Abstract 4371670: Higher Post-Ablation Scar Shifts Recurrence Towards Flutter

Background: Atrial arrhythmia recurrence remains a common challenge after catheter ablation. While both atrial fibrillation (AF) and atrial flutter (AFL) may recur, the relationship between post-ablation scar burden and the predominant type of arrhythmia recurrence remains incompletely defined. Hypothesis: To evaluate whether higher post-ablation fibrosis burden is associated with a shift in recurrence pattern favoring atrial flutter over atrial fibrillation. Methods: This post hoc analysis included 337 patients from the prospective randomized multicenter DECAAF-II trial who experienced recurrence of atrial arrhythmia after catheter ablation (278 with AF, 59 with AFL). All participants underwent LGE-MRI before and 3 months after ablation to assess left atrial (LA) fibrosis, volume, and post-ablation scar. Baseline demographics as well as the substrates and post-ablation scar burden were compared between AF and AFL recurrence groups using Wilcoxon tests, t-tests, and Chi-square tests accordingly. Results: Baseline atrial substrate was similar between recurrence groups (Table 1). No significant differences were observed in baseline fibrosis (AF: 19.16 ± 7.65% vs. AFL: 19.53 ± 7.83%, p = 0.69), left atrial volume (138.92 ± 42.19 mL vs. 141.74 ± 47.25 mL, p = 0.82), or left atrial volume index (66.81 ± 25.19 vs. 67.40 ± 20.24 mL/m2, p = 0.82). Treatment allocation, demographic factors, and comorbidities were also similar across groups. In contrast, post-ablation scar burden was significantly higher in patients with AFL recurrence (10.46 ± 5.41%) compared to those with AF recurrence (8.75 ± 4.90%, p = 0.015). Conclusion: More scar means less AF and more flutter. Greater post-ablation fibrosis shifts recurrence toward organized rhythms that may be easier to manage clinically.