Dissociated rhythms between donor and recipient hearts after heart transplantation using the modified bicaval technique.

The modified bicaval anastomosis technique is an orthotopic heart transplantation technique that preserves the posterior wall of the right atrium as a bridging tissue, creating a dual structure of the recipient and donor hearts between the superior and inferior venae cavae. In this report, we present a case with unique electrophysiological findings following heart transplantation using this technique. The patient, who had persistent atrial fibrillation before the procedure, achieved a maintained sinus rhythm afterward. During an episode of cavotricuspid isthmus-dependent atrial flutter in the donor heart, an irregular rhythm suggestive of atrial fibrillation was identified in limited areas of the superior and inferior venae cavae. Atrial flutter ceased after cavotricuspid isthmus ablation; however, atrial fibrillation in the superior and inferior venae cavae persisted. The dissociated rhythms were observed probably because atrial fibrillation may have persisted entirely in the recipient's atrium, and could only be visualized through the superior and inferior venae cavae, which were accessible through the endocardium. Learning objective: When two different atrial arrhythmias occur in the donor and recipient hearts in a patient after heart transplantation using the modified bicaval anastomosis technique, the recipient heart's arrhythmia may persist concurrently with the donor heart's, resulting in a "duplex arrhythmia." Dissociated rhythms could be observed in the separated areas of the right atrium and the superior and inferior venae cavae, which are accessible through the endocardium.