"Offsetting" of the septal tricuspid leaflet in normal hearts and in hearts with Ebstein's anomaly. Anatomic and echographic correlation.

Apical displacement of the septal tricuspid valve leaflet is considered the most reliable criterion to diagnose Ebstein's anomaly. This feature is best assessed using 2-dimensional echocardiography. However, the anatomy in Ebstein's anomaly is highly variable; therefore, the problem arises as to how to distinguish between the abnormal displacement in borderline cases of Ebstein's disease and the lowered septal offsetting of the tricuspid valve in normal persons. To solve this problem the minimal and maximal differences in offsetting of the tricuspid and mitral valves have been studied, both anatomically and echocardiographically, in fetuses, infants, children and adults. In fetuses in the first trimester of pregnancy it was impossible to measure a difference in offsetting of the 2 atrioventricular valves. Thereafter, a gradual increase occurred with age. In normal hearts the most significant separation was usually recorded in anteriorly angulated 4-chamber views, whereas in hearts with Ebstein's anomaly maximal separation appeared to posteriorly angulated views. The anatomic and echographic measurements showed a constant relation. When the minimal distances in offsetting were measured, an overlap was found between cases with and those without Ebstein's anomaly. The maximal values, however, clearly discriminated between the 2 conditions. The critical difference in children was 15 mm, and in adults the discriminating value was 20 mm.