10 Pulmonary Atresia and Intact Ventricular Septum

Rima S. Bader, James C. Huhta

I. CASE

A 30-year-old white woman, gravida 2, para 1+0, referred at 21 weeks’ gestation for an abnormal fetal four-chamber view on prenatal ultrasound. The mother has a 2-year-old daughter with a hypoplastic right heart and pulmonary atresia.

A. Fetal echocardiography findings

1. The fetal echo reveals situs solitus of the atria, levocardia, left aortic arch, and heart rate of 142 bpm.

2. The four-chamber view is abnormal, with a small right ventricle (RV), which is hypertrophied and has reduced systolic function, and a dilated right atrium (RA) (Fig. 10-1).

3. Cardiac axis and position are normal.

4. Cardiac size is increased (cardiothoracic ratio = 0.40).

5. The outflow assessment reveals normally related great arteries with significant asymmetry (aorta–to–pulmonary artery diameter ratio = 1:0.5).

6. The pulmonary valve is atretic, with no antegrade flow in systole and no pulmonary insufficiency.

7. There are good-sized confluent branch pulmonary arteries.

8. The tricuspid valve diameter is small (0.24 cm) (z score = −3), with normal inflow waves (E/A waves).

9. A narrow jet of tricuspid regurgitation (4 m/s) and a dP/dt (change in pressure per change in time) of 600 mm Hg per second.

10. There are possible RV coronary sinusoids.

11. The aortic arch is leftward, with normal antegrade flow.

12. The ductal arch shows flow reversal in systole.

13. There is unrestricted flow through the foramen ovale, with a right- to-left shunt.

14. The pulmonary venous flow pattern is normal. There is also normal flow in the inferior vena cava (IVC), ductus venosus, and umbilical vein.

15. The left ventricular (LV) Tei index (myocardial performance index) is normal to mildly increased (0.48). The RV Tei index could not be calculated due to the pulmonary atresia.

Fig. 10-1 Fetal pulmonary atresia at 32 weeks’ gestation with small right ventricle and dilated right atrium and left ventricle (upper panel). The tricuspid regurgitation (TR) jet is high velocity—nearly 4 m/s—predicting a right ventricular pressure >70 mm Hg (lower panel).

B. Cardiovascular profile score

1. The cardiovascular profile score is 8/10.

2. Points were deducted for decreased RV function and holosystolic tricuspid regurgitation.

3. The arterial and venous Doppler flow patterns were normal.

C. Associated extracardiac findings

None.

D. Fetal management and counseling

1. Amniocentesis should be offered, although chromosomal anomalies are unlikely with pulmonary atresia with intact ventricular septum.

2. Follow-up includes serial antenatal studies at 4-week intervals.

a. Assess RV size and function and endocardial fibroelastosis.

b. Look for congestive heart failure (CHF), which can develop if there is:

    (1) Significant tricuspid regurgitation creating RA enlargement.

    (2) Restriction of the foramen ovale, which would compromise systemic venous return.

c. Assess LV function.

    (1) LV function may be compromised with significant volume loading or diastolic pathology of the right heart.

    (2) LV dysfunction can occur after birth if the coronary circulation is RV dependent and the RV is decompressed.

d. Assess the growth of pulmonary arteries and branches. Ductal flow has already been shown to be reverse of normal due to the atretic pulmonary valve.

3. Delivery.

a. Conditions for vaginal delivery.

    (1) The mode of delivery is decided according to the functional condition of the LV. Usually vaginal delivery is possible.

    (2) If the fetus remains well compensated, vaginal delivery should be at term or near term in a tertiary care center.

b. Conditions for cesarean delivery.

    (1) LV dysfunction, such as fractional shortening of less than 25%.

    (2) Evidence of progressive flow restriction through the foramen ovale.

    (3) Fluid accumulation in either the pleural or peritoneal cavities.

c. Cesarean section practice varies with institution preference.

E. Neonatal management

1. Medical.

a. Administer prostaglandin E₁ (PGE₁) infusion to keep the ductus open to increase pulmonary blood flow and raise arterial oxygen saturation.

b. Oxygen administration can increase oxygen saturation by decreasing pulmonary venous regurgitation and increasing blood flow.

c. Therapeutic balloon atrial septostomy should be performed in the rare situation of restrictive patent foramen ovale.

d. Cardiac catheterization and angiography are recommended to demonstrate coronary sinusoids (by RV angiogram) and rule out coronary artery anomalies such as stenosis. In many pediatric cardiac centers, radiofrequency perforation of the RV outflow tract (RVOT) is possible at cardiac catheterization, eliminating the need for surgery when the RV can otherwise sustain sufficient pulmonary circulation.

2. Surgical.

a. Palliative.

    (1) Decisions regarding intervention at cardiac catheterization or surgery for this condition depend on the RV size and the presence or absence of RV sinusoids or coronary artery anomalies.

