Ebstein anomaly

Ebstein anomaly is an uncommon congenital cardiac anomaly, characterised by a variable developmental anomaly of the tricuspid valve.

The anomaly accounts for only ~0.5% of congenital cardiac defects 6-7, although it is the most common cause of congenital tricuspid regurgitation. There is no recognised gender predilection, and almost all cases seem to be sporadic, although an association with maternal lithium carbonate injection has been postulated 6. A few familial cases have been reported 6-7.

The presentation is often antenatal, with the development of hydrops fetalis and fetal tachyarrhythmias 6. In less severe cases, it may present at birth. Depending on the degree of atrial right-to-left shunting, the infant may or may not be cyanotic.

The main abnormality is an abnormal tricuspid valve (particularly septal and posterior leaflets), which is displaced apically into the right ventricle, resulting in atrialisation of the parts of the ventricle above the valve. This results from the tricuspid valve leaflets inadequately separating from each other, or from the chorda tendinae from the inferior portion of the ventricle, during embryologic development. There can be concurrent tricuspid regurgitation with or without stenosis.

Associations
Plain radiograph

Findings on chest radiographs largely depend on the severity of the abnormality and the degree to which the tricuspid valve is displaced downwards.

There is often severe right-sided cardiomegaly due to an elongated and enlarged right atrium which may result in an elevated apex. Classically, the heart is described as having a "box shape" on a frontal chest radiograph. 

Echocardiography/ultrasound 

Typically shows right heart enlargement. Colour Doppler may show tricuspid regurgitation, an abnormally downward displaced tricuspid valve, and a small right ventricle. May also show evidence of concomitant tricuspid valve regurgitation.

CT/MRI

Allows direct visualisation of anatomical detail. Cine MRI can be used akin to echocardiography for functional assessment. 

  • apical displacement of the septal and posterior leaflets of the tricuspid valve
    • as a rule of thumb: if the tricuspid septal attachment lies more than 1.5 cm "beneath" (i.e. towards the apex) than mitral septal attachment, this can be considered Ebstein anomaly (in adults, the measurement is 2 cm)
    • some prefer a value indexed to body surface area
      • a septal displacement below the mitral valve of >8 mm/m2 (or >0.8 mm/cm2) is the cutoff value 9 for Ebstein anomaly
  • "atrialisation" of the right ventricle
  • tricuspid regurgitation

If you find Ebstein anomaly, also look for other associated defects: RVOT abnormalities, ASD (especially ostium secundum type), VSD and tetralogy of Fallot.

In your report, mention the position of tricuspid valve leaflets, assess the degree of regurgitation, and measure right ventricular volume and function. Be sure that you quote "true" RV volume (volume of the ventricular side of the tricuspid valve).

As the anomaly is of variable severity, so is the prognosis. Severity is related to the amount of RVOT dysfunction and tricuspid regurgitation. Sudden death from arrhythmia may occur.

Symptomatic cases that present in utero have a poorer prognosis 6-7. Even in initially asymptomatic cases, life expectancy is usually limited to a few decades 7.

Some surgical procedures have been performed with mixed results. Arrhythmias are treated with medications or pacemaker placement.

It is named after Wilhelm Ebstein, a German physician (1836-1912) 4.

The differential on a chest radiograph is extremely broad, particularly since the findings in Ebstein anomaly are so variable. With echocardiography and MRI, the diagnosis is usually self-evident, once the apically displaced tricuspid valve in identified.

Differential on a chest radiograph includes:

Congenital heart disease

There is more than one way to present the variety of congenital heart diseases. Whichever way they are categorised, it is helpful to have a working understanding of normal and fetal circulation, as well as an understanding of the segmental approach to imaging in congenital heart disease.

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Article Information

rID: 7365
Section: Pathology
Synonyms or Alternate Spellings:
  • Ebstein's anomaly

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Cases and Figures

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     Case 5: on x-ray
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    Case 5: on MRI
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    Case 6: with a box-shaped heart
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    Case 7: adult
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