About Transposition of the great arteries

Transposition of the great arteries is a heart defect present at birth (congenital), in which the two main arteries leaving the heart are reversed (transposed). The condition 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 at birth or within the first few weeks of life.

Corrective surgery within the first weeks of life is the usual treatment. Having a baby with transposition of the great arteries is naturally worrisome to you as a parent. Remember that with proper treatment, most babies with congenital heart defects grow up to lead healthy, productive lives.

Symptoms

Typical signs and symptoms of transposition of the great arteries include:

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

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.

A normal heart has four chambers. 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. Transposition of the great arteries is the most common cyanotic heart defect.

One or more connections needed
In order to survive, infants born with transposition of the great arteries must have a conduit — an additional heart defect such as a hole in the wall between the chambers of the heart (ventricular septal defect or atrial septal defect) or a surgically created channel — that allows some mixing of oxygen-rich blood with the oxygen-poor blood. Some babies will need medications to keep these connections open or a procedure to create or enlarge an atrial septal defect to increase the amount of oxygen delivered to the body.

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

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. These include:

  • A mother who had rubella (German measles) or another viral illness during pregnancy
  • A parent who had transposition of the great arteries or another congenital heart defect
  • Poor nutrition during pregnancy
  • Excessive alcohol consumption during pregnancy
  • A mother older than 40
  • A mother who has diabetes
  • Down syndrome in the baby, which increases the risk of transposition of the great arteries and other congenital heart defects

Diagnosis

After your baby is born, his or her doctor may 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.

If your baby has a large atrial septal defect or ventricular septal defect, the blood may have enough oxygen initially that the bluish skin color won’t be very noticeable. But, as your baby becomes more active, 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 assessing 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 assess 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.

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).
  • Congestive heart failure. Unless there’s some mixing of oxygen-rich blood and oxygen-poor blood within the body, congestive heart failure — a condition in which the heart can’t pump enough blood to meet the body’s needs — may develop.
  • Pulmonary vascular obstructive disease. This condition causes damage to the lungs, making breathing difficult.

Without corrective surgery, transposition of the great arteries is fatal in most cases during the first six months of life.

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

  • Leaky heart valves
  • Problems with the arteries that supply the heart muscle with blood (coronary arteries)
  • Heart rhythm abnormalities (arrhythmias)
  • Decline in function of the heart muscle or heart valves

Preventive antibiotics
People with congenital heart defects are at increased risk of endocarditis, an infection of the inner lining of the heart. If your child is waiting to have corrective surgery, your child’s doctor will likely recommend preventive antibiotics before certain dental and other procedures. After corrective surgery, your child’s doctor can offer guidance on whether to continue with preventive antibiotics or not.

Pregnancy
It’s possible to have a healthy pregnancy if the transposition has been repaired. 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 you as the mother.

Treatment

All infants with transposition of the great arteries require 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 E-1 helps keep open the ductus arteriosus — a connection between the aorta and pulmonary artery — to increase blood flow and improve mixing of oxygen-poor and oxygen-rich blood.
  • 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 correct 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.

    The atrial switch was used frequently beginning in the 1960s. Since the 1980s, however, it has been largely replaced by the arterial switch operation because the latter is not associated with many of the long-term complications of the atrial switch, such as arrhythmias, 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 limit physical activity. Your child may need to take antibiotics before dental procedures and other surgical procedures to prevent infections.

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.

Prevention

In most cases, transposition of the great arteries cannot 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.

Caring for a baby with a serious heart problem, 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 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 to lead healthy, productive lives.