Background and Objectives: Atrial fibrillation (AF) is the most common cardiac arrhythmia, present in up to 14-20% of patients undergoing cardiac surgery, with the number of patients expected to double within the next decade. Despite a Class I recommendation for concomitant surgical ablation and a Class I-B recommendation for left atrial appendage (LAA) occlusion in patients with AF undergoing cardiac surgery (Class IIa for endoscopic or hybrid AF ablation), both procedures remain substantially underutilized in clinical practice. The design of the Mapping atrial fibrillation after Epicardial Surgical Ablation plus AtriClip to Guide Endocardial ablation (MESAGE) prospective study is presented. Materials and Methods: A narrative literature review was conducted using PubMed through March 2025. Randomized controlled trials, multicenter registries, meta-analyses and current clinical guidelines were prioritized. The MESAGE study protocol is presented in accordance with the SPIRIT recommendations. Results: Randomized evidence demonstrates that hybrid ablation achieves 32-48% greater arrhythmia freedom than catheter ablation (CA) alone in persistent and long-standing persistent AF, with comparable safety and significantly fewer interventions at two-year follow-up. Epicardial LAA occlusion with the AtriClip device achieves complete occlusion in all patients with an 87.5% relative reduction in ischemic stroke risk in anticoagulation-free follow-up. Continuous implantable loop recorder (ILR)-based monitoring reveals AF recurrence in substantially more patients than conventional monitoring, with AF burden emerging as a more meaningful endpoint than arrhythmia freedom. The MESAGE study enrolls 40 patients undergoing cardiac surgery who have pre-existing AF, pre-randomized 1:1 to pulmonary vein isolation (PVI) alone versus PVI-BOX, with mandatory pre-operative ILR implantation, intra-operative AtriClip LAA exclusion, and systematic Day-60 endocardial mapping and supplementary ablation using the Affera dual-energy system. Conclusions: Hybrid epicardial-endocardial ablation combined with LAA exclusion and continuous ILR monitoring represents a comprehensive, mechanistically rational and evidence-informed approach to AF management in patients undergoing cardiac surgery, although current evidence remains heterogeneous, and the benefits depend on the AF phenotype and monitoring strategy. The MESAGE pilot study will generate hypothesis-generating prospective comparative data on epicardial PVI versus PVI-BOX in the concomitant surgical setting, assessed through systematic post-surgical endocardial mapping and continuous rhythm monitoring.