Pathogenesis of unstable angina with 0- or 1-vessel disease. Important role of coronary artery spasm.

In order to examine the possible role of coronary artery spasm in the pathogenesis of unstable angina, provocative testing for coronary spasm was performed in 43 patients with unstable angina who had 0- or 1-vessel disease. Coronary spasm was induced in 20 (65%) of 31 patients by hyperventilation testing (ST increases in 18, ST decreases in 2). Anginal attacks with either ST-segment elevation or ST-segment depression in patients without a significant organic stenosis were induced in 23 (55%) of 42 patients during treadmill exercise testing. Coronary artery spasm, showing severe (> or = 90%) vasoconstriction with angina and/or ischemic electrocardiographic ST-segment deviation, was also documented angiographically in 42 (98%) of 43 patients following intracoronary injection of acetylcholine. We conclude that dynamic coronary obstruction plays an important role in the genesis of attacks in patients with unstable angina who had 0- or 1-vessel organic coronary artery disease.