Pulsed-Field Ablation Versus Radiofrequency Ablation Combined Ethanol infusion via the vein of Marshall for Mitral Isthmus Line ablation in Persistent Atrial Fibrillation

BackgroundDurable mitral isthmus (MI) bidirectional block is an important substrate endpoint for persistent atrial fibrillation (PeAF) ablation. Radiofrequency (RF) ablation with adjunctive ethanol infusion via the vein of Marshall (EIVOM) improves epicardial lesion formation and MI block durability; pulsed-field ablation (PFA) is a non-thermal alternative that produces rapid myocardial ablation but its acute lesion durability and gap distribution at the MI are not well defined. We compared acute procedural efficacy, lesion durability after a standardized waiting period, ablation time, gap distribution, and safety between PFA and EIVOM+RF for MI line ablation in PeAF. MethodsIn this prospective, single-center observational cohort, consecutive patients with symptomatic PeAF undergoing first-time catheter ablation with a planned MI line were enrolled. Analyses included 164 patients (PFA, n=56; EIVOM+RF, n=108). Procedures used standardized mapping and pacing criteria to define bidirectional MI block. Study endpoints include acute bidirectional MI block at the end of ablation, immediate block after MI initial ablation, MI reconnection rate after 20 minutes observation period and total MI ablation time. Residual gap locations and peri-procedural complications were also recorded. Between-group comparisons used appropriate univariate tests. ResultsImmediate bidirectional MI block was achieved in 100% of PFA cases versus 97.2% of EIVOM+RF cases (P=0.552). First-pass MI block was significantly higher with PFA (98.2% vs 73.2%; P<0.001). After a 20-minute waiting period, sustained bidirectional block remained in 73.2% of PFA patients versus 89.8% of EIVOM+RF patients (P=0.012). Acute bidirectional MI block at procedure end was 96.4% in PFA group versus 90.7% in EIVOM+RF group (P=0.224). Mean total MI ablation time was markedly shorter with PFA (median 6.1 minutes [IQR 3-8] vs 24 minutes [IQR 16-33]; P<0.001). Residual conduction gaps clustered at the mid-isthmus adjacent to the great cardiac vein in the PFA group (8/13 gaps, 61.5%), whereas gaps in the EIVOM+RF group clustered near the pulmonary vein/ridge region (6/11 gaps, 63.6%). Major complication rates were low and similar between groups (one small self-resolving pericardial effusion in EIVOM+RF; one transient coronary spasm in PFA). ConclusionsIn this prospective cohort of PeAF patients, focal PFA achieved very high acute and first-pass MI block rates and substantially reduced MI ablation time compared with EIVOM+RF but demonstrated greater early reconnection after a 20-minute observation period. The two strategies produced different patterns of residual conduction gaps (PFA: mid-isthmus/GCV; EIVOM+RF: PV-ridge), suggesting modality-specific lesion characteristics. These findings support PFA as an efficient approach to MI line creation but indicate that prolonged observation may be required to secure durable MI block with PFA. Further studies assessing longer-term rhythm outcomes and optimized PFA protocols (including potential hybrid approaches) are warranted.