Tetralogy of Fallot

Tetralogy of Fallot (TOF) consists of two major lesions and two minor lesions:

• Large ventricular septal defect (VSD): This is a hole in the wall separating the two lower heart chambers which are the pumping chambers.
• Pulmonary stenosis: This is a narrowing at and below the pulmonary valve, obstructing blood flow to the lungs. The pulmonary arteries may be small as well.
• Right ventricular hypertrophy.
• Overriding aorta.

These defects cause the child to become cyanotic (bluish color to the lips, nailbeds, and skin). This is caused by "blue blood," low in oxygen, from the right ventricle passing through the VSD directly into the aorta and then to the body. Reduced amounts of blood go to the lungs because of the obstruction from the pulmonary stenosis and smaller size of the pulmonary artery. The stress of pumping blood through these narrowed areas causes the right ventricle to enlarge (hypertrophy). Some infants and children experience episodes called "tet spells" caused by a sudden decrease in the amount of blood going to the lungs. During these spells the child turns very blue, may breathe rapidly, and may pass out.

Children with these defects may grow poorly, tire easily, and have frequent respiratory infections. The age of surgical repair will depend on the severity of the defects and the child's symptoms. Surgery usually consists of total correction. Sometimes, it may be performed in stages, allowing the child to grow. Children with surgically treated or untreated TOF require penicillin (also called SBE prophylaxis) prior to any dental work or surgery on the mouth, bowel, or bladder. This helps prevent the uncommon, but possible, occurrence of bacterial infection affecting the heart near the defects or the heart valves.