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What is Tetralogy of Fallot?

Tetralogy of Fallot is a complex congenital heart defect (e.g., present at birth) characterized by the presence of four heart problems. Babies born with this heart defect have:

A large hole in the muscular wall that separates the heart’s lower pumping chambers (called a ventricular septal defect).

An obstruction, or narrowing, in the pulmonary valve, which makes it harder for blood to travel from the heart to the lungs to receive fresh oxygen.

A misplaced aorta, so instead of being connected to the left ventricle, the aorta \”overrides\” the left and right ventricles and is frequently located in the same place as the ventricular septal defect, allowing oxygenated and unoxygenated blood to mix.

A thickened muscle surrounding the lower right ventricle, or chamber that pumps unoxygenated blood to the heart.

Tetralogy of Fallot occurs in an estimated five of every 10,000 babies. The cause is usually unknown, but the defect seems more common in children with Down syndrome or DiGeorge syndrome.

This defect changes normal blood flow through the heart. In a healthy heart, the organ’s left side pumps oxygenated blood to the body, while the heart\’s right side pumps unoxygenated blood to the lungs to receive fresh oxygen. In children with Tetralogy of Fallot, blood can make its way from the right to left ventricle (mixing oxygen-rich and oxygen-poor blood). This partly oxygenated blood then goes to the aorta and is transported out to the rest of the body.

As a result, children with the defect are often blue, or cyanotic, because their tissues are not receiving enough oxygenated blood.

Because Tetralogy of Fallot involves major abnormalities in the heart\’s structure, it can often be diagnosed while the baby is still in utero by a fetal ultrasound. This early diagnosis gives the doctors time to develop a treatment plan. Tetralogy of Fallot is always treated with surgery, but the number and type of surgeries depend on the severity of the defect and the baby\’s overall health. The goal is to completely repair the heart as early in the child’s life as possible.

In some cases, a complete surgical repair (open-heart surgery) can be done almost immediately. But if a child has other health issues, physicians might first perform a shunt operation. This temporary solution involves sewing a small tube between the aorta and pulmonary artery, to encourage enough blood flow to the lungs. This shunt will be closed later on, when the full repair is completed.

The full repair involves a complex series of operations that:

Repair the ventricular septal defect, usually with a patch covering the hole between the ventricles.

Remove some of the excess muscle from the right ventricle, allowing it to operate more normally.

Repair or remove the pulmonary valve (a heart can still function normally with no pulmonary valve).

Possibly enlarge the narrowed pulmonary arteries connecting the heart to the lungs.

Some children will need to limit physical activity even after healing due to leftover obstructions, leaky valves or decreased heart function. These children often need to be followed throughout their lives for heart-related complications.


  • American Heart Association
  • Tetralogy of Fallot.
    National Heart, Lung, and Blood Institute
  • What is Tetralogy of Fallot?

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