Local impedance based assessment of lesion effectiveness during pulsed field ablation using a variable-loop circular catheter

Background Local impedance (LI) at the electrode–tissue interface is a promising surrogate of contact quality and lesion effectiveness during pulsed-field ablation (PFA). However, real-world relationships among per-application LI change (ΔLI), a system-derived tissue proximity indication (TPI), and acute pulmonary vein isolation (PVI) outcomes remain insufficiently characterized. Purpose To evaluate whether per-application ΔLI and TPI are associated with (i) first-pass PVI and (ii) gap occurrence, and to compare ΔLI between left- and right-sided pulmonary veins (LPVs vs RPVs). Methods We conducted a single-center observational analysis in adults undergoing PFA-PVI with a variable-loop circular, multielectrode catheter integrated with an electroanatomical mapping system. Electrode-level LI was extracted from procedural video recordings and device logs. Baseline LI was the pre-delivery stable mean immediately before each application. Post-delivery LI was the instantaneous nadir (peak deflection) after energy delivery, without smoothing. For each train within an application (three trains per application), per-train ΔLI was calculated as baseline minus the instantaneous nadir for that train. For each active electrode, the electrode-level ΔLI (per application) was obtained by summing the three per-train ΔLI values. The per-application total ΔLI was then computed as the sum of electrode-level ΔLI across all active electrodes. TPI positivity was determined by the system’s impedance-based proximity criterion at the application level. Endpoints were patient-level first-pass PVI and PV-level presence of a conduction gap. In an exploratory analysis, applications were also categorized by per-application total ΔLI > 40 Ω, and for each pulmonary vein (PV) the count of such applications was compared between PVs with and without a conduction gap. Results Eight patients were analyzed. First-pass PVI was achieved in 5/8 (62.5%); conduction gaps occurred in 3/8 (37.5%), all in the right pulmonary veins. The mean number of applications per procedure was 21± 4. A total of 1,578 active-electrode impedance pairs were analyzed. The mean per-application total ΔLI was 21 ± 20 Ω overall; it was 28 ± 22 Ω in LPVs and 16 ± 17 Ω in RPVs, with a significantly greater ΔLI on the left side (p<0.05). Applications with TPI positivity showed a numerically larger ΔLI than TPI-negative applications, without reaching statistical significance. Among PVs with a conduction gap, the mean count of applications per vein with per-application total ΔLI > 40 Ω was significantly lower than in PVs without a gap (non-gap vs gap: 19.2 ± 3.1 vs 14.0 ± 1.0 per vein, p<0.05). Conclusion Per-application total ΔLI was higher in left- than right-sided pulmonary veins, and all acute gaps occurred on the right. Veins with a gap had fewer applications achieving total ΔLI > 40 Ω, while TPI positivity tracked with larger ΔLI without statistical significance.