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Tetralogy of Fallot

Tetralogy of Fallot (fuh-LOE) is an uncommon condition consisting of four ("tetra") defects within the heart structures of infants and young children. Together these defects cause reduced blood flow to the lungs and mixing of blood from both sides of the heart. This results in oxygen-poor blood flowing out of the heart and into the body. Consequently, infants and children with tetralogy of Fallot usually have blue-tinged skin (cyanosis).

Tetralogy of Fallot, which is present at birth, is usually diagnosed during infancy. However, it may not be detected until later in life, depending on the severity of the heart defects and symptoms. Tetralogy of Fallot occurs in about five out of every 10,000 babies and affects males and females equally. With early diagnosis followed by corrective surgery and ongoing care, the majority of children with tetralogy of Fallot survive to adulthood.

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 the majority of cases the cause is unknown.

Tetralogy of Fallot is named after a doctor who described four heart abnormalities common to several of his patients in 1888. This group of abnormalities includes :
  • Ventricular septal defect. In this condition, there's a hole in the wall that separates the two ventricles of the heart. Oxygen-poor blood from the right ventricle mixes with oxygen-rich blood from the left ventricle, which pumps blood out to the body.
  • 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. If the pulmonary valve is constricted, the heart has to pump harder to push blood through the valve and into the pulmonary artery.
  • Overriding aorta. Normally the aorta 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 unoxygenated blood from the right ventricle with the oxygenated blood from the left ventricle.
  • Right ventricular hypertrophy. In this condition, excessive heart pumping 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.

Risk Factor:
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 virus illness of the mother, such as rubella (measles), during pregnancy
  • Maternal alcoholism
  • Poor nutrition
  • A mother older than 40
  • A parent who had tetralogy of Fallot
Children born with Down syndrome, a genetic condition resulting from an extra 21st chromosome, are also at increased risk of having tetralogy of Fallot.

When to seek medical advice:
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 your local emergency number immediately.

Signs and symptoms of tetralogy of Fallot vary, depending on the extent of obstruction of blood flow out of the right ventricle and into the lungs. Typical signs and symptoms may include:
  • A bluish coloration of the skin caused by blood low in oxygen (cyanosis)
  • Shortness of breath and rapid breathing
  • Loss of consciousness (fainting)
  • Clubbing of fingers and toes (an abnormal, rounded shape of the nail bed)
  • Lack of appetite
  • Poor weight gain
  • Tiring easily during play
  • Irritability
Infrequently, babies with tetralogy of Fallot will suddenly develop deep blue skin, nails and lips after crying, feeding or upon awakening. These episodes are called "Tet spells" and result from 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.

After your baby is born, your baby's doctor may suspect tetralogy of Fallot if the baby has blue-tinged skin or if a heart murmur — an abnormal whooshing sound caused by turbulent blood flow — is heard in your child's chest. By using several tests, your doctor can confirm the diagnosis.
  • Chest X-ray. X-rays produce pictures by passing an X-ray beam through a patient. The beam is absorbed in different amounts by body structures. A typical sign of tetralogy of Fallot on X-ray film is a "boot-shaped" heart, because the right ventricle is enlarged.
  • Complete blood count. This is a test to measure the number of each type of cell in the blood. In tetralogy of Fallot, the number of red blood cells may be abnormally high (erthrocytosis) as the body attempts to increase the oxygen level in the blood.
  • Echocardiography. Echocardiograms use high-pitched sound waves to produce an image of the heart. Sound waves bounce off your baby's heart and produce moving images that can be viewed on a video screen. This test is used to diagnose tetralogy of Fallot by assessing whether a ventricular septal defect is present, the structure of the pulmonary valve, the function of the right ventricle and the position of the aorta.
  • Electrocardiogram. An electrocardiogram records the electrical activity in the heart each time it contracts. During this procedure, patches with wires (electrodes) are placed on your baby's chest, wrists and ankles. The electrodes measure electrical activity, which is recorded on paper. This test helps determine if your baby's right ventricle is enlarged (ventricular hypertrophy) and if the heart rhythm is regular.
  • Cardiac catheterization. During this procedure, your doctor inserts a thin flexible tube (catheter) into an artery or vein in your baby's groin and weaves it up to his or her heart. A dye is injected through the catheter to make your baby's heart structures visible on X-ray pictures. The catheter also measures pressure in the chambers of the heart and in the blood vessels.
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, or stroke, a blood clot in the brain.

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

Most babies with tetralogy of Fallot need a type of surgery called intracardiac repair, which is typically performed during the first year of life. During this procedure, the surgeon places a patch over the ventricular septal defect to close the hole between the ventricles. He or she also repairs the narrowed pulmonary valve and widens the pulmonary arteries to increase blood flow to the lungs. After intracardiac repair, the oxygen level in the blood increases and your baby's symptoms will lessen.

Occasionally babies need to undergo a temporary surgery before having intracardiac repair. If your baby was born prematurely or has pulmonary arteries that are underdeveloped (hypoplastic), doctors will create a bypass (shunt) between the aorta and pulmonary artery. This bypass increases blood flow to the lungs. When your baby is ready for a full repair, the shunt will be removed.

After the surgery
While most babies do well after intracardiac repair, complications are possible. The most frequent are chronic pulmonary regurgitation, in which blood leaks through the pulmonary valve, and an irregular heartbeat. Sometimes blood flow to the lungs is still restricted after intracardiac repair. Babies with these complications may require another surgery, and in some cases, their pulmonary valves may be replaced by artificial valves. In addition, there's a slight risk of infection, unexpected bleeding or blood clots.

After surgery your baby will require continuing care. Your doctor will schedule routine check-ups with your child to make sure that the procedure was successful and to monitor for any new problems. He or she may also recommend that your child limit physical activity or take antibiotics during dental procedures to prevent infections.

While there's no known prevention for tetralogy of Fallot, it's important to follow your doctor's advice about taking care of yourself during pregnancy. Following a balanced diet and abstaining from alcohol and tobacco will increase the chances that your baby will be born healthy.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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