Biatrial tachycardia utilizing Bachmann bundle

A 69-year-old woman with a history of pulmonary vein isolation for paroxysmal atrial fibrillation (AF) was admitted for recurrence of AF. After reisolation of the left superior pulmonary vein and posterior wall isolation, low-voltage electrograms on the anterior wall were ablated during AF. During the radiofrequency application, AF was organized into biatrial tachycardia (BiAT) (Supplemental Video). The activation map of BiAT showed a counterclockwise circuit using most of the mitral annulus in the left atrium (LA) (including the coronary sinus but not the LA septum) and right atrial (RA) septum with 2 interatrial connections. The postpacing intervals at the RA septum, coronary sinus, LA roof, and lateral mitral annulus were equal to the tachycardia cycle length. Radiofrequency ablation at the LA roof where Bachmann bundle was connected terminated BiAT (blue tag in Supplemental Video). The activation map of the RA during LA appendage pacing showed that the earliest activation site was the ostium of the coronary sinus (Figure 1A). In contrast, the activation map of the LA during sinus rhythm showed that the earliest site was the posterior-inferior LA (Figure 1B). These activation maps indicated that there were no other RA-LA connections except for the coronary sinus and vice versa.