Transposition of Great vessels is a congenital heart disease, involving a spatial mal-arrangement of any of the major blood vessels of Superior and Inferior Venacava, Pulmonary artery, Pulmonary veins and the Aorta. When there is only involvement of the large arteries, a subgroup called Transposition of great arteries(TGA) occurs. d-TGA is the second most common cyanotic congenital heart disease. Although “transposed” literally means “swapped”, many types of TGV involve vessels that are in abnormal positions, while not actually being swapped with each other.
The major causes, for a child being born with transposition of great arteries are
- A mother who had rubella(German measles) or another viral illness during pregnancy
- A parent who had transposition of the great arteries or another congenital heart defect
- Poor nutrition during pregnancy
- Excessive alcohol consumption during pregnancy
- A mother older than 40
- A mother who has diabetes
- Down syndrome in the baby, which increases the risk of transposition of the great arteries and other congenital heart defects.
In a normal heart, the blood from the left side of the body is pumped into aorta and from the right side to the pulmonary arteries. Left side of heart receives oxygenated blood from the lungs, where as the right side receive deoxygenated blood from elsewhere.
TGV can be either:
- Dextro or d-TGA
- Levo or l-TGA
With d-TGA, deoxygenated blood from the right heart is pumped immediately through the aorta and circulated to the body and the heart itself, bypassing the lungs altogether, while the left heart pumps oxygenated blood continuously back into the lungs through the pulmonary artery. In effect, two separate “circular”(parallel) circulatory systems are created. The common symptoms being, cyanosis – bluish discoloration of skin, will appear in peripheral areas: around the mouth and lips, fingertips, and toes. A d-TGA baby will exhibit indrawing beneath the ribcage and rapid breathing. The infant will be easily fatigued and may experience weakness, particularly during breast feeding or playing; this interruption to feeding can cause growth failure. If d-TGA is not diagnosed and corrected early on, the infant may eventually experience episodes of loss of consciousness and develop clubbing – thickening of the nail skin interface of the fingers and toes. If not attended to promptly, it can lead to heart failure.
d-TGA can be diagnosed in a fetus by an ultrasound scan around 18 weeks of gestation, if not the cyanosis at birth acts as a indicator of an underlying condition. Further investigation can be carried on using echocardiography, chest x-ray and electrocardiography. Treatment options available are:
Cardiac catheterization: using a guide wire passed through an artery in the thigh. Many different techniques are available in this field. Usually used as the first step before definitive corrective procedures as the two listed below
Medical therapy: diuretics, oxygen therapy.
Arterial switch operation
After the corrective surgery the baby should be on a constant follow up at a cardiologist. Sometimes long term medication and counseling of the care taker fro the same may be necessary.
l-TGA is commonly referred to as congenitally corrected transposition of the great arteries(CC-TGA), is an acyanotic congenital heart defect, in which the aorta and the pulmonary artery are transposed and the morphological left and right ventricles are also transposed. With l-TGA, deoxygenated blood is pumped from the right atrium into the morphological left ventricle(which lies on the right side of the heart), then through the pulmonary artery to the lungs. The oxygenated blood then returns, via the pulmonary veins, to the left atrium from which it is pumped into the morphological right ventricle, then through the aorta. Simple l-TGA does not immediately produce any visually identifiable symptoms, but since each ventricle is intended to handle different blood pressures, the right ventricle may eventually hypertrophy due to increased pressure and produce symptoms such as breathing difficulty or fatigue.
l-TGA can sometimes be diagnosed in a fetus, inutero, with an ultrasound scan, after 18 weeks gestation. However, many cases of simple l-TGA are “accidentally” diagnosed in adulthood, during diagnosis or treatment of other conditions. Simple l-TGA has a very good prognosis, with many individuals being asymptomatic and not requiring surgical correction. In a number of cases, the surgical correction has been successfully performed, in the early life, to restore the normal blood flow through the ventricles. Commonly employed surgical option is an Arterial double switch operation, which is both technically challenging and requires expertise.