Global impedance reduction during pulsed field ablation: Implications for impedance-based procedural feedback

Background Bipolar impedance is increasingly used as procedural feedback during pulsed field ablation (PFA), often to infer catheter–tissue contact. This use assumes that bipolar impedance behaves predominantly as a local contact signal and that its baseline remains stable during the procedure. Objective We evaluated whether impedance changes during PFA remain confined to ablation targets and whether pre-PFA baseline impedance is anatomically uniform. Methods We analyzed 395 consecutive VARIPULSE procedures. Pre- and post-PFA blood-pool reference impedance was compared in 225 paired cases. In a 40-case mapping subset, paired impedance maps were acquired before and after PFA, including crossover-order assessment of contralateral superior pulmonary vein (SPV) impedance before local applications. Regional baseline impedance and post-PFA changes after ablation-zone exclusion were analyzed. Results Blood-pool reference impedance decreased in all 225 paired cases (Δ = −19.7 ± 7.0 Ω, −11.6 ± 3.4%; P < .001). In the mapping subset, non-ablation left atrial surface impedance also decreased in all 40 cases (Δ = −20.7 ± 8.0 Ω, −11.4 ± 3.9%; P < .001), with a similar decrease in the mapping-derived blood-pool reference impedance. Contralateral SPV impedance had already decreased at mid-procedure before local applications, suggesting that the change was not solely attributable to local ablation. Pre-PFA baseline impedance followed the hierarchy intra-PV > PV antrum > non-ablation left atrial surface > blood-pool reference. Conclusion During VARIPULSE-based PFA, bipolar impedance reduction extends beyond direct ablation targets and occurs against a spatially heterogeneous baseline. These findings support context-aware interpretation of bipolar impedance and provide a framework for impedance-based procedural feedback.