Ebstein’s anomaly
This right ventricular myopathy was first described by Wilhelm Ebstein in 1866 and is characterized by a failure of tricuspid valve (TV) delamination, annulus dilatation, and highly variable tricuspid valve morphology that typically results in severe tricuspid regurgitation (TR)30,31. The frequency of this lesion varies between 1 in 10.000 to 50.000 live births32,33. In fact, tricuspid valve dysplasia is an essential part of Ebstein’s anomaly (EA). Morphologically, in contrast to isolated dysplasia, the apical displacement of the hinge points of the tricuspid valve in EA is towards the outflow tract with rotation of the valve apparatus along the axis of the aorta, constituting an “all-or-none” criterion for the diagnosis of EA34. The value of the offset distance of the tricuspid septal leaflet compared to that of the mitral valve leaflet for estimation the severity of the disease has been questioned in the past35,36. Accordingly, this further highlights the need for an attitudinally appropriate assessment of the deformed and displaced valve. In EA, the aforementioned inlet component of the RV is functionally integrated into the right atrium (atrialized) and may become disproportionately dilated and dyskinetic, whereas the trabecular and outlet portions are situated downstream from the displaced orifice and show preserved contractility37. This consequently results in decreased forward blood flow through the right heart.
As has clearly been demonstrated and validated for adult cardiology, fetal 3D echocardiography is able to offer novel insights into the altered morphology and function of the right heart and allows elucidation of all the features of EA (e.g., shape and derangement of the valve leaflets, level of their attachment, and degree of coaptation)38,39. Figure 2 shows semiautomatic reconstruction of cardiac diagnostic planes of a fetus at 32 completed gestational weeks. Two-dimensional echocardiography revealed a cardiomegaly, an apically displaced tricuspid valve with marked insufficiency (> 3 m/s) and a left ventricular outflow tract obstruction (LVOTO). Upon assessment of the semiautomatic reconstructed planes, it could be noted that all nine views reflect anatomic abnormalities corresponding to those frequently seen in EA. Most strikingly, there is a dysplastic TV with displacement of the proximal attachments of its inferior and septal leaflets within the markedly enlarged and left-rotated heart. The atrialized right ventricle (aRV) and its demarcation against the residual RV are clearly depicted in right ventricular outflow tract (RVOT) and ductal arch views. In a recent retrospective study, Gottschalk et al. stated that EA was isolated in 54 % of cases and accompanied by other cardiac anomalies in 46 % of cases. Other obstructive lesions of the left ventricular outflow tract were found in two fetuses in their study40. In the present case, a concomitant aortic coarctation was noted, which is clearly seen in three cardiac planes (5CV, LVOT and ductal arch views). An abnormal RA/heart index (Celermajer index; > 0.7), cardiomegaly (cardiothoracic circumference ratio > 0.5), TV annulus diameter, TR severity and younger age at prenatal diagnosis and at birth have been shown to be significantly associated with an unfavorable postnatal outcome. Standardized plane reconstruction as shown in figure 2 can ease offline assessment of cardiac dimensions. Absence of antegrade pulmonary blood flow was identified as the most important hemodynamic marker with regard to postnatal survival40-43. In a recent multicenter study, qualitative left ventricular dysfunction has been identified as an important predictor of poor postnatal outcome44. This functional impairment with reduced left ventricular output is likely secondary to compression by the aRV, warranting close surveillance for LV dysfunction throughout pregnancy44-46.