Tetralogy of Fallot

Tetralogy of Fallot (teh-TRAL-uh-jee of fuh-LOW) — or TOF — has four components:

  1. A ventricular septal defect (VSD)
  2. Pulmonary stenosis (this may be the valve itself, or narrowing above or below the valve. It is usually below the valve (known as infundibular narrowing or sub-PS))
  3. Thickening of the right ventricle called right ventricular hypertrophy (RVH)
  4. Overriding or straddling of the aorta over the wall (septum) between the right and left ventricles

To understand TOF, frequently called “tet,” you must understand two main abnormalities:

  1. A large hole, or ventricular septal defect
  2. A narrowing (stenosis) (sten-O'-sis) at or just beneath the pulmonary valve

This narrowing partially blocks the blood flow from the heart's right side to the lungs. If there were no hole between the ventricles, the right ventricle would have to increase the pressure to overcome this narrowing or obstruction. However, since there is a VSD, blood can flow from the right ventricle to the left ventricle without going through the lungs. Therefore, blue blood (blood with less oxygen) goes to the body and the patient may appear more blue or “cyanotic.” The more obstruction there is, the less blood can get to the lungs to become oxygenated and the bluer (more cyanotic) the patient becomes. 

Typical Heart

Heart with Tetralogy of Fallot

In some patients, there is complete obstruction to blood flow to the lungs (known as pulmonary atresia) in which case all the blue blood goes from the right to the left ventricle. The only way to get oxygen blood to the body is if the ductus arteriosus remains open by giving a medication called prostaglandin. In less severe forms of tetralogy of Fallot, there is only mild obstruction to blood flow to the lungs. These patients may not have severe cyanosis (blueness) unless the obstruction gets worse with time, which it usually does.

Typical Heart - Cross Section 

Heart with TOF with Pulmonary Atresia 

Some babies with tetralogy of Fallot have “spells” where they suddenly become very blue (cyanotic) and breathe rapidly. They may become irritable or even become unconscious. These “spells” are caused by increased blood flow from the right to the left ventricle. They can be dangerous and, if they occur, the pediatric cardiologist needs to be notified immediately. Usually, in the United States, surgery is performed early in life so that these “spells” do not occur. The type of surgery depends in part on the anatomy — the size of the pulmonary arteries, the amount of narrowing or obstruction below the pulmonary valve and other factors.

What Are the Symptoms of Tetralogy of Fallot?

Symptoms of blue color or a “spell” may occur.

How Is Tetralogy of Fallot Diagnosed?

Diagnosis is usually made early in life (infancy) due to the finding of an abnormal murmur or cyanosis (in the case of pulmonary atresia). The diagnosis is confirmed with an echocardiogram.

How Is Tetralogy of Fallot Treated?

The surgical goal is to relieve all areas of obstruction and close the VSD. Sometimes this can all be done at once (single stage repair). Other times, infants may need an operation to give temporary relief by increasing blood flow to the lungs with a shunt. This is done by making a connection between the aorta and the pulmonary artery, called a Blalock-Taussig shunt or BT shunt. Then some blood from the aorta flows into the lungs to get more oxygen. This reduces the cyanosis and allows the child to grow and develop until the problem can be fixed when the child is older. However, it is increasingly common (almost universal) to perform the open heart surgery at a young age (neonatal repair) to establish normal blood flow early and allow the normal growth and development of the heart, lungs and blood vessels.

Treatment Risks

The risks of open-heart surgery always include bleeding, infection and the need for cardiopulmonary bypass. Special risks include injury to the electrical system of the heart, the possibility of a residual hole in the heart and the possibility of residual leakiness or obstruction of the repaired valve.

What Are the Long-term Effects of Tetralogy of Fallot?

If surgery is not performed, the patient will become bluer with time and have difficulty with exercise. More “spells” can occur, and there is a risk of complications from rhythm abnormalities, strokes, severe cyanosis and poor right-heart function. Early surgery is felt to decrease these complications. After surgery, the long-term outlook varies, depending largely on how severe the defects were before surgery. Specifically, there may be a residual hole or VSD, narrowing of the pulmonary valve or arteries, leakiness of the pulmonary valve, abnormal heart function and rhythm abnormalities. Therefore, lifelong medical follow up is needed.

Adults with this diagnosis can be seen in a specialized adult congenital heart center. There is always the risk of bacterial endocarditis so that preventive measures are needed for life.


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