Tetralogy of Fallot
What Is Tetralogy of Fallot?
Tetralogy of Fallot (teh-TRAL-uh-jee of fuh-LOW) — or TOF — is a combination of congenital heart defects. It has four components:
- A ventricular septal defect (VSD)
- Pulmonary stenosis : This may be narrowing of the valve itself, or narrowing above or below the valve. Often, it is below the valve (known as infundibular narrowing or sub-PS) and at the valve level
- Thickening of the right ventricle called right ventricular hypertrophy (RVH)
- 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:
- A large hole, or ventricular septal defect (VSD)
- A narrowing (stenosis) (sten-O'-sis) at or just beneath the pulmonary valve
This narrowing partially blocks/obstructs 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.
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 blood to the lungs 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 cyanosis (blueness) unless the obstruction gets worse with time, which it often does. Some patients with tetralogy of Fallot have normal saturations and are referred to as having “pink” tetralogy.
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 a decrease in blood flow to the lungs and increased blue blood flow from the right to the left ventricle, then to the body. They can be dangerous and, if they occur, the pediatric cardiologist needs to be notified and patients require urgent/emergent evaluation.
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 of the heart and vessels, specifically the size of the pulmonary arteries, the amount of narrowing or obstruction below the pulmonary valve, the pulmonary valve size and several other factors.
Tetralogy of Fallot (Pulmonary Stenosis)
Tetralogy of Fallot (Pulmonary Atresia)
Tetralogy of Fallot (Pulmonary Atresia with MAPCAS)
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 significant obstruction of blood flow to the lungs or with pulmonary atresia). The diagnosis is confirmed with an echocardiogram. Often, the diagnosis is suspected prenatally due to an abnormal fetal ultrasound.
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-Thomas-Taussig shunt or BTT shunt. With this surgery, some blood from the aorta flows into the lungs through the shunt 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 to perform the complete 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. It is important to remember that many factors go into the decision on the timing and type of surgery since all patients are different. This is the role of pediatric cardiologist in discussion with the cardiovascular surgeon.
The risks of open-heart surgery always include bleeding, infection and the need for cardiopulmonary bypass (the baseline risks of the heart/lung bypass machine used at the time of surgery). Special risks include injury to the electrical system of the heart, the possibility of a residual hole in the heart, as well as 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, the presence of persistent abnormalities and the presence of any other medical issues. Specifically, there may be a residual hole or VSD, narrowing of the pulmonary valve or arteries, leakiness of the pulmonary valve, abnormal heart function or the development of rhythm abnormalities. Patients with repaired congenital heart disease may be at higher risk for endocarditis (the development of an infection inside the heart) and some require antibiotics prior to dental work in addition to consistent dental care.
Children requiring cardiac surgery in the first year of life are at higher risk for developmental delays and require close follow up of their developmental progress. Many patients with repaired tetralogy of Fallot will require additional cardiac interventions in the future, including the placement of new pulmonary valve. Therefore, lifelong medical follow up is needed. Adults with this diagnosis can be seen in a specialized adult congenital heart center.
Heart Center Family Resource Guide
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