ELECTROPHYSIOLOGICAL EVIDENCE OF REINNERVATION OF THE TRANSPLANTED HUMAN HEART

Beat-by-beat heart rate (HR) changes during exercise were studied in t wo young and fit heart-transplanted humans at different time intervals following transplantation. Upon the start of the exercise, a slow gra dual increase in HR was seen during the early experiments after the tr ansplantation, whereas an immediate rapid increase in HR was observed during the later experiments. From standard ECGs obtained 32 months af ter transplantation, two P waves at somewhat different rates could be identified in both subjects, probably arising from donor and recipient sinoatrial nodes, respectively. The two P wave rate changes during an d following exercise were very similar. We conclude that these changes in the HR pattern and ECG must be due to reinnervation of the donor h earts, most likely by parasympathetic cardiac fibers.