Abstract Body (Do not enter title and authors here): Background: The failure to distinguish nearfield and farfield signals is a common reason for ablation failure. Peak frequency (PF) analysis of electrograms is hypothesized to distinguish nearfield from farfield cardiac signals, although in vivo proof is lacking.

Hypothesis: Using electrically isolated pulmonary vein (PV) tissue for analysis, PF will distinguish nearfield from farfield electrograms during atrial fibrillation (AF) ablation, identifying successful PV isolation and validating PF as a predictor of catheter proximity to electrical signals (nearfield versus farfield).

Methods: We created a cohort of twenty patients with paroxysmal AF undergoing wide area circumferential PV isolation between July 2023 and January 2024. Left atrial and PV maps of PF (EnSite OT Near Field, Abbott, Inc) were generated before (Figure A) and after (Figure B) each PV isolation attempt and if dissociated potentials were present. The highest PF in each PV was selected in each PF map. PV electrograms were defined as farfield or nearfield based on the presence or absence of exit and entrance block. PV electrograms of dissociated potentials were considered nearfield. In the first 10 patients, a cutoff value was selected to predict nearfield versus farfield signals. The performance of this cutoff was assessed in the remaining 10 patients. If the PF remained elevated after PV isolation, pacing maneuvers were used to identify the source of the signal.

Results: PF was lower in isolated PVs compared to connected PVs or dissociated potentials within PVs (Figure C). In the derivation cohort, a PF of 300 Hz had 93.2% (95% CI 81.3% - 98.6%) sensitivity and 100% (95% CI 95.0% - 100.0%) specificity for identifying the signal as farfield. In the validation cohort, this cutoff was associated with 90.0% (95% CI 76.3% to 97.2%) sensitivity and 100.0% (95% CI 93.6% to 100.0%) specificity. All farfield signals with a PF over 300 Hz were SVC signals detected in the right superior PV.

Conclusions: PF distinguishes nearfield PV from farfield left atrial signals during AF ablation. PF analysis improves the recognition of PV isolation. Future studies modifying mapping and ablation strategies by utilizing PF as a tool to define nearfield versus farfield should be pursued to improve ablation outcomes.