The impact of diabetes mellitus (DM) on the outcome of patients requiring cardiac surgery has been investigated in previous decades. However, the profile of cardiac surgical practice is changing in addition to changes in patients' risk profile, making the results inconclusive. In this study we sought to investigate the impact of DM on operative mortality and morbidity in patients undergoing cardiac surgery and adjust for patient and disease characteristics. In total 10,709 patients (9,229 nondiabetics and 1,480 diabetics) were admitted to the study; 5,557 patients (1,012 diabetics) underwent an isolated coronary operation, 1,775 patients (278 diabetics) underwent coronary plus valve operations, and 3,337 patients (209 diabetics) underwent valve operations. To control for differences in patient and disease characteristics, a propensity score (for DM) was performed. DM increased crude morbidity and this difference was maintained after risk adjustment for propensity score; conversely, the crude operative mortality risk was higher in diabetics but not significantly after adjustment for propensity score. Thereafter, DM remained independently associated to operative mortality risk in the valve population only (odds ratio 2.53, 95% confidence interval 1.45 to 4.4, p = 0.001). In conclusion, DM has a significant impact on operative mortality of patients undergoing heart valve surgery. Although diabetic patients undergoing coronary operations are not at increased risk of operative mortality, morbidity is significantly affected in the overall population.
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