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.