CT APPEARANCE OF LIPOMATOUS HYPERTROPHY OF THE INTERATRIAL SEPTUM

OBJECTIVE. We undertook this study to determine the CT findings of lip omatous hypertrophy of the interatrial septum, an asymptomatic and und errecognized benign proliferation of fat within the atrial septum. MAT ERIALS AND METHODS. We retrospectively identified 12 cases of lipomato us hypertrophy of the interatrial septum by searching the radiology re cords at our institution from 1991 to 1995. We reviewed the CT scans o f these patients to determine the distribution and morphology of fat w ithin the interatrial septum.RESULTS. In ail patients with lipomatous hypertrophy, a mass of fat attenuation extended from the coronary sinu s to just above the level of the aortic root with relative sparing of the fossa ovalis, which resulted in a dumbbell configuration. Average dimensions were 7 cm for craniocaudal extent (range, 6-9 cm), 4.5 cm a long the interatrial septum (range, 3.6-6.2 cm), and 2.7 cm perpendicu lar to the septum (range, 1.5-4.8 cm), Increased epicardial fat was se en on CT scans in 10 patients (83%). CT revealed mediastinal lipomatos is in six patients (50%). No patients had undergone corticosteroid tre atment or total parenteral nutrition. No electrocardiographic or funct ional cardiac abnormalities were seen. CONCLUSION. On standard, high-r esolution, and enhanced CT images, lipomatous hypertrophy of the inter atrial septum is shown as a nonenhancing smoothly marginated homogenou s dumbbell-shaped mass of fat attenuation confined to the interatrial septum. These characteristic morphologic features allow confident diag nosis and help differentiate this benign condition fi om other cardiac masses.