Pulmonary Atresia Intact Ventricular Septum

Pulmonary atresia with intact ventricular septum (PAIVS) is a complex congenital heart defect characterized by pulmonary valvular atresia. As such, the colour box presented below does not show any passage of blood flow through the valve. The disease is PGE dependent - ductal dependent - to allow adequate pulmonary circulation. Patients may have various presentations, with myocardial sinusoids complicating the course of their management. More on PAIVS here.

Pulmonary Atresia with Intact Ventricular Septum (PA/IVS) is a rare and complex congenital heart defect characterized by a complete blockage (atresia) of the pulmonary valve, preventing blood flow from the right ventricle (RV) to the pulmonary artery. A key defining feature is the presence of an intact ventricular septum, meaning there is no direct communication between the right and left ventricles. This condition represents a wide spectrum of anatomical variations, particularly concerning the size and structure of the right-sided heart chambers and the pulmonary artery. In this condition, there is ductal dependent pulmonary circulation. As such, these infants need urgent exposure to prostaglandin to maintain ductal patency and pulmonary blood flow. They will be cyanotic, considering that the right to left shunt is obligatory at the atrial level, introducing deoxygenated blood in the systemic circulation. Saturation to be aimed are >80%, outlining that there is adequate pulmonary blood flow and oxygenated blood coming back to the left atrium and mixing with the right to left shunt via the inter-atrial communication. This condition is of particular interest, considering that there is a risk in a subcategory of infants with PAIVS of persistent sinusoids, possibly stealing from the coronary circulation. Indeed, depending on the tricuspid valve competency, the intra-RV pressure may be extremely high during the early fetal life. Because of this, these remnant embryological channels (sinusoids) may stay patent and connect the RV cavity to the coronary system. This may lead to severe coronary steal upon decompression of the RV - or changes in the hemodynamics. As such, these patients are at risk of severe myocardial ischemia. These infants often undergo cath lab evaluation before surgery in order to delineate if there is indeed sinusoids connecting to the coronary circulation, and before attempting an intervention. Depending on the RV size, the RVOT configuration and the presence or absence of sinusoids, these patients will have different approaches for their interventions. They may require single ventricular repair because of the above considerations.

Anatomy and Morphology

The anatomical features of PA/IVS are highly variable and significantly influence the clinical presentation and management. Key structures evaluated include:

• Pulmonary Valve Atresia Type: The blockage of the pulmonary valve can be either membranous (an imperforate valve with formed cusps fused together) or muscular (a long segment of muscle blocking the RV outflow tract). Membranous atresia is generally associated with a better long-term prognosis compared to muscular atresia. When membranous, these infants may be eligible for cath-based interventions to re-open the RV outflow tract.

• Right Ventricle (RV) Size and Morphology: The RV can range from near-normal size to being severely underdeveloped (diminutive). Its morphology is often described by the presence and development of its three components: the inflow, apical trabecular, and outlet regions. A tripartite RV has all three components well-formed, a bipartite RV is moderately hypoplastic with an attenuated apical component, and a unipartite RV is severely hypoplastic, consisting mainly of the inflow portion. The size and morphology of the RV are crucial in determining the potential for different repair strategies.

  • In a subset of patients with PA/IVS, the right ventricle (RV) appears enlarged rather than hypoplastic, occurring in approximately 5–10% of cases. This dilation may vary in severity, sometimes leading to striking cardiac enlargement. These patients often exhibit significant tricuspid regurgitation, resulting in marked right atrial enlargement and, at times, dilation of the systemic venous return. The foramen ovale may be stretched open due to elevated right-sided pressures, facilitating right-to-left shunting at the atrial level. The tricuspid valve annulus and RV cavity in these cases tend to be oversized, occasionally to the point where the right heart compresses the left-sided structures, impairing systemic output. On imaging, the heart may appear massively enlarged, mimicking the radiographic features of severe Ebstein anomaly. While some patients may indeed have coexisting Ebstein anomaly, others show a structurally normal tricuspid hinge point with dysplastic, sail-like leaflets. The RV in this context is usually thin-walled and lacks hypertrophy, and fibroelastosis is rare. Systolic decompression of the RV through tricuspid regurgitation results in relatively low intraventricular pressures, making coronary anomalies less common. The pulmonary valve annulus and pulmonary arteries are typically of normal caliber or only mildly small, with no significant abnormalities in the pulmonary arterial tree. Managing PA/IVS patients with significant right ventricular (RV) dilation is complex, as they face higher risks of fetal loss, neonatal complications, and surgical mortality. Some have been successfully managed with biventricular repair strategies, such as tricuspid valvuloplasty combined with patching the right ventricular outflow tract (RVOT), occasionally alongside surgical reduction of the dilated RV or right atrium. In select cases, a pulmonary valvotomy or RVOT patch alone may suffice. However, others may require single-ventricle palliation. In cases of severe tricuspid regurgitation, a Starnes procedure may be indicated. This involves excluding the RV from circulation by placing a fenestrated patch over the tricuspid valve, along with a systemic-to-pulmonary shunt (in Ebstein - the Starnes procedure also includes ligating the pulmonary artery). 

