Mitral Valve Annulus Tension

The mitral valve annulus is an anatomical structure joining the leaflets and left ventricle wall. It is divided into the fibrous annulus in the anteromedial section and the myocardium annulus in the posterolateral section, according to annulus histology. Two trigones are in the fibrous annulus. Mitral annulus supports leaflets in the valve coaptation and controls inflow hemodynamics during a cardiac cycle. When the mitral valve is fully open during diastole, inflow drag force on the leaflets and chordae pulls the leaflets approximately apically. As mitral valve leaflets coaptate during systole, trans-mitral pressure acts on the leaflets and induces leaflet tension which is transferred to the annulus and chordae. The leaflet tension at the annulus per unit length is defined as annulus tension (AT). Annulus dilatation is a mitral valve pathology that is related to AT and its interaction with the myocardium. Little is known about the detailed mechanism of annulus dilatation. But from mechanics standpoint, there are two possible mechanisms that change annulus size. AT pulls annulus towards the center of mitral valve orifice and is balanced by myocardium force on the annulus that pulls the annulus outward. Annulus size depends upon which force is predominant in annulus mechanics. It is hypothesized that the AT is one of the important mechanism to control annulus size. This hypothesis suggests that annulus size can be controlled by the AT and its interaction with the myocardium. We aim to understand annulus dilatation by the AT. The objective of the current study was to understand the tension transferred to the mitral annulus by the leaflets during the valve coaptation.