Serial assessment of sympathetic reinnervation after orthotopic heart transplantation - A longitudinal study using PET and C-11 hydroxyephedrine

Background-Little is known about the progressiveness of sympathetic reinner vation late after cardiac transplantation (HTX). The aim of the present stu dy was to describe individual growth of sympathetic terminals after HTX by a longitudinal quantitative assessment. Methods and Results-In 20 patients after HTX, dynamic PET with C-ll hydroxy ephedrine (HED) was performed twice within 3.0+/-0.5 years. According to th e time interval between HTX and first PET, subgroups of patients early (gro up A, <1.5 years; n=7), intermediate (group B, 1.5 to 7 years; n=7) and lat e (group C, >7 years; n=6) after HTX were defined. At the time of first HED PET, 10 patients were completely denervated (7 in group A, 2 in group B, a nd 1 in group C). Only 3 remained denervated at second PET. A significant i ncrease of reinnervated myocardium between first and second PET was found i n all 3 groups (0% to 9+/-9% of left ventricle for group A, P<0.05; 13+/-12 % to 23+/-17% for group B, P<0.05; 21+/-21% to 37+/-23% for group C, P<0.05 ). The magnitude of increase was similar between groups. Reinnervation was first surveyed in the basal anterior region, then toward apex, septal, and lateral wall. Inferior wall remained denervated. The largest reinnervated a rea surveyed in an individuum was 66% of the left ventricle. Conclusions-The present data confirm the low likelihood of sympathetic rein nervation within Is months after HTX. Once the reinnervation process is ini tiated, a continuous growth is observed even late after HTX, suggesting a p rogressive nature of reinnervation. Reinnervation, however, remained region ally heterogeneous, and a complete restoration was not found until 15 years after HTX.