What is the Tetralogy of Fallot?

Tetralogy of Fallot is the most common form of cyanotic congenital heart disease. Cyanosis is an abnormal bluish discoloration of the skin caused by low circulating oxygen levels in the blood. You can find more information below.

What is tetralogy of Fallot?

Tetralogy of Fallot is a rare disease condition that results from a combination of four congenital heart defects. These defects, which affect the heart’s structure, cause insufficiently oxygenated blood to flow to the heart and the rest of the body. Babies and children with tetralogy of Fallot often have blue-colored skin because their blood does not carry enough oxygen.

Tetralogy of Fallot is often diagnosed in infancy or soon after. However, depending on the severity of the defects and symptoms, it may not be detected until later in life in some adults.

With early diagnosis and subsequent appropriate surgical treatment, most children and adults with tetralogy of Fallot lead relatively normal lives but will need regular medical care throughout life and may have exercise limitations.

What causes tetralogy of Fallot?

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

The four abnormalities that make up tetralogy of Fallot include:

  • Pulmonary valve stenosis: Pulmonary valve stenosis is a condition that separates the lower right chamber of the heart (right ventricle) from the main blood vessel leading to the lungs (pulmonary artery). Narrowing of the pulmonary valve reduces blood flow to the lungs. The narrowing can also affect the muscles under the pulmonary valve. In some severe cases, the pulmonary valve does not form properly (pulmonary atresia), causing reduced blood flow to the lungs.
  • Ventricular septal defect: A ventricular septal defect is a hole (defect) that separates the two lower chambers of the heart, the left and right ventricles. The hole allows deoxygenated blood from the right ventricle to flow into the left ventricle and mix with freshly oxygenated blood from the lungs. Blood from the left ventricle also flows inefficiently back into the right ventricle. The ability of blood to flow through the ventricular septal defect reduces the supply of oxygenated blood to the body and can eventually weaken the heart.
  • Aorta override: In a normal heart, the aorta connects to the left ventricle, allowing oxygen-rich blood to flow throughout the body. In tetralogy of Fallot, the aorta is located between both the left and right ventricles. This causes oxygen-deficient blood from the right ventricle to flow into the aorta instead of the pulmonary artery. If babies with tetralogy of Fallot are left untreated, symptoms often become progressively more severe. Blood flow to the lungs may be further reduced, and severe cyanosis can cause life-threatening complications.
  • Right ventricular hypertrophy: When the heart’s pumping action works too hard, it causes the muscular wall of the right ventricle to thicken. Over time, this can cause the heart to harden, weaken, and ultimately fail.
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Some children or adults with tetralogy of Fallot may have other heart defects, such as a hole between the upper chambers of the heart (atrial septal defect), abnormalities of the right aortic arch, or coronary arteries.

Who is at risk?

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

  • A viral illness such as rubella during pregnancy
  • alcoholism during pregnancy
  • malnutrition during pregnancy
  • a mother over 40
  • A parent with tetralogy of Fallot
  • Presence of Down syndrome or DiGeorge syndrome

What are the symptoms of tetralogy of Fallot?

Many of the symptoms of tetralogy of Fallot vary depending on the degree of disease. Symptoms may include:

  • A bluish discoloration of the skin caused by low-oxygen blood (cyanosis)
  • Shortness of breath and rapid breathing, especially during feeding or exercise
  • loss of consciousness, fainting
  • An abnormal, rounded shape of the nail bed of the fingers and toes
  • bad weight gain
  • Getting tired easily during play or exercise
  • Irritability
  • prolonged crying
  • heart murmur

Sometimes, babies with tetralogy of Fallot suddenly develop deep blue skin, nails, and lips when crying or after feeding. This condition is caused by a rapid decrease in the amount of oxygen in the blood and is most common in young infants 2 to 4 months old. Young children or older children may instinctively squat when they are short of breath. Squatting increases blood flow to the lungs.

When should you see a doctor?

You should seek medical attention if you notice that your baby has the following symptoms:

  • difficulty breathing
  • bluish discoloration of the skin
  • fainting or seizures
  • Weakness
  • abnormal irritability

If your baby becomes blue (cyanotic), take your baby with you and pull your baby’s knees towards your chest. This helps increase blood flow to the lungs. Then call the emergency services without wasting time.

How is tetralogy of Fallot diagnosed?

