[Lipomatous hypertrophy in the atrial septum].

Subcostal 4-chamber view of transthoracic echocardiography revealed abnormal thickening of atrial septum (arrow) in a 43-year-old Japanese woman with frequent atrial premature beats (A). MRI was obtained by the ECG-gated spin-echo technique. T1-weighted image of the heart demonstrated large fatty deposits (arrow) in the atrial septum, which have been referred to as lipomatous hypertrophy of the atrial septum (B). Lipomatous hypertrophy of the atrial septum has been reported to be a cause of atrial arrhythmias. Massive fatty deposits are seen not only in the atrial septum but also in other parts of the heart, such as atrial walls and epicardium (arrowheads). RA indicates right atrium; RV, right ventricle; LA, left atrium; and LV, left ventricle.