Abstract 4363703: Both electrical isolation and lesion homogeneity should be focused: evidence from repeat atrial fibrillation ablation

Background: Recurrent atrial tachycardia (AT) remains a major challenge following catheter ablation for atrial fibrillation (AF). While pulmonary vein (PV) reconnection is a well-recognized mechanism, the contribution of lesion heterogeneity to iatrogenic AT is not clearly defined. Methods: We analyzed patients who underwent repeat ablation for recurrent AT. Mechanisms of AT recurrence were identified using high-resolution electroanatomic mapping and categorized into six groups. Nonuniform ablation–related AT—considered iatrogenic—was defined as focal or localized reentrant ATs arising from regions of prior ablation characterized by heterogeneous lesion formation. Results: A total of 118 patients who had undergone initial ablation procedures across 31 centers in 17 provinces of China were enrolled. Of these, 52 (44.1%) patients underwent their first ablation at a different institution. All patients subsequently underwent a repeat ablation procedure at Fuwai Hospital. PV reconnection was the most common mechanism of recurrence (39.0%), followed by unclear mechanisms (24.6%) and nonuniform ablation–related AT (14.4%). The number of reconnected PVs was not significantly associated with the timing of recurrence. Nonuniform ablation–related ATs frequently presented as a combination of AF and atrial flutter (AFL), whereas gap-related macro-reentry typically manifested as AFL, and PV reconnection was primarily associated with AF. Conclusion: Lesion homogeneity plays a critical role in minimizing iatrogenic ATs, highlighting the importance of ablation strategies that optimize both electrical isolation and lesion quality. These findings offer valuable insights for the refinement of ablation techniques and the development of improved catheter technologies.