pulmonary atresia
Summary
Pulmonary atresia is a cyanotic congenital heart defect in which there is complete obstruction of the right ventricular outflow tract, with no communication between the right ventricle and pulmonary artery. Pulmonary blood flow is entirely dependent on a patent ductus arteriosus (PDA) or, in some cases, aortopulmonary collaterals. It presents in the neonatal period with severe cyanosis and requires urgent PGE1 infusion to maintain ductal patency.
Detail
Pulmonary atresia occurs when the pulmonary valve fails to develop properly, resulting in a complete membranous or muscular obstruction of the RV outflow tract. It exists in two major forms: pulmonary atresia with intact ventricular septum (PA-IVS), where the RV is often hypoplastic and there may be RV-dependent coronary circulation, and pulmonary atresia with ventricular septal defect (PA-VSD), which is essentially an extreme form of Tetralogy of Fallot where pulmonary blood flow depends on a PDA or major aortopulmonary collateral arteries (MAPCAs).
Pathophysiology: Since blood cannot flow from the RV to the pulmonary artery, systemic venous blood shunts right-to-left across a patent foramen ovale or ASD into the left heart, and pulmonary blood flow occurs via the ductus arteriosus (ductal-dependent circulation) or collaterals. Closure of the PDA after birth causes severe hypoxemia and can be fatal without intervention.
Clinical presentation: Neonates present within hours to days of birth with severe cyanosis, tachypnea, and a single S2 (absent pulmonic component). A continuous murmur may be heard from PDA flow. Echocardiography confirms diagnosis by showing atretic pulmonary valve/RVOT, VSD (if present), RV size, and ductal-dependent flow.
Management: Immediate prostaglandin E1 (alprostadil) infusion to maintain ductal patency until surgical intervention. Depending on anatomy (RV size, presence of VSD), surgical options include: balloon or surgical valvotomy, RV-to-PA shunt (Blalock-Taussig shunt or similar), or staged single-ventricle palliation (Norwood → Glenn → Fontan) if RV is severely hypoplastic. PA-IVS often requires assessment for RV-dependent coronary circulation, which affects surgical planning (biventricular vs. univentricular repair).
Associations: Pulmonary atresia is associated with genetic syndromes (e.g., 22q11 deletion in some forms), and RV-dependent coronary circulation is a critical consideration in PA-IVS due to risk of myocardial ischemia if RV decompression is performed without addressing coronary anomalies.
High-yield boards points: Remember pulmonary atresia as a ductal-dependent cyanotic lesion requiring PGE1; distinguish from Tetralogy of Fallot (which has some antegrade flow) and tricuspid atresia (different anatomic defect). Test question stems often describe a cyanotic newborn who worsens when the ductus closes (e.g., after indomethacin or spontaneous closure) — the answer is PGE1, not closing the duct.
Sources
- Kaplan USMLE Step 1 Lecture Notes - Cardiovascular System
- First Aid for the USMLE Step 1
- Nelson Textbook of Pediatrics, Congenital Heart Disease chapter
- UpToDate: Pulmonary atresia with intact ventricular septum
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.