What is Transposition of the Great Arteries (TGA)?
The heart pumps the blood in the two arteries - the aorta which supplies the pure blood to the body and the pulmonary artery that supplies impure blood to the lungs. Normally the pulmonary artery arises from the right ventricle (right side of heart) and aorta arises from the left ventricle (left side of heart). In TGA, the aorta arises from the right ventricle and pulmonary artery arises from the left ventricle. Thus, in TGA, impure blood that returns to the right ventricle instead of going to the lungs passes into the aorta and back to the body. Also pure blood that comes from the lungs in the left ventricle goes back to the lungs through the pulmonary artery. As a result every organ of the body receives less oxygen and the patient looks "blue" due to less oxygenated blood.

How does a child with survive?
Since in TGA, 2 parallel circulations are created- one that carries the pure blood and one in which impure blood is carried, life would not be possible. Hence nature creates a way in which" MIXING" of both circulations can occur. This could be by way of another heart defect such as ASD - Atrial septal defect (mixing occurs at the level of the atria), VSD- Ventricular Septal defect (mixing occurs at the level of the ventricles) or PDA- Patent Ductus Arteriosus (mixing occurs by a channel between the aorta and the pulmonary artery).
PDA normally closes within hours after birth (DUCT DEPENDENT CIRCULATION) but a drug called Prostaglandin can keep it open for a few hours to days till surgery is performed.

How is TGA detected?
Any baby with bluish discoloration, breathlessness and heart failure is suspected to have TGA, which is diagnosed on echocardiography (ultra sound of the heart).

What happens if TGA is left untreated?
If TGA is left untreated, 90% of the patients do not survive more than 1 year of age.

When should a TGA be treated?
Most cases of TGA need to be treated “ AT BIRTH ” especially those with DUCT DEPENDENT CIRCULATION.
In patients with TGA and VSD, enough mixing of blood takes place for the child to survive. However, the child will have fatigue, giddiness, fainting spells, repeated chest infections, breathlessness and on long duration- irreversible thickening of blood vessels in lungs.
Also patients with TGA with VSD with narrowing of the pulmonary valve (Pulmonary valve regulates the outflow of blood from the right ventricle) survive upto their 20’s and 30’s as –hypertension in the blood vessels in the lungs develops late.
The type of operation depends on the associated heart defects, the age of the child and cost of surgery.


Last created on 6-05-2003
Last updated on 18-11-2006