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AbstractIntroduction: Moving to clinical validation is an essential phase with every model-based result. However, this translation is often not straightforward because animal models differ from human computer models in many anatomic and electrophysiologic ways, while testing on human subjects in clinical studies is often limited by cost and ethical factors. The present study investigated the translation from computer modeling to experimental testing of an atrial fibrillation (AF) termination algorithm based on rapid septal pacing. Methods: Using a biophysical model of AF based on CT scans from AF patients and atrial membrane kinetics, an algorithm for AF termination was developed: rapid pacing from a ring of electrodes around the septum at 62-70% AF cycle length (AFCL) for 10-30s, followed by stepwise transition to slow pacing at 180% AFCL. This algorithm showed promising results (up to 29% AF termination) during computer simulations. Animal experiments on swine hearts were performed in vitro at the Visible Heart® Laboratory and during in vivo acute experiments. Three septal electrode rings were tested using a transseptal approach: Pulmonary Vein Ablation Catheter®, Multi-Array Septal Catheter® and a decapolar lasso catheter (Biosense Webster). Rapid stimulation was applied simultaneously to 4 electrodes on the ring (Grass S48 Stimulator, FHC Pulsar 6b Pulse Generator). After AF induction using drugs, the extent of AF capture induced by septal pacing was assessed via decapolar mapping catheters in the right and left (coronary sinus) atria. Results: In vitro tests validated the electrode-stimulation system and showed that the lasso catheter was the best electrode ring to implement AF septal pacing. Pacing thresholds were 0.6-1.2V and 1.4-2.3 mA in vivo. The impact of septal pacing on AF was harder to study experimentally due to the difficulty to induce sustained AF and the limited view provided by the mapping catheters compared to computer simulations. Nevertheless, local AF capture could be observed. Conclusion: The results from animal experiments are promising and will serve as a basis for a clinical study on patients undergoing ablation of persistent AF. AF septal pacing could represent an alternative to drugs and catheter-based ablation for some AF patients.