What to know about tetralogy of Fallot

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Tetralogy of Fallot is a congenital heart defect that develops while the fetus is in the womb.

It can affect how the blood flows in the heart and to the lungs, therefore affecting how much oxygen reaches the rest of the body. This can cause the skin to become a bluish color.

Doctors refer to congenital heart diseases that cause a lack of oxygen as “cyanotic congenital heart disease.” Tetralogy of Fallot is the most common cause of these conditions. Research suggests it accounts for 7–10% of congenital anomalies of the heart.

A 2022 review of research suggests that tetralogy of Fallot affects about 3 in every 10,000 live births.

Tetralogy of Fallot consists of four different abnormalities of the heart. These include the following:

Pulmonary stenosis

This refers to a narrowing of the pulmonary valve in the heart, which is responsible for the flow of blood from the lower right chamber into the artery that supplies blood to the lungs.

Ventricular septal defect

The ventricular septum is a wall in the heart that separates the two sides. The bottom left side of the heart stores oxygen-rich blood. The bottom right side stores oxygen-poor blood. The septal wall stops the two types of blood from mixing. A ventricular septal defect is a hole in the septal wall, which can cause the two types of blood to mix.

Right ventricular hypertrophy

Right ventricular hypertrophy refers to a thickening of the muscles in the wall of the lower right chamber of the heart. This is due to the heart having to work extra hard to pump blood through the narrowed pulmonary valve and the extra flow of blood coming in through the ventricular septal defect.

Overriding aorta

The aortic valve is typically on the lower left chamber of the heart and is responsible for the flow of oxygen-rich blood to the rest of the body.

When a person has tetralogy of Fallot, the aortic valve is between the lower left and right chambers of the heart, next to the ventricular septal defect. This causes oxygen-poor blood to flow through the aortic valve instead of oxygen-rich blood.

Symptoms of tetralogy of Fallot may vary and can range from mild to severe. They may be present from birth.

The most common symptom is a bluish coloring to the skin, particularly the lips, tongue, and hands. This is due to the lack of oxygen in the blood.

Other symptoms can include:

• difficulty breathing, especially after or during physical activity
• tiring easily
• dizziness
• slow weight gain
• slow physical growth
• poor appetite
• clubbing, which refers to a widening of the finger and toe tips with nails that overhang
• heart murmur
• hypercyanotic attacks, which cause a person to suddenly:
  • become extremely blue or paler than usual
  • have difficulty breathing
  • faint
  • experience a seizure

Additionally, someone with tetralogy of Fallot may be more at risk of developing endocarditis and arrhythmias.

Healthcare professionals do not know the exact cause of tetralogy of Fallot in many babies. However, research suggests that tetralogy of Fallot may occur due to a combination of certain gene mutations, environmental factors that affect the fetus, or substances that a pregnant person consumes.

Risk factors that may lead to a pregnant person having a baby with tetralogy of Fallot include:

• consuming alcohol while pregnant
• having diabetes
• having poor nutrition
• experiencing certain viral illnesses
• taking certain medications while pregnant
• being over the age of 40 years while pregnant

Learn what to avoid during pregnancy.

There are also several health conditions that may be risk factors for tetralogy of Fallot, including:

• genetic disorders, including Down, Alagille, and DiGeorge syndromes
• birth defects of the spine
• heart defects
• abnormalities of the limbs and airways

Research from 2022 suggests that, in approximately 50% of people who have tetralogy of Fallot, a diagnosis occurs with an ultrasound scan of the heart of the fetus.

After birth, there are several indicators of tetralogy of Fallot that a doctor may discover during a physical examination, including:

• an infant turning blue, or paler than usual, while feeding or crying
• a bluish tint to the skin, lips, or tongue
• a whooshing sound when the heart beats, which can indicate a heart murmur

A doctor may then recommend several tests to diagnose tetralogy of Fallot, including:

• an electrocardiogram, which assesses the electrical activity in the heart and how regular the heartbeat is
• an echocardiogram, which is a type of ultrasound scan to examine the heart and surrounding blood vessels
• cardiac catheterization, which is a surgical procedure that uses a catheter to examine the inside of the heart

A doctor may perform pulse oximetry, which is a newborn screening test that can estimate levels of oxygen in the blood. When an infant has low levels of oxygen, it can be a sign of tetralogy of Fallot. Pulse oximetry can help identify tetralogy of Fallot before an infant displays any symptoms.

A person who is born with tetralogy of Fallot may require surgery shortly after they are born or within the first few weeks of life.

Surgery to treat tetralogy of Fallot involves addressing the pulmonary stenosis and ventricular septal defect that are present. Once a doctor treats these two issues, the other two typically resolve on their own.

The surgical procedures to treat tetralogy of Fallot can include:

• temporarily placing a shunt, or tube, between the aorta and the pulmonary artery
• widening or replacing the pulmonary valve and artery
• placing a patch over the hole in the septum

Before a person has surgery, a doctor may make recommendations to help relieve symptoms of tetralogy of Fallot. These can include:

• taking heart medication to help regulate the heartbeat
• supplementing with oxygen or morphine, which can help raise oxygen levels in the blood
• taking sodium bicarbonate to reduce levels of acid in the blood
• taking medication such as propranolol to help prevent hypoxia
• giving antibiotics to an infant to help prevent infection

Tetralogy of Fallot is a group of four heart abnormalities that can develop while a fetus is in the womb.

The four heart abnormalities can affect how the blood flows in the heart and how much flows to the lungs. This can result in a lack of oxygen in the blood, which can lead to an infant having episodes of bluish skin, difficulty breathing, and other symptoms.

Tetralogy of Fallow is a critical condition that typically requires surgery to treat the abnormalities shortly after birth. A doctor may diagnose tetralogy of Fallow during pregnancy or after the infant is born.

A person should seek medical attention if they think an infant in their care is experiencing symptoms of tetralogy of Fallot.