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.

Diagnosis

Transposition of the great arteries is most often diagnosed after a baby is born. But sometimes the condition may be seen before birth during a routine pregnancy ultrasound. If so, an ultrasound of the unborn baby's heart may be done to confirm the diagnosis. This test is called a fetal echocardiogram.

After birth, a health care provider may think about a diagnosis of a TGA if the baby has blue or gray skin, a weak pulse, or trouble breathing. The care provider may hear a heart sound, called a murmur, while listening to the baby's heart.

Tests

Tests are needed to confirm a diagnosis of transposition of the great arteries. They may include:

• Echocardiogram. This test uses sound waves to create moving pictures of the beating heart. It shows how blood flows through the heart, heart valves and blood vessels. It can show the positions of the two main arteries leaving the heart. An echocardiogram also can show if there are other heart problems present at birth, such as a hole in the heart.
• Chest X-ray. A chest X-ray shows the condition of the heart and lungs. It can't diagnose TGA by itself, but it does help the health care provider see the heart's size.
• Electrocardiogram (ECG or EKG). This simple, painless test records the electrical activity of the heart. Sticky patches called electrodes are placed on the chest and sometimes the arms and legs. Wires connect the electrodes to a computer, which displays the test results. An ECG can show if the heart is beating too fast, too slow or not at all.

Treatment

All infants with complete transposition of the great arteries (D-TGA) need surgery to correct the heart problem. Treatment for congenitally corrected transposition (L-TGA) depends on when the condition is diagnosed and what other heart conditions exist.

Medications

Before surgery is done to fix the switched arteries, a medicine called alprostadil (Caverject, Edex, others) may be given to the baby. This medicine increases blood flow. It helps oxygen-poor and oxygen-rich blood better mix together.

Surgery or other procedures

Surgery for transposition of the great arteries (TGA) is usually done within the first days to weeks after birth. Options depend on the type of TGA. Not all people with congenitally corrected transposition need surgery.

Surgeries and other treatments used to treat transposition of the great arteries may include:

• Atrial septostomy. This treatment may be done urgently as a temporary fix before surgery. It uses thin tubes and small cuts to widen a natural connection between the heart's upper chambers. It helps mix oxygen-rich and oxygen-poor blood, improving oxygen levels in the baby's body.
• Arterial switch operation. This is the most common surgery used to correct transposition of the great arteries. During this surgery, the two main arteries leaving the heart are moved to their correct positions. Other heart problems present at birth may be repaired during this surgery.
• Atrial switch operation. The surgeon splits blood flow between the heart's two upper chambers. After this surgery, the right lower heart chamber must pump blood to the body, instead of just to the lungs.
• Rastelli procedure. This surgery may be done if a baby with TGA also has a hole in the heart called a ventricular septal defect. The surgeon patches the hole and redirects blood flow from the left lower heart chamber to the aorta. This lets oxygen-rich blood go to the body. An artificial valve connects the right lower heart chamber to the lung artery.
• Double switch procedure. This complex surgery is used to treat congenitally corrected transposition. It redirects blood flow coming into the heart. It switches the great artery connections so the left lower heart chamber can pump oxygen-rich blood to the aorta.

Babies born with TGA often have other heart problems. Other surgeries may be needed to fix those heart problems. Surgery also may be needed to treat complications of TGA. If TGA causes changes in the heartbeat, a device called a pacemaker may be recommended.

After surgery to fix TGA, lifelong care is needed with a provider trained in heart problems present at birth. This type of health care provider is called a congenital cardiologist.

Coping and support

Caring for a baby with a serious heart condition, such as transposition of the great arteries, can be challenging. Here are some tips that might be helpful:

• Seek support. Ask for help from family members and friends. Talk with your baby's health care providers about support groups and other types of assistance that are available near you.
• Record the baby's health history. Write down the diagnosis, medicines, surgery and other treatments. Include the dates of treatment or surgery and the health care providers' names and numbers. This record will be helpful for health care providers who are unfamiliar with your baby's health history.
• Encourage safe activities. After surgery to fix TGA, some high-energy activities might need to be avoided. Talk with a health care provider about which exercises or activities are safe.

Every situation is different. But due to advances in surgical treatment, most babies with transposition of the great arteries grow up to lead active lives.

Preparing for an appointment

If your baby has transposition of the great arteries (TGA), you'll likely have appointments with several types of health care providers. For example, you'll usually see a provider trained in heart problems present at birth, called a congenital cardiologist. Here's some information to help you prepare for the appointments.

What you can do

• Get a complete family history for both sides of your family. Ask if anyone in your family was born with a heart problem.
• Take a family member or friend with you, if possible. Sometimes it can be difficult to remember all of the information provided to you. Someone who goes with you may be able to remember details.
• Write down questions to ask the health care provider.

For transposition of the great arteries, some basic questions to ask the health care provider include:

• Does my baby need surgery?
• What other treatments are available, and which do you recommend?
• How often are checkups needed after surgery?
• After surgery, will there be any remaining health concerns?
• Are there any activity restrictions?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend?

Don't hesitate to ask other questions you have.

What to expect from your doctor

Your health care provider is likely to ask you a number of questions, such as:

• Is there a family history of heart problems at birth?
• Were there any known pregnancy complications?
• Does the person have blue or gray skin, difficulty feeding, or trouble breathing?
• Does the person have shortness of breath, swelling of the legs or irregular heartbeats?