What is Pulmonary Atresia (PA)?
Pulmonary atresia (PA) is a complicated congenital (present at birth) heart defect. It occurs due to abnormal development of the fetal heart in the first trimester of pregnancy.
The pulmonary valve is between the right ventricle (RV) and the pulmonary artery. It is formed by three leaflets that function like a one-way door. This allows oxygen-depleted blood that has returned from the body to the right side of the heart to flow from the right pumping chamber (RV) out to the lungs to pick up oxygen. This valve closes as the RV relaxes. This way the blood does not go backwards into the right ventricle.
With pulmonary atresia, problems with valve development prevent the leaflets from opening. This can either be a problem with how the valve itself has formed (membranous pulmonary atresia) or there may be thick muscle under the valve area with no clear leaflets (muscular pulmonary atresia). That means blood cannot flow forward from the right ventricle to the lungs. Before birth, while the fetus is developing, they are safe while the placenta provides oxygen for the baby. The lungs are not being used to oxygenate the blood. Blood entering the right side of the fetal heart goes through an opening between the collecting chambers (atrium) called the foramen ovale. This allows oxygen-rich (red) blood from the placenta to go through to the left side of the heart. It then goes to the body.
In some cases, there may be a second opening. The opening may be in the ventricular wall (between the right and left pumping chambers). This allows blood in the right ventricle a way out. This opening is called a ventricular septal defect (VSD). If there is no VSD (also called intact ventricular septum), the right ventricle gets little blood flow before birth. It does not develop fully and can be much smaller than normal.
At birth, when the baby is separated from the placenta, the lungs open on the first breath. They must do the work of oxygenating the baby’s blood. With no pulmonary valve opening present, blood needs another way to reach the lungs and get oxygen.
The foramen ovale normally closes in the first few months of life, but often stays open in this situation. It allows oxygen-poor (blue) blood to go from the right atrium to the left atrium. From there, it goes to the left ventricle, out the aorta, to the body. This situation cannot support life long-term. Oxygen-poor (blue) blood cannot meet the body's demands. Fetuses and newborns also have a connection between the aorta and the pulmonary artery. This is called the ductus arteriosus. It allows some blood to pass into the lungs in order to pick up more oxygen. Unfortunately, this ductus arteriosus normally closes within a few hours or days after birth once the baby starts breathing on their own. As the ductus arteriosus closes, oxygen levels will decrease if the child is not treated with life-saving medicine, called prostaglandins, to keep it open.
Because of the low amount of oxygen given to the body, pulmonary atresia is one of the heart problems that is labeled "blue-baby syndrome." Pulmonary atresia occurs in about one out of every 10,000 live births.
Causes of Pulmonary Atresia
The problem occurs as the heart is forming during the first eight weeks of fetal development.
Some congenital heart defects may have a genetic link. This may be due to a defect in a gene, a chromosome abnormality or environmental exposure. This may cause heart problems to occur more often in certain families. Most of the time, this heart defect occurs by chance with no clear reason for its development.
Signs and Symptoms of Pulmonary Atresia
Cyanosis (blue color) due to low oxygen levels is often present right after birth. Depending on other structural differences in the heart, it could range from mild to severe. The degree of cyanosis is related to the presence of other defects that allow blood to mix. This includes a patent (open) ductus arteriosus as described above. As the ductus closes the cyanosis will increase.
Some babies will have developed extra blood vessels, called collateral vessels, which take blood from an artery to the lungs. Depending on the size and number of these vessels, the baby may not be blue as early. They may not need surgical intervention for a longer period. Eventually, the baby will outgrow the capacity of these vessels to get enough blood to the lungs to maintain safe oxygen levels.
The following are the most common symptoms of pulmonary atresia. Each child may have different symptoms. Symptoms may include:
- cyanosis (blue color around the mouth or of the skin)
- Fast breathing
- Difficulty breathing
- Irritability
- Lethargy (increased sleepiness)
- Pale, cool or clammy skin
The symptoms of pulmonary atresia may look like other medical conditions or heart problems. Always talk to your child's doctor for a diagnosis.
Diagnosis of Pulmonary Atresia
A pediatric cardiologist and / or a neonatologist may be involved in your child's care. A pediatric cardiologist specializes in the diagnosis and medical management of congenital heart defects. They also focus on heart problems that may develop later in childhood. A neonatologist specializes in illnesses affecting newborns, both premature and full-term.
Cyanosis is a major sign that there is a problem with your newborn. Your child's doctor may have also heard a heart murmur during a physical examination. A heart murmur is a noise caused by the turbulence of blood flowing through the openings that allow the blood to mix, or through abnormal valves between the different parts of the heart.
Diagnostic Tests
Other tests are needed to help with the diagnosis. They may include:
- Chest X-ray - a diagnostic test that uses invisible electromagnetic energy beams to create images of internal tissues, bones, and organs onto film.
- Electrocardiogram (ECG or EKG) - a test that records the electrical activity of the heart. It also shows abnormal rhythms (arrhythmias or dysrhythmias), and can see heart muscle stress. This test may look different than normal for a newborn with pulmonary atresia.
- Echocardiogram (echo) - a procedure that looks at the structure and function of the heart by using sound waves recorded and shown on a screen. The sounds waves make a moving picture of the heart and heart valves.
- Cardiac catheterization - an invasive procedure that gives detailed information about the structures inside the heart. Under sedation, a small, thin, flexible tube (catheter) is put into a blood vessel in the groin and guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart and in the pulmonary artery and aorta. Contrast dye is injected to see the heart structures more clearly.
