Resource Center
What is Tetralogy of Fallot (TOF)?
Topics listed below include:
- Overview
- How common is TOF?
- How does TOF develop?
- What causes TOF to develop?
- How is TOF diagnosed?
- If I have TOF, can I have children?
- If I have TOF, do my children have a higher risk of having a heart defect?
- What are the long-term outcomes for adults with unrepaired TOF?
- What health problems can occur with TOF?
- Are there restrictions on how much I can exercise?
- What surgical treatments exist for TOF?
- What are the long-term outcomes for adults with repaired TOF?
- What kind of cardiology care is recommended for adults with repaired and unrepaired VSD?
- What other challenges face adults living with TOF?
- A ventricular septal defect (hole in the wall separating the two lower chambers of the heart)
- Pulmonary stenosis (narrowing of the opening to the pulmonary valve)
- Right ventricular hypertrophy (thickening of the outer wall of the right ventricle), and
- Overriding aorta (the aortic valve is located unusually close to the right ventricle, also close to the ventricular septal defect).
How common is TOF?
TOF is the most common cyanotic heart birth defect. About 1 in 1500 babies is born with TOF. About 10% of all heart defects are TOF.
How does TOF develop?
In the womb the heart starts as a tube. It then folds back on itself and develops chambers. When the chromosomes and genes responsible for this development are defective or malfunction, heart defects form.
What causes TOF to develop?
Doctors do not know the cause of most cases of TOF.
Heredity may play a role. Parents with a congenital heart defect may be more likely to have a child with TOF than other parents. Persons with other birth defects, such as DiGeorge’s syndrome or Down syndrome are more likely to have Tetralogy of Fallot.
Other factors that increase the risk of a mother having a child with Tetralogy of Fallot are:
- Using alcohol or street drugs during pregnancy;
- Poor nutrition during pregnancy;
- Taking medications to control seizures during pregnancy;
- Having phenylketonuria (fen-el-key-toe-NEW-ree-a, or PKU);
- Having viral infections such as rubella (German measles) during pregnancy;
- Mother over 40 years old.
How is TOF diagnosed?
Most cases of TOF are found shortly after birth. By listening to the heart with a stethoscope, a doctor can usually hear the rumble or swish of blood as it goes through the hole. This is called a murmur. Sometimes you can even feel the rumble of the blood going through the hole, just by putting a hand on the chest; this is called a thrill.
Tests to verify the presence and impact of TOF include:
- Chest x-ray to look at the heart and lungs for enlargement or fluid
- Electrocardiogram, which is a paper tracing of the heart’s electrical system
- Echocardiogram, which is an ultrasound picture of the heart to look at its structure
- Cardiac MRI may also be used.
Infants with may have "tet spells", which are episodes of severe cyanosis (blue lips, face, and/or fingers and toes) that occur with crying or increasing physical activity. These spells can be severe, with loss of consciousness or seizure. Prolonged or very frequent spells can cause brain damage.
If I have TOF, can I have children?
A recent study has shown that a majority of women with TOF tolerate pregnancy well. However, complications such as congestive heart failure and heart rhythm problems can occur. Pre-pregnancy planning and close observation during pregnancy by an ACHD specialist is recommended.
If I have TOF, do my children have a higher risk of having a heart defect?
Yes.
What are the long-term outcomes for adults with unrepaired TOF?
Only 10% of infants with unrepaired TOF are likely to survive past age 21.
Most adults with unrepaired TOF had a shunt performed in childhood. Many have developed additional heart, lung, and blood problems in response to the long term effects of the unrepaired VSD. When this occurs, it is called Eisenmenger's Syndrome. Once permanent lung and heart damage has occurred, surgical repair may not be an option.
What health problems can occur with TOF?
- Problems with heart rhythm
Some patients with repaired TOF develop problems with unusually rapid or slow heart rhythm. Rapid heart rate can be caused by the surgical procedures during the repair. Life threatening heart rhythms can cause sudden death years after repair. Evaluation at an adult congenital heart disease center can determine if you are at risk for this. Enlargement of the heart due to leaky pulmonary valves can also cause rhythm problems
- Why having a leaky pulmonary valve is a problem
When a valve leaks, the heart has to work harder to keep the blood moving in the right direction. The larger the leak, the more blood the heart has to pump. In many people, their heart can compensate for the extra workload. But for some people, the heart's extra work creates new problems. The heart can start to stretch and lose strength. This stretching can also cause serious heart rhythm problems. There is wide variation in how individual TOF hearts respond to leaky pulmonary valves. Leakage can also increase over time. This often makes it hard for doctors to predict how your valve leakage will affect you. This is one reason why it is important that all people with TOF continue to receive regular cardiac follow-up. If your leak is large, you are experiencing symptoms, and/or your heart is having additional problems, your cardiologist may recommend another surgery to replace this valve. Replacing a leaky pulmonary valve can help you feel better and/or prevent further heart damage.
