CORONARY-ARTERY CALCIUM AREA BY ELECTRON-BEAM COMPUTED-TOMOGRAPHY ANDCORONARY ATHEROSCLEROTIC PLAQUE AREA - A HISTOPATHOLOGIC CORRELATIVE STUDY

Background Coronary calcium identified by electron-beam computed tomog raphy (EBCT) correlates poorly with luminal atherosclerotic narrowing, but calcium, an intimate part of coronary plaque, may be more directl y related to atheromatous plaque area. Methods and Results Thirty-eigh t coronary arteries from 13 autopsy hearts were dissected, straightene d, and scanned with EBCT in 3-mm contiguous increments. Coronary calci um area was defined as one or more pixels with a density >130 Hounsfie ld units (0.18 mm(2)/pixel). Each artery was divided into correspondin g 3-mm segments, representative histological sections were stained, an d atherosclerotic plaque area per segment (mm(2)) was quantified. Coro nary artery calcium and coronary artery plaque areas were correlated f or the hearts as a whole, for individual coronary arteries, and for in dividual coronary artery segments. The sums of histological plaque are as versus the sums of calcium areas were highly correlated for each he art and for each coronary artery. However, coronary plaque area was on the order of five times greater than calcium area. Furthermore, minim al diffuse segmental coronary plaque could be present despite the abse nce of coronary calcium detectable by EBCT. Conclusions This histopath ologic study confirms an intimate relation between whole heart, corona ry artery, and segmental coronary atherosclerotic plaque area and EBCT coronary calcium area but suggests that there is a threshold value fo r plaque area below which coronary calcium is either absent or not det ectable by this methodology.