Tetralogy of Fallot | Symptoms and Causes

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What is Tetralogy of Fallot (ToF)?

In a normal heart, oxygen-poor (blue) blood returns to the right atrium from the body and travels to the right ventricle. Then, it is pumped through the pulmonary artery into the lungs, where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle and then is pumped through the aorta out to the body.

But in ToF, the abnormal features prevent enough oxygen-poor (blue) blood from flowing to the lungs as it should. As a result, a person with ToF has a lower-than-normal amount of oxygen in the blood. Surgical intervention is needed.

In ToF, there are four cardiac anatomic characteristics:

  • Right ventricular outflow tract obstruction: The connection between the heart and the artery that goes to the lungs (pulmonary artery) is narrowed and blood flow to the lungs is reduced.
  • Overriding aorta: The major blood vessel from the heart to the body connects to the heart a bit further to the right than it normally does.
  • Hypertrophy of the right ventricle: The right-sided pumping chamber (ventricle) is thicker than normal because it’s pumping blood at a higher-than-normal pressure.

What is tetralogy of Fallot with pulmonary atresia (ToF/PA)?

ToF/PA is a more severe variant of ToF.

  • Babies with ToF/PA often show cyanosis (bluish tinge to skin) after birth, but in some cases this condition becomes apparent only at an older age. 
  • Surgery to repair or partially correct the defects is usually done within in the first six months of a baby’s life. Often, more than one operation is needed.

ToF/PA is a combination of cardiac anatomic characteristics:

  • Overriding aorta: moves toward right side of heart; located just over the ventricular septal defect
  • Hypertrophy of the right ventricle: becomes abnormally enlarged because it’s attempting to compensate for the pulmonary obstruction
  • No connection between the right ventricle and the pulmonary arteries: blood flow into the lungs is through blood vessels running from the aorta to the pulmonary arteries
  • Abnormal pulmonary arteries: The number, size and arrangement of pulmonary arteries are extremely variable in this disease. This often constitutes the biggest challenge for therapy since it may be necessary to connect multiple pulmonary arteries together and then to the right ventricle.

What are the symptoms of ToF?

  • Cyanosis is sometimes the first sign to be recognized. Cyanosis is marked by a blue color of the skin and mucus membranes due to a lower-than-normal amount of oxygen in the blood.
  • In many cases, a heart murmur—perhaps detected at a well-child visit—is the first sign of ToF. (Note: The overwhelming majority of murmurs in babies and older children are not associated with any cardiac abnormality.)
  • Congenital heart defects like ToF usually occur by chance, with no clear reason for their development. So, it’s difficult to predict who’s at risk. But in ToF, familial cases have been reported, and a genetic link has been confirmed in some cases.
  • Parents who have a child with a ToF (or another congenital heart defect) have a somewhat greater chance of having a second child with a heart defect.
  • Even after it’s apparent that a baby has ToF, there may be few symptoms for weeks or even months. A few babies will have signs of cardiac overwork—becoming tired with feeding, poor weight gain—if the amount of pulmonary obstruction is mild.
  • More commonly, the baby has few symptoms at first. But, over time, the cyanosis increases. Eventually, the cyanosis becomes so severe that it interferes with normal growth, development and activities.
  • “Tet spells,” also known as “hypercyanotic episodes,” are also a concern. During these episodes—which often occur after feeding, warm baths or stress—the baby has a sudden decrease in the amount of oxygen in his blood. He becomes deep blue, breathes faster than normal and may appear to be very irritable or crying. During these episodes, the oxygen level may become so low that the baby’s life is threatened. Babies having a tet spell need urgent medical attention.

How is ToF diagnosed?

A diagnosis of ToF is usually made by echocardiogram (cardiac ultrasound). Other tests may be used to provide additional information.

How is ToF treated?

  • Surgery. Babies with ToF must have open heart surgery for repair. Surgery is usually performed in the first 3 to 6 months of life, although it can be performed earlier, if needed. This surgery consists of closing the VSD (usually using Dacron cloth) and relieving the narrowing between the right ventricle and pulmonary artery. 
  • Catheterization. Some babies may require catheterization to obtain information not available from echocardiography. Occasionally, a baby may benefit from interventional catheterization to widen the connection between the right ventricle and the pulmonary artery. This procedure can serve as a temporary way to increase the oxygen level in the blood.

What are the long-term effects of ToF?

Your child may need additional operation(s) or catheterization(s) as he grows older. Although the goal of the operation is to repair the defect, some patients will develop leakage from the pulmonary valve that requires replacement. This usually occurs in adolescence or later adulthood, although it can occur sooner.

Teenagers with congenital heart defects will have to deal with medical appointments and procedures and possible restrictions on physical activities.

Adults who were treated for congenital heart disease as a child will need to be followed by a cardiologist because complications from early heart disease can arise in adulthood. ToF patients may be at some risk for arrhythmias, leaky valves and other heart problems.
Non-cardiac surgeries may pose risks for some patients and will require evaluation and discussion with a cardiologist. For female patients, pregnancy may also present risks.

Boston Children's helps adults with congenital heart defects, too.

Boston Children’s Heart Center is the largest pediatric heart program in the United States. Our staff of more than 80 pediatric cardiac specialists cares for thousands of children and adults with congenital and acquired heart defects each year, from simple to complex cases. We have experience treating rare heart problems—with results that are among the best in the world.

We are grateful to have been ranked #1 on U.S. News & World Report's list of the best children's hospitals in the nation for the third year in a row, an honor we could not have achieved without the patients and families who inspire us to do our very best for them. Thanks to you, Boston Children's is a place where we can write the greatest children's stories ever told.”
- Sandra L. Fenwick, President and CEO

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