Pulmonary Atresia With Intact Ventricular Septum


Article Author:
Sudheer Gorla


Article Editor:
Ajay Pratap Singh


Editors In Chief:
David Wood
Andrew Wilt
Hajira Basit


Managing Editors:
Avais Raja
Orawan Chaigasame
Khalid Alsayouri
Kyle Blair
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Abbey Smiley
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beenish Sohail
Hajira Basit
Phillip Hynes
Sandeep Sekhon


Updated:
8/19/2019 1:27:54 PM

Introduction

Pulmonary atresia with an intact ventricular septum (PA-IVS) is one of the rare forms of congenital heart disease (CHD), accounting for less than 1% of total heart defects. This entity was first described by Hunter in 1783 and later by Peacock in 1869. As implied by the name, this disease is characterized by either membranous or long segment muscular atresia of the right ventricular outflow tract (RVOT) in the absence of communication at the level of ventricles. The spectrum of this disease range from simple membranous pulmonary atresia (PA) with normal-appearing right ventricle (RV) to hypoplastic RV with abnormal connections between the right ventricle and coronary arteries. 

Etiology

An insult during the sensitive stages of the embryological development is thought to cause this heart defect. However, the precise abnormality that leads to PA-IVS remains unclear. Few theories postulated to explain the pathogenesis of this disorder includes the primary insult to the pulmonary valve leading to an atretic valve, abnormal venous valve limiting the flow of the flow through the tricuspid valve into the RV, or as a result of abnormal coronary arterial development. 

Epidemiology

PA-IVS is the third most common form of cyanotic CHD with incidence varying anywhere between 4 to 8 per 100000 live births. In the United Kingdom and Eire collaborative study published in 1998, the incidence of this disorder was reported to be close to 4 per 100000 live births.[1] In another study published from the United States in 1984, the incidence of PA-IVS was close to 8 per 100000 live births.[2]

With the widespread availability and use of fetal echocardiography, the number of patients with complex forms of CHD, including PA-IVS, being diagnosed during pregnancy across the world is increasing. This fact has not only helped the physicians with planning the care of these neonates ahead of time but also increased the rates of elective termination of pregnancies following the diagnosis of complex CHD. This elective abortions of pregnancies with complex CHD has led to an overall reduction in the incidence of various forms of CHD. When including these elective terminations, the incidence of PA-IVS will be significantly higher than reported.

There is no predilection to either sex, and also there has been no identified association with genetic disorders, even though De Stefano et al. in 2008 reported PA-IVS in monozygotic twins.[3] Genetic evaluation of twins in that report was notable for 55 kb deletion at WFDC8 and WFDC9, and the clinical significance of this gene deletion is unknown. Similarly, in 1992, Chitayat et al. from Canada, reported the incidence of PA-IVS in two siblings with no other associated cardiac anomalies.[4]

Developmental Considerations and Anatomical Characteristics:

With regards to the timing of occurrence, in 1983, Kusche and Van Mierop suggested that the insult that leads to PA-IVS happen later in gestation when compared to pulmonary atresia with ventricular septal defect (PA-VSD).[5] They suggested that the insult leading to PA-VSD occur before complete formation of ventricular septum whereas PA-IVS occur following the completion of ventricular septal formation.

Atresia of the pulmonary valve classifies into membranous and muscular forms. It is essential to distinguish between these two types, as a membranous form of PA has better long term prognosis when compared to muscular PA due to the higher incidence of abnormal connections (discussed in the latter part of this section) between the RV and coronary arteries. Due to high pressures in the RV, the tricuspid valve is generally abnormal. The tricuspid valve can be hypoplastic, dysplastic, and can have malformed chordal apparatus.

Another characteristic feature, if present, of PA-IVS, are the abnormal connections between the RV and coronary arteries. The RV, especially in patients with competent tricuspid valve, is hypertensive due to lack of egress for the blood. Due to which the RV develop these abnormal connections with the epicardial coronary arteries, which help to decompress the ventricle. These abnormal connections, when present over time leads to progressive stenosis of the coronary arteries related to high-velocity blood flowing through these abnormal connections. Due to progressive stenosis of the coronary arteries over time, some parts of the myocardium depends on right ventricle for the perfusion and is known as right ventricular dependent coronary circulation  (RVDCC). Due to the progressive nature of RVDCC, it correlates with poor prognosis. 

