Abstract 3126: Coronary Artery Calcification as a Predictor of Subsequent Coronary Artery Disease Events

Abstract

Coronary artery calcification (CAC) as measured by electron beam computed tomography (EBCT) can be used as an indicator of atherosclerotic burden. We have previously reported a cross sectional association between the presence of CAC and history of clinical coronary artery disease (CAD) in type 1 diabetes. In this analysis, we assessed the ability of CAC to predict the incidence of CAD events. Participants from the Pittsburgh Epidemiology of Diabetes Complications Study of childhood onset type 1 diabetes who underwent an EBCT screening (1996–98) and were free of clinical CAD were selected for study (n=236). Mean age at EBCT screening was 36.6 years and diabetes duration 28 years. CAC was calculated using the Agatston score and was used both as a continuous variable (after log transformation) and as a categorical variable. CAD was defined as non-fatal MI (n=4), ischemic ECG changes (Minnesota codes 1.3, 4.1, 4.2, 4.3, 5.1, 5.2, 5.3, 7.1) (n=9), hospitalized unstable angina (n=1), new onset angina leading to revascularization (n=2) or fatal CAD (n=4). Glucose disposal rate (eGDR-insulin sensitivity) was estimated by a regression equation derived from hyperinsulinemic euglycemic clamp studies with terms for waist to hip ratio, HbA 1c , and hypertension. During a mean follow-up of 7.4 years, 20 (8.5%) individuals had an incident event. Individuals who had an event were older, with a greater diabetes duration, systolic blood pressure, HbA 1c , and WBC count, a lower eGDR (all p-values <0.05), and a higher CAC score (p<0.0001). Thus, approximately 24% of persons with CAC ≥200 had a subsequent CAD event compared to only 3% of those with a zero score. In multivariable Cox proportional hazard models with backward elimination, a CAC score greater than zero was a significant predictor of CAD incidence (HR=4.07, 95% CI=1.38–11.96). Other significant predictors comprised diabetes duration (HR=1.07, 95% CI=1.01–1.14) and HbA 1c (HR=1.39, 95% CI=1.10–1.76). The area under the ROC curve increased from 0.720 to 0.784 with the inclusion of CAC score. In this cohort of individuals with type 1 diabetes, CAC is a significant predictor of subsequent CAD status and adds to the prediction beyond standard risk factors. Thus, CAC may be used as a screening tool for CAD risk in type 1 diabetes.