Po-01-223 epicardial roof-dependent macro-reentrant tachycardia after ablation of atrial fibrillation: prevalence, electrophysiological characteristics, and ablation strategy

Epicardial roof-dependent macro-reentrant tachycardias (epi-RMAT) after catheter ablation of persistent atrial fibrillation are not rare but the prevalence and characteristics remain unclear. To report the prevalence of epicardial conduction in RMATs, and further describe their electrophysiological characteristics and ablation outcome Forty-four consecutive patients with 45 roof-dependent macroreentrant tachycardia (RMAT) after AF ablation were enrolled. High-density mapping and appropriate entrainment were performed to diagnose epi-RMATs. Epi-RMAT was identified in 15 (34.1%) patients. Under the right lateral view, the activation pattern can be briefly classified into 3 types, including clockwise reentry (n=4), counterclockwise reentry (n=9), and biatrial reentry (n=2). Five (33.3%) of them had a 'pseudo focal' activation pattern. All epi-RMATs had continuous slow or no conduction zone with a mean width of 21.3±12.3mm traversing both pulmonary antra, and 9 (60.0%) of them had missing cycle length >10% actual cycle length. Compared with endocardial RMAT (endo-RMAT), epi-RMAT required longer ablation time (9.60±4.98 min vs 3.68±3.42 min, P<0.001), more floor line ablation (85.7% 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(20.0%) with epi-RMATs, while all endo-RMATs were terminated by radiofrequency applications (P=0.032). Posterior wall ablation was performed under esophagus deviation in 2 patients. Among 43 patients with follow-up over 3 months, 2 of 14 patients with epi-RMAT had recurrent tachycardia after a mean follow-up of 9.6±3.7 months, and 7 of 29 patients with endo-RMAT had recurrent tachycardia after a mean follow-up of 13.9±6.1 months (P=0.721 for log-rank). Epi-RMATs are not uncommon in recurrent RMATs 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.