REDUCED CORONARY FLOW RESERVE DURING EXERCISE IN CARDIAC TRANSPLANT RECIPIENTS

Background Coronary flow reserve (CFR) is reduced in a majority of pat ients after heart transplantation (HTx). Pharmacological interventions , however, provide only limited information on CFR under physiological conditions. Thus, CFR during exercise was evaluated in the present st udy. Methods and Results Coronary angiography was performed at rest an d during supine bicycle exercise in 35 patients early (2 to 3 months; n=10) or late (1 to 6 years; mean, 2.5 years; n=25) after HTx and in 8 controls (C). CFR was determined by parametric imaging after administ ration of 10 mg intracoronary papaverine, during exercise, and after 1 .6 mg sublingual nitroglycerin. Epicardial coronary artery size was me asured by quantitative coronary angiography. CFR after papaverine was normal early (3.6+/-0.5 versus C, 3.6+/-0.7; P=NS) and late (3.8+/-1.3 ; P=NS) after HTx. During exercise, CFR was normal early (3.1+/-0.6 ve rsus C, 3.9+/-0.9; P = NS) but decreased late (2.3+/-0.6; P<.01) after HTx. The increase in coronary cross-sectional area during exercise wa s also diminished late after HTx (14+/-10% versus C, 22+/-10%; P<.05). Both exercise-induced CFR (r=-.39, P<.05) and coronary vasodilation ( r=-.44, P<.01) were inversely correlated with time after HTx. Conclusi ons CFR during exercise is normal early but reduced late after HTx, wh ereas CFR after papaverine administration is maintained. This differen ce between physiological and pharmacological vasodilation suggests pro gressive endothelial dysfunction after HTx.