Cardiac ablation is a worldwide accepted minimally invasive procedure to treat Atrial Fibrillation (AF). It consists in creating lesions with a catheter in the cardiac tissue in order to cut off specific electrical pathways. During this project, based on preclinical studies, we investigated and modeled the lesion formation process. This led first to identify and quantify the different mechanisms which take place in the heating process. The model developed gave rise to a Lesion Depth Index to quantify the lesion depth based on clinical parameters used to treat patient: Force Power and Duration. Another part of this project was the analysis of the clinical study EFFICAS 1 focused on the local outcome of the Pulmonary Veins Isolation (PVI). Combining the lesion depth model with the clinical analysis permitted to upgrade the analysis and confirmed that the model developed was relevant for clinical analysis. Moreover, this clinical study, allowed us to discover that the smallest lesion performed in a given microscopic area is a key predictor for isolation defect in PVI. Therefore, we showed that performing transmural ablation at the first shot is essential for a good PVI.