Atrial fibrillation (AF) is the most common arrhythmia observed in clinical practice. It is responsible for about one third of hospitalizations related to problems of arrhythmia. AF is an important clinical entity due to the increased risk of morbidity and mortality. The consequences of AF most frequently found are hemodynamic function impairment (loss of atrial synchronized contraction, irregular and inadequately rapid ventricular rate), atriogenic thromboembolic events and tachycardia induced atrial and ventricular cardiomyopathy. With the present increase of life expectancy, AF prevalence is expected to double in the next fifty years, in particular in western countries. In collaboration with the Division of Cardiology of CHUV, a catheter ablative protocol mainly based on pulmonary vein isolation (PVI) and complex fractionated elctrograms ablations was defined in order to develop new strategies to decrease procedural time and ablation extent. More precisely, surface EGC as intracardiac electrogram (EGM) signals were recorded from different catheters at specific locations before ablation during and after PVI. The purpose of this project is to evaluate the ability of known (AF cycle length) and new intracardiac organization indices based on recorded surface ECGs and EGM signals to monitor AF organization during stepwise ablation of persistent AF.