Tetralogy of Fallot

Tetralogy of Fallot (TOF), formerly known as Steno-Fallot tetralogy, is a congenital heart defect characterized by four specific cardiac defects. Classically, the four defects are:

pulmonary stenosis, which is narrowing of the exit from the right ventricle;

a ventricular septal defect, which is a hole allowing blood to flow between the two ventricles;

right ventricular hypertrophy, which is thickening of the right ventricular muscle; and

an overriding aorta, which is where the aorta expands to allow blood from both ventricles to enter.

At birth, children may be asymptomatic or present with many severe symptoms. Later in infancy, episodes of bluish colour to the skin typically occur due to a lack of sufficient oxygenation, known as cyanosis. When affected babies cry or have a bowel movement, they may undergo a "tet spell", where they turn cyanotic, have difficulty breathing, become limp, and occasionally lose consciousness. Other symptoms may include a heart murmur, finger clubbing, and easy tiring upon breastfeeding.

The cause of tetralogy of Fallot is typically not known. Maternal risk factors include lifestyle-related habits (alcohol use during pregnancy, smoking, or recreational drugs), medical conditions (diabetes), infections during pregnancy (rubella), and advanced age of mother during pregnancy (35 years and older). Babies with Down syndrome and other chromosomal defects that cause congenital heart defects may also be at risk of tetralogy of Fallot.

Tetralogy of Fallot is typically treated by open-heart surgery in the first year of life.