Epicardial Roof-Dependent Macro-Re-Entrant Tachycardia After Ablation of Atrial Fibrillation: Electrophysiological Characteristics and Ablation.

Background: Epicardial roof-dependent macro-re-entrant tachycardias (epi-RMAT) after catheter ablation of persistent atrial fibrillation are not rare but the prevalence and characteristics remain unclear.

Objectives: The purpose of this study was to investigate the prevalence, electrophysiological characteristics and ablation strategy of recurrent epi-RMATs after ablation of atrial fibrillation.

Methods: A total of 44 consecutive patients with 45 roof-dependent RMATs after atrial fibrillation ablation were enrolled. High-density mapping and appropriate entrainment were performed to diagnose epi-RMATs.

Results: Epi-RMAT was identified in 15 patients (34.1%). Under the right lateral view, the activation pattern can be briefly classified into clockwise re-entry (n = 4), counterclockwise re-entry (n = 9), and bi-atrial re-entry (n = 2). Five (33.3%) had a pseudofocal activation pattern. All epi-RMATs had continuous slow or no conduction zone with a mean width of 21.3 ± 12.3 mm traversing both pulmonary antra, and 9 (60.0%) had missing cycle length of >10% actual cycle length. Compared with endocardial RMAT (endo-RMAT), epi-RMAT required longer ablation time (9.60 ± 4.98 minutes vs 3.68 ± 3.42 minutes; P < 0.001), more floor line ablation (93.3% vs 6.7%; P < 0.001), and electrogram-guided posterior wall ablation (78.6% vs 3.3%; P < 0.001). Electric cardioversion was required in 3 patients (20.0%) with epi-RMATs, whereas all endo-RMATs were terminated by radiofrequency applications (P = 0.032). Posterior wall ablation was performed under esophagus deviation in 2 patients. We did not observe a significant difference in the recurrence of atrial arrhythmias between patients with epi-RMATs and endo-RMATs after the procedure.

Conclusions: Epi-RMATs are not uncommon after roof or posterior wall ablation. An explicable activation pattern with a conduction obstacle in the dome and appropriate entrainment is critical for the diagnosis. The effectiveness of posterior wall ablation may be restricted by the risk of esophagus impairment.