SECTION IX - EBSTEIN ANOMALY

Part I - Background Information

Ebstein anomaly is rare. The term encompasses a wide spectrum of anatomic and functional abnormalities of the morphological tricuspid valve (TV) which have certain features in common:

• Apical displacement of the septal and postero-lateral leaflets of the TV below the atrioventricular junction into the right ventricle.
• Resultant 'atrialization' of the inflow of the right ventricle to varying degrees and consequently a smaller 'functional' right ventricle.
• Varying degrees of tricuspid regurgitation (exceptionally, the tricuspid valve is stenotic).
• Enlargement of the right atrium.
• A shunt at atrial level, either PFO or secundum ASD, in approximately 50%.
• One or more accessory conduction pathways, increasing the risk of atrial tachycardias, in 25% of cases.
• Varying degrees of anatomical and physiological right ventricular inflow or outflow tract obstruction.
• Varying impairment of left ventricular function (113-115).
• Varying degrees of cyanosis (less than half the patients).

Associated lesions may include:

• VSD.
• PS.
• Occasionally others, such as aortic coarctation or mitral valve prolapse.

 
Part II - History and Management of Unoperated Patients

Patients with mild Ebstein anomaly may be asymptomatic with no functional limitation. Survival to the ninth decade has been reported. Patients with moderate Ebstein anomaly may become symptomatic during late adolescence or young adult life. Patients with severe Ebstein usually present at birth or even in utero.

The most common symptoms in adults are exercise intolerance (dyspnea and fatigue) and symptomatic supraventricular arrhythmias. Heart block occasionally occurs.

When an atrial defect is present, patients may be cyanotic (to a varying degree - particularly on exercise), and are at risk of a paradoxical embolus resulting in TIA/stroke. Alternatively, they may have a left-to-right shunt at rest, which can reverse on effort.

End-stage disease with severe tricuspid regurgitation and right ventricular dysfunction may manifest as right-sided cardiac failure. It is usually precipitated by an arrhythmia such as atrial flutter or fibrillation. Sudden death (presumed arrhythmic in nature) may occur at any age, and is more likely if accessory pathway(s) is/are present (116-122).

 
Part III - Diagnostic Work-up

An adequate diagnostic workup:

• Documents the anatomic severity (degree of apical displacement of the tricuspid valve) with resultant degree of right-sided enlargement, RV dysfunction and degree of tricuspid regurgitation.
• Determines whether the TV has the potential for surgical repair. This depends on the degree of anterior leaflet size and degree of tethering as well as the relative size of the 'functional' RV.
• Documents the presence or absence of an atrial communication and whether there is right-to-left shunting.
• Determines the presence or absence of associated lesions.
• Measures left ventricular function and identifies any mitral valve abnormalities.
• Defines, if possible, the presence or absence of an accessory pathway.
• Determines the amount of functional limitation, if any.

The initial workup should include at a minimum:

• A thorough clinical assessment.
• ECG.
• Chest x-ray.
• Echo Doppler evaluation by an appropriately trained individual.
• Oximetry.

The diagnostic workup may require:

• Exercise test.
• TEE Doppler examination if the anatomic information is not provided by TTE.
• Holter monitor.
• An electrophysiological study if there is a history or ECG evidence of arrhythmias or accessory pathway(s).
• Coronary angiography in patients at risk of coronary artery disease or in patients over the age of 40 years if surgical repair is planned.

 
Part IV - Indications for Intervention

The following situations warrant intervention: Deteriorating exercise capacity (NYHA class > II). Increasing heart size (CTR > 60%). Important cyanosis (resting oxygen saturation < 90%). Severe tricuspid regurgitation with symptoms. A TIA or stroke. Sustained atrial flutter or fibrillation. Atrial arrhythmias secondary to an accessory pathway.
Grade: C	Level: V	Refs: 123,124

 
Part V - Interventional Options

Ebstein anomaly should only be repaired by congenital heart surgeons, ideally with substantial specific experience in this operation. Every effort should be made to preserve the native tricuspid valve.
Grade: C	Level: V	Refs: 125-129

When the anterior TV leaflet is mobile and can serve as a monocusp valve, and the functional RV is of adequate size (>1/3 of the total RV), valve repair may be possible and is preferable to valve replacement (130).

If the TV is not repairable, valve replacement will be necessary.

An atrial communication, if present, should be closed.

Given normal PA pressures, in patients with an inadequate RV (because of size or function), severe tricuspid regurgitation and chronic supraventricular arrhythmias, a bi-directional cavopulmonary connection may be used to supplement the intracardiac repair.

Occasionally a Fontan operation may be the best option in patients with tricuspid stenosis and/or hypoplastic RV.

It is controversial whether the atrialized portion of the right ventricle should be plicated to improve hemodynamics and reduce the risk of atrial arrhythmias. Radiofrequency or operative cryoablation have been successful in preventing atrial flutter. A maze procedure including pulmonary vein encirclement may be helpful to prevent and treat atrial fibrillation.

 
Part VI - Interventional Outcomes

With satisfactory valve repair, with or without bi-directional cavopulmonary connection, medium term prognosis is excellent. Late arrhythmias, most commonly atrial tachyarrhythmias and seldom complete atrioventricular block, may occur (131,132).

Valve re-replacement may be necessary because of a failing bioprosthesis or thrombosed mechanical valve. There is a high incidence of complete heart block with tricuspid valve re-replacement.

 
Part VII - Arrhythmias

In patients with chronic supraventricular arrhythmias (atrial fibrillation/flutter), concomitant cryoablation and/or right atrial maze procedure at the time of surgery may be considered (128). Radiofrequency ablation is less successful because of the commonly very large right atrium.

If an accessory pathway is present, this should be mapped and can be obliterated either at the time of surgical repair or pre-operatively in the catheter laboratory (133). However, multiple pathways are common and pre-operative ablation may prove difficult.

 
Part VIII - Pregnancy

In the absence of maternal cyanosis, right-sided heart failure or arrhythmias, pregnancy is usually well tolerated (134,135).

 
Part IX - Follow Up

All Ebstein patients should have regular follow-up with an ACHD cardiologist. Particular attention should be paid to: Cyanotic patients. Substantial cardiomegaly (CT ratio > 60%). Right-sided ventricular function which may worsen and cause congestion. Tricuspid regurgitation or tricuspid stenosis in the previously operated patient. Degeneration/infection of a bioprosthetic valve or thrombosis/infection of the mechanical valve. Recurrent atrial arrhythmias. Ventricular arrhythmias. Complete heart block. Endocarditis prophylaxis is recommended for 6 months following Ebstein repair or for life if any residual gradient/lesions persist or in the presence of prosthetic valve.

Grade: Consensus