       (a) If the RV is of adequate size for future growth, a connection is established between the RV and the main pulmonary artery (transannular patch or closed transpulmonary valvotomy) in preparation for a biventricular repair.

       (b) A temporary aortic-to-pulmonary shunt might also be necessary at the same time if the RV is still insufficiently compliant to sustain a normal preload and thus a normal output.

       (c) The surgical mortality for this operation is less than 1%.

    (2) Alternatively, laser wire or radiofrequency-assisted valvotomy plus balloon dilation of the pulmonary annulus has been shown to be effective and safe compared to the previously mentioned approach in selected patients with moderate RV hypoplasia and patent infundibulum. About 60% of the patients achieve biventricular circulation.

    (3) In patients with monopartite RV and coronary sinusoids, a systemic-to-pulmonary shunt without an RV outflow patch is recommended. Decompression of the RV (pulmonary valvotomy or RV outflow patch) can reverse coronary flow into the RV, resulting in a coronary steal from the LV, producing myocardial ischemia.

    (4) Coronary circulation is truly RV dependent with proximal stenosis of the left main coronary artery, the right coronary artery, the left anterior descending artery, or the circumflex artery. Many infants have sinusoids, and in isolation these do not necessarily result in a coronary circulation that requires the RV pressure to remain high.

    (5) Recognition of RV-dependent coronary circulation is necessary for making the best choice in the initial management of an affected infant.

       (a) An infant with an RV-dependent coronary circulation, which is often associated with the most hypoplastic RVs, should have an aortic-to-pulmonary shunt placed in the neonatal period.

       (b) An infant without an RV-dependent coronary circulation may undergo an intervention to decompress the RV.

b. Corrective.

    (1) In some patients, radiofrequency perforation of the pulmonary valve with dilation or placement of an RVOT patch to enlarge the RVOT results in normal or near-normal circulation, provided the RV is sufficiently large to provide pulmonary blood flow (with or without closure of the atrial-level shunt).

    (2) In patients with smaller right ventricles, an initial radiofrequency perforation of the RVOT with subsequent placement of an aortic- to-pulmonary or Blalock–Taussig shunt can buy time to ultimately allow later repair.

    (3) When there is sufficient growth of the RV, the Blalock–Taussig shunt could be closed at cardiac catheterization or surgery. In the cardiac catheterization laboratory, balloon occlusion of the atrioseptal defect (ASD) and even the Blalock–Taussig shunt may be performed initially to be certain that the RV output is sufficient to sustain normal pulmonary circulation and that the central venous pressures do not increase significantly.

    (4) Occasionally, the RV is not sufficient to ever sustain the full pulmonary output but is sufficient to sustain at least half of the output. In such a state, the infant may have a right bidirectional Glenn shunt placed, with takedown of the Blalock–Taussig shunt and ASD closure or fenestration, known as the ventricle-and-a-half repair. Mortality for this procedure is 5%. This might be a better solution for a borderline RV.

    (5) If the RV is too small for the ventricle-and-a-half palliation or there is an RV-dependent coronary circulation, a Fontan procedure may be necessary at 2 to 5 years of age, following assessment at cardiac catheterization. Mortality for this procedure is 5% to 7%.

    (6) Transplantation might also be considered in a neonate with RV-dependent coronary artery perfusion. The coronary stenosis can lead to an increased risk of sudden death.

F. Follow-up

None of the surgical procedures is curative.

1. Patients who had a Fontan operation.

a. Arrhythmia, reduced heart function, and neurodevelopmental problems are possible sequelae.

b. Women who have undergone the Fontan procedure can become pregnant.

c. Transplantation is a possibility in young adult life if LV dysfunction develops.

2. For patients who had RVOT reconstruction and two-ventricle repair, surgery might be necessary for recurrent RV outflow obstruction or conduit replacement.

G. Risk of recurrence

1. When there is a previous baby with the same condition, this rare congenital heart defect may be an autosomal recessive trait.

2. In the absence of positive family history and normal karyotype, including FISH for 22q11.2, we assume a multifactorial inheritance, and hence the estimated recurrence risk is around 2%.

H. Outcome of this case

1. The baby was born at term with good Apgar scores and good weight.

2. Moderate cyanosis was noted at birth (pulse oximeter reading was 76%-82%).

3. Prostaglandin E₁ (PGE₁) infusion was started.

4. Postnatal echocardiography confirmed the diagnosis of pulmonary atresia, moderate tricuspid regurgitation, and intact ventricular septum.

5. The pulmonary arteries were of good size and had confluent pulmonary artery branches.

6. The foramen ovale and ductus arteriosus were patent and good sized, with left-to-right shunting.

7. There was retrograde flow in the left anterior descending artery and the left main coronary artery, and there was evidence of a proximal left main coronary artery stenosis.

8. Cardiac catheterization confirmed the presence of RV-dependant coronary circulation. The presence of RV-dependant coronary circulation made a univentricular repair the only surgical option.

9. The infant had a palliative A-P shunt at day 5 of postnatal life.

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