Progressive deterioration of coronary flow reserve after heart transplantation

Background: The purpose of this study was to determine coronary flow reserve in cardiac allograft recipients early (0 to 3 years) and late (3 to 7 years) after heart transplantation. Methods and Results: With the use of a Doppler tipped guide wire, coronary flow reserve (ratio of hyperemic to baseline coronary flow velocity) was measured in 82 patients before and after intracoronary adenosine. Forty-five patients were early (≤3 years) after transplantation, 24 were late, and 13 were control patients with single- vessel coronary artery disease. Coronary flow reserve in the early transplantation patients was similar to that in the control group (2.9 ± 0.2 vs 3.0 ± 0.6, p = not significant) but was reduced in the late transplantation group (2.2 ± 0.5 vs 3.0 ± 0.6, p < 0.001). There were differences in coronary flow reserve between the early and late transplantation patient groups (3.0 ± 0.6 vs 2.2 ± 0.5, p < 0.001) despite equally elevated mean arterial pressure, mean heart rate, mean pulmonary capillary wedge pressure, and mean left ventricular mass in the two groups. Coronary flow reserve in patients with angiographic allograft arteriopathy (n = 19) was reduced when compared with coronary flow reserve of patients with normal vessels (n = 50) (1.9 ± 0.3 vs 3.1 ± 0.6, p < 0.001). Conclusions: There is progressive deterioration of coronary flow reserve over time after transplantation. Dysfunction of the coronary microcirculation rather than determinants of myocardial oxygen consumption contributes to this reduction.