Transposition of the Great Vessels (TGV)

What is transposition of the great vessels (TGV)?

In transposition of the great vessels (arteries), the positions of the 2 main arteries of the heart are reversed.

The heart has 4 chambers. The upper chambers are called atria, and the lower chambers are called ventricles. The pulmonary artery normally carries oxygen-poor (blue) blood from the right ventricle to the lungs. The aorta normally carries oxygen-rich (red) blood from the left ventricle to the body.

In TGV, the aorta is connected to the right ventricle and carries blue blood to the body. The pulmonary artery is attached to the left ventricle and carries red blood back to the lungs.

Infants born with this condition can survive only if they have one or more "defects" that allow the blue and red blood to mix until they can have surgery. These defects are:

• a hole between the 2 upper chambers (an atrial septal defect, or ASD)
• a hole between the 2 lower chambers (a ventricular septal defect, or VSD)
• a vessel connecting the lung artery with the aorta (a patent ductus arteriosus, or PDA).

How does it occur?

When the heart was being formed before birth, the pulmonary artery and aorta did not line up properly. Infants with TGV are born that way. No one knows what causes it.

What are the symptoms?

Babies with this condition look blue (cyanotic) right after birth. This is because their blood is not mixing enough to provide the oxygen their bodies need. Oxygen rich blood must reach the body in order for the infant to survive.

How is it diagnosed?

An oxygen monitor placed on the infant's hand or foot will show that the oxygen level in the blood is low. The baby will have an echocardiogram. An echocardiogram is a test that uses ultrasound to create pictures of the structure of the heart. This test shows if the pulmonary artery and the aorta are transposed.

How is it treated?

TGV may need to be treated in stages. The first procedure is called an atrial septostomy. Using cardiac catheterization, your doctor will thread a tube through a blood vessel to create or enlarge an opening between the 2 upper chambers. In some cases, a medicine is given to enlarge or open the small tube between the aorta and the pulmonary artery. That medicine will only work for a short time, however.

The 2 types of surgery used to correct the problem are:

• Arterial switch. In this procedure, the major arteries are switched to the proper position. The aorta is connected to the left ventricle so it will pump red blood to the body. The pulmonary artery is connected to the right pumping chamber so it pumps blue blood to the lungs. The arterial switch procedure must be performed within the first few days or weeks after birth.
• Venous switch or intra-atrial baffle. This operation, sometimes known as a Mustard or Senning operation, is usually done in early infancy. It creates a tunnel inside the upper chambers of the heart. This routes the red blood to the right ventricle and the blue blood to the left ventricle.

If there are other defects along with transposition, surgery becomes more complex.

What is the outlook after surgery?

Children who have had a successful repair of transposition of the great vessels generally lead normal, healthy lives. However, they may still have problems with heart rhythm or function. They need to visit a cardiologist at least once a year for the rest of their lives. They also need to need to take antibiotics to prevent infection of the heart when having dental work and certain other procedures.