Clinical validation of a ≥35% contact index threshold for fixed-loop circular pulsed field ablation

Background Lesion formation during pulsed field ablation (PFA) depends on catheter–tissue distance, yet no clinical parameter directly quantifies this relationship. A three-dimensional electroanatomical mapping system provides a contact index (CI) derived from impedance changes reflecting tissue proximity. The optimal CI threshold for pulmonary vein isolation (PVI) using a fixed-loop circular PFA catheter (FLCC) remains uncertain. In an ex vivo potato tissue model, a CI ≥35% achieved lesion depths comparable to those achieved with radiofrequency catheter ablation. Methods We retrospectively analyzed 135 consecutive patients with atrial fibrillation (91 persistent, 41 paroxysmal) who underwent FLCC-guided PVI between December 2024 and December 2025. One-year atrial arrhythmia recurrence was evaluated using Kaplan–Meier analysis with administrative censoring at 1 year or March 1, 2026. Outcomes before and after CI implementation were compared. In repeat procedures, pulmonary vein reconnection was systematically assessed. Results Overall, 1-year recurrence was 26.5% before CI implementation and 23.4% after implementation. In paroxysmal AF, recurrence decreased from 17.6% (3/17) to 4.2% (1/24), without statistical significance (log-rank p=0.63; Fisher’s p=0.29). Among the four repeat procedures performed after CI implementation, pulmonary vein isolation was preserved in all cases. In one patient, pulmonary vein reconduction was observed at the right pulmonary vein carina, where ablation had been delivered at a CI of 28%. In the remaining three patients, the minimum CI achieved was ≥35%, and no pulmonary vein reconnection was identified. In contrast, pulmonary vein reconnection was documented in 5 of 8 cases of recurrence treated without CI guidance. Conclusion Although CI implementation did not significantly reduce 1-year atrial arrhythmia recurrence, second-session findings suggest that achieving CI ≥35% may contribute to durable pulmonary vein isolation, supporting the clinical relevance of the ex vivo–derived threshold.