• Tricuspid Valve (TV) Size and Morphology: The tricuspid valve, which controls blood flow from the right atrium to the RV, also shows variable anatomy, from normal size to severe hypoplasia. It may also be dysplastic or have malformed chordal attachments, sometimes presenting an "Ebstinaoid"-type of malformation. The size of the tricuspid valve annulus, often expressed as a z-score, is a component to evaluate when assessing for potential biventricular repair. Tricuspid regurgitation can also be present and be significant.

• Pulmonary Arteries: In most cases of PA/IVS, the main pulmonary artery (MPA) and its branches (left and right pulmonary arteries) are well-formed, or only mildly hypoplastic. Indeed, they were fed in-utero by the ductus arteriosus which is left to right (aortic to pulmonary), contrary to the usually patern of right to left (pulmonary artery to aorta). Indeed, pulmonary blood flow is typically supplied by the patent ductus arteriosus (PDA). Major aortopulmonary collateral arteries (MAPCAs) are rare in PA/IVS, but can occur.

• Atrial Septum: An opening in the atrial septum, such as a patent foramen ovale (PFO) or an atrial septal defect (ASD), is essential for survival. This allows oxygen-poor blood from the right atrium to shunt to the left atrium, mixing with oxygenated blood returning from the lungs, enabling systemic circulation. Although rare, patients with a restrictive foramen ovale may require a septostomy in the post-natal context. However, because the entire systemic venous return and placental flow typically returns to the right atrium and is obliged to pass towards the left atrium, this communication remaind large in most fetuses by the significant flow that is present during fetal life through the FO. 

• Coronary Artery Anomalies: A critical feature that can significantly impact outcomes is the presence of abnormal connections between the RV cavity and the coronary arteries, known as ventriculocoronary connections (VCACs) or sinusoids. In some cases, the coronary circulation becomes dependent on pressure from the RV to perfuse the myocardium, termed Right Ventricle Dependent Coronary Circulation (RVDCC). This can occur if there are stenoses (narrowings) or atresia (blockages) in the coronary arteries near their origin from the aorta. RVDCC is a significant risk factor and can preclude standard biventricular repair.

  • Potential for circular shunt: If blood flows from the aorta into the coronary arteries, then retrograde into the RV through these sinusoids, and from there back into the right atrium via tricuspid regurgitation, you get a "circular shunt" — a loop of blood circulating on the right side of the heart that bypasses the systemic and pulmonary circulation entirely, offering no effective perfusion to the body. This situation is hemodynamically dangerous because it recirculates blood without delivering oxygen to the tissues, and may lead to myocardial ischemia if the coronary perfusion becomes dependent on RV pressures. It is one of the reasons RV-dependent coronary circulation is considered a contraindication to biventricular repair in PA/IVS.

Clinical Presentation

Newborns with PA/IVS are typically cyanotic (bluish skin colour) because of the mixing of oxygenated and deoxygenated blood and reduced pulmonary blood flow. Cyanosis often becomes more prominent as the PDA, which provides the primary source of pulmonary blood flow, begins to narrow after birth. The severity of cyanosis depends on the amount of blood flowing to the lungs via the PDA and the degree of mixing at the atrial level. If the atrial communication is restrictive, it can limit systemic cardiac output, potentially leading to signs of low cardiac output. Physical examination may reveal a single second heart sound (due to pulmonary atresia) and potentially a murmur from a patent ductus arteriosus or tricuspid regurgitation.

Diagnosis

Diagnosis is primarily made using echocardiography, often prenatally. Echocardiography allows visualization of the pulmonary valve atresia, assessment of RV and TV size and morphology, evaluation of pulmonary artery size, identification of the atrial septal communication and PDA, and initial assessment for the presence of ventriculocoronary connections. However, echocardiography is often insufficient to fully delineate the complex coronary artery anatomy and confirm RVDCC. Therefore, cardiac catheterization with angiography is often required, especially to evaluate the coronary circulation and assess the severity of any coronary stenosis or atresia. Cardiac catheterization can also be used to assess pulmonary vascular resistance, particularly before later stages of palliation or in older patients. Chest CT or MRI may be used if needed, but echocardiography is the mainstay.

Management Strategies

Management of PA/IVS is complex and highly individualized based on the specific anatomy, particularly RV and TV size, and the presence or absence of RVDCC.

• Initial Stabilization: Maintaining the patency of the ductus arteriosus with a prostaglandin E1 (PGE1) infusion is essential immediately after diagnosis to ensure adequate pulmonary blood flow. If the atrial communication is severely restrictive, balloon atrial septostomy may be necessary to improve mixing and systemic oxygenation.

