Transposition of the great arteries (TGA) is a heart condition that is present at birth, and often is called a congenital heart defect. TGA occurs when the two main arteries going out of the heart—the pulmonary artery and the aorta—are switched in position, or “transposed”.
Normally, blood returning to the heart from the body is pumped from the right side of the heart through the pulmonary artery to the lungs. There, it receives oxygen and returns to the left side of the heart. Then, the oxygen-rich blood is pumped from the left side of the heart through the aorta to the body. In TGA, blood returning from the body bypasses the lungs and is pumped back out to the body. This occurs because the main connections are reversed. The pulmonary artery, which normally carries oxygen-poor blood from the right side of the heart to the lungs, now arises from the left side and carries oxygen-rich blood returning from the lungs back to the lungs. The aorta, which normally carries blood from the left side of the heart to the body, now arises from the right side and carries oxygen-poor blood back out to the body. The result of transposition of these two vessels is that too little oxygen is in the blood that is pumped from the heart to the rest of the body.
TGA might also be referred to as transposition of the great vessels (TGV), but TGA is the more common term.
Because the main arteries are switched, there are two separate blood circulations instead of a single connected one. Thus, blood with oxygen from the lungs does not get to the rest of the body. This means that TGA is a cyanotic (lacking oxygen) heart defect that leads to a bluish-purple coloring of the skin and shortness of breath.
Symptoms appear at birth or very soon afterwards. How bad the symptoms are depends on whether there is a way for the two separate blood circuits to mix, allowing some oxygen-rich blood to get out to the body. This mixing can occur through other defects, such as a hole between the bottom chambers of the heart (a ventricular septal defect), or through a shunt that normally is present at birth. Symptoms also can depend on whether other defects are present as well. Common symptoms of TGA include:
Surgery might be needed shortly after birth. In most hospitals, a type of surgery called an arterial switch procedure can be used to permanently correct the problem within the first week of life.