Interatrial septum in subcostal view

Interatrial septum in subcostal view

Interatrial septum in subcostal view

False echo dropouts can occur in the interatrial septum in apical four chamber view as the ultrasound beam is parallel to the structure being imaged. Subcostal view is best for imaging the interatrial septum. This picture in subcostal view gives an excellent image of the interatrial septum between the right atrium above and the left atrium below. Most echocardiographers use this orientation for subcostal view, though it is anatomically an inverted view as the transducer is kept below the structures being imaged. On the contrary, most pediatric echocardiographers invert the image in the machine while imaging from the subcostal view in order to get a more straight forward anatomical orientation of structures being imaged.

Colour Doppler imaging of interatrial flow across and atrial septal defect or patent foramen ovale is also good in this view as the principle of Doppler is that the imaging is better when the flow being imaged is parallel to the ultrasound beam.

Left to right flow will be seen as red and reversal of shunt will be shown as blue, in this view. Gradient across the defect in IAS is also accurately measured by this approach. The gradient will be significant in restrictive defects while it will be negligible in a large defect. Reverse flow across the IAS in the absence of features of pulmonary hypertension should alert us to the possibility of total anomalous pulmonary venous drainage. This will initiate a meticulous imaging of pulmonary venous connections.

Martin SS and colleagues suggested that if a good subcostal view can be obtained, it is the preferred view for the interatrial septum as it is almost perpendicular to the path of the echocardiographic beam [1]. They mention that though apical four chamber view is useful in assessing the right heart, parallel orientation of the interatrial septum can lead to false echo dropouts as mentioned initially. Other views like parasternal short axis views and non standard views have been suggested as complementary views to obtain more information.

Reference

  1. Martin SS, Shapiro EP, Mukherjee M. Atrial Septal Defects – Clinical Manifestations, Echo Assessment, and Intervention. Clin Med Insights Cardiol. 2015 Mar 23;8(Suppl 1):93-8.