Heterotopic heart transplantation (HHT) is useful in the setting of irreversible pulmonary hypertension or donor/recipient size mismatch. The resulting pump is composed of two hearts attached to one another. Autonomic tone can be lost in orthotopic heart transplantation, but HHT is unique in that the donor heart lacks an autonomic nervous supply. This is relevant in terms of increasing cardiac output for example during exercise. We document altered autonomic tone in two of our patients who underwent HHT, and discuss the bearing this has on cardiac function.