Congenitally Corrected Transposition of the Great Arteries

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Corrected transposition of the great arteries (c-TGA) is a complex and unusual abnormality occurring in fewer than 1 percent of people with congenital (present at birth) heart disease. It occurs in males twice as often as females.

The condition is actually a combination of two heart abnormalities that cancel each other out, resulting in a condition in which the circulation of blood through the body is "correct." That is, oxygen-poor blood from the body ends up going into the lungs to pick up oxygen and oxygen-rich blood from the lungs goes out to nourish the body.

It seems like a case of two "wrongs" making "right," and while about 1 percent of people with this condition may go through life with no ill effects, the majority develop associated conditions that require treatment. They must remain under the care of a cardiologist throughout their lives.

Description of Congenitally Corrected Transposition of the Great Arteries

Congenitally — existing at birth
Corrected — blood flowing in correct direction
Transposition — reversed or switched
Great arteries — the aorta and pulmonary artery

Corrected transposition of the great arteries is a complex and unusual abnormality.

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In the normal heart, the right ventricle pumps (blue) blood to the pulmonary artery and lungs, and the left ventricle pumps (red) blood to the aorta and the body. The ventricle that pumps blood around the body's system is called the systemic ventricle. This is the "left" ventricle under normal circulstances. The "right" ventricle has a different structure than the left ventricle. The right ventricle normally pumps blood to the lungs and works at a low pressure (about 25 mmHg). The left ventricle normally pumps blood to the body and therefore pumps at whatever pressure your blood pressure is (about 120 mmHg).

In congenitally corrected transposition, the position of the two ventricles is reversed so that the right atrium connects to the left ventricle; and the left atrium connects to the right ventricle. The two great arteries (the aorta and pulmonary artery) therefore arise from the wrong ventricle. In other words, the aorta arises from the right ventricle and sends blood around the body; and the pulmonary artery arises from the left ventricle and takes blood to the lungs. You will note, however, that with this arrangement, while the blood is flowing through the wrong ventricles, it is still going in the correct direction, hence the term "congenitally corrected transposition."

The medical terms for this arrangement are atrioventricular discordance (since the atria are connected to the opposite ventricles) and ventriculo-arterial discordance (since the ventricles give rise to the opposite artery). It is sometimes called "ventricular inversion."

Additional problems within the heart are common in people with transposition of the great arteries. For people who have no associated heart defects, the condition may not cause much of a problem except that the chest X-ray or electrocardiogram may look abnormal (because of the unusual position of the ventricles and arteries). With time, since the right ventricle is not built to pump to such a high pressure, the right ventricle may weaken, dilate, and cause fatigue or breathlessness.

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