A novel stepwise catheter ablation method of the mitral isthmus for persistent atrial fibrillation: efficacy and reproducibility

Background: Ethanol infusion of the vein of Marshall (EI-VOM) has been widely used to facilitate mitral isthmus (MI) ablation. According to the literature, the success rate of achieving a bidirectional conduction block across the MI ranges from 51% to 96%, and there is no standardized strategy or method for other cardiac electrophysiologists. Objectives: This study aimed to introduce and evaluate a novel ablation method of MI. Methods: : Consecutive patients with persistent atrial fibrillation (PeAF) that underwent catheter ablation were included. The MI ablation procedure followed a stepwise approach. In step 1, Ethanol infusion of the vein of Marshall (EI-VOM) was performed; in step 2, a "V-shape" endocardial linear ablation connecting the left inferior pulmonary vein (LIPV) to mitral annulus (MA) was performed; in step 3, earliest activation sites(EASs) near the ablation line were identified using activation mapping and reinforced ablation was performed; in step 4, precise epicardial ablation was performed, with the catheter introduced into the coronary sinus(CS) to aim at key ablation targets (KATs). Results: : 135 patients with PeAF underwent catheter ablation. Finally, 119 of them were included in the stepwise ablation method. Bidirectional conduction blocks were achieved in 117 patients (98.3%). The block rates of every step were 0%, 58.0%, 44.0%, and 92.9%, and the cumulative block rates for the four steps were 0%, 58.0%, 76.5%, and 98.3%, respectively. No patient suffered from fatal complications. Conclusions: Our novel stepwise catheter ablation method for MI demonstrated a high bidirectional block rate with high reproducibility.