Diabetes mellitus: the major risk factor in unstable coronary artery disease even after consideration of the extent of coronary artery disease and benefits of revascularization

OBJECTIVES: This study was designed to study the influence of diabetes on the outcome of unstable coronary artery disease (CAD). BACKGROUND: Diabetes mellitus is a major contributor to CAD. Despite improvement in the management of patients with unstable coronary syndromes, this condition is still linked to a substantially increased mortality and morbidity among diabetic patients. Recent evidence advocates early revascularization in unstable coronary syndromes. Diabetic patients subjected to coronary interventions under stable conditions have a higher risk for complications and a more dismal prognosis than nondiabetic subjects. Accordingly, it is of considerable interest to obtain further information regarding the best possible management of diabetic patients with unstable CAD. METHODS: A total of 2158 patients without and 299 with diabetes mellitus were randomized to an early invasive or a noninvasive strategy. The severity of CAD was expressed as the number and extent of vessel involvement. RESULTS: Three-vessel disease was diagnosed in 42% of diabetic and 31% of nondiabetic patients (p = 0.006). The percentages of patients with ST-depression and troponin-T >0.03 microg/l at admission were comparable among diabetic and nondiabetic patients. Mortality and reinfarction after 12 months were more frequent among diabetic than nondiabetic patients in both treatment groups. Diabetes remained a strong independent predictor for death and myocardial infarction in multivariable analysis. The invasive strategy reduced event rate in nondiabetic patients from 12.0% to 8.9% (odds ratio OR = 0.72; confidence interval CI 0.54 to 0.95; p = 0.019) and in diabetic patients from 29.9% to 20.6% (OR 0.61; CI 0.36 to 1.04; p = 0.066). In a multivariate analysis including the extent of CAD, diabetes remained a strong independent predictor of the combined end point (relative risk RR 2.40; CI 1.47 to 3.91; p = 0.0001) and of mortality (RR 5.43; CI 2.09 to 14.12; p = 0.001). CONCLUSIONS: An invasive strategy improved outcome for both diabetic and nondiabetic patients with unstable CAD. However, diabetes mellitus remained an independent and important risk factor for death and myocardial infarction in the invasive group. Thus, factors beyond the extent of flow-limiting coronary lesions are of considerable importance for outcome in diabetic subjects with unstable coronary syndromes.