• Definitive Treatment Approaches: The long-term strategy is determined by the potential for the RV to support the pulmonary circulation.

  • Biventricular (BiV) Repair: This is the goal for patients with adequately sized RV and TV, and no significant RVDCC. The primary intervention aims to create an opening between the RV and the pulmonary artery to restore antegrade pulmonary blood flow. This can be achieved through percutaneous catheter-based radiofrequency perforation and balloon dilation of the pulmonary valve or surgical valvotomy. Supplemental pulmonary blood flow may still be needed, often provided by PDA stenting or a surgical systemic-to-pulmonary artery shunt (e.g., Blalock-Taussig-Thomas shunt). The atrial septal defect is typically left open initially to allow the RV to remodel and is later closed if it doesn't close spontaneously. The muscular type may need a RV-PA conduit as they are not eligible for valvular opening (there is no valve). 

  • One-and-a-Half Ventricle (1.5V) Repair: This approach may be considered for patients with borderline RV and/or TV size. It involves using the RV to pump some blood to the lungs (usually through an RV-PA connection or shunt) and diverting systemic venous return from the upper body directly to the pulmonary artery via a bidirectional cavopulmonary shunt (BCPS).

  • Single Ventricle (1V) Palliation: This pathway is chosen when the RV is too small or there is significant RVDCC that prevents biventricular repair. Initial intervention focuses on securing a reliable source of pulmonary blood flow, often with a PDA stent or BTT shunt. This is followed by staged procedures, including the BCPS and ultimately the Fontan operation, to redirect all systemic venous blood passively to the lungs.

  • Primary Cardiac Transplantation: This may be the preferred option for patients with severe RVDCC, which carries a high risk of myocardial ischemia and mortality. Ventricular assist devices (VADs) may be used as a bridge to transplant.

Outcomes and Prognosis

Overall survival rates for PA/IVS have improved significantly with advancements in diagnosis and management, now approaching 70-90%. However, prognosis varies depending on the specific anatomical features and the chosen management pathway. The presence of Right Ventricle Dependent Coronary Circulation (RVDCC) is strongly associated with increased morbidity and mortality due to the risk of myocardial ischemia. Long-term complications can include issues related to the chosen repair pathway, such as need for reintervention on shunts or conduits, residual valve issues, or challenges associated with Fontan circulation if a single ventricle pathway is followed.

Differential Diagnoses

Other congenital heart defects presenting with neonatal cyanosis and decreased pulmonary blood flow should be considered in the differential diagnosis, including Tetralogy of Fallot (TOF), Transposition of the Great Arteries (TGA) with pulmonary stenosis, single ventricle lesions with severe pulmonary stenosis, and tricuspid atresia. Severe Ebstein's anomaly of the tricuspid valve with "functional" pulmonary atresia (where the pulmonary valve is anatomically normal but doesn't open due to poor RV function) should also be differentiated from true anatomical pulmonary atresia in PA/IVS, as management differs significantly.

References

1. Dipchand AI, Barron DJ, Floh AA, editors. Manual of Cardiac Care in Children. Cham: Springer Nature Switzerland AG; 2024.

2. Park IS, editor. An Illustrated Guide to Congenital Heart Disease: From Diagnosis to Treatment – From Fetus to Adult. Singapore: Springer Nature Singapore Pte Ltd.; 2019.

3. Gorla SR, Thomas A, Singh AP. Pulmonary Atresia With Intact Ventricular Septum. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK546666/.

4. Manhem S, Odermarsky M, Wåhlander H, Ekman-Joelsson BM. Pulmonary Atresia with Intact Ventricular Septum, a National Comparison Between Interventional and Surgical Approach, in Combination with a Systematic Literature Review. Pediatr Cardiol. 2024 Jul 5; [Epub ahead of print].

5. Johns Hopkins All Children’s Hospital Heart Institute. Pulmonary Atresia w/Intact Ventricular Septum Clinical Pathway. 2025 Mar 11. Available from: https://www.hopkinsmedicine.org/-/media/files/allchildrens/clinical-pathways/heart-institute-paivs-03-25-final.pdf.

6. https://pcics.org/wp-content/uploads/Pulmonary-Atresia-Intact-Ventricular-Septum.pdf 

7. Lai, Wyman W., et al., eds. Echocardiography in pediatric and congenital heart disease: from fetus to adult. John Wiley & Sons, 2021.

Case 1

Case 2

Pulmonary atresia with intact ventricular septum. Severe tricuspid valve annular hypoplasia. Unrestrictive secundum atrial septal defect, with a prominent and floppy septum primum. Severe right ventricular hypoplasia. Small branch pulmonary artery. Patent ductus arteriosus of pulmonary atresia type - tortuous, left to right. Coronary fistulas (sinusoids) within the right ventricle.

PAIVS presentation prepared by Laila Wazneh (NNP) and Dr Shiran S Moore (NHCR fellow) at Montreal Children's Hospital