Donor-to-recipient decremental conduction of atrial fibrillation following orthotopic heart transplantation: insights into the mechanism of atrioatrial conduction.

We describe the unique case of a heart transplant patient with type I atrial fibrillation that arose in the donor atrium during a late acute rejection episode and conducted to the recipient atrium with second-degree type I local block. After internal cardioversion, programmed stimulation showed bidirectional decremental conduction across the suture line with nearly equal atrioatrial interval, whereas the recepient atrium showed progressively delayed intra-atrial conduction. These findings strongly suggest that the mechanism of atrioatrial conduction may be electrical propagation along viable myocardium bridging the surgical scar and that the electrophysiologic characteristics of the recipient atrium are involved in decremental conduction across the suture line.