|
| HOME | SUBSCRIPTIONS | CURRENT ISSUE | PAST ISSUES | CARDIOSOURCE | SEARCH | HELP | FEEDBACK |
|
|
|
|||||||||
|
|||||||||||
|
J Am Coll Cardiol, 2001; 37:885-892 © 2001 by the American College of Cardiology Foundation |
* Division of Cardiothoracic Surgery, University of Florida Health Science Center, Jacksonville, Florida, USA
Duke Clinical Research Institute, Durham, North Carolina, USA
University of British Columbia, Vancouver, Canada
University of Colorado Health Science Center, Denver, Colorado, USA
Manuscript received July 28, 2000; revised manuscript received October 16, 2000, accepted November 29, 2000.
Reprint requests and correspondence: Dr. Fred H. Edwards, Division of Cardiothoracic Surgery, University of Florida Health Science Center, 653-2 West Eighth Street, Jacksonville, Florida 32209-6511
fhe{at}mediaone.net
 |
Abstract |
|---|
 Top Abstract MethodsResultsDiscussionReferences |
|---|
We sought to develop national benchmarks for valve replacement surgery by developing statistical risk models of operative mortality.
BACKGROUND
National risk models for coronary artery bypass graft surgery (CABG) have gained widespread acceptance, but there are no similar models for valve replacement surgery.
METHODS
The Society of Thoracic Surgeons National Cardiac Surgery Database was used to identify risk factors associated with valve surgery from 1994 through 1997. The population was drawn from 49,073 patients undergoing isolated aortic valve replacement (AVR) or mitral valve replacement (MVR) and from 43,463 patients undergoing CABG combined with AVR or MVR. Two multivariable risk models were developed: one for isolated AVR or MVR and one for CABG plus AVR or CABG plus MVR.
RESULTS
Operative mortality rates for AVR, MVR, combined CABG/AVR and combined CABG/MVR were 4.00%, 6.04%, 6.80% and 13.29%, respectively. The strongest independent risk factors were emergency/salvage procedures, recent infarction, reoperations and renal failure. The c-indexes were 0.77 and 0.74 for the isolated valve replacement and combined CABG/valve replacement models, respectively. These models retained their predictive accuracy when applied to a prospective patient population undergoing operation from 1998 to 1999. The Hosmer-Lemeshow goodness-of-fit statistic was 10.6 (p = 0.225) for the isolated valve replacement model and 12.2 (p = 0.141) for the CABG/valve replacement model.
CONCLUSIONS
Statistical models have been developed to accurately predict operative mortality after valve replacement surgery. These models can be used to enhance quality by providing a national benchmark for valve replacement surgery.
| ||||||||||||||||||||
Using data from the Society of Thoracic Surgeons National Cardiac Surgery Database (STS Database), we characterized operative outcomes after isolated valve replacement and CABG plus valve surgery. We identified major preoperative predictors of mortality and developed risk models that would accurately estimate operative mortality (OM). We then assessed the performance of these models in a prospective patient population.
|
Methods |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
Participants in the STS Database receive individualized, semi-annual, risk-adjusted surgery outcomes, along with direct comparisons with the aggregate database population. This feedback is used for internal quality improvement efforts and is not publicly released. The mortality risk models are an integral part of the participants’ software, which allows the users to generate risk-adjusted outcomes data locally, compared with the national experience.
Patient population. The models were developed using data on all patients undergoing aortic valve replacement (AVR) or mitral valve replacement (MVR) either alone or in combination with CABG from January 1, 1994 through December 31, 1997. This included those patients receiving either mechanical or bioprosthetic valve replacement, but excluded those receiving valve repair surgery. In addition, patient records were excluded from the study if they were missing age or gender (<0.1% of records), if they were receiving tricuspid or pulmonary valve surgery or if they were having multivalve replacement surgery. In addition, all patients having a diagnosis of congenital heart disease were excluded. Finally, those undergoing cardiac surgery combined with other cardiac procedures were excluded. The resultant database contains clinical information on 92,536 patients. A total of 49,073 patients received isolated AVR or MVR, and 43,463 patients received combined CABG/valve surgery.
