Transposition of the great arteries

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).

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), 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.

Symptoms

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.

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 (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.

Risk factors

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

Complications

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.

Prevention

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.

Diagnosis

Transposition of the great arteries is most often diagnosed after a baby is born. However, signs of the condition may be detected before birth during a routine pregnancy ultrasound. If so, a fetal echocardiogram may be recommended. A fetal echocardiogram uses sound waves to create detailed images of the unborn baby's heart. It can help a health care provider confirm the diagnosis of transposition of the great arteries.

After birth, a health care provider may suspect a heart defect such as transposition of the great arteries if the baby has blue skin, a weak pulse or trouble breathing.

The care provider may also suspect a heart problem if an irregular whooshing sound (heart murmur) is heard when listening to the baby's heart.

Tests

A physical exam alone can't accurately diagnose transposition of the great arteries. One or more of the following tests are necessary for an accurate diagnosis:

• Echocardiogram. An echocardiogram is an ultrasound of the heart. It uses sound waves to create moving images of the heart in motion. An echocardiogram can show the position of the aorta and the pulmonary artery. The test can also identify other associated congenital heart defects, such as a ventricular septal defect, atrial septal defect or patent ductus arteriosus.
• Chest X-ray. Although a chest X-ray doesn't provide a definitive diagnosis of transposition of the great arteries, it does allow the provider to see the baby's heart size and determine if blood flow is collecting in the lungs.
• Electrocardiogram (ECG or EKG). This simple, painless test records the electrical activity of the heart. Sticky patches (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 congenital heart defect. Treatment for congenitally corrected transposition (L-TGA) depends on when the condition is diagnosed and what other heart conditions exist.

The baby's care provider may recommend medications or a catheter procedure to help manage the condition before corrective surgery.

Medications

Before surgery for transposition of the great arteries, a medication called alprostadil (Caverject, Edex, others) may be given to increase blood flow and improve mixing of oxygen-poor and oxygen-rich blood.

Surgery or other procedures

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

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

• Atrial septostomy. This catheter procedure may be done urgently as a temporary treatment. The procedure, also called balloon atrial septostomy, widens a natural connection between the heart's upper chambers (atria). It helps mix oxygen-rich and oxygen-poor blood, increasing oxygen delivery to the baby's body.

• Arterial switch operation. This is the most common surgery used to correct transposition of the great arteries. During an arterial switch operation, the pulmonary artery and the aorta are moved to their correct positions. The pulmonary artery is connected to the right ventricle, and the aorta is connected to the left ventricle. The heart arteries also are reattached to the aorta.

  If your baby also has a ventricular septal defect or an atrial septal defect, those holes usually are closed during surgery. But sometimes a heart surgeon may leave small ventricular septal defects to close on their own.

• Atrial switch operation. In this surgery, the surgeon divides blood flow between the heart's two upper chambers (atria). Oxygen-rich blood coming back to the heart from the lungs is directed to the right lower chamber (right ventricle), which then pumps the blood to the aorta. The oxygen-poor blood returning to the heart from the body is directed to the left lower chamber (left ventricle), where it's pumped to the pulmonary artery.

  After the atrial switch procedure, the right ventricle must pump blood to the body, instead of just to the lungs as it would do in a typical heart. Possible complications of the atrial switch operation include irregular heartbeats, obstructions or leaks, and heart failure due to long-term reduced pumping function.

• Rastelli procedure. This procedure may be recommended if a baby has a ventricular septal defect with transposition of the great arteries. The surgeon closes the hole (septal defect) in the heart using a synthetic patch and redirects blood flow from the left ventricle to the aorta, allowing the oxygen-rich blood to go to the body. The connection between the left ventricle and the pulmonary artery is disrupted. A connection is then made with an artificial valve from the right ventricle to the artery connected to the lungs (pulmonary artery).
• Double switch procedure. This complex surgical procedure is used to treat congenitally corrected transposition. It redirects blood flow coming into the heart and switches the great artery connections, with the goal of placing the left lower heart chamber (ventricle) in the position to pump oxygen rich blood to the aorta.

Additional surgeries may be needed to correct other heart conditions, such as ventricular septal defect or pulmonary outflow obstruction. A pacemaker may be needed if transposition of the great arteries causes a disruption in heart signaling (heart block).

Some complications of transposition of the great arteries, such as irregular heart rhythms (arrhythmias) or heart valve problems may require additional treatment.

After treatment

After corrective surgery for transposition of the great arteries, the person will need lifelong follow-up care with a heart doctor (cardiologist) who specializes in congenital heart disease.

• Strenuous activity. The cardiologist may recommend avoiding certain activities, such as weightlifting or competitive sports, because they raise blood pressure and may stress the heart. Talk to your or your child's provider about what type and amount of activity is safe.

• Pregnancy. If you're thinking about becoming pregnant, talk to your cardiologist and obstetrician before conceiving. If you had surgery to correct transposition of the great arteries while a baby, it may be possible to have a healthy pregnancy, but specialized care may be needed.

  Complications of transposition of the great arteries, such as irregular heart rhythms or serious heart muscle problems, may make pregnancy risky for both mom and the unborn baby. In some situations, such as for women who have severe complications of their heart defect, pregnancy isn't recommended even for those with a repaired transposition.

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 strategies that may help make it easier:

• Seek support. Ask for help from family members and friends. Talk with your child's cardiologist about support groups and other types of assistance that are available near you.
• Record your or your baby's health history. Write down the diagnosis, medications, surgery, and other procedures and the dates they were performed, along with any doctor's names and numbers. This record will be helpful for health care providers who are unfamiliar with your or your baby's health history.
• Encourage safe activities. After corrective surgery, you or your child may need to avoid certain types of vigorous activities. Talk with the cardiologist about which activities are safe. If some are off-limits, encourage other pursuits rather than focusing on what can't be done.

Every circumstance 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 a care provider suspects transposition of the arteries, you or your child will be referred to a cardiologist for diagnosis and treatment.

What you can do

• Get a complete family history for both sides of your family. Ask if anyone in your family has had a congenital heart defect or congenital heart disease.
• 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 recall information if you forget some 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:

• What treatments are available, and which do you recommend?
• After surgery, will there be any lingering 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?

In addition to the questions that you've prepared to ask your health care provider, don't hesitate to ask questions during your appointment if you don't understand something.

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 disease at birth?
• Were there any known pregnancy complications?
• Have you noticed that your baby has blue skin, difficulty feeding or difficulty breathing?
• If you are the patient, have you had shortness of breath, swelling of the legs or irregular heartbeats?

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