Ebstein Anomaly

Introduction
Background

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.
Pathophysiology

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.

Frequency
United States

True prevalence is unknown because mild forms frequently are undiagnosed. Currently, with wide application of echocardiography, more cases are being diagnosed. Ebstein anomaly probably accounts for 0.5% of cases of congenital heart diseases.
Mortality/Morbidity

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.2,3
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.

Race

Ebstein anomaly is more common in children of white females.
Sex

No specific sex predominance exists.
Age

Ebstein anomaly can present at various stages of life.
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.
Clinical
History

Patients can have a variety of symptoms related to the anatomical abnormalities of Ebstein anomaly and their hemodynamic effects or associated structural and conduction system disease.

Cyanosis
Fairly common and frequently due to right-to-left shunt at the atrial level and/or severe heart failure
Transient in neonatal life with recurrence in adult life
May appear for the first time in adult life
Transient appearance/worsening of cyanosis in adult life due to paroxysmal arrhythmias
Once apparent, progressively worsens
Fatigue and dyspnea: These are due to poor cardiac output secondary to right ventricular failure and decreased left ventricular ejection fraction.
Palpitations and sudden cardiac death
Due to paroxysmal supraventricular tachycardia (SVT) in as many as one third of patients
Fatal ventricular arrhythmias, which may be due to the presence of accessory pathways
Symptoms of right heart failure: These include ankle edema and ascites.
Other less common presenting symptoms
Brain abscess due to right-to-left shunt
Bacterial endocarditis
Paradoxical embolism, stroke, and transient ischemic attacks
Physical

Physical findings, like the symptoms, span a spectrum from subtle to dramatic.
Cyanosis and clubbing - Varying degrees of cyanosis at various times in life and transient worsening with arrhythmias
Precordial asymmetry
Usually left parasternal prominence and occasionally right parasternal prominence
Absent left parasternal (ie, right ventricular) lift an important negative sign
Jugular venous pulse
May be normal owing to a large, thin-walled right atrium, which can absorb the volume and pressure transmitted from the right ventricle through an incompetent tricuspid valve
Large a and v waves late in the course of the disease, with development of right heart failure
Arterial pulses
Usually normal
Diminished volume late in the course of the disease due to severe right heart failure and decreased left ventricular stroke volume
Heart sounds
First heart sound is widely split with loud tricuspid component secondary to delayed closure of the elongated anterior tricuspid leaflet, which has an increased excursion. Mitral component may be soft or absent in the presence of prolonged PR interval.
Second heart sound usually is normal but may be widely split when the pulmonary component is delayed due to right bundle-branch block (RBBB).
Additional heart sounds and murmurs
Third and fourth heart sounds are commonly present, even in the absence of congestive heart failure (CHF). Summation of third and fourth heart sounds, especially with prolonged PR interval, can mimic an early diastolic murmur.
The holosystolic murmur of tricuspid regurgitation is heard maximally at the lower left parasternal area and sometimes at the apex owing to the displaced location of the tricuspid valve; murmur intensity and duration increase during inspiration.
Causes
Ebstein anomaly is a congenital disease of often uncertain cause.
Environmental factors4 implicated in etiology include the following:
Maternal ingestion of lithium in first trimester of pregnancy
Maternal benzodiazepine use
Maternal exposure to varnishing substances
Maternal history of previous fetal loss
Risk is higher in whites than in other races.

http://emedicine.medscape.com/article/154447-overview