Pathogenesis of impending myocardial infarction and acute myocardial infarction. Clinical and angiographic evaluation of coronary thrombosis as a precipitating factor.

In order to investigate the role of coronary thrombosis as a precipitating factor of acute myocardial infarction (AMI), we examined coronary angiographic findings in 89 patients with AMI taken within 24 hours of the onset and in 42 patients with prolonged angina attack of impending myocardial infarction (impending MI) taken within 50 hours of the last angina attack. Furthermore, in the patients with impending MI, the effects of intracoronary and intravenous thrombolytic therapy and anticoagulant therapy used to prevent impending MI from developing into AMI, were also studied. (1) In 72 of 89 patients (81%) with AMI, coronary thrombi were detected angiographically. The thrombi were detected most frequently (88%) in angiographs taken within 3 hours of onset. (2) In 23 of 42 patients with impending MI, coronary thrombi were detected angiographically. In 6 patients with coronary thrombi who underwent intracoronary thrombolysis during angina attack, occlusive coronary thrombi in ischemia-related vessels were the observed, and recanalization by thrombolysis with intracoronary urokinase infusion relieved chest pain and improved ECG changes. (3) The incidence of AMI in 42 patients with impending MI who were treated with intracoronary and intravenous thrombolytic therapy and anticoagulant therapy was significantly less than in the conventional therapy group (80 patients) (11.9% vs. 27.5%; p less than 0.05). In 4 of 5 patients with developing AMI, coronary thrombi were detected angiographically in the acute phase of impending MI. These results indicate that coronary thrombosis plays an important role not only in the precipitation of impending MI but also in the development of impending MI to AMI.