Pulmonary Atresia is a severe congenital heart defect present at birth, characterized by the complete absence or blockage of the pulmonary valve. This valve normally acts as a one-way door, regulating blood flow from the heart’s lower right chamber, the right ventricle, into the pulmonary artery which leads to the lungs. When this pathway is obstructed, the heart cannot send deoxygenated blood to the lungs to pick up oxygen, creating an immediate, life-threatening crisis for the newborn. This structural anomaly means that a baby’s circulation must rely entirely on temporary fetal pathways until surgical intervention can be performed.
Defining Pulmonary Atresia and Its Impact on Blood Flow
In a healthy heart, deoxygenated blood returns from the body to the right side and is pumped to the lungs for oxygenation. With pulmonary atresia, the blocked valve causes blood to back up in the right ventricle and atrium. This pressure forces the blood to seek alternate routes through structures that should have closed shortly after birth, resulting in ductal-dependent circulation.
The primary temporary pathway is the patent ductus arteriosus (PDA), a small blood vessel connecting the pulmonary artery to the aorta. Since blood cannot exit the right ventricle, the only way for blood to reach the lungs is by flowing backward through the PDA from the high-pressure aorta. This mechanism supplies the lungs with a limited amount of mixed blood.
Another circulatory adjustment involves the atria, the heart’s two upper chambers. An opening, such as the foramen ovale or an atrial septal defect, allows deoxygenated blood to bypass the right side of the heart entirely. This blood flows from the right atrium directly into the left atrium, where it mixes with oxygenated blood returning from the lungs.
The mixed blood is then pumped by the left ventricle to the rest of the body, resulting in low systemic oxygen levels. This causes the baby to appear cyanotic, or blue, because the distributed blood lacks sufficient oxygen. Reliance on the PDA makes this defect an urgent concern, as this vessel naturally begins to close shortly after birth.
The Two Primary Forms of Pulmonary Atresia
Pulmonary atresia is classified into two main types, which influence the required surgical strategy. The distinction lies in the condition of the ventricular septum, the wall separating the heart’s two lower chambers. These two forms are pulmonary atresia with an intact ventricular septum (PA-IVS) and pulmonary atresia with a ventricular septal defect (PA-VSD).
In PA-IVS, the wall between the right and left ventricles is complete. Because the pulmonary valve is blocked, the right ventricle receives very little blood flow during fetal development and cannot decompress. This often leads to the right ventricle being small and underdeveloped. The size of this underdeveloped right ventricle is the central factor in determining treatment.
Conversely, PA-VSD includes a large hole in the wall separating the two ventricles. This defect acts as a pressure relief valve, allowing blood to flow freely between the right and left ventricles. This decompression results in a right ventricle that is more normally sized and developed. This form is sometimes considered a severe variant of Tetralogy of Fallot.
Identifying Pulmonary Atresia and Initial Urgent Care
Pulmonary atresia can sometimes be detected before birth using a fetal echocardiogram. More commonly, the condition is identified shortly after birth when the newborn exhibits severe cyanosis, a bluish tint to the skin and lips, reflecting low blood oxygen saturation. Newborn screening using pulse oximetry can also flag the condition if saturation levels are low.
Once the diagnosis is confirmed by an echocardiogram, immediate intervention is necessary to stabilize the baby. The primary goal is to keep the patent ductus arteriosus (PDA) open, as it is the sole source of blood flow to the lungs. This is achieved through the continuous intravenous administration of Prostaglandin E1 (PGE1).
PGE1 works by relaxing the smooth muscle tissue of the ductus arteriosus, preventing its natural closure and maintaining the temporary channel to the lungs. This intervention allows time to stabilize the infant and plan for definitive surgical procedures. The baby is then closely monitored until surgical repair can be scheduled.
Treatment Pathways and Long-Term Management
The treatment for pulmonary atresia is complex and involves a staged surgical approach tailored to the specific anatomy, especially the size of the right ventricle. The initial palliative goal is to establish a reliable source of blood flow to the lungs to improve oxygen saturation. This is often accomplished by placing a systemic-to-pulmonary artery shunt, a small tube connecting an artery from the body to the pulmonary artery.
For patients with PA-VSD and a well-developed right ventricle, the goal is a full two-ventricle repair, typically performed later in infancy. This involves closing the ventricular septal defect and surgically connecting the right ventricle to the pulmonary artery using a valved conduit. This repair establishes a normal blood flow pattern, allowing the right ventricle to pump deoxygenated blood directly to the lungs.
If the right ventricle is too small (common in PA-IVS), the patient is placed on a single-ventricle repair pathway, culminating in a series of two or three operations. The second stage is usually the Glenn procedure, which diverts blood from the upper body directly into the pulmonary artery, bypassing the right ventricle entirely. The final stage is the Fontan procedure, which reroutes blood from the lower body to the pulmonary artery, establishing a passive flow of all deoxygenated blood to the lungs.
Individuals who have undergone repair require lifelong, specialized cardiac care from cardiologists trained in congenital heart disease. Patients on the two-ventricle path often need subsequent procedures to replace the valved conduit as they grow or as it wears out. Ongoing monitoring is necessary to manage potential complications like heart rhythm issues, heart failure, or the need for additional valve interventions.