Transposition of the great arteries

Definition

Transposition of the great arteries is a rare heart defect present at birth (congenital), in which the two main arteries leaving the heart are reversed (transposed). Transposition of the great arteries changes the way blood circulates through the body, leaving a shortage of oxygen in blood flowing from the heart to the rest of the body. Without an adequate supply of oxygen-rich blood, the body can't function properly.

Transposition of the great arteries is usually detected within the first few weeks of life.

Corrective surgery soon after birth is the usual treatment for transposition of the great arteries. Having a baby with transposition of the great arteries is naturally worrisome to you as a parent, but with proper treatment, the outlook is promising.

Transposition of the great arteries

Transposition of the great arteries

In transposition of the great arteries, the placement of the main arteries leading away from the heart — the aorta and the pulmonary artery — is switched (transposed)....

Symptoms

Transposition of the great arteries symptoms include:

• Blue color of the skin (cyanosis)
• Shortness of breath
• Lack of appetite
• Poor weight gain

When to see a doctor
Transposition of the great arteries is often detected as soon as your baby is born or during the first week of life. If signs and symptoms didn't appear in the hospital, seek prompt medical help if you notice that your baby has developed any transposition of the great arteries symptoms.

Causes

Transposition of the great arteries occurs during fetal growth when your baby's heart is developing. Why this defect occurs is unknown in most cases.

Normally, the pulmonary artery — which carries blood from your heart to your lungs to receive oxygen — is attached to the lower right chamber (right ventricle). From your lungs, the oxygen-rich blood goes to your heart's upper left chamber (left atrium), through the mitral valve into the lower left chamber (left ventricle). The aorta is normally attached to the left ventricle. It carries oxygen-rich blood out of your heart back to the rest of your body.

In transposition of the great arteries, the positions of the pulmonary artery and the aorta are switched. The pulmonary artery is connected to the left ventricle, and the aorta is connected to the right ventricle. Oxygen-poor blood circulates through the right side of the heart and back to the body without passing through the lungs. Oxygen-rich blood circulates through the left side of the heart and right back into the lungs without being circulated to the rest of the body.

Circulation of oxygen-poor blood through the body causes the skin to have a blue tint (cyanosis). Because of this, transposition of the great arteries is called a congenital cyanotic heart defect.

Although some factors, such as rubella or other viral illnesses during pregnancy, maternal age over 40, or maternal diabetes, may increase the risk of this condition, in most cases the cause is unknown.

Chambers and valves of the heart

Chambers and the valves of the heart

A normal heart has two upper and two lower chambers. The upper chambers, the right and left atria, receive incoming blood. The lower chambers, the more muscular right and left ventricles, pump blood ...

Transposition of the great arteries

Transposition of the great arteries

In transposition of the great arteries, the placement of the main arteries leading away from the heart — the aorta and the pulmonary artery — is switched (transposed)....

Risk factors

Although the exact cause of transposition of the great arteries is unknown, several factors may increase the risk of a baby being born with this condition, including:

• A history of German measles (rubella) or another viral illness in the mother during pregnancy
• A family history of transposition of the great arteries or another congenital heart defect
• Poor nutrition during pregnancy
• Excessive alcohol consumption during pregnancy
• A mother older than age 40
• A mother who has poorly controlled diabetes
• Down syndrome in the baby

Complications

Potential complications of transposition of the great arteries include:

• Lack of oxygen to tissues. Your baby's tissues may be getting too little oxygen (hypoxia).
• Heart failure. Unless there's some mixing of oxygen-rich blood and oxygen-poor blood within the body, heart failure — a condition in which the heart can't pump enough blood to meet the body's needs — may develop.
• Lung damage. The lack of oxygenated blood causes damage to the lungs, making breathing difficult.

Severe cases of transposition of the great arteries may be fatal in as few as six months if corrective surgery isn't done.

Babies who have surgery to correct transposition of the great arteries sometimes have the following associated conditions later in life:

• Leaky heart valves
• Narrowing of the arteries that supply blood to the heart (coronary arteries)
• Heart rhythm abnormalities (arrhythmias)
• Heart muscle weakness or stiffness leading to heart failure

Preparing for your appointment

Your obstetrician or your child's doctor may suspect a congenital heart defect if your child has bluish skin from birth. You'll then be referred to a pediatric heart specialist (cardiologist) for diagnosis and treatment. You'll usually be introduced to the pediatric cardiologist while your baby is still in the hospital.

Here's some information to help you get ready, and what to expect from your doctor.

What you can do

• Get a complete family history for both sides of your baby's family. Find out if anyone in your child's family was ever born with a heart defect.
• Ask a family member or friend to be with you, if possible. Sometimes it can be difficult to remember all of the information provided to you, and because you're so concerned about your baby, you may miss something the doctor says or you may forget some details.
• Write down questions to ask your doctor.

For transposition of the great arteries, some basic questions to ask your doctor include:

• What caused this to happen to my baby?
• What treatments are available, and which do you recommend?
• What happens if my baby doesn't have the surgery?
• After surgery, will my baby have any lingering problems?
• Will my child have any activity restrictions?
• How can I prevent this from happening in future pregnancies?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment anytime you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions, such as:

• Is there a family history of heart disease at birth?
• Did you experience any significant illnesses or take medications while pregnant?
• Have you noticed that your baby has bluish skin, difficulty feeding or difficulty breathing?

Tests and diagnosis

After your baby is born, his or her doctor will immediately suspect a heart defect such as transposition of the great arteries if your baby has blue-tinged skin (cyanosis) or if your baby is having trouble breathing.

