Case No. :	27
Month :	March
Year :	2001
Contributor :	Dr. Arpit Nagar

Case Report | Discussion

Case report:

A 20 yr-old-lady with 24 weeks' amenorrhea presented for a routine antenatal ultrasound examination . She had no obstetric complaints or bad obstetric history .On gray scale ultrasound examination, the right atrium of the fetus was found to be enlarged with right ventricular outflow tract obstruction . The right ventricle was not well seen. On colour Doppler examination there was presence of tricuspid regurgitation and the tricuspid valve was displaced caudally into the right ventricle . The rest of the cardiac chambers were normal . There was no evidence of right to left shunt. The rest of the obstetrical parameters were normal . There was no evidence of hydrops . An antenatal diagnosis of Ebstein's anomaly was made . The lady is yet to deliver.

Fig 1			Fig 2
Note inferior displacement of the tricuspid valve. Hypoplasia of the right ventricle is also seen.

Fig 3	Fig 4
Note the tricuspid regurgitation .

Discussion:

Ebstein's anomaly of the heart is an uncommon congenital cardiac anomaly characterised by atrialization of the right ventricle with inferior displacement of the tricuspid valve( Figure 1 and 2). The septal and posterior leaflets of the tricuspid valve are fused to the walls of the right ventricle . There is hypoplasia of the right ventricle ( Figure 1). It forms 7% of all cardiac anomalies and 0.5-1% of all the fetal anomalies . The most specific teratogen to cause this condition is maternal lithium exposure . This condition is usually associated with pulmonary stenosis , pulmonary atresia , a right to left shunt via the foramen ovale. The patient may present at any age . Imaging modalities include radiographs of the chest , 2D Echo , Colour Doppler . Plain filmy findings include a prominent right heart shadow , cardiomegaly ( characteristic box shaped heart) and pulmonary oligemia .Although the main pulmonary artery is enlarged it is masked by the cardiomegaly on the chest radiograph. On 2D Echo the apical 4 chamber view is the view of choice. It shows the enlargement of the right atrium with hypoplasia of the right ventricle . The septal and the posterior leaflets of the tricuspid valve are adherent . Right ventricular outflow tract obstruction viz. pulmonary stenosis /atresia can be demonstrated. The presence of a right to left shunt via the foramen of ovale is confirmed on 2D Echo . Colour Doppler is helpful in showing the presence of tricuspid regurgitation and the right to left shunt ( Note the tricuspid regurgitation as seen in Figure 3 and Figure 4). One characteristic finding on 2D Echo on the M-mode is the elongation of interval between the q wave and the tricuspid valve closure. On antenatal obstetric US examination the diagnosis of Ebstein's is to be strongly suspected in all cases of right atrial enlargement with a hypoplastic right ventricle. The differential diagnosis of Ebstein's anomaly include the Uhl's anomaly , idiopathic dilated right atrium and tricuspid valve dysplasia . Uhl's anomaly ( parchment right ventricle ) is similar to Ebstein's anomaly but the right ventricle is extremely thin with imperceptible walls and the walls cannot be differentiated from the pericardium besides the main difference of a normal tricuspid valve. Surgery is indicated in cases of severe cyanosis ( Glenn's procedure - anastamosis of the superior vena cava with the right pulmonary artery).