TRANSPOSITION OF THE GREAT ARTERIES
Transposition of the great arteries (TGA) is a heart defect that occurs from birth (congenital).
The two major arteries that carry blood away from the heart, the aorta and the pulmonary artery, are switched (transposed).
The cause of TGA is unknown. It is not associated with any one common genetic abnormality. It rarely occurs in other family members.
TGA is a cyanotic heart defect. This means there is decreased oxygen in the blood that is pumped from the heart to the rest of the body.
In normal hearts, blood that returns from the body goes through the right side of the heart and pulmonary artery to the lungs to get oxygen. The blood then comes back to the left side of the heart and travels out the aorta to the body.
In TGA, venous blood returns normally to the heart through the right atrium. But, instead of going to the lungs to absorb oxygen, this blood is pumped out through the aorta and back to the body. This blood has not been recharged with oxygen and leads to cyanosis.
Symptoms appear at birth or very soon afterward. How bad the symptoms are depends on the type and size of additional heart defects (such as atrial septal defect, ventricular septal defect, or patent ductus arteriosus) and how much the blood can mix between the two abnormal circulations.