Sometimes, the bluish skin color isn't as noticeable if your baby has another heart defect, such as a large atrial septal defect or ventricular septal defect, that's allowing some oxygen-rich blood to travel through the body. The septum is the wall separating the left and right sides of the heart. Sometimes, babies are born with holes in the septum. If the hole is in the upper chambers of the heart, it's called an atrial septal defect. In the lower chambers of the heart, the defect is called a ventricular septal defect. As your baby becomes more active, the heart defects won't allow enough blood through and eventually the cyanosis will become obvious.

Your baby's doctor may also suspect a heart defect if he or she hears a heart murmur — an abnormal whooshing sound caused by turbulent blood flow.

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

• Echocardiography. An echocardiogram is an ultrasound of the heart — it uses sound waves that bounce off your baby's heart and produce moving images that can be viewed on a video screen. Doctors use this test to diagnose transposition of the great arteries by looking at the position of the aorta and the pulmonary artery. Echocardiograms can also identify associated heart defects, such as a ventricular septal defect or an atrial septal defect.
• Chest X-ray. Although a chest X-ray doesn't provide a definitive diagnosis of transposition of the great arteries, it does allow the doctor to see your baby's heart size and see the position of the aorta and pulmonary artery.
• Electrocardiogram. An electrocardiogram records the electrical activity in the heart each time it contracts. During this procedure, patches with wires (electrodes) are placed on your baby's chest, wrists and ankles. The electrodes measure electrical activity, which is recorded on paper.
• Cardiac catheterization. Because of its invasive nature, this procedure is typically done only when other tests, such as echocardiography, don't yield enough information to make a diagnosis. During a cardiac catheterization, the doctor inserts a thin flexible tube (catheter) into an artery or vein in your baby's groin and weaves it up to his or her heart. A dye is injected through the catheter to make your baby's heart structures visible on X-ray pictures. The catheter also measures pressure in the chambers of your baby's heart and in the blood vessels.

Treatments and drugs

All infants with transposition of the great arteries need surgery to correct the defect.

Before surgery
Your baby's doctor may recommend several options to help manage the condition before corrective surgery. They include:

• Medication. The medication prostaglandin E1 (Alprostadil) helps keep the connection between the aorta and pulmonary artery open, increasing blood flow and improving mixing of oxygen-poor and oxygen-rich blood until surgery can be performed.
• Atrial septostomy. This procedure — usually done using cardiac catheterization rather than surgery — enlarges a natural connection between the heart's upper chambers (atria). It allows for the oxygen-rich and oxygen-poor blood to mix and results in improved oxygen delivery to your baby's body.

Surgery
Surgical options include:

• Arterial switch operation. This is the surgery that doctors most often use to fix transposition of the great arteries. Doctors usually perform this surgery within the first month of life.

  During an arterial switch operation, the pulmonary artery and the aorta are moved to their normal positions: The pulmonary artery is connected to the right ventricle, and the aorta is connected to the left ventricle. The coronary arteries also are reattached to the aorta.

  If your baby has a ventricular septal defect or an atrial septal defect, those holes usually are closed during surgery. In some cases, however, the doctor may leave small ventricular septal defects to close on their own.

• Atrial switch operation. In this surgery, the surgeon makes a tunnel (baffle) between the heart's two upper chambers (atria). This diverts the oxygen-poor blood to the left ventricle and the pulmonary artery and the oxygen-rich blood to the right ventricle and the aorta. With this procedure, the right ventricle must pump blood to the entire body, instead of just to the lungs as it would do in a normal heart. Possible risks from the atrial switch operation include irregular heartbeats, baffle obstructions or leaks, and problems with right ventricle function.

After surgery
After corrective surgery, your baby will need lifelong follow-up care with a heart doctor (cardiologist) who specializes in congenital heart disease to monitor his or her heart health. The cardiologist may recommend that your child avoid certain activities, such as weightlifting, because they raise blood pressure and may stress the heart.

If your child had an atrial switch operation, he or she may need to take antibiotics before dental procedures and other surgical procedures to prevent infections. Those who've had the arterial switch operation generally won't need preventive antibiotics.

Many people who undergo the arterial switch operation don't need additional surgery. However, some complications, such as arrhythmias, heart valve leaks or problems with the heart's pumping, may require treatment.

Pregnancy
If you had transposition of the great arteries repaired in your infancy, it's possible for you to have a healthy pregnancy, but specialized care may be necessary. If you're thinking about becoming pregnant, talk to your cardiologist and obstetrician before conceiving. If you have complications such as arrhythmias or serious heart muscle problems, pregnancy may pose risks to both the mother and the fetus. In some situations, such as for women with severely reduced heart function, pregnancy isn't recommended even for those with a repaired transposition.

Coping and support

Caring for a baby with a serious heart problem, such as transposition of the great arteries, can be challenging and frightening. 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 baby's health history. You may want to write down your baby's diagnosis, medications, surgery and other procedures and the dates they were performed, your child's cardiologist's name and phone number, and any other important information about your baby's care. This record will help you recall the care your child has received, and it will be helpful for doctors who are unfamiliar with your baby to understand his or her health history.
• Talk about your concerns. You may worry about the risks of vigorous activity, even after your child has had corrective surgery. Talk with the cardiologist about which activities are safe for your child. If some are off-limits, encourage your child in other pursuits rather than focusing on what he or she can't do. If other issues about your child's health concern you, discuss them with your child's cardiologist, too.

Although every circumstance is different, remember that most children with congenital heart defects grow up healthy.

Prevention

In most cases, transposition of the great arteries can't be prevented. If you have a family history of heart defects or if you already have a child with a congenital heart defect, before getting pregnant consider talking with a genetic counselor and a cardiologist experienced in congenital heart defects.

Additionally, it's important to take steps to have a healthy pregnancy. For example, before becoming pregnant, be sure you're up to date on all of your immunizations, and start taking a multivitamin with 400 micrograms of folic acid.