Causative & risk factors
Transposition of the great arteries is a congenital defect, the exact cause of which is not known. Under normal circumstances, the pulmonary artery is attached to the right ventricle whereas the aorta attached to the left ventricle.
The function of the pulmonary artery is to carry deoxygenated blood from the heart to the lungs in order to get oxygenated. The function of the aorta is to distribute the oxygenated blood to various body parts.
In transposition of the great arteries, the pulmonary artery and the aorta are connected to the left ventricle and the right ventricle respectively. This results in oxygenated blood being transported to the lungs, whereas deoxygenated blood circulates through rest of the body.
Certain risk factors have been identified that are associated with this heart defect. They include a familial tendency to congenital heart defects, maternal infection during pregnancy, malnutrition or excessive alcohol intake during pregnancy. Advanced maternal age and gestational diabetes are also associated with a higher risk.
Clinical presentation
Circulation of deoxygenated blood through the body gives a bluish tinge to the skin (cyanosis). The baby doesn’t feed well and his weight is below average. He/she may appear breathless.
Undetected or untreated transposition of the great arteries can lead to heart failure and eventual death of the baby.
Investigations
Transposition of the great arteries can be diagnosed while the fetus is in-utero.
This condition can be diagnosed soon after birth, since cyanosis (bluish discoloration of the skin) becomes obvious. Auscultation of the chest will sometimes reveal a heart murmur.
As soon as anything abnormal is suspected, echocardiography of the heart is performed to detect the position of the arteries and any associated heart defects.
Other basic tests such as chest X-ray and an ECG are carried out.
If no definitive diagnosis has been reached after these tests, cardiac catheterization is performed. A thin catheter is introduced into the baby’s heart via his groin and a dye is injected. The pressure in the heart chambers can be measured via this procedure and also X-ray images of the heart are taken.
Cardiac catheterization is sometimes used as a therapeutic procedure to perform may be done urgently to perform a balloon atrial septostomy.
Treatment
Surgery is the choice of treatment.
Before surgery, a procedure known as atrial septostomy is performed to increase the supply of oxygen to various body parts.
The primary surgical procedures are an ‘arterial switch’ or an ‘atrial switch’.
Arterial switch operation – The pulmonary artery and the aorta are moved to their normal positions and the coronary arteries are reattached to the aorta.
Atrial switch operation – A tunnel is made between the right and left atrium.
Even after corrective surgery is performed, the patient must be regularly monitored by a cardiac physician throughout his lifetime.
