Subcostal Atrial and Four Chamber View
The second view in the series is the subcostal atrial and four chamber view. Keep your echo probe under the xiphisternum, but tilt it as if you were looking at the ground below the subjects head, roughly at a 45 degree angle to the horizontal. The side marker on the probe should still be pointing to the left. You'll need to invert the screen vertically so that the apex of the imaging triangle is now at the bottom of the screen (see below).
This view contains key information, and is particularly valuable where other viewing windows are poor (e.g. in pneumothorax/chronic lung disease) as it essentially uses the liver as a window.
Look first for an intact intra-atrial septum using 2D imaging. Sweep anteriorly and posteriorly to ensure you've visualised the entire intra-atrial septum.
(IAS-Inter-atrial septum, LA-Left Atrium, RA-Right Atrium, )
It's also helpful to use colour Doppler to look for flow across the septum. A patent foramen ovale (PFO) is physiological in the newborn (and in around 10% of adults). Generally flow through a PFO is predominantly left-to-right, and therefore will appear red on colour Doppler
From the atria sweep slightly anteriorly to interrogate the membranous portion of the ventricular septum. Again colour Doppler helps exclude a defect (VSD). This is worth doing at this stage as from an apical 4 chamber view the thinness of the membranous septum means that it may not reflect sound waves, and therefore mimic a VSD.
(Ao-Aorta, IVS-Inter-ventricular septum, LV-Left Ventricle, RV-Right Ventricle)
Finally you may wish to sweep yet more anteriorly to interrogate the great arteries. First the aorta should come into view, then the pulmonary artery. To exclude transposition of the great arteries (TGA) the vessels should be clearly seen to cross at this point.
(IVS-Inter-ventricular septum, LV-Left Ventricle, MPA-Main Pulmonary Artery, RV-Right Ventricle)
At this point you should also be able to see the superior vena cava (SVC) entering the right atrium (see also the functional echo section).