Overview
Transposition of the great arteries (TGA) describes a congenital cyanotic heart disease characterised by the swapping of the aorta and pulmonary trunk. As a result, the aorta emerges from the right ventricle and the pulmonary trunk emerges from the left ventricle creating two parallel circuits which are incompatible with life. One circuit goes from the right ventricle to the body, the other circuit goes from the left ventricle to the lungs.
Some types of TGA are associated with ventricular septal defect (VSD) and pulmonary stenosis. This can affect the severity of their symptoms.
Patients with TGA need a patent ductus arteriosus (PDA) or VSD to stay alive as this allows the mixing of oxygenated and deoxygenated blood between the two circuits. This is reflected in the management of TGA, discussed below.
Presentation
Infants become cyanotic within the first week of life, and this may even occur shortly after birth. Other features include:
- Cyanosis – depends on the presence of a VSD, which can allow mixing between the two circuits formed, resulting in less or minimal cyanosis
- Tachypnoea, tachycardia, poor feeding, and irritability
- The S2 heart is loud and single
- S2 is normally split because the aortic valve closes before the pulmonary valve
- A prominent ventricular impulse and systolic thrill may be felt
Investigations
Investigations must not delay management. If a cyanotic heart disease is suspected in a neonate, prostaglandins should be given to keep the ductus arteriosus patent. Neonates should be transferred to a cardiac centre immediately.
Some investigations may include the following, however, initial treatment must not be delayed:
- ECG:
- May show right axis deviation and right ventricular hypertrophy
- Chest x-ray:
- May show an ‘egg on string’ or ‘egg on side’ appearance of the heart
- Echocardiography:
- Identifies TGA
Management
Overview
- Prostaglandin infusion:
- This keeps the ductus arteriosus open to allow the mixing of deoxygenated and oxygenated blood between the two separate circuits in TGA to buy time for definitive management
- Definitive management involves surgical correction.
Prognosis and Complications
- After correction, the 20-year-survival is around 90%
- Some complications occurring after correction may include:
- Arrhythmia
- Coronary artery disease
- Pulmonary artery stenosis
- Coronary artery stenosis
- Aortic root dilation
