We present a model-based study of therapeutical approaches to atrial fibrillation with a focus on pacing. After a systematic evaluation of different atrial pacing sites, we selected pacing from the septum area and designed a novel septum pacing protocol for atrial fibrillation termination. We then evaluated the performance of septum pacing in different models of atrial fibrillation and investigated the effect atrial substrate (cellular properties, anisotropy and heterogeneities) on the ability to capture during pacing. This study highlight the need for the development of patient-specific algorithms for atrial therapies.