The saddle shape of the mitral valve: More than just a shape

The knowledge about mitral valve (MV) has tremendously increased from the days when Andreas Vesalius suggested the picturesque term “mitral” to describe the left atrioventricular valve owing to its resemblance to a plan view of the bishop’s mitre. In its open state, the MV leaflets extend like a funnel from its base at the atrioventricular junction to the free margins. Tendinous chords attach the MV leaflets to two closely arranged anterolateral and posteromedial papillary muscle. The MV leaflets, the annulus, the atrial and ventricular wall surrounding the annulus, the tendinous chords, the papillary muscles, and the myocardium surrounding the papillary muscle attachment constitute the MV complex/apparatus. For the prevention of the back flow during systole, precisely timed interaction of all the anatomical components of the MV complex is essential. Alterations in the structure and function of any of these elements can lead to MV dysfunction. [1] The MV annulus is a concept and not an anatomically well-defined structure. The anterior one-third of the MV annulus that houses the anterior mitral leaflet (AML) is fibrous and well defined. Fibroelastic tissue extends posteriorly from the extremes of the anterior fibrous partial ring and forms the posterior two-thirds of the MV annulus; this part of the annulus tends to be “weak” and lacks a well-formed fibrous cord. The posterior mitral leaflet (PML) is attached to this part of the MV annulus. This is the area affected in “annular dilatation” and is often involved in calcification of the annulus.The MV is non-planar and obliquely located in the heart, and the annulus is saddle shaped. It is not known how the MV annulus acquires non-planar and saddle shape. Also, it is not known how this saddle shape is maintained. The finite element analyses consistently Access this article online