Ebstein anomaly of the tricuspid valve is a congenital malformation, in which there is downward displacement of insertion of septal and posterior leaflets. Anterior leaflet is not usually affected. The tricuspid valve leaflets are dysplastic. As a result of the displacement, there is poor coaptation of the valve leaflets leading to tricuspid regurgitation, which in turn causes right atrial enlargement of a variable degree depending upon the degree of tricuspid regurgitation.
No single gene defect has been consistently identified with Ebstein anomaly. Ebstein anomaly appears to be genetically heterogeneous, and several candidate genes have been suggested including GATA4, NKX2.5, and hypothetical genes in 1p36. Exposure to lithium during pregnancy has been reported as an etiologic factor.
Ebstein anomaly accounts for 0.3% to 0.6% of all congenital heart defects. No gender preponderance is noted. The majority of cases are sporadic. There is a higher incidence of recurrence in the offspring of women (6%) than that seen the offspring of men (0.6%).
Hemodynamic abnormalities are dependent on the severity of the lesion. Main determinants are a degree of displacement of the tricuspid valve and degree of tricuspid regurgitation. In mild Ebstein anomaly, tricuspid valve function is close to normal. In moderate to severe forms, with each atrial contraction, the blood is propelled into the atrialized RV. With ventricular contraction, blood is forced back into the right atrium. This is even more pronounced in children with significant tricuspid regurgitation. This leads to right atrial dilatation and increased right atrial pressure; the latter results in a right-to-left shunt across ASD/PFO. This results in arterial desaturation and pulmonary oligemia.
There is displacement of the septal and posterior leaflets toward the apex of the right ventricle. The anterior leaflet is usually attached at the annular level and is large and sail-like with multiple attachments to ventricle wall. The portion of RV that is proximal to the level of the displaced septal and posterior leaflets is called the atrialized RV and is usually thin and dysplastic. RV cavity beyond the attachment of the septal and posterior leaflets is the functional RV and is smaller, lacks inlet portion and has a small trabecular portion. The infundibular portion of RV is sometimes obstructed by redundant anterior leaflet or its chordal attachments.
The disorder has a wide spectrum of presentation. Mild cases may not be detected until adulthood. Most severe forms present during the neonatal period. In the fetus, Ebstein anomaly may present as cardiomegaly, tricuspid regurgitation, with right atrial enlargement on fetal echocardiography, arrhythmia or heart failure with hydrops. The fetal presentation is associated with a high incidence of fetal loss. Infants with milder forms are largely asymptomatic. Infants with severe forms become symptomatic and have severe cardiomegaly and may have associated lung hypoplasia. Cyanosis is noted in 50% of the newborn. Children or teens may be detected because of a cardiac murmur or by echocardiography. Supraventricular tachycardia is common, and this is secondary to the accessory pathway or atrioventricular reentry.
In the newborn with mild forms, there may have no cyanosis, but the infant may have multiple cardiac sounds, described as a triple or quadruple rhythm. No significant murmur is heard. In moderate Ebstein anomaly, there may be cyanosis with no significant respiratory distress. In severe cases, hyperdynamic precordium and thrill at the left lower sternal border may be present. The first heart sound is usually normal. The second heart sound may be widely split or be normal.
Chest x-ray reveals severe cardiomegaly in Ebstein anomaly. The increase in the cardiothoracic ratio is due to right atrial enlargement. The lung field is either normal or oligemic. ECG shows right atrial enlargement, low QRS voltages, and right bundle branch block. Right axis deviation is common. Features of WPW syndrome with short PR interval are reported in 30% of Ebstein anomaly patients while 12% have evidence of pre-excitation with normal PR interval. Echocardiography shows the degree of displacement of the tricuspid valve leaflets. The hinge points of the septal and posterior leaflets are usually displaced downward toward the apex. The anterior leaflet usually is not displaced. Apical four chamber view is recommended to estimate the displacement. Mitral valve annulus serves as a reference to quantitate the degree of displacement. The septal leaflet may be dysplastic, fibrotic or absent. Short chordae may attach the septal leaflet to the ventricular septum. Cardiac computed tomography or magnetic resonance imaging is not usually necessary to define and evaluate the anomaly. Cardiac catheterization is usually not necessary, but it is indicated for therapeutic purposes. When catheterization is done, it shows a right to left shunt at the atrial level by oximetry. RA pressure (mean) is usually elevated; A wave is more prominent than a V wave. Low RV systolic pressure is a poor prognostic sign, indicative of the inability of RV to mount enough pressure to enable adequate forward flow via the pulmonary valve.
