The increased risk of sudden cardiac arrest (SCA) or sudden cardiac death (SCD) related to vigorous physical activity is well-documented. Currently, for young victims (under 35 years) of SCA/SCD, no etiology is found in 40 to 50% of cases after a standard medical assessment, leading to two important consequences. For the victim's family, it is difficult to understand and accept this tragic event, and the risk of it occurring in another family member is a source of concern. Medically, the absence of a known cause limits the ability to effectively prevent such events. The RESOUDRE study will be a national, prospective, observational registry of young victims (12-35 years) of sports-related SCA/SCD. All cases will undergo the recommended etiological assessment, including autopsy for SCA cases, along with whole exome genetic analysis and toxicological testing. In the event a genetic pathology is identified, a genetic evaluation will be offered to other family members, and appropriate medical care will be provided if necessary. The results of this study could significantly reduce the number of unexplained sport-related SCA/SCD cases and aid in preventing these incidents among affected families.