Risk of death or acute myocardial infarction 10 years after coronary artery bypass surgery in relation to type of diabetes

BackgroundThe aim of this study was to assess the long-term risk of death or acute myocardial infarction (AMI) in patients with diabetes mellitus (DM) compared with that in patients without DM after coronary artery bypass grafting (CABG).MethodsNational registers were used to record death or AMI occurring in 6727 patients who had CABG during 1980 to 1995. Diabetes mellitus in 856 patients (13%) was classified as type 1 (6%) or type 2 treated with insulin (29%), oral drugs (46%), or diet (19%).ResultsThe risk of death ≤30 days of the operation was increased in patients with insulin-treated type 2 DM (odds ratio [OR] 4.6, 95% CI 2.5-8.4) and in those on oral antidiabetic drugs (OR 2.0, 95% CI 1.0-3.8), but not in diet-treated diabetic patients, compared with that in patients without diabetes. At 10 years, the relative risk of death or having an AMI was 1.8 (95% CI 1.5-2.2) in insulin-treated patients and 1.4 (95% CI 1.2-1.7) in patients on oral drugs. No increased risk of late death or AMI was observed in diet-treated patients with diabetes compared with patients without diabetes. Survival at 10 years without an AMI was 40% in insulin-treated type 2 diabetic patients, 48% if on oral drugs, and 59% if diet managed, compared with 66% in nondiabetic patients.ConclusionType 2 DM requiring insulin treatment or oral antidiabetic drugs is associated with an increased early and long-term risk of death or AMI after CABG, whereas diet-treated patients have a risk similar to that in patients without diabetes.