Heart valve prosthesis

1. A heart valve prosthesis comprising:

a support structure comprising a framework deformable between an expanded state and a compressed state and vice versa, said support structure having a radial dimension when in the expanded state and a smaller radial dimension when in the compressed state, said support structure comprising smoothly curved ribs; and

a flow-control structure, supported by the support structure, for permitting blood flow downstream in a first direction, defining an axial direction of the prosthesis, and for restricting blood flow in an upstream direction opposite to the first direction,

wherein the flow-control structure comprises at least three leaflets each having a radially outer edge so as to define a profile, each leaflet having an associated smoothly curved rib,

each associated smoothly curved rib having a curve to match the profile of the radially outer edge of their associated leaflet and to which each said individual smoothly curved rib is attached,

wherein the support structure further comprises a first set of petal-like portions that protrude beyond the flow-control structure axially in the upstream direction in which the flow-control structure restricts blood flow opposite to the first direction in which the flