasma D-dimer levels to screen for AoD, significant elevations of D-dimer were seen in all 24 patients with documented acute AoD involving either the ascending or descending thoracic aorta regardless of time from presentation, ranging from 1 to 120 hours (325). A meta-analysis of 11 studies (330) noted that the pooled sensitivity of D-dimer in 349 patients with documented acute AoD was 94% (95% CI 91% to 96%) with specificity ranging from 40% to 100%. Two patients had limited ascending aortic IMH without intimal flap and had negative D-dimer assays (331).

Some authors (325,332) recommend that D-dimer assays be performed in all patients where clinical suspicion exists, to help identify those who do not require definitive imaging studies. However, the efficacy and safety of this strategy have not been tested in a large clinical trial, and several caveats should apply. The negative likelihood ratio provided by the most sensitive D-dimer assay is not of sufficient magnitude to provide useful information in high-risk individuals and therefore cannot be used to "rule out" the disease in this group. Clinical scoring systems to identify the true pretest probability for AoD in individual patients have not been developed or validated, thus limiting an accurate determination of the true "posttest" probability associated with a negative D-dimer result. Finally, there are reports of negative D-dimer assays associated with ascending aortic IMH or a thrombosed false lumen, such that further studies are needed regarding the sensitivity of D-dimer levels to detect the presence of IMH or PAU (331). Given these issues, the writing committee cannot recommend serum D-dimer screening for all patients being evaluated for AoD.

Where a high level of suspicion for acute AoD exists, laboratory testing aimed at presurgical screening (blood count, serum chemistries, coagulation profiles, and blood type and screen) may reduce preoperative delays.

8.6.1.3 Recommendations for Screening Tests
Class I

1 An electrocardiogram should be obtained on all patients who present with symptoms that may represent acute thoracic aortic dissection.

a Given the relative infrequency of dissection-related coronary artery occlusion, the presence of ST-segment elevation suggestive of myocardial infarction should be treated as a primary cardiac event without delay for definitive aortic imaging unless the patient is at high risk for aortic dissection. (37,47,333) (Level of Evidence: B)

2 The role of chest x-ray in the evaluation of possible thoracic aortic disease should be directed by the patient's pretest risk of disease as follows:

a Intermediate risk: Chest x-ray should be performed on all intermediate-risk patients, as it may establish a clear alternate diagnosis that will obviate the need for definitive aortic imaging. (Level of Evidence: C)

b Low risk: Chest x-ray should be performed on all low-risk patients, as it may either establish an alternative diagnosis or demonstrate findings that are suggestive of thoracic aortic disease, indicating the need for urgent definitive aortic imaging. (Level of Evidence: C)

3 Urgent and definitive imaging of the aorta using transesophageal echocardiogram, computed tomographic imaging, or magnetic resonance imaging is recommended to identify or exclude thoracic aortic dissection in patients at high risk for the disease by initial screening. (42–46,67,73) (Level of Evidence: B)

Class III

1 A negative chest x-ray should not delay definitive aortic imaging in patients determined to be high risk for aortic dissection by initial screening. (Level of Evidence: C)

8.6.1.4 Recommendations for Diagnostic Imaging Studies
Class I

1 Selection of a specific imaging modality to identify or exclude aortic dissection should be based on patient variables and institutional capabilities, including immediate availability. (Level of Evidence: C)

2 If a high clinical suspicion exists for acute aortic dissection but initial aortic imaging is negative, a second imaging study should be obtained. (212) (Level of Evidence: C)

8.6.1.5 Recommendations for Initial Management
Class I

1 Initial management of thoracic aortic dissection should be directed at decreasing aortic wall stress by controlling heart rate and blood pressure as follows:

a In the absence of contraindications, intravenous beta blockade should be initiated and titrated to a target heart rate of 60 beats per minute or less. (Level of Evidence: C)

b In patients with clear contraindications to beta blockade, nondihydropyridine calcium channel-blocking agents should be used as an alternative for rate control. (Level of Evidence: C)

c If systolic blood pressures remain greater than 120 mm Hg after adequate heart rate control has been obtained, then angiotensin-converting enzyme inhibitors and/or other vasodilators should be administered intravenously to further reduce blood pressure that maintains adequate end-organ perfusion. (Level of Evidence: C)

d Beta blockers should be used cautiously in the setting of acute aortic regurgitation because they will block the compensatory tachycardia. (5) (Level of Evidence: C)

Class III

1 Vasodilator therapy should not be initiated prior to rate control so as to avoid associated reflex tachycardia that may increase aortic wall stress, leading to propagation or expansion of a thoracic aortic dissection. (Level of Evidence: C)

8.6.1.6 Recommendations for Definitive Management
Class I

1 Urgent surgical consultation should be obtained for all patients diagnosed with thoracic aortic dissection regardless of the anatomic location (ascending versus descending) as soon as the diagnosis is made or highly suspected. (Level of Evidence: C)

2 Acute thoracic aortic dissection involving the ascending aorta should be urgently evaluated for emergent surgical repair because of the high risk of associated life-threatening complications such as rupture. (47) (Level of Evidence: B)

