Histological heart lesions resembling myocardial dysplasia in a Guiana Dolphin (Sotalia guianensis) necropsied on the coast of Ceará, Brazil

Myocardial dysplasia, also known as arrhythmogenic right ventricular cardiomyopathy (ARVC), is a degenerative condition characterized by the progressive replacement of the myocardium by fibroadipose tissue, impairing cardiac electrical conduction and predisposing to arrhythmias and sudden death. Although well described in humans and in certain canine breeds, such as Boxers, it is rarely reported in veterinary medicine, especially in marine mammals. This study describes a case in a Guiana dolphin (Sotalia guianensis), stranded on the coast of Ceará, Brazil, which underwent necropsy and histopathological analysis, revealing replacement of myocardial tissue by adipose and fibroadipose tissue in the free wall of the right ventricle, with extension to the subendocardial region, without signs of myocarditis. Despite sampling limitations, the observed lesion pattern is consistent with ARVC-like changes and should be interpreted with caution in light of the possible occurrence of physiological lipomatosis in cetaceans, which has not yet been described in this species. These findings suggest that patterns similar to those observed in other species may occur in cetaceans, contributing to the understanding of cardiac diseases in this group and reinforcing the importance of detailed histopathological evaluation in stranded marine animals. Furthermore, the need for additional studies is highlighted, especially in regions under significant anthropogenic influence.