The external validation sample consisted of 51,492 patients in the STS Database who received valve replacement from January 1, 1998 to December 31, 1999. In this group, 25,640 patients received isolated valve replacement, whereas the remaining 25,852 patients underwent combined CABG/valve surgery.
Data definitions. Operative mortality is defined as 1) all deaths occurring during the hospital period in which the operation was performed; and 2) those deaths occurring after hospital discharge, but within 30 days of the procedure, unless the cause of death is clearly unrelated to the operation. Definitions of risk factors used in this analysis are provided in the STS web site.
Analysis. Each of the STS "core data set" risk factors were considered for inclusion into the model. Patient demographic data were compared (Table 1), and univariate OM rates for each risk factor were examined. This information, along with clinical evaluation of the risk factors, was used to determine the model variables. We constructed two models—one that included isolated valve procedures (AVR and MVR) and another that included combined (CABG plus valve replacement) procedures.
|
 |
Assessment of model performance. Model performance was assessed both internally and externally. The internal approach involved direct comparison of predicted versus observed results within the data on which the model was derived. The c-index, which reflects the ability of a model to discriminate patients who died during the operation from survivors, was calculated to evaluate model discrimination. For model calibration, patients were ordered by their predicted OM and then classified into 10 groups of equal size. Average predicted versus observed OM rates were then compared for each of the groups across the risk spectrum.
We also tested the model in a population separate from the derived population. For this independent data set, we selected registered patients undergoing operation in 1998 or 1999. The screening criteria described earlier were applied to all patients in this database, yielding 25,640 patients in the "isolated valve test set" and 25,852 patients in the "CABG plus valve test set." Average predicted and observed OM rates were then compared for each group. The c-index for the model applied to this population was also calculated.
|
Results |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
Patient outcomes. Outcomes for the four procedural groups are presented in Table 2. Operative mortality was higher in those receiving combined procedures than in those receiving isolated valve surgery. Likewise, OM was higher in those receiving MVR than in those receiving AVR. Higher complication rates and longer postoperative hospital stays were also noted in those receiving combined CABG/valve surgery (vs. isolated valve surgery) and in those receiving mitral (vs. aortic) valve procedures.
|
|
|
|
|
|
The overall predicted mortality rates for the 1998 to 1999 test set were very similar to the observed mortality rates (Fig. 3 and 4). For the isolated valve model, the overall predicted mortality rate was 4.8%, compared with an observed rate of 4.7%. For the CABG/valve model, the predicted mortality rate was 8.6%, compared with an 8.2% observed mortality rate.
|
|
|
Discussion |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
The results of valve replacement surgery should also be considered an important element in the evaluation of cardiac surgery results. Unfortunately, there have been few national or large regional studies of valve surgery comparable to those of coronary surgery. Accordingly, the risk factors associated with valve surgery are more obscure, and acceptable outcomes are more difficult to define. Risk models have only recently been used to evaluate patients undergoing valve replacement surgery (7,8).
Clinical application. The use of a national database has obvious value in this context. The STS Database has detailed preoperative, intraoperative and postoperative information on patients undergoing valve replacement surgery in a wide variety of centers throughout the country. The centers include academic, private, military and Veterans Affairs practices, which, in aggregate, should represent a reasonable estimate of the "average" national experience.
The use of this population to develop statistical risk models should serve as a unique benchmark for quality assurance. With the risk models presented in this report, it becomes possible for centers to obtain an objective and reproducible estimate of OM based on national results. It is instructive to illustrate this concept with an example: a given institution seeking to assess its valve surgery OM may enter its patient population into the STS models to generate a predicted OM for each patient. The average predicted mortality (P%) for the population is then calculated. The following statement is warranted: "Based on the accumulated experience of the STS Database, of every 100 patients with comparable risk factors, P would be expected to die after valve replacement surgery." The actual OM for the population should be compared with the predicted OM. If there is no significant difference, it is reasonable to conclude that the results of this institution conform with an accepted national average. If there is a significant difference, it should prompt the institution to investigate the issue more thoroughly. The STS holds the position that differences between predicted and actual OM rates do not invariably signal substandard care, but such differences should be a cause for more detailed examination (9).