3 Acute thoracic aortic dissection involving the descending aorta should be managed medically unless life-threatening complications develop (e.g., malperfusion syndrome, progression of dissection, enlarging aneurysm, inability to control blood pressure or symptoms). (285,288,334–337) (Level of Evidence: B)

Early identification of acute thoracic dissection is challenging. During the initial evaluation, the correct diagnosis of AoD has been made in only 15% to 43% of patients initially thought to have the disease (215,237,252). Factors that may impede accurate diagnosis of AoD include the following:

1 Acute AoD is often believed to be a rare disease (2.9 to 3.5 cases per 100 000 person-years) (215,217), whereas the incidence of acute MI is several orders of magnitude greater (more than 200 cases per 100 000 person-years) (338). Data previously cited in this guideline from UHC suggest that acute AoD is not "rare." Some common explanations that clinicians give for this underlying belief include the following:

a It is difficult for clinicians to effectively separate patients with AoD from the multitude of other patients who present to emergency departments and primary care physicians with common complaints that are much more often not due to acute AoD.

b Front-line medical providers may have little direct experience with acute AoD and are unlikely to be aware of the subtleties of its presenting signs and symptoms.

c Institutional multidisciplinary pathways developed for other emergencies such as ST-elevation myocardial infarction (STEMI) or acute stroke have not generally existed for acute AoD.

2 In contrast to other more common cardiovascular emergencies, acute AoD may occur in younger patients. Accurate identification of acute AoD; however, requires that clinicians recognize on a routine basis that the disease may present in younger patients. Case reports exist of children as young as 3 years of age presenting with acute AoD (105).

3 Acute AoD may present with a wide range of unusual manifestations that do not conform with classic "textbook findings." (339–341)

4 There are no well-studied, rapidly available, and effective screening tests for acute AoD.

8.6.2 Evaluation and Management Algorithms
The provided algorithms guide the initial evaluation of patients whose presentations are concerning for AoD and the management of patients in whom the diagnosis of acute thoracic AoD is confirmed. Although clinicians may ultimately choose to deviate from the pathway for patient-specific reasons, the algorithms provide a framework with which to quickly diagnose (Figure 25) and provide early management (Figure 26) of AoD. This decision model is supported by several large studies that indicate a targeted history and physical examination are likely to identify the vast majority of patients who present with acute AoD, suggesting that adequate screening need not be time intensive or technology dependent (47,215,264). Using a target history and physical examination, patients can be placed into 1 of 3 categories: 1) those with immediately apparent acute AoD requiring emergent surgical evaluation and expedited aortic imaging, 2) those whose presentation is concerning for acute AoD and in the absence of a clear alternative diagnosis require expedited aortic imaging, and 3) those whose clinical presentation is not initially suggestive of acute AoD but may benefit from aortic imaging in the absence of a likely alternative diagnosis at the completion of the initial evaluation.

View larger version (60K): [in this window] [in a new window] [Download PPT slide]   Figure 25 AoD evaluation pathway. ACS indicates acute coronary syndrome; AoD, aortic dissection; BP, blood pressure; CNS, central nervous system; CT, computed tomographic imaging; CXR, chest x-ray; EKG, electrocardiogram; MR, magnetic resonance imaging; STEMI, ST-elevation myocardial infarction; TAD; thoracic aortic disease; and TEE, transesophageal echocardiogram.

View larger version (60K): [in this window] [in a new window] [Download PPT slide]   Figure 26 Acute AoD management pathway. AoD indicates aortic dissection; BP, blood pressure; MAP, mean arterial pressure; and TTE, transthoracic echocardiogram.

Pain (Figure 25, T2–2) is the most commonly reported presenting symptom of acute AoD regardless of patient age, sex, or other associated clinical complaint (37,47,215,223,242,264,289). Pain described as abrupt or instantaneous in onset, that is severe in intensity, or that has a ripping or tearing quality establishes a high pretest probability for AoD (47,261).

The combination of 2 or more high-risk features (Figure 25, T3) is strongly suggestive of acute AoD.

The presence of a single high-risk feature (i.e., high-risk condition, pain, or physical examination) may trigger immediate concern for acute AoD; however, other diagnostic considerations may exist. Pain with high-risk features, although suggestive of acute AoD, may occur as a result of an alternate disease process (Table 12). For patients who are determined to have an intermediate probability of acute AoD on the basis of initial bedside assessment, Figure 25, T4, provides a pathway for further evaluation.

For patients presenting with new ST-segment elevations on the initial ECG and without high-risk AoD features, immediate coronary angiography and reperfusion therapy (i.e., thrombolysis or percutaneous coronary intervention) are indicated (333). However, if coronary angiography is performed and no culprit coronary lesion is identified, then Figure 25, T6, provides a pathway to dedicated aortic imaging. As approximately 40% of chest films in acute AoD lack a widened mediastinum, and as many as 16% are normal, the absence of radiographic abnormalities does not exclude the diagnosis of AoD (37,47) (Figure 25, T7).