BACKGROUND Several methods have been proposed to locate the conduction gap on the pulmonary vein isolation (PVI) ablation line. However, the value of the interval of far-field potential (FF potential) and pulmonary vein potential (PV potential) is unknown. METHODS: The state of PV potential and the location of that ablation sites were particularly recorded for analysis once LSPV was isolated in a development cohort of consecutive patients undergoing PVI ablation at a single center. These findings informed the development of a novel algorithm to discriminate the location of a conduction gap between upper portion and inferior portion of LSPV. The performance of this novel algorithm was prospectively tested in a validation cohort of consecutive re-do patients undergoing PVI ablation RESULTS: A total one hundred sixteen patients were recruited, of which 56 formed the validation cohort. Interval of FF potential and PV potential was associated with the location of the conduction gap, and the interval <5 ms predicted that there was a conduction gap in the upper portion of ostium with 92.9% sensitivity and 96.9% specificity. In the prospective evaluation, the interval was able to correctly predict the site of successful ablation in 89.6%. CONCLUSIONS: Interval of far-field potential and pulmonary vein potential is a novel and accurate marker to predict the location of a conduction gap.