We previously reported the feasibility and efficacy of a simulation-guided clinical catheter ablation of atrial fibrillation (AF) in an in-silico AF model. We developed a highly efficient realistic AF model reflecting the patient endocardial voltage and local conduction and tested its clinical feasibility. We acquired > 500 endocardial bipolar electrograms during right atrial pacing at the beginning of the AF ablation procedures. Based on the clinical bipolar electrograms, we generated simulated voltage maps by applying fibrosis and local activation maps adjusted for the fiber orientation. The software's accuracy (CUVIA2.5) was retrospectively tested in 17 patients and feasibility prospectively in 10 during clinical AF ablation. Results: We found excellent correlations between the clinical and simulated voltage maps (R = 0.933, p < 0.001) and clinical and virtual local conduction (R = 0.958, p < 0.001). The proportion of virtual local fibrosis was 15.4, 22.2, and 36.9% in the paroxysmal AF, persistent AF, and post-pulmonary vein isolation (PVI) states, respectively. The reconstructed virtual bipolar electrogram exhibited a relatively good similarities of morphology to the local clinical bipolar electrogram (R = 0.60 ± 0.08, p < 0.001). Feasibility testing revealed an in situ procedural computing time from the clinical data acquisition to wave-dynamics analyses of 48.2 ± 4.9 min. All virtual analyses were successfully achieved during clinical PVI procedures. We developed a highly efficient, realistic, in situ procedural simulation model reflective of individual anatomy, fiber orientation, fibrosis, and electrophysiology that can be applied during AF ablation. Catheter ablation (CA) is an effective approach for rhythm control management of atrial fibrillation (AF) 1,2. However, the recurrence rate after AF ablation procedures is still substantial 3. Although pulmonary vein isolation (PVI) is a well-established target of AF ablation, extra-pulmonary vein (PV) foci or drivers maintain AF in some patients, and extra-PV foci are more commonly found in AF patients with significant left atrial (LA) remodeling 4,5. The Substrate and Trigger Ablation for Reduction of Atrial Fibrillation trial part 2 (STAR AF2) demonstrated that an empirical extra-PV ablation did not improve the rhythm outcome compared with a circumferential PVI alone in patients with persistent AF (PeAF) 6. However, the one-year recurrence rate was higher than 40% regardless of any additional extra-PV ablation after the PVI, and the outcome of the invasive interventional catheter procedure was not adequate. Therefore, an innovative mapping technology to identify the core target of AF is needed in AF catheter ablation (AFCA). Simulation is a very useful computer-aided method for identifying appropriate intervention targets. We recently reported the feasibility of a simulation-guided PeAF ablation by applying a personalized heart computed tomography (CT) image-integrated AF simulation 7,8. To further this method, we developed a more realistic AF simulation r...