Synonyms: Pulmonary atresia with intact ventricular septum, Type I, Type II¹, Tricuspid atresia with hypoplasia of the right ventricle²; pulmonary valve fusion with intact ventricular septum;  Pulmonary atresia with normal aortic root.

Incidence: Approximately 1 to 3% of all congenital cardiac defects³.

Definition: Atresia of the proximal pulmonary arterial circulation in the presence of an intact ventricular septum results in right ventricular pathology that is dependent upon competency of the tricuspid valve. In most cases, the tricuspid valve remains competent, which renders the right ventricle hypertrophic with an extremely small chamber volume (Type 1). Less frequently, tricuspid incompetence results in a right ventricular chamber diameter that is either normal or enlarged (Type II). In Type I disease, retrograde flow through sinusoids that supply the right ventricle results in communication with and dilatation of the coronary arterial circulation. 

Etiology: Unknown. Proposed theories have included viral or other infectious agents resulting in local disruption of pulmonary valve and proximal pulmonary artery embryogenesis or local destruction of previously formed vasculature. 

Pathogenesis: Type I: pulmonary artery atresia leads to massive right ventricular hypertrophy and obliteration of the chamber. Suprasystemic right ventricular pressure results in retrograde flow of blood through feeding sinusoids into the coronary artery circulation. Type II: tricuspid insufficiency allows retrograde flow of blood into the right atrium and through an atrial septal defect that is almost invariably present. Right ventricular chamber diameter is normal or enlarged.

Associated anomalies: Cardiac: atrial septal defect, tricuspid atresia, proximal pulmonary artery atresia, right atrial dilatation, aortic stenosis, Ebstein anomaly of the tricuspid leaflets³. Extracardiac: None. 

Differential diagnosis: Tricuspid atresia with hypoplastic right ventricle and ventricular septal defect³.

Prognosis: Lethal if uncorrected. Palliative shunting between systemic and pulmonary circulation distal to point of pulmonary artery atresia successful in some series. Prognosis has improved significantly since introduction of PGE, for maintenance of ductal patency and sophistication of surgical repair. 

Recurrence risk: Multifactorial inheritance suggests risk of recurrence of 3-5%.

Management: In utero diagnosis with fetal echocardiography demands search for extracardiac malformations and chromosomal analysis as for any complex cardiac lesion. A scheduled induction of labor, after documentation of pulmonary maturity, should be made with close consultation with neonatologist, pediatric cardiologist, and cardiac surgeon.

MESH Pulmonary-Artery-abnormalities BDE 0837 ICD9 746.0 CDC 7460.000

Address correspondence to Gary Joffe, MD, University of New Mexico Medical Center, Dept. of Obstetrics and Gynecology, 211 Lomas Boulevard, NE, Albuquerque, New Mexico 87131-5286 Ph: 505-272-6386, Fax: 505-272-6385 ¶Division of Pediatric Cardiology

Introduction 

Pulmonary atresia with intact ventricular septum is a complex cardiac lesion that has been extensively described in the cardiovascular literature, and is characterized by one of two patterns of pathophysiology.

In Type I disease, a combination of pulmonary valvular atresia, competence of the tricuspid valve, and an intact ventricular septum result in massive right ven­tri­cular hypertrophy and chamber obliteration with supra­systemic pressures. Suprasyste­mic pressures force blood through the myocardial sinusoids that feed the right ventricle into the coronary circulation. Coronary dilatation with areas of stenosis are the result of turbulent flow.

In Type II disease, proximal pulmonary arterial atresia and an intact ventricular septum are present, but tricuspid incompetence allows retrograde flow of blood into the right atrium and across an atrial septal defect. Thus, in Type II disease, the right ventricle is either normal or dilated. Fetal echocardiography, continuous and pulsed Doppler, and color flow Doppler have allowed detailed characterization of the disease in utero, including assessment of retrograde flow through myocardial sinusoids into the coronary circulation. Through a combination of the use of PGE₁ and advances in cardiac surgery, survival has improved during the past decade. This report describes a recent case of pulmonary atresia with intact ventricular septum evaluated at our institution and presents fetal echocardiographic evidence of massive dilatation of the coronary circulation with confirmation during neonatal cardiac catheterization. 

