Purpose: Intracardiac organization indices (OI) have been used to track the efficiency of stepwise radiofrequency catheter ablation (step-CA) of persistent atrial fibrillation (pers-AF). A better understanding of the components and complexity of AF electrograms (EGMs) is fundamental for tracking the organization of AF. It remains unknown whether ventricular contractions affect the complexity of AF EGMs by means of mechano-eletrical feedback. Our study is aimed at developing new methods to quantify the potential mechano-electrical contribution of ventricular contractions on AF complexity. Methods: During step-CA, a quadripolar catheter was placed into the right atrial appendage (RAA). Robust maximum positive peak detection was applied. The time difference between two adjacent peaks was regularly resampled resulting in the intra-cardiac variability (ICV) signal. ICV reflects the intrinsic atrial activation time variability as well as the potential mechano-electrical feedback of ventricular contractions (VC). A lowpass version impulses series of R wave locations was used as input to an adaptive interference canceller in order to suppress the VC contribution to ICV (VC-ICV). Results: Step-CA (including PVI, CFAE, roof and mitral isthmus lines) terminated 2/3 pers-AF into flutter. The mean contribution of the mechano-electrical feedback on AF complexity achieved 37%. The figure shows a representative example where the VC component (2.03 Hz) has been removed from the ICV, resulting in the atrial-ICV. All other components have been preserved. Conclusions: Our preliminary findings suggest that by means of mechano-electrical feedback, VC contribute up to 37% of the atrial complexity during pers-AF. It is also a first step in the elaboration of new organization indices free of ventricular contribution.