13 Double-Outlet Right Ventricle

Rima S. Bader

I. CASE

A 21-year-old white woman, gravida 2, para 0+1, was referred at 23 weeks’ gestation for an abnormal anomaly scan with a two-vessel umbilical cord. The scan had been performed because of an abnormal serum screen.

A. Fetal echocardiography findinges

1. The fetal echo reveals situs solitus of the atria, levocardia, left aortic arch, heart rate of 132 bpm, normal cardiac axis and position, and mild cardiomegaly (cardiothoracic ratio = 0.38).

2. The four-chamber view is abnormal, with a small posterior left ventricle.

3. The outflow assessment reveals transposition of the great arteries (TGA) (aorta anterior and to the right of the pulmonary artery), mild asymmetry and the aorta slightly smaller than the pulmonary artery (Fig. 13-1).

4. The aortic valve is bicuspid, and the annulus is a normal size for gestation. The valve domes mildly in systole, with moderate flow acceleration through it by Doppler (1.5 m/s).

5. The main pulmonary artery is a good size and has confluent branch pulmonary arteries with normal Doppler velocity through them.

6. The aortic arch is leftward; however, the aortic arch is smaller than the ductal arch. Both arches have antegrade flow.

7. There is a large perimembranous ventricular septal defect (VSD) with outlet extension.

8. There is straddling of the mitral valve.

9. Flow through the foramen ovale is unrestricted, with a bidirectional shunt.

10. The pulmonary venous flow pattern and drainage are normal.

11. The Tei index (myocardial performance index) is normal in both ventricles.

Fig. 13-1 These images demonstrate the findings in a fetus with Taussig–Bing double-outlet right ventricle. A, The four-chamber view is not so abnormal. However, the outflow tract pathology can be seen sweeping toward the outlets, which demonstrate parallel relationship of the great arteries and a mildly smaller aorta (a), suggesting the potential for aortic coarctation. The main pulmonary artery (p) overrides the muscular septum as a consequence of the presence of anterior malalignment of the conal septum, which impinges on flow to the aorta in fetal development. LV, left ventricle; RV, right ventricle. B, Three-vessel view of the great arteries, with an anterior and rightward aorta, more rightward and posterior superior vena cava (s), and posterior pulmonary artery (p), which is significantly larger than the aorta (a). L, left; R, right.

B. Cardiovascular profile score

1. The cardiovascular profile score is 9 /10.

2. One point was deducted for mild cardiomegaly.

C. Associated syndromes and extracardiac anomalies

1. Abnormal maternal serum screen.

2. Two-vessel umbilical cord.

3. Overriding of fingers and rocker-bottom feet.

D. Fetal management and counseling

1. Management: Diagnosis of any form of double-outlet right ventricle (DORV) should prompt referral for the following:

a. Thorough anatomic examination by ultrasound.

b. Amniocentesis.

    (1) Karyotyping for DiGeorge’s syndrome.

    (2) Chromosomal anomaly (including trisomies) screening, including fluorescent in situ hybridization (FISH) screen for chromosome 22q11 microdeletion.

c. In this case, the abnormal maternal serum screen is an additional reason to ask for amniocentesis.

2. Follow-up includes serial antenatal studies at 4- to 6-week intervals.

a. Pulmonary and aortic outflow obstruction (bilateral outflow tract obstruction) is possible, with progressive hypoplasia of the aortic valve, ascending aorta, and arch and evolving coarctation of the aorta.

b. Check the size of the VSD (might become restrictive).

c. Monitor the direction of ductal flow.

d. Monitor ventricular size and function using the biventricular Tei index.

e. Watch for development of hydrops fetalis. It is unlikely unless there is biventricular dysfunction or significant atrioventricular (AV) valve or semilunar valve regurgitation.

f. Watch for development of rhythm disturbance.

E. Delivery

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

F. Neonatal management

1. Medical.

a. If there is progressive arch hypoplasia with or without aortic outflow obstruction, initiation of prostaglandin E₁ (PGE₁) infusion should be considered to keep the ductus open at least until a postnatal echocardiogram confirms or excludes important outflow tract and arch pathology.

b. In addition, given the potential for transposition physiology and streaming, PGE₁ may be necessary until an atrial septostomy is performed to improve atrial and ventricular level mixing.

c. Administration of oxygen can increase oxygen saturation by decreasing pulmonary valve regurgitation and increasing blood flow.

d. At times, volume and inotropic support may be indicated to improve ventricular function and atrial level mixing.

2. Surgical: In this case, given the presence of a straddling mitral valve, single ventricle palliation is most likely in order.

a. Stage 1.

    (1) If there is arch hypoplasia with or without aortic outflow obstruction, the infant requires a Norwood procedure in the neonatal period. (See the description of the Norwood procedure in Chapter 15.)

    (2) If there is no significant aortic or pulmonary outflow tract obstruction or arch obstruction, pulmonary artery banding may be the first stage with atrial septostomy or septectomy.

b. Stage 2 is a bidirectional Glenn shunt at 4 to 6 months, following diagnostic cardiac catheterization.

c. Stage 3 is a modified Fontan procedure at 2 to 5 years of age.

G. Follow-up

1. Follow-up is as discussed previously in the outcome of the Norwood procedure and single ventricle palliation in Chapter 15.

2. Unique to the present situation is the potential for bilateral outflow tract obstruction, which could add to the risk of a Fontan procedure.

H. Risk of recurrence

1. For isolated DORV, the risk is approximately 1.5% to 2%.

2. If aneuploidy is present (e.g., trisomy 18), the recurrence risk is low.

I. Outcome of this case

1. Amniocentesis showed a chromosomal abnormality (trisomy 18).

2. The mother decided to terminate the pregnancy after consulting with the genetic counselor.

II. YOUR HANDY REFERENCE

A. Prevalence

1. DORV accounts for less than 1% of all congenital heart disease.

2. Allan and Sharland (1992) studied a total group of 2136 fetuses with heart diseases diagnosed prenatally. These included 62 (3%) cases of DORV.

a. Mortality.

    (1) Pregnancy was terminated in 34.

    (2) Spontaneous intrauterine death occurred in two.

    (3) There were five neonatal deaths and four infant deaths.

b. Survival: 17 babies survived (61% survival rate of continuing pregnancies).

3. In fetal life, DORV in the absence of ventricular hypoplasia is one of the less commonly identified lesions in utero. As in TGA, the four-chamber view may be normal, and most of these lesions go undetected at the time of obstetric ultrasound examination.

B. Outcome

The postnatal outcome in infants with DORV depends on:

1. The complexity of the cardiac lesion.

2. The size of the ventricles.

3. The anatomy of the AV valves.

4. The position, size, and number of the VSD(s).

5. The anatomical relationships of the great arteries.

6. The presence of outflow obstruction.

C. Associated syndromes and extracardiac anomalies

1. DORV can be associated with chromosomal abnormalities and is present in 12% of cases in one fetal series.

2. The tetralogy of Fallot (TOF) type of DORV may be associated with trisomies 13, 18, and 21 as well as with microdeletion of chromosome 22 (velocardiofacial or DiGeorge’s syndrome).

3. The TGA type of DORV has a lower risk of chromosomal abnormalities.

4. DORV associated with mitral atresia and normally related great arteries can be seen in trisomies 18 and 13.

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