Diabetes mellitus and its impact on long-term outcomes after coronary artery bypass graft surgery

Diabetes mellitus (DM) is an important risk factor for accelerated atherosclerosis and increases cardiovascular disease. Several studies found a higher mortality rate in postoperative diabetic patients than in non-diabetic patients. However, other studies found conflicting evidence on bypass graft dysfunction in patients with diabetes mellitus. We therefore investigated the influence of diabetes mellitus on the long-term outcome after coronary artery bypass surgery (CABG). In this prospective study, 936 consecutive CABG patients were included. These patients were divided into three groups: patients without diabetes mellitus, patients with diabetes mellitus using oral drugs (non-insulin-treated DM) and patients with diabetes mellitus using insulin (insulin-treated DM). The three groups were compared for mortality and (angiographic) bypass graft dysfunction. Of the 936 included patients, 720 (76.8%) patients were non-diabetics, 138 (14.7%) were non-insulin-treated DM, and 78 (8.3%) patients were insulin-treated DM. Follow-up was achieved in all patients, at a mean of 33 months. Mortality was significantly higher in patients with insulin-treated DM, compared with non-insulin-treated DM or non-diabetic patients (P = 0.003). Fourteen (1.5%) patients suffered a myocardial infarction after CABG. A coronary angiography was performed in 77 (8.2%) patients during follow-up, proven bypass graft dysfunction was found in 41 (53.2%) patients. There was no significant difference in bypass graft dysfunction between the three groups. Diabetes mellitus has a significant impact on long-term follow-up after coronary surgery. Particularly insulin dependency is related to an increased mortality. However, diabetes has no influence on angiographically proven bypass graft dysfunction.