CFAE software can be used, but CFAE ablation is not guided by the software, but based on visual judgement. Preferably a CFAE map will be made before ablation to judge the sites of most extensive CFAE sites. Baseline mapping in both atria will be performed during AF with the PentaRay multispline catheter sequentially positioned in various regions of the RA and LA. At each location, the catheter will be maintained in a stable position for a minimum of 2.5 s. The operator will look for dispersion areas (electrograms exhibiting both time and spatial dispersion). Where dispersion are found and/or the catheter is not stable for 2.5 s, acquisitions will be repeated.