Single-loop bi-atrial tachycardia with presumed conduction block across an anteroseptal mitral ablation line: A case report: Bi-AT after septal mitral isthmus ablation.

A 64-year-old man with no previous medical history underwent catheter ablation (CA) by right pulmonary vein isolation and creation of an anteroseptal mitral isthmus (MI) line for peri-mitral atrial flutter. Since atrial tachycardia (AT) recurred with palpitation 4 months later, a second CA session was performed. Although the differential pacing method appeared to confirm the conduction block across the MI line previously created, single-loop bi-atrial AT (Bi-AT) involving both atria through the septum was induced. When the upper septum of the right atrium was ablated, Bi-AT was terminated. Of note, the time from the onset of the P-wave to activation of the left atrial appendage increased after the ablation compared to before. Learning objective: The anteroseptal mitral isthmus line between the right superior pulmonary vein and the septal mitral annulus is an effective therapy for peri-mitral atrial flutter. However, there are some problems such as difficulty in assessing the bidirectional block of this line and the occurrence of bi-atrial tachycardia via the Bachmann bundle. Further investigation needs to clarify whether conduction block of this interatrial bundle is an appropriate endpoint, as the clinical impacts of conduction delay of left atrial appendage remain uncertain. < The anteroseptal mitral isthmus line between the right superior pulmonary vein and the septal mitral annulus is an effective therapy for peri-mitral atrial flutter However, there are some problems such as difficulty in assessing the bidirectional block of this line and the occurrence of biatrial atrial tachycardia via the Bachmann bundle. Further investigation needs to clarify whether conduction block of this interatrial bundle is an appropriate endpoint as the clinical impacts of conduction delay of left atrial appendage remain uncertain.>.