History and Physical

The most prevalent presenting signs and symptoms include cyanosis and desaturations. Neonates with PS-IVS become symptomatic following the closure of the patent ductus arteriosus as their pulmonary circulation is dependent on it. They rarely present or have the symptoms of decreased cardiac output due to obligatory right to left shunting at the level of atrial septum through foramen ovale. The presence of low cardiac output syndrome should raise suspicion for myocardial ischemia, especially in patients with coronary fistulae. As noted with many other forms of cyanotic CHD, these patients will not have an improvement in their cyanosis/desaturations with 100% oxygen delivery, failed hyperoxia test.

On cardiac auscultation, the examiner will note single first and second heart sounds. If there is a regurgitation of the tricuspid valve, a pansystolic murmur is audible at the left lower sternal border. An additional murmur related to the flow across patent ductus arteriosus might be audible in patients with patent ductus, especially following the initiation of prostaglandin infusion to maintain the ductal patency. The peripheral pulses and capillary refill time are usually normal except in patients with a severely restrictive right to left shunting at the level of atria.

Evaluation

2D echocardiography, an easy and readily available modality of cardiac evaluation, is used in the diagnosis of PA-IVS.  Due to the widespread availability and use of fetal echocardiography in conjunction with prenatal screening for CHD, majority of the patients with this disorder get diagnosed prenatally. In a recently published study on the utilization of fetal echocardiography, the overall rate of prenatal diagnosis for this specific heart defect was approximately 86%.[6]

The diagnosis of PA-IVS is possible with echocardiogram alone, but the additional information regarding the coronary circulation, which are significant predictors of outcomes and type of repair, cannot be discerned from this modality alone. In spite of providing information regarding the anomalous connections between the RV and coronary arteries, it is not useful in the diagnosis of RVDCC. Therefore, cardiac catheterization with angiograms is often needed to arrive at a complete diagnosis, which includes the assessment for fistulous connections between the RV and coronary arteries and RVDCC.

Echocardiogram:

The diagnosis of PA-IVS is possible from an apical four-chamber sweep. The absence of an outflow tract from the RV with intact ventricular septum is the diagnostic finding. While performing the echocardiography in these patients, special attention should focus on the anatomy of the interatrial septum, tricuspid valve, RV, and branch pulmonary arteries.

Interatrial septum:

These patients depend on the obligatory right to left shunting at the level of the interatrial septum to maintain the cardiac output and systemic perfusion. Therefore, it is prudent to evaluate for any obstruction across the interatrial septum. The subcostal views are generally optimal in imaging this part of the heart. A combination of 2D imaging, color doppler imaging, and spectral Doppler imaging are required to complete the assessment of the interatrial septum.

Tricuspid valve:

The assessment of the anatomy of the tricuspid valve is very crucial in these patients as the adequacy of the tricuspid valve is one of the major factor influencing the type of surgical repair. The assessment of the tricuspid valve should include the size of the tricuspid valve annulus, morphology of the valve leaflets, functional status of the valve (atretic vs. patent; competent vs. regurgitate). The patients with regurgitant tricuspid valve have a lower incidence of coronary anomalies as regurgitation through the valve helps to decompress the RV.

Right ventricle:

The morphological characteristics of the RV is another parameter that requires assessment in detail during the echocardiogram. Generally, the size of the RV is proportional to the size of the tricuspid valve. More than the absolute size of the right ventricle, it is important to evaluate the morphological characteristics of the right ventricle, which divides into three components, namely inflow, apical, and outflow. If the RV is tripartite, well-developed inflow, apical, and outflow components, the neonates can undergo biventricular repair even if it is hypoplastic, given that all the other characteristics favor the biventricular repair.  

