**1. Introduction**

Ebstein's anomaly (EA) was first described by Wilhelm Ebstein in 1866 noting the septal and inferior leaflets of the tricuspid valve arose from the right ventricular myocardium [1]. EA is a rare congenital heart disease with a prevalence of 2.4 per 10,000 live births [2]. Embryologically, EA is a result of varying degrees of failure of leaflets to delaminate from the underlying endocardium that results in a number of characteristic features. There are varying degrees of apical displacement of the tricuspid leaflets with the septal leaflet most severely affected followed by the posterior leaflet. Furthermore, the right ventricle (RV) is myopathic and is separated into

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two zones, with an "atrialized" poorly functional portion between the true annulus and the hinge point of the apically displaced septal leaflet, while the "functional" RV is the portion below the leaflet hinge point. Depending on the degree of leaflet displacement this functional RV volume can be quite diminutive.

**3.** The portion of the RV above the functional annulus ('atrialized right ventricle') is dilated and thin. The true tricuspid annulus is almost always enlarged. In a neonate this measures

Neonatal Ebstein's Anomaly

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**5.** The infundibulum of the RV can be obstructed by the redundant tissue of the anterior leaf-

In addition to the leaflet abnormalities there is a variable degree of ventricular myocardial dysfunction. Morphometric histopathologic studies have demonstrated that there is an absolute decrease in the number of myocardial fibers in addition to thinning of the wall of the dilated RV in EA [12].

*Type B*: The anterior leaflet has abnormal chordae but normal mobility. The RV is reduced in

*Type C*: The anterior leaflet is restricted in movement. The RV is small with a large atrialized

*Type D*: Also called 'tricuspide sac' as the leaflets form a complete sac of fibrous tissue adher-

The long term prognosis of a fetus diagnosed with EA is poor and remains one of the highest mortalities amongst congenital heart disease patients. One multicenter study showed that a fetal diagnosis of EA resulted in a 17% fetal demise. Furthermore, there was an additional 32% in-hospital attrition of live-born babies with EA with an overall 45% perinatal mortality [4]. Risk factors for perinatal mortality include lack of antegrade flow across the pulmonary valve, large cardiothoracic ratio, earlier in utero diagnosis, large tricuspid valve annulus, pericardial effusion, and right ventricular dysfunction [13–16]. Pulmonary valve regurgitation may be the most ominous risk factor representing the end result of severe tricuspid regurgitation with resultant volume load on a myopathic right ventricle that has to pump against retrograde flow from the PDA. This triad of diminished preload, increased afterload and a dysfunctional right ventricle leads to inadequate preload to the left ventricle and subsequent heart failure, cardiogenic shock and perinatal demise.

These factors in-utero lead to hydrops and arrhythmias and ultimately fetal demise.

Neonates are symptomatic as a result of ineffective RV cardiac output and severe TV regurgitation. There is usually some degree of cardiomegaly which can be quite severe compressing

**4. Pathophysiology of the newborn**

**4.** The cavity of the effective RV is reduced ('functional right ventricle').

Carpentier et al. also described four grades of Ebstein's anomaly [11].

ent to the RV. The only functional part of the RV is the infundibulum.

*Type A*: The anterior leaflet has normal morphology and the RV is adequate.

let and its chordal attachments to the infundibulum.

approximately 21 mm.

volume but adequate.

**3.1. Perinatal period**

component.

The clinical manifestations of EA vary widely from mild forms presenting in adulthood, to severe forms with high mortality in the neonatal period. In utero, EA can result in hydrops and arrhythmia. Furthermore, an in utero diagnosis of EA has an incidence of 48% fetal demise [3]. Mortality rates are highest in the neonatal period ranging from 17 to 56% [4] and poses significant medical and surgical challenges.
