Linear ablation for persistent atrial fibrillation: an evidence-based study

Background Additional linear ablation for persistent atrial fibrillation (PerAF) still has limited evidence-based medical proof. Objectives We probed into the mechanisms of intermediate atrial tachycardia (AT) during PerAF termination by catheter ablation and provided evidence for it. Methods 136 patients who converted to organized AT after PerAF termination in the Extent-AF study were analyzed. Bi-atrial activation mapping combined with entrainment mapping were performed to identify the mechanisms and critical isthmus of these ATs. Results A total of 164 ATs in 136 patients were identified (average 1.2 per patients) and 143 (87%) ATs in 113 patients (average 1.3 per patient) were successfully mapped. The mechanisms of intermediate ATs were 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) 52 (47%), followed by roof dependent ATs (RF-AT) in 40 (36%) and typical atrial flutter (AFL) in 18 (16%). 98 (72%) patients had successfully ablated intermediate ATs. Among these patients, 88 (90%) required at least one of the perimitral line, roofline, or peritricuspid line to finally restore sinus rhythm. At the end of 12 months of follow-up, 63 (64.3%) patients with successful ablative ATs were free of any arrhythmia. Conclusion The majority of intermediate ATs after PerAF termination were macro-reentrant ATs. Linear ablation targets the mitral isthmus, roof, and tricuspid isthmus was a critical step of PerAF ablation to restore sinus rhythm in up to 90% patients, suggesting the importance of additional linear ablation.