ACC/AHA 2004 Guideline Update for Coronary Artery Bypass Graft Surgery: Summary Article: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery) FREE

The American College of Cardiology (ACC)/American Heart Association (AHA) Task Force on Practice Guidelines regularly reviews existing guidelines to determine when an update or full revision is needed. This process gives priority to areas where major changes in text, particularly recommendations, are mentioned on the basis of new understanding of evidence. Minor changes in verbiage and references are discouraged. The ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery published in 1999 have now been updated. The full-text guidelines incorporating the updated material are available on the Internet (www.acc.org or www.americanheart.org) in both a version that shows the changes from the 1999 guidelines in track changes mode, with strike-through indicating deleted text and underlining indicating new text, and a “clean” version that fully incorporates the changes. This article describes the major areas of change reflected in the update in a format that we hope can be read and understood as a stand-alone document. Please note we have changed the table of contents headings in the 1999 guidelines from roman numerals to unique identifying numbers. Interested readers are referred to the full-length Internet version to completely understand the context of these changes.

Classification of Recommendations and Level of Evidence are expressed in the ACC/AHA format as follows:

Classification of Recommendations

Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.

Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.

IIa: Weight of evidence/opinion is in favor of usefulness/efficacy.

IIb: Usefulness/efficacy is less well established by evidence/opinion.

Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective and in some cases may be harmful.

Level of Evidence

Level of Evidence A: Data are derived from multiple randomized clinical trials or meta-analyses.

Level of Evidence B: Data are derived from a single randomized trial, or nonrandomized studies.

Level of Evidence C: Only consensus opinion of experts, case studies, or standard of care.

(Please refer to Table 1 in the full-text guidelines for more details.)

New material was added on off-pump coronary artery bypass (OPCAB) and its role in neurological outcomes after CABG. The material is reproduced below:

OPCAB avoids both aortic cannulation and cardiopulmonary bypass. Accordingly, one would expect postoperative neurological deficits to be reduced in patients undergoing OPCAB. Three randomized controlled trials (1- 3) have not firmly established a significant change in neurological outcomes between OPCAB patients and conventional CABG patients. Each trial demonstrates problems inherent with small patient cohorts, differing definitions, and patient selection. At this point, there is insufficient evidence of a difference in neurological outcomes for patients undergoing OPCAB compared with those undergoing conventional CABG (4).

New material was added with clinical trial data comparing stents with CABG in patients with multivessel disease.(Table 1)was revised to incorporate stent trial data and outcomes at longer follow-up. The new text appears below:

Since the previous update of these guidelines, several trials comparing stents with CABG in patients with multivessel disease have been initiated. The Arterial Revascularization Therapies Study Group (ARTS) trial enrolled 1205 patients with multivessel coronary disease in whom a cardiac surgeon and interventional cardiologist agreed that they could achieve a similar extent of revascularization. In this randomized comparison, there was no difference at 1 year in the combined rate of death, myocardial infarction (MI), and stroke between the 2 revascularization strategies (5). However, repeat revascularization rates were higher with stenting (16.8% versus 3.5% with surgery), with a net cost savings of $2973 per patient favoring the stent approach. In patients with diabetes (n equals 198), the difference in repeat revascularization rates was even more disparate (22.3% with stents versus 3.1% with CABG), although overall event-free survival was similar (6) (Table 1)

Similar results were reported by the Stent or Surgery (SoS) trial investigators. The trial randomized 988 patients with multivessel disease (57% 2-vessel; 42% 3-vessel) to revascularization with percutaneous coronary intervention (PCI) (78% received stents) or CABG (81% with pedicled left internal mammary artery [IMA] graft). The primary end point of repeat revascularization occurred in 21% of PCI patients versus 6% of CABG patients at a median follow-up of 2 years (hazard ratio equals 3.85, P less than 0.0001). Freedom from angina was also better with surgery (79% versus 66%). Mortality was higher in the PCI group but was influenced by a particularly low surgical mortality and a high rate of noncardiovascular death in the PCI group (7).

