Unguarded tricuspid orifice with two-chambered right ventricle.

Catheterization and anatomical data are presented of an infant with cyanosis due to a most unusual variant of unguarded tricuspid valve orifice in association with a two-chambered right ventricle. The inlet portion of the right ventricle ended blindly and was completely separated from the outlet portion by a muscular wall. The outlet chamber, which supported the pulmonary trunk, received its blood from the left ventricle through an outlet foramen. The condition is considered to be related to imperforate Ebstein's anomaly.