The Unsaddled Annulus

Masterful mitral valve (MV) repair demands thorough understanding of integrated mitral apparatus structure and mechanics.1,2 One consistently reported feature, the saddle shape of the mitral annulus, was recognized in the process of resolving the contradiction posed by an apparently high prevalence of MV prolapse (MVP) in otherwise healthy individuals: A normal saddle-like shape will show opposite leaflet curvatures with leaflets above or below the annulus in perpendicular 2-dimensional echocardiographic views, leading to the false impression of prolapse based on an assumed planar annulus.3 Criteria recognizing annular nonplanarity substantially improved diagnostic specificity.4,5Article see p 832Whether this saddle shape, by analogy to architectural structures, best supports ventricular-imposed stresses on the valve compared with a flat annulus6 was first shown computationally7 and then confirmed in vitro and in vivo.8–11In this issue of Circulation , Lee et al12 revisit the implications of annular shape. They have used 3-dimensional echocardiography as a powerful technique to explore MV geometry in 100 subjects, 68 with degenerative MVP, with or without important mitral regurgitation (MR ≥ moderate), and 32 normal controls. Their most salient finding is that the mitral annulus of patients with more severe MR is not only greater in area but also flatter, with a decreased ratio of annular height to commissural width. That ratio is strongly associated with chordal rupture, which progressively increases in prevalence from 7% in those with the most saddle-shaped annuli to 42% in those with the most planar. Annular flattening is also associated with increased leaflet billowing volume, and together …