Effects of intracoronary injection of acetylcholine on coronary collateral circulation.

To clarify the effect of intracoronary injection of acetylcholine on coronary collateral circulation, acetylcholine (20 and 50 micrograms) was injected directly into the donor artery of 5 patients with rest angina who had angiographically demonstrable collateral channels. Coronary spasm was defined as severe vasoconstriction (> or = 90% of luminal diameter) with chest pain and/or ischemic ST-segment changes. The intracoronary injection of acetylcholine induced spasm in all the 5 patients. The site of spasm was collateral vessels in 3, and the recipient coronary artery in 2 of the 5 patients. The spasm resolved spontaneously without administration of nitroglycerin. The contralateral intracoronary injection of acetylcholine also induced diffuse coronary spasm in 4 patients. These findings indicate that collateral vessels and recipient coronary arteries of the collateral circulation are susceptible to acetylcholine. Impaired relaxation and vasospastic responses to acetylcholine presumably due to endothelial dysfunction in the collateral and recipient coronary vessels may explain, at least in part, myocardial ischemia in patients with a well-developed collateral circulation.