Mitral valve malformation of Ebstein type in absence of corrected transposition.

The first documented case is reported of mitral valve malformation of the Ebstein type in the absence of corrected transposition. In this case, the ring of the inferior leaflet of the mitral valve was displaced downward into the left ventricle, dividing the latter into a proximal atrialized and a distal effective ventricular chamber. The anterior leaflet was not displaced. The chordae tendineae of both leaflets were thickened. The papillary muscles were hypertrophied and abnormal in architecture. The outflow tract of the effective left ventricle was shortened. The valve leaflets were thickened, and the mitral valve was probably insufficient.