| From your Guide Dr.MANI |  | |
Transposition of Great Arteries | ||
| From your Guide Dr.MANI | | |
Transposition of Great Arteries | ||
| |
What is Transposition of the Great Arteries ?
The two "great" arteries of the body are the AORTA and the PULMONARY ARTERY. The
aorta comes out of the left ventricle, and carries pure blood to the rest of the body. The pulmonary
artery arises from the right ventricle and carries impure blood from the veins into the lungs for
oxygenation.
Transposition of the Great Arteries - TGA, for short - as the name implies, means the two arteries
are "transposed". That is, the aorta arises from the RIGHT ventricle, and the pulmonary artery from
the LEFT ventricle.
What happens in TGA ?
You have read all about the circulation of blood in the body. So it must be clear to you that a
situation like TGA will not permit normal circulation and oxygen supply to the different organ
systems of the body.
When "impure" venous blood returns to the right ventricle (instead of going to the lungs as it
normally does), it passes into the transposed aorta. This impure blood is then distributed to the rest
of the body. So every organ of the body will receive blood with very little oxygen and a lot of
waste materials. The patient looks "blue" - CYANOSIS - and so TGA is another example of a
congenital cyanotic heart disease, like Tetralogy of Fallot and Pulmonary Atresia.
On the contrary, when "purified" blood with oxygen returns to the left ventricle from the lungs,
instead of being pumped into the aorta, it passes into the transposed pulmonary artery. This "pure"
blood makes another trip to the lungs. As it is already fully saturated with oxygen, this trip is
useless.
If the two sides of the circulation were completely separate, life would not be possible beyond a
few minutes. But once again Nature plays its wonderful role. By creating an additional defect, the
child is kept alive for a few hours or days, so that medical care can be given, and the condition
repaired.
So what is Nature's protective method ?
The basic problem of transposed arteries cannot be corrected without operation. However, if the
two sides of the circulation could be made to MIX with each other, there would be atleast partial
improvement. The child could live a little longer; long enough for surgery to be performed.
How then can this mixing be brought about ?
In many cases of TGA, there is an associated hole or defect in the wall between the atrium or
ventricle - called Atrial Septal Defect (ASD) or Ventricular Septal Defect (VSD). Across these
defects, blood mixes. But even when these defects are absent, there is still another chance.This other site of mixing is the Patent Ductus Arteriosus (PDA). As I mentioned in another article,
PDA is a tube connecting the aorta and pulmonary artery. It normally closes within minutes or
hours after birth. But it can be kept open artificially by using a drug called PROSTAGLANDIN.
Prostaglandin is a "miracle" drug, that has been a boon for children with complex birth defects of
the heart. It is also the mainstay in treatment of TGA patients. Prostaglandin infusion is started as
soon as the diagnosis of TGA is made, and continued until surgery is possible, usually within a few
hours or days.
What are the problems if TGA is left untreated ?
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