Computer model-based simulations have shown that rapid stimulation at 60-100% of atrial fibrillation cycle length (AFCL) from a ring of electrodes located around the septum may induce local capture in both atria for most AF dynamics. The present study aims to investigate whether model-based results on AF septal pacing can be translated to experimental simulations. Acute experiments on swine hearts were performed in vivo. The septal ring of electrodes was experimentally implemented using a decapolar lasso catheter placed against the septal wall. Rapid septal pacing was applied in sequences of 10-sec simultaneously on four electrodes on the septal ring. The extent of local AF capture, defined as the ability of the rapid pacing sequence to take control over certain areas of the atria, was assessed via two decapolar mapping catheters in the right and left atrium. AFCL was measured on bipolar electrograms using a nonlinear filtering technique that uses short- and long-term electrogram energies for a robust CL extraction. AFCL was significantly higher in the right atrium compared to the AFCL in left atrium which indicates the existence of different AF dynamics in the two atria. Local capture was observed in both atria when pacing from four electrodes on the septum.