A heart valve prosthesis comprising: a supported valve comprising a biological valve portion mounted within a support structure, the supported valve being configured to provide for substantially unidirectional flow of blood through the supported valve, the supported valve having inflow and outflow ends that are spaced axially apart from each other; and a fixation support member (14, 174) comprising inflow (40, 173) and outflow (42, 175) portions, the inflow portion of the fixation support member extending from a radially inner contact surface (44, 176, 180) of the fixation support member radially outwardly and axially in a direction of the inflow end of the supported valve, the outflow portion of the fixation support member extending from the radially inner contact surface radially outwardly and axially in a direction away from the inflow portion of the fixation support member, the radially inner contact surface being attached to a radially outer surface of the supported valve adjacent the inflow end of the supported valve, the supported valve and the fixation support member being deformable between a reduced cross-sectional dimension and an expanded cross-sectional dimension thereof, whereby implantation of the heart valve prosthesis is facilitated, wherein the fixation support member further comprises a flexible and deformable annular support which includes an inflow portion, an outflow portion, and an annular opening extending through the support corresponding to a radially inner extent thereof, the fixation support member having a substantially V-shaped cross-sectional configuration for a longitudinal cross-section taken axially through the prosthesis in its expanded cross-sectional dimension, such that the radially inner contact surface of the fixation support member defines an apex and each of the inflow and outflow portions of the fixation support member define legs of the V-shaped cross-sectional configuration, characterised in that the annular support is a continuous monolithic structure having a substantially V-shaped cross-sectional configuration for a longitudinal cross-section taken axially through the prosthesis in its expanded cross-sectional dimension, said structure consisting in a zigzag arrangement of support features (24, 26), in which the support features alternate between extending in the inflow and outflow directions along a circumferential path corresponding to the radially inner extent of the support structure. a supported valve comprising a biological valve portion mounted within a support structure, the supported valve being configured to provide for substantially unidirectional flow of blood through the supported valve, the supported valve having inflow and outflow ends that are spaced axially apart from each other; and a fixation support member (14, 174) comprising inflow (40, 173) and outflow (42, 175) portions, the inflow portion of the fixation support member extending from a radially inner contact surface (44, 176, 180) of the fixation support member radially outwardly and axially in a direction of the inflow end of the supported valve, the outflow portion of the fixation support member extending from the radially inner contact surface radially outwardly and axially in a direction away from the inflow portion of the fixation support member, the radially inner contact surface being attached to a radially outer surface of the supported valve adjacent the inflow end of the supported valve, the supported valve and the fixation support member being deformable between a reduced cross-sectional dimension and an expanded cross-sectional dimension thereof, whereby implantation of the heart valve prosthesis is facilitated, wherein the fixation support member further comprises a flexible and deformable annular support which includes an inflow portion, an outflow portion, and an annular opening extending through the support corresponding to a radially inner extent thereof, the fixation support member having a substantially V-shaped cross-sectional configuration for a longitudinal cross-section taken axially through the prosthesis in its expanded cross-sectional dimension, such that the radially inner contact surface of the fixation support member defines an apex and each of the inflow and outflow portions of the fixation support member define legs of the V-shaped cross-sectional configuration, characterised in that the annular support is a continuous monolithic structure having a substantially V-shaped cross-sectional configuration for a longitudinal cross-section taken axially through the prosthesis in its expanded cross-sectional dimension, said structure consisting in a zigzag arrangement of support features (24, 26), in which the support features alternate between extending in the inflow and outflow directions along a circumferential path corresponding to the radially inner extent of the support structure.