Electron-beam tomography coronary calcium scores are superior to Framingham risk variables for predicting the measured proximal stenosis burden.

ABSTRACT

Previous studies of electron-beam tomography (EBT) have correlated coronary calcium scores with simplistic visual estimates of disease severity. In a clinical trial designed to evaluate 2 treatment strategies in coronary artery disease (CAD) patients with low levels of high-density lipoprotein cholesterol, we used quantitative coronary angiography to measure composite proximal stenosis burden from the baseline coronary angiogram and assessed the traditional Framingham risk variables in 146 patients. Stenosis burden is the sum, per patient, of percent stenosis for the worst lesion found in each of 9 standard proximal coronary segments. EBT estimates of coronary calcium (Agatston score, calcium volume score) were obtained for 115 of these patients. Stenosis burden was correlated with the calcium scores and risk variables. The best traditional correlates of stenosis burden were smoking status (r = 0.31, p = 0.001), prior myocardial infarction (r = 0.24, p = 0.005), body mass index (r = 0.23, p = 0.005), pack-years smoking (r = 0.20, p = 0.05), and age (r = 0.17, p = 0.04). With adjustment for age, all these correlations improved (eg, body mass index x age [r = 0.28, p = 0.001]). In addition, total cholesterol x age (r = 0.22, p = 0.008), fibrinogen x age (r = 0.19, p = 0.03), and systolic blood pressure x age (r = 0.18, p = 0.03) became significant correlates. Spearman correlations of the calcium scores with stenosis burden were considerably greater (Agatston r = 0.62, p <0.0001; calcium volume r = 0.63, p <0.0001). In multivariate regression analysis, calcium score, body mass index, and history of myocardial infarction were independent correlates of stenosis burden (R(2) = 0.45). At a given point in time, the EBT coronary calcium scores are greatly superior to the Framingham risk factors in predicting the measured proximal stenosis burden. Agatston and calcium volume scores are comparably predictive of stenosis burden.