Ebstein Anomaly

Ebstein anomaly is a congenital malformation of the heart that is characterized by apical displacement of the septal and posterior tricuspid valve leaflets, leading to atrialization of the right ventricle with a variable degree of malformation and displacement of the anterior leaflet.

Wilhelm Ebstein first described a patient with cardiac defects typical of Ebstein anomaly in 1866. In 1927, Alfred Arnstein suggested the name Ebstein's anomaly for these defects. In 1937, Yates and Shapiro described the first case of the anomaly with associated radiographic and electrocardiographic data.

The embryological development of tricuspid valve leaflets and chordae involves undermining of the right ventricular free wall. This process continues to the level of the atrioventricular (AV) junction. In Ebstein anomaly, this process of undermining is incomplete and falls short of reaching the level of the AV junction. In addition, the apical portions of the valve tissue, which normally undergo resorption, fail to resorb completely. This results in distortion and displacement of the tricuspid valve leaflets, and a part of the right ventricle becomes atrialized. In one study involving 50 hearts with the anomaly, the entire right ventricle was found to be morphologically abnormal. ^[1]

Ebstein anomaly is commonly associated with other congenital, structural, or conduction system disease, including intracardiac shunts, valvular lesions, and accessory conduction pathways (eg, Wolff-Parkinson-White [WPW] syndrome).

The hemodynamic consequences of Ebstein anomaly result from displaced and malformed tricuspid leaflets and atrialization of the right ventricle. The leaflet anomaly leads to tricuspid regurgitation. The severity of regurgitation depends on the extent of leaflet displacement, ranging from mild regurgitation with minimally displaced tricuspid leaflets to severe regurgitation with extreme displacement.

The atrialized portion of the right ventricle, although anatomically part of the right atrium, contracts and relaxes with the right ventricle. This discordant contraction leads to stagnation of blood in the right atrium. During ventricular systole, the atrialized part of the right ventricle contracts with the rest of the right ventricle, which causes a backward flow of blood into the right atrium, accentuating the effects of tricuspid regurgitation.

Ebstein anomaly is a congenital disease of often uncertain cause.

Environmental factors implicated in etiology include the following maternal factors ^[2] :

• Maternal ingestion of lithium in first trimester of pregnancy

• Maternal benzodiazepine use

• Maternal exposure to varnishing substances

• Maternal history of previous fetal loss

The risk of having Ebstein anomaly is higher in white persons than in other races.

Ebstein anomaly probably accounts for 0.5% of cases of congenital heart diseases. Its true prevalence is unknown because mild forms frequently are undiagnosed. With the wide application of echocardiography, more cases are being diagnosed.

Race-, sex-, and age-related demographics

Ebstein anomaly is more common in children of white females. However, no specific sex predominance exists.

Ebstein anomaly can present at various stages of life, as follows:

• Fetal life: Ebstein anomaly is usually diagnosed incidentally by echocardiography.

• Neonatal life and infancy: Ebstein anomaly presents with cyanosis and/or severe heart failure; typically, symptoms present in infancy improve as pulmonary vascular resistance decreases.

• Adult life: Ebstein anomaly presents with fatigue, exertional dyspnea, cyanosis, tricuspid regurgitation and/or right heart failure, and palpitations; arrhythmias are common.

Prognosis depends on the severity of the disease and treatment options available. Pregnancy in women with Ebstein anomaly seems to be well tolerated with adequate supervision. ^{[3, 4]}

Poor prognostic signs include the following:

• Male sex

• Earlier age at presentation ^[5]

• Cardiothoracic ratio of more than 0.65 on chest radiographs

• Septal leaflet attachment ratio (ie, ratio of distance between AV ring and distal attachment of septal leaflet to length of septal leaflet) of more than 0.45

• Increasing ratio of combined area of right atrium and atrialized right ventricle to that of the functional right ventricle—grade 1, which is less than 0.5, to grade 4, which is more than 1.5 (increase in the relative risk of 2.7 for each increment in the grade)

• New York Heart Association (NYHA) class: This has been linked with mortality rate in some studies ^[6]

Morbidity/mortality

The natural course of the disease varies according to the severity of tricuspid valve displacement. Patients presenting in infancy generally have severe disease and unfavorable prognosis. ^{[7, 8]}

The mean age of presentation is in the middle teenage years. According to older observational data, approximately 5% of these patients survive beyond age 50 years. The oldest recorded patient lived to age 85 years.

Complications

Complications of Ebstein anomaly include the following:

• Congestive heart failure

• Sudden cardiac death

• Bacterial endocarditis

• Brain abscess

• Paradoxical embolism

• Transient ischemic attacks

• Stroke