Tetralogy of Fallot

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at May 27, 2016
StartDiseasesTetralogy of Fallot

Tetralogy of Fallot (or TOF) is a rare condition that occurs when four heart defects are present at birth. These defects affect the structure of the heart, and result in poorly-oxygenated blood. People suffering from TOF often have a blue tint to their skin due to the lack of oxygen. Typically it is diagnosed while a person is an infant, but depending on the severity of the condition, it can go unnoticed until later in life. When tetralogy of Fallot is diagnosed early and the patient has successful heart surgery, he or she has a good chance to live a normal healthy life, albeit with some restrictions on strenuous exercise.

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Definition & Facts

Tetralogy of Fallot (TOF) is one of the most common cyanotic heart defects in the world. The Centers for Disease Control and Prevention estimate that TOF is present in 1 out of every 2,589 live births. Currently, TOF accounts for roughly 7-10% of congenital heart defects worldwide. It is named after a French physician, Etienne-Louis Arthur Fallot, who documented the condition in the late nineteenth century. The four conditions that make up tetralogy of Fallot are:

Tetralogy of Fallot drastically affect people's lives--it drastically limits the amount of physical activity their hearts can handle, and requires lifelong care and examination by a cardiologist. Fortunately, medical technology has advanced to the point where TOF sufferers can still lead a long, mostly normal life. 

Symptoms & Complaints

TOF results in a mix of oxygenated and deoxygenated blood in the left ventricle of the heart which leads to episodes of cyanosis (a bluish tint to the skin, lips, teeth, and fingernails). Babies with cyanosis may experience "tet spells," during which their skin turns blue, they have difficulty breathing, and may even lose consciousness.

Some other common symptoms among those with tetralogy of Fallot include difficulty gaining weight, tiring quickly from playing or eating, and sustained crying spells. Children who have TOF may also develop a condition known as clubbing, which refers to the rounding or widening of the bones or skin around the fingertips.

Causes

The cause of tetralogy of Fallot isn't fully understood, but there is believed to be a strong genetic link. TOF often occurs with other genetic conditions. For example, children born with genetic disorders like Down syndrome and DiGeorge syndrome have higher rates of congenital heart defects like TOF. 

There are several known factors and conditions that can occur during pregnancy which elevate the risk of having a child with tetralogy of Fallot. One contributing factor is the mother contracting rubella (German measles) or other viral infections while she is expecting. Poor nutrition during pregnancy is another contributing factor, as is alcohol use. Studies have shown that TOF rates are also noticeably higher when the mother is older than 40 or has diabetes.

Diagnosis & Tests

If doctors suspect that a child has tetralogy of Fallot, they will run a series of tests. A common first step is to perform a pulse oximetry test by placing a small sensor on a baby's toe or finger to measure the oxygen levels in the baby's blood. If the levels are high enough to confirm the doctor's suspicions, further diagnostic tests will be performed.

Echocardiography, which uses sound waves to produce an image of the heart, is now the most common method used to diagnose tetralogy of Fallot. It allows doctors to determine whether or not a ventricular septal defect exists in the heart, as well as the defect's location. Echocardiography also allows doctors to see the structure of the pulmonary valve and artery, if the right ventricle functions properly, and if the aorta is properly positioned.

Doctors may also perform chest X-rays so they can examine the structure of a baby's lungs and heart. This is useful, because it can reveal a common sign of TOF: a "boot-shaped" heart with an enlarged right ventricle.

Treatment & Therapy

If an infant experiences a 'tet' spell, it is a medical emergency. The best thing to do is place the baby on his or her side, then pull the baby's knees up to their chest--this increases blood flow to the baby's lungs. In the case of these tet spells, it is important to call 911 or the local emergency number immediately.

The only effective treatment for tetralogy of Fallot is surgery. The options for surgery vary, but the most common surgery for infants and older children is intracardiac repair. Intracardiac repair is an open-heart surgery that is usually performed during the first year of a baby's life. The surgeon patches the ventricular septal defect to close the gap between the heart's lower chambers. The surgery also involves repairing or replacing the narrow pulmonary valve and widening the pulmonary arteries to increase the flow of blood to the lungs.

After the intracardiac repair, the oxygen levels in the baby's blood increases and the symptoms will occur much less frequently. Doctors may conduct physical examinations and order tests and regular follow-up appointments to monitor and evaluate the child's condition. Usually, doctors recommend that these children limit physical activity, particularly in cases where there is pulmonary valve obstruction, cardiac arrhythmias, or leakage.

Prevention & Prophylaxis

Because the causes of tetralogy of Fallot can be mysterious, or it is passed down genetically, it is a difficult condition to prevent. A healthy pregnancy is the most effective method to preventing TOF. A proper, nutrient-rich diet is a good starting point. Abstaining from alcohol during pregnancy is one of the most important factors for a baby's healthy development. For children with the condition, abstaining from exercise that strains the heart is the best way to prevent complications.