Heart failure and enlarged heart in a 10-week-old Oriental shorthair

Abstract

A 10-week-old female Oriental shorthair was referred due to stunted growth, weight loss, dyspnea, and reduced activity levels compared to her littermates. Thoracic radiography revealed a markedly enlarged cardiac silhouette and a diffuse unstructured interstitial pulmonary pattern, presumably due to cardiogenic pulmonary edema. Echocardiography showed marked left- and right-sided ventricular dilation, decreased contractility, and enlargement of both atria, without any identifiable congenital defects. Pleural and peritoneal effusion were also present. Based on these findings, a presumptive diagnosis of both left- and right-sided congestive heart failure due to a dilated cardiomyopathy phenotype was made. Cardiovascular pathological examination confirmed the echocardiographic findings. Additionally, mild interstitial myocardial fibrosis was present in the left ventricle, both atria, the interventricular septum, and, to a minimal extent, in the right ventricle. Moderate endocardial fibrosis was observed in the left atrium and left atrial appendage, while mild endocardial fibrosis was present in the left ventricle. Both antemortem and postmortem evaluations did not provide clear evidence of the underlying cause. Therefore, we consider this a rare case of feline juvenile idiopathic dilated cardiomyopathy with secondary reactive endocardial and myocardial fibrosis.