EPICARDIAL VASOMOTOR RESPONSES TO ACETYLCHOLINE ARE NOT PREDICTED BY CORONARY ATHEROSCLEROSIS AS ASSESSED BY INTRACORONARY ULTRASOUND

Objectives. The purpose of this study was to use intravascular ultraso und to determine the morphologic appearance of the coronary arteries, relating the absence, presence and extent of atherosclerosis to the re sponse of the coronary arteries to acetylcholine infusion. Background. Endothelial function plays a major role in the pathophysiology of myo cardial ischemia and angina pectoris. The response of the coronary art eries to selective infusion of acetylcholine has been used to examine endothelial function, with vasoconstriction occurring in the absence o f intact endothelial function. Vasoconstriction to acetylcholine infus ion in humans without overt coronary artery disease has been attribute d to early atherosclerosis not detected by coronary angiography. Metho ds. Twenty-nine patients without overt coronary artery disease underwe nt selective coronary angiography and selective intracoronary infusion of increasing concentrations of acetylcholine (10(-6), 10(-5) and 10( -4) mol/liter), followed by intravascular ultrasound imaging. Results. The response of the coronary arteries to acetylcholine infusion was n ot dependent on the absence or presence of atherosclerotic plaque, as detected by intravascular ultrasound. The percent change in epicardial coronary artery diameter during acetylcholine infusion versus baselin e was -14 +/- 28% (mean +/- SD) in the seven patients with no visible atherosclerosis on intravascular ultrasound versus -9 +/- 20% in the 2 2 patients with visible atherosclerosis on intravascular ultrasound (p = NS, confidence interval -14% to 25%). There was a greater vasoconst rictive response to acetylcholine infusion in patients with risk facto rs for coronary artery disease than in those without risk factors (p = 0.003). Conclusions. The vasoreactive response to acetylcholine is no t necessarily dependent on ultrasound detection of the presence or abs ence of atherosclerosis.