Tetralogy of Fallot

Also known as TOF
What Is

Tetralogy (teh-TRAL-o-je) of Fallot (fah-LO) is a congenital heart defect. This is a problem with the heart's structure that's present at birth. Congenital heart defects change the normal flow of blood through the heart.

Tetralogy of Fallot is a rare, complex heart defect. It occurs in about 5 out of every 10,000 babies. The defect affects boys and girls equally.

To understand tetralogy of Fallot, it helps to know how a healthy heart works. The Health Topics How the Heart Works article describes the structure and function of a healthy heart. The article also has animations that show how your heart pumps blood and how your heart's electrical system works.


Tetralogy of Fallot involves four heart defects:

  • A large ventricular septal defect (VSD)
  • Pulmonary (PULL-mun-ary) stenosis
  • Right ventricular hypertrophy (hi-PER-tro-fe)
  • An overriding aorta

Ventricular Septal Defect

The heart has an inner wall that separates the two chambers on its left side from the two chambers on its right side. This wall is called a septum. The septum prevents blood from mixing between the two sides of the heart.

A VSD is a hole in the septum between the heart's two lower chambers, the ventricles. The hole allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood from the right ventricle.

Pulmonary Stenosis

This defect involves narrowing of the pulmonary valve and the passage from the right ventricle to the pulmonary artery.

Normally, oxygen-poor blood from the right ventricle flows through the pulmonary valve and into the pulmonary artery. From there, the blood travels to the lungs to pick up oxygen.

In pulmonary stenosis, the pulmonary valve cannot fully open. Thus, the heart has to work harder to pump blood through the valve. As a result, not enough blood reaches the lungs.

Right Ventricular Hypertrophy

With this defect, the muscle of the right ventricle is thicker than usual. This occurs because the heart has to work harder than normal to move blood through the narrowed pulmonary valve.

Overriding Aorta

This defect occurs in the aorta, the main artery that carries oxygen-rich blood from the heart to the body. In a healthy heart, the aorta is attached to the left ventricle. This allows only oxygen-rich blood to flow to the body.

In tetralogy of Fallot, the aorta is located between the left and right ventricles, directly over the VSD. As a result, oxygen-poor blood from the right ventricle flows directly into the aorta instead of into the pulmonary artery.


With tetralogy of Fallot, not enough blood is able to reach the lungs to get oxygen, and oxygen-poor blood flows to the body.

Cross-Section of a Normal Heart and a Heart With Tetralogy of Fallot

Cross-Section of a Normal Heart and a Heart With Tetralogy of Fallot
Figure A shows the structure and blood flow inside a normal heart. Figure B shows a heart with the four defects of tetralogy of Fallot.

Babies and children who have tetralogy of Fallot have episodes of cyanosis (si-ah-NO-sis). Cyanosis is a bluish tint to the skin, lips, and fingernails. It occurs because the oxygen level in the blood leaving the heart is below normal.

Tetralogy of Fallot is repaired with open-heart surgery, either soon after birth or later in infancy. The timing of the surgery will depend on how narrow the pulmonary artery is.

Over the past few decades, the diagnosis and treatment of tetralogy of Fallot have greatly improved. Most children who have this heart defect survive to adulthood. However, they'll need lifelong medical care from specialists to help them stay as healthy as possible.

Other Names
  • Fallot's tetralogy

Doctors often don't know what causes tetralogy of Fallot and other congenital heart defects.

Some conditions or factors that occur during pregnancy may raise your risk of having a child who has tetralogy of Fallot. These conditions and factors include:

  • German measles (rubella) and some other viral illnesses
  • Poor nutrition
  • Alcohol use
  • Age (being older than 40)
  • Diabetes

Heredity may play a role in causing tetralogy of Fallot. An adult who has tetralogy of Fallot may be more likely than other people to have a baby with the condition.

Children who have certain genetic disorders, such as Down syndrome and DiGeorge syndrome, often have congenital heart defects, including tetralogy of Fallot.

Researchers continue to search for the causes of tetralogy of Fallot and other congenital heart defects.

Signs, Symptoms, and Complications

Cyanosis is an important sign of tetralogy of Fallot. Cyanosis is a bluish tint to the skin, lips, and fingernails. Low oxygen levels in the blood cause cyanosis.

Babies who have unrepaired tetralogy of Fallot sometimes have "tet spells." These spells happen in response to an activity like crying or having a bowel movement.

A tet spell occurs when the oxygen level in the blood suddenly drops. This causes the baby to become very blue. The baby also may:

  • Have a hard time breathing
  • Become very tired and limp
  • Not respond to a parent's voice or touch
  • Become very fussy
  • Pass out

In years past, when tetralogy of Fallot wasn't treated in infancy, children would get very tired during exercise and could faint. Now, doctors repair tetralogy of Fallot in infancy to prevent these symptoms.

