Sympathetic reinnervation in cardiac transplant recipients: Prevalence, time course and association with long-term survival.

BACKGROUND Partial cardiac sympathetic reinnervation after cardiac transplant has been extensively investigated and evidenced. However, there have been no large-scale, long-term studies evaluating the prevalence, time-course, and association with long-term survival of sympathetic reinnervation of the heart. METHODS Cardiac transplant recipients (n=232) were recruited from outpatient clinic at a single transplant centre in the United Kingdom. Participants were each tested once for the presence of sympathetic reinnervation of the sinus node using the low frequency component of power spectral analysis of heart rate variability, with a cut-off defined as 2 standard deviations above the mean for denervated participants (those tested <56 days post-transplant). Time-course was calculated based on the timing of testing post-transplant. Patients were then followed-up over a period of up to 27 years after transplant for survival analysis. RESULTS The overall prevalence of cardiac sympathetic reinnervation in the 225 patients tested >56 days post-transplant was 64.9%. Sympathetic reinnervation primarily occurred in the first 18 months after transplant, with a plateau thereafter. The prevalence in participants tested >18 months post-transplant was 69.6%. In Kaplan-Meier survival analysis, sympathetic reinnervation was associated with significantly improved survival (Log-rank P=0.019), with a median survival time for reinnervated patients of 19.9 years compared to 14.4 years for the denervated group. CONCLUSIONS Sympathetic reinnervation of the sinus node occurs mostly within 18 months of transplant, is found in 70% of cardiac transplant recipients tested >18 months post-transplant, and is associated with significantly improved long-term survival.