Acetylcholine and Endothelial Function

Abstract

To the Editor: Hasdai et al1 reported that myocardial perfusion defects are produced in response to acetylcholine 10−4 mol/L IC. However, acetylcholine has dual effects on coronary artery tone depending on the intracoronary concentration of acetylcholine and the presence of coronary atheroma. In normal coronary arteries, vasodilation, mediated by the endothelial cells, occurs at low concentrations and vasoconstriction, mediated by a direct action on the smooth muscle cells, at higher concentrations. In atheromatous coronary arteries, constriction and dilation occur at low concentration and only constriction occurs at high concentrations of acetylcholine.2 3 We have studied the responses of epicardial coronary arteries to intracoronary infusion of acetylcholine in 15 patients with normal coronary arteriograms, chest pain, and risk factors for coronary artery disease.4 In 53% of patients, there was both constriction and dilation of proximal and distal segments coexisting not only in different coronary arteries but also in different segments of the …