Status of the research project: The main complications of arrhythmogenic cardiomyopathies (AC) are sudden death, more rarely heart failure. Recently, data are emerging in favor of an associated role of myocardial inflammation and myocarditis in this pathology, but the impact of inflammation on the presentation and prognosis of the cardiomyopathy, as well as its mechanisms, are not clearly elucidated. To date, endomyocardial biopsy is the gold standard for documenting myocardial inflammation. Aim of the research: To evaluate the interest of a new hybrid PET-MR imaging tool for tissue and metabolic characterization of AC associating MRI and 18F-FDG PET, already used in inflammatory pathologies (cardiac sarcoidosis). Project description: Multicentric observational study of 80 patients with genetic AC undergoing PET-MR. Description of the observed profiles and their impact on the phenotype of the cardiomyopathy and its evolution, study of associated immunological mechanisms, correlation with available anatomopathological data. Expected results and perspectives: first non-invasive description of tissue and metabolic phenotype of AC by PET-MR imaging and its prognostic role, basis for pathophysiological and therapeutic research in case of confirmation of the performances of this imaging for the detection of myocardial inflammation.