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Tetralogy of Fallot

Tetralogy of Fallot (teh-tral-uh-je ov fuh-LOE) is a rare condition caused by a combination of four heart defects that are present at birth. These defects, which affect the structure of the heart, cause oxygen-poor blood to flow out of the heart and into the rest of the body. Infants and children with tetralogy of Fallot usually have blue-tinged skin because their blood doesn't carry enough oxygen.

Tetralogy of Fallot is often diagnosed during infancy or soon after. However, tetralogy of Fallot may not be detected until later in life, depending on the severity of the defects and symptoms. With early diagnosis followed by appropriate treatment, most children with tetralogy of Fallot live relatively normal lives, though they'll need regular medical care and may have restrictions on exercise.

Symptoms Causes Risk factors Complications

Tetralogy of Fallot symptoms vary, depending on the extent of obstruction of blood flow out of the right ventricle and into the lungs. Signs and symptoms may include:

  • A bluish coloration of the skin caused by blood low in oxygen (cyanosis)
  • Shortness of breath and rapid breathing, especially during feeding
  • Loss of consciousness (fainting)
  • Clubbing of fingers and toes — an abnormal, rounded shape of the nail bed
  • Poor weight gain
  • Tiring easily during play
  • Irritability
  • Prolonged crying
  • A heart murmur

Tet spells

Sometimes, babies with tetralogy of Fallot will suddenly develop deep blue skin, nails and lips after crying, feeding, having a bowel movement, or kicking his or her legs upon awakening. These episodes are called Tet spells and are caused by a rapid drop in the amount of oxygen in the blood. Toddlers or older children may instinctively squat when they are short of breath. Squatting increases blood flow to the lungs. Tet spells are more common in young infants, around 2 to 4 months old.

When to see a doctor

Seek medical help if you notice that your baby has the following symptoms:

  • Difficulty breathing
  • Bluish discoloration of the skin
  • Passing out or seizures
  • Weakness
  • Unusual irritability

If your baby becomes blue (cyanotic), immediately place your child on his or her side and pull the knees up to the chest. This helps increase blood flow to the lungs. Call 911 or your local emergency number immediately.

Tetralogy of Fallot occurs during fetal growth, when the baby's heart is developing. While factors such as poor maternal nutrition, viral illness or genetic disorders may increase the risk of this condition, in most cases the cause of tetralogy of Fallot is unknown.

The four abnormalities that make up the tetralogy of Fallot include:

  • Pulmonary valve stenosis. This is a narrowing of the pulmonary valve, the flap that separates the right ventricle of the heart from the pulmonary artery, the main blood vessel leading to the lungs. Constriction of the pulmonary valve reduces blood flow to the lungs. The narrowing may also affect the muscle beneath the pulmonary valve.
  • Ventricular septal defect. This is a hole in the wall that separates the two lower chambers (ventricles) of the heart. The hole allows deoxygenated blood in the right ventricle — blood that has circulated through the body and is en route to the lungs to replenish its oxygen supply — to flow into the left ventricle and mix with oxygenated blood fresh from the lungs. Blood from the left ventricle also flows back to the right ventricle in an inefficient manner. This ability for blood to flow through the ventricular septal defect dilutes the supply of oxygenated blood to the body and eventually can weaken the heart.
  • Overriding aorta. Normally the aorta, the main artery leading out to the body, branches off the left ventricle. In tetralogy of Fallot, the aorta is shifted slightly to the right and lies directly above the ventricular septal defect. In this position the aorta receives blood from both the right and left ventricles, mixing the oxygen-poor blood from the right ventricle with the oxygen-rich blood from the left ventricle.
  • Right ventricular hypertrophy. When the heart's pumping action is overworked, it causes the muscular wall of the right ventricle to enlarge and thicken. Over time this may cause the heart to stiffen, become weak and eventually fail.

Rarely, some babies who have tetralogy of Fallot will have a hole between their heart's upper chambers (atrial septal defect), as well. When this occurs, the condition is known as pentalogy of Fallot.

While the exact cause of tetralogy of Fallot is unknown, several factors may increase the risk of a baby being born with this condition. These include:

  • A viral illness in the mother, such as rubella (German measles), during pregnancy
  • Maternal alcoholism
  • Poor nutrition
  • A mother older than 40
  • A parent with tetralogy of Fallot
  • Babies who are also born with Down syndrome or DiGeorge syndrome

All babies with tetralogy of Fallot need corrective surgery. Without treatment, your baby may not grow and develop properly. He or she is also at increased risk of serious complications, such as infective endocarditis, an inflammation of the inner lining of the heart caused by a bacterial infection.

Untreated cases of tetralogy of Fallot usually develop severe complications over time, which may result in death or disability by early adulthood.

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