Influence of diabetes mellitus on early and late outcome after coronary artery bypass grafting

Background. Diabetes mellitus is an established independent risk factor for significant morbidity and mortality after coronary artery bypass grafting. Methods. The impact of diabetes on short- and long-term follow-up after coronary artery bypass grafting was studied by comparing the outcomes between 9,920 patients without diabetes mellitus and 2,278 patients with diabetes from 1978 to 1993. Results. Compared with nondiabetic patients, the group with diabetes was older (62 ± 10 years versus 60 ± 10 years), comprised more women (31% versus 19%), had a greater incidence of hypertension (61% versus 44%) and previous myocardial infarction (51% versus 48%), had class III-IV angina more commonly (69% versus 63%), showed a higher incidence of congestive heart failure (11% versus 5%) or triple-vessel or left main disease (60% versus 50%), and had lower ejection fractions (0.54 versus 0.57) (all, p ≤ 0.05). Diabetic patients had a higher incidence of postoperative death (3.9% versus 1.6%) and stroke (2.9% versus 1.4%) (both, p ≤ 0.05), but not Q wave myocardial infarction (1.8% versus 2.9%). Diabetics had lower survival (5 years, 78% versus 88%; 10 years, 50% versus 71%; both, p ≤ 0.05) and lower freedom from percutaneous transluminal coronary angioplasty (5 years, 95% versus 96%; 10 years, 83% versus 86%; latter, p ≤ 0.05), but diabetics did not have lower freedom from either myocardial infarction (5-years, 92% versus 92%; 10-years, 80% versus 84%) or additional coronary artery bypass grafting (5-years, 98% versus 99%; 10-years, 90% versus 91%). Multivariate correlates of long-term mortality were diabetes, older age, reduced ejection fraction, hypertension, congestive heart failure, number of vessels diseased, and urgent or emergent operation. Conclusions. Diabetics have a worse hospital and long-term outcome after coronary artery bypass grafting. The increased risk in such patients can only partially be explained by other demographic characteristics.