Reappearance of Cardiac Presynaptic Sympathetic Nerve Terminals in the Transplanted Heart: Correlation Between PET Using 11C- Hydroxyephedrine and Invasively Measured Norepinephrine Release

Previously, sympathetic reinnervation of the transplanted heart has been described using invasive catheterization techniques and noninvasive radionuclide imaging techniques. However, lit-tle is known about the agreement between these 2 methods. Thus, correlation between 11C-hydroxyephedrine (HED) PET and invasively measured norepinephrine (NE) release was in-vestigated in transplant recipients in this study. Methods: Using PET and the catecholamine analog HED, 17 patients were stud-ied between 2 mo and 13.6 y after transplantation. Based on results in completely denervated hearts, areas with HED reten-tion.7%/min were defined as reinnervated. Additionally, trans-cardiac NE release induced by intravenous tyramine (55 mg/kg) was measured by coronary sinus and aortic catheterization within 1 wk of the PET study. NE levels between coronary sinus and aortic root, DNECS–AO, were calculated at baseline and after tyramine administration. Differences of more than 3 SD of base-line (.163 pg/mL) were interpreted as reinnervation. Results: HED retention indicated reinnervation in 10 patients. Maximal HED retention ranged from 4.3%/min to 16.4%/min. DNECS–AO 1 min after tyramine administration ranged between 210 pg/mL and 1157 pg/mL, and 8 patients were above the reinnervation threshold. Fisher’s exact test demonstrated good agreement between results of PET and DNECS–AO measurements (P 5 0.002). Maximal HED retention was also significantly correlated with NE release (r 5 0.69; P 5 0.001). Conclusion: Results of invasively measured NE release and noninvasive 11C-HED PET are well correlated. This study further supports the usefulness of PET as a noninvasive approach for detection of reappearance of catecholamine uptake sites after heart transplantation