A rare case of cardiac tumor of the interventricular septum complicated with atrioventricular block

Lipomatous hypertrophy of the interatrial septum is a rare benign condition characterized by adipocyte hyperplasia with fat infiltration between the myocardial fibers in the interatrial septum. Although lipomatous hypertrophy does not occur only in the interatrial septum, its location in the interventricular septum is extremely rare. A 45-year-old woman with no medical or family history of cardiac disease presented with an episode of syncope. Transthoracic echocardiography revealed an echogenic mass in the interventricular septum and no outflow obstruction. The mass-like area showed fat tissue-specific features on computed tomography and magnetic resonance imaging, and furthermore, it showed late gadolinium enhancement. We diagnosed it as lipomatous hypertrophy of the interventricular septum. An implantable loop recorder documented paroxysmal complete atrioventricular block with presyncope. A permanent dual-chamber pacemaker was implanted. This is the first reported case of lipomatous hypertrophy of the interventricular septum treated with a pacemaker for complete atrioventricular block with syncope. We have described the case and the treatment strategy in detail. Learning objective To understand lipomatous hypertrophy, a rare disorder, and its characteristics and differences between lipomatous hypertrophy and cardiac adipose tumors on computed tomography and magnetic resonance imaging. To learn about the appropriate treatment and clinical management of this benign condition and treat symptomatic patients.