Intermediate Atrial Tachycardia During Persistent Atrial Fibrillation Ablation: A Sub‐analysis of the Extent‐AF Trial

ABSTRACT Background The evidence supporting additional linear ablation for persistent atrial fibrillation (PerAF) remains limited. This study investigates the mechanisms of intermediate atrial tachycardia (AT), a transient state between PerAF and sinus rhythm (SR), during PerAF termination by catheter ablation, and provides evidence for these mechanisms. Methods We analyzed 136 patients who converted to organized AT after PerAF termination in the Extent‐AF study. Bi‐atrial activation mapping combined with entrainment mapping was used to identify the mechanisms and critical isthmus of these ATs. Results A total of 164 ATs were identified in 136 patients (average 1.2 per patient), with 143 (87%) ATs successfully mapped in 113 patients (average 1.3 per patient). The mechanisms of intermediate ATs included macro‐reentry in 110 (77%), micro‐reentry in 21 (15%), and focal AT in 12 (8%). Among the macro‐reentrant ATs, the most common were perimitral ATs (PM‐AT) in 52 (47%), followed by roof‐dependent ATs (RF‐AT) in 40 (36%) and typical atrial flutter (AFL) in 18 (16%). A total of 98 (72%) patients successfully underwent ablation for intermediate ATs. Of these, 88 (90%) required at least one of the perimitral line, roofline, or peritricuspid line to finally restore SR. After 12 months of follow‐up, 63 (64.3%) of the patients with successfully ablated ATs were remained free of arrhythmia. Conclusions The majority of intermediate ATs after PerAF termination were macro‐reentrant ATs. Linear ablation targeting the mitral isthmus, roof, and tricuspid isthmus was crucial for restoring SR in up to 90% of patients, suggesting the importance of additional linear ablation in PerAF ablation. Trial Registration Optimization of intervention strategies for persistent atrial fibrillation: ChiCTR2200060075; chictr.org.cn.