[Nosologic frontiers of arrhythmogenic dysplasia. Quantitative variations of normal adipose tissue of the right heart ventricle].

The increasing number of arrhythmogenic idiopathic cardiomyopathies with available histological studies by biopsy or peroperative sampling has prompted the need for data about the normal structure of the right ventricle. A retrospective study of right ventricular tissues was undertaken in 148 autopsies. The quantity of adipose tissue was scored 0 (only epicardial fat visible) to 4 (total replacement of the myocardium by adipose tissue). The topography of the adipocytes was also coded 0 to 4 according to the degree of intermyocytic penetration, irrespective of the total quantify of fat. The amount and extension of adipose tissue in the right ventricular wall was striking. Fifty called "normal" appearances with a myocytic wall of normal thickness and a separate layer of epicardial fat, were only present in 61 of the 148 cases. Adipocytes were present in variable numbers, often unexpectedly high in the majority of cases, with no relationship to the age or gender of the patient with frequent individualization of the myocardial bundles. These surprising findings in normal right ventricles should be born in mind when considering the diagnosis of arrhythmogenic right ventricular dysplasia (ARVD). The histopathological appearances of ARVD are very similar but also differ very significantly, at least in typical cases. The adipocytes are often present in large numbers but this is banal and non-specific. On the other hand, the bundles which penetrate the epicardial fat are usually fibro-muscular and not purely myocytic. In addition, arterioles suggesting segmental diversions are present within the fatty layer with non-specific inflammatory cells.(ABSTRACT TRUNCATED AT 250 WORDS)