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Pulmonary Atresia with Intact Ventricular Septum (PA-IVS)

Pulmonary atresia with an intact ventricular septum is a rare congenital heart defect characterized by the complete obliteration of the pulmonary valve, preventing normal blood flow from the right ventricle to the pulmonary artery. Unlike pulmonary atresia with a ventricular septal defect, in this condition, the ventricular septum is intact, preventing any direct communication between the two ventricles.
The pulmonary blood flow is therefore maintained exclusively through collateral circulations, such as the patent ductus arteriosus or systemic-to-pulmonary arterial collaterals.
The absence of a normal right ventricular outflow leads to secondary alterations in right ventricular development and pulmonary circulation, making this condition one of the critical congenital heart defects in neonates.

Epidemiology

Pulmonary atresia with an intact ventricular septum has an estimated incidence of about 4-5 cases per 100,000 live births, accounting for approximately 1-3% of all congenital heart defects. There is no significant sex predilection. However, it is frequently associated with coronary anomalies, such as coronary artery fistulae connecting to the right ventricle or coronary circulation dependent on a hypoplastic right ventricle, which influence prognosis and treatment.

Pathophysiology

Atresia of the pulmonary valve prevents blood from flowing normally from the right ventricle to the pulmonary artery, leading to pulmonary blood flow that depends on extracardiac shunts. Since the ventricular septum is intact, the right ventricle has no outlet for blood due to the completely closed pulmonary valve. This condition causes increased pressure inside the right ventricle, which initially may lead to hypertrophy (thickening of the ventricular walls). However, in more severe cases, the reduced blood flow through the right ventricle compromises its development, leading to progressive hypoplasia (reduction in size and function) of the ventricle itself and the tricuspid valve.
The main pathophysiological consequences include:

Clinical Manifestations

The clinical presentation of pulmonary atresia with an intact ventricular septum is variable. The primary symptom is severe and progressive central cyanosis, which worsens significantly as the ductus arteriosus begins to close.
It is usually accompanied by tachypnea and respiratory distress, due to hypoxemia. On physical examination, a heart murmur may be auscultated, usually related to tricuspid regurgitation or abnormal pulmonary blood flow. Signs of right heart failure may also be present in cases where the right ventricle is hypertrophic but dysfunctional.
In the most severe cases, closure of the ductus arteriosus without therapeutic intervention rapidly leads to cardiac decompensation and hypoxic shock.

Diagnosis

Diagnosis is based on a combination of clinical and imaging studies. Fetal echocardiography, performed between the 18th and 22nd weeks of gestation, can identify pulmonary atresia through the absence of flow across the pulmonary valve and the presence of a hypoplastic right ventricle.
After birth, diagnostic suspicion arises in the presence of severe cyanosis and respiratory distress. Transthoracic Doppler echocardiography allows visualization of the absence of pulmonary blood flow, right ventricular anatomy, and the presence of coronary anomalies. Cardiac magnetic resonance imaging (CMR) is useful in complex cases to assess the morphology of the right ventricle and pulmonary arteries, while cardiac catheterization is necessary for surgical candidates to evaluate coronary circulation and pulmonary vascular resistance.

Treatment

Treatment of pulmonary atresia with an intact ventricular septum depends on right ventricular morphology and associated coronary circulation. The primary goal is to ensure adequate pulmonary blood flow and prevent severe hypoxia. Infusion of prostaglandin E1 (PGE1) is essential to keep the ductus arteriosus open and ensure adequate pulmonary blood flow while awaiting surgery.
In neonates with respiratory compromise or metabolic acidosis, ventilatory support and careful acid-base balance management may be required to stabilize hemodynamic conditions. Surgical strategies:

Prognosis

Prognosis depends on multiple factors, including right ventricular size, adequacy of coronary flow, and timeliness of treatment.
In patients with favorable ventricular morphology, biventricular repair offers an acceptable quality of life. In more complex cases, long-term outcomes depend on the effectiveness of palliation and the risk of late complications.
    References
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