Adipositas cordis, fatty infiltration of the right ventricle, and arrhythmogenic right ventricular cardiomyopathy. Just a matter of fat?

Whether fatty infiltration of the right ventricle has to be considered "per se" a sufficient morphologic hallmark of arrhythmogenic right ventricular cardiomyopathy (ARVC) is still a source of controversy; ARVC should be kept distinct from both fatty infiltration of the right ventricle and adipositas cordis. In fact, it is well known that a certain amount of intramyocardial fat is present in the right ventricular antero-lateral and apical regions even in the normal heart and that the epicardial fat increases with increasing body weight. However, both the fibro-fatty and fatty variants of ARVC show, besides fatty replacement of the right ventricular myocardium, degenerative changes of the myocytes and interstitial fibrosis, with or without extensive replacement-type fibrosis. The need to adopt strict diagnostic criteria is warranted not only in the clinical setting but also in the forensic and general pathology arena. When dealing with a case of sudden death, in which the only morphologic finding consists of an increased amount of epicardial or intramyocardial fat, a more convincing arrhythmogenic source such as myocardial inflammatory infiltrates, fibrosis, anomalous pathways, and ion channel disease should always be searched for, in order to avoid an over-diagnosis of ARVC cases.