Transposition of the Great Arteries
Transposition is one of the core neonatal diagnoses to grasp. Correct diagnosis is critical as antenatal diagnosis can be difficult, and infants often present shocked and in need of resuscitation and urgent cardiology intervention (including emergency balloon atrial septostomy).
In the normal heart the aorta and pulmonary trunk can readily be seen to cross. From the parasternal long axis view this can be demonstrated by visualising the aorta heading parallel to the tranducer, and then sweeping to look to the subjects left shoulder where the pulmonary trunk is visible.
This crossing can also be seen from the apical four chamber view. A further check comes from demonstrating bifurcation of the vessel leaving the right ventricle.
In the case of transposition the pulmonary trunk and aorta can be seen to be parallel in the long axis view. This is NEVER NORMAL!
Also the vessel exiting the right ventricle does not bifurcate, rather it can be seen to become the aortic arch.
If you suspect transposition urgent referral to a cardiologist is mandatory. They may need to perform an urgent balloon atrial septostomy, so try to estimate whether there is mixing at the atrial level.