There is currently no correlation between substrate mapping during atrial fibrillation and sinus rhythm. We sought to determine the correlation between the mean voltage recorded during atrial fibrillation and sinus rhythm at different times up to a total duration of 30 seconds. We found that the most accurate correlation between the mean voltage occurred over a period of 10 seconds recording. Although in average the mean voltage during atrial fibrillation is lower than during sinus rhythm this represents the most accurate comparison between voltage mapping during atrial fibrillation and sinus rhythm.