Biatrial Macroreentrant Tachycardia Involving Persistent Left Superior Vena Cava and Bachmann's Bundle.

BACKGROUND

Atrial tachycardia after atrial fibrillation ablation may arise from uncommon epicardial conduits.

CASE SUMMARY: A 73-year-old man with persistent atrial fibrillation underwent redo ablation for recurrent atrial tachycardia. Electroanatomic mapping showed durable pulmonary vein and posterior wall isolation with a blocked anterior mitral line. Tachycardia (cycle length: 252 milliseconds) appeared mitral isthmus-dependent, but endocardial ablation only prolonged the cycle without termination. Mapping revealed a macroreentrant biatrial tachycardia incorporating the persistent left superior vena cava (PLSVC) and Bachmann's bundle (BB). Given the central role of the PLSVC, targeted ablation inside the PLSVC terminated the tachycardia and confirmed mitral isthmus block.

DISCUSSION: This rare case illustrates how both the PLSVC and BB can serve as epicardial substrates for biatrial macroreentry, emphasizing comprehensive mapping and tailored ablation in redo procedures.

TAKE-HOME MESSAGES: Recognition of epicardial conduction via PLSVC and BB is essential in redo ablations.