Complete Isolation of the Left Atrial Posterior Wall (Box Lesion) to Treat Longstanding Persistent Atrial Fibrillation.

INTRODUCTION The left atrial posterior wall has been shown to play na important role in AF pathophysiology. OBJECTIVE Evaluate the efficacy of an ablation strategy designed to completely isolate the LA posterior wall, on top of PV isolation. Methods and Results: 25 pts (72% male age 65 ± 12 years) undergoing AF ablation for persistent or long term persistent AF. Mean AF duration was 11 ± 3 months and mean LA diameter was 4.8 ± 0.4 mm. After complete PVI, a "Roof Line" was created between the top of each contralateral set of lesions and a "floor line" closed the posterior wall in a "Box" fashion, connecting the bottom of each set of contralateral lesions. After an average follow-up of 16 ± 2 months, 20 patients (80%) were free of any atrial arrhythmia recurrences (18 of whom off drugs). Five patients (20%) had sustained atypical flutter and required a new ablation procedure. All these patients had mitral isthmus dependent flutters and no electrical conduction in the PVs or posterior wall were detected. CONCLUSIONS Complete LA posterior wall isolation on top of PV is associated with good outcomes in patients with persistent and long-standing persistent AF when performed using meticulous bidirectional isolation criteria and adenosine infusion. Recurrences occur predominately as perimitral flutter, without gaps in the posterior wall.