Which congenital abnormality is characterized by displacement of the tricuspid valve into the right ventricle, right atrial enlargement, large right-to-left shunt, and decreased right ventricular outflow?

• A. Ebstein's anomaly
• B. Tetralogy of Fallot
• C. Coarctation of the aorta
• D. Transposition of the great arteries

Answer: (A)

Displacement of the tricuspid valve toward the apex with atrialization of part of the right ventricle is the hallmark of Ebstein’s anomaly. This abnormal leaflet position causes severe tricuspid regurgitation and markedly enlarges the right atrium, while the functional right ventricle becomes small and inefficient. The enlarged right atrium and reduced forward flow often promote a large right-to-left shunt across an atrial septal defect or patent foramen ovale, leading to cyanosis. Because the problem lies with the tricuspid valve apparatus itself and the downstream effect on the right heart, the RV outflow is diminished from the distorted valve and atrialized RV tissue. This combination—apical displacement of the tricuspid valve, right atrial enlargement, a prominent right-to-left shunt, and decreased effective RV outflow—is characteristic of Ebstein’s anomaly, distinguishing it from other congenital lesions like Tetralogy of Fallot, coarctation of the aorta, or transposition of the great arteries, which involve different structural abnormalities.