What is pulmonary atresia?
Pulmonary atresia is a congenital heart defect (the baby is born with it) in which the pulmonary valve does not develop normally or remains blocked after birth. ("Atresia" means absent and pulmonary refers to the lungs.)
The structure of the heart
The heart has four chambers—the right atrium and the left atrium (plural: atria) on top and the right and left ventricles (pumping chambers) on the bottom. The heart is divided by a solid wall called the septum into two sides: the right side sends blood to the lungs to get oxygen, while the left side of the heart moves oxygen-rich blood to the rest of the body through the aorta (the main artery in the heart).
Inside the Heart
There are also four valves in the heart, which open and close to allow blood to move through the chambers:
- The tricuspid valve, located on the right side of the heart between the right ventricle and the right atrium;
- The pulmonary valve, located on the right side of the heart between the right ventricle and the pulmonary artery (the blood vessel that carries blood to the lungs);
- The mitral valve, located between the left ventricle and the left atrium;
- The aortic valve, located on the left side of the heart, between the aorta and the left ventricle.
The pulmonary valve has three flaps (also called leaflets or cusps) that normally open to let blood flow forward from the right ventricle into the pulmonary artery. The leaflets also close to prevent blood from flowing backward into the heart.
In some babies with pulmonary atresia, the right ventricle of the heart, the pulmonary artery, and the tricuspid valve may be underdeveloped. Some infants may also have a ventricular septal defect, or opening in the wall (septum) between the right and left ventricles. This opening allows oxygen-rich blood to mix with oxygen-poor blood.
If there is no pulmonary valve or if it is blocked, blood cannot flow through the pulmonary artery to reach the lungs, where it receives oxygen. Instead, oxygen-poor (blue) blood is pumped throughout the body. The lips, fingers, and toes of the infant may appear blue because of a lack of oxygen in the blood. This condition is known as cyanosis.
The fetal heart has an opening (the foramen ovale) between the pulmonary artery and the aorta. It usually closes after birth, but sometimes remains open in newborns who have pulmonary atresia. The foramen ovale allows oxygen-poor blood to pass from the right atrium to the left atrium of the heart, where it flows through the left ventricle to the aorta.
Newborns also have another passageway between the aorta and the pulmonary artery. This passageway, called the ductus arteriosus, begins to close within a few hours to days after birth. While the ductus arteriosus remains open, some oxygen-poor blood is still able to reach the lungs.
What causes pulmonary atresia?
Pulmonary atresia occurs in about 1 out of 10,000 live births. Pulmonary atresia occurs during the first eight weeks that the fetus is developing in the womb. The exact cause is unknown. Genetic factors, such as an abnormal gene or chromosomal defect, may increase the chances of heart defects in certain families. (Some children with genetic disorders may be at greater risk for developing pulmonary atresia.)
What are the symptoms of pulmonary atresia?
Symptoms of pulmonary atresia often appear within the first few hours or days of life and may include:
- Rapid breathing
- A bluish tinge to the skin, especially the lips, fingers, and toes
- Cool, pale, or clammy skin
- Breathing problems
- Fatigue or tiredness
- Poor feeding