Relation of coronary calcium determined by electron beam computed tomography and lumen narrowing determined by autopsy

Abstract

Coronary calcium determined by electron beam computed tomography (CT) has not been system-atically evaluated regarding prediction of histopathologic atherosclerotic disease. Furthermore, gender specificity has not been examined. The 3 major epicardial arteries were dissected from 13 consecutive hearts (5 women and 8 men) after autopsy. Each artery was straightened and scanned using CT in contiguous 3 mm thick cross sections. After imaging, histologic sections were prepared at corresponding intervals and luminal area obstruction determined by planimetry. Electron beam CT scans were analyzed to determine coronary calcium area (i.e., tomographic area with CT density >130 Hounsfield units). A total of 522 histologic specimens were examined and paired with corresponding CT scans (182 in women, 340 in men). Receiver-operating characteristic (ROC) analysis was used to define site specificity of calcium area for luminal area narrowing by atherosclerosis. ROC curve areas for segmental CT calcium and prediction of atherosclerosis representing mild, moderate, or severe disease were, respectively, 0.712, 0.843, and 0.857 for women and 0.732, 0.793, and 0.841 for men. Curves relating false-positive rate (1-specificity) to predefined degrees of atherosclerotic narrowing versus calcium area were curvelinear. In both women and men, calcium areas on the order of 1 mm 2/coronary segment were necessary to predict at least mild atherosclerosis with a false-positive rate of 0% (i.e., 100% specificity), whereas a calcium area >3 mm 2 was necessary to predict the same result for severe disease. In conclusion, coronary artery calcium area as determined by electron beam CT has the potential to predict segmental histopathologic coronary disease. Increasing coronary calcium areas were associated with increasing likelihood of more advanced atherosclerotic involvement, regardless of patient gender.