Impact of Radiofrequency Power Settings on Acute Mitral Isthmus Ablation Success with Concomitant Vein of Marshall Ethanol Infusion

Background.Achieving acute bidirectional block (BB) across the mitral isthmus (MI) remains technically challenging due to the complex architecture of the left atrial inferolateral wall and the presence of epicardial connections via the coronary sinus (CS) and vein of Marshall (VOM).Ethanol infusion into the VOM (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.To assess the impact of two radiofrequency (RF) power strategies (50 W vs. 35 W) on procedural efficacy and safety of mitral isthmus ablation performed with adjunctive vein of Marshall ethanol infusion (VOM-EI) in an exploratory randomized study.Methods.Seventy-one patients planned for left atrial linear ablation for persistent atrial fibrillation (PeAF) were randomly assigned to receive either 50 W (HPSD; n=37) or 35 W (conventional; n=34).VOM-EI was the first step preceding left atrial RF.Procedural metrics, acute MI BB 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; p < 0.002) and total MI applications (17.4 16.4 vs 29.3 23.3, p=0.01) compared with 35 W, without increasing complications.First-pass endocardial mitral isthmus block was achieved in 21/37 (56.8%) patients in the 50 W group and 11/34 (32.4%) in the 35 W group (absolute difference 24.4%; 95% CI 2.1-45.3;p=0.037).Coronary sinus ablation was required less frequently in the 50 W group than in the 35 W group (43.2% vs. 67.6%;absolute difference -24.4%; 95% CI -45.1 to -3.7; p=0.038).Coronary sinus applications when necessary did no differ significantly between 50 W and 35W power (1110 vs 15.5 13; p=0.27).Acute reconnection rates were also comparable between groups (10% vs. 16.6%;absolute difference -6.6%; 95% CI -23.2 to 10.0; p=0.38).Acute mitral isthmus block success rates were comparable between the 50 W and 35 W groups (97.3% vs. 88.2%;absolute risk difference 9.1%; 95% CI -2.9 to 21.1; p = 0.13).Acute reconnection rates were also similar between groups (10% vs. 16.6%;absolute risk difference -6.6%; 95% CI -22.4 to 9.2; p = 0.38).Final mitral isthmus block rates were similar between groups (97.3% vs. 88.2%;absolute difference 9.1%; 95% CI -5.4 to 23.6; p=0.13).Conclusions.In this exploratory randomized study, a 50 W ablation strategy during mitral isthmus 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 mitral isthmus ablation.Larger studies are needed to determine whether these differences translate into improved long-term outcomes.