Pulmonary atresia with intact ventricular septum (PA-IVS) is a rare and complex cyanotic congenital heart defect characterized by the complete absence of anatomical continuity between the right ventricle and the pulmonary arterial tree, in the presence of a completely intact ventricular septum. Unlike the variant associated with a ventricular septal defect (PA-VSD), this form lacks any shunt between the two ventricles, making pulmonary blood flow entirely dependent on alternative routes, primarily the patent ductus arteriosus and, to a variable extent, coronary fistulae.
PA-IVS is a critical congenital heart disease from birth, resulting in severe systemic hypoxemia due to the inability of systemic venous blood to reach the lungs via the normal right ventricle–pulmonary artery pathway. The only available pulmonary blood flow is that provided by the patent ductus arteriosus (PDA), whose spontaneous closure leads to a rapidly fatal course without intervention.
This condition accounts for approximately 1–3% of all congenital heart defects, with an estimated prevalence of 0.7–1.0 cases per 10,000 live births. It is frequently associated with right ventricular hypoplasia, tricuspid valve atresia or dysplasia, coronary anomalies, and in some cases, restrictive interatrial communications.
Prognosis and therapeutic strategy are tightly linked to the right ventricular morphology and the presence of abnormal coronary connections, which determine whether a biventricular repair is feasible or if a palliative univentricular approach (e.g., Fontan pathway) is required.
Pulmonary atresia with intact ventricular septum results from an early developmental defect of the right ventricle outflow tract, occurring between the fifth and seventh weeks of gestation. Normally, during embryonic development, the conus arteriosus divides into two components: an anterior portion that forms the right ventricular outflow tract and pulmonary valve, and a posterior portion that develops into the left ventricular outflow tract and aortic valve. In PA-IVS, there is complete obliteration of the right infundibulum and failure of pulmonary valve canalization.
The intact ventricular septum prevents any direct decompression of the right ventricle into the left, leaving the coronary circulation as the only outflow pathway. Due to elevated pressure and right ventricular hypertrophy, ventriculo-coronary fistulae develop, directly connecting the right ventricle to the epicardial coronary arteries. This compromises normal coronary perfusion and creates a condition known as right ventricular–dependent coronary circulation.
This situation exposes the neonate to a high risk of myocardial ischemia in the event of sudden right ventricular decompression (e.g., after pulmonary valvulotomy), since the coronary arteries are no longer perfused from the aorta but depend entirely on the right ventricle. The risk of acute infarction and sudden death in these scenarios is extremely high.
From a pathophysiological perspective, survival depends on the presence and patency of the ductus arteriosus, which allows blood to flow from the aorta to the pulmonary artery and undergo oxygenation. A patent foramen ovale or a wide atrial communication is also essential to permit systemic venous return to pass into the left heart and systemic circulation.
Based on the right ventricular morphology and the distribution of coronary fistulae, two major functional phenotypes are distinguished:
The clinical picture of PA-IVS typically emerges in the first hours of life with severe central cyanosis and signs of systemic hypoxemia. The lack of communication between the right ventricle and the pulmonary circulation results in fully oxygenated flow depending on the patent ductus arteriosus, whose physiological postnatal closure leads to rapid clinical deterioration. In neonates with restrictive atrial communications or extensive coronary fistulae, symptoms can be particularly early and dramatic.
The most frequent presenting signs include:
In cases with a restrictive foramen ovale or absent atrial decompression, right heart failure can rapidly develop with systemic congestion, hepatomegaly, and jugular vein distention. Progressive right ventricular hypertrophy exacerbates coronary hypoperfusion, leading to an early risk of myocardial ischemia and arrhythmias.
Some neonates may present with a systolic murmur if there is tricuspid regurgitation or ductal flow turbulence; however, auscultation is often silent or unremarkable. The clinical hallmark remains cyanosis unresponsive to high-flow oxygen, which should always prompt suspicion of a critical cyanotic congenital heart disease.
The clinical picture varies depending on ventricular morphology and coronary anomalies. In cases of severe right ventricular hypoplasia with coronary dependence, systemic compromise is rapid and severe, potentially evolving toward cardiovascular collapse unless promptly treated with prostaglandins and atrial decompression.