Comparison with previous studies. The initial attempt to model valve OM using the STS Database was begun five years ago (7). This effort focused on the population from 1986 to 1995, which, in retrospect, constitutes a more heterogeneous group of patients undergoing a broader array of valve procedures. Furthermore, data gathered in the 1980s were not subject to the more rigorous screening criteria imposed in the 1990s, so that a significant portion of the 1986 to 1995 population may contain information that does meet current quality standards. In addition, the STS "core data set" variables had not been developed, so the model risk factors include several variables that are not now considered necessary for collection. These early models served a useful purpose and provided a necessary step in the evolution of our outcomes analyses; however, the present models represent a clear improvement by obviating most of the aforementioned shortcomings.
The pioneering work of the Veterans Affairs Cardiac Surgery Consultants Committee has been particularly important in this field (5,8). The scientific development and the practical application of risk models by this organization have been exemplary, but their population, by design, is restricted to Veterans Affairs centers. The select population of Veterans Affairs hospitals may well preclude application of their models on a broader scale.
Study limitations. Statistical risk models are valuable as quality assurance tools and as aids to medical decision making; however, one should not place an undue premium on their value. Models should not dictate therapy, nor should they arbitrarily brand a practice as "acceptable" or "substandard." They are designed to serve as aids, not to serve as the answer. Results of risk models should be generally considered as one would regard the results of a laboratory test—one piece of the puzzle that should be evaluated in concert with clinical judgment and other more traditional forms of assessment (9–11).
The broad scope of the STS Database suggests that this aggregate experience defines an acceptable standard of care. Although this is a logical conclusion, it may not be true. It is possible that regional geographic differences and select referral patterns are so disparate that it is unreasonable to hold all practices to a single standard. This issue is presently under investigation by the STS Database Committee. For now, it may be most appropriate to consider these data as a "national average" rather than a "national standard" (9).
Future investigations. Operative mortality is certainly the most important and the most easily measured of surgical outcomes, but other outcomes also have a major impact on patient care. We are presently developing models to predict various forms of operative morbidity, with special emphasis on postoperative neurologic dysfunction and the need for prolonged ventilatory support. Models to predict length of hospital stay and cost are also being investigated.
The STS has assisted with several regional and state initiatives to gather and analyze data on a regional level. These studies will be compared with national data to determine whether significant differences exist. At this point, one state has developed a risk model of CABG mortality based solely on its state population. After extensive testing of this "state model," it was found to be essentially identical to the national model. Future efforts along these lines should determine whether the national experience with cardiac surgery should be considered as a standard of care or whether regionalization is necessary to establish fair standards.
Conclusions. These STS risk models fill a void in our ability to assess surgical outcomes associated with valve replacement surgery. They allow one to determine the net impact of all important preoperative risk factors to predict the probability of postoperative mortality in patients undergoing valve surgery. This information, in turn, can be used as a benchmark to compare risk-stratified patient groups with a large multi-institutional experience that approximates a national standard of care.
