Epicardial Roof-Dependent Macro-Re-Entrant Tachycardia After Ablation of Atrial Fibrillation

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.