J Thorac Cardiovasc Surg 2004;127:1854-1855
© 2004 The American Association for Thoracic Surgery
Epidemiologic contrast of predictors' trends for outcomes of coronary artery bypass grafting: Heart failure versus ventricular function versus left main disease
Jeffrey H. Shuhaiber, MD
University of Illinois at Chicago, Chicago, IL 60612, USA
To the Editor:
I read with interest the article by Davierwala and colleagues1 in the November 2003 issue of the Journal. The work analyzed differential change in predictors of in hospital mortality after coronary artery bypass grafting. The study elegantly demonstrated the diminishing statistical significance for left ventricular function greater than 20% as a predictor for mortality during a 12-year period. Several explanations are provided related to patient comorbidity, interventional cardiology, surgeon experience, and intensive patient care. It is well established that one of the major determinants of morbidity during and after coronary artery bypass grafting is low left ventricular ejection fraction.2 The results of numerous coronary artery bypass grafting trials performed in the 1970s and 1980s show that despite this increased morbidity, the benefits of this procedure for patients with multivessel coronary artery disease and low left ventricular systolic function in many cases outweigh the risks.3 The article does not contain data for the actual causes of death in this large group of patients, which would be epidemiologically relevant. Given the data provided, however, it is difficult to observe a contrast in the trends between congestive heart failure (CHF) and left ventricular function as predictor variables. Davierwala and colleagues1 also stated in their discussion that from studying the data again in Table 1 it is clear to the reader that CHF held an increasing proportion as morbidity in the patient cohort (7.8% vs 9.4% vs 9.4%) during the interval (1990-1993 vs 1994-1997 vs 1998-2001). Moreover, according to the original article's Table 3, after a multivariate analysis CHF showed an increasing trend for odds ratio by year group (1.9 vs 3.6).1 Given this contrast of predictor outcome trends, the authors should have included other explanations. In simple terms, the CHF increasing trend could reflect an increase in diastolic heart failure, assuming that the proportions of new patients in each time interval were significant. In other words, the decline of the predictor value in left ventricular dysfunction was not related to interyear group patient death. The authors stated that left main disease in a "somewhat counterintuitive finding" was "unmasked" in the last time cohort, with an odds ratio of 1.7 in Table 3 of the original article.1 From their data, both CHF and left main disease increased in prevalence, yet worsening ventricular dysfunction declined. This constellation may reflect a change in the ventricular dysfunction function from systolic to diastolic biometrically.
Furthermore, the typical risk factors and comorbidities of female gender, diabetes, and hypertension together increased significantly during the entire period of their study. This association has now been found to be the same with diastolic dysfunction.4 As we know now, there is growing appreciation of diastolic heart failure as a distinct entity. There are 4.6 million people in the United States with heart failure today, and 550,000 new cases are being reported annually by the American Heart Association.5 Approximately 30% to 50% of patients with heart failure have a normal or nearly normal left ventricular ejection fraction.6 CHF is a leading cause of cardiac morbidity and mortality from cardiovascular disease. Although left ventricular diastolic dysfunction occurs in all patients with systolic dysfunction and CHF, a third of patients have CHF with isolated diastolic dysfunction. In the general population, the mortality among patients with diastolic heart failure is 4 times that among persons without heart failure but half that among patients with systolic heart failure. It is widely known that many physicians underappreciate diastolic function in heart failure.
Reinterpreting the data in the context of the discussion asks for other explanations. In the present era of advancements in echocardiography, diastolic dysfunction needs to be taken into consideration, especially when symptoms of congestive heart failure are present. If that is the case in this study, left ventricular dysfunction remains a predictor of outcome but with a change from systolic to diastolic. Finally, I ask Davierwala and colleagues to take a second look at their data in the light of this forgotten predictor variable. I would appreciate their feedback.
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References
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- Davierwala PM, Maganti M, Yau TM. Decreasing significance of left ventricular dysfunction and reoperative surgery in predicting coronary artery bypass grafting–associated mortality: a twelve-year study. J Thorac Cardiovasc Surg. 2003;126:1335–1344[Abstract/Free Full Text]
- Kurki TS, Kataja M. Preoperative prediction of postoperative morbidity in coronary artery bypass grafting. Ann Thoracic Surg. 1996;61:1740–1745[Abstract/Free Full Text]
- Christakis GT, Ivanov J, Weisel RD, Birnbaum PL, David TE, Salerno TA. The changing pattern of coronary artery bypass surgery. Circulation. 1989;80(3 Pt 1):I151–I161
- Kitzman DW, Little WC, Brubaker PH, Anderson RT, Hundley WG, Marburger CT, et al. Pathophysiological characterization of isolated diastolic heart failure in comparison to systolic heart failure. JAMA. 2002;288:2144–2150[Abstract/Free Full Text]
- American Heart Association. 2000 Heart and stroke statistical update. Dallas: The Association; 2000.
- Vasan RS, Benjamin EJ. Diastolic heart failure—no time to relax. N Engl J Med. 2001;344:56–59[Free Full Text]
Related Article
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Reply to the Editor
- Piroze M. Davierwala and Terrence M. Yau
J. Thorac. Cardiovasc. Surg. 2004 127: 1855.
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