What is Tetralogy of Fallot (TOF)?
TOF is a congenital heart defect that affects the heart’s structure and causes oxygen-poor blood to flow out of the heart and around the body. While it’s a rare and complex heart defect, occurring in about 5 of every 10,000 babies, our team at Texas Children’s Heart Center performs an average of 30 TOF repairs each year and our survival rate is 99 percent.
How does TOF affect the heart?
In TOF, a part of the muscle that separates the lower chambers of the heart gets deviated into the right side and fails to join the rest of the muscular septum. This problem translates into four different heart defects:
- Ventricular septal defect (VSD): A hole in the wall between the two lower chambers of the heart
- Pulmonic stenosis (PS): Narrowing of the exit from the heart to the lungs (at, above or below the pulmonary valve)
- Malpositioned or overriding aorta: The aorta is directly over the VSD, instead of over the left ventricle
- Ventricular hypertrophy: An overly muscular right ventricle
In a typical heart, oxygen-poor blood flows to the right side of the heart where it is pumped to the lungs to receive more oxygen. In TOF, the PS heart defect makes it harder for the blood to flow out of the right side of the heart. This causes oxygen-poor blood to travel across the heart through the VSD, into the left ventricle, and out into the aorta (that distributes the blood to the rest of the body).
When the aorta carries mixed (oxygen-poor and oxygen-rich) blood to the rest of the body, less oxygen is available to the tissues, causing cyanosis – the appearance of a blue or purple coloration of the skin or mucous membranes, sometimes called “blue baby syndrome.”
In very severe cases (pulmonary atresia), the outflow of the right heart is completely obstructed and there is no connection between the right heart and the lungs. The lungs have to then get blood supply from other sources, such as the ductus arteriosus, a communication between the aorta and the pulmonary artery that we all have when we’re born and normally closes in the first few days of life.
What are symptoms of TOF?
TOF symptoms can vary depending on the seriousness of the condition. If the condition is mild, patients may just have a heart murmur or rapid breathing. If the condition is more severe, patients may have a blue discoloration of the body, shortness of breath, tire easily or even loss of consciousness.
How is TOF diagnosed?
Several tests may be recommend to diagnose TOF. These tests can provide information about the four heart defects that can occur and how serious they are. The most common tests include:
- Chest X-ray
- Electrocardiogram (EKG)
How is TOF treated?
Open-heart surgery, either soon after birth or later in infancy, is the most successful treatment. At Texas Children’s Heart Center, a surgical approach to the repair of TOF is individualized for each patient based on the child’s age, anatomy and symptoms. This allows us to repair the defect and preserve critical parts of the cardiac anatomy, thereby optimizing the child’s long-term heart function.
Even though most of the time we perform the repair at once, in some situations, we may undertake the repair in two stages:
First stage: Blalock-Taussig shunt. An artificial shunt (or tube) is placed between the aorta and pulmonary artery to increase blood flow to the lungs.
First or second stage: Complete TOF repair. The opening between the two chambers of the heart (VSD) is patched to prevent blood from traveling between both sides, and the exit of the right ventricle is widened to increase blood flow to the lungs.
Click here to see Texas Children’s TOF surgical outcomes.