Which of the following statements about the pathophysiology of Ebstein's anomaly is/are true?

A. The tricuspid valve is usually insufficient.

C. The redundant anterior leaflet of the tricuspid valve may cause obstruction of the right ventricular outflow tract.

E. High pulmonary vascular resistance in neonates exacerbates tricuspid regurgitation and cyanosis. 

DISCUSSION: Ebstein's anomaly is characterized by downward displacement of the tricuspid valve into the right ventricular cavity. The anterior leaflet is large and “sail-like,” while the other two leaflets are rudimentary. Although the tricuspid valve occasionally may be stenotic, it is usually regurgitant. The tricuspid regurgitation and functional right ventricular outflow tract obstruction caused by the large anterior leaflet lead to right-to-left shunting across the ASD. Systemic venous hypertension is often present, but pulmonary hypertension almost never occurs with this malformation. Finally, neonates that present with Ebstein's anomaly are markedly cyanotic, owing to their high pulmonary vascular resistance. This causes a functional pulmonary atresia, which increases right-to-left shunting across the ASD.