Another common sign of tetralogy of Fallot is a heart murmur. A heart murmur is an extra or unusual sound that doctors might hear while listening to the heart.

The sound occurs because the heart defect causes abnormal blood flow through the heart. However, not all heart murmurs are signs of congenital heart defects. Many healthy children have heart murmurs.

Babies who have tetralogy of Fallot may tire easily while feeding. Thus, they may not gain weight or grow as quickly as children who have healthy hearts. Also, normal growth depends on a normal workload for the heart and normal flow of oxygen-rich blood to all parts of the body.

Children who have tetralogy of Fallot also may have clubbing. Clubbing is the widening or rounding of the skin or bone around the tips of the fingers.


Doctors diagnose tetralogy of Fallot based on a baby's signs and symptoms, a physical exam, and the results from tests and procedures.

Signs and symptoms of the heart defect usually occur during the first weeks of life. Your infant's doctor may notice signs or symptoms during a routine checkup. Some parents also notice cyanosis or poor feeding and bring the baby to the doctor. (Cyanosis is a bluish tint to the skin, lips, and fingernails.)

Specialists Involved

If your child has tetralogy of Fallot, a pediatric cardiologist and pediatric cardiac surgeon may be involved in his or her care.

A pediatric cardiologist is a doctor who specializes in diagnosing and treating heart problems in children. Pediatric cardiac surgeons repair children's heart defects using surgery.

Physical Exam

During a physical exam, the doctor may:

  • Listen to your baby's heart and lungs with a stethoscope.
  • Look for signs of a heart defect, such as a bluish tint to the skin, lips, or fingernails and rapid breathing.
  • Look at your baby's general appearance. Some children who have tetralogy of Fallot also have DiGeorge syndrome. This syndrome causes characteristic facial traits, such as wide-set eyes.

Diagnostic Tests and Procedures

Your child's doctor may recommend several tests to diagnose tetralogy of Fallot. These tests can provide information about the four heart defects that occur in tetralogy of Fallot and how serious they are.


Echocardiography (echo) is a painless test that uses sound waves to create a moving picture of the heart. During the test, the sound waves (called ultrasound) bounce off the structures of the heart. A computer converts the sound waves into pictures on a screen.

Echo allows the doctor to clearly see any problem with the way the heart is formed or the way it's working.

Echo is an important test for diagnosing tetralogy of Fallot because it shows the four heart defects and how the heart is responding to them. This test helps the cardiologist decide when to repair the defects and what type of surgery to use.

Echo also is used to check a child's condition over time, after the defects have been repaired.

EKG (Electrocardiogram)

An EKG is a simple, painless test that records the heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through the heart.

This test can help the doctor find out whether your child's right ventricle is enlarged (ventricular hypertrophy).

Chest X Ray

A chest x ray is a painless test that creates pictures of the structures in the chest, such as the heart and lungs. This test can show whether the heart is enlarged or whether the lungs have extra blood flow or extra fluid, a sign of heart failure.

Pulse Oximetry

For this test, a small sensor is attached to a finger or toe (like an adhesive bandage). The sensor gives an estimate of how much oxygen is in the blood.

Cardiac Catheterization

During cardiac catheterization (KATH-eh-ter-ih-ZA-shun), a thin, flexible tube called a catheter is put into a vein in the arm, groin (upper thigh), or neck. The tube is threaded to the heart.

Special dye is injected through the catheter into a blood vessel or one of the heart's chambers. The dye allows the doctor to see the flow of blood through the heart and blood vessels on an x-ray image.

The doctor also can use cardiac catheterization to measure the pressure and oxygen level inside the heart chambers and blood vessels. This can help the doctor figure out whether blood is mixing between the two sides of the heart.


Tetralogy of Fallot is repaired with open-heart surgery, either soon after birth or later in infancy. The goal of surgery is to repair the four defects of tetralogy of Fallot so the heart can work as normally as possible. Repairing the defects can greatly improve a child's health and quality of life.

The pediatric cardiologist and cardiac surgeon will decide the best time to do the surgery. They will base their decision on your baby's health and weight and the severity of the defects and symptoms.

Some teenagers or adults who had tetralogy of Fallot repaired in childhood need additional surgery to correct heart problems that develop over time. For more information, go to "Living With Tetralogy of Fallot."

Types of Surgery

Complete Intracardiac Repair

Surgery to repair tetralogy of Fallot improves blood flow to the lungs. Surgery also ensures that oxygen-rich and oxygen-poor blood flow to the right places.

