A prospective study of 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 i n 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 infar ction was made as the finding of 2 out of 3 WHO criteria. It occurred spont aneously 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, endocoron ary ultrasonography, an ergometrine provocation test for coronary spasm and a blood coagulation study. Coronary angiography was normal in 4 patients but showed wall changes witho ut stenosis > 50% in 20 patients and one case of aneurysmal arterial diseas e. Intracoronary thrombosis was detected in 6 cases. Endocoronary ultrasono graphy confirmed the normality of the coronary arteries in 2 cases and show ed atheroma in 23 cases (soft atheroma : n = 17 and hard : n = 6). It detec ted 66% of the coronary thrombi observed at angiography and found 3 other c ases. Coronary spasm was authentified in 10 patients (40%). The coagulation study was normal in 19 patients and showed increase in Pai-1 in 5 patients and primary thyrombocytopaenia in one case. The authors conclude that coronary angiographic data is less accurate than endocoronary ultrasonography which best shows the extent and, above all, th e nature of the plaques present in 23 of the cases (92%). Coronary spasm ma y be a contributing factor in 40% of cases, in situ thrombosis in 36% of ca ses despite usually nor mal blood clotting studies. None of these abnormali ties was observed in one case. The embolic cause of infarction was certain in 2 cases.