Strategies for Recurrent Atrial Fibrillation in Patients Despite Durable Pulmonary Vein Isolation

<b>Background/Objectives</b>: Pulmonary vein isolation (PVI) is the cornerstone in the treatment of atrial fibrillation (AF). Despite initially successful PVI patients experience recurrence of AF potentially due to reconnection of pulmonary veins (PVs). However, a certain number of patients present with recurrent AF, despite durable PVI. The optimal ablation strategy for these patients has yet to be discerned. The aim of this study was to compare outcomes for different ablation strategies for recurrent AF despite persistent PVI. <b>Methods</b>: All redo procedures for the recurrence of atrial fibrillation from March 2018-May 2023 were analyzed. Only patients with proven durable PVI (entrance/exit block and high density (HD) mapping) who received linear ablation or CFAE (complex fractionated atrial electrogram)/low-voltage area ablation were included. Patients were excluded if re-PVI or ablation of atrial tachycardia (AT) was necessary. In all procedures, a 3D-HD map and radiofrequency ablation (RFA) were performed. The ablation strategy was at the operators' discretion. Data from a routinely performed 12-month follow-up were obtained. <b>Results</b>: A total of 847 repeat ablation procedures for atrial arrhythmias were analyzed. In 170 (20.1%) procedures, all PVs were still isolated. Of these, 51 (30.0%) patients were excluded due to AT or because they did not receive further left atrial linear ablation or substrate modification. In total, 119 patients were included in the final analysis, and 71 out of 119 patients (59.7%) were male. The majority (89 patients, 74.8%) suffered from persistent AF. In 72 patients (60.5%), LA-scar (voltage < 0.4 mV) was detectable (81.9% persAF). The ablation strategies were either linear ablation (n = 55), a non-linear substrate modification strategy (CFAE ablation/ablation of low-voltage areas, n = 21) or a combination of both (n = 43). In the Kaplan-Meier analysis, none of the ablation strategies showed a significantly superior outcome. After 370.0 ± 144.9 days, 56.0% (48.1% vs. 61.9% vs. 62.8%, <i>p</i> = 0.3) were free from any arrhythmia. 15.4% vs. 9.5% vs. 9.3% developed an AT (<i>p</i> = 0.3). Left atrial dilatation correlated with recurrence of AF. <b>Conclusions</b>: In patients suffering from a recurrence of AF despite durable pulmonary vein isolation, different substrate modification strategies did not show any superiority for one or the other. Despite the necessity of additional ablation beyond PVI, the optimal ablation strategy has yet to be determined to improve the outcome of redo procedures.