OBJECTIVE: The vasomotor responses of the epicardial coronary arteries to acetylcholine were examined in patients with normal coronary arteries and chest pain. DESIGN: Quantitative angiography was used to measure minimum lumen diameter of proximal and distal coronary artery segments at baseline, during intracoronary infusion of acetylcholine (10(-7) - 10(-3) mol/l), and following an intracoronary bolus (2 mg) of isosorbide dinitrate. PATIENTS: Coronary arteriograms were obtained in 15 patients (mean (SEM) age 48 (10) years) with normal coronary arteries and chest pain. MAIN RESULTS: In response to the low concentrations of acetylcholine (10(-7) - 10(-6) mol/1) 20 (61%) distal and 11 (41%) proximal segments showed dilatation (group 1), whereas 13 (39%) distal segments and 14 (52%) proximal segments showed constriction (group 2) (P < 0.05 v group 1). In group 1, the maximum dilatation induced by acetylcholine in the proximal and distal segments was 7.83 (1.19)% and 11.6 (2.2)% respectively. In group 2, the maximum constriction at higher concentration was 16.55 (3.3)% and 33.11 (11.63)% in the proximal and distal segments respectively. The two different patterns of the vasomotor response coexisted in eight (53%) of the 15 patients. Intracoronary isosorbide dinitrate caused a greater increase in the coronary luminal diameter of distal segments than in proximal segments in group 1 (25.63 (5.16)% v 12.43 (3.48)%, P < 0.01) but not in group 2 (12.65 (2.53)% v 10.82 (3.33)%. CONCLUSIONS: Constriction and dilatation may occur in proximal and distal coronary artery segments, suggesting local areas of endothelial dysfunction, in response to acetylcholine in patients with chest pain and angiographically normal coronary arteries.
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