Lipomatous hypertrophy of the interatrial septum with partial SVC/atrial junction obstruction

Case contributed by Dr Jeewaka Mohotti

Presentation

The patient had a Chest X ray to investigate for emphysema. This was suspicious for hilar lymphadenopathy so a CT chest with intravenous contrast was performed to further investigate.

Patient Data

Age: 60 years old
Gender: Male

The intravenous contrast has been partially obstructed at the level of the SVC insertion into the right atrium. There is thickening of the inter atrial septum extending into the lateral right atrial wall which measure -50 to -70 HU. This is iso-dense to subcutaneous fat and the cardiac fat pad. There is a small central portion of the septum spared by the adipose hypertrophy in the expected location of the fossa ovalis. The presence of adipose thickening of the inter atrial septum with sparing of the fossa ovalis is suggestive of an incidental finding of lipomatous hypertrophy of the inter atrial septum. 

This zoomed axial image shows the dumbbell shaped appearance which occurs due to sparing of the fossa ovalis. The second image is identical but has the shape outlined in red to highlight it. 

Case Discussion

Limpomatous hypertrophy of the inter-atrial septum is a condition caused by benign proliferation of adipocytes in the inter-atrial septum. The condition is thus a hyperplasia rather than hypertrophy (cell enlargement) and some authors have proposed naming it as such 1. It is usually asymptomatic and an incidental finding but may be associated with atrial arrhythmias 2. Prevalence is estimated to 2-8% 3, 4. There is a tendency for it to occur more amongst the elderly and the obese 1.

The condition is characterised on CT by fat attenuation thickening of the inter-atrial septum. There is characteristically sparring of the fossa ovalis making the septum narrow and then thicken again on cross section giving rise to an appearance referred to as “dumbbell” like in shape 2.  This is clearly demonstrated in the key image above.

The thickening is often more prominent cranially and there have been at least 1 reported case where the SVC/atrial junction had been obstructed secondary to mass effect 5. In a case series of 12 patients by Meaney et al, 4 had 50-100% circumferential fatty involvement of the SVC and the remaining 8 all had at least 25% involvement 2

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Case Information

rID: 44445
Case created: 21st Apr 2016
Last edited: 7th May 2016
System: Cardiac
Inclusion in quiz mode: Included

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