Findings - Plain film shows box shaped heart with cardiomegaly, involving mainly the right side of the heart and a narrow pedicle.
MRI: SSFP axial image confirms the dilatation of the right atrium. There is tethering of the leaflet of the tricuspid valve to the apex of the right ventricle.
Ebstein anomaly is seen in 0.5-1% of the patients with congenital heart diseases. It is associated with dysplasia and inferior displacement of the septal and posterior leaflets of the tricuspid valves. The distal leaflet is attached to portions of the right ventricular apex, abnormally placed chordae, or moderator band. The tricuspid valve annulus is enlarged and is occasionally inferiorly displaced. This causes tricuspid regurgitation and volume overloading on the right side of the heart and a right – to – left shunt through a patent foramen ovale.
MRI: SSFP axial image confirms the dilatation of the right atrium. There is tethering of the leaflet of the tricuspid valve to the apex of the right ventricle.
Ebstein anomaly is seen in 0.5-1% of the patients with congenital heart diseases. It is associated with dysplasia and inferior displacement of the septal and posterior leaflets of the tricuspid valves. The distal leaflet is attached to portions of the right ventricular apex, abnormally placed chordae, or moderator band. The tricuspid valve annulus is enlarged and is occasionally inferiorly displaced. This causes tricuspid regurgitation and volume overloading on the right side of the heart and a right – to – left shunt through a patent foramen ovale.
The right ventricle is divided into two parts, a thin walled proximal ‘atrialised’ portion and a more distal component with decreased pumping capacity. Consequently, the portion of the right ventricle into which blood flows fails to function normally, and the outflow tract functions as the main pumping apparatus of the right ventricle.
MRI demonstrates the inferior displacement of the tricuspid valve. This displacement is significant when it is greater than 8mm/m2 body surface area. The functional fraction of the right ventricles is assessed with GRE cine images. This plays a role in planning surgery – valve replacement versus reconstruction.
Ebstein anomaly can also be a component of other complex cardiac diseases. It can be associated with pulmonary stenosis or atresia, ventricular septal defect, mitral stenosis, tetralogy of Fallot, and corrected or partial transposition of the great vessels.
EMBRYOLOGY OF THE TRICUSPID VALVE
The tricuspid valve develops from the right ventricular myocardium and the endocardial cushions. The anterior leaflet embryologically develops first, arising from the mesenchyme surrounding the atrioventricular orifice, while the posterior and septal leaflets develop later through creation of a diverticulum and undermining of the myocardium. In patients with Ebstein anomaly, undermining of the myocardium either fails to occur or occurs only partially. This leaves the entire septal and posterior valve leaflets and the distal anterior valve leaflet either low within the right ventricle or adherent to the right ventricle walls. The difference in the embryology of the valve leaflets is the likely reason why the proximal portion of the anterior valve leaflet is not usually displaced and the anterior leaflet is the most dysplastic valve leaflet.