Endothelium-dependent and endothelium-independent vasomotion in large coronary arteries and in the microcirculation after cardiac transplantation.

Endothelium-dependent and endothelium-independent vasodilation of the epicardial conduit vessels and the microcirculatory coronary vessels was investigated with cumulative doses of acetylcholine (ACh 50 micrograms and 100 micrograms i.c.), nitroglycerin (0.3 mg i.c.) and dipyridamole (0.56 mg.kg-1 i.v.) in 17 patients (3 female/14 male; age: 47 +/- 3.6 years) with angiographically normal coronary arteries 40 +/- 5.1 months after cardiac transplantation. The effect of ACh on large conduit arteries was evaluated angiographically. Coronary blood flow velocity changes were measured utilizing an 8F Judkins style 20 MHz Doppler catheter positioned in the left main coronary artery. A coronary flow index was calculated from the mean Doppler flow velocity and the computed cross-sectional vascular area. After 50 micrograms of ACh the diameter of proximal, middle and distal segments of the left anterior descending coronary artery decreased significantly by 7.6 +/- 2.06% (P < 0.05), 10.6 +/- 3.5% (P < 0.01) and 12.6 +/- 3.29% (P < 0.01) and after 100 micrograms ACh by 10.5 +/- 2.4% (P < 0.05), 13.0 +/- 3.7% (P < 0.01) and 15.3 +/- 3.9% (P < 0.01). The endothelium-independent vasodilator nitroglycerin (0.3 mg i.c.) induced an increase in vascular diameter of 14.4 +/- 3.1% (P < 0.01), 18.6 +/- 4.1% (P < 0.01) and 20.8 +/- 2.9% (P < 0.01) in proximal, mid and distal segments of the left anterior descending coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)