The indication for surgery in newborn and infants with cyanosis and congestive heart failure are not clear, and the decision to perform surgery should be individualized. Neonates who require repair poses a great challenge. The indication of surgery in older children and adults includes NYHA class 3 or 4, NYHA class 1or 2, but CT ratio of 0.65 or more, significant cyanosis, paradoxical embolism, and intractable arrhythmia.
Management depends on the severity and age of presentation. An asymptomatic cyanotic newborn does not need any active treatment unless cyanosis is severe. Treatment consists of temporarily keeping the PDA open using prostaglandin E1 infusion until the PVR drops. Intubation and positive pressure ventilation may help to manage pulmonary hypertension more effectively. Correction of metabolic acidosis with bicarbonate and inotropic infusions for low cardiac output will be needed. Features of heart failure from tricuspid regurgitation may be treated with anti-failure medications. Supraventricular tachycardia from the accessory pathway or atrial flutter from enlarged atrium should be controlled using appropriate anti-arrhythmia medications. Restrictive PFO/ASD may require balloon atrial septostomy to stabilize the infant for further management.
Multiple surgical approaches have been described for treatment of Ebstein anomaly. Surgical closure of ASD may provide the symptomatic improvement by controlling the significant left to right shunting and mild cyanosis. The Danielson repair consists of repair of tricuspid valve by plication of the atrialized portion of RV, narrowing the size of the tricuspid valve and creating a monoleaflet tricuspid valve that is competent. The Carpentier repair consists of plicating the atrialized portion of RV and narrowing the tricuspid valve annulus but in the direction at right angles from that performed by Danielson. The Cone procedure consists of mobilizing the anterior and posterior leaflets from their anomalous attachments, rotating the detached edges of these leaflets clockwise and suturing them to the septal edge of the anterior leaflet at the level of the tricuspid valve annulus. The small number of patients undergo one and a half repair. The surgery consists of patch closure of ASD, repair of the tricuspid valve with reduction of the atrialized portion of the RV. A Fontan operation for the rare patients with tricuspid stenosis and hypoplastic right ventricle may be required.
Severe cardiomegaly with pulmonary oligemic in a cyanotic newborn is highly suggestive of Ebstein anomaly. Other conditions to be considered as differential are critical PS or pulmonary atresia with the intact ventricular septum and functional pulmonary atresia. Tricuspid atresia, transposition of the great arteries (TGA), and tetralogy of Fallot (TOF) may rarely mimic Ebstein anomaly.
The Celermajer index to predict an outcome based on fetal or neonatal echocardiogram is used. Apical four chamber view is used for measurement. A ratio of the area of the RA plus an atrialized portion of RV to the combined area of functional, the distal portion of RV, LV, and LA is used for grading.
Celermajer index predicts mortality. The higher the grade, the higher is the mortality.
It leads to cyanosis, congestive heart failure, and a raised arrhythmia risk.
Ebstein anomaly is a rare congenital heart defect. Mild forms are asymptomatic. Moderate forms managed with relative ease and severe form is a challenge to manage.
Prognosis depends on the severity of the lesion, age at presentation and type of surgical repair. Surgical outcomes have improved over time, but the early presentation in fetus and newborn is associated with poor prognosis.
The majority of infants with Ebstein anomaly come to attention soon after birth. These infants need NICU monitoring, and hence, the ICU nurse must be familiar with the management of congenital heart disorders. While some infants have an isolated heart anomaly, others may also have involvement of other organ systems, and hence appropriate consultations are required. Once the diagnosis is made, surgery is usually required in the symptomatic infant. Post surgery, the infants require close monitoring in the NICU for an extended period of time until all the pacing wires and chest tubes have been removed and the infant is breathing without the aid of a mechanical ventilator.
The outcomes depend on the severity of the anomaly. Poor prognostic factors include an early age at presentation, enlarged cardiothoracic ratio, advanced NYHA class and a high-grade Celermajer index. Based on case reports and small series, today a few patients may survive past the fifth decade of life.