Reappearance of cardiac presynaptic sympathetic nerve terminals in the transplanted heart: Correlation between PET using C-11-hydroxyephedrine and invasively measured norepinephrine release

Previously, sympathetic reinnervation of the transplanted heart has been de scribed using invasive catheterization techniques and noninvasive radionucl ide imaging techniques. However, little is known about the agreement betwee n these 2 methods. Thus, correlation between C-11-hydroxyephedrine (HED) PE T and invasively measured norepinephrine (NE) release was investigated in t ransplant recipients in this study. Methods: Using PET and the catecholamin e analog HED, 17 patients were studied between 2 mo and 13.6 y after transp lantation. Based on results in completely denervated hearts, areas with HED retention >7%/min were defined as reinnervated. Additionally, transcardiac NE release induced by intravenous tyramine (55 mug/kg) was measured by cor onary sinus and aortic catheterization within 1 wk of the PET study. NE lev els between coronary sinus and aortic root, Delta NECS-AO, were calculated at baseline and after tyramine administration. Differences of more than 3 S D of baseline (> 163 pg/mL) were interpreted as reinnervation. Results: HED retention indicated reinnervation in 10 patients. Maximal HED retention ra nged from 4.3%/min to 16.4%/min. Delta NECS-AO 1 min after tyramine adminis tration ranged between -10 pg/mL and 1157 pg/mL, and 8 patients were above the reinnervation threshold. Fisher's exact test demonstrated good agreemen t between results of PET and Delta NECS-AO measurements (P = 0.002). Maxima l HED retention was also significantly correlated with NE release (r = 0.69 ; P = 0.001), Conclusion: Results of invasively measured NE release and non invasive C-11-HED PET are well correlated. This study further supports the usefulness of PET as a noninvasive approach for detection of reappearance o f catecholamine uptake sites after heart transplantation.