These two articles demonstrate the intimate relationship between the amount of calcium in the coronaries, as measured with EBCT, and the amount of atherosclerotic plaque as measured by traditional pathologic staining methods. In effect, the calcium score measures the total plaque burden in the artery walls, which is the best predictor of future risk for coronary events.

1. Coronary Artery Calcium Area by Electron Beam Computed Tomography and Coronary Atherosclerotic Plaque Area- A Histopathologic Correlative Study

Methods and Results: 38 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. 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 5 times greater than calcium area. Furthermore, minimal diffuse segmental coronary plaque could be present despite absence of coronary calcium detectable by EBCT.
Conclusions: 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 there is a threshold value for plaque area below which coronary calcium is either absent or not detectable by this methodology.

2. Arterial Calcification and Not Lumen Stenosis Is Highly Correlated With Atherosclerotic Plaque Burden in Humans: A Histologic Study of 723 Coronary Artery Segments Using Nondecalcifying Methodology

Objectives: This study was designed to evaluate whether calcium deposition in the coronary arteries is related to atherosclerotic plaque burden and narrowing of the arterial lumen.
Methods: A total of 37 nondecalcified coronary arteries were processed, sectioned at 3-mm intervals and evaluated by computer planimetry and densitometry.
Results: A significant relation between calcium area and plaque area was found on a per-heart basis (n=13, r=0.87, p<0.0001), per artery basis (left anterior descending: n=13, r=0.89, p <0.0001; left circumflex artery: n=11, r=0.7, p<0.001; right coronary artery: n=13, r=0.89, p<0.0001) and per segment basis (n=723, r=0.52, p<0.0001)….
Conclusions: Coronary calcium quantification is an excellent method for assessing atherosclerotic plaque presence at individual artery sites. Moreover, the amount of calcium correlates with the overall magnitude of atherosclerotic plaque burden.