Abnormalities seen in the great arteries view
Transposition of Great Arteries
In Simple TGA the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. The four-chamber view is usually normal. The first great artery seen above the level of the four-chamber view is the branching pulmonary artery. The aorta originates from the right ventricle in continuity with the aortic arch and the head and neck vessels. There is no normal ‘crossing over’ of the great arteries as they arise in parallel. The ‘three-vessel view’ is abnormal because the pulmonary artery and arterial duct lie below the aorta and aortic arch.
Prevalence
This defect is found in about 1 in 10,000 live births.
Other abnormalities
This defect is rarely associated with extracardiac defects or chromosomal abnormalities.
Prognosis
Simple TGA requires surgical treatment (mortality is less than 5%) in the first weeks of life and the long-term outcome is good. In cases where there are additional findings such as ventricular septal defect and pulmonary stenosis the outcome is less favourable.
A case of simple TGA
This clip demonstrates a parallel great artery arrangement. The artery (red line) with early branching (pulmonary artery) is arising from the left ventricle. The artery (yellow line) which gives the aortic arch (aorta) arises from the right ventricle. Please note that the great arteries are not crossing over. The four-chamber view is normal but there is suspicion of possible small subpulmonary VSD (yellow circle). This would need to be confirmed in lateral view using colour Doppler.