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Tetralogy of Fallot

Tetralogy of Fallot is a condition caused by a combination of congenital heart defects (heart defects that are present at birth). The four heart defects that combine to become tetralogy of Fallot are:

  • Pulmonary valve stenosis – Pulmonary valve stenosis occurs when the pulmonary valve narrows, which leads to valve malfunction, which can cause reduced blood flow to the lungs. The pulmonary valve is the valve that separates the right ventricle from the pulmonary aorta. Narrowing can also affect the heart muscle below the valve. 
  • Ventricular septal defect – A ventricular septal defect is a hole in the septum, which is the wall that separates the two ventricles (the lower chambers of the heart). A hole in the septum allows oxygen-poor blood from the right ventricle to flow into the left ventricle where it mixes with oxygen-rich blood returning from the lungs. It also allows blood from the left ventricle to flow back to the right ventricle, which reduces the supply of oxygen-rich blood getting to the body. This can cause problems throughout the body and can weaken the heart. 
  • Overriding aorta – The aorta is the main artery that leads from the heart to the rest of the body from the left ventricle. When someone has tetralogy of Fallot, the aorta is slightly to the right so it lies above the ventricular septal defect. When the aorta is in this position, it receives blood from both ventricles, which also allows mixing of oxygen-rich and oxygen-poor blood. 
  • Right ventricular hypertrophy – All of the defects listed above can make the heart work harder than normal, which can cause the heart muscle in the right ventricle to thicken. This can cause the heart muscle to become stiffer and weaker, and it may eventually fail. 

Some people with tetralogy of Fallot have other heart defects as well, including a right aortic arch, coronary artery abnormalities, or a hole between the heart's upper chambers (an atrial septal defect).

Together, these heart defects affect the heart’s structure so it cannot oxygenate blood or pump blood from the heart to the body properly. The lack of oxygen in the blood comes from the obstruction between the heart and lungs. Instead of oxygen-poor blood pumping from the heart to the lungs where it’s supposed to pick up more oxygen, some blood pumps through the hole between the ventricles rather than to the lungs. This makes it difficult for the blood to get enough oxygen to deliver throughout the body. And when blood oxygen levels are low, children tend to have blue-ish skin.

Most cases of tetralogy of Fallot are diagnosed during infancy or early childhood, but if the defects and symptoms are mild, it may go unnoticed until later in life. 

Complications of tetralogy of Fallot

Children who have tetralogy of Fallot will need surgery to correct the four heart defects. If your child has tetralogy of Fallot and doesn’t get treated, he or she may not develop normally and may be at greater risk of serious complications. There are severe potential complications of tetralogy of Fallot, including infective endocarditis, which is a bacterial infection in the lining of the heart or heart valve.

Despite the risks if untreated, children who are diagnosed early and are treated to correct the defects live mostly normal lives.

Causes of tetralogy of Fallot

Tetralogy of Fallot develops when a child’s heart is developing during the fetal growth stage. Experts aren’t sure what causes the defects, but there are theories that poor maternal nutrition, viral illness during pregnancy, or genetics may increase risk of tetralogy of Fallot.

Children with Down syndrome or DiGeorge syndrome are at greater risk of tetralogy of Fallot.

Risk factors for tetralogy of Fallot

  • A virus, like German measles, during the mother’s pregnancy
  • Drinking alcohol excessively during the mother’s pregnancy
  • Poor maternal nutrition
  • Advanced maternal age (over 40)
  • A parent who has tetralogy of Fallot
  • Down syndrome or DiGeorge syndrome

Signs and symptoms of tetralogy of Fallot

The symptoms of tetralogy of Fallot can vary from person to person. Worse symptoms tend to coincide with greater blood flow obstruction from the right ventricle into the lungs. 

Signs and symptoms of tetralogy of Fallot may include: 

  • Cyanosis (a blue-ish tint to the skin that occurs when the blood doesn’t have enough oxygen)
  • Shortness of breath or fast breathing, especially during feeding or when physically active
  • Fainting
  • Clubbed fingers and toes
  • Insufficient weight gain during childhood
  • Feeling tired quickly when playing or being physically active
  • Irritability
  • Prolonged crying spells
  • Heart murmur
  • Tet spells

What is a tet spell?

A tet spell is the development of deep blue color to skin, nails, and lips that occurs after crying or eating or when a child is agitated. These episodes are due to a quick drop in oxygen levels in the blood. Tet spells tend to happen most in infants between two and four months old. 

When toddlers or older children have sudden drops in blood flow to the lungs, they may squat instinctively to try to catch their breath. 

When to call your child’s doctor

If you notice that your child has the following symptoms, call the doctor or go to the emergency room right away.

  • Difficulty breathing
  • Blue or blue-ish skin
  • Seizures
  • Losing consciousness
  • Unexplained weakness
  • Unusual irritability or agitation 

If your infant turns blue, place them on their side and pull their knees up to their chest. Doing this helps increase blood flow to the lungs. Then immediately call 911 or other emergency medical services.

Diagnosing tetralogy of Fallot

Blue-ish skin and a heart murmur are two of the telltale signs of tetralogy of Fallot, so if your child’s doctor notices these symptoms, he or she may refer you to a pediatric cardiologist. The cardiologist will do a physical exam and listen to your child’s heart and will most likely order tests to confirm a diagnosis.

Tests that help diagnose tetralogy of Fallot include:

  • Echocardiogram – Echocardiogram is the most common test to confirm a diagnosis of tetralogy of Fallot. This test uses sound waves to create a picture of the heart. The echocardiogram machine allows doctors to view a video screen of images of the heart beating so they can examine the heart and its pumping for abnormalities. For example, it can help the doctor see a ventricular septal defect and, if it’s there, where it’s located. It can also help determine whether the pulmonary valve and artery are normal, if the aorta is positioned normally, and if the right ventricle is functioning well. Test results can also help doctors decide upon the best treatment options.
  • Electrocardiogram (ECG or EKG) – An ECG is a test that records the electrical activity in the heart. This is a quick test that involves placing electrodes on the chest, wrists, and ankles to look for certain heart abnormalities. An ECG can help doctors determine whether there is right ventricle hypertrophy, whether the right atrium is enlarged, and if there’s a regular heart rhythm.
  • Pulse oximetry – This is a quick, simple, painless test to measure the amount of oxygen in circulating blood. The sensor can be placed on a finger or toe, and the oxygen level reading is available in seconds. This is a valuable test because children with tetralogy of Fallot often have low levels of oxygen in the blood.
  • Cardiac catheterization – This is a procedure done for two reasons: to determine the structure of the heart and to plan surgical treatment to correct the defects. During a cardiac catheterization, doctors use a thin, flexible tube called a catheter to inject dye into the heart so its structures are visible on x-ray. It can also measure oxygen and pressure levels in the heart chambers and blood vessels.

For a referral to a Beaumont pediatric cardiologist, call 855-480-KIDS (855-480-5437) or find one online.