PATHOLOGY OF UNSTABLE PLAQUE - CORRELATION WITH THE CLINICAL SEVERITYOF ACUTE CORONARY SYNDROMES

Objectives. The aim of this study mas to relate the various clinical p resentations of acute coronary syndromes to the underlying plaque morp hology as assessed from histopathologic analysis of plaque fragments o btained by directional coronary atherectomy (DCA). Background. Autopsy studies have shown that unstable angina and infarction are related to plaque instability and involve events such as fissure or rupture of t he fibrous cap, thrombosis and inflammation, The clinical severity and prognosis of acute coronary syndromes can be estimated by the Braunwa ld classification of unstable angina, Whether plaque morphology can be related to the Braunwald classification has not been evaluated. Metho ds. Plaque fragments were obtained by DCA in 75 patients: 38 with unst able angina, 19 with stable angina and 18 with no symptoms after infar ction, The presence of fibrous tissue, thrombus, high cellularity, inf lammatory cells, atheroma, neovessels and ''stellar-shaped'' smooth mu scle cells was evaluated in 7-mu m thick sections by appropriate stain ing, The patients were classified according to clinical presentation w ithout knowledge of the results of pathologic examination, and a plaqu e instability score was assigned, The risk of further cardiac events w as classified as low, medium or high. Results. Increasing severity of the score of unstable angina was associated with increasing prevalence of thrombus, high cellularity, atheroma and neovessels. Plaque from p atients with unstable angina considered to be at low risk of further e vents appeared very similar to that of patients with stable angina, wh ereas the specific morphologic characteristics of plaque instability w ere more frequently observed as the clinical score and the risk of fur ther events increased, After thrombolyzed infarction, plaque morpholog y depends on the delay between the acute event and DCA, Within 1 week after infarction, plaque still showed the morphologic characteristics of instability, whereas late DCA provided samples with morphologic fea tures similar to those observed in patients with stable angina. Conclu sions. The morphologic features of plaque fragments vary at different stages of acute coronary disease. The specific features of plaque inst ability correlate with the clinical scoring system of the Braunwald cl assification. (C) 1997 by the American College of Cardiology.