Pathologic elucidation of the echocardiographic features of Ebstein's malformation of the morphologically tricuspid valve in discordant atrioventricular connections.

We defined the morphology of the left atrioventricular valve in Ebstein's malformation associated with congenitally corrected transposition to elucidate the approach to diagnosis by echocardiography. We found 14 unequivocal cases out of a total of 3,720 specimens. We noted the atrial arrangement, displacement, and nature of the tricuspid leaflets, and axis of the plane of the tricuspid orifice. We constructed ratios of volume of the atrialized to the functional right ventricle, and of the right to left ventricle, as well as distances of the septal attachments of the atrioventricular junctions to the respective ventricular apices. Three specimens had abnormalities of cardiac position, and 8 had ventricular septal defect. The tricuspid valve plane was rotated 47 +/- 21 degrees from its usual position into the ventricle. The tricuspid valvar tissue was variably attached to the underlying myocardium, with the most severely affected lesion being the mural leaflet followed by the septal leaflet, and the anterior leaflet attachment the least affected. Abnormalities of the tendinous cords and the effective valvar orifice occurred in 3 specimens. The ratio of the atrialized to the functional right ventricular volume was 0.74 +/- 0.49; the ratio of the fetal right to left ventricular volume was 1.18:1 +/- 0.70:1. These data suggest that plastic repairs of the right ventricle would leave a small functional right ventricle, but that valve replacement could restore the volume of the ventricle. Thus, the plane of displacement of the valve in corrected transposition appears less amenable to 4-chamber echocardiography than other forms of Ebstein's malformation. Changes in the echocardiographic planes should display the morphology and also provide some hemodynamic information.