Ebstein's anomaly is caused by

(A) Lithium # Environmental factors found in studies include maternal exposure to benzodiazepines.> Maternal lithium therapy can rarely lead to Ebstein's anomaly in the baby.> About 10% of cases are associated with chronic maternal lithium use.> About 20% of patients with Ebstein's anomaly have accessory electrical tissue which can cause episodes of heart racing, a condition known as Wolff-Parkinson-White syndrome (WPW).> Unusual and rare cyanotic congenital heart disease with diminished pulmonary blood flow results from an abnormality of the tricuspid valve.> Posterior as well as the septal leaflet of the tricuspid valve is displaced downwards.> Result is an attachment to the posterior wall of the right ventricle.> In addition, the leaflets are malformed and fused resulting in obstruction to flow of blood into the right ventricle.> Portion of the right ventricle above the leaflet attachment thins out and is called atrialized right ventricle.> Right ventricular contraction is also abnormal.