Pulmonary atresia-intact ventricular septum syndrome

Pulmonary atresia with intact ventricular septum (PA-IVS) is a rare congenital heart defect present at birth in which the pulmonary valve fails to form properly, resulting in complete obstruction of blood flow from the right ventricle to the pulmonary artery. Unlike pulmonary atresia with a ventricular septal defect, the ventricular septum remains intact, meaning there is no hole between the two lower chambers of the heart. This condition critically impairs the heart's ability to send blood to the lungs for oxygenation. Survival after birth depends on the persistence of fetal circulatory pathways, particularly the patent ductus arteriosus (PDA), which allows some blood to reach the lungs. Without intervention, closure of the PDA leads to severe cyanosis (bluish discoloration of the skin due to low oxygen levels) and is life-threatening. The right ventricle in PA-IVS is often underdeveloped (hypoplastic), though its size can vary considerably among affected individuals. In some cases, abnormal connections between the right ventricle and the coronary arteries (sinusoidal communications or coronary fistulae) develop, which can make the coronary circulation dependent on the right ventricle — a feature known as right ventricle-dependent coronary circulation (RVDCC). This is a critical consideration in treatment planning because decompressing the right ventricle in such cases could compromise coronary blood flow and lead to myocardial ischemia. Other associated findings may include tricuspid valve abnormalities, right atrial enlargement, and an atrial septal defect or patent foramen ovale that allows right-to-left shunting. Immediate treatment after birth typically involves administration of prostaglandin E1 to maintain ductal patency, followed by surgical or catheter-based interventions. Treatment strategies depend on the anatomy and include radiofrequency perforation or surgical valvotomy of the pulmonary valve, creation of a systemic-to-pulmonary artery shunt (such as a modified Blalock-Taussig shunt), or staged single-ventricle palliation culminating in a Fontan procedure for patients with severely hypoplastic right ventricles. Some patients with adequate right ventricular size may ultimately achieve a biventricular repair. Long-term outcomes have improved significantly with advances in neonatal cardiac surgery and interventional cardiology, though lifelong cardiac follow-up is required.

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