INFLUENCE OF TYPE OF SURGERY ON THE OCCURRENCE OF PARASYMPATHETIC REINNERVATION AFTER CARDIAC TRANSPLANTATION

Background-Cardiac autonomic reinnervation after human cardiac transpl antation has been demonstrated frequently but to date only for sympath etic efferents. Standard surgical techniques leave many parasympatheti c branches intact in the original atria and thus with less stimulus to reinnervate the donor atria, Methods and Results-We used changes in t he RR-interval power spectrum induced by sinusoidal modulation of arte rial baroreceptors by neck suction at different frequencies to detect both parasympathetic and sympathetic reinnervation in 79 subjects with ''standard'' and 10 ''bicaval'' heart transplants. In 24 subjects (17 standard and 7 bicaval), the protocol was repeated 6 and 11 months af ter transplantation. Neck suction at 0.20 Hz produced a component at 0 .20 Hz in the RR-interval spectrum not due to respiration (fixed at 0. 25 Hz), which suggested parasympathetic reinnervation, in 4 of 10 bica val but in only 2 of 79 standard transplant subjects (whose recipient atria underwent >50% resection to remove scars of previous interventio ns), P<.001. In only 1 (bicaval) transplant subject was parasympatheti c reinnervation present 6 months after transplantation (confirmed 3 mo nths later); in 4 subjects, it was absent at 6 months but appeared aft er 11 months after transplantation. Atropine (0.04 mg/kg TV) abolished the response to fast (0.20 Hz) and reduced that to slow stimulation, confirming the presence of parasympathetic reinnervation (4 subjects), Conclusions-Parasympathetic reinnervation depends on the surgical tec hnique: because bicaval surgery cuts all sympathetic and parasympathet ic nerves, regeneration might be stimulated similarly in both branches , Standard surgery cuts only approximate to 50% of sympathetic fibers; most recipient parasympathetic axons remain intact, hence their regen eration might not be stimulated.