TETRALOGY OF FALLOT
Dr Ira Shah
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.
What are the causes of cyanotic spells?
There is a “spasm” of the band of muscles just at the right ventricle narrowing. This leads to further decrease in blood flowing into the lungs and thus increased blue color as oxygen content of blood becomes very low. To compensate this, the patients breathe rapidly and try and take in as much oxygen into the lungs as possible.
There are several provoking factors that can precipitate cyanotic spell such as exercise, fever, diarrhea, dehydration etc. To compensate for these spells, children tend to squat to decrease blood supply to the right ventricle and thus decreasing right to left shunting of blood. Sometimes these spells may be life threatening.
What is the treatment of Tetralogy of Fallot?
Some infants with severe Tetralogy of Fallot may need an operation to increase blood supply to the lungs. This is done by shunt surgery whereby the connection between aorta and pulmonary artery is made. This increases the oxygen content of the blood. In older children, corrective surgery is required which involves closing the ventricular septal defect, removing the muscle causing narrowing in the right ventricular outflow.
What happens if a patient with Tetralogy of Fallot does not undergo surgery?
If a patient with Tetralogy of Fallot does not undergo surgery, there is increased risk of stroke, brain abscess, heart failure. Sometimes a cyanotic spell may be fatal. Over a period of time, due to constant decreased oxygen supply to the heart and other organs of the body, the heart becomes weak.
What is the prognosis post surgery?
After surgery, long term outlook varies depending on how severe the defects were before surgery. Lifelong follow up with cardiologist is needed.
created on 1-08-2010
updated on 1-08-2010