Transposition of the great arteries
What is transposition of the great arteries (TGA)?
Transposition of the great arteries (TGA) is a birth defect of the heart in which the two main arteries—the aorta and the pulmonary artery—are in reversed positions (transposed).
A healthy heart is a strong, muscular pump that pushes blood through the circulatory system to carry oxygen and nutrients to the body. The heart has four chambers -- two on the right and two on the left. Blood is pumped through these chambers and regulated by valves that open and close like tiny doors, so that blood can move in only one direction.
After its trip through the body to deliver oxygen, blood is a blue color because it's no longer oxygen-rich. The blue blood returns to the heart through the right chambers and is pumped through the pulmonary artery into the lungs. In the lungs, it picks up more oxygen and becomes bright red. It then goes back through the pulmonary vein to the left chambers and is pumped through the aorta and out into the body again.
In a heart with TGA, the aorta is connected to the right side of the heart instead of the left, and the pulmonary artery is connected to the left side instead of the right. It's the exact opposite of a normal heart's structure.
Because of this, a two-circuit system occurs. Oxygen-rich blood moves through the left side of the heart and back into the lungs without getting to the rest of the body. Oxygen-poor blood moves through the right side of the heart and back to the body without passing through the lungs.
This can cause serious problems, such as:
- Hypoxia: A condition in which body tissues do not receive enough oxygen to be healthy.
- Pulmonary vascular obstructive disease: Difficulty breathing due to lung damage.
- Congestive heart failure: A condition in which the heart can no longer pump enough blood to meet the body's needs.
Typically, children born with TGA have an additional, related heart defect. It could be a hole in the wall between the chambers of the heart (ventricular septal defect or atrial septal defect) or a connection between the aorta and the pulmonary artery (patent ductus arteriosus). This other heart defect is actually needed for the child to survive, because it allows at least some mixing of oxygen-rich blood with oxygen-poor blood, which in turn means that some oxygen-rich blood circulates through the body and delivers necessary nutrients.
What causes transposition of the great arteries?
Transposition of the great arteries occurs during the first eight weeks of fetal development, when the heart is forming. This heart defect usually occurs with no clear cause.
Although the cause of TGA is unknown, several factors may increase the risk of a baby being born with this condition. These include: A mother who is over 40, has diabetes, or had a viral illness (such as measles) during pregnancy. Poor nutrition or alcohol abuse during pregnancy may also be a risk factor.
Children born with Down syndrome also are at increased risk of having transposition of the great arteries and other congenital heart defects. In addition, some congenital heart defects may have a genetic link, causing heart problems to occur more often in certain families.
TGA accounts for about 10-11% of all congenital heart defects.
What are the signs and symptoms of transposition of the great arteries?
The symptoms of transposition of the great arteries vary for each child, but may commonly include:
- Cyanosis: A blue tone to the skin, lips, or nails
- Pale, cool or clammy skin
- Rapid heart rate
- Difficulty breathing
- Lack of appetite and poor weight gain
Your doctor may look for a heart defect such as TGA if your baby has difficulty breathing or blue-tinged skin (cyanosis) after he or she is born.
In the vast majority of TGA cases, cyanosis is noted within the first few hours or days of your baby's life. However, if your baby has a large atrial or ventricular septal defect, the blood may receive enough oxygen that the bluish skin color won't be as noticeable in the beginning, but become apparent as your baby becomes more active.
Your baby's doctor may also suspect TGA if he or she hears a heart murmur — an abnormal whooshing noise, heard through a stethoscope exam, which may indicate a problem with blood flow. Most heart murmurs are called "innocent heart murmurs." Children with innocent heart murmurs do not have a heart defect and do not experience heart problems. However, if a heart murmur is present along with other symptoms, your doctor may want to investigate further by ordering other tests.
How is transposition of the great arteries diagnosed?
A clear diagnosis is the first step to treatment. A pediatric cardiologist (a children's heart doctor) can use several tests to confirm your child's diagnosis. These tests may include:
- Chest X-ray: A beam of electromagnetic energy creates images on film that show the inside structures of your baby's body. A chest X-ray doesn't provide a definitive diagnosis of TGA, but it helps the doctor determine your baby's heart size and the position of the aorta and pulmonary artery.
- Cardiac Magnetic Resonance Imaging (MRI): This test produces a three-dimensional image of the heart so you're your child's doctors can examine blood flow and functioning of the heart as it is working.
- Electrocardiogram (ECG or EKG): This test, conducted by attaching patches with wires (electrodes) to your baby's skin, records the heart's electrical activity. It will show if there are abnormal heart rhythms (arrhythmias or dysrhythmias) and/or stress on the heart muscle.
- Echocardiogram (Echo): This test uses sound waves to make a moving image of the heart on a video screen. It is similar to an ultrasound and can diagnose TGA by showing the structure and position of parts of the heart, as well as related heart defects like a ventricular septal defect or atrial septal defect.
- Cardiac catheterization: During this procedure, your doctor inserts a thin flexible tube (a catheter) into a blood vessel in the groin, then guides it up to the inside of the heart. A dye injected through the catheter makes the heart structures visible on x-ray pictures. The catheter also measures blood pressure and oxygen levels.
How is TGA treated?
Babies with TGA must have a connection (shunt) placed between the two circulatory systems in order to survive. Surgery within the first few weeks of life is usually needed to correct TGA.
Once diagnosed, your child's specific treatment may vary, depending on his or her individual needs. Your child may be admitted to the intensive care unit (ICU) or special care nursery as soon as symptoms are noted. He or she may be placed on a ventilator to help with breathing.
In some cases, a procedure called atrial septostomy may be done to broaden the connection between the heart's chambers and allow oxygen-rich and oxygen-poor blood to mix so that the body receives more needed oxygen. Intravenous (IV) medications may be given to help your baby's heart and lung function.
Usually, transposition of the great arteries is surgically corrected in the first month of life. Without corrective surgery, TGA is fatal in most cases within the first six months.
Procedures vary, but the most common is an arterial switch operation, in which your baby's surgeon moves the pulmonary artery and aorta to their normal positions and reattaches the coronary arteries to the aorta. If your baby has a ventricular septal defect or an atrial septal defect, those holes are usually closed up during the surgery. In some cases, however, small ventricular septal defects may be left to close on their own.
Many infants who undergo TGA surgical repair will grow and develop normally. However, your baby may need lifelong follow-up care with a cardiologist who can monitor his or her heart health for problems such as irregular heart rhythms, heart valve leaks, or narrowing of the arteries at their switch connections sites. The cardiologist may recommend that your child limit physical activity and take antibiotics before dental and surgical procedures to prevent infections.
About treatment for transposition of the great arteries at Children's
Hypoplastic left heart syndrome is treated through Children's cardiovascular program one of the largest and oldest pediatric cardiovascular programs in the region. Team members consistently achieve treatment results that are among the best in the nation. Each year, care is provided for thousands of the region¹s sickest children with heart conditions, including fetuses, newborns, infants, children, adolescents, and adult, long-term patients with pediatric cardiovascular conditions.
For more information, please call Children's Heart Clinic at 1-800-938-0301.
(From Pritchet & Hull Assoc., Inc.)
Heart with transposition of the great arteries with intact ventricular septum
(From Pritchet & Hull Assoc., Inc.)
Heart with transposition of the great arteries – arterial switch operation
(From Pritchet & Hull Assoc., Inc.)