Secundum atrial septal defect

Last revised by Dr David Carroll on 28 May 2022

A secundum atrial septal defect (ASD) is the most common congenital abnormality of the interatrial septum. It describes a defect in the center of the interatrial septum in the region of the fossa ovalis and is most commonly due to a discontinuity in the portion of the septum derived from the embryologic septum primum 1.

Associations

Radiographic features

Echocardiography

Secundum ASDs may be visualized from parasternal, apical and subxiphoid windows on transthoracic echocardiography. The subxiphoid windows typically offer the most reliable evaluation of the atrial septum as the perpendicular vantage point it affords imparts a lesser degree of acoustic dropout. Non-standard imaging views between standard short and long axes may be required for optimum visualization of the full length of the interatrial septum 3.

A secundum ASD will appear as a variably sized area of septal "dropout," or absence of tissue, in the mid/central interatrial septum about the fossa ovalis delimited by inferior and superior rims of septum 1. It should demonstrate interatrial flow when assessed with color flow Doppler, and should be discrete from the ostia of the right pulmonary veins and the free wall of the right atrium. The anterior and posterior rims are best visualized using a parasternal short axis view at the base 4.

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Cases and figures

  • Case 1: secundum ASD on CMRI
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  • Case 2: secundum ASD on CT
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