Tetralogy of Fallot (TOF)

Tetralogy of Fallot, or TOF, is a critical congenital (present at birth) heart defect that impacts the flow of blood through the heart. People with Tetralogy of Fallot have four specific defects, including a boot-shaped heart and an overriding aorta. The condition is usually diagnosed soon after birth. Babies may have tet spells, also known as tetralogy spells, which are episodes of bluish skin. Most babies with tetralogy of Fallot need tetralogy of Fallot surgery to repair the heart before they’re about six months old. With surgery, 90% of people with TOF survive to adulthood and lead healthy lives.

Continue reading to learn more about TOF, including how tetralogy of Fallot impacts the body, what to expect from surgery and the prognosis for your child. 

How Tetralogy of Fallot Affects the Body

The heart is responsible for bumping oxygen-rich blood throughout the body. However, tetralogy of Fallot causes blood flow to be reduced. Because of that, oxygen doesn’t reach the body as well as it does in healthy individuals. This is why babies with TOF are often blue, or experience a tet spell (periods of turning blue) when crying or eating.

What Are the 4 Abnormalities of the Heart in Tetralogy of Fallot?

Four characteristic defects are present in the heart when a person has tetralogy of Fallot. They are:

• Ventricular septal defect (VSD): This is a hole between the heart's two lower chambers, called ventricles. The hole disrupts normal blood flow through the heart.
• Right ventricular hypertrophy: This is a condition where the muscle of the right ventricle is thicker, making it more difficult for the heart to pump. 
• Overriding aorta: The aorta, the largest artery in the body, sits over the ventricular septal defect hole, allowing it to open to both chambers of the heart. In a healthy heart, the aorta opens only to the left chamber.
• Pulmonary valve stenosis (PS): This is a narrowing of the pulmonary valve, which allows blood to flow from the heart's right ventricle to the lungs. 

Tetralogy of Fallot Causes

Researchers don’t know what causes tetralogy of Fallot. However, they have identified risk factors for the condition, including having other chromosomal disorders, including Down syndrome, Alagille syndrome, and DiGeorge syndrome.

In addition, these conditions during pregnancy can increase the risk of a fetus that has tetralogy of Fallot:

• A mother who is over 40
• Alcoholism
• Diabetes
• Poor nutrition
• Rubella and other viral infections

Tetralogy of Fallot Symptoms

The most common symptom of tetralogy of Fallot is a blue tinge on the skin, lips and nails. This is a condition known as cyanosis, which happens when there is not enough oxygen in the blood. In people with darker skin, cyanosis can cause the skin to look gray or white. 

Babies with tetralogy of Fallot can experience tet spells, or tetralogy spells, which happen when their oxygen levels drop rapidly, causing cyanosis. This happens most often when an infant is crying or feeding. During these spells, babies may:

• Turn blue-ish
• Have difficulties breathing
• Go limp
• Lose consciousness

Other symptoms of tetralogy of Fallot include:

• Trouble breathing
• Fatigue
• Fussiness
• A heart murmur
• Difficulties eating or gaining weight

When to Seek Medical Care

If your child turns blue while feeding or crying, seek medical care immediately. A tet spell is often the first sign of tetralogy of Fallot. If this happens, or if your healthcare provider notices other symptoms, like a heart murmur or a baby that isn’t gaining weight, they’ll order additional tests to diagnose the condition. 

How Is Tetralogy of Fallot Diagnosed?

Sometimes, tetralogy of Fallot is detected before a fetus is born using an ultrasound. However, the condition is more commonly diagnosed after birth.

When a baby is born, healthcare providers may notice symptoms like a heart murmur or a blueish tinge in the hospital. The condition can also be detected during a newborn screening when doctors use pulse oximetry to measure a baby’s oxygen levels. But a tet spell is often the first sign that a child has tetralogy of Fallot.

After a symptom is noticed, healthcare providers will order an echocardiogram, or ultrasound of the heart. This test can confirm the presence of the four abnormalities of tetralogy of Fallot, allowing your healthcare provider to diagnose. 

How Is Tetralogy of Fallot Treated?

Babies with tetralogy of Fallot need corrective surgery. Without surgery, most people with the condition die before they are 20. But with surgery, about 90% of people with the condition live into adulthood and have full, healthy lives.

Temporary operation

Sometimes, doctors use a temporary operation to help relieve symptoms of tetralogy of Fallot. This surgery is not open-heart surgery, so it’s used for very young or fragile infants. A shunt, or hollow tube, is placed in the heart to help normalize blood flow until a corrective surgery is done.

Complete repair

During a tetralogy of Fallot repair surgery, surgeons address each of the four abnormalities of this condition by:

• Closing the ventricular septal defect, using a patch
• Removing thickened muscle below the pulmonary valve
• Repairing or removiing the obstructed pulmonary valve and enlarge the branch pulmonary arteries
• If needed, placing a tube between the right ventricle and the pulmonary artery to improve blood flow

What’s the Outlook for Someone With Tetralogy of Fallot?

With treatment, the outlook for infants with tetralogy of Fallot is good. Children who have TOF will need to continue to see a cardiologist, even after the condition is repaired. Some children will need to limit activities like contact sports, while others will be able to do most activities. 

Children can experience some complications, including arrhythmias, or irregular heartbeats. In severe cases, these can cause dizziness or fainting. Your child should continue to see a cardiologist throughout their life if they were born with tetralogy of Fallot.

Summary

Tetralogy of Fallot is a congenital heart condition that some people are born with. The condition includes four distinct defects in the heart, which impact the organ’s ability to pump oxygen throughout the body. Tetralogy of Fallot is serious and requires open-heart surgery to correct. However, with proper treatment and follow up, 90% of people with the condition will live into adulthood.