Cardiac catheterization:

The cardiac catheterization with angiocardiography is often used in the evaluation of patients with PA-IVS as it provides additional information regarding coronary circulation; this is particularly important in patients in whom decompression of the RV is a consideration. The primary goal of the cardiac catheterization is to assess for RVDCC. The diagnosis of RVDCC is made when a significant portion of the ventricular myocardium depends on RV for the blood supply. The angiographic criteria for the diagnosis of RVDCC include stenosis of two or more major coronary arteries or atresia of the coronary ostia and the myocardium distal to the obstruction receiving the blood supply via fistulous connections from the RV. Loomba et al. proposed the aortic perfusion score based on the angiographic characteristics of coronary perfusion, as a predictor of patient outcomes.[7]

Galindo et al. described various angiographic techniques that will help in obtaining adequate/optimal coronary imaging. The various techniques described in that article include RV angiogram, aortogram, aortogram with balloon occlusion of the aorta, and selective coronary angiograms. The evidence of myocardial ischemia on the surface electrocardiogram following the placement of the catheter in the RV (decompression of the RV from catheter-related tricuspid valve regurgitation) is very suspicious for RVDCC.   

Treatment / Management

Medical Management:

Immediately following the diagnosis of PA-IVS, an attempt should be made to initiate prostaglandin infusion to maintain the patency of ductus arteriosus. This action is vital for preoperative survival of these patients, as ductus arteriosus is the sole source of pulmonary blood flow. Also, it is crucial to manipulate pulmonary vascular and systemic vascular resistance to achieve optimal pulmonary and systemic blood flow.

Procedural management:

The patients with PA-IVS will need an intervention, either a catheter-based intervention or surgical procedure, as a neonate. As a result of the complexity and heterogeneity of this disorder, there is no single procedure that will be effective for all patients. Even though the biventricular repair is the ideal and preferred surgical approach, the management of this disorder has to be highly individualized. The preferred surgical or transcatheter intervention is influenced by several variables, which include tricuspid valve size and function, RV anatomy, coronary artery anatomy, and type of pulmonary atresia.

The currently available therapeutic algorithms are quite diverse. Chikkabyrappa et al. published an article in which they discuss the various therapeutic options for this disorder.[8] According to that article:

  1. Patients with adequate and tripartite RV size which is functionally tripartite, tricuspid valve z-score greater than 2.5, and normal coronary artery anatomy would benefit from biventricular repair (Radiofrequency perforation of the pulmonary valve for pulmonary atresia and surgical right ventricular outflow tract reconstruction for long segment atresia).
  2. Patients with borderline bipartite hypoplastic RV, tricuspid valve z-scores between -2.5 to -4.5 might benefit from attempted biventricular repair ± systemic to pulmonary shunt. These patients require close surveillance for RV growth, in the absence of which, they will benefit from one and a half ventricular repair.
  3. Single ventricular repair (bidirectional Glenn followed by Fontan) should be a consideration in patients with severe RV hypoplasia and patients with RVDCC.
  4. Primary heart transplantation might be a reasonable approach in patients with myocardial ischemia related to coronary artery abnormalities.

Clinicians should recall that the patients in categories 2, 3, and 4 will need systemic to pulmonary artery shunt or stenting of the PDA in the immediate newborn period.

Differential Diagnosis

Since the major presenting symptoms are desaturations and cyanosis, we need to exclude other respiratory and cardiac causes of these symptoms.

Prognosis

Several studies have shown a gradual improvement in the survival of patients with this disorder, thought to be due to the advancements in the field of pediatric cardiology and cardiothoracic surgery. In a population-based study from the UK and Ireland published in 2005, the 1-year survival was about 71%, and 5-year survival was approximately 64%.[9] In the same article, the authors have found that low birth weight and unipartite right ventricle were the independent risk factors for death. RVDCC, especially atresia of the coronary ostia, is an independent risk factor for poor outcomes.[10] 

Complications

In the absence of extensive aortopulmonary collaterals, PA-IVS is not compatible with life in the absence of ductal patency. 

Deterrence and Patient Education

Pulmonary atresia with the intact ventricular septum (PA-IVS) is a rare and complex form of congenital heart defects with a broad spectrum of presentation. An insult during sensitive stages of embryological development is proposed to lead to PA-IVS. The presentation of this entity is similar to other complex cyanotic congenital heart defects with decreased pulmonary blood flow like tetralogy of Fallot. 

The echocardiogram plays a vital role in diagnosing PA-IVS. Cardiac catheterization provides additional information regarding the status of the coronary circulation. 

The management of patients with this heart defect is complex. Many therapeutic algorithms guide the medical team in the management of these patients.

