Decreasing prevalence but increasing importance of left ventricular dysfunction and reoperative surgery in prediction of mortality in coronary artery bypass surgery: trends over 18 years

Objectives: The number of patients referred for coronary artery bypass grafting (CABG) has fallen, whereas their risk profile appears to be increasing. We evaluated changes in the predictors of hospital mortality among patients undergoing CABG during a span of 18 years.

Methods: Data were collected prospectively for all patients undergoing isolated CABG (n=23,445) from 1991 to 2008. To examine the effect of time on patients' risk profiles and outcomes, we divided patients into 3 time cohorts (1991-1996, n=8280; 1997-2002, n=9801; 2003-2008, n=5364). We used multivariable logistic regression model to identify predictors of mortality in the entire cohort and in each time cohort.

Results: Hospital mortality declined from 2.4% (1991-1996) to 1.2% (2003-2008; P<.0001). Urgent or emergency surgery, left ventricular dysfunction, reoperative CABG, increased age, female gender, hypertension, cardiogenic shock, congestive heart failure, peripheral vascular disease, left main disease, and earlier year of operation (1991-1996) were independent predictors of hospital mortality. The prevalence of most risk factors for mortality increased over the 18-year period of this study. In contrast, the prevalence of severe left ventricular dysfunction and reoperative CABG decreased significantly; however, their associated odds of mortality increased with time.

Conclusions: Whereas the prevalence of most risk factors increased with time, left ventricular dysfunction and reoperative CABG became significantly less common. However, the odds of mortality associated with these 2 predictors increased, indicating that although they occur less commonly, these 2 risk factors paradoxically play an increasingly important role in determining patient outcomes.