Due to various factors, the two leaflets normally involved in sealing the mitral valve to retrograde flow may not coapt properly.

[3] Under normal conditions the mitral valve undergoes significant dynamic changes in shape and size throughout the cardiac cycle.

[citation needed] Throughout the cardiac cycle, the annulus undergoes a sphincter motion, narrowing down the orifice area during systole to facilitate coaptation of the two leaflets and widens during diastole to allow for easy diastolic filling of the left ventricle.

Today, cardiac surgeons can select from a variety of annuloplasty devices, flexible, semi-rigid, or rigid, incomplete or complete, planar or saddle-shaped, adjustable and non-adjustable.

The goal of semi-rigid rings is to maintain coaptation and valve integrity during systole, while allowing for good hemodynamics during diastole.