Enhancing Healthcare Team Outcomes

An interprofessional approach is needed to achieve optimal outcomes in these patients. The team most often include pediatric cardiologist, pediatric cardiothoracic surgeon, obstetrician, and maternal-fetal specialist (fetal diagnosis), neonatal-perinatal specialist, ICU nurses, and a cardiac intensivist. In patients diagnosed prenatally, it is imperative to have a management plan even before the baby is delivered. In individual cases, it is not unreasonable to consider delivering the neonate in a tertiary care center, where pediatric cardiothoracic surgical services are available. Every attempt should be made to prevent delivery of the neonate during weekends and holidays when hospitals are not at full staffing.

Nursing will work with both the specialists and physicians as well as the family to help ensure care is optimal. They can offer to counsel and answer family questions. Surgical nurses are invaluable during any delivery and subsequent neonatal surgery and will participate in neonatal ICU care following procedures, reporting all status changes to the managing physicians. Only with this type of interprofessional collaboration can the mother and child achieve the best possible outcome. [Level V]

The patents should receive detailed counsel from the team of nurses and doctors regarding heart defect and surgical strategies under consideration in the management of this complex disorder. Also, they understand the implications regarding the increased risk of heart defects with future pregnancies. 


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Pulmonary Atresia With Intact Ventricular Septum - Questions

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A 2-day old full-term male neonate presents to the emergency room presents with cyanosis and irritability. On arrival, his vital signs were notable for tachycardia (HR: 195 bpm), desaturation (O2 sat: 78%). He was noted to have purplish discoloration of the tongue. His cardiac auscultation was notable for single S2 and no audible murmur. His echocardiogram demonstrated atresia of the right ventricular outflow tract. On the echocardiogram, the tricuspid valve Z-score was -2.35. The right ventricle was hypoplastic. There was a tiny restrictive patent ductus arteriosus with a left to right shunting. The branch pulmonary arteries were confluent, and Z-scores were -1.75 and -1.9 for the left pulmonary artery and right pulmonary artery, respectively. The neonate was started on the prostaglandin infusion. Following the stabilization of his metabolic status, he was taken to the cardiac catheterization. During cardiac catheterization, he had a sudden decompensation in his clinical status with hypotension and tachycardia while performing the right ventricular angiogram. A stat echocardiogram done in the cath lab showed at least moderately reduced function of the left ventricle with mild mitral regurgitation. Which of the following factors is a contraindication for biventricular repair in this patient?



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A 48-hour old male neonate born at term was found to have central cyanosis on examination. The vital signs on presentation were: afebrile, respiratory rate: 38 breaths per minute, heart rate: 153 beats per minute, blood pressure: 74/55 mm Hg, O2 sat: 89% on room air. Chest x-ray done showed no normal lung. On hyperoxia test, there was no improvement in the saturation in the upper and lower extremities. The echocardiogram performed in view of the results of the hyperoxia test demonstrated severely hypoplastic right ventricle and tricuspid valve. There is no color doppler evidence of flow across the pulmonary valve into the pulmonary arteries. Right to left shunting is noted across the interatrial septum. Which of the following is the most likely explanation for worsening of cyanosis in this neonate?



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A 2-day old full-term female neonate is brought to the healthcare provider with the complaint of irritability. The vital signs were notable for tachycardia (heart rate: 192 beats per minute) and desaturations (oxygen saturation: 78% on room air). On exam, the neonate was irritable and not consolable. On auscultation, he was noted to have a single S1 and single S2 with no audible murmur. An echocardiogram showed membranous pulmonary atresia with the intact ventricular septum (PA-IVS). Echocardiogram was also suspicious of an abnormal connection between the right ventricle and coronary arteries. The tricuspid valve Z-score was -2.5, the right ventricle is tripartite. The neonate was started on prostaglandin infusion and was later taken to the cardiac catheterization laboratory. On injection of the contrast into the right ventricle, the contrast was seen in the coronary arteries and lumen of the ascending aorta. What is the most appropriate procedural management in this neonate?



