Above. Post-delivery anatomy. Ebstein anomaly is a defect of the tricuspid valve. There is downward displacement into the right ventricle of the septal and posterior leaflets of the tricuspid valve, which results in a portion of the right ventricle (RV) which is incorporated into the right atrium (RA) (atrialized RV). The RV is functionally hypoplastic (small and underdeveloped) and the RV free wall is dilated and thin. The tricuspid valve is incompetent. The valve leaflets are abnormal, and there is regurgitation of blood back from the RV into the RA. As a result, the RA becomes dilated and hypertrophied. Either a patent foramen ovale (PFO) or atrial septal communication (ASD) with a right to left shunt is present.