Recipient Atrial Fibrillation Manifesting as an Irregular Monomorphic Atrial Tachycardia in the Donor Heart.

A 63-year-old man presented with a 1-year history of atrial tachycardia (AT) 6 years after orthotopic heart transplantation with bicaval anastomosis. Twelve-lead electrocardiogram showed monomorphic AT with isoelectric intervals across all leads and strikingly irregular PP intervals. At electrophysiology study, the native left atrium's rhythm was atrial fibrillation (AF) while the donor atria exhibited centrifugal activation of irregular cycle length originating from a site along the left atrial anastomosis. Ablation at that site terminated AT to sinus rhythm. Recipient AF with recipient-to-donor conduction should be suspected in the presence of irregular monomorphic AT in orthotopic heart transplantation recipients. Catheter ablation of atrio-atrial conduction is safe and effective.