[Prospective study on the mechanism of myocardial infarction without significant coronary stenosis].

The aim of this study was to evaluate prospectively the respective roles of the atheromatous plaque, coronary spasm and abnormalities of haemostasis in patients with myocardial infarction with normal coronary arteries. The study population included 25 patients (19 men and 6 women) with a mean age of 52.1 +/- 11.1 years (34-76 years). The diagnosis of myocardial infarction was made as the finding of 2 out of 3 WHO criteria. It occurred spontaneously and was transmural in 80% of cases, inferior wall infarction in 9 patients (36%), anterior in 12 (48%) and lateral in 4 patients (16%). All patients underwent investigation on average 10 days after infarction (1-42 days) by coronary angiography with quantitative angiography, endocoronary ultrasonography, an ergometrine provocation test for coronary spasm and a blood coagulation study. Coronary angiography was normal in 4 patients but showed wall changes without stenosis > 50% in 20 patients and one case of aneurysmal arterial disease. Intracoronary thrombosis was detected in 6 cases. Endocoronary ultrasonography confirmed the normality of the coronary arteries in 2 cases and showed atheroma in 23 cases (soft atheroma: n = 17 and hard: n = 6). It detected 66% of the coronary thrombi observed at angiography and found 3 other cases. Coronary spasm was verified in 10 patients (40%). The coagulation study was normal in 19 patients and showed increase in Pai-1 in 5 patients and primary thrombocythemia in one case. The authors conclude that coronary angiographic data is less accurate than endo-coronary ultrasonography which best shows the extent and, above all, the nature of the plaques present in 23 of the cases (92%). Coronary spasm may be a contributing factor in 40% of cases, in situ thrombosis in 36% of cases despite usually normal blood clotting studies. None of these abnormalities was observed in one case. The embolic cause of infarction was certain in 2 cases.