Studies related to atrial fibrillation (AF) have shown that surface lead V₁ reflects mainly the dominant atrial frequency (DAF) of the right atrium (RA), which has been widely used to analyze this arrhythmia. AF organization and fibrillatory (f) waves amplitude are two recently proposed non-invasive AF markers, which have not been yet validated with invasive recordings. In this work, these two non-invasive metrics have been compared with similar measures recorded from two unipolar atrial electrograms (AEGs). Results obtained from 38 patients showed statistically significant correlations between the values measured from surface and invasive recordings, thus corroborating the usefulness of the aforesaid markers in the non-invasive study of AF. Precisely, for AF organization, the correlation coefficients between surface and both AEGs were R = 0.926 (p <; 0.001) and R = 0.932 (p <; 0.001), respectively. For f waves amplitude, slightly lower significant relationships were noticed, the correlation coefficients being R = 0.765 (p <; 0.001) and R = 0.842 (p <; 0.001), respectively. These outcomes together with interesting linear relationships found among the parameters, suggest that AF organization and f waves amplitude can characterize non-invasively the epicardial activity related to AF.