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Overview of Tetralogy of Fallot

By Maureen Salamon

Updated October 07, 2008

(LifeWire) - Tetralogy of Fallot may sound like an obscure disease, and it is rare, but it's actually one of the most common congenital cyanotic heart defects, and the outlook for an affected newborn treated today is much better than it used to be.

Once known as blue baby syndrome, tetralogy of Fallot (TOF) is called a "cyanotic heart defect," because it can cause the lips, skin or tongue to turn blue from lack of oxygen. ("Cyanosis" is a blue discoloration of the skin.) As a congenital disease, TOF is a condition children are born with, and it is named both for the four distinct heart defects it produces ("tetra") and for one of the key physicians who helped identify the anomaly in the 1800s, Etienne-Louis Arthur Fallot.

About 5 of every 10,000 babies are born with the condition, which occurs in boys and girls equally. The condition used to kill most affected infants, but an effective surgical procedure called "intracardiac repair" was developed to treat TOF. Now, 95% of babies with TOF undergo successful surgery before they turn 2.

The four heart defects present in TOF include:

  • A sizable ventricular septic defect (VSD), which is a hole in the wall that separates the lower chambers of the heart, the ventricles. This hole keeps oxygen-rich blood from flowing in to the aorta as it should.
  • Pulmonary valve stenosis, a narrowing of the pulmonary valve that restricts the passage of blood from the right ventricle to the pulmonary arteries. This problem makes the heart work harder than normal and keeps sufficient blood from reaching the lungs.
  • Right ventricular hypertrophy, a thickening of the right ventricle caused by the heart working harder than normal.
  • An overriding aorta, leaving the aorta located between the left and right ventricles over the VSD instead of its normal location, attached to the left ventricle.

(You can read an overview of the heart's chambers and valves here.)

Babies born with TOF may seem perfectly healthy at first, but the condition usually becomes quickly apparent since it limits oxygen-rich blood from flowing correctly through the body. Such babies may exhibit cyanosis or a significant heart murmur when examined with a stethoscope. An echocardiogram can definitively diagnose the problem.

Depending on the severity of the TOF, infants will either undergo complete surgical repair of the condition or receive a temporary repair, which will be completed when the baby is larger. Doctors base the surgical timing on how adequate the child's oxygen levels are.

Some children, after surgery, have no enduring heart problems. Others suffer from heart rhythm problems, which can be treated with either medication or with a surgically implanted pacemaker. Many children have residual pulmonary valve leakage, which can later be remedied with a valve replacement.

Long-term studies of TOF patients show that, although many can engage in normal activities, including sports, their heart defect may continue to affect their lives. For example, female patients with TOF are more likely to experience cardiac problems during pregnancy, and infant mortality for their children is higher than normal.

Many of the risk factors for TOF happen during the mother's pregnancy. Pregnant women need to know that viral infections (such as German measles), being older than 40, alcohol use and poor nutrition during pregnancy increase a baby's risk of developing TOF.


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LifeWire, a part of The New York Times Company, provides original and syndicated online lifestyle content. Maureen Salamon is a New Jersey-based freelance writer who has written for newspapers, websites and hospitals.

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