Left panel: the anatomical areas acquired with the 3d electro-anatomical systems (3d-S). Right panel:A, C and E show the maps acquired by means of the multipolar catheter and 3d-S CARTO 3, while B, D and F show the maps acquired by means of the OC and 3d-S Ensite Precision. A.PA projection. PsAF and dilated LA. Map with 2,520 points acquired in the 0.05-0.5 mV voltage range. The IW presents LV, characterized by small islands of blue/green/redcolors (potential patchy fibrosis) within a larger area of healthy tissue (purple). According to our results, this map could be influenced by the limitations of bipolar recordings.B. AP Projection. PsAF and dilated LA. Map with 28,000 points acquired in the 0.3-0.6 mV voltage range. The entire AW presents LV. A large area of different colors (dashed area) is clearly visible; this is characterized by small islands of normal tissue (purple), separated by probable patchy fibrosis (blue/green/yellow/red) inside the remaining AW; this latter area displays no electrical activity (gray) and is unable to mediate re-entry. C. AP projection. PsAF and non-dilated LA. The entire AW presents LV and is green in color (compatible with dense fibrosis) with only some small islands of healthy tissue (purple) and scar tissue (red), which poorly represent patchy fibrosis. From our point of view, this substrate is unlikely to be able to mediate re-entry. However, this map could also be influenced by the limitations of bipolar recordings D. PA Projection. Paroxysmal AF and non-dilated LA. The PW presents LV that is qualitatively compatible with patchy fibrosis. E. PA Projection. PsAF and dilated LA. The IW presents normal tissue, and the PW a few small islands of LV which are not able to mediate re-entry. F. AP Projection. The same patient as in D. The map shows a prevalence of green and red colors that are more compatible with dense fibrosis and less so with patchy fibrosis, indicating a substrate that is probably unable to mediate re-entry.