First, the affected person’s or child’s cardiologist will perform a physical examination and use several tests to confirm the diagnosis. These tests may include:

  • Echocardiography: Echocardiograms use high-pitched sound waves to create an image of the heart. Sound waves bounce off the heart and produce moving images that can be viewed on the video screen. This test is often used to diagnose tetralogy of Fallot. The doctor can diagnose if and where there is a ventricular septal defect, whether the structure of the pulmonary valve and pulmonary artery is normal, and if there are other heart defects. This test can also help the doctor plan treatment for the condition.
  • Electrocardiogram: An electrocardiogram records the electrical activity in the heart each time it contracts. During this procedure, wire patches (electrodes) are placed on the patient’s chest, wrists, and ankles. The electrodes measure the electrical activity recorded on the paper. This test helps determine enlargement of the right ventricle (right ventricular hypertrophy), enlargement of the right atrium, and whether the heart rhythm is regular.
  • Chest X-ray: A chest X-ray can show the structure of the heart and lungs. Many things that point to tetralogy of fallot can be noticed on a chest X-ray.
  • Oxygen level measurement (pulse oximetry): This test uses a small sensor that can be placed on a finger or toe to measure the amount of oxygen in the blood.
  • Cardiac catheterization: Doctors can use this test to evaluate the structure of the heart and plan surgical treatment. During this procedure, the doctor inserts a thin, flexible tube (catheter) into an artery or vein in the arm, groin, or neck and connects it to the heart. The doctor then injects a dye through the catheter to make the heart structures visible on X-ray pictures. Cardiac catheterization also measures pressure and oxygen levels in the chambers and blood vessels of the heart.
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How is tetralogy of Fallot treated?

The only effective treatment for tetralogy of Fallot is surgery. Surgical options include intracardiac repair or a temporary procedure using a shunt. However, most infants and older children have intracardiac repair.

Doctors will determine the most appropriate surgery and the timing of the surgery according to the condition of the affected person.

In some cases, the affected person may need medication to keep the opening between the two major blood vessels in the heart open. This may help maintain blood flow from the heart to the lungs prior to intracardiac repair.

Intracardiac repair

This open heart surgery is usually done during the first year after birth and includes several repairs. Adults with tetralogy of Fallot may rarely undergo this procedure if they did not undergo surgical repair as a child.

The surgeon places a patch over the ventricular septal defect to close the hole between the lower chambers (ventricles) of the heart.

It also repairs or replaces the narrowed pulmonary valve and widens the pulmonary arteries to increase blood flow to the lungs.

After this procedure, the right ventricle wall will return to its normal thickness, as the right ventricle does not have to work as hard to pump blood. After intracardiac repair, the oxygen level in the blood increases and the symptoms decrease.

Temporary surgery

Sometimes, babies need to undergo temporary (palliative) surgery before intracardiac repair to improve blood flow to the lungs. This procedure can be done if the baby was born prematurely or has immature (hypoplastic) pulmonary arteries.

In this procedure, the surgeon creates a bypass (shunt) between a large artery branching from the aorta and the pulmonary artery.

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When your baby is ready for intracardiac repair, the surgeon removes the shunt during the intracardiac repair procedure.

after surgery

While most infants and adults are successful after intracardiac repair, long-term complications are common. Complications can include:

  • chronic pulmonary regurgitation in which blood leaks back through the pulmonary valve into the pumping chamber (right ventricle)
  • Other heart valve problems, such as blood leaking from the tricuspid valve
  • Holes in the wall between the ventricles (ventricular septal defects) that may continue to leak after repair or need to be repaired again
  • Improper functioning right ventricle or left ventricle
  • Irregular heartbeats (arrhythmias)
  • coronary artery disease
  • Aortic root dilatation, in which the ascending aorta expands
  • sudden cardiac death

For people with tetralogy of Fallot, complications can continue throughout childhood, adolescence, and adulthood. Most adults with repaired tetralogy of Fallot may require another procedure or intervention in their lifetime. Regular follow-up with a cardiologist trained in the care of people with congenital heart disease who can evaluate the patient and determine the appropriate timing of another intervention or procedure is essential.

Sometimes blood flow to the lungs may still be restricted after intracardiac repair. Infants, children, or adults with these complications may require additional surgeries. More commonly, there is leakage from the repaired pulmonary valve. Most adults with repaired tetralogy of Fallot may have a pulmonary valve leak (insufficiency) and may need to have the pulmonary valve replaced during their lifetime. Your cardiologist will determine the optimal timing for this procedure.

Arrhythmias are common after repair and can be treated with medications, a procedure to treat arrhythmias (ablation), or a special pacemaker device that treats life-threatening heart rhythms.

Additionally, as with any surgery, there is a risk of infection, unexpected bleeding, or blood clots.

Ongoing care

After surgery, the person involved will need lifelong care with a cardiologist trained to treat congenital heart disease, including routine follow-up appointments to make sure the initial surgery or procedure was successful and to monitor anything.

The doctor may perform physical examinations and tests at regular follow-up appointments to assess and monitor the affected person’s condition.

The doctor may also recommend that the patient limit vigorous physical activity, especially if there is pulmonary valve leakage, occlusion, or arrhythmias.

Sometimes antibiotics are recommended during dental procedures to prevent infections that can cause endocarditis. Antibiotics are especially important for people with pre-existing endocarditis, artificial valves, or prosthetic material.

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