The surgeon will:

  • Widen the narrowed pulmonary blood vessels. The pulmonary valve is widened or replaced. Also, the passage from the right ventricle to the pulmonary artery is enlarged. These procedures improve blood flow to the lungs. This allows the blood to get enough oxygen to meet the body's needs.
  • Repair the ventricular septal defect (VSD). A patch is used to cover the hole in the septum. This patch stops oxygen-rich and oxygen-poor blood from mixing between the ventricles.

Fixing these two defects resolves problems caused by the other two defects. When the right ventricle no longer has to work so hard to pump blood to the lungs, it will return to a normal thickness. Fixing the VSD means that only oxygen-rich blood will flow out of the left ventricle into the aorta.

The incision (cut) that the surgeon makes to reach the heart usually heals in about 6 weeks. The surgeon or a hospital staff member will explain when it's okay to give your baby a bath, pick him or her up under the arms, and take your baby for regular shots (immunizations).

Temporary or Palliative Surgery

It was common in the past to do temporary surgery during infancy for tetralogy of Fallot. This surgery improved blood flow to the lungs. A complete repair of the four defects was done later in childhood.

Now, tetralogy of Fallot usually is fully repaired in infancy. However, some babies are too weak or too small to have the full repair. They must have temporary surgery first. This surgery improves oxygen levels in the blood. The surgery also gives the baby time to grow and get strong enough for the full repair.

For temporary surgery, the surgeon places a tube between a large artery branching off the aorta and the pulmonary artery. The tube is called a shunt. One end of the shunt is sewn to the artery branching off the aorta. The other end is sewn to the pulmonary artery.

The shunt creates an additional pathway for blood to travel to the lungs to get oxygen. The surgeon removes the shunt when the baby's heart defects are fixed during the full repair.

After temporary surgery, your baby may need medicines to keep the shunt open while waiting for the full repair. These medicines are stopped after the surgeon removes the shunt.

Living With

The outlook for a child born with tetralogy of Fallot is much better today than in the past. Advances in testing and treatment mean that most children who have this congenital heart defect survive to adulthood. However, they need long-term care from specialists to stay as healthy as possible.

Caring for Your Child at Home

Feeding and Nutrition

Babies who have tetralogy of Fallot can tire while nursing or feeding. Small, frequent meals may be easier for your baby to handle.

Your child also may need extra nutrition. A supplement or an extra feeding can give the baby more calories, vitamins, or iron. Your child's doctors will work with you to decide whether your baby needs extra nutrition.

Tet Spells

"Tet spells" can occur in babies whose tetralogy of Fallot hasn't yet been repaired. Lowering your baby's anxiety or stress can help prevent tet spells and save the baby's energy. For example, slowly picking up your baby and speaking in a soothing voice can avoid startling him or her, which may prevent or reduce crying.

Ask your doctor how you can manage your child's tet spells. Your doctor may suggest that you:

  • Bring the child's knees up tight against his or her chest (this is called the knee–chest position) or have your child squat down. This will increase blood flow to the lungs.
  • Try to calm your child.
  • Call 9–1–1 if the symptoms don't improve right away.

Activity Restrictions

If your child was born with tetralogy of Fallot, he or she may have some physical activity limits. The limits vary with each child. Ask your child's doctor whether:

  • Your child needs to restrict activity or exercise
  • Your child can play in organized sports, especially contact sports
  • You need a note for your child's school or coaches about limiting your child's exercise

Ongoing Medical Care

Children who have tetralogy of Fallot should have ongoing medical care. This includes making sure your child:

  • Sees a pediatric cardiologist for heart checkups as directed
  • Sees a pediatrician or family health care provider for routine exams
  • Takes medicines as prescribed

Children who have severe heart defects, like tetralogy of Fallot, may be at slightly increased risk for infective endocarditis (IE). IE is a serious infection of the inner lining of the heart chambers and valves.

Your child's doctor or dentist may give your child antibiotics before some medical or dental procedures (such as surgery or dental cleanings) that can allow bacteria into the bloodstream. Your child's doctor will tell you whether your child needs to take antibiotics before such procedures.

To reduce the risk of IE, gently brush your young child's teeth every day as soon as they begin to come in. As your child gets older, make sure he or she brushes every day and sees a dentist regularly. Talk with your child's doctor and dentist about how to keep your child's mouth and teeth healthy.

Consider having your child wear a medical ID bracelet or necklace. This alerts anyone caring for your child that the child has a heart defect.

