[Angioscopic observation of the ruptured plaque cap in a patient with acute myocardial infarction with particular reference to the mechanism of plaque rupture].

A 45-year-old man was admitted with the diagnosis of acute inferior myocardial infarction. After successful thrombolytic therapy, coronary angiography showed TIMI grade 3 flow with the filling defect and haziness on the infarct-related coronary segment. Repeat coronary angiography and coronary angioscopy were performed on the 28th hospital day. Coronary angiography showed 50% stenosis of the luminal diameter of the right coronary artery. Coronary angioscopy showed a white plaque with ruptured cap which occupied one third of the circumferential coronary artery. The torn ends of the cap were longitudinal, and projected into the lumen during the cardiac cycle. Plaque rupture and thrombus formation are important in the pathogenesis of acute coronary syndromes, although the mechanism of plaque rupture is still controversial. The present angioscopic findings seem to support the concept that circumferential tension or mechanical stretch from part of the coronary artery causes the longitudinal fissure at the weakened site of the plaque cap.