A heart valve prosthesis includes an expandable prosthetic valve including three valve leaflets coupled to an anchoring structure. The anchoring structure includes an annular member and a plurality of arms movably coupled to the annular member at one end. The free ends of the arms extend radially away from the prosthesis toward a valve annulus. The arms are configured to fit in a space defined between an open native valve leaflet and a wall of a valve sinus. The arms are sufficiently resilient such that they resist downward movement in response to pressure exerted on the prosthesis, facilitating anchorage and stabilization of the prosthesis at the implantation site.