Dr Ira Shah
Consultant Pediatrician
Editor - Pediatric Oncall

What is Tetralogy of Fallot (TOF)?
The heart consists of 4 chambers, right atrium that receives oxygen poor blood from the body, right ventricle that receives blood from right atrium and pumps it through the pulmonary artery to the lungs to get oxygen; left atrium that receives oxygen rich blood from the lungs and left ventricle that receives blood from left atrium and then pumps it through the aorta to the rest of the body. In Tetralogy of Fallot, there is a large hole between the two ventricles (ventricular septal defect) that lets blood pass from the right to the left ventricle without going through the lungs along with a narrowing near the outflow of right ventricle thus restricting blood flow into the pulmonary artery. In addition, since right ventricle has to pump blood against a narrowing, it is more muscular. Also the aorta opens directly over the ventricular septal defect.

What happens in Tetralogy of Fallot?
Since there is mixing of both oxygen poor blood and oxygen rich blood in left ventricle which goes into the body, there is bluish color of the baby (due to less oxygen in blood). These babies have sudden episodes of increased bluish colour of body along with rapid breathing and may even become unconsciousness. These episodes are known as cyanotic spells. Cyanotic spells are more open after 6 months of age and can occur at increased frequency.