Coronary Artery Calcium Area by Electron-Beam Computed Tomography and Coronary Atherosclerotic Plaque Area

TLDR

Electron‑beam CT detects coronary calcium, a component of atherosclerotic plaque, but its correlation with luminal narrowing is weak. The study scanned 38 coronary arteries from 13 autopsy hearts with EBCT, defined calcium area as pixels >130 HU, and quantified plaque area in corresponding 3‑mm histological segments to correlate calcium and plaque areas. Plaque area and calcium area were highly correlated, yet plaque area was about five times larger, and small diffuse plaque could exist without detectable calcium, indicating a threshold below which EBCT fails to detect calcium.

Abstract

Coronary calcium identified by electron-beam computed tomography (EBCT) correlates poorly with luminal atherosclerotic narrowing, but calcium, an intimate part of coronary plaque, may be more directly related to atheromatous plaque area.Thirty-eight coronary arteries from 13 autopsy hearts were dissected, straightened, and scanned with EBCT in 3-mm contiguous increments. Coronary calcium area was defined as one or more pixels with a density > 130 Hounsfield units (0.18 mm2/pixel). Each artery was divided into corresponding 3-mm segments, representative histological sections were stained, and atherosclerotic plaque area per segment (mm2) was quantified. Coronary artery calcium and coronary artery plaque areas were correlated for the hearts as a whole, for individual coronary arteries, and for individual coronary artery segments. The sums of histological plaque areas versus the sums of calcium areas were highly correlated for each heart and for each coronary artery. However, coronary plaque area was on the order of five times greater than calcium area. Furthermore, minimal diffuse segmental coronary plaque could be present despite the absence of coronary calcium detectable by EBCT.This histopathologic study confirms an intimate relation between whole heart, coronary artery, and segmental coronary atherosclerotic plaque area and EBCT coronary calcium area but suggests that there is a threshold value for plaque area below which coronary calcium is either absent or not detectable by this methodology.