Deciding when to replace a pulmonary valve in TOF can be one of the most difficult decisions that ACHD doctors and patients face. On one hand, studies suggest that if this valve is replaced early enough, people often feel better. The heart can get smaller and rhythm problems may be reduced. If the valve is replaced late, there may be little or no improvement in symptoms and/or heart function. On the other hand, it does not make sense to replace these valves too soon. Valves used in this position are usually made of tissue, and these valves don't last forever. Once you have a new valve, it will likely need to be replaced again at some point in the future. Waiting allows you to benefit from new technologies under development, such as valve replacement using catheters or longer lasting tissue valves. ACHD clinics weigh many different factors when deciding if and when to replace this valve, such as exercise tolerance, MRI, echo and EKG results, and changes in these results over time. MRI and echocardiograms can measure the amount of regurgitation directly, while the QRS durations measured by EKG greater than 185 msec are correlated with occurrences of ventricular tachycardia.
It is important that your needs and plans are also considered when deciding when to have your pulmonary valve replaced. For example, pregnancy can make leaky valves worse. If you are planning a pregnancy, your doctor may recommend you have your valve replaced first. If possible, you might also want to plan surgery for certain times in your life. If you plan to join the Peace Corps, you might want to get your valve replaced before you go! The question of when to replace pulmonary valves in TOF is a hotly debated topic in ACHD care today. There is general agreement that these valves should be replaced neither "too early" nor "too late". But different ACHD specialists can use different markers to decide when the "time is right". Ask your cardiologist what information he or she is using to make this decision. If you have questions about the timing of your replacement, you may want to seek a second opinion from another ACHD clinic to help guide your decision.
Are there restrictions on how much I can exercise?
Many adults with repaired TOF can exercise normally. If you have additional problems, such as shunting, rhythm problems, and/or valve problems, you should consult with your cardiologists about what kind of exercise is most appropriate for you.
We recommend that all those with heart conditions check with their cardiologist before taking on any new athletic activities.
What surgical treatments exist for TOF?
The first surgical treatment was the Blalock-Taussig shunt first performed in 1944. This palliative surgery relieved the cyanosis and allowed the children to grow to adulthood. In this procedure, one branch of the subclavian artery is cut and connected to the pulmonary artery, allowing the lungs to get more blood with low oxygenation from the body. Other shunt techniques have been developed over the years, including the Potts, Waterston, Waterston-Cooley, and Davidson shunts. Some of them are more difficult that others to take down when performing the repair operation.
In 1954, the first surgical repairs were performed. The VSD is closed with a patch, removing some of the thickened muscle below the pulmonary valve, and repairing or replacing the pulmonary valve. Repair procedures are usually done between ages 6-12 months, and may require additional shunts as the patient grows.
The repair surgery has less than 2% risk of death and a 90% or greater 30 year survival. As the first TOF repair patients are only in their 60s now, we do not know the full expected lifespan.
What are the long-term outcomes for adults with repaired TOF?
The oldest survivors of TOF repair are now in their fifties and sixties. This means that we do not yet know what the life-long impact of TOF repair will be. We do know that about 10% of those with repaired TOF will need to have their pulmonary valve replaced due to regurgitation, or leakage
What kind of cardiology care is recommended for adults with repaired and unrepaired VSD?
TOF is considered to be a moderate complex CHD, and the American College of Cardiology has recommended that TOF patients be seen regularly at regional ACHD centers. The size of the right ventricle and pulmonary regurgitation will be monitored for changes over time. This will be done with electrocardiograms, echocardiograms, and sometimes cardiac catheterization, CAT scans, or cardiac MRI. If it is determined that your pulmonary valve should be replaced, it is recommended that the procedure be done at a regional ACHD center by a surgeon with experience in ACHD. In any case, a regular general cardiac exam is suggested. You should also continue to protect yourself from heart infection (endocarditis).
If you have an unrepaired TOF or repaired TOF with pulmonary hypertension, you should receive regular care at a specialized ACHD clinic. It is important that you see doctors who know about your special needs and can help keep you feeling your best. New treatments for your symptoms may also be available. As with all adults, your risk of acquired heart disease rises with age and other risk factors such as smoking, high blood pressure, poor diet, etc. This acquired (and mostly preventable) heart disease worsens the complications of congenital heart disease, increasing your chances of heart attack, heart failure, sudden death, and stroke.
What other challenges face adults living with TOF?
Like all those with congenital heart defects, adults with TOF can face psychosocial issues related to their CHD. For example, teens and young adults may have self-esteem issues related to their scar. Depression and risk taking behavior are more common in adults with CHD.
Adults with TOF can also face discrimination when applying for life and health insurance. If you are rejected or asked to pay higher premiums, we suggest that you ask your cardiologists to send additional documentation about your health condition to your insurance company, including data on long-term outcomes in your disease.