Bipolar Local Impedance Delta as a Quantitative Index of Catheter–Tissue Energy Coupling During Pulsed-Field Ablation
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Background
Pulsed-field ablation (PFA) systems increasingly provide impedance-based contact indicators, such as tissue proximity indication (TPI), derived from local impedance changes relative to a blood-pool baseline. These indicators are largely binary and do not quantify post-application catheter–tissue energy coupling. We evaluated Bipolar Local Impedance Delta (BiLID), the peri-application bipolar local impedance drop, as a complementary impedance-based index of delivered energy coupling.
Methods
We retrospectively analyzed 1,556 VARIPULSE applications in 23 patients undergoing pulmonary vein isolation. BiLID was derived from 29,822 paired pre-/post-ablation impedance measurements obtained from numeric local impedance readouts displayed by the mapping system, without proprietary data export or waveform estimation. Reproducibility was assessed by intraclass correlation. Associations with TPI status, vein anatomy, application order, and peak creatine kinase-MB (CK-MB) were examined using linear mixed-effects models with within-patient clustering and exploratory patient-level analyses.
Results
BiLID showed excellent interobserver reproducibility and increased stepwise with the number of TPI-positive electrodes per pair (0–2; P < 0.0001), while varying widely among TPI-positive signals. BiLID differed by electrode position and was lower during right than left pulmonary vein ablation (both P < 0.0001). Total BiLID correlated with peak CK-MB (r = 0.71; 95% CI, 0.42–0.87; P = 0.0001), whereas application count (r = 0.16, P = 0.4711) and TPI-positive signals (r = 0.26, P = 0.2334) did not. Lower CK-MB elevation was associated with larger left atrial volume index, female sex, and heart failure, suggesting substrate-modulated biomarker release.
Conclusions
BiLID is a reproducible, continuous index of catheter–tissue energy coupling that complements pre-delivery binary contact indicators by quantifying the response after PFA delivery. It captures graded contact quality and anatomical heterogeneity and may inform individualized, coupling-guided PFA titration.
Clinical Perspective
What is Known
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Pulsed-field ablation procedures currently rely largely on cumulative application counts and binary contact-assessment tools such as tissue proximity indication to guide lesion delivery.
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Binary proximity indicators provide useful information on catheter–tissue contact but do not quantify the quality or efficiency of energy coupling during each application.
What the Study Adds
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Bipolar Local Impedance Delta (BiLID), an offline-derived continuous index based on peri-application bipolar local impedance drop, increased stepwise with the number of TPI-positive electrodes and captured variation not represented by binary TPI alone.
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BiLID showed systematic anatomical heterogeneity, with lower values during right pulmonary vein ablation, and correlated with peak CK-MB more strongly than application count or TPI-positive signals.
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Systemic biomarker release was influenced by atrial substrate factors, suggesting that procedural coupling metrics and biomarkers provide complementary information relevant to future individualized PFA titration.
