Orthotopic heart transplantation: two parts of the heart with two different arrhythmias.

An unusual case of two different types of atrial arrhythmia after orthotopic heart transplantation is reported: a macro-reentrant atrial tachycardia in the recipient atrium, and a common-type, counterclockwise, isthmus-dependent atrial flutter in the donor atrium. The clinical symptoms were caused by atrial flutter arising from the donor atrium. Radiofrequency catheter ablation of the electrically active, donor-derived portion of the cavotricuspid isthmus was performed successfully.