Usefulness of topography of coronary calcium by electron-beam computed tomography in predicting the natural history of coronary atherosclerosis

Electron-beam computed tomography (EBCT) allows for accurate noninvasive de tection and quantification of coronary calcium that is representative of un derlying atherosclerotic disease. The present study quantitatively analyzes the topography and establishes the natural history of coronary calcium in patients with variable degrees of coronary atherosclerosis, EBCT was perfor med in 330 consecutive patients aged 56 +/- 12 years (70% men) with recent (<3 months) onset of signs or symptoms of coronary artery disease (CAD) or who were evaluated because of a presumed high risk. Total calcium scores, c omputed by the Agatston method, were positive in 269 patients (82%) (mean a ge 58 +/- 11 years, 73% men). These patients were classified into 4 groups, with total calcium scores ranging between 1 and 30, >30 and 100, > 100 and 400, and >400, respectively. The presence and amount of calcium was additi onally assessed in 10 major segments of the coronary arterial tree, includi ng the major coronary arteries. Of the 72 patients with calcium of only 1 o f the major coronary arteries, the left anterior descending coronary artery was involved in 39 patients (54%) and the right coronary artery in 18 pati ents (25%). Left main stem calcium was observed in only 10 of 139 patients (7%) with 1- or 2-vessel calcium and in 17 of 77 patients (23%) with 3-vess el calcium. Calcium was consistent most frequently in the proximal left ant erior descending coronary artery, followed by the proximal left circumflex and right coronary artery segments. A significant decrease of frequency and amount of calcium from the proximal to distal segments was observed in the left coronary system but not in the right coronary artery, where the distr ibution was more even. With increasing total calcium scores, segmental scor es in the more distal segments were enhanced, but the increase was most pro nounced in the proximal segments and particularly in the proximal left ante rior descending coronary artery. EBCT-derived coronary calcium shows an axi al distribution that appears comparable to that of atherosclerotic lesions observed in pathologic and angiographic studies, highlighting the potential role of EBCT for studying the natural history of CAD. (C)2000 by Excerpta Medica, Inc.