Clinical Characteristics and Timing of Accessory Pathway Reconduction During Catheter Ablation of Accessory Pathways.

Background: Catheter ablation of accessory pathways has high acute success rates; however, accessory pathway (AP) recurrence remains a clinically relevant issue. Although intra-procedural AP reconduction is frequently encountered during ablation procedures, its timing, predictors, and clinical significance remain insufficiently characterized. Objectives: This study aimed to investigate the timing, electrophysiologic characteristics, and clinical implications of intra-procedural AP reconduction during catheter ablation of manifest and concealed accessory pathways. Methods: We retrospectively analyzed 128 patients with manifest or concealed AP who underwent catheter ablation at our institution between May 28, 2015, and February 2025. Details of cases in which AP reconduction was observed during the 30 min waiting period after successful ablation, including clinical and procedural characteristics, were compared with those of patients without reconduction. Results: Intra-procedural AP reconduction occurred in 23 patients (18.0%). The mean time to reconduction was 16.7 ± 7.0 min, with a maximum interval of 27 min. Compared with patients without reconduction, those with reconduction had a significantly longer time to pathway interruption, more frequent broad or oblique APs, and more complex procedural approaches requiring multiple anatomical access routes. Intra-procedural reconduction was also associated with subsequent late recurrence. Fifteen of 23 events (65.2%) occurred ≥ 15 min after AP elimination. Conclusions: Intra-procedural AP reconduction during catheter ablation of accessory pathways is not uncommon and appears to be associated with specific electrophysiologic and procedural characteristics as well as late recurrence. These findings may facilitate identification of patients at higher risk of reconduction and help guide intra-procedural assessment during catheter ablation.