Effects of cardiac allograft vasculopathy on myocardial blood flow, vasodilatory capacity, and coronary vasomotion.

Abstract

Coronary vasculopathy is the third leading cause of death 1 year after cardiac allograft transplantation. This study was designed to assess the hemodynamic effects of transplant vasculopathy on myocardial blood flow and vasomotion. Thirty-two patients were studied 1 to 2 years after cardiac transplantation by use of positron emission tomography (n = 32), intravascular ultrasound (n = 26), coronary angiography (n = 32), and endomyocardial biopsy (n = 32). Twenty healthy individuals served as control subjects. Quantitative intravascular ultrasound was used to compute coronary lumen area, intimal thickness, and intimal index [Intima Area/(Intima + Lumen Area)]. Myocardial blood flow was quantified with the use of 13N-ammonia/positron emission tomography. Mean myocardial blood flow was higher in the transplant patients than in control subjects (0.94 +/- 0.26 versus 0.68 +/- 0.16 mL.min-1.g-1 P < .0005). Cold increased myocardial blood flow to 0.79 +/- 0.18 mL.min-1.g-1 in control subjects but not in patients (0.98 +/- 0.36 mL.g-1.min-1). Hyperemic myocardial blood flow was lower in patients than in control subjects (1.69 +/- 0.78 versus 2.30 +/- 0.32 mL.min-1.g-1; P < .05) and was inversely related to maximal intimal thickness and intimal index (all P < .05). The myocardial flow reserve was reduced in patients (1.82 +/- 0.55 versus 3.45 +/- 1.03; P < .0001). The degree of intimal thickening is correlated with abnormalities in coronary function in patients with diffuse cardiac allograft vasculopathy. The reduction in vasodilatory capacity and the abnormal blood flow response to cold suggest abnormalities in endothelium-dependent and -independent coronary vasodilation in transplant recipients.