Ebstein's Anomaly

O35.8, Q22.5

In Ebstein’s anomaly, the attachments of the septal and mural leaflets of the tricuspid valve are displaced downward into the right ventricle and the anterior leaflet is elongated. [3]. 

The postnatal incidence has been estimated at approximately 50–100 per 1 million live births, which comprises up to 1% of con¬genital heart disease with no predilection for either gender [2]. However, the prenatal incidence has been noted to be substantially higher, comprising up to 8% of congenital heart disease [1].

Among fetuses and with Ebstein’s anomaly, the following pathologic characteristics have been described: apical displacement of the septal and/or mural leaflet without displacement of the anterior leaflet from the atrioventricular junction, dysplastic features of the valve leaflets (beyond their displacement), and atrialization of the inlet portion of the right ventricle (with or without thinning of the atrialized myocardium) [4]. The redundant and “sail-like” nature of the anterior leaflet may lead to a one-leaflet valve mechanism with anterosuperior displace¬ment of the valve orifice toward the right ventricular outflow tract [5]. Abnormalities of the subvalvar apparatus, including anomalous or tethered chordal attachments and/or papillary muscles, further contribute to the morphologic spectrum of Ebstein’s anomaly.

Associated cardiac defects are common, and many occur as a consequence of the altered physiology of Ebstein’s anomaly during fetal development. The most common associated cardiac defect among patients postnatally is a patent foramen ovale or atrial septal defect, which may lead to right-to-left shunting and cyanosis. There is also likely greater than normal physiologic right-to-left shunting in utero due to the severity of the tricuspid regur¬gitation and associated right ventricular dysfunction. Right ventricular outflow tract obstruction may occur in up 40% of patients with Ebstein’s anomaly [4]. It is important to distinguish between true or anatomic pulmonary atresia and “func¬tional” pulmonary atresia.  A ventricular septal defect, typ¬ically of the perimembranous type, may also be present, with or without right ventricular outflow tract obstruction [4]. Ebstein’s anomaly may also occur in the context of congenitally cor¬rected transposition of the great arteries (cc-TGA). The presence of right atrial enlargement and a high prevalence of accessory pathways increase the risk for supraventricular tachyarrhythmia, primarily seen in postnatal studies but also prenatally [6]. 

This type of malformation can occasionally be associated with extracardiac anomalies. In a large fetal series, Ebstein’s anomaly was associated with chromosomal abnormalities in 1.2% of cases (one case of trisomy 21) and a further 6% had an extracardiac anomaly. The latter included cleft lip and palate, diaphragmatic hernia, duodenal atresia and sacrococcygeal teratoma. Fetal hydrops was associated in 7% of cases, being seen particularly in cases with severe tricuspid regurgitation [3].

In the four-chamber view the tricuspid valve will be seen to be displaced apically, with an exaggerated differential insertion. The degree of displacement of the valve is variable and in some cases the tricuspid valve leaflet may appear tethered to the ventricular septum. The anterior leaflet will appear elongated. There will often be tricuspid regurgitation, the severity of which varies from case to case. Severe tricuspid regurgitation can cause right atrial enlargement, which results in cardiomegaly and an increased cardiothoracic ratio. However, in some cases there may be little tricuspid regurgitation and minimal or no cardiomegaly. Secondary lung hypoplasia as a result of longstanding compression from severe cardiomegaly can be a life-threatening associated feature. Obstruction to the right ventricular outflow tract is common, so that there may be associated pulmonary stenosis or atresia. In some cases there may be reduced forward flow into the pulmonary artery as a result of gross tricuspid regurgitation. This may produce functional pulmonary atresia which may be difficult to distinguish from anatomical atresia. Hypoplastic pulmonary arteries may be observed, particularly in the context of anatomic pulmonary atresia.

On occasion, it may be difficult to differentiate prenatally between Ebstein anomaly and tricuspid valve dysplasia. The origin of the tricuspid regurgitant jet on color Doppler may help in differentiating these two lesions. In tricuspid valve dysplasia, the jet arises from the normally inserted tricuspid valve at the level of the annulus, whereas in Ebstein anomaly, the origin of the regurgitant jet is displaced inferiorly within the RV owing to the low insertion of the septal and posterior tricuspid valve leaflets. Severe tricuspid regurgitation with cardiomegaly can be found in dilative cardiomyopathy and in other noncardiac lesions with fetal hemodynamic impairment. Premature closure of the ductus arteriosus may also be present with tricuspid regurgitation. A thorough evaluation of the tricuspid valve in grayscale, and color Doppler and spectral Doppler velocities across the ductus arteriosus helps in differentiating this entity from Ebstein’s anomaly.

Ebstein’s anomaly is a spectrum disorder with a very wide range of immediate, medium- term and longer-term problems. During fetal life the cardiac findings may remain stable but, in some cases, tricuspid regurgitation can worsen as pregnancy advances, resulting in increasing cardiomegaly and the development of hydrops. This has a major adverse impact on the prognosis. After birth the immediate concern is adequate ventilation, particularly in cases where there has been marked cardiomegaly compromising lung development. Some babies are duct-dependent and require an urgent systemic to pulmonary artery shunt (Blalock-Thomas-Taussig shunt) to maintain pulmonary blood flow, whilst others do not need any early surgical intervention or support.

In reported outcome  data in a large single-centre fetal series of 82 cases of Ebstein’s anomaly diagnosed prenatally, 44% of pregnancies resulted in a termination of pregnancy. If the terminations are excluded then the outcome of the continuing pregnancies was: 24% resulting in spontaneous intrauterine death, 22% died in the neonatal period, 4% died in infancy and 50% were alive at last update [3].

 Another  multicenter study reported high perinatal mortality rates for affected  fetuses. In this study there were 243 fetuses (mean gestational age 27 weeks) diagnosed with Ebstein anomaly from 2005 to 2011 at 23 centers [2]. The rate of fetal demise was 17 percent, 5 percent were lost at follow-up, and 6 percent were terminated. Of 176 live-born patients, 32 percent died before discharge. Independent predictors at the time of diagnosis of perinatal mortality were gestational age <32 weeks, pulmonic regurgitation, a pericardial effusion, and tricuspid valve annulus z-score.

1.    Sharland, G.K., S.K. Chita, and L.D. Allan, Tricuspid valve dysplasia or displacement in intrauterine life. J Am Coll Cardiol, 1991. 17(4): p. 944-9.
2.    Freud, L.R., et al., Outcomes and Predictors of Perinatal Mortality in Fetuses With Ebstein Anomaly or Tricuspid Valve Dysplasia in the Current Era: A Multicenter Study. Circulation, 2015. 132(6): p. 481-9.
3.    Sharland, G., Fetal Cardiology Simplified: A Practical Manual 1st Edition. 2013: p. 109.
4.    Lang, D., et al., Pathologic spectrum of malformations of the tricuspid valve in prenatal and neonatal life. J Am Coll Cardiol, 1991. 17(5): p. 1161-7.
5.    Schreiber, C., et al., Morphologic spectrum of Ebstein's malformation: revisitation relative to surgical repair. J Thorac Cardiovasc Surg, 1999. 117(1): p. 148-55.
6.    Cappato, R., et al., Radiofrequency current catheter ablation of accessory atrioventricular pathways in Ebstein's anomaly. Circulation, 1996. 94(3): p. 376-83.

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