Background— Few data exist on the relation of the 3-dimensional morphology of mitral valve and degree of mitral regurgitation (MR) in mitral valve prolapse. Methods and Results— Real-time 3-dimensional transesophageal echocardiography of the mitral valve was acquired in 112 subjects, including 36 patients with mitral valve prolapse and significant MR (≥3+; MR+ group), 32 patients with mitral valve prolapse but no or mild MR (≤2+; MR− group), 12 patients with significant MR resulting from nonprolapse pathologies (nonprolapse group), and 32 control subjects. The 3-dimensional geometry of mitral valve apparatus was measured with dedicated quantification software. Compared with the normal and MR− groups, the MR+ group had more dilated mitral annulus ( P <0.0001), a reduced annular height to commissural width ratio (AHCWR) ( P <0.0001) indicating flattening of annular saddle shape, redundant leaflet surfaces ( P <0.0001), greater leaflet billow volume ( P <0.0001) and billow height ( P <0.0001), longer lengths from papillary muscles to coaptation ( P <0.0001), and more frequent chordal rupture ( P <0.0001). Prevalence of chordal rupture increased progressively with annulus flattening (7% versus 24% versus 42% for AHCWR >20%, 15%–20%, and <15%, respectively; P =0.004). Leaflet billow volume increased exponentially with decreasing AHCWR in patients without chordal rupture ( r 2 =0.66, P <0.0001). MR severity correlated strongly with leaflet billow volume ( r 2 =0.74, P <0.0001) and inversely with AHCWR ( r 2 =0.44, P <0.0001). In contrast, annulus dilatation but not flattening occurred in nonprolapse MR patients. An AHCWR <15% (odds ratio=7.1; P =0.0004) was strongly associated with significant MR in mitral valve prolapse. Conclusion— Flattening of the annular saddle shape is associated with progressive leaflet billowing and increased frequencies of chordal rupture and may be important in the pathogenesis of MR in mitral valve prolapse.

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