Background
Ebstein anomaly of the tricuspid valve is a congenital defect characterized by downward displacement of the insertion of septal and posterior leaflets. Such displacement leads to tricuspid regurgitation secondary to lack of coaptation of the leaflets. As a consequence of downward displacement of leaflet insertion, a portion of the right ventricle (RV) is included on the right atrial side ("atrialized portion of the RV"). The severity of the clinical presentation depends on the degree of displacement of the leaflets and the associated cardiac defects.
The lesion was first described in 1866 by Wilhelm Ebstein and first referred to as Ebstein disease in 1927. In addition to the downward displacement of the insertion of tricuspid valve leaflets, there may also be (i) redundancy of the normally-inserted anterior leaflet of the tricuspid valve and (ii) abnormal attachment of the tricuspid valve chordae to the RV wall, causing obstruction to the RV outflow tract.
Associated cardiac defects include (i) atrial septal defect (ASD) or patent foramen ovale (PFO), which is present in 90% of the patients; (ii) pulmonary stenosis or atresia, which is present in 20%-25% of the patients; and (iii) an accessory conduction pathway similar to that of Wolf-Parkinson-White syndrome (20%).
Patients with congenitally-corrected transposition of the great arteries (L-TGA) have the tricuspid valve on the left-side of the heart. This type of Ebstein anomaly noted in such a left-sided tricuspid valve is called an Ebsteinoid anomaly.
Patient education
Patient and family education is directed at communicating the importance of prophylaxis for bacterial endocarditis and identifying the signs and symptoms of potential arrhythmias and progressive congestive heart failure.
For patient education resources, see Heart Health Center, as well as Palpitations (Causes, During Pregnancy, Symptoms, Treatment).
Pathophysiology
Hemodynamic status in patients with Ebstein anomaly depends on the severity of the lesion. Those with mild leaflet displacement and mild valvar regurgitation may be asymptomatic for many years, whereas severe leaflet displacement with severe tricuspid valve regurgitation results in severe dilatation of the right atrium—even as a fetus. The size of the functional right ventricular (RV) (excluding the atrialized portion of RV) may be too small to generate adequate RV systolic pressure (by a combination of its small functional size and severe tricuspid regurgitation). Such severe cases present in newborns. Cyanosis occurs owing to three mechanisms: Right-to-left shunting at the atrial septal defect or patent foramen ovale, decreased pulmonary blood flow as a result of either functional or anatomic pulmonary valve stenosis/atresia and high pulmonary vascular resistance noted as neonatal transitional circulation. In such circumstances, the newborn will be dependent on the patent ductus arteriosus to maintain pulmonary blood flow at least until the pulmonary vascular resistance decreases in the newborn. Congestive heart failure may also develop secondary to a small functional RV and reduced RV compliance. Neonatal presentation of Ebstein anomaly needs careful management and has a worse prognosis than presentation at an older age.
Patients with moderate leaflet displacement present with transient cyanosis as newborns, which improves with a gradual decrease in pulmonary vascular resistance. These patients may be followed clinically for elective repair later when they're older.
Additional problems in these patients include an association with paroxysmal supraventricular tachycardia (SVT), which occurs in 25%-50% of patients. Many of these patients with SVT have Wolff-Parkinson-White (WPW) syndrome.
In short, patients with Ebstein anomaly are at risk not only for tricuspid regurgitation and RV enlargement but also for RV and left ventricular (LV) dysfunction and dyssynchrony. [1, 2] LV dysfunction and dyssynchrony are associated with heart failure and disease severity parameters that can be assessed with cardiac magnetic resonance imaging (CMRI) tracking (CMR-FT). [1, 2]
Epidemiology
Ebstein anomaly accounts for 0.3%-0.6% of all congenital heart diseases. Most cases are sporadic, but familial cases have occurred. [3, 4, 5] Maternal lithium and benzodiazepine exposures have been implicated as a cause of this disease. No specific gene defect has been consistently identified in association with Ebstein anomaly, although more recently, a missense mutation in FLNA (filamin A), an actin-binding protein located at Xq28, has been identified. [4]
A higher occurrence of Ebstein anomaly is reported in the offspring of women with Ebstein anomaly (6%) than for men with this disease (0.6%). [6]
Prognosis
Prognosis depends on the severity of the anomaly. However, individuals with Ebstein anomaly have a significantly increased risk for sudden death, with multivariate key clinical predictors of sudden death including previous ventricular tachycardia, heart failure, tricuspid valve surgery, pulmonic stenosis, and hemoglobin level above 15 g/dL. [7]
In an analysis of 2010-2016 data from 255 neonates and 239 infants at 95 centers from the Society of Thoracic Surgeons Congenital Heart Surgery database to evaluate surgical management and outcomes of Ebstein anomaly, investigators found that there was a very high risk of symptomatic Ebstein anomaly in early infancy and these cases involved a variety of surgical interventions. [8] The primary procedures most often performed in neonates were Ebstein repair (39.6%), systemic-to-pulmonary shunt (20.4%), and tricuspid valve closure (9.4%), with an overall surgical mortality of 27.4 (51.4% composite morbidity-mortality). Among infants, the most common primary procedures were superior cavopulmonary anastomosis (38.1%) and Ebstein repair (15.5%), with an overall operative mortality of 9.2% (20.1% composite morbidity-mortality). [8]
Pregnancy influences cardiac function and hemodynamics in women with Ebstein anomaly; these women should be clinically and hemodynamically monitored during their pregnancy to minimize their cardiac risk as well as to aid clinicians in choosing the appropriate delivery mode. [9] In a retrospective (1995-2015) single-center study of 17 women with Ebstein anomaly who underwent either elective cesarean section (8 women, 9 pregnancies) or vaginal delivery (9 women, 14 pregnancies), pregnancy was relatively safe. However, some women underwent elective cesarean delivery due to the development of cyanosis, arrhythmia, or significant heart failure. [9]
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Frontal chest radiograph in an infant with severe Ebstein anomaly. This image shows a large heart that leaves little space for the lung. Although the appearance is relatively nonspecific, the large heart should suggest Ebstein anomaly in the differential diagnosis.
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Chest radiograph of a newborn with severe Ebstein anomaly and patent ductus arteriosus. Most of the cardiomegaly is secondary to right atrial enlargement. The pulmonary vascular markings are normal in this newborn.
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Echocardiogram in an apical four-chamber view. This image reveals downward displacement of the insertion of the septal leaflet of the tricuspid valve (arrow) in a 3-year-old boy. The child has moderate tricuspid regurgitation and has not required surgical intervention so far. aRV = atrialized portion of right ventricle, LA = left atrium, LV = left ventricle, RA = right atrium, RV = functional portion of the right ventricle.
