Comparison of Mitral Isthmus Ablation Strategies after Ethanol Infusion into the Vein of Marshall: Voltage Map-Guided versus Conventional Mitral Isthmus Line Placement

Introduction: Ethanol infusion into the vein of Marshall (VOM-Et) has been introduced as an adjunctive strategy to facilitate mitral isthmus (MI) block. However, the optimal placement of the MI line following VOM-Et remains uncertain, and the clinical efficacy of a voltage map-guided MI line has not been fully assessed. Objective: This study aimed to compare procedural and clinical outcomes between patients who underwent a voltage map-guided MI line after VOM-Et (Group A) and those who received a conventional MI line after VOM-Et (Group B). Methods: A total of 60 patients (mean age 69.1 ± 8.1 years; 37 men) with atrial fibrillation (AF) and/or atrial tachycardia (AT) were retrospectively analyzed. All patients underwent MI ablation following VOM-Et. In Group A (n = 39), the MI line was positioned along low-voltage areas identified post-VOM-Et. In Group B (n = 21), the MI line was placed from the 2–3 o'clock position of the mitral annulus to the left inferior pulmonary vein, irrespective of voltage mapping. Results: The overall acute success rate of MI block was 96.7%, with no significant difference between Groups A and B (94.9% vs. 100%, p = 0.30). Coronary sinus (CS) ablation was necessary in 38.3% of patients, with no difference between groups (38.5% vs. 38.1%, p = 0.98). However, Group A had significantly longer MI lines (41.3 ± 9.7 cm vs. 32.7 ± 7.4 cm, p < 0.01) and required more radiofrequency (RF) lesions (15.9 ± 5.7 vs. 12.6 ± 5.7, p = 0.03). No significant difference was observed in AT/AF recurrence rates between the groups (23.0% vs. 42.0%, p = 0.12). Conclusions: Regarding MI ablation after VOM-Et, the voltage map-guided MI line showed no significant differences compared with the conventional MI line in terms of MI block success, the need for CS ablation, or AT/AF recurrence . However, it was associated with significantly longer MI lines and a greater number of RF lesions, suggesting no clear procedural advantage.