Coronary artery spasm in the genesis of myocardial ischemia.

Angina pectoris that is mainly caused by coronary artery spasm (coronary spastic angina) has 1 or more of the following characteristics: (1) the attack occurs at rest, (2) the attack is associated with ST-segment elevation on the electrocardiogram (not necessarily so in case of old myocardial infarction), (3) the attack has a variable exercise threshold, and (4) the attack is suppressed by calcium antagonists but not by beta-adrenergic blocking agents. By this criteria, coronary artery spasm is involved in the development of most angina pectoris in patients with 1-vessel disease. The role of coronary artery spasm in the development of acute myocardial infarction is still controversial. However, in this study, injection of nitroglycerin, 0.2 mg, into the totally or subtotally occluded coronary artery either released the occlusion or improved the patency in 13 of the 69 patients (18.8%) with acute transmural myocardial infarction in whom coronary arteriography was performed within 4.0 +/- 1.9 hours of the onset of symptoms. Thus, coronary artery spasm appears to play a role in the production of acute myocardial infarction in these patients.