Epicardial connection between superior vena cava and right atrium contributes to subsequent atrial fibrillation: a case report.

Background: The superior vena cava (SVC) acts as a non-pulmonary vein (PV) trigger for atrial fibrillation (AF) in 2%-6% of patients and harbours 25%-40% of non-PV foci. Approximately 10% of patients with AF have epicardial connections (ECs) between the atrium and PV inside the PV isolation lines, which are associated with AF recurrence. However, the contribution of EC(s) between the SVC and right atrium (RA) to subsequent AF remains unknown. Case summary: A 76-year-old woman underwent ablation for recurrent AF. She had undergone cryo-balloon ablation for paroxysmal AF 3 years previously. After confirming the complete entrance and exit blocks of the four PVs, SVC firing-induced AF was observed. After SVC isolation, the EC between the SVC and RA was observed. No AF was induced after EC ablation. Discussion: Although the mechanisms of ECs in the SVC and RA have not been entirely elucidated, several potential mechanisms have been proposed. (i) Anatomically inherited myofibres/bundles may run through the epicardial side between the SVC and RA. (ii) Epicardial connections between the right PV and the SVC or RA have been recently reported. Thus, we might speculate on the possibility of the existence of EC(s) between the right PV and both the SVC and RA. After cryoablation in the first session, the connection between the SVC and RA remained, which might have acted as EC(s). Thus, physicians should consider the possibility of EC(s) when remaining potentials in the SVC are observed, even though the SVC isolation line seems to be completed.