Pulmonary atresia is a heart defect that prevents adequate amounts of blood from reaching the lungs. It is a rare congenital heart defect that can lead to infant death if not treated soon after birth. Most infants need surgery to correct it soon after birth. In the United States, about 1 in every 7,100 babies is born with pulmonary atresia.
Pulmonary atresia occurs when the valve between the right side of the heart and the artery leading to the lungs does not form.
In PA-IVS and PA-VSD, symptoms occur because the body does not receive the oxygen-rich blood it needs.
Treatments for pulmonary atresia depend on the type and severity of the heart defect. With proper treatment and follow-up, infants can expect to live long and healthy life.
What is Pulmonary Atresia?
Pulmonary atresia is a heart defect that is present at birth. The heart valve between the right side of the heart and the main blood vessel leading to the lungs (the pulmonary artery) does not form correctly; thus, blood cannot flow from the heart to the lungs.
Because blood cannot flow directly from the heart into the pulmonary artery, it must use other blood vessels to bypass the unformed valve. Often the foramen ovale, a hole between the two sides of the heart, will remain open to allow blood to flow to the lungs. Sometimes doctors will need to give the infant medicine to keep the ductus arteriosus open. The ductus arteriosus is a hole between the pulmonary artery and the aorta (the large artery taking blood from the heart to the body). Usually, both of these holes close very soon after birth, but without them, an infant with pulmonary atresia will not survive long.
Types of Pulmonary Atresia
Doctors divide pulmonary atresia into two types:
Pulmonary Atresia with an Intact Ventricular Septum (PA-IVS)
In PA-IVS, the valve between the heart and the large artery leading to the lungs, the pulmonary artery, is not formed correctly. In addition, the wall between the two sides of the heart is intact. As a result, not much blood can reach the right side of the heart, and it does not develop fully. After birth, the small right side of the heart cannot pump effectively, and since the pulmonary valve did not form, the artery leading to the lungs is also too small.
Abnormal connections may also develop between the right side of the heart and the blood vessels going to the heart muscle, which can damage the heart muscle.
Unless the ductus arteriosus (the hole between the two main arteries) remains open, an infant with PA-IVS will not live long.
Pulmonary Atresia with a Ventricular Septal Defect (PA-VSD)
In PA-VSD, a hole between the two sides of the heart lets blood flow between the right and left sides. This hole is called a ventricular septal defect (VSD). The blood flowing into the right side of the heart allows it to form and develop correctly, but the blood still cannot flow through the unformed pulmonary valve.
The VSD allows all the blood that the heart cannot pump to the lungs to flow to the body. Because of this, the body receives very little oxygen-rich blood.
So extra (collateral), smaller arteries usually form before birth to allow blood to flow to the lungs. Usually, these arteries are not formed correctly and are too small at one end, making it difficult for the right side of the heart to pump enough blood to the lungs.
Causes and risk factors
Although the exact cause of pulmonary atresia is not understood, scientists and doctors believe it occurs due to an injury arising during certain critical stages of fetal development. Risk factors associated with damage to a developing heart include:
- Certain drugs are taken by the mother during pregnancy
- Poorly controlled diabetes during pregnancy
- Congenital heart disease in either parent
- Smoking before or during pregnancy
- Pregnancy occurring in older women
Most cases of pulmonary atresia are diagnosed during pregnancy or very soon after birth.
Prenatal screening can often detect heart defects before an infant is born. In addition, follow-up tests and screenings, such as a fetal echocardiogram, may allow doctors to diagnose the exact defect and be ready to treat it as soon as the baby is born.
If not detected before birth, a pulse oximetry test may alert the doctor to a problem during newborn screening. For example, low oxygen levels in a newborn's blood can indicate a critical heart defect before symptoms arise, allowing doctors to begin treatment early.
If the newborn screening fails to detect a problem, symptoms of pulmonary atresia arise very soon after birth. Symptoms may include:
- heart murmur heard through a stethoscope
- white or bluish hue to the skin (cyanosis)
- excessive sleepiness
- difficulty breathing
- poor feeding
Doctors will order additional tests, such as an echocardiogram, an EKG, or a heart catheterization, to determine the problem if a heart condition is suspected.
One of the first treatments may be to administer medicine to keep the ductus arteriosus open after birth, allowing better blood flow to the lungs while considering and implementing other treatment options.
Long-term treatments for pulmonary atresia depend on the severity of the heart defect.
A doctor may be able to perform cardiac catheterization and place a stent in the ductus arteriosus to keep it open long-term.
Babies may need surgery to replace the unformed pulmonary valve and repair holes in their hearts. In addition, if a baby has PA-IVS, and the right side of their heart does not develop enough to pump blood effectively, they may need multiple surgeries.
In severe cases of PA-VSD, babies may need a heart transplant.
Any form of pulmonary atresia has a poor outlook if left untreated. However, with proper treatment, most infants with pulmonary atresia will have a much better chance of surviving.
These children will need regular checkups with a pediatric cardiologist. Even as adults, these follow-up appointments are vital to check for other heart conditions that may develop. In some cases, further surgeries may be necessary.