Pulmonary Atresia

Complete obstruction of right ventricular outflow with no flow from the right ventricle to the pulmonary arteries. About 7 to 8 per 100,000 live births in total, comprising two forms:

• Pulmonary atresia with intact ventricular septum: atretic pulmonary valve, hypoplastic or normal right ventricle, small tricuspid valve, possible right ventricle to coronary artery sinusoids. Lungs depend on the ductus arteriosus.
• Pulmonary atresia with ventricular septal defect: an extreme form of tetralogy of Fallot, with a variable pulmonary artery supply from the ductus or from major aortopulmonary collateral arteries.

• Mechanism: blood reaches the lungs only through the ductus or collateral vessels; right to left shunt at atrial or ventricular level causes cyanosis, which worsens as the ductus closes.
• Untreated, nearly all neonates die within days to weeks of ductal closure.

• Cyanosis within the first hours to days, unresponsive to oxygen, with tachypnoea but little respiratory distress initially.
• Single loud second heart sound; no murmur, or a continuous murmur from the ductus or collaterals; tricuspid regurgitation murmur in intact septum type.
• Deterioration at ductal closure: profound cyanosis, acidosis, collapse.
• With a large collateral supply, heart failure may appear later.
• Differential diagnosis: critical pulmonary stenosis, tricuspid atresia, transposition of the great arteries, Ebstein anomaly, severe tetralogy of Fallot, persistent pulmonary hypertension of the newborn, neonatal sepsis.
• Complications: shunt thrombosis, pulmonary artery distortion, conduit stenosis, endocarditis, ventricular dysfunction, arrhythmia, haemoptysis from collaterals.

• Hyperoxia test: PaO2 remains less than 150 mmHg (and SpO2 does not rise to more than about 90%) on 100% oxygen for 10 minutes, supporting a cyanotic cardiac cause.
• Arterial blood gas: hypoxaemia, metabolic acidosis with ductal closure.
• ECG: left axis deviation, little right ventricular force with hypoplastic ventricle. Chest X-ray: oligaemic lungs, normal or enlarged heart.
• Echocardiography: valve plate atresia, right ventricular size, tricuspid valve z-score (a z-score of less than minus 2.5 predicts poor right ventricular growth), right ventricular infundibulum, ductus, confluence and size of branch pulmonary arteries, ventricular septal defect, aortic arch sidedness.
• Cardiac catheterisation or CT angiography: coronary anatomy (right ventricle dependent coronary circulation with sinusoids and proximal coronary stenosis), collateral arteries.

• Keep the ductus open: alprostadil (prostaglandin E1) 0.05 to 0.1 micrograms/kg/min IV until the ductus reopens, then reduce to the lowest effective dose, 0.01 to 0.05 micrograms/kg/min. Be ready to ventilate because apnoea occurs in about 10 to 12%, particularly in babies under 2 kg.
• Target SpO2 75 to 85%. Avoid high oxygen concentrations (oxygen promotes ductal closure and pulmonary vasodilatation does not help because there is no forward flow). Correct acidosis, maintain temperature, glucose and haemoglobin of 130 g/L or more (13 g/dL), avoid dehydration.
• Intact septum, adequate right ventricle (tricuspid z-score greater than minus 2.5, tripartite ventricle): catheter radiofrequency or laser perforation of the valve followed by balloon valvuloplasty, with ductal stenting or a shunt if saturation stays at less than 75% to 80%. Surgical valvotomy or transannular patch is an alternative.
• Hypoplastic right ventricle: modified Blalock-Taussig shunt (3 to 3.5 mm tube for under 3 kg, 4 mm after) or ductal stent, then staged single ventricle palliation (bidirectional Glenn shunt at 3 to 6 months, Fontan completion at 2 to 4 years) or a one-and-a-half ventricle repair.
• Right ventricle dependent coronary circulation: right ventricular decompression is contraindicated because it causes coronary ischaemia. Proceed to a shunt and single ventricle pathway, or transplant for severe coronary disease.
• Perioperative anticoagulation for a shunt: unfractionated heparin 50 to 100 units/kg IV at placement; aspirin 3 to 5 mg/kg/day afterwards (shunt thrombosis rate about 5 to 10%).
• Pulmonary atresia with ventricular septal defect: shunt or primary repair depending on pulmonary artery size. Complete repair by closing the ventricular septal defect and placing a conduit from the right ventricle to the pulmonary artery, with unifocalisation of collaterals when pulmonary arteries are small. Conduit replacement is needed every 5 to 15 years.
• Medical support after palliation: furosemide 1 mg/kg per dose 1 to 2 times daily for oedema, aspirin 3 to 5 mg/kg/day, iron supplementation (3 to 6 mg/kg/day of elemental iron) if iron deficient.
• Endocarditis prophylaxis after palliation or repair with prosthetic material: amoxicillin 50 mg/kg (maximum 2 g) orally 30 to 60 minutes before dental procedures.
• Survival: intact septum about 70 to 85% at 5 years in modern series; ventricular septal defect form about 75 to 90% at 10 years, lower with severe collateral disease.
• Special groups: pregnancy (high risk after single ventricle palliation or with residual obstruction; preconception assessment essential); older children and adults (arrhythmia surveillance, conduit assessment, hepatic and renal monitoring after Fontan).
• Red flags: SpO2 less than 70%, sudden fall in saturation after a shunt (thrombosis), fever, new arrhythmia.
• Follow up: neonatal intensive care, then weekly weight and saturation checks after discharge; echocardiography every 3 to 6 months in infancy, yearly in childhood; lifelong specialist congenital heart disease follow up.