Dissimilar Motion Patterns of the Fossa Ovalis and Rest of the Atrial Septum in a Patient With Atrial Fibrillation and Lipomatous Hypertrophy

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Rami N. Khouzam, MD
Ivan A. D'Cruz, MD, FRCP

University of Tennessee Health Science Center and VA Medical Center, Cardiology Section, Memphis, TN

Case Presentation:

An 85 year old man had atrial fibrillation for more than 10 years for which he was on anticoagulation therapy. He also had hypertension, history of stroke, and congestive heart failure - NYHA Class II.

On a routine follow-up visit the ECG (above) showed atrial flutter-fibrillation.

An echocardiogram was performed. In the subcostal view of the transthoracic echocardiogram - the thin fossa ovalis (fo) can be seen forming the floor of the crater-like limbus region of the interatrial septum (IAS). The remaining atrial septum is somewhat thicker than normal - probably due to lipomatous hypertrophy. This is shown in the two images below.

Whereas the thin membrane of the fossa ovalis shows prominent undulations, the thicker part of the atrial septum shows finer, more rapid oscillations. This is shown in the two M-mode images below. The 2D component of the M-mode image immediately below demonstrates the path of the M-mode beam through the thin membrane of the fossa ovalis. The subsequent lower image shows an M-mode beam through the thicker (fat-infiltrated) atrial septum. The differences in motion are more obvious on the left atrial (LA) side of the interatrial septum in both images. ECG is shown for comparison.


This case shows two different types of motion within the interatrial septum in a patient with atrial flutter-fibrillation. The motion discrepancies are presumably made more obvious by fatty infiltration of the interatrial septum.

The echocardiographic diagnosis of lipomatous hypertrophy is made when there is marked thickening of the interatrial septum with sparing of the fossa ovalis.


Nadra I, Dawson D, Schmitz SA, Punjabi PP, Nihoyannopoulos P. Lipomatous hypertrophy of the interatrial septum: a commonly misdiagnosed mass often leading to unnecessary cardiac surgery. Heart. 2004;90(12):e66

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