Figure 2. Discrepancy in leaflet-annular relations in echocardiographic views of a saddle-shaped model structure. The heavy interrupted lines of the left indicate the plane of view. On the right, echocardiographic images of the model are shown along with diagrams of the surrounding structures. The dotted lines in echocardiographic images demarcate an apparent annular plane in each view; they were placed manually, with the aid of an echocardiographic instrument. Note that in the four-chamber view, leaflets prolapse past the annular plane. Ant = anterior; Ao = aorta; LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle; Post = posterior. Reprinted with permission from R. A. Levine et al.: The relationship of mitral annular shape to the diagnosis of mitral valve prolapse. Circulation 1987; 75:756-67.