PA-IVS should be suspected in any full-term neonate presenting with persistent central cyanosis uncorrectable by high-flow oxygen, particularly in the absence of significant auscultatory findings. The clinical presentation may initially mimic a respiratory disorder, but consistently low oxygen saturation despite oxygen therapy is a critical sign pointing toward a cyanotic congenital heart defect.
The cornerstone of diagnosis is transthoracic echocardiography, which confirms the presence of:
Particular attention must be paid to the assessment of the epicardial coronary arteries, whose dilation and retrograde flow may indicate right ventricular–dependent coronary circulation. In the presence of suspicious findings, early cardiac catheterization is necessary to perform a detailed angiographic study of the coronary circulation.
Cardiac catheterization is also useful for measuring intracardiac pressures, assessing the patency and direction of shunting through the foramen ovale, and for performing an atrial septostomy if atrial decompression is inadequate. Right ventricular morphology, continuity between the right ventricle and the coronary arteries, and the degree of tricuspid annular hypoplasia are all crucial factors in defining the therapeutic strategy.
Fetal echocardiography can establish the diagnosis as early as the second trimester, allowing for appropriate planning of delivery in tertiary care centers with neonatal cardiac surgery facilities. Prognosis is significantly improved in cases diagnosed prenatally and managed with dedicated care pathways.
Pulmonary atresia with intact ventricular septum is a neonatal cardiac emergency that requires early and highly individualized therapeutic intervention.
The treatment strategy is primarily based on three factors:
Depending on these variables, treatment may aim at biventricular repair, intermediate palliation, or definitive univentricular repair.
The first step in managing the neonate is hemodynamic stabilization. Administration of prostaglandin E1 is essential to maintain ductal patency and ensure adequate pulmonary blood flow. If atrial decompression is inadequate, a balloon atrial septostomy (Rashkind procedure) is indicated to enable right-to-left shunting of venous blood.
In patients with a sufficiently developed right ventricle, appropriately sized tricuspid valve, and normal coronary arteries not dependent on the right ventricle, a program of functional biventricular rehabilitation can be planned, aiming to restore a physiologic two-ventricle circulation. This therapeutic approach is progressive and tailored to the individual anatomy, with the ultimate goal of re-establishing continuity between the right ventricle and the pulmonary artery.
The first step involves pulmonary valvulotomy, which can be performed percutaneously using a balloon catheter or via direct surgical technique. This intervention entails controlled opening of the atretic valvular orifice, allowing blood to flow from the right ventricle into the pulmonary artery, thereby initiating functional remodeling and activation of the right ventricular chamber.
Subsequent interventions may be required depending on hemodynamic response and the growth of involved structures, including enlargement of the right ventricular outflow tract, dilation of the pulmonary valve annulus, and gradual ductal closure. During this phase, cardiac physiology is carefully guided toward biventricular autonomy, enabling the right ventricle to effectively sustain pulmonary flow.
In some cases, controlled pressure loading techniques are applied to promote morphological and functional growth of the right ventricle by maintaining a workload that encourages adaptation without inducing failure.
Achieving biventricular repair represents the most favorable outcome, as it restores pulsatile blood flow to the lungs, with reduced risk of long-term complications and greater hemodynamic stability compared to palliative univentricular pathways.
In cases with marked right ventricular hypoplasia, dysplastic tricuspid valve, and documented coronary dependence, right ventricular decompression is contraindicated due to the risk of fatal myocardial infarction.
In such patients, a palliative univentricular approach is adopted, following the classic steps of the Fontan pathway:
In selected intermediate cases, a surgical strategy known as 1.5 ventricle palliation may be employed. This is reserved for patients with a hypoplastic but functionally useful right ventricle that cannot support the entire systemic venous return but can contribute partially to the circulation.
This technique involves direct connection of the superior vena cava to the pulmonary artery (bidirectional Glenn anastomosis), while the inferior vena cava continues to drain into the right heart. The result is a reduced hemodynamic load on the systemic ventricle, with a more balanced pressure distribution and more efficient blood flow.
This procedure is indicated when there is preserved residual ventricular function, competent tricuspid valve, and absence of coronary dependence, conditions that make the right ventricle suitable to participate, albeit partially, in the overall cardiac workload without bearing the full burden.
