Transposition of the great arteries (TGA) is a serious, rare heart problem in which the two main arteries leaving the heart are reversed (transposed). The condition is present at birth (congenital heart defect).
There are two types of transposition of the great arteries:
- Complete transposition of the great arteries, also called dextro-transposition of the great arteries (D-TGA), causes a shortage of oxygen-rich blood to the body. Symptoms are usually noticed during pregnancy, immediately after birth or within a few weeks of birth. Without treatment, serious complications or death can occur.
- Congenitally corrected transposition, also called levo-transposition of the great arteries (L-TGA), is a less common type of this condition. Symptoms may not be noticed right away. Treatment depends on the specific heart defects.
Corrective surgery soon after birth is the usual treatment for transposition of the great arteries.
Signs of transposition of the great arteries may be detected during certain routine screening tests done during pregnancy.
However, some people with congenitally corrected transposition of the great arteries may not have symptoms for many years.
Signs and symptoms of transposition of the great arteries after birth include:
- Blue color of the skin (cyanosis)
- Shortness of breath
- Weak pulse
- Lack of appetite
- Poor weight gain
A blue skin color may not be as noticeable in babies who are born with transposition of the great arteries and other congenital heart defects. This is because these other heart conditions — such as atrial septal defect, ventricular septal defect or patent ductus arteriosus — may allow some oxygen-rich blood to travel through the body. But as the baby becomes more active, the congenital heart defects won't allow enough blood through and eventually the blue skin color will become obvious.
When to see a doctor
Complete transposition of the great arteries is usually detected before birth, immediately after birth or within the first hours to weeks of life.
Always seek emergency medical help if you notice that anyone develops a blue coloring of the skin.
Transposition of the great arteries occurs during pregnancy when the baby's heart is developing. The cause is most often unknown.
To understand transposition of the great arteries, it may be helpful to know how the heart typically pumps blood.
- Usually, the artery that carries blood from the heart to the lungs (pulmonary artery) connects to the heart's lower right chamber (right ventricle).
- Oxygen-rich blood is then pumped from the lungs to the heart's upper left chamber (left atrium).
- Blood then flows into the lower left chamber (left ventricle).
- The body's main artery (aorta) typically connects to the left ventricle. It carries oxygen-rich blood out of the heart to the rest of the body.
Complete transposition of the great arteries (D-TGA)
In a complete transposition of the great arteries (also called dextro-transposition of the great arteries), the pulmonary artery and the aorta have switched positions. The pulmonary artery connects to the left ventricle, and the aorta is connected to the right ventricle.
As a result, oxygen-poor blood flows through the right side of the heart and back to the body without passing through the lungs. Oxygen-rich blood flows through the left side of the heart and directly back into the lungs without being pumped to the rest of the body.
Congenitally corrected transposition (L-TGA)
In this less common type, also called levo-transposition of the great arteries (L-TGA), the two lower heart chambers (ventricles) are switched. The left ventricle is on the heart's right side and receives blood from the right atrium, and the right ventricle is on the heart's left side and receives blood from the left atrium.
The blood usually flows correctly through the heart and body. The right-sided left ventricle attaches to the pulmonary artery, which delivers oxygen-poor blood to the lungs, while the left-sided right ventricle attaches to the aorta, which carries oxygen-rich blood to the body. Because the two chambers aren't exactly alike, the heart can have long-term difficulty pumping blood. People with L-TGA may also have problems with the tricuspid heart valve.
Several things may increase the risk of a baby being born with transposition of the great arteries, including:
- A history of German measles (rubella) or another viral illness in the mother during pregnancy
- Drinking alcohol or taking certain medications during pregnancy
- Smoking during pregnancy
- Poorly controlled diabetes in the mother during pregnancy
Transposition of the great arteries can contribute to other health concerns later in life. Complications depend on the type of transposition of the great arteries (TGA).
Potential complications of complete transposition of the great arteries (D-TGA) may include:
- Lack of oxygen to tissues. The body tissues receive too little oxygen (hypoxia). Unless there's some mixing of oxygen-rich blood and oxygen-poor blood within the body, this complication causes death.
- Heart failure. Heart failure is a condition in which the heart can't pump enough blood to meet the body's needs. It may develop over time because the right lower heart chamber (ventricle) is pumping under higher pressure than usual. The strain may make the muscle of the right ventricle stiff or weak.
Potential complications of congenitally corrected transposition (L-TGA) may include:
- Reduced heart pumping function. In L-TGA, the right lower heart chamber (right ventricle) is pumping blood to the body. This work is different from what the right ventricle was designed to do.
- Complete heart block. The changes in the structure of the heart due to L-TGA can disrupt the electrical signals that tell the heart to beat. A complete heart block occurs if all signals are blocked.
- Heart valve disease. Valves in the heart act as doorways to keep blood moving in one direction. In congenitally corrected transposition, the valve between the upper and lower heart chambers (tricuspid valve) may not close completely, causing blood to move backward. This condition is called tricuspid valve regurgitation. Regurgitation can eventually lead to reduced heart pumping function.
If you have a family history of congenital heart defects or if you already have a child with one, consider talking with a genetic counselor and a cardiologist experienced in congenital heart defects before getting pregnant.
It's important to take steps to have a healthy pregnancy. Before becoming pregnant, get up to date on all immunizations and start taking a multivitamin with 400 micrograms of folic acid.