Improved survival after coronary artery bypass grafting has not influenced the mortality disadvantage in patients with diabetes mellitus

Objectives: We sought to compare mortality after coronary artery bypass grafting in patients with and without diabetes mellitus undergoing operations during different time periods. Methods: We performed analyses of 12,415 primary isolated coronary artery bypass grafting operations performed during 1970-2003, with follow-up of 5-year mortality up to December 2006. Results: The prevalence of diabetes mellitus continuously increased up to 25% among patients undergoing coronary artery bypass grafting in 2003. The 1892 patients with type 2 diabetes mellitus were older, more often female, and more frequently had cardiovascular risk factors, acute coronary syndrome, 3-vessel disease, and severely reduced left ventricular function than patients without diabetes mellitus. Early mortality was 3.4% in patients with diabetes mellitus versus 1.8% in patients without diabetes mellitus. The multivariable adjusted odds ratio was 2.0, and the 95% confidence interval was 1.4 to 2.7. Early adjusted mortality was significantly lower in patients operated on during 2000-2003 than those operated on during 1970-1989 in patients with diabetes mellitus (odds ratio, 0.3; 95% confidence interval, 0.1-0.9) and without diabetes mellitus (odds ratio, 0.4; 95% confidence interval, 0.2-0.7). Mortality until 5 years was 14.6% in patients with diabetes mellitus versus 8.3% in patients without diabetes mellitus (hazard ratio, 1.8; 95% confidence interval, 1.5-2.0). Five-year mortality was reduced by 40% in patients operated on during 2000-2003 compared with that seen in those operated on during 1970-1989 in patients with and without diabetes mellitus. Conclusions: Diabetes mellitus was associated with an almost 2-fold increased risk of early and 5-year mortality. Early and late mortality were substantially reduced in patients with and without diabetes mellitus operated on more recently, but the mortality disadvantage associated with diabetes mellitus was not eliminated.