Modified Anatomical Ablation Strategy for Mitral Isthmus

Durable mitral isthmus (MI) block remains challenging in persistent atrial fibrillation (AF) ablation. Ethanol infusion into the vein of Marshall (EI-VOM) enhances efficacy, but the minimal endocardial ablation extent post-EI-VOM is undefined.

This prospective study (June 2024-March 2025) enrolled 35 persistent AF patients undergoing first-time ablation: EI-VOM (11.10 ± 2.24 mL ethanol), bilateral pulmonary vein isolation (PVI), linear ablations, and stepwise MI ablation. Endpoints included acute MI block, lesion requirements, and 6-month sinus rhythm (SR) maintenance.

Left PVI demonstrated significantly shorter ablation time versus right-sided PVI (10.94 ± 5.31 min vs. 18.77 ± 7.27 min, p < 0.01), while acute MI block was achieved in 88.6% (31/35) of patients with 5.03 ± 4.51 endocardial lesions-notably fewer in smaller left atria (diameter <45 mm: 4.1 ± 3.9 vs. ≥45 mm: 6.8 ± 5.1 lesions, p = 0.03). EI-VOM enabled 90% of MI blocks with partial endocardial ablation. SR maintenance reached 91.4% (3-month) and 88.5% (6-month), showing no correlation with MI block or clinical variables (p > 0.05), with zero major complications recorded.

EI-VOM synergizes with partial endocardial ablation for MI block, particularly in non-dilated left atria (<45 mm). Adjunctive coronary sinus ablation is essential for dilated atria. High mid-term SR stability (88.5%) supports strategy efficacy, though non-anatomical factors influence recurrence.