Case report 

The patient is a 25-year-old G₂P₁ Hispanic woman who presented for her initial ultrasound at 26 weeks of gestation. A targeted ultrasound was performed upon notation of an abnormal 4-chamber view of the heart. The targeted ultra­sound demonstrated a hypoplastic right ventricle, intact ventricular septum, enlarged aorta, and non-visualization of the pulmonary outflow tract. There were no extracardiac ano­malies noted. The patient was referred to the Division of Pediatric Cardiology where a formal fetal echocardiogram was performed.

Findings included severe hypertrophy and hypoplasia of the right ventricle, a patent but hypoplastic tricuspid valve, no right ventricular outflow tract, a large dilated aortic arch, and non- visualization of the proximal pulmonary artery (fig. 1-4).

Fig. 1: Atrial septal defect is invariably present in pulmonary valve atresia with  intact ventricular septum

Fig. 2: Distended coronary sinus. Flow across the coronary sinus into right atrium and across atretic tricuspid valve completes a “right-sided circular shunt”.

Fig. 3: Hypoplastic right heart, with color Doppler evidence of retrograde flow towards the aorta.

Fig. 4: Myocardial sinusoid with flow towards the aorta.

Both right and left coronary arteries were markedly dilated. The presence of an atrial septal defect was also noted. Color and pulsed Doppler were used to demonstrate turbulent flow in the ductus arteriosus, which flowed in a left-to-right direction. Turbulent flow was also noted in the direction of the right ventricle through dilated sinu­soids into the coronary arteries and ultimately into the aorta.

At a later date, a rapid fetal karyotype was obtained by performing percutaneous umbilical blood sampling and was noted to be 46, XY. The patient was counseled that although the fetal prognosis was quite guarded, pulmonary atresia with intact ventricular septum has been demonstrated to be amenable to surgical repair.

At term, the patient underwent repeat cesarean section with delivery of a viable 3850g male infant with Apgars of 5 at one minute and 9 at 5 minutes. During the first hours of life, a neonatal cardiac echo was performed and confirmed the findings that were obtained in utero. An infusion of PGE₁ was begun to maintain patency of the ductus arteriosus.

The neonate was then taken for cardiac catheterization, which demonstrated pulmonary atresia, massive right ventricular hypertrophy and suprasystemic pressure (120mm Hg compared to 60mm Hg in the left ventricle and aorta) (fig. 5), massive dilatation of the coronary circulation with areas of stenosis, an atrial septal defect, and a large patent ductus arteriosus (fig. 6).

Fig. 5: Cardiac catheterization with pressure tracing that demonstrates the suprasystemic pressure of the right ventricle.  Small pressure waveform is from the umbilical artery.

Fig. 6: Neonatal cardiac angiography demonstrates retrograde filling of the myocardial sinusoids during right ventricular systole.

An atrial septostomy was performed at cardiac catheterization secondary to a 20mm pressure gradient between right and left atria. The neonate was stabilized and on the third day of life underwent cardiac surgery that included right ventricular exclusion (placement of a Teflon patch over the tricuspid valve), aorta to pulmonary artery shunt, and PDA ligation. In addition, the atrial septostomy was enlarged. The coronary arteries were noted to have a diameter of 4-5mm. The neonate tolerated the surgery well. However, two days after surgery he suffered cardiac arrest and resuscitation effort were unsuccessful.

Discussion

Definition

Pulmonary atresia with intact ventricular septum was described over two centuries ago³ and is characterized by atresia of the pulmonary valve with an intact ventricular septum.  Two types of pulmonary atresia with intact ventricular septum have been described.

Type I

The more common form of the disease, Type I, is characterized by a relative competence of the tricuspid valve (even in the presence of tricuspid pathology) with a resulting right ventricular hypertrophy and obliteration of the chamber cavity. As was seen in the case report, suprasystemic right ventricular pressure forces retrograde flow through myocardial sinusoids with eventual dilatation of the coronary circulation.

Type II

Type II disease demonstrates a normal or dilated right ventricle secondary to tricuspid insufficiency. An atrial septal defect is invariably present. Left ventricle and aortic diameters are usually enlarged secondary to increased flow. The tricuspid valve is almost always anomalous. Frequent presentations include hypoplastic valve leaflets, fibrotic valve leaflets, fused commissures, reduced number of chordae tendinae, abnormal attachments to papillary muscles, and frank Ebstein anomaly³.

