Morphometric analysis of the composition of coronary arterial plaques in isolated unstable angina pectoris with pain at rest.

Coronary artery plaque morphology was studied in 354 five-mm segments of the 4 major (left main, left anterior descending, left circumflex and right) epicardial coronary arteries in 10 patients with isolated unstable angina pectoris with pain at rest. The 4 major coronary arteries were sectioned at 5-mm intervals and a drawing of each of the resulting 354 Movat-stained histologic sections was analyzed using a computerized morphometry system. The major component of plaque was a combination of dense acellular and cellular fibrous tissue with much smaller portions of plaque being composed of pultaceous debris, calcium, foam cells with and without inflammatory infiltrates and inflammatory infiltrates without foam cells. There were no differences in plaque composition among any of the 4 major epicardial coronary arteries. Plaque composition varied as a function of the degree of luminal narrowing. Linear increases were observed in the mean percent of dense fibrous tissue (from 5 to 50%), calcific deposits (from 1 to 10%), pultaceous debris (from 0 to 10%) and inflammatory infiltrates without significant numbers of foam cells (from 0 to 5%), and a linear decrease was observed in the mean percent of cellular fibrous tissue (from 94 to 22%) in sections narrowed up to 25% to more than 95% in cross-sectional area. Multiluminal channels were seen in all 10 patients (28 [19%] of the 146 sections narrowed greater than 75% in cross-sectional area and in 36 [10%] of all 354 segments); occlusive thrombi in no patient; nonocclusive thrombi in 2 patients (1 section each of 2 arteries); plaque rupture in 2 patients (4 segments from 2 arteries); and plaque hemorrhages in 6 patients (11 sections from 10 arteries).