Intra-septal radiofrequency ablation within the transseptal puncture hole targeting an interatrial connection during a bi-atrial tachycardia

A 74-year-old man after multiple mitral valve surgeries underwent catheter ablation of a bi-atrial tachycardia (BiAT). Ultra-high resolution activation mapping exhibited a reentrant circuit propagating around the inferior to anterior mitral annulus and right atrial (RA) septum with two interatrial connections. At the transeptal puncture site, continuous fractionated electrograms were recorded during the BiAT, and entrainment pacing revealed a post-pacing interval similar to the tachycardia cycle length, which suggested that the interatrial conduction from the RA to the left atrium (LA) was located just at the transseptal puncture site. A radiofrequency application inside the transseptal puncture hole could successfully eliminate the BiAT. The ablation target for BiATs propagating around the mitral annulus and RA septum is generally the anatomical mitral isthmus (MI). Since the present case had multiple incisions on both the RA and LA septum due to mitral valve surgeries, there was the possibility of the occurrence of a BiAT including the RA and LA septum after performing an MI linear ablation. Therefore, the preferable ablation target for the BiAT in the present case appeared to be the interatrial connection. Ultra-high resolution detailed mapping not only on the atrial endocardium but also in the transseptal puncture hole may be useful for identifying a critical interatrial connection of BiAT circuits.