Echocardiographic Diagnosis of Atrial Septal Defect

Essential 2D Echocardiographic Features

The American Heart Association recommends that the entire atrial septum from the superior vena cava orifice to the inferior vena cava orifice must be visualized to detect sinus venosus defects or extension of large secundum defects 1, 2
Subcostal views with deep inspiration and high right parasternal views are particularly helpful for imaging ASD in adults 1, 2
Right ventricular volume overload with RV enlargement is the hallmark finding indicating hemodynamically significant shunting 1, 2
Right atrial enlargement is a common finding in patients with ASD 1, 2

Secundum ASD is located centrally in the fossa ovalis region 3, 4
Primum ASD is characterized by a defect in close proximity to atrioventricular valves with no offset between the valves 3, 4
Sinus venosus defects are often missed by TTE due to superior location and require TEE for definitive diagnosis 1, 2

TEE becomes necessary when transthoracic images are poor quality in adults 1
TEE is required for exact localization and sizing of the ASD for intervention planning 1
Identification of all pulmonary vein connections is required using TEE 1

Rim characterization is paramount, with rim width <5 mm (except at the aortic side) generally precluding device closure 7, 6
Assessment includes largest defect diameter, tissue strands crossing the defect, extensive Eustachian valve or Chiari network, and concomitant pulmonary venous anomalies 7, 6

Apparent septal dropout on 2D images may mimic ASD, and contrast echocardiography or TEE should be used to confirm 1, 2
Sinus venosus ASDs are commonly missed due to superior location, and patients with unexplained RV volume overload by TTE should undergo TEE or alternative imaging 1, 2