Histologic characteristics potentially associated with coronary vasospasm in myocardial infarction cases without apparent epicardial coronary culprit stenosis

Background Among cases of sudden cardiac death attributed to acute myocardial infarction, some present without identifiable culprit lesions in the epicardial coronary arteries. Although these cases are clinically presumed to involve coronary vasospasm, the pathological characteristics of the peripheral intramural coronary arteries remain unclear. Purpose We histologically examined the epicardial and peripheral intramyocardial coronary arteries in cases clinically suspected of coronary vasospasm as the cause of sudden death. Methods We analyzed 11 postmortem hearts from sudden death cases clinically suspected to be associated with coronary vasospasm (mean age, 53.8 years; 5 women). Ventricular fibrillation was documented in all cases prior to death, and hemorrhagic myocardial necrosis was observed on cross-sections of the right and left ventricles. Histological evaluation was performed to assess wall thickness and intimal changes in the major epicardial coronary branches (serial sections at 5-mm intervals), as well as in the peripheral intramural coronary arteries at the papillary muscle level on short-axis sections of both ventricles. Results In all hearts, the distribution of myocardial necrosis did not correspond to the territories of the major coronary arteries. Minimal atherosclerotic changes were observed in the major epicardial coronary branches; however, irregular non-eccentric intimal thickening was identified in seven cases. In contrast, markedly thickened arteriolar walls were conspicuous in the peripheral intramural coronary arteries in 9 of 11 hearts. No apparent vascular lesions were observed in one case. Conclusion In hearts without significant atheromatous plaque rupture or massive coronary thromboembolism, intimal thickening of the epicardial coronary arteries and conspicuous wall thickening of the peripheral intramural coronary arteries may represent morphological changes associated with coronary vasospasm shortly before death.