Prognosis is strongly influenced by anatomical subtype and therapeutic pathway. Patients undergoing biventricular repair have better survival rates and quality of life, but represent a minority. In forms managed with a univentricular approach, long-term survival has improved thanks to advances in surgical techniques, although there remains a significant risk of late complications such as ventricular dysfunction, arrhythmias, and failed Fontan physiology.
Follow-up must be continuous and multidisciplinary, including cardiologic assessment, echocardiography, and often cardiac magnetic resonance imaging, to monitor cardiac function, central venous pressures, and the possible development of systemic-to-pulmonary collaterals or valvular dysfunction. In patients with coronary dependence, surveillance must be even more rigorous due to the risk of late-onset ischemia.
PA-IVS is a congenital heart disease with a high risk of both early and late complications, whose nature depends on ventricular morphology, the chosen therapeutic approach, and the presence of coronary anomalies. The overall clinical course is influenced by anatomical complexity and the timeliness of initial therapeutic decisions.
In neonates, one of the most feared complications is acute myocardial ischemia due to right ventricular–dependent coronary circulation. If unrecognized, decompression of the hypertensive right ventricle can result in a critical drop in coronary perfusion, with fatal outcome due to massive infarction. This risk requires extreme caution when considering valvulotomy or decompressive shunts.
In the early postoperative phase, ventricular dysfunction, tricuspid regurgitation, and arrhythmias may occur, particularly in patients with severely hypoplastic right ventricles or valvular dysplasia. Hemodynamic instability often necessitates prolonged inotropic support and intensive postoperative mechanical ventilation.
Over the long term, patients undergoing univentricular palliation are exposed to complications typical of Fontan physiology, including:
In patients undergoing biventricular repair, complications may include progressive tricuspid regurgitation, re-narrowing of the reconstructed infundibulum, pulmonary annular stenosis, or the need for reoperation due to valve dysfunction. Right ventricular diastolic dysfunction may emerge even in the absence of significant residual stenosis.
Particular attention should be paid to the risk of infective endocarditis in all patients with prosthetic materials or palliated circulations, and to the monitoring of neurological status and neurocognitive development, given the high vulnerability associated with early hypoxemia, neonatal surgery, and suboptimal cerebral perfusion during the first months of life.
A multidisciplinary follow-up is essential to ensure quality and continuity of care, including serial cardiologic evaluations, advanced functional imaging, and integrated management of extracardiac comorbidities. Early identification of complications enables timely intervention and may significantly improve long-term functional outcomes.
The two definitions refer to distinct conditions from an anatomical, embryological, and occasionally management standpoint. Here are the key differences:
In practice, PA-IVS is a specific subtype of pulmonary atresia without ventricular communication, characterized by well-defined morphological and pathophysiological features, including:
By contrast, not all forms of pulmonary atresia without VSD necessarily exhibit these features. Some may have a well-formed tricuspid valve, a larger right ventricle, and no coronary anomalies: in such cases, a biventricular repair may be considered—a scenario that is exceedingly rare in classic PA-IVS.
| Feature | PA with Intact Ventricular Septum (PA-IVS) | PA without Ventricular Septal Defect (generic) |
|---|---|---|
| Definition | Specific form of pulmonary atresia with intact septum and typical associated anomalies | Broader category including all forms without ventricular communication |
| Prevalence | Rare (<1% of congenital heart diseases) | Includes a wider variety of less well-defined cases |
| Right ventricle | Typically hypoplastic, often rudimentary | Variable hypoplasia; sometimes well developed |
| Tricuspid valve | Almost always dysplastic or stenotic | Can be normal, dysplastic, or hypoplastic |
| Coronary circulation | Often with fistulae and RV-dependent flow | Rarely RV-dependent; more often normal |
| Pulmonary artery | Often hypoplastic or absent | Variable: hypoplastic, normal, or absent |
| Feasibility of biventricular repair | Very rare, generally not feasible | Possible in cases with a well-developed RV |
| Typical treatment | Univentricular palliation (Fontan) or 1.5 ventricle strategy | Univentricular palliation or, in selected cases, biventricular repair |
| Prognosis | Affected by RV hypoplasia and coronary dependence | Generally better in biventricular candidates |