What is Pulmonary Atresia (PA)?
Pulmonary atresia (PA) is a complicated congenital (present at birth) 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 has three leaflets that function like a one-way door. This allows oxygen-depleted blood 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. That means blood cannot flow forward from the right ventricle to the lungs. Before birth, while the fetus is developing, this is not a threat to life. 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 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. This allows blood in the right ventricle a way out. This opening is called a ventricular septal defect (VSD). If there is no VSD, the right ventricle gets little blood flow before birth. It does not develop fully.
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 must find 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. Newborns also have a connection between the aorta and the pulmonary artery. This is called the ductus arteriosus. It allows some of the oxygen-poor (blue) blood to pass into the lungs. Unfortunately, this ductus arteriosus normally closes within a few hours or days after birth if the child is not treated with life-saving medicine.
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) is often present to some degree immediately 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 that is used to bypass the lungs during fetal life. This ductus arteriosus begins closing shortly after birth. Closure is started by the introduction of oxygen into the blood once the baby starts breathing on their own. Closure of this ductus starts within hours of being born. It can take a few days to weeks. 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 of these vessels, the baby may not be blue as early. They may not need a surgical intervention for a longer period. Eventually, the baby will outgrow the capacity of these vessels to get enough blood to the lungs for oxygenation.
The following are the most common symptoms of pulmonary atresia. Each child may have different symptoms. Symptoms may include:
- Fast breathing
- Difficulty breathing
- Lethargy (increased sleepiness)
- Pale, cool or clammy skin
- Cyanosis (blue color around the mouth or of the 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.
Other tests are needed to help with the diagnosis. They may include:
- Chest X-ray - a diagnostic test which 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.
- 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. Measurements are also taken in the pulmonary artery and aorta. Contrast dye is injected to see the heart structures more clearly.
This heart defect is often found before birth, during an ultrasound. Your obstetrician will refer you to a specialist who will do a fetal echocardiogram. This can give you a chance to learn about this defect. It also helps your doctors prepare for the birth of your baby. When this diagnosis is known before birth, the baby can be stabilized with a medicine that can keep the fetal connections open until the baby is examined. An echocardiogram will be done with the exam to decide if the baby will need surgery in the newborn period.
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
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. 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. All these need lifelong monitoring by congenital heart experts.