Myocardial circulation

A prominent feature of this case was the intrauterine demonstration of massively dilated myocardial sinusoids and coronary circulation. This is sometimes referred to as a “right-sided circular shunt”⁴. The blind right ventricle feeds into intramyocardial sinusoids, which, in turn, anastomose with the coronary artery circulation. The coronary arteries drain into the coronary venous system and ultimately into the coronary sinus which is positioned in the right atrium. The circular shunt is completed when the blood that originated in the blind right ventricle returns to this chamber through the atretic tricuspid valve.

Communication between the right ventricle and coronary circulation is felt to be responsible for ischemia within both ventricles secondary to the flow of desaturated blood. The pulmonary lesion in this disease is that of an atretic pulmonary valve apparatus. The main pulmonary artery and the right and left pulmonary arteries are abnormal less than 20% of the time³. In utero, the pulmonary circulation is supplied in a retrograde fashion across the patent ductus arteriosus.

Differential diagnosis

The differential diagnosis for pulmonary atresia with intact septum is tricuspid atresia with ventricular septal defect. The distinction is quite important as extracardiac manifestations are more frequently seen with this disease. Tricuspid atresia with ventricular septal defect comprises 1-3% of congenital heart disease. Extracardiac anomalies are present in 20% of cases, and there is an association with Down syndrome, asplenia, Christian"s disease, and cats eye syndrome³. In summary, the present case demonstrates that the antenatal diagnosis of pulmonary atresia with intact septum is quite easily achieved with fetal echocardiography. The sonographic findings include absence of flow through the pulmonary valve, right ventricular hypertrophy (Type I) or dilatation (Type II), tricuspid atresia, atrial septal defect, and dilatation of myocardial sinusoids with retrograde flow into the coronary circulation.

Prognosis

Prognosis in the neonatal period immediately after birth is directly proportional to the diameter and resistance within the ductus arteriosus.

Management

With the advent of the use of PGE₁ immediate stabilization has improved significantly. However, the neonate is still hypoxic, as the pulmonary blood flow is diminished in comparison to the normal state. Therefore, the first clinical manifestation of unrecognized pulmonary atresia with intact ventricular septum is cyanosis– the degree of which depends upon the amount of flow through the ductus arteriosus. Prior to surgical repair with pulmonary atresia with intact ventricular septum, cardiac catheterization and angiocardiography are essential. Cardiac catheterization allows demonstration of suprasystemic right ventricular pressures (both systolic and diastolic) and normal left heart pressures (fig.  .). Angiocardiography demonstrates retrograde filling of the coronary circulation and as in fig. which outlines the areas of massive dilatation and stenosis.

The surgical approach to the neonate with pulmonary atresia with intact ventricular septum must be individualized to the type and severity of lesions that are present. If the degree of right ventricular hypertrophy has not been enough to seriously compromise chamber volume, then pulmonary valvulotomy may achieve a satisfactory result. Other approaches have included establishing shunts between the aorta and main pulmonary arteries, as in this case, or placing a shunt between the subclavian artery and the pulmonary circulation. In some series, since the advent of PGE₁therapy for maintenance of ductal patency, the early post-surgical mortality has fallen to less than 10%⁵.

Conclusions

Antenatal diagnosis allows complete counseling of the patient in conjunction with the neonatologist, pediatric cardiologist, and cardiac surgeon in order to establish prognosis and plan for intensive peripartum and postpartum management of the neonate.

References

l. Greenwold WE, et al. Congenital pulmonary atresia with intact ventricular septum: Two anatomic types. Circulation 14:945-946 1956.

2. Rosenthal A, Dick, M. Tricuspid atresia. Heart Disease in Infants, Children and Adolescents., 4th ed. Baltimore: Williams and Wilkins, 1989, p348.

3. Marvin W, Mahoney LT: Pulmonary atresia with intact ventricular septum. Heart Disease in Infants, Children, and Adolescents, 4th ed. Baltimore, Williams and Wilkins, 1989, p338.

4. Freedom RM, Harrington DP. Contributions of intramyocardial sinusoids in pulmonary atresia and intact ventricular septum to a right-sided circular shunt. Br Heart J 6:1061-1065 1974.

5. De Leval M, et al. Pulmonary atresia and intact ventricular septum: surgical management based on a revised classification. Circulation, 66:2 1982.