Transposition of the great arteries

Question 1

What is TOGA?

Answer 1

Where the attachments of the aorta and the pulmonary trunk are swapped (’transposed’). This means that the RV pumps blood into the aorta and the LV pumps blood into the pulmonary vessels.

Question 2

Which children are more at risk of this?

Answer 2

Children of diabetic mothers are at increased risk of TGA.

Question 3

What can this condition be associated with?

Answer 3

VSD, coarctation of the aorta, pulmonary stenosis.

Question 4

How will the baby present at birth and why?

Answer 4

• During pregnancy, gas and nutrient exchange happens in the placenta, so it’s not necessary for blood to flow to the lungs.
• After birth, the condition is life-threatening as there’s no connection between the systemic circulation and the pulmonary circulation, so the baby will be cyanosed.

Question 5

What is immediate survival dependent on?

Answer 5

A shunt between the systemic circulation and pulmonary circulation that allows blood flowing through the body an opportunity to get oxygenated in the lungs. This can occur across a PDA, ASD, or VSD.

Question 6

Diagnosis?

Answer 6

Usually diagnosed during pregnancy with antenatal scans.

Question 7

How does it present?

Answer 7

• If not detected during pregnancy, it’ll present with cyanosis at or within a few days of birth.
• A PDA or VSD can initially compensate by allowing blood to mix between the systemic circulation and lungs, but within a few weeks they will develop respiratory distress, tachycardia, poor feeding, poor weight gain and sweating.

Question 8

Clinical features?

Answer 8

• Cyanosis
• tachypnoea
  loud single S2
• prominent right ventricular impulse palpable on examination
• ‘egg on side’ appearance on CXR.

Question 9

Management?

Answer 9

1. If there’s a VSD, this will allow some mixing of blood between the 2 systems and provide some time for definite treatment. 2. Prostaglandin infusion - maintain the ductus arteriosus → allows blood from the aorta to flow to the pulmonary arteries for oxygenation.
2. Balloon septostomy - insert catheter into foramen ovale via the umbilicus and inflating a balloon to create a large ASD → this allows oxygenated blood returning from the lungs from the pulmonary veins (on the left side) to flow to the right side of the heart through the aorta to the body.
3. Open heart surgery = definitive treatment - cardiopulmonary bypass machine is used to perform an ‘arterial switch’ procedure within a few days of birth. Any VSD or ASD present can be corrected at the same time.