With this defect, the positions of the vessels that take blood away from the heart to the lungs and the body are switched.
So the aorta comes out of the right ventricle, while the pulmonary artery comes out of the left ventricle. This means that
blood that already has oxygen flows to the lungs, while blood that needs oxygen flows around the body.
About 5% to 7% of babies with CHD have this defect. It is considered to be the defect most commonly identified in the first
week of life. This defect is fatal unless another defect exists that allows blood to mix between the two circulation systems
so that the body gets the oxygen it needs. This usually means an atrial septal defect, a ventricular septal defect, or ductus
arteriosus. Babies born with transposition of the great arteries show symptoms — mainly cyanosis — immediately after birth.
| Transposition of the Great Arteries |
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| The large vessels that carry blood out of the heart have switched positions. The aorta carries deoxygenated blood to the body
(instead of oxygenated blood) while the pulmonary arteries carry oxygenated blood to the lungs (instead of deoxygenated blood).
As a result, blood in need of oxygen circulates through the body instead of the lungs.
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There are two types of TGA: D-TGA and L-TGA. D-TGA is known as “complete” TGA; the "D" stands for dextroposition . The "L"
in L-TGA stands for levotransposition. In D-TGA, the aorta and the pulmonary artery have switched places, leaving the child
very cyanotic. In L-TGA, the aorta and pulmonary artery are in the right place but the ventricles have switched places. This
significantly raises the risk of having other heart defects. L-TGA occurs in less than 1% of all patients with CHD, and D-TGA
in about 5%.
How is transposition of the great arteries treated?
Initially, a drug called prostaglandin will be given to keep the ductus arteriosus open to improve circulation. Another temporary
procedure that can help mixing of the blood is a balloon atrial septostomy, which puts a hole or opening between the left
and right atria. This is a temporary measure until the child is old enough for surgery to establish normal blood circulation.
Surgery, in this case, an arterial switch procedure, within the first few weeks of life is needed to correct the blood flow.
This open heart procedure involves “switching” the pulmonary artery and the aorta back to their normal positions and attaching
the coronary arteries to the new aorta in the correct positions.
What is the long-term outlook for children with transposition of the great arteries?
The long-term outlook depends on the type of repair. In the past, patients with "atrial switch" repairs (sometimes called
Mustard or Senning repairs) were at risk of losing their normal cardiac rhythm over time and being at risk of arrhythmias,
which can lead to sudden cardiac death. Leakage of blood backward through the valve (blood regurgitation) is also a risk,
along with ventricular failure and obstruction of the tunnel created to redirect blood flow (baffle obstruction). More recently,
almost all children with TGA undergo an "arterial switch repair" (also called the Jatene repair) which appears to significantly
reduce these risks, although a small percentage of patients may have long-term problems with their coronary arteries.
