Ebstein Anomaly: Definition and Clinical Features
Ebstein anomaly is a rare congenital heart defect characterized by apical displacement of the tricuspid valve leaflets into the right ventricle, resulting in atrialization of the right ventricle, varying degrees of tricuspid regurgitation, and right atrial enlargement. 1
Anatomical Features
- Adherence of the tricuspid valve leaflets to the underlying myocardium (failure of delamination) 1
- Apical displacement of the septal and posterior leaflets of the tricuspid valve below the atrioventricular junction in the right ventricle 1
- Atrialization and dilation of the inflow portion of the right ventricle to varying degrees 1
- Redundancy, tethering, and fenestrations of the anterior tricuspid valve leaflet 1
- Varying degrees of tricuspid regurgitation 1
- Enlargement of the right atrium 1
Associated Abnormalities
- More than 50% of patients have a shunt at the atrial level with either a patent foramen ovale or secundum atrial septal defect, resulting in varying degrees of cyanosis 1
- One or more accessory conduction pathways (approximately 25%), increasing the risk of atrial tachycardias 1
- Ventricular septal defects 1
- Varying degrees of right ventricular outflow tract obstruction 1
- Occasionally, other anomalies such as mitral valve prolapse 1
- Abnormalities of left ventricular morphology and function 1
Epidemiology
- Occurs in approximately 0.005% of live births (1 in 20,000) 1, 2
- Accounts for about 0.5-1% of all congenital heart defects 2
- Increased risk with maternal lithium exposure during pregnancy 3
Clinical Presentation
- Varies widely in severity from asymptomatic adults to severely affected neonates 1
- Adults commonly present with:
Diagnostic Evaluation
Physical Examination
- Jugular venous pressure often normal despite severe tricuspid regurgitation due to compliant right atrium 1
- Central cyanosis may be present due to right-to-left shunting 1
- Right ventricular lift is subtle 1
- Auscultation reveals loud first heart sound, possibly systolic clicks, and holosystolic murmur of tricuspid regurgitation at lower left sternal border that increases with inspiration 1
Diagnostic Testing
- Electrocardiogram: Tall peaked P waves ("Himalayan P waves"), QR pattern in lead V1, prolonged and "splintered" QRS with right bundle-branch block pattern 1
- Chest X-ray: May show severe cardiac enlargement with right atrial prominence, "globular" cardiac contour, and clear lung fields 1
- Echocardiography: Primary diagnostic tool to confirm diagnosis 1
- Cardiovascular magnetic resonance (CMR): Useful to determine anatomy, right ventricular dimensions, and systolic function 1
- Transesophageal echocardiography (TEE): Useful for surgical planning when transthoracic images are inadequate 1
- Electrophysiological study: Recommended before surgical intervention, particularly with ventricular preexcitation 1
Follow-up and Monitoring
- All patients with Ebstein anomaly should have regular follow-up in a center for congenital cardiology 1
- Frequency of follow-up depends on disease severity:
Treatment Indications
Surgical repair or reoperation is recommended when one or more of the following are present:
Catheter ablation is recommended for patients with high-risk pathway conduction or multiple accessory pathways 1
Pitfalls and Caveats
- Failure to recognize the diagnosis, especially in milder forms 1
- Late referral in the setting of severe tricuspid regurgitation and right ventricular dysfunction 1
- Underestimation of right ventricular size and function by echocardiography alone; CMR provides more accurate assessment 1
- Pregnancy requires careful evaluation in all Ebstein anomaly patients; cyanotic patients may need surgical correction before pregnancy 4