Effects of intracoronary injection of acetylcholine on coronary arterial hemodynamics and diameter

Abstract

To examine the effects of intracoronary injection of acetylcholine on coronary blood flow and on coronary arterial diameter in humans, acetylcholine was injected into the left coronary artery in 32 adult patients (21 men and 11 women with a mean age of 54 years, range 37 to 65) with normal or almost normal coronary arteriographic findings. Patients with angina pectoris, myocardial infarction and severe cardiac diseases were excluded. Temporary right ventricular pacing was set at a rate of 60 beats/min to prevent transient bradyarrhythmias during intracoronary injection of acetylcholine. Measurements of coronary sinus blood flow and coronary vascular resistance and quantification of coronary arterial diameters using a computer-assisted technique were performed before and after each injection of 20, 50 and 100 μg of acetylcholine. Significant increase in coronary sinus blood flow and significant decrease in coronary vascular resistance occurred after intracoronary injection of acetylcholine. In contrast, mean diameter of normal epicardial coronary artery tended to decrease and that of irregular epicardial coronary artery decreased significantly after intracoronary injection of acetylcholine. Intracoronary injection of acetylcholine increases coronary blood flow, suggesting vasodilation in the coronary arteriolar bed, while it induces vasoconstriction in most of epicardial coronary arteries in adult humans.