ACETYLCHOLINE-INDUCED CONSTRICTION OF ANGIOGRAPHICALLY NORMAL CORONARY-ARTERIES IS NOT TIME-DEPENDENT IN TRANSPLANT RECIPIENTS - EFFECTS OFSTEPWISE INFUSION AT 1, 6, 12 AND MORE THAN 24 MONTHS AFTER TRANSPLANTATION

Objectives. The aim of this study was to evaluate whether acetylcholin e may be a useful tool for detection of early angiographically undetec table coronary atherosclerosis in heart transplant recipients. Backgro und. Coronary artery disease is the main determinant of long-term prog nosis in transplant recipients. Acetylcholine-induced constriction of angiographically normal coronary arteries in heart transplant recipien ts could be due to early atherosclerosis, and acetylcholine has been p roposed for early detection of coronary artery disease. Methods. The r esponses of large coronary arteries to stepwise intracoronary infusion of acetylcholine (10(-8) to 10(-5) mol/liter) were compared in five c ontrol subjects and in four groups of transplant recipients 1, 6, 12 a nd > 24 months postoperatively (group 1, n = 6; group 2, n = 7; group 3, n = 6; group 4, n = 6, respectively). All patients had normal coron ary arteriographic findings. Vessel dimensions were measured in four s egments in each patient. Results. In control subjects, acetylcholine i ncreased diameters significantly at 10(-8), 10(-7) and 10(-6) mol/lite r (all p < 0.001 vs. basal value). No significant variation was observ ed at 10(-5) mol/liter. Intracoronary isosorbide dinitrate increased d iameters of all segments (p < 0.001). In transplant recipients, vessel diameters did not vary significantly from baseline at 10(-8) and 10(- 7) mol/liter concentrations in groups 1 and 3 and at 10(-8) mol/liter in group 4. Vessels constricted significantly in all the other cases. Comparisons of each group with control subjects showed that responses were significantly different for all concentrations but 10(-8) mol/lit er in groups 3 and 4. Intracoronary isosorbide dinitrate elicited coro nary vasodilation similar to that of control subjects in all groups of transplant recipients. Conclusions. This study indicates that the ace tylcholine response is persistently abnormal in transplant recipients compared with that in normal control subjects and that this abnormalit y may not be related simply to the presence of atherosclerosis. Thus, acetylcholine may not be a useful tool for early detection of coronary atherosclerosis in heart transplant recipients.