Model of closing and tethering forces acting on the mitral valve. The forces acting on mitral valve leaflets are shown in model parasternal short axis (A) and long axis (B) sections (green dashed line in (A) indicates the plane shown as (B)). The LV, LA, and aorta are shown in gray and blue, with PMs indicated by hatched lines (since the PMs are not at the same level as the mitral annulus). The mitral annulus and leaflets are shown in red with the aortomitral curtain in purple. Normal systolic closing forces include: LV contraction (green arrows), basal myocardial clockwise rotation (blue arrow), and mitral annulus contraction (purple arrows). Tethering forces include passive constraint of the mitral annulus (red arrows) and tethering from the PM-chordae and PM contraction (orange arrows). The relative size of the arrow delineates relative magnitude of the forces acting on the mitral leaflets.