VULNERABLE PLAQUE - RELATION OF CHARACTERISTICS TO DEGREE OF STENOSISIN HUMAN CORONARY-ARTERIES

Background The microanatomic features of the atherosclerotic plaque at risk of disruption include a large lipid core, a high macrophage cont ent, and a thin cap. The relation between lipid core size, plaque size , and cap thickness either with each other or with the degree of steno sis has yet to be evaluated in human coronary arteries. Methods and Re sults Atherosclerotic coronary plaques (n=160) were obtained from 31 s ubjects who died suddenly of ischemic heart disease. In coronary arter ies perfused with formol saline at a pressure of 100 mm Hg, stenosis w as measured by comparison of the minimal lumen size at the site of a p laque with that of the lumen in an adjacent normal segment of artery. Plaque size, the size of the lipid core, and the thickness of the cap were measured in histological sections. Lipid core size ranged from 0% to 82% of overall plaque size. Seventeen percent of plaques had a cor e size of >50%. Linear regression showed no relation of core size to s tenosis (r=.21. Absolute plaque size bore no relation to core size (r= .14). Minimal cap thickness was not related to core size (r=.06). Ten percent of plaques predicted to be angiographically invisible had core s of >50%. Conclusions Two major determinants of plaque vulnerability, core size and cap thickness, are not statistically related. Neither o f these two factors that confer vulnerability are related to absolute plaque size or to the degree of stenosis.