Basal hyperinsulinemia beyond a threshold predicts major adverse cardiac events at 1 year after coronary angiogram in type 2 diabetes mellitus: a retrospective cohort study

BACKGROUND: There is a substantial reduction in cardiovascular related morbidity and mortality in the general population attributed to improved treatment of cardiac risk factors and disease, the same magnitude of benefit has not been observed in those with diabetes mellitus. The aim of the present study was to evaluate factors associated with the cardiac outcome at 1 year after coronary angiogram in patients with type 2 diabetes mellitus and to compare the outcomes with nondiabetics. METHODS: A retrospective cohort study was carried out in subjects who underwent coronary angiogram for an evaluation of CAD, with follow-up data available for period of 12 months. The data consisted of 208 type 2 diabetic and 75 non-diabetic patients. Clinical, anthropometric and other biochemical risk factors of the study participants were recorded. Univariate and multivariate cox proportional hazard regression analyses were performed to evaluate the relation between the cardiovascular risk factors and major adverse cardiac events (MACE). RESULTS: At 1 year, MACE was observed in 50 (24.04%) type 2 diabetic subjects, which included non-fatal myocardial infarction 24 (11.54%), target vessel revascularization 15 (7.21%) and death 11 (5.29%). The area under the curve for insulin in predicting MACE was found to be 0.81 (95% CI 0.73-0.88) with sensitivity and specificity of 88% (95% CI 0.71-0.96) and 74% (95% CI 0.65-0.81) respectively. After adjustment for potential confounders hyperinsulinemia (>20 µIU/ml) was significantly associated with MACE [adjusted hazard ratio (HR): 3.03, 95% CI 1.41-6.54, p = 0.005]. Interestingly, the MACE rate in type 2 diabetics with insulin levels <20 µIU/ml (10.2%) and non-diabetics (12%) (p = 0.676) appears to be same. CONCLUSIONS: In addition to severity of the CAD at the baseline, basal hyperinsulinemia beyond a threshold strongly predicts adverse cardiac events at 1 year in type 2 diabetes mellitus. Those below the threshold, appears to be having a risk equivalent to non-diabetics.