Transposition of the Great Arteries (TGA)

Second most common cause of cyanotic CHD diagnosed by 1 year of age

The most common cyanotic CHD that presents in the first day of life.

The aorta lies anteriorly and arises from the right ventricle; the pulmonary artery is relatively posterior and connected to the left ventricle (ventriculoarterial discordance). Deoxygenated blood is therefore returned to the body and oxygenated blood is returned to the lungs. The pulmonary and systemic circuits are arranged in parallel. Unless there is mixing of blood between them, this condition is incompatible with life.

The presentation for infants with TGA depends on the degree of blood mixing. Fortunately, there are a number of naturally occurring associated anomalies, e.g. VSD, ASD and PDA.  Initial survival depends on the presence of a shunt, allowing mixing between the systemic and pulmonary circulations.

These infants present with cyanosis at birth because of right-to-left shunting, and the cyanosis becomes more severe when the ductus arteriosus closes.

Fig 2: Transposition of the Great Arteries


Clinical presentation

  • The lesion is frequently detected antenatally. Cyanosis is the predominant symptom. Presentation is usually on day 2 of life when ductal closure leads to a marked reduction in mixing of the desaturated and saturated blood.
  • Cyanosis may be less severe and presentation is delayed if there is more mixing of blood from associated anomalies, e.g. an ASD.
  • Hypoxia and acidosis
Physical signs
  • Cyanosis is always present
  • The second heart sound is often loud and single
  • Usually no murmur


Chest radiograph
  • “egg on a string” appearance
  • The “egg” = enlarged and globular shaped heart with an abnormally convex right atrial border and an enlarged left atrium
  • The “string” = narrow mediastinum due to the anteroposterior (AP) position of the great vessels
  • Cardiomegaly with increased vascular markings (increased pulmonary blood flow)
  • Right axis deviation (RAD) and right ventricular hypertrophy (RVH)
  • Demonstrate the abnormal arterial connections and associated abnormalities


In the sick cyanosed neonate, the key is to improve mixing. The outcome depends on the degree of blood “mixing,” the magnitude of tissue hypoxia, and the ability of the right ventricle to maintain the systemic circulation. Without surgery, most patients die within months.

Maintaining the patency of the ductus arteriosus with a prostaglandin infusion is helpful. However, this systemic-to-pulmonary connection tends to close early and thus intervention is required to create a new shunt such as balloon atrial septostomy within the first few days of life.

3)   Total Anomalous Pulmonary Venous Return (TAPVR)

Rare CHD; 2% to 3% of CHD presenting in the neonatal period.

It is characterized by anomalous drainage of all pulmonary veins to the systemic circulation. There is embryologic failure of the pulmonary veins to form a connection to the left atrium, and thepulmonary vein carries blood from the lungs to the right atrium. This results in a left-to-right shunt of oxygenated blood back to the lungs rather than to the body. Though pulmonary venous blood does come to the right side, there is complete mixing in the right atrium, and “right-to-left” shunting across the ASD making this a cyanotic lesion.

It is classified depending on where the pulmonary vein drains:

  • Type I: Superior vena cava (supra-cardiac) 55%
  • Type II: Right atrium (via the coronary sinus) 30%
  • Type III: Portal vein (infra-cardiac)
  • Type IV: Mixed with 2 or more anomalous connections

Anatomically it can be classified as

  • Supra-diaphragmatic (supra-cardiac or cardiac)
  • Infra-diaphragmatic; depending on the location where the anomalous venous connection occurs

Physiologically, this can be classified as obstructive or nonobstructive (depending on whether free flow through the pulmonary veins is impeded or not)

  • The most frequent is the non-obstructive, supradiaphragmatic form
  • The most classic is infra-diaphragmatic with obstruction
  • Presentation: Presents in early infancy; 50% within the first month and almost 90% by one year of age.
  • Obstructive TAPVR present with cyanosis in the first hours to days of life.
  • Non-obstructive TAPVR has minimal no cyanosis and presents with CHF between the ages of 4 and 6 weeks
  • Congestive heart failure (obstruction in these anomalous connections)
  • Cyanosis (subtle in unobstructed forms, severe in obstructed forms)
  • Loud single S2 (fixed, widely split)
  • EKG: Right axis deviation, right ventricular hypertrophy and right atrial enlargement
  • Chest Radiograph: The findings depend on the level of venous drainage and the presence or absence of obstruction
  • Significant cardiomegaly with increased pulmonary vascular markings (snowman appearance or “figure-of-eight” sign in infants over 4 months in type I TAPVR)
  • “snowman” head = Wide mediastinum due to dilated right SVC and a left vertical vein represents the confluence of the pulmonary veins posterior to the left atrium.
  • “snowman” body = heart
  • Supra-diaphragmatic TAPVR without obstruction = cardiomegaly, increased pulmonary vascularity, and pulmonary arterial dilation
  • Infra-diaphragmatic TAPVR with obstruction = small heart with pulmonary venous congestion


Surgical correction in which the common pulmonary venous confluence or the individual pulmonary veins are mobilized and anastomosed with the left atrium.