Lipomatous hypertrophy of the interatrial septum: a possibly neglected cause of sudden cardiac death

Abstract

An 89-year-old woman was found dead in the corridor of her apartment. A forensic autopsy was requested because her death was sudden and unexpected with an uncertain cause. The woman’s significant past medical history included chronic venous insufficiency of the lower limbs and ischemic heart disease. External examination showed small abrasions of the forehead and chronic ulcers on the lower limbs. Internal examination revealed moderate generalized atherosclerosis, dilation of both cardiac ventricles, congestion of internal organs, and pulmonary edema. Sectioning the heart (weight 570 g, dimensions 14 9 14 9 4 cm) revealed an unencapsulated fatty accumulation within the cardiac interatrial septum with particular sparing of the fossa ovalis (Fig. 1). The interatrial septum was up to 2.5 cm thick. The mass was firm and yellow to brown in color. It had an appearance different to epicardial fat (Figs. 1, 2). The coronary arteries were calcified, but there was no significant stenosis or thrombotic occlusion. There was also no gross myocardial fibrosis or necrosis. Additional autopsy findings included a small leiomyoma on the anterior wall of the uterus and a cyst (4 cm diameter) with clear content on the posterior aspect of the right kidney. Histological examination of the cardiac interatrial septum revealed mature fat with an admixture of brown fat, fibrous tissue, entrapped myocardial fibers, and hypertrophied myocytes with atypical nuclei (Fig. 3). Postmortem toxicological analysis was negative for drugs and alcohol. Death was attributed to a fatal cardiac arrhythmia caused by the fatty accumulation in the cardiac interatrial septum.