In the Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) study, 454 patients at 16 VA hospitals with high-risk features for adverse outcome with surgery were randomized to either surgery or PCI. High-risk characteristics included prior open-heart surgery, age greater than 70 years, ejection fraction less than 0.35, MI within 7 days, and the need for an intra-aortic balloon pump (IABP). Stents were used in 54% of PCI patients. Survival was similar (79% with CABG and 80% with PCI) at 36 months 8. Finally, in the Stenting versus Internal Mammary Artery (SIMA) trial, 121 patients with isolated proximal left anterior descending coronary artery disease were randomly treated with stenting or CABG (using the IMA). At 2.4 years of follow-up, there were no differences in the rates of death, MI, functional class, medications, or quality of life. Repeat revascularization was required more often (31% versus 7%) in the stent group (9). Overall, 6 trials have now been published comparing CABG with PCI utilizing stents in single or multivessel disease. Compared with the earlier trials utilizing balloon angioplasty, stent usage and left IMA revascularization rates have increased (16- 26). The results in terms of death, MI, and stroke are similar in the more recent trials; however, the disparity in the need for repeat revascularization, which favors surgery, has narrowed (Table 1).

This section was added to reflect current understanding of the prognostic value of cardiac biomarkers when assessed after CABG.

Although more than 30 observational studies showed a reduced mortality for coronary disease in postmenopausal women taking hormone therapy, hormone replacement is no longer recommended for women undergoing CABG surgery. The new material can be found in the full-text guidelines.

The section on reoperation was rewritten to include emerging understanding of the nature and sequelae of late vein graft atherosclerosis. In patients in whom late vein graft stenosis is found in vein grafts supplying the LAD coronary artery, reoperation should be strongly considered to improve survival. The need for reoperation may be reduced as surgeons increasingly utilize arterial conduits for the primary revascularization. Please see the full-text guidelines for new material.

New text was added regarding the risk of CABG in acute coronary syndrome patients treated with new and more potent antithrombotic and antiplatelet therapies. This update reflects more recent nomenclature that defines the spectrum of acute coronary syndromes from unstable angina to non-ST-segment elevation MI to ST-segment elevation MI. Where appropriate, the writing committee used the new classification in the document, recognizing, however, that many of the cited trials categorized the patient subgroups according to the older nomenclature. The new text is reproduced below.

A new issue that has arisen concerns the risk of CABG in patients with acute coronary syndrome treated with new and more potent antithrombotic and antiplatelet therapies. Several studies have demonstrated a greater risk for postoperative hemorrhage in patients treated with low-molecular-weight heparin (10,10a,10b), abciximab 11, and clopidogrel 12. It is important to understand the pharmacokinetics of these agents to reduce the risk. For instance, no increased bleeding was observed when the short-acting glycoprotein IIb/IIIa inhibitor eptifibatide was discontinued at least 2 hours before bypass (13), when platelet transfusions were appropriately administered after abciximab (14), and when clopidogrel was withheld for 5 days before surgery (12). In some instances, the need for surgery supersedes the risk.

The section on less-invasive CABG was extensively rewritten to highlight advances in OPCAB with more recent clinical trial data. Please refer to the full-text guidelines for further details.

This new section was added to address the current understanding of robotic coronary bypass.

The Arterial and Alternate Conduits section was updated to include more recent trial data and explore the use of multiple IMA grafts (bilateral IMA, or BIMA).

This section was updated to include new prospective, controlled, randomized trials that demonstrate efficacy of transmyocardial revascularization (TMR) in select patients.

A new section on “Hospital Environment” was added to explain the process of clinical care surrounding CABG surgery and how appropriate implementation of clinical guidelines can show measurable improvement in outcomes.

The section “Areas in Need of Future Research” was eliminated because the material was covered in previous sections.

All of the recommendations in the CABG guideline update were written in full sentences that express a complete thought, such that a recommendation, even if separated and presented apart from the rest of the document, would still convey the full intent of the recommendation. It is hoped that this will increase readers’ comprehension of the guidelines. In the 1999 update, the committee did not rank the available scientific evidence in an A, B, or C fashion. The level of evidence for each recommendation is now provided. The rewritten recommendations appear under their respective headings below.