A valve prosthesis assembly for implantation into a native valve site includes a valve prosthesis with a prosthetic valve component and a frame. The frame of the valve prosthesis includes a central portion supporting the prosthetic valve component, the central portion being configured to fit within an annulus of the native valve site, and an inflow portion configured to engage an upstream side of the annulus and restrict movement of the valve prosthesis in a downstream direction of blood flow at the native valve site. The valve prosthesis assembly also includes a separate support flange configured to be attached to the frame after the valve prosthesis has been deployed in situ and a plurality of anchors configured to attach the support flange to the frame and configured to embed into the annulus to anchor the frame of the valve prosthesis to the native valve.