Transposition of the Great Arteries

A good way to understand this condition is to first think about how blood flows in the body. Arteries are blood vessels that carry blood away from the heart to other places in the body. The two largest of these arteries are called the great arteries. One of them, the pulmonary artery, takes blood from the heart to the lungs. In the lungs, oxygen is added to the blood. Then it goes back to the heart. From there, the other great artery delivers it to the rest of the body. This artery is called the aorta.

Sometimes, the great arteries get reversed. This is called transposition. The pulmonary artery is connected to the left side of the heart (instead of the right). The aorta is connected to the right side (instead of the left). This is a problem because the right side of the heart pumps blood to the lungs. The left side pumps it into the body. But the arteries have switched positions. So, blood that does not have enough oxygen in it gets pumped into the body. This causes cyanosis. The baby's skin or lips may look bluish. The baby may also have trouble breathing.

The arteries were reversed while the baby was developing in the mother's womb. Why it happens is usually not known. It is a called a congenital condition because the baby was born with it. Treatment needs to start right away and surgery will be needed. With good treatment, most babies born with transposed arteries can grow up to live fairly normal lives.

CAUSES

A baby's heart forms during the first 8 weeks in the mother's womb. Sometimes something goes wrong and things do not form like they should. This does not happen often. Transposition of the great arteries occurs in about 20 to 30 of every 100,000 newborns. The cause is usually not known, but some conditions (called risk factors) increase the chances that a baby will be born with the condition. They include:

  • Things that affected the baby's mother, such as:

  • Having diabetes (too much sugar in the blood).

  • Having a viral infection (caused by a virus) while pregnant. German measles (rubella) is an example.

  • Drinking a lot of alcohol while pregnant.

  • Being older than 40.

  • Genetics. Other members of the baby's family can have the condition. They could also have also been born with other heart problems (congenital).

  • Sex. The condition occurs much more often in baby boys than girls.

SYMPTOMS

Babies must have oxygen get to their bodies to survive. Most of the time, babies with transposed arteries do not have enough oxygen in their blood. But they usually have some. That is because they often are born with a connection between the right and the left sides of the heart. Sometimes this is a hole in the heart between the two sides. Other times, a blood vessel connects the great arteries. This blood vessel was used while the baby was in the womb and usually closes after birth. The holes can close after birth too, but they may stay open for some time after birth. How long they stay open and the size of the opening will affect the baby's symptoms. These connections effect how much mixing can take place between blood with oxygen and blood without it. Newborns with a very small opening may have symptoms at the time of birth. If the opening is bigger, symptoms may not show up for several days or even weeks. When symptoms do appear, they usually include:

  • Blue lips or skin.

  • Skin that is cool, pale and moist.

  • Rapid breathing.

  • Trouble breathing.

  • Rapid heartbeat.

  • Difficulty feeding.

  • Poor weight gain.

DIAGNOSIS

Some symptoms can be seen. Blue lips, for instance. Others cannot. To decide if a baby has transposition of the great arteries, the child's healthcare provider will probably:

  • Listen to the baby's heart. The caregiver may hear an unusual sound when the heart beats (heart murmur).

  • Order blood tests, such as:

  • A test that shows how many red blood cells are in the child's blood (complete blood count). These are the cells that carry oxygen.

  • A test that shows how much oxygen is being carried by the red blood cells (arterial blood gas test).

  • Order imaging tests. These take pictures of different parts of the body. They may include:

  • Chest X-ray. This can show if the heart is bigger than normal or has a specific shape.

  • Echocardiogram. This uses sound waves to create moving pictures of the heart.

  • Magnetic resonance imaging (MRI). It uses a computer and magnets to create pictures of the heart.

  • Order an electrocardiogram (EKG). This test measures the electrical activity of the heart. It can show if the heartbeat is unusual.

  • Do a cardiac catheterization. This procedure can give the child's caregivers a lot of information about the heart. A catheter (soft, thin tube) is put into a blood vessel that goes to the heart. Then, tests can be done to measure the oxygen and pressures inside the heart. Pictures can also be taken of the blood vessels by injecting a special dye.

TREATMENT

Treatment is a must. This can be a life-threatening condition in a newborn. Treatment usually includes:

  • Supportive care. Steps are taken to help the baby's body. For example:

  • A ventilator may be used. This is a machine to help the child breathe. A tube is put in the child's airway. It is attached to the machine. The ventilator makes sure the baby's lungs get enough oxygen.

  • Intravenous therapy (IV). Soft, plastic tubes are used to give the baby food and fluids. A needle is put into a blood vessel. It is connected to an IV tube. This is not painful for the child.

  • Medication may be given to keep the blood vessel that connects the left and right sides of the heart open. It would be given through an IV.

  • Cardiac catheterization. This may be done to make the hole bigger in the wall between the two sides of the heart. Or, a new opening can be made. A special catheter with a tiny balloon on the end is used. This lets the blood mix more until surgery can be done.

  • Surgery. This is usually done within a week or two after the child is born. The most common surgery is called an arterial switch operation. It is open-heart surgery.

  • An incision (cut) is made in the chest.

  • A heart-lung machine is used to do the work of the heart while the operation is taking place.

  • The aorta and the pulmonary artery (the two great arteries) are disconnected. Then they are connected to the proper sides of the heart.

  • The coronary arteries (the blood vessels that give oxygen to the heart muscle) are moved from one great artery to the other.

  • Any holes between the sides of the heart are closed.

  • The child is taken off the heart-lung machine.

  • The baby's heart begins to pump blood. Now, blood without oxygen goes to the lungs. And blood with oxygen goes out from the heart to the rest of the body.

  • Another type of surgery is called the Mustard or Senning procedure. These surgeries direct the blood with low oxygen to the pumping chamber that goes to the lungs. The surgery uses patches in the upper parts of the heart to redirect the blood to the correct chamber. A benefit of this surgery is that the great arteries are not moved and the coronary arteries are not disturbed. This type of surgery is usually for those babies or children who were not able to have the arterial switch surgery performed in the first few months of life.

PROGNOSIS

Methods and technology have improved a great deal in recent years. Today, most newborns that have the arterial switch surgery survive. The babies may have problems as they grow up. Scarring from surgery can cause problems. The arteries or patches sometimes become too narrow. Some children may develop unusual heartbeats or even need an electronic pacemaker. Some children may have some learning or behavior problems. All of them will need to be checked every year by a heart specialist. Even so, these problems can be managed. Most of the children should be able to grow up and lead fairly normal, productive lives.