Cardiomyopathies inflammatoires : diagnostic, corrélations avec l’imagerie, intérêt de la biopsie myocardique et place de la biologie moléculaire

Inflammatory cardiomyopathies, also known as "myocarditis" are inflammatory pathologies affecting the myocardium and characterized by vast etiological and clinical heterogeneity. They can be asymptomatic, particularly in viral forms, or be responsible for sudden death, particularly in subjects under 35 years olds. Due to insufficient sensitivity and specificity of imaging and biology, the gold standard is histopathological and is performed on an endomyocardial biopsy or on explanted heart samples in a transplant context. Their classification has considerably evolved and is now based on the identification of a predominant cell pattern such as lymphocytic, neutrophilic or eosinophilic polynuclear, giant cell or granulomatous myocarditis. These different patterns will guide the etiological diagnosis, prognosis and the therapies to be implemented. Due to the importance of viral etiologies, this morphological analysis must be complemented by a virological analysis based on PCR with viral load quantification. In addition, some authors have been able to demonstrate the occurrence of myocarditis in patients with arrhythmogenic cardiomyopathy of genetic origin. The aim of this chapter is to review the current state of knowledge on inflammatory cardiomyopathies and their management.