EVIDENCE FOR REGIONAL CATECHOLAMINE UPTAKE AND STORAGE SITES IN THE TRANSPLANTED HUMAN HEART BY POSITRON EMISSION TOMOGRAPHY

Positron emission tomography in combination with the newly introduced catecholamine analogue [C-11]hydroxyephedrine ([C-11]HED) enables the noninvasive delineation of sympathetic nerve terminals of the heart. To address the ongoing controversy over possible reinnervation of the human transplant, 5 healthy control subjects and 11 patients were studied after cardiac transplant by this imaging approach. Regional [C-11]HED retention was compared to regional blood flow as assessed by rubidium-82. Transplant patients were divided into two groups. Group I had recent (< 1 yr, 4.4 +/- 2.3 mo) surgery, while group II patients underwent cardiac transplantation more than 2 yr before imaging (3.5 +/- 1.3 yr). [C-11]HED retention paralleled blood flow in normals, but was homogeneously reduced in group I. In contrast, group II patients revealed heterogeneous [C-11]HED retention, with increased uptake in the proximal anterior and septal wall. Quantitative evaluation of [C-11]HED retention revealed a 70% reduction in group I and 59% reduction in group II patients (P < 0.001). In group II patients, [C-11]HED retention reached 60% of normal in the proximal anterior wall. These data suggest the presence of neuronal tissue in the transplanted human heart, which may reflect regional sympathetic reinnervation.