Sympathetic reinnervation demonstrated on serial iodine-123-metaiodobenzylguanidine SPECT images after cardiac transplantation.

The transplanted heart is without autonomic nervous control in the early postsurgical period. We present here a case of cardiac transplantation in which 123I-metaiodobenzylguanidine (MIBG) SPECT and an exercise-loading test were used to monitor the sympathetic reinnervation. The distribution of myocardial 123I-MIBG uptake extended with time from 1 to 2 yr after surgery. However, functional improvement, estimated by the heart rate response to exercise, was not discernable during this period. The findings in this case suggest the feasibility of 123I-MIBG SPECT imaging in the serial monitoring of sympathetic reinnervation after transplantation and that scintigraphic evidence of reinnervation precedes functional recovery.