CVS - Transposition of Great Arteries (TGA)

Question 1

Aetiology of TGA.

Answer 1

Failure of Aorticopulmonary Septum to spiral during septation.

Question 2

Risk Factor of TGA (1).

Answer 2

Diabetic Mother.

Question 3

Associated Features of TGA (3).

Answer 3

1. VSD.
2. Aortic Coarctation.
3. Pulmonary Stenosis.

Question 4

Clinical Features of TGA (4).

Answer 4

1. Cyanosis.
2. Tachypnoea.
3. Loud Single S2.
4. Prominent Right Ventricular Impulse.

Question 5

Pathophysiology of TGA (4).

Answer 5

1. Aorta leaves RV & Pulmonary Trunk leaves LV (wrong way around).
2. 2 Separate circulations don’t mix (Right = Systemic; Left = Pulmonary).
3. During Pregnancy = normal development of foetus with gas and nutrient exchange in placenta.
4. After birth = immediate life-threatening due to no connection = cyanosis.

Question 6

Investigations of TGA (2).

Answer 6

1. CXR - Egg-on-Side/String Appearance.

2. Diagnosed often during antenatal Ultrasound scans.

Question 7

Management of TGA (4).

Answer 7

1. Immediate survival depends on a shunt between the two circulations e.g. PDA, ASD or VSD (provides a few weeks of life before development of symptoms and respiratory distress).
2. Maintain Ductus Arteriosus with Prostaglandins.
3. Balloon Septostomy (insert catheter into Foramen Ovale via Umbilicus to inflate balloon and create a large ASD).
4. Definitive = Surgical correction (Open Heart Surgery) : cardiopulmonary bypass machine is used to perform an ‘arterial switch’. Correct any co-existing defects.