Tetralogy of Fallot (TOF)

This congenital heart condition is a combination of defects that results in impaired pulmonary blood flow and reduced oxygen levels in the blood.

Normal Heart

In a normal heart, oxygen-depleted blood returns to the right atrium and empties into the right ventricle, which then pumps the blood to the lungs to receive oxygen. Oxygen-rich blood from the lungs returns to the heart’s left atrium and is pumped out to the body via the left ventricle.

Heart with Tetralogy of Fallot

In a heart with Tetralogy of Fallot, there are four defects. First, there is a large hole between the
ventricles called a ventricular septal defect, or VSD. Second, there is muscular narrowing below the
pulmonary valve that can restrict pulmonary blood flow and may result in underdevelopment of the
pulmonary valve. Third, the aorta is positioned over the ventricular septal defect. And finally, the right ventricle becomes thickened, known as ventricular hypertrophy, because it is working against the obstruction in the outflow into the pulmonary artery.


The symptoms of Tetralogy of Fallot vary from patient to patient. Infants with a greater narrowing
of the area leading to the pulmonary artery will have a reduced amount of blood going to the lungs. The decrease in blood flow to the lungs can lead to lower oxygen levels in the blood and cyanosis, a
bluish appearance of the skin. Infants may experience periods of extreme cyanosis, also called
tetralogy spells or hypercyanotic spells, which can be life threatening.


To get blood flowing to the lungs in patients with severe obstruction of flow from the right ventricle to the pulmonary artery, a medication may be used to keep open a vessel between the aorta and the pulmonary artery that normally closes after birth. In select cases, a temporary tube, or shunt, may be surgically added to connect the aorta and the pulmonary artery. A complete surgical repair is usually performed in the first six months of life.