Lipomatous hypertrophy of the interatrial septum presenting as an obstructive right atrial mass in a patient with exertional dyspnea.

We report a case of lipomatous hypertrophy of the interatrial septum in a patient who presented with shortness of breath. Transesophageal echocardiography revealed a right atrial mass that caused a marked narrowing of the cavoatrial junction. The patient underwent successful resection of the mass with reconstruction of the interatrial septum. Histologic examination demonstrated proliferation of mature fat cells and hypertrophy of cardiac muscle cells consistent with lipomatous hypertrophy of the interatrial septum.