What causes tetralogy of Fallot?
Some congenital heart defects may have a genetic link, either occurring due to a defect in a gene, a chromosome abnormality, or environmental exposure, causing heart problems to occur more often in certain families.
Maternal abuse of alcohol during pregnancy, leading to fetal alcohol syndrome, is linked to tetralogy of Fallot. Mothers who take medications to control seizures and mothers with phenylketonuria are also more likely to have a baby with tetralogy of Fallot.
Tetralogy of Fallot may also occur as part of a syndrome like Down syndrome or DiGeorge syndrome.
Most of the time, this heart defect occurs sporadically (by chance), with no clear reason evident for its development.
Why is tetralogy of Fallot a concern?
The amount of oxygen-poor (blue) blood that passes through the VSD to the left side of the heart varies. If the right ventricle obstruction is severe, or if the pressure in the lungs is high, a large amount of oxygen-poor (blue) blood passes through the VSD, mixes with the oxygen-rich (red) blood in the left ventricle, and is pumped to the body. The more blood that goes through the VSD, the less blood that goes through the pulmonary artery to the lungs, and the less oxygen-rich (red) blood that returns to the right side of the heart. Soon, nearly all the blood in the left ventricle is oxygen-poor (blue). This is an emergency situation, as the body will not have enough oxygen to meet its needs.
Some situations, such as crying, increase the pressure in the lungs temporarily, and increasing blueness might be noted as a baby with tetralogy of Fallot cries. In other situations, the pathway from the right ventricle to the pulmonary artery becomes tighter, preventing much blood from passing that way, and allowing oxygen-poor (blue) blood to flow through the VSD into the left heart circulation. Both of these situations are nicknamed "TET spells." Sometimes, steps can be taken to lessen the pressure or the obstruction, and allow more blood to flow into the lungs and less through the VSD. These steps, however, are not always effective.
What are the symptoms of tetralogy of Fallot?
The following are the most common symptoms of tetralogy of Fallot. However, each child may experience symptoms differently. Symptoms may include:
- Because large amounts of oxygen-poor (blue) blood can flow to the body under certain circumstances, one of the symptoms of tetralogy of Fallot is blueness (blue color of the skin, lips, and nail beds) that occurs with such activity as crying or feeding, and quickly becomes more obvious.
- Some babies do not have noticeable cyanosis (blue color of the skin, lips, and nail beds), but may instead be very irritable or lethargic due to a decreasing amount of oxygen available in the bloodstream.
- Some children become pale or ashen in color, and may have cool, clammy skin.
Any of these can be symptoms of tetralogy of Fallot. The symptoms of tetralogy of Fallot may resemble other medical conditions or heart problems. Always consult your child's doctor for a diagnosis.