|
References |
|---|
|
TopAbstractMethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  P. T.L. Chiam and C. E. Ruiz Percutaneous Transcatheter Aortic Valve Implantation: Assessing Results, Judging Outcomes, and Planning Trials: The Interventionalist Perspective J. Am. Coll. Cardiol. Intv., August 1, 2008; 1(4): 341 - 350. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Filsoufi, J. Chikwe, J. G. Castillo, P. B. Rahmanian, J. Vassalotti, and D. H. Adams Prosthesis type has minimal impact on survival after valve surgery in patients with moderate to end-stage renal failure Nephrol. Dial. Transplant., July 7, 2008; (2008) gfn337v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Vahanian, O. R. Alfieri, N. Al-Attar, M. J. Antunes, J. Bax, B. Cormier, A. Cribier, P. De Jaegere, G. Fournial, A. P. Kappetein, et al. Transcatheter valve implantation for patients with aortic stenosis: a position statement from the European Association of Cardio-Thoracic Surgery (EACTS) and the European Society of Cardiology (ESC), in collaboration with the European Association of Percutaneous Cardiovascular Interventions (EAPCI). Eur. J. Cardiothorac. Surg., July 1, 2008; 34(1): 1 - 8. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. K. Song, J. D. Grab, S. M. O'Brien, K. F. Welke, F. Edwards, and R. M. Ungerleider Gender differences in mortality after mitral valve operation: evidence for higher mortality in perimenopausal women. Ann. Thorac. Surg., June 1, 2008; 85(6): 2040 - 2045. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Vahanian, O. Alfieri, N. Al-Attar, M. Antunes, J. Bax, B. Cormier, A. Cribier, P. De Jaegere, G. Fournial, A. P. Kappetein, et al. Transcatheter valve implantation for patients with aortic stenosis: a position statement from the European Association of Cardio-Thoracic Surgery (EACTS) and the European Society of Cardiology (ESC), in collaboration with the European Association of Percutaneous Cardiovascular Interventions (EAPCI) Eur. Heart J., June 1, 2008; 29(11): 1463 - 1470. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. M. Fedoruk, H. Wang, M. R. Conaway, I. L. Kron, and K. C. Johnston Statin therapy improves outcomes after valvular heart surgery. Ann. Thorac. Surg., May 1, 2008; 85(5): 1521 - 1525. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Nozohoor, J. Nilsson, C. Luhrs, A. Roijer, and J. Sjogren Influence of Prosthesis-Patient Mismatch on Diastolic Heart Failure After Aortic Valve Replacement Ann. Thorac. Surg., April 1, 2008; 85(4): 1310 - 1317. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Iung Management of the elderly patient with aortic stenosis Heart, April 1, 2008; 94(4): 519 - 524. [Full Text] [PDF]
|
|
|
|
 |
|
 T. K. Rosengart, T. Feldman, M. A. Borger, T. A. Vassiliades Jr, A. M. Gillinov, K. J. Hoercher, A. Vahanian, R. O. Bonow, and W. O'Neill Percutaneous and Minimally Invasive Valve Procedures: A Scientific Statement From the American Heart Association Council on Cardiovascular Surgery and Anesthesia, Council on Clinical Cardiology, Functional Genomics and Translational Biology Interdisciplinary Working Group, and Quality of Care and Outcomes Research Interdisciplinary Working Group Circulation, April 1, 2008; 117(13): 1750 - 1767. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. van Gameren, A. P. Kappetein, E. W. Steyerberg, A. C. Venema, E. A.J. Berenschot, E. L. Hannan, A. J.J.C. Bogers, and J. J.M. Takkenberg Do We Need Separate Risk Stratification Models for Hospital Mortality After Heart Valve Surgery? Ann. Thorac. Surg., March 1, 2008; 85(3): 921 - 930. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. H. Mehta, J. D. Grab, S. M. O'Brien, D. D. Glower, C. K. Haan, J. S. Gammie, E. D. Peterson, and on Behalf of the Society of Thoracic Surgeons Nati Clinical Characteristics and In-Hospital Outcomes of Patients With Cardiogenic Shock Undergoing Coronary Artery Bypass Surgery: Insights From the Society of Thoracic Surgeons National Cardiac Database Circulation, February 19, 2008; 117(7): 876 - 885. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. D. Desai and G. T. Christakis Bioprosthetic Aortic Valve Replacement: Stented Pericardial and Porcine Valves Card. Surg. Adult, January 1, 2008; 3(2008): 857 - 894. [Full Text]
