Abstract Introduction Effective pulmonary vein isolation (PVI) is the cornerstone of AF ablation, and conduction block from the atrium to the pulmonary veins (PV) is the accepted method to demonstrate it. However, far-field electrograms may make challenging to establish whether PVI has been achieved. Purpose This study aimed to evaluate whether peak frequency (PF) mapping can effectively identify far-field electrograms in the superior PVs following a redo PVI procedure. Methods Left atrium and PV activation and voltage bipolar 3D electroanatomical maps were generated using a steerable catheter with a 16-grid-patterned electrode configuration (HD-Grid) during coronary sinus pacing, both before and after the redo PVI. PF maps were developed offline using specialized experimental software. Only reconnected superior PVs from the redo PVI procedure were included in the analysis. Results Twenty consecutive patients (mean age 63±12 years, 12 male) were prospectively enrolled in the study, with 15 presenting reconnected PVs after the redo PVI. Conduction gaps were identified in the superior PVs of 9 patients (7 in the left superior PV, 5 in the right superior PV). Following the redo PVI, both voltage (0.96±1.1 mV vs. 0.49±1.21, P<0.01) and PF (285±134 vs. 153±112 Hz, P<0.001) were significantly reduced in both superior PVs. This reduction was more prominent in the right superior PV (0.83±0.75 vs. 0.20±0.39 mV, 299±159 vs. 132±116 Hz) than in the left superior PV (1.08±1.32 vs. 0.83±1.67 mV, 272±105 vs. 178±101 Hz). High-voltage (>0.3 mV) electrograms remained prevalent in the right (12%) and left (37%) superior PVs after the redo PVI. However, high PF (>250 Hz) electrograms significantly decreased following PVI in both the right (64% before vs. 6% after PVI) and left (66% before vs. 22% after PVI) PVs. Only a small percentage (5.3% in the right PV and 12% in the left PV) of all electrograms exhibited both high voltage and high PF following the PVI (see figure). Conclusion PF mapping proves to be a valuable tool in distinguishing far-field electrograms from atrial activity in the PVs, offering additional insights to complement voltage mapping, particularly in the context of redo PVI procedures.