Image of the Month – April 2016 – Mind the gap: atrial septal defects in the elderly

An 86 year-old male presented with progressive shortness of breath on exertion on a background of severe aortic stenosis. Cardiac computed tomgraphy demonstrated a hypertrophied left ventricle with a severely dilated right atrium (Figure A). Axial and sagittal multi-planar reconstructions revealed an ostium secundum atrial septal defect (ASD) with transit of contrast from the left to right atrium (Figure B and C). Transthoracic echocardiography confirmed a left-right shunt through the ostium secundum ASD (Figure D).

Ostium secundum ASDs are the most common type of ASD accounting for 80-90% of defects in the interatrial septum [1]. Shunt flow occurs predominantly during ventricular diastole with the direction of flow determined by difference in the compliance and capacity between the left and right ventricles [2]. Cardiac computed tomography acquisitions during late-diastole with opacification of the left heart can visualise ASDs without the requirement for the Valsalva manoeuvre.

In elderly patients with ostium secundum ASDs, larger left-right shunts may occur following changes in left ventricular compliance. In this case, the shunt acts as a ‘release valve’ for the left atrium to maintain lower pulmonary venous pressures. Closure of the defect may lead to an acute rise in left atrial pressure and precipitate pulmonary oedema.


[1] Johri AM, Rojas CA, El-Sherief A, et al. Imaging of the atrial septal defects: echocardiography and CT correlation. Heart. 2011;97:1441-1453.

[2] Sommer RJ, Hijazi ZM, Rhodes Jr. JF. Pathophysiology of Congenital Heart Disease in Adults. Part I: Shunt Lesions. Circulation. 2008;117:1090-1099.

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