Special Needs for Teenagers and Adults

As children who have heart defects grow up and become teens, they should learn how their hearts differ from normal hearts. They also should know what kind of defects they have, how they were treated, and what type of care is still needed. They should be able to recognize signs and symptoms and know how to respond.

Work with your child's health care providers to compile a packet of medical records and information that covers all aspects of your child's heart defect, including:

  • Diagnosis
  • Procedures or surgeries
  • Prescribed medicines
  • Recommendations about medical followup and how to prevent complications
  • Health insurance

Review your current health insurance plan so you understand your coverage. Keeping your health insurance current is important. If you plan to change jobs, find out whether your new health insurance will cover care for your child's congenital heart defect.

Transition of Care

The move from pediatric care to adult care is an important step in treatment. Talk with your teen's health care team about creating a plan to help your teen transition to adult care. Start planning as soon as your teen is able and willing to fully take part in this process.

Following a transition plan has many benefits. It will help your teen:

  • Get used to talking with health care providers
  • Learn about the adult health care system
  • Understand the importance of having health insurance and learn what his or her insurance covers
  • Take responsibility for his or her medical care

A transition plan also can help your teen think about other important issues, such as future education and employment, birth control and pregnancy planning, and making healthy choices about nutrition, physical activity, and other lifestyle habits.

Additional Surgery and Other Complications

Some teenagers or young adults need additional surgery. For example, the pulmonary valve can narrow again over time, reducing blood flow. A surgeon may need to widen or replace the valve. The cardiologist will discuss with you and your teenager the need for any additional heart surgeries.

Over time, people who have had surgery to repair tetralogy of Fallot also may face other heart problems.

Leaking heart valves. The heart has four valves that open and close with each heartbeat. These valves ensure that blood flows only in one direction.

If a valve doesn't seal tightly, blood can leak back into the chamber it came from. This is called backflow or regurgitation (re-GUR-jih-TA-shun), and it can lead to symptoms and complications.

The most frequent problem that occurs after tetralogy of Fallot repair is pulmonary backflow, or leaking from the pulmonary valve. Backflow from the tricuspid valve and aortic valve also can occur.

Surgery is used to repair or replace the leaking valve. In some cases, catheter-based procedures may be used to replace leaking valves.

Arrhythmias. Arrhythmias (ah-RITH-me-ahs) are another complication that may occur. Arrhythmias are problems with the rate or rhythm of the heartbeat.

Arrhythmias associated with tetralogy of Fallot include ventricular tachycardia, atrial fibrillation, and atrial flutter. For more information, go to the Health Topics Arrhythmia article.

Doctors use medicines to control these arrhythmias. They also may recommend medical procedures or surgery to treat arrhythmias.

Pulmonary artery branch stenosis. Over time, the pulmonary valve can narrow again. This will reduce blood flow to the lungs, making the heart work harder than it should. Several surgical techniques can be used to fix this problem.

Right ventricular aneurysms. The patch used to fix a ventricular septal defect (VSD) can cause areas of the ventricle to weaken. These areas, called aneurysms (AN-u-risms), can bulge or "balloon" out. Aneurysms make it hard for the heart to work as well as it should. Aneurysms are repaired with surgery.

Residual ventricular septal defects. Some VSDs still leak, even after they've been repaired. VSDs are repaired again if they're large or are causing problems with the function of the right ventricle.

Coronary heart disease. As people who have repaired tetralogy of Fallot approach middle age, they can develop coronary heart disease (CHD). (Adults who don't have congenital heart defects also can develop CHD.)

CHD is a condition in which a waxy substance called plaque (plak) builds up in the coronary (heart) arteries. CHD can lead to chest pain, shortness of breath, and heart attack.

For people who have repaired tetralogy of Fallot, preventing CHD is important. The procedures used to treat CHD, such as coronary artery bypass grafting, can cause problems for these people.

Other Considerations

Many women with repaired tetralogy of Fallot who become pregnant are able to have successful, full-term pregnancies. Others may have difficult pregnancies.

Women with tetralogy of Fallot who want to become pregnant (or who are pregnant) should talk with their doctors about:

  • Health risks during pregnancy
  • Medicines they can take during pregnancy
  • Any new or worsening symptoms

If possible, these women should consult specialists who take care of pregnant women who have heart conditions, such as congenital heart defects.

Adults who were born with tetralogy of Fallot should consider job changes carefully, because health benefits may change. Some health plans have waiting periods or clauses to exclude some types of coverage. Before making any job changes, find out whether the change will affect your health insurance.

Several laws protect the employment rights of people who have health conditions, such as congenital heart defects. The Americans with Disabilities Act and the Work Incentives Improvement Act try to ensure fairness in hiring for all people, including those who have health conditions.

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