Impact of radiofrequency power settings on acute mitral isthmus ablation success with concomitant vein of Marshall ethanol infusion.

Background: Achieving acute bidirectional block across the mitral isthmus (MI) remains technically challenging owing to the complex architecture of the left atrial (LA) inferolateral wall and the presence of epicardial connections via the coronary sinus (CS) and vein of Marshall. Ethanol infusion into the vein of Marshall (VOM-EI) has been shown to facilitate acute MI line completion, but the influence of high-power short-duration (HPSD) radiofrequency (RF) settings in this context has not been fully evaluated. Objectives: This study aimed to assess the impact of 2 RF power strategies (50 W vs 35 W) on procedural efficacy and safety of MI ablation performed with adjunctive VOM-EI in an exploratory randomized study. Methods: 71 patients planned for LA linear ablation for persistent atrial fibrillation were randomly assigned to receive either 50 W (HPSD; n = 37) or 35 W (conventional; n = 34). VOM-EI was the first step preceding LA RF. Procedural metrics, acute MI bidirectional block, and safety were analyzed. Results: Mitral RF delivery was performed with an ablation index target of 450-550. HPSD ablation significantly reduced the number of endocardial MI applications (11 ± 7.1 vs 18.8 ± 13; Conclusion: In this exploratory randomized study, a 50-W ablation strategy during MI ablation with adjunctive VOM-EI reduced the number of RF applications and increased first-pass block without increasing complications. These findings suggest that higher-power delivery may improve procedural efficiency during MI ablation. Larger studies are needed to determine whether these differences translate into improved long-term outcomes.