Enhanced platelet aggregation in the coronary circulation after coronary spasm

A recently developed platelet aggregometer using a laser light scattering method is capable of monitoring the increase in size of small-sized platelet aggregates (diameter 9-25 microm), which cannot be detected with the conventional methods. Whether coronary spasm can cause platelet aggregation in the coronary circulation is unknown. We investigated platelet aggregation, especially small-sized platelet aggregates, simultaneously in the coronary sinus and the aortic root in 18 patients with coronary spastic angina before and after a left coronary artery spasm induced by intracoronary injection of acetylcholine, and in 15 patients with stable exertional angina before and after acute myocardial ischemia induced by rapid right atrial pacing. Platelet aggregation in 12 patients with chest pain syndrome was also examined before and after coronary spasms provoked by acetylcholine. The number of small-sized platelet aggregates increased significantly in the coronary sinus [2.0+/-0.6 x 104 to 4.1+/-1.0 x 104 (V), P<.01] and in the aortic root [1.7+/-0.6 x 104 to 3.2+/-0.6 x 104 (V), P<.05], and the coronary sinus-arterial difference in the number of small-sized platelet aggregates [2.3+/-1.9 x 103 to 1.1+/-0.4 x 104 (V), P<.01] increased significantly after attacks in the coronary spastic angina group, but remained the same in the stable exertional angina group after attacks and in the chest pain syndrome group after the administration of acetylcholine. Therefore, we can conclude that acute myocardial ischemia induced by coronary spasm causes platelet aggregation in the coronary circulation.