Coronary flow reserve impairment predicts cardiac events in heart transplant patients with preserved left ventricular function

Background The impact of allograft vasculopathy on the coronary circulation and consequently on cardiac outcome may be expressed by coronary flow reserve (CFR) impairment. Therefore, we aimed to evaluate CFR and its relation to cardiac events in heart transplant patients. Methods Twenty-three patients, 2 female, with left ventricular ejection fraction >45% were studied 76±30 months after heart transplantation. They were divided into 2 groups according to coronary angiography: Group A, 10 patients with significant coronary artery disease (stenosis≥50%) and group B, 13 patients without significant stenosis. Twenty healthy subjects, 13 female, served as controls. Coronary flow velocity reserve (CFVR) was assessed by transesophageal echocardiography and calculated as the ratio of maximal (i.v. adenosine, 140 μg/kg/min) to baseline coronary velocities. Patients were followed for a mean of 25 months for cardiac events. Results Compared to controls, heart transplant groups showed significantly higher baseline coronary flow velocities (51±27, 38±12 and 32±12 cm/s, respectively) and lower maximal coronary velocities (90±52, 112±33 and 118±24 cm/s), resulting in a reduced CFVR (1.9±1.0, 3.0±0.5 and 3.8±1.2). Multivariate analysis identified heart transplantation and epicardial coronary artery disease as the only variables independently related to CFVR. Hypertension was positively related to baseline while diabetes inversely related to maximal coronary flow velocities. A CFVR <2.3 was a marker for cardiac events (4 deaths, 1 heart failure). Conclusion CFVR impairment, particularly in the presence of epicardial coronary artery disease, follows heart transplantation and is associated with a worse outcome.