|
|
|
|
|
|
T. Gudbjartsson, T. Absi, and S. Aranki Mitral Valve Replacement Card. Surg. Adult, January 1, 2008; 3(2008): 1031 - 1068. [Full Text]
|
|
|
|
|
|
T. Feldman and M. B. Leon Prospects for Percutaneous Valve Therapies Circulation, December 11, 2007; 116(24): 2866 - 2877. [Full Text] [PDF]
|
|
|
|
|
|
J.-L. Monin, M. Monchi, M. E.W. Kirsch, H. Petit-Eisenmann, S. Baleynaud, C. Chauvel, D. Metz, C. Adams, J.-P. Quere, P. Gueret, et al. Low-gradient aortic stenosis: impact of prosthesis-patient mismatch on survival Eur. Heart J., November 1, 2007; 28(21): 2620 - 2626. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Kalkat, M.-B. Edwards, K. M. Taylor, and R. S. Bonser Composite Aortic Valve Graft Replacement: Mortality Outcomes in a National Registry Circulation, September 11, 2007; 116(11_suppl): I-301 - I-306. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. L. Grover, J. E. Mayer Jr, N. Kouchoukos, R. Guyton, F. Edwards, and J. Bavaria Letter by Grover et al Regarding Article, "Percutaneous Implantation of the CoreValve Self-Expanding Valve Prosthesis in High-Risk Patients With Aortic Valve Disease: The Siegburg First-in-Man Study" Circulation, June 5, 2007; 115(22): e612 - e612. [Full Text] [PDF]
|
|
|
|
|
|
F. B. Vanky, E. Hakanson, and R. Svedjeholm Long-Term Consequences of Postoperative Heart Failure After Surgery for Aortic Stenosis Compared With Coronary Surgery Ann. Thorac. Surg., June 1, 2007; 83(6): 2036 - 2043. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Kuduvalli, A. D. Grayson, J. Au, G. Grotte, B. Bridgewater, B. M. Fabri, and on behalf of the North West Quality Improvement Pr A multi-centre additive and logistic risk model for in-hospital mortality following aortic valve replacement Eur. J. Cardiothorac. Surg., April 1, 2007; 31(4): 607 - 613. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Shahian, F. H. Edwards, V. A. Ferraris, C. K. Haan, J. B. Rich, S.-L. T. Normand, E. R. DeLong, S. M. O'Brien, C. M. Shewan, R. S. Dokholyan, et al. Quality Measurement in Adult Cardiac Surgery: Part 1--Conceptual Framework and Measure Selection Ann. Thorac. Surg., April 1, 2007; 83(4_Supplement): S3 - S12. [Full Text] [PDF]
|
|
|
|
|
|
E. L. Hannan, C. Wu, E. V. Bennett, R. E. Carlson, A. T. Culliford, J. P. Gold, R. S.D. Higgins, C. R. Smith, and R. H. Jones Risk Index for Predicting In-Hospital Mortality for Cardiac Valve Surgery Ann. Thorac. Surg., March 1, 2007; 83(3): 921 - 929. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. S. Gammie, S. M. O'Brien, B. P. Griffith, T. B. Ferguson, and E. D. Peterson Influence of Hospital Procedural Volume on Care Process and Mortality for Patients Undergoing Elective Surgery for Mitral Regurgitation Circulation, February 20, 2007; 115(7): 881 - 887. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Boku, M. Masuda, M. Eto, T. Nishida, S. Morita, and R. Tominaga Risk Evaluation and Midterm Outcome of Cardiac Surgery in Patients on Dialysis Asian Cardiovasc Thorac Ann, February 1, 2007; 15(1): 19 - 23. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Authors/Task Force Members, A. Vahanian, H. Baumgartner, J. Bax, E. Butchart, R. Dion, G. Filippatos, F. Flachskampf, R. Hall, B. Iung, et al. Guidelines on the management of valvular heart disease: The Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology Eur. Heart J., January 26, 2007; (2007) ehl428v1. [Full Text] [PDF]
