The third view in the series is the apical four chamber view. Place your echo probe on the apex beat. This can be difficult to palpate in small infants, so it's often best to start just below the left nipple. The side marker on the probe should still be pointing to the patient's left.
This is probably the core view for neonatal echocardiography, and actually contains much of the information needed to exclude structural congenital heart disease (though you should always perform the full sequence of scans!)
(IVS-Inter-ventricular septum, LA-Left Atrium, LV-Left Ventricle, MV-Mitral Valve, RA-Right Atrium, RV-Right Ventricle, TV-Tricuspid Valve)
As you can see, the tricuspid valve should be placed more towards the apex of the heart than the mitral valve. This is a subtle but important sign - it essentially rules out atrioventricular septal defects (also known as endocardial cushion defects, and associated with Trisomy 21).
It's worth using colour Doppler to demonstrate normal flow through the mitral and tricuspid valves.
Apical 4 chamber Mitral Inflow:
Apical 4 Chamber Tricuspid Inflow:
Once again you should use colour Doppler to exclude flow across the ventricular septum which would indicate a VSD. Look carefully for these as they are common, and may also indicate additional structural defects, e.g. coarctation. Within hours of life the normal right sided pressure will have dropped below systemic values, so a VSD will almost always be associated with shunt visible on colour Doppler.
Apical 4 Chamber Doppler:
Another key anatomical defect to rule out is total anomalous pulmonary venous drainage (TAPVD). This is extremely difficult. However the pulmonary veins are often visible from the apical 4 chamber view. You will need to use colour Doppler, and may also need to increase the colour Doppler gain and decrease the colour Doppler velocity range scale to visualise the veins. A clear flow of blood should be visible from the veins directly into the left atrium.
Lastly from the apical view, sweep anteriorly to image the great arteries. For the aorta this is often referred to as the '5 chamber view'.
Once again colour Doppler is useful to delineate the vessels. Now, since blood is travelling away from the Doppler probe, the blood in the aorta and pulmonary will appear blue.