Abstract Body (Do not enter title and authors here): Introduction: The efficacy of extensive ablation strategies in addition to pulmonary vein (PV) isolation is still controversial in persistent atrial fibrillation (AF) ablation. Gaps in previously ablated lesions can induce arrhythmias, potentially decreasing the effectiveness of extensive ablation.

Purpose: To evaluate the incidence of gaps, gap-related reentry, and subsequent recurrence following redo AF ablation in the EARNEST-PVI trial (NCT03514693).

Methods: The analysis was performed using the extended data of the EARNEST-PVI trial (N=512), a randomized controlled trial evaluating ablation strategies for persistent AF. Patients were randomized 1:1 to either the PVI-plus or PVI-alone group. During a median follow-up of 47 months, 126 (25%) patients underwent redo AF ablation. Among them, we enrolled patients who underwent PVI-alone (N=69), or PVI-plus left atrial (LA) linear ablations (LA roof and mitral isthmus) (N=46) during the index ablation.

Results: In the previous PVI-alone group, electrical PV gaps were observed in 38 (57%) patients. In the previous PVI-plus group, 19 (41%), 10 (22%), and 11 (24%) patients had electrical gaps in the PVs, LA linear lines, or both, respectively. During the redo session, 19 atrial tachycardias (ATs) were observed/induced in 15 patients. ATs were more frequently observed in the PVI-plus group than in the PVI-alone group (23.9% vs. 5.8%, p=0.005). While 7 ATs were not associated with gaps, 2 were related to PV gaps, and 10 were related to gaps in the linear lesions. In the redo AF ablation, PVI was re-completed in all patients, and any induced ATs were eliminated by additional ablation. During a median follow-up of 32 months post-redo, patients with gaps had a lower clinical recurrence rate than those without (44.3 vs. 47.2%, log-rank p=0.033). However, the Cox regression analysis revealed that AF recurrence post-redo was associated only with PV gaps, and not with linear ablation gaps (hazard ratio, 0.57; 95% confidence interval, 0.32–0.99; p = 0.049).

Conclusions: In redo AF ablations, electrical gaps were more prevalent in patients who underwent extensive ablation during the index procedure. While all gaps during redo were potentially arrhythmogenic, PV gaps alone were associated with AF recurrence after redo AF ablation.