Tetralogy of Fallot: A Critical Congenital Heart Defect

Tetralogy of Fallot (pronounced te-tral-uh-jee of Fal-oh) is a congenital heart defect, present at birth, that develops when a baby's heart does not form correctly during pregnancy. About 1 in 2,041 babies in the United States, about 1,754 a year, are born with it.

Four defects in one

1. Ventricular septal defect (VSD): a hole in the wall between the heart's two lower chambers, the ventricles.
2. Pulmonary stenosis: a narrowed pulmonary valve and main pulmonary artery.
3. An enlarged aortic valve: the aortic valve, which leads to the aorta, is enlarged, sits directly over the VSD and receives blood from both ventricles, instead of only the left as in a typical heart.
4. Ventricular hypertrophy: the muscular wall of the lower right chamber is thicker than normal.

Because a baby with tetralogy of Fallot may need surgery or other procedures soon after birth, it is considered a critical congenital heart defect.

Signs

The defect can reduce the oxygen in blood flowing to the body, so babies may have bluish skin, called cyanosis. Some are not blue at birth but later have sudden episodes of bluish skin while crying or feeding, called tet spells.

Infants with tetralogy of Fallot or other conditions that cause cyanosis may have:

• a higher risk of endocarditis, an infection of the layers of the heart;
• a higher risk of arrhythmia, irregular heart rhythms;
• dizziness, fainting or seizures from low blood oxygen;
• delayed growth and development.

Causes

For most babies the cause is unknown. Some heart defects come from changes in genes or chromosomes, and a combination of genes and other factors, such as things in the mother's environment, what she eats or drinks, or the medicines she takes, may raise the risk.

Diagnosis

• During pregnancy. A prenatal ultrasound may detect the defect, and a fetal echocardiogram, a more detailed ultrasound of the baby's heart, can confirm it and show how the heart is working.
• After birth, when it is usually found, often after a tet spell. Bluish skin or a heart murmur may raise suspicion, and an echocardiogram, an ultrasound of the heart, is the most common confirming test.
• Newborn pulse oximetry screening, which measures oxygen in the blood, can pick up some babies with tetralogy of Fallot before they show symptoms.

Treatment and the long term

Surgery soon after birth widens or replaces the pulmonary valve, enlarges the passage to the pulmonary artery and patches the VSD, improving blood flow to the lungs and body.

Most children go on to live active, healthy lives. They need routine checkups with a heart doctor throughout life to watch their progress and check for other conditions, and as adults some may need more surgery or care.

Sources

• CDC, "Tetralogy of Fallot": https://www.cdc.gov/heart-defects/about/tetralogy-of-fallot.html
• CDC, newborn screening for critical congenital heart defects: https://www.cdc.gov/heart-defects/screening/index.html