First described by Wilhelm Ebstein in 1866, Ebstein's anomaly is a congenital malformation of the heart, characterised by apical displacement of the septal and posterior tricuspid valve leaflets, leading to part of the right ventricle becoming part of the right atrium, with a variable degree of malformation and displacement of the anterior leaflet.

Epidemiology

• Accounts for less than 1% of cases of congenital heart diseases.¹
• True prevalence is unknown because mild forms often remain undiagnosed.

Risk factors

• Environmental factors implicated in aetiology include maternal ingestion of lithium or benzodiazepine and maternal history of miscarriage.²
• Increased incidence in Caucasians.

Presentation

• Ebstein's anomaly presents with a spectrum of congenital abnormalities of the tricuspid valve and the right ventricle.³
• The abnormality of the tricuspid valve leads to tricuspid regurgitation. The degree of tricuspid regurgitation is variable, ranging from mild to severe regurgitation.
• Presentation is often between the ages of 10 and 30 years but can present at various stages of life:
  • Fetal life: diagnosed incidentally by echocardiography.
  • Neonatal life and infancy: presents with cyanosis and/or severe heart failure. Symptoms presenting in infancy often improve as the pulmonary vascular resistance decreases.
  • Adult life: fatigue, exertional dyspnoea, cyanosis, tricuspid regurgitation and/or right heart failure and palpitations (arrhythmias are common).

Symptoms

• Cyanosis: common and often due to either associated atrial right-to-left shunt and/or severe heart failure. Cyanosis is often transient in neonatal life with recurrence in adult life, but may appear for the first time in adult life. In adult life, cyanosis progressively worsens and may be transiently increased due to paroxysmal arrhythmias.
• Fatigue and dyspnoea: due to right ventricular failure and decreased left ventricular ejection fraction.
• Palpitations and sudden cardiac death: due to paroxysmal supraventricular tachycardia or fatal ventricular arrhythmias.

Signs

• Signs are variable depending on the extent of the anomaly.
• Cyanosis and clubbing: variable degrees of cyanosis, and transient worsening with arrhythmias.
• Precordial asymmetry: usually left parasternal prominence and occasionally right parasternal prominence.
• Jugular venous pressure (JVP): may be normal due to a large, thin-walled right atrium, which can absorb the volume and pressure transmitted from the right ventricle through an incompetent tricuspid valve.
• Signs of right heart failure: ankle oedema, hepatomegaly and ascites. Large A and V waves in the JVP.
• Heart sounds: first heart sound is widely split with a loud tricuspid component. Second sound is usually normal but may be widely split. Third and fourth heart sounds are often present, even in the absence of congestive heart failure.
• The pansystolic murmur of tricuspid regurgitation is best heard at the lower left parasternal area and sometimes at the apex.

Differential diagnosis

• Accessory pathway-mediated Wolff-Parkinson-White (WPW) syndrome and supraventricular tachycardia (SVT).
• Cyanotic congenital heart diseases.
• Tricuspid valve dysplasia and prolapse.
• Arrhythmogenic right ventricular cardiomyopathy.
• Atrial septal defect.
• Cases of severe right heart failure.
• Transposition of the great vessels.

Investigations

• Chest X-ray: may be normal or demonstrate cardiomegaly, decreased pulmonary vasculature, large right atrium.
• ECG: usually normal sinus but may intermittently demonstrate SVT, paroxysmal SVT, atrial flutter, atrial fibrillation or ventricular tachycardia. Abnormal P waves, consistent with right atrial enlargement and the PR interval is often prolonged (but may be normal or short in patients with WPW syndrome). QRS often shows right bundle branch block.⁴
• Echocardiogram: allows definitive diagnosis.
• Cardiac catheterisation: rarely required.
• Electrophysiology studies: can delineate accessory conduction pathways. Right-sided pathways are more common and 50% of patients have multiple pathways.

Management

• Antibiotic prophylaxis for infective endocarditis.
• Management of heart failure.
• Treatment of arrhythmias.

Surgical

• Increasingly the trend is for operative intervention early in the development of heart failure.⁵
• Correction of the underlying tricuspid valve and right ventricular abnormalities.
• Tricuspid valve repair is preferred over valve replacement.⁶
• The atrialised portion of the right ventricle can be resected surgically, and the markedly dilated, thin-walled right atrium can be resected.
• Correction of any associated intra-cardiac defects.
• Associated septal defects may be closed.
• Palliative procedures: are usually reserved for severely ill infants with an otherwise poor prognosis. These include creation of atrial septal defect, closure of tricuspid valve with plication of the right atrium, and maintenance of pulmonary blood flow through an aorto-pulmonary shunt.
• Surgical treatment of associated arrhythmias.
• Heart transplantation is appropriate in selected patients.

Complications

• Right heart failure
• Sudden cardiac death
• Brain abscess due to right-to-left shunt
• Bacterial endocarditis
• Paradoxical embolism (passage of thrombus from venous system to arterial system via a septal heart defect)
• Stroke and transient ischaemic attacks

Prognosis

• The prognosis depends on severity of the anomaly, degree of tricuspid regurgitation, degree of heart failure, associated anatomical defects and associated arrhythmias.⁷
• Patients presenting in infancy generally have severe disease and a poor prognosis.⁸
• However the prognosis for neonatal Ebstein's anomaly has improved with modern surgical techniques.⁹