Pulmonary Atresia is a severe congenital heart defect (CHD) where the pulmonary valve, which controls blood flow from the heart to the lungs, is underdeveloped or completely closed. This condition is present at birth. The absence of a functional pulmonary valve means that blood cannot flow from the heart’s right pumping chamber, the right ventricle, into the pulmonary artery to reach the lungs for oxygenation. This structural abnormality redirects deoxygenated blood through alternate pathways, leading to a profound lack of oxygen in the body’s circulation.
Understanding the Core Defect
The right ventricle normally propels oxygen-poor blood through the pulmonary valve to the lungs. In Pulmonary Atresia, this path is blocked, preventing the right ventricle from performing its function. Blood must bypass this obstruction to reach the lungs.
To survive, newborns rely on two temporary openings from fetal circulation: the patent foramen ovale (PFO) and the ductus arteriosus. The PFO is an opening between the heart’s upper chambers (atria) that shunts blood from the right side to the left side. The ductus arteriosus is a blood vessel connecting the aorta to the pulmonary artery, providing the only route for blood to reach the lungs.
The condition is categorized into two main types based on the ventricular septum (the wall separating the lower chambers). Pulmonary Atresia with an intact ventricular septum (PA/IVS) means there is no hole between the ventricles, often resulting in a small and underdeveloped right ventricle. Pulmonary Atresia with a ventricular septal defect (PA/VSD) includes a hole between the ventricles, which allows blood flow to and from the right ventricle, often resulting in a more normally sized chamber.
Detecting Pulmonary Atresia
The condition may be identified before birth during routine prenatal screening. If an issue is suspected, a fetal echocardiogram—a specialized ultrasound of the baby’s heart—can confirm the diagnosis by detailing the structure and function of the heart. Prenatal detection allows for planning delivery and immediate medical management at a specialized center.
Postnatally, symptoms often appear within the first hours or days of life, typically as the ductus arteriosus begins closing. The most recognizable sign is cyanosis, a bluish tint to the skin, lips, and nails, caused by low oxygen levels. Other symptoms include rapid or difficult breathing, extreme sleepiness, and poor feeding.
Physicians use several diagnostic tools to confirm the condition after birth. Pulse oximetry, a painless test measuring blood oxygen saturation, will show low levels. An echocardiogram uses sound waves to create a moving picture of the heart, clearly showing the blocked pulmonary valve and blood flow. Further tests, such as a chest X-ray and an electrocardiogram (EKG), provide information on the heart’s size and electrical activity, revealing signs of muscle stress.
Causes and Risk Factors
The precise cause of Pulmonary Atresia remains largely unknown in most cases, suggesting it results from a combination of factors. The defect occurs during the first eight weeks of pregnancy when the fetal heart is developing its structure. This is when the pulmonary valve fails to form properly, leading to the complete obstruction.
Genetic factors play a role, as a family history of congenital heart irregularities increases the risk. Children with chromosomal defects or specific genetic syndromes, such as DiGeorge syndrome, also have an elevated risk. Maternal factors during pregnancy are recognized as contributing risk factors. These include unmanaged maternal diabetes, obesity, and the use of certain teratogenic medications. Exposure to environmental factors, such as maternal alcohol or tobacco use during pregnancy, may also increase the likelihood of the defect developing.
Surgical and Medical Management
Immediate medical intervention is necessary for newborns with Pulmonary Atresia to ensure blood flow to the lungs. The first step is an intravenous infusion of Prostaglandin E (PGE). This drug temporarily prevents the ductus arteriosus from closing, maintaining the connection between the aorta and pulmonary artery, which is the only way for blood to reach the lungs.
Long-term management involves a staged surgical approach, often beginning within the first days or weeks of life. Initial palliative procedures establish a reliable source of blood flow to the lungs. A common procedure is the placement of a systemic-to-pulmonary artery shunt, such as a Blalock-Taussig shunt, which connects a body artery to the pulmonary artery.
Initial Palliative Procedures
In some cases, a catheter-based intervention may be performed. This involves placing a stent to keep the ductus arteriosus open, or widening the blocked pulmonary valve with a balloon.
Definitive Repair
The goal is definitive repair, which depends heavily on the size and development of the right ventricle. If the right ventricle is large enough, a complete two-ventricle repair may be possible, involving valve replacement and closure of associated defects.
If the right ventricle is too small to function as a primary pump, patients require a series of procedures culminating in the Fontan procedure. The Fontan operation is a palliative solution that redirects all deoxygenated blood flow directly to the pulmonary artery, bypassing the right ventricle entirely. This leaves the left ventricle to manage both body and lung circulation.
Long-Term Outlook
The prognosis for individuals born with Pulmonary Atresia has significantly improved due to advancements in surgical and medical care. Survival rates into early adulthood are high for patients who successfully complete their intended treatment path, whether it is a two-ventricle repair or the Fontan pathway. For those discharged alive after definitive repair, 20-year survival rates can reach over 90%.
The condition necessitates lifelong, specialized follow-up care with a cardiologist experienced in adult congenital heart disease (ACHD). Patients who undergo the Fontan procedure may face long-term complications related to the altered circulation.
Potential Long-Term Complications
These complications include:
- Abnormal heart rhythms (arrhythmias)
- Liver dysfunction
- Heart failure
- Increased risk of endocarditis (infection of the heart lining)
Regular check-ups are required to monitor heart function, manage chronic conditions, and assess the need for potential future interventions.