Overview
Transposition of the great arteries
Transposition of the great arteries
In transposition of the great arteries, the main arteries leading away from the heart — the aorta and the pulmonary artery — are switched, also called transposed.
Transposition of the great arteries, also called TGA, is a serious, rare heart condition in which the two main arteries leaving the heart are switched. The condition is present at birth. That means it's a congenital heart defect.
Types
There are two types of transposition of the great arteries:
- Transposition of the great arteries, also called dextro-transposition of the great arteries (d-TGA). This type lowers the amount of oxygen-rich blood to the body. It's often diagnosed during pregnancy or soon after birth. Without treatment, serious complications or death can happen.
- Congenitally corrected transposition, also called levo-transposition of the great arteries (l-TGA or ccTGA). This is a less common type. Symptoms may not be seen right away. Treatment also depends on the specific heart structure and if there are other heart conditions.
Surgery to fix the positions of the arteries is the usual treatment. The surgery is usually done soon after birth.
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Symptoms
Symptoms of transposition of the great arteries include:
- Blue or gray skin due to low oxygen levels. Depending on skin color, these color changes may be harder or easier to see.
- Pounding heartbeat.
- Weak pulse.
- Lack of appetite.
- Poor weight gain.
Some people with the congenitally corrected type of TGA may not have symptoms for many years.
Also, skin color changes may not be seen right away if a baby with TGA also has other heart changes that let some oxygen-rich blood move through the body. But as the baby becomes more active, less oxygen-rich blood flows through the body. The changes in skin color become more noticeable as oxygen levels drop.
When to see a doctor
Serious congenital heart defects are often diagnosed before or soon after a child is born.
Get help right away if a child has trouble breathing.
Also get emergency medical help for anyone who has blue or gray skin or nails. Low oxygen levels can cause this change in skin color. Depending on skin color, the changes may be harder or easier to see.
Causes
Transposition of the great arteries, also called TGA, happens during pregnancy when the unborn baby's heart is forming. An unborn baby also is called a fetus. The cause is most often not known.
To understand TGA, it may help to know how the heart usually pumps blood. The typical heart has four chambers.
- The two upper chambers are called the atria.
- The two lower chambers are called the ventricles.
The artery that carries blood from the heart to the lungs is called the pulmonary artery. It connects to the heart's lower right chamber, called the right ventricle.
The right side of the heart moves blood to the lungs. In the lungs, blood picks up oxygen and then returns it to the heart's left side. The left side of the heart then pumps the blood through the body's main artery, called the aorta. The blood then goes out to the rest of the body.
Transposition of the great arteries, also called d-TGA
In this condition, also called dextro-transposition of the great arteries (d-TGA), the position of the two arteries leaving the heart is switched. 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. Usually, oxygen-poor blood flows through the right side of the heart to the lungs to get oxygen. In d-TGA, the oxygen-poor blood goes from the right side of the heart to the aorta and the rest of the body. The oxygen-rich blood goes back into the lungs without being pumped to the rest of the body. Unless there also is a hole in the heart, such as an atrial septal defect, that lets the blood mix, the body does not get oxygen-rich blood. This is life-threatening.
Congenitally corrected transposition, also called ccTGA or l-TGA
In this less common type, also called levo-transposition of the great arteries, 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 the right way through the heart and body. But the heart can have long-term trouble pumping blood. People with l-TGA also may have changes with the tricuspid heart valve such that it does not work as well.
Risk factors
Possible risk factors for congenital heart defects such as transposition of the great arteries include:
- Rubella, also called German measles. Having rubella during pregnancy can cause changes in an unborn baby's heart development. A blood test done before pregnancy can determine if you're immune to rubella. A vaccine is available if you aren't.
- Some medicines. Taking certain medicines during pregnancy can cause congenital heart defects and other health conditions present at birth. Always tell your healthcare team about the medicines you take.
- Alcohol use. Drinking alcohol during pregnancy raises the risk of congenital heart defects in the baby.
- Smoking. If you smoke, quit. Smoking during pregnancy can be harmful to the unborn baby, also called a fetus.
- Diabetes. Careful control of blood sugar before and during pregnancy can reduce the risk of congenital heart defects in the baby. Diabetes that develops during pregnancy is called gestational diabetes.
Complications
Complications depend on the type of transposition of the great arteries. Possible complications of complete transposition of the great arteries may include:
- Not enough oxygen to body tissues. Unless there's some mixing of oxygen-rich blood and oxygen-poor blood within the heart, this complication causes death.
Possible complications of congenitally corrected transposition, also called l-TGA, may include:
- Complete heart block. Transposition of the great arteries can change the way electrical signals move through the heart and 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, called the tricuspid valve, may not close all the way. Blood might flow backward. This condition is called tricuspid valve regurgitation. It can make it harder for the heart to pump blood.
- Heart failure. The heart can't pump enough blood to meet the body's needs. Heart failure may happen over time in l-TGA because the right lower heart chamber is pumping under higher pressure than usual. The strain may make the muscle of the right lower chamber weak.
Pregnancy and TGA
If you had transposition of the great arteries and want to become pregnant, talk with your healthcare professional. It may be possible to have a healthy pregnancy. But special care may be needed.
Complications of TGA, such as changes in heart signaling, may make pregnancy risky. Pregnancy isn't recommended for people who have severe complications of TGA, even if they had surgery to fix the heart condition.
Prevention
Because the exact cause of most congenital heart defects is not known, it may not be possible to prevent these conditions.
If you have a family history of heart conditions present at birth, talk with a genetic counselor and a healthcare professional trained in congenital heart defects before getting pregnant.
It's important to take steps to have a healthy pregnancy. Get proper prenatal care. Before becoming pregnant, get recommended immunizations. Start taking a multivitamin with folic acid. Folic acid has been shown to prevent harmful changes in the unborn baby's brain and spinal cord. It also may help reduce the risk of congenital heart defects.