Transposition of the great arteries

Overview

Transposition of the great arteries (TGA) is a serious, rare heart problem in which the two main arteries leaving the heart are reversed. The condition is present at birth, which means it's a congenital heart defect.

Types

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). This type reduces the amount 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). This is a less common type. Symptoms may not be noticed right away. Treatment depends on the specific heart problems.

Surgery to correct the positions of the arteries is the usual treatment. The surgery is usually done soon after birth.

Symptoms

Transposition of the great arteries (TGA) may be seen in a baby before birth during a routine pregnancy ultrasound.

But some people with the congenitally corrected type of TGA may not have symptoms for many years.

Symptoms of transposition of the great arteries after birth include:

• Blue or gray skin. Depending on the baby's skin color, these color changes may be harder or easier to see.
• Weak pulse.
• Lack of appetite.
• Poor weight gain.

Skin color changes may not be noticed right away if a baby with TGA also has other heart problems. This is because the other heart problems may let some oxygen-rich blood move through the body. But as the baby becomes more active, less blood flows through the body. The blue or gray skin color then becomes more noticeable.

When to see a doctor

Always seek emergency medical help if you notice that anyone develops a blue or gray skin color.

Causes

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 — called the pulmonary artery — connects to the heart's lower right chamber. That chamber is called the right ventricle.
• Oxygen-rich blood is then pumped from the lungs to the heart's upper left chamber, also called the left atrium.
• Blood then flows into the lower left chamber, known as the left ventricle.
• The body's main artery, called the 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 two arteries leaving the heart have switched positions. The pulmonary artery connects to the left lower heart chamber. The aorta connects to the right lower heart chamber.

The switched arteries cause changes in blood flow. Oxygen-poor blood now flows through the right side of the heart. It goes back to the body without passing through the lungs. Oxygen-rich blood now flows through the left side of the heart. It goes 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 are reversed.

• The lower left heart chamber, called the left ventricle, is on the heart's right side. It gets blood from the upper right heart chamber.
• The lower right heart chamber is on the heart's left side. It gets blood from the left upper heart chamber.

The blood usually still flows correctly through the heart and body. But the heart can have long-term trouble pumping blood. People with L-TGA may also have problems with the tricuspid heart valve.

Risk factors

Several things may increase a baby's risk of transposition of the great arteries, including:

• A history of German measles (rubella) or another infection by a virus during pregnancy.
• Drinking alcohol or taking certain medicines during pregnancy.
• Smoking during pregnancy.
• Poorly controlled diabetes during pregnancy.

Complications

Complications depend on the type of transposition of the great arteries (TGA).

Possible complications of complete transposition of the great arteries (D-TGA) may include:

• Not enough oxygen to body tissues. 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 is pumping under higher pressure than usual. The strain may make the muscle of the right lower chamber stiff or weak.

Possible complications of congenitally corrected transposition (L-TGA) may include:

• Reduced heart pumping. In L-TGA, the right lower heart chamber pumps blood to the body. This work is different from what that chamber was designed to do. This can cause changes in how well the heart pumps blood.
• Complete heart block. The changes in the structure of the heart due to L-TGA can change the electrical signals that tell the heart to beat. A complete heart block occurs if all signals are blocked.
• Heart valve disease. In L-TGA, the valve between the upper and lower heart chambers — the tricuspid valve — may not close completely. Blood might move backward through the valve. This condition is called tricuspid valve regurgitation. It can eventually reduce the heart's ability to pump blood.

Pregnancy and TGA

If you had transposition of the great arteries and want to become pregnant, talk with a health care provider first. It may be possible to have a healthy pregnancy, but special care may be needed.

Complications of TGA, such as changes in heart signaling or serious heart muscle problems, may make pregnancy risky. Pregnancy isn't recommended for people who have severe complications of TGA, even if they had surgery to fix the TGA.

Prevention

If you have a family history of heart problems present at birth, consider talking with a genetic counselor and a health care provider experienced in congenital heart defects before getting pregnant.

It's important to take steps to have a healthy pregnancy. Before becoming pregnant, get recommended immunizations and start taking a multivitamin with 400 micrograms of folic acid.