Influence of radiofrequency power settings on acute mitral isthmus ablation success with concomitant vein of marshall ethanol infusion

Abstract Background Achieving acute durable bidirectional block (BB) across the mitral isthmus (MI) remains technically challenging and ethanol infusion into the VoM (VoM-EI) has been shown to facilitate acute MI line completion. The influence of radiofrequency (RFA) power settings in this context has not been fully evaluated. Objectives To assess the impact of RF power settings (35 vs 50 W) on the acute efficacy of MI ablation performed with adjunctive VoM-EI. Methods In this prospective cohort study, patients undergoing left linear plan ablation (LPA) for persistent atrial fibrillation (PeAF) received VoM-EI followed by RFA along the MI using either 35 W (conventional) or 50 W (high-power, short-duration). Procedural metrics, acute BB and safety were analyzed. Results A total of 66 patients undergoing first-line pulmonary vein isolation (PVI) plus PVI-LPA combined with VoM-EI were included. Baseline characteristics were: age 68 ± 8 years, 18.2% female, CHA2DS2-VASc score 2.5±1.6, left ventricular ejection fraction 57.5±12.1%, left atrial surface area 25.5±4.3 cm², and indexed left atrial volume 50±18 ml/m². Procedure and fluoroscopy times (minutes) were as follows: total procedure 88.7±30 and 9.8±4.7; VoM-EI 12.7±5.8 and 3.8±2.8; and RFA 18±11 and 3.7±2.3, respectively. Randomization to 35 W vs. 50 W yielded no differences in age (68.5±8 vs. 67.7±8 years), CHA2DS2-VASc score (2.6±1.8 vs. 2.4±1.5), ejection fraction (58.2±11.7% vs. 56.8±12.7%), left atrial surface area (25.4±5 vs. 25.4±4 cm²), or indexed left atrial volume (50.2±20.5 vs. 50± 16 ml/m²) (p=ns). Ablation index targets were 500–550 for MI, 420–450 for the anterior wall, and 360–380 for both posterior wall and roof. Mitral isthmus length (39±8 vs. 37±8 mm; p=0.20), LA volume (160±41 vs 161±44 ml; p=0.9) and Marshall low-voltage footprint (8±7.5 vs. 9.3±8%; p=0.50) did not differ between 35 and 50 W groups. High-power ablation significantly reduced the number of endocardial MI applications (11 ± 7.4 vs. 18.5 ± 13.2; p < 0.007) and total MI applications (17.8 ± 17 vs. 28.7 ± 23.4; p < 0.007) compared with 35 W, without increasing complications. Coronary sinus ablation was less frequently required with 50 W (44.1% vs. 65.6%; p = 0.08) to achieve MI block. Acute MI block success rates were comparable between 50 W and 35 W groups (96% vs. 90.6%; p = NS), as were durable block rates (97% vs. 90%; p=0.30) and acute reconnection rates (6.25% vs. 12.5%; p=0.35). No coronary or ethanol-related complications were reported. Conclusions In the setting of VOM ethanol infusion, both 35 W and 50 W RFA achieve high acute and durable mitral isthmus block rates. High-power (50-W) radiofrequency ablation facilitates the rapid achievement of acute mitral isthmus block by generating a steeper thermal gradient and accelerating resistive heating within the target tissue. This results in earlier transmural lesion formation, which is particularly relevant in the context of prior Vein of Marshall ethanol infusion.