During this testing, one of the important things that will be assessed for is abnormalities of the coronary arteries. Coronary arteries are small blood vessels that supply oxygen- rich blood to the heart muscle. When there is pulmonary atresia with no ventricular septal defect (intact ventricular septum), the right ventricle muscle gets very thick. As the coronary arteries develop, they may form abnormal connections to the thick right ventricle. In some cases, with these abnormal connections to the ventricle, the normal connections of the coronary artery from the aorta are not formed at all or are smaller than normal (coronary artery atresia or stenosis).
The coronary arteries and their connections are best assessed on a cardiac catheterization. If significant coronary artery abnormalities are found, there is a risk of poor blood flow to the heart muscle. This can cause the function of ventricles to decrease significantly. These babies may need to be listed for a heart transplant.
This heart defect may also be diagnosed on fetal echocardiograms. It is one of the cardiac defects that may be found on screening ultrasounds. Early diagnosis of the defect allows for prompt intervention at the time of birth.
Planning to deliver an infant at a hospital capable of newborn resuscitation is important in improving the chances for a good outcome.
Echocardiograms can give detailed information of the anatomy of the various cardiac structures affected in this congenital defect. They also give important information about the function of the heart, the heart valves, the size of the atrial septal defect and the size of the patent ductus arteriosus.
Learn more about our Fetal Heart Program.
Treatment for Pulmonary Atresia
Specific treatment for pulmonary atresia will be determined by your child's doctor based on:
- Your child's age, overall health and medical history
- Extent of the disease
- Your child's tolerance for specific medications, procedures or therapies
- Expectations for the course of the disease
- Your opinion or preference
After birth, it is important to make sure the ductus arteriosus stays open to allow blood to get to the lungs to pick up oxygen. An IV medicine called prostaglandin (PGE-1) is used to keep the ductus arteriosus open. In some babies who have extra blood vessels to the lungs (collaterals), this medicine may not be necessary as these vessels are formed differently than the ductus arteriosus and don’t close right away. However, they may get narrower over time.
Many babies will then undergo a procedure to provide more stable blood flow to the lungs and allow them to grow before they undergo further surgeries. This procedure can be done either with surgery or with a catheter-based procedure. If it is done surgically, a tube or shunt is placed from a body artery to the pulmonary artery. In the catheterization lab, a stent can be placed in the ductus arteriosus to keep it open. Both allow blood to flow from an artery to the lungs where it can pick up oxygen and allows the pulmonary arteries to grow.
Some patients, particularly those who had a pulmonary valve that did not form normally but do not have a lot of muscle under the valve, may be eligible for another procedure. A cardiac catheterization can open the valve to allow blood to flow from the right ventricle to the lungs. A stent may also be placed to keep this area open. This is not safe to perform in patients with abnormal coronary arteries as it will decrease the pressure in the right ventricle and not allow enough blood to flow to the heart muscle.
After this initial procedure, the next steps are determined by the size of the right side of the heart, including the tricuspid valve between the atrium (collecting chamber) and the ventricle, the right ventricle itself, and any other associated abnormalities. If the right side of the heart is too small, the child will need to undergo Single Ventricle palliation and ultimately will have a Fontan circulation.
If the tricuspid valve and right ventricle are normal sized, the child should be able to have surgery to bring blood from the right ventricle to the lungs. This surgery can be with a transannular patch that involves opening the area below the valve in the right ventricle and the pulmonary artery in addition to opening the area of the valve itself. Some patients may need a tube (conduit) placed to form this connection instead. If there is a ventricular septal defect, that can be closed at the time of surgery too. If there are collateral vessels that are the only blood supply to a particular part of the lungs, they may be detached from the artery they came from and brought together with the normal pulmonary arteries.
If the tricuspid valve and right ventricle size is in between (not very small, but not normal sized), then the child may require a combination of the above surgeries so the right ventricle does not have to handle all the blood that would normally go through it to the lungs. They may undergo a procedure called the bidirectional Glenn operation, which connects the superior vena cava (which brings blood back from the top half of the body to the heart) directly to the lungs.
Finally, in some patients with significant coronary abnormalities who do not have good blood supply to their heart muscle, a heart transplant may be required. The low number of newborn organs available for transplantation and the life-long need for anti-rejection therapy can cause concern. Although outcomes for transplantation are improving, and rejection is lowest in patients transplanted as newborns, the average life span of the transplanted heart is less than 20 years.
Adult and Adolescent Management
Adults with pulmonary atresia present may be blue (cyanotic) if they have not be diagnosed in childhood or have not yet had a surgical repair. These patients will have many extra blood vessels (collaterals) that may make their case difficult to treat. All cyanotic patients need careful monitoring and management by congenital heart experts. Some patients who had pulmonary atresia will have had surgical correction of various types and need lifelong monitoring by congenital heart experts.
Depending on their initial surgical pathway, some patients may require a pulmonary valve replacement as an adolescent or young adult. This is needed after the transannular patch surgery because, while it allows blood to flow forward into the lungs, it also allows blood to leak freely back into the right ventricle. Over time, the right ventricle becomes larger and the function can decrease if the valve is not replaced. The patient will be assessed to see if the pulmonary valve replacement needs to be done surgically or if the valve can be placed in the catheterization lab.
If patients underwent repair with a tube (conduit), this will not grow with them and larger conduits will need to be replaced as they get bigger. They may also get procedures in the catheterization lab to stretch out the conduit if possible, open it up if it becomes narrow, or have a valve placed.
For patients needing single ventricle surgeries, outcomes after Fontan are generally good with the oldest patients who have undergone these surgeries, now in their 30-40s. They may eventually need heart transplantation depending on the functioning of the left ventricle and the left sided (mitral) valve, or complications that can be seen after the Fontan surgery.
Learn more about the Adolescent and Adult Congenital Heart Disease Program.
