Ebstein's anomaly - antenatal ultrasound

Case contributed by Imran Ahmad Khan

Presentation

A young primigravida came for a fetal anatomic scan at 18 weeks.

Patient Data

Age: 30 years
Gender: Female

The scan is remarkable for a grossly dilated right atrium of the heart. The tricuspid valve is significantly offset as compared to the mitral valve and is displaced apically.  The valve is thickened and moving abnormally. There is a large tricuspid regurgitation which could be appreciated on color as well as pulsed Doppler examination. There is atrialization of right ventricle and functional right ventricle is small. The left side of the heart is slightly compressed and appears small. There is an associated ASD as well as an ostium secundum VSD. The left ventricular outflow tract is normal and could be seen well. However, the right ventricular outflow tract is hypoplastic and could not be imaged despite best efforts. There is an overall cardiomegaly. However, the lungs at the time of scan showed apparently normal morphology and echogenicity. There is no fetal ascites or pleural effusion and no signs of hydrops.  No other associated congenital anomaly could be identified.

Case Discussion

Ebstein’s anomaly is one of rare congenital cardiac anomalies accounting for around 0.2-0.5 % of all cardiac anomalies 1,2 . The primary anomaly is an abnormal inferior (apical) displacement of the tricuspid valve leaflets, mainly the septal and the posterior leaflets, which leads to significant shortening of the functional right ventricle 2-4. The valve is not only abnormal in position but also abnormal in morphology and is usually thickened and incompetent leading to tricuspid regurgitation and to a lesser extent tricuspid stenosis.  The part of the right ventricle above the anomaly is referred to as atrialized right ventricle. The atrialized right ventricle and the tricuspid annulus are often significantly dilated.  Right atrium is usually hugely dilated.  ASD is almost always present. A number of other associated cardiac defects are also present including pulmonary hypoplasia/ atresia, aortic and mitral valve abnormalities and VSD 2,5.   

The prognosis is poor and fetal hydrops followed by demise usually results in majority of cases 6.  The neonatal chest radiograph shows markedly enlarged box shaped heart. Cyanosis and cardiac failure are usually the presenting features in neonates and infants 7. Older children may present as cardiac murmurs. Few mild cases may remain asymptomatic till adulthood and present as arrythmias 7

Based on the prognosis of the case and being able to detect the anomaly early (18 weeks) medical termination of pregnancy was offered to the mother.  

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