Right Atrial Isomerism

Published on 07/06/2015 by admin

Filed under Neonatal - Perinatal Medicine

Last modified 07/06/2015

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21 Right Atrial Isomerism

I. CASE

A 22-year-old white woman, gravida 4, para 2, abortus 1, was referred at 24 weeks’ gestation by the obstetrician for an abnormal four-chamber view and discrepancy in the position of the stomach and heart. There is a positive family history of two maternal uncles who died in the neonatal period of complex congenital heart disease and anal atresia.

A. Fetal echocardiography findings

1. Imaging of the inferior vena cava (IVC) and aorta shows the two vessels running together on the left side of the spine (right atrial isomerism [RAI]) (Fig. 21-1).

2. The liver is midline, and the stomach is on the right and posterior.

3. The heart is in the left chest with a left aortic arch, a normal cardiac axis, and a normal size (cardiothoracic ratio = 0.34). The heart rate is 154 bpm.

4. The four-chamber view shows significant disproportion, with an unbalanced atrioventricular (AV) canal. There is a significantly large right-sided morphologic right ventricle (RV).

5. There is mild holosystolic common AV valve regurgitation.

6. The outflow assessment reveals normally related great arteries but with asymmetry (aorta–to–pulmonary artery diameter ratio = 1.1:0.6), and both arise from the RV.

7. No forward flow can be demonstrated by color or pulsed Doppler through the pulmonary outflow and main pulmonary artery. There are small confluent branch pulmonary arteries.

8. The aortic annulus is increased in size, and there is normal blood velocity by Doppler through it (1.2 m/s).

9. The ductal arch is tortuous and small and has retrograde flow (filling the pulmonary artery) (Fig. 21-2).

10. There is a large atrial septal defect (ASD) creating a common atrium, with a strand of muscle extending from anterior to posterior.

11. The pulmonary venous connection is to a posterior confluence and then to a descending vein coursing to the liver, where it is obstructed (abnormal venous flow pattern) before draining into the IVC.

12. There are bilateral superior venae cavae (SVC) to the respective atria and no coronary sinus (Fig. 21-3).

13. The RV Tei index (myocardial performance index) is normal, with good ventricular function and no signs of heart failure.

F. Neonatal managment

1. Medical.

a. PGE1 infusion should be started to keep the ductus open to increase pulmonary blood flow and raise arterial oxygen saturation to greater than 70%. If saturation does not increase, then repair of a total anomalous pulmonary venous connection (TAPVC) may be indicated.

b. Administration of oxygen can increase oxygen saturation by decreasing pulmonary vascular resistance (PVR) and by increasing blood flow.

c. Intubation and mechanical ventilation for progressive cyanosis might be needed.

d. With hypotension, volume and inotropic support are indicated to improve ventricular function.

e. Antibiotics: Asplenic patients should receive amoxicillin orally once per day at dose of 20 mg/kg body weight.

f. Immunizations.

2. Surgical.

a. Palliative.

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