Transposition of the great arteries involves swapped attachments of the aorta and the pulmonary trunk. The right ventricle pumps blood into the aorta and the left ventricle pumps blood into the pulmonary vessels. Blood from the systemic venous system drains into the right side of the heart and is pumped straight back into the aorta. Blood from the pulmonary veins drains into the left side of the heart and is pumped straight back into the pulmonary arteries. These two separate circulations do not mix.
Fetal development is typically normal, as gas and nutrient exchange happens in the placenta. Blood does not need to travel to both the lungs and the systemic circulation. However, it is immediately life-threatening after birth. The newborn will be cyanotic.
Immediate survival depends on a shunt connecting the systemic and pulmonary circulation. This can occur across a patent ductus arteriosus, atrial septal defect, or ventricular septal defect.
Presentation
The defect is often diagnosed during pregnancy with antenatal ultrasound scans. Close monitoring is necessary during the pregnancy, and arrangements are made for specialist management immediately after birth.
When the defect is not detected antenatally, it presents with cyanosis shortly after birth.
A patent ductus arteriosus or ventricular septal defect can initially compensate by allowing blood to mix between the systemic circulation and the lungs. However, within a few weeks, they will develop respiratory distress, tachycardia, poor feeding, poor weight gain, and sweating.
Management
A prostaglandin E2 infusion is used to maintain the ductus arteriosus. This allows blood to flow from the aorta to the pulmonary arteries and lungs for oxygenation.
Balloon septostomy involves inserting a catheter into the foramen ovale via the umbilicus and inflating a balloon to create a connection between the atria. This allows blood from the pulmonary veins to flow from the left atrium to the right atrium, where it can flow to the right ventricle and aorta.
Definitive management involves an arterial switch operation. The aorta and pulmonary trunk are switched to their correct locations. This is usually performed within a few days of birth.
Last updated January 2025
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