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A 5-month old male infant with a previous diagnosis of pulmonary atresia with intact ventricular septum (PA/IVS) is brought to the emergency department due to poor feeding. He underwent placement of systemic to pulmonary shunt as a neonate and is scheduled to undergo bidirectional Glenn surgery in 3-weeks time. During his last clinic visit, his cardiologist was concerned about some obstruction to the flow in his heart, which he thought can be addressed during the surgery. Over the last couple of weeks, the infant seemed to be more irritable and is not feeding well. His mother also noticed that his abdomen is more distended. Vital signs show a pulse of 178/min, respiratory rate 35/mmin, blood pressure 65/50 mmHg, and oxygen saturation 82%. On examination, a continuous murmur is heard over the precordium. His liver is 5 cm below the costal margin. Laboratory evaluation is notable for elevated AST, ALT, BUN, and creatinine. What is the most likely etiology for the infant's current clinical presentation?



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A 4-month old male neonate with a history of pulmonary atresia with an intact ventricular septum (PA-IVS), status post modified Blalock-Tausig shunt presents to the emergency room with new-onset irritability. The vital signs on presentation are, temperature 98 Fahrenheit, heart rate 192 beats per minute, respiratory rate 55 breaths per minute, blood pressure 65/52 mmHg, and oxygen saturation: 76% (baseline sat: 80-85%) on room air. The capillary refill time in the lower extremity was 4 seconds. A continuous murmur is heard over the precordium. On further history, his mother recalls that the infant's cardiologist mentioned regarding abnormal connections in the infant's heart, which prevent him from a having a certain type of surgery and now he requires three surgeries. Which of the following is most likely be responsible for the neonate's clinical deterioration?



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Pulmonary Atresia With Intact Ventricular Septum - References

References

Daubeney PE,Sharland GK,Cook AC,Keeton BR,Anderson RH,Webber SA, Pulmonary atresia with intact ventricular septum: impact of fetal echocardiography on incidence at birth and postnatal outcome. UK and Eire Collaborative Study of Pulmonary Atresia with Intact Ventricular Septum. Circulation. 1998 Aug 11;     [PubMed]
Ferencz C,Rubin JD,McCarter RJ,Brenner JI,Neill CA,Perry LW,Hepner SI,Downing JW, Congenital heart disease: prevalence at livebirth. The Baltimore-Washington Infant Study. American journal of epidemiology. 1985 Jan;     [PubMed]
De Stefano D,Li P,Xiang B,Hui P,Zambrano E, Pulmonary atresia with intact ventricular septum (PA-IVS) in monozygotic twins. American journal of medical genetics. Part A. 2008 Feb 15;     [PubMed]
Chitayat D,McIntosh N,Fouron JC, Pulmonary atresia with intact ventricular septum and hypoplastic right heart in sibs: a single gene disorder? American journal of medical genetics. 1992 Feb 1;     [PubMed]
Kutsche LM,Van Mierop LH, Pulmonary atresia with and without ventricular septal defect: a different etiology and pathogenesis for the atresia in the 2 types? The American journal of cardiology. 1983 Mar 15;     [PubMed]
Gorla SR,Chakraborty A,Garg A,Gugol RA,Kardon RE,Swaminathan S, Emerging trends in the prenatal diagnosis of complex CHD and its influence on infant mortality in this cohort. Cardiology in the young. 2018 Dec 26;     [PubMed]
Loomba RS,Pelech AN, Aortic perfusion score for pulmonary atresia with intact ventricular septum: An antegrade coronary perfusion scoring system that is predictive of need for transplant and mortality. Congenital heart disease. 2018 Jan;     [PubMed]
Chikkabyrappa SM,Loomba RS,Tretter JT, Pulmonary Atresia With an Intact Ventricular Septum: Preoperative Physiology, Imaging, and Management. Seminars in cardiothoracic and vascular anesthesia. 2018 Sep;     [PubMed]
Daubeney PE,Wang D,Delany DJ,Keeton BR,Anderson RH,Slavik Z,Flather M,Webber SA, Pulmonary atresia with intact ventricular septum: predictors of early and medium-term outcome in a population-based study. The Journal of thoracic and cardiovascular surgery. 2005 Oct;     [PubMed]
Cheung EW,Richmond ME,Turner ME,Bacha EA,Torres AJ, Pulmonary atresia/intact ventricular septum: influence of coronary anatomy on single-ventricle outcome. The Annals of thoracic surgery. 2014 Oct;     [PubMed]

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