Ebstein anomaly

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

Epidemiology

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

Associations
  • chromosomal anomalies
  • multiple other congenital heart lesions (ASD is quite common)
  • conduction abnormalities leading to arrhythmia (common), e.g. Wolf-Parkinson-White syndrome
  • maternal lithium carbonate ingestion: possible 

Clinical presentation

The presentation is often antenatal, with the development of hydrops fetalis and fetal tachyarrhythmias . 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.

ECG
  • right atrial enlargement
  • right bundle branch block
    • may be incomplete or complete
  • abnormal PR interval
    • associated with the Wolff-Parkinson-White syndrome
    • alternatively, may demonstrate a prolonged PR interval

Pathology

The main abnormality is an abnormal tricuspid valve (particularly septal and posterior leaflets), which is displaced apically into the right ventricle, resulting in atrialization 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.

Radiographic features

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 

Diagnosis relies on visualization of the septal leaflet of the tricuspid valve, typically appreciated from transthoracic parasternal and apical windows. Apical displacement the septal leaflet in excess of 8 mm per m (body surface area) with “sail-like” elongation is considered diagnostic . Further features include:

  • tricuspid regurgitation
  • degree of right/left ventricular dysfunction
  • right atrial enlargement
  • calculation of the chamber area ratio
    • in the apical 4 chamber view at end-diastole
    • sum of the right atrial and atrialized right ventricular areas divided by the remaining three cardiac chambers
    • values of one or more considered markedly enlarged/severe and portend a poor prognosis
CT/MRI

Allows direct visualization 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/m (or >0.8 mm/cm) is the cutoff value for Ebstein anomaly
  • "atrialization" of the right ventricle
  • tricuspid regurgitation

If you find Ebstein anomaly, also look for other associated defects: right ventricular outflow tract (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).

Treatment and prognosis

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 . Even in initially asymptomatic cases, life expectancy is usually limited to a few decades .

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

History and etymology

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

Differential diagnosis

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: