Non-complete tissue proximity indication shows perfect concordance with acute isolation gaps: an eight-segment spatial analysis during pulsed field ablation with a variable-loop circular catheter

Background/Purpose Pulsed field ablation (PFA) using a variable-loop circular catheter is an emerging modality for pulmonary vein isolation (PVI). The tissue proximity indicator (TPI) provides real-time feedback on electrode-tissue contact; however, the spatial distribution of non-complete TPI and its relationship to acute isolation gaps have not been systematically evaluated with side-specific analysis. We performed the first segment-level spatial analysis of TPI patterns using a novel eight-segment classification, separately for left and right PVs. Methods In this prospective single-centre study, 14 consecutive patients with atrial fibrillation (AF) underwent PVI using a variable-loop circular PFA catheter. For each ipsilateral PV pair, two ablations were delivered within each PV and six at the antrum encompassing both veins, totalling ten ablations per side. Post-ablation TPI was assessed using the TPI filter on the electroanatomical mapping system. Each PV ostium was divided into eight segments: superior, anterior-superior, anterior-carina, anterior-inferior, inferior, posterior-inferior, posterior-carina, and posterior-superior. TPI was graded as complete, partial, or poor. Voltage mapping identified acute isolation gaps. Left PVs (LPVs; 112 segments) and right PVs (RPVs; 112 segments) were analysed separately. Results Mean age was 69±10 years, 50% were female, and 50% had persistent AF. Procedure and fluoroscopy times were 58±9 and 14±3 min, respectively. Overall complete TPI rates were similar between LPVs and RPVs (94.6% vs 93.8%). However, vulnerability patterns differed markedly: in RPVs, the anterior-superior segment was most frequently non-complete (28.6%), harbouring 3 of 5 RPV gap sites. In LPVs, non-complete TPI was distributed across the superior (14.3%) and anterior-inferior (14.3%) segments. The posterior-carina was vulnerable bilaterally (LPV 7.1%; RPV 14.3%). The inferior and posterior-inferior segments achieved 100% complete TPI in both LPVs and RPVs, with no gaps at these sites. Acute gaps were detected in 4/14 LPVs (5 sites) and 5/14 RPVs (5 sites). Critically, all 10 gap sites across both sides exhibited non-complete TPI (sensitivity 100%), and no gaps occurred where TPI was complete (NPV 100%; p<0.0001 for both). No procedural complications occurred. Conclusions Eight-segment spatial analysis revealed distinct side-specific vulnerability patterns during PFA. The anterior-superior segment of RPVs and the superior and anterior-inferior segments of LPVs were most susceptible to incomplete tissue proximity. Non-complete TPI demonstrated perfect concordance with acute isolation gaps bilaterally, suggesting that segment-level TPI assessment can reliably predict incomplete isolation and guide targeted additional ablation.