Prosthetic Heart Valve

A prosthetic heart valve for implantation at the mitral annulus of a heart, the prosthetic heart valve comprising: a support framework reversibly transformable between a collapsed configuration and an expanded configuration; and one or more leaflets connected to the framework; wherein, in the expanded configuration: the support framework defines a fluid pathway through the prosthetic heart valve, the fluid pathway having a portion with a D-shaped cross section for engaging the mitral annulus; and the one or more leaflets allow fluid to pass through the fluid pathway in a first direction but prevent fluid from flowing in the opposite direction.