Background: Previous studies have demonstrated increased risk in patients undergoing coronary artery bypass surgery (CABG), but the effect of this increasing risk on outcomes has not been well documented. The purposes of this study were (1) to evaluate patients who had CABG from 1993 to 1995 (group III) and compare them with patients from 1981 through 1987 (group I) and 1988 through 1992 (group II) to determine if the trend toward higher-risk patients continued and (2) to evaluate what effect risk had on in-hospital outcomes.
Methods and results: Data were collected prospectively on patients undergoing CABG. Patients from the three time periods were compared by use of univariate and multivariate statistics. Risk models for mortality were developed by use of logistic regression. Significant changes were noted in the three time periods, with risk increasing over time. Increased risk was associated with increased mortality in group II, but mortality declined in group III despite the continued increase in patient risk. Group II had an increase in complications, with little change in group III. The actual mortality rate was lower than predicted in group III.
Conclusions: Patients undergoing CABG are increasingly high risk. In-hospital mortality rates declined during the period from 1993 through 1995 and were lower than predicted despite the increase in risk. This decreased mortality rate may reflect greater experience in providing care to high-risk patients and improved myocardial protection and surgical and anesthetic techniques. Although continued analysis of patient risk and benefit is needed, researchers must be cognizant of the rapid changes in technology and knowledge and should correlate changes in the process of care with outcomes.