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

## TL;DR

A rare case shows how unusual heart structures can cause abnormal heart rhythms after ablation, requiring detailed mapping and targeted treatment.

## Contribution

Highlights the role of persistent left superior vena cava and Bachmann's bundle in biatrial tachycardia after ablation.

## Key findings

- Tachycardia involved the PLSVC and Bachmann's bundle in a post-ablation patient.
- Targeted ablation in the PLSVC terminated the arrhythmia.
- Epicardial substrates like PLSVC and BB are critical in biatrial macroreentry.

## Abstract

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

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.

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.

Recognition of epicardial conduction via PLSVC and BB is essential in redo ablations.