In Ebstein's anomaly, the septal and posterior leaflets of the tricuspid valve are downwardly displaced into the right ventricular cavity, while the anterior leaflet is elongated with abnormal attachments. As a result, the right side of the heart is abnormally partitioned into a right atrium, an atrialized portion of the right ventricle, and a right ventricular cavity. A communication between the left and right atrium is often present. This is known as an atrial septal defect (ASD) or a patent foramen ovale.
These abnormalities typically result in a leak in the tricuspid valve (known as tricuspid regurgitation) and varying degrees of right ventricle enlargement. An ASD may cause mild cyanosis, a situation where blue unoxygenated blood from the right atrium travels across the atrial septum and mixes with oxygenated blood returning from the lungs. In addition, 20% of patients with Ebstein's anomaly have accessory electrical tissue (known as a bypass tract) which can cause episodes of heart racing, a condition known as Wolff-Parkinson-White syndrome (WPW).
Symptoms of Ebstein's anomaly are quite variable and range from the most severe form producing severe congestive heart failure and cyanosis at birth to milder cases that may not be discovered until adulthood. The main determinant in the clinical presentation of Ebstein's anomaly is the degree of tricuspid regurgitation and its effect on right ventricular size and function. Management depends on the patients age, symptoms, and anatomic abnormalities.
Treatment and Management
Surgery is indicated when there is congestive heart failure from a leak in the tricuspid valve. Significant cyanosis may also be an indication for an intervention. The management of adolescents and adults who lack symptoms but have important degrees of tricuspid regurgitation varies amongst centers. Those with considerable experience in the surgical repair of Ebstein's are likely to be more aggressive in recommending surgery than those with less experience.
Surgical repair is complex and encompasses several different approaches for tricuspid valve reconstruction, such as a monocusp valve repair or a Cone operation, as well as tricuspid valve replacement. While valve repair avoids the need for an artificial valve, the adequacy and durability of the repair must be balanced against the reliability of eliminating tricuspid regurgitation following valve replacement. Moreover, the recent development of catheter-based valves extends the time to reoperation for a degenerating bioprosthetic valve by inserting a catheter-valve inside the failing valve and delaying the need for surgical replacement of the tricuspid valve replacement.
Delayed recognition of Ebstein's anomaly until adolescence or adulthood is often associated with the development of a tachyarrhythmia (such as supraventricular tachycardia) or after the discovery of an enlarged heart following a chest x-ray. Such patients should be evaluated at an experienced Adult Congenital Heart Disease center to determine if they should undergo cardiac surgery and to assess arrhythmia treatment options.
Cardiac arrhythmias play an important part in the management of patients with Ebstein's anomaly. There are several different forms of arrhythmias associated with Ebstein's anomaly. In patients with an accessory pathway (known as a bypass tract or WPW), specific types of rhythm abnormalities are seen and include AV reciprocating tachycardia or antidromic tachycardia. In addition, all patients with Ebstein's anomaly are susceptible to the development of atrial tachycardia, atrial flutter, or atrial fibrillation. Although most of these arrhythmias can be successfully treated with catheter ablation, management is more complicated because of the anatomy and should be approached in conjunction with an assessment of the tricuspid valve and right ventricle.
In an occasional patient, the leak in the tricuspid valve is minor but significant blood flow across the atrial septum results in cyanosis during exercise. Some of these patients may be candidates for device closure of the atrial septal defect to eliminate cyanosis from the right to left shunt. However, before embarking on this approach it should be certain that the degree of tricuspid regurgitation is only mild.
Ebstein's anomaly is a complicated lesion, and management of adolescents and adults at an experienced center is advisable. In addition to the abnormalities in the tricuspid valve, right ventricle, atrial septum, and rhythm, it is important to recognize those patients with chronically elevated right atrial pressure who may develop hepatic congestion and hypersplenism.