|
|
|
|
|
|
R. H. Mehta, J. D. Grab, S. M. O'Brien, C. R. Bridges, J. S. Gammie, C. K. Haan, T. B. Ferguson, E. D. Peterson, and for the Society of Thoracic Surgeons National Card Bedside Tool for Predicting the Risk of Postoperative Dialysis in Patients Undergoing Cardiac Surgery Circulation, November 21, 2006; 114(21): 2208 - 2216. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Florath, A. Albert, W. Hassanein, B. Arnrich, U. Rosendahl, I. C. Ennker, and J. Ennker Current determinants of 30-day and 3-month mortality in over 2000 aortic valve replacements: impact of routine laboratory parameters Eur. J. Cardiothorac. Surg., November 1, 2006; 30(5): 716 - 721. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. O. Bonow, B. A. Carabello, K. Chatterjee, A. C. de Leon Jr, D. P. Faxon, M. D. Freed, W. H. Gaasch, B. W. Lytle, R. A. Nishimura, P. T. O'Gara, et al. ACC/AHA 2006 Guidelines for the Management of Patients With Valvular Heart Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease) Developed in Collaboration With the Society of Cardiovascular Anesthesiologists Endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons J. Am. Coll. Cardiol., August 1, 2006; 48(3): e1 - e148. [Full Text] [PDF]
|
|
|
|
|
|
R. O. Bonow, B. A. Carabello, K. Chatterjee, A. C. de Leon Jr, D. P. Faxon, M. D. Freed, W. H. Gaasch, B. W. Lytle, R. A. Nishimura, P. T. O'Gara, et al. ACC/AHA 2006 Practice Guidelines for the Management of Patients With Valvular Heart Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease) Developed in Collaboration With the Society of Cardiovascular Anesthesiologists Endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons J. Am. Coll. Cardiol., August 1, 2006; 48(3): 598 - 675. [Full Text] [PDF]
|
|
|
|
|
|
J. S. Gammie, J. W. Brown, J. M. Brown, R. S. Poston, R. N. Pierson III, P. N. Odonkor, C. S. White, J. S. Gottdiener, and B. P. Griffith Aortic valve bypass for the high-risk patient with aortic stenosis. Ann. Thorac. Surg., May 1, 2006; 81(5): 1605 - 1610. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Cladellas, J. Bruguera, J. Comin, J. Vila, E. de Jaime, J. Marti, and M. Gomez Is pre-operative anaemia a risk marker for in-hospital mortality and morbidity after valve replacement? Eur. Heart J., May 1, 2006; 27(9): 1093 - 1099. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Chan, W.R. E. Jamieson, A. G. Fleisher, D. Denmark, F. Chan, and E. Germann Valve Replacement Surgery in End-Stage Renal Failure: Mechanical Prostheses Versus Bioprostheses. Ann. Thorac. Surg., March 1, 2006; 81(3): 857 - 862. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Iung, A. Cachier, G. Baron, D. Messika-Zeitoun, F. Delahaye, P. Tornos, C. Gohlke-Barwolf, E. Boersma, P. Ravaud, and A. Vahanian Decision-making in elderly patients with severe aortic stenosis: why are so many denied surgery? Eur. Heart J., December 2, 2005; 26(24): 2714 - 2720. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. S. Gammie, S. M. O'Brien, B. P. Griffith, and E. D. Peterson Surgical Treatment of Mitral Valve Endocarditis in North America Ann. Thorac. Surg., December 1, 2005; 80(6): 2199 - 2204. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. R. Nowicki What is the Future of Mortality Prediction Models in Heart Valve Surgery? Ann. Thorac. Surg., August 1, 2005; 80(2): 396 - 398. [Full Text] [PDF]
|
|
|
|
|
|
R. Jin, G. L. Grunkemeier, A. Starr, and Providence Health System Cardiovascular Study Grou Validation and Refinement of Mortality Risk Models for Heart Valve Surgery Ann. Thorac. Surg., August 1, 2005; 80(2): 471 - 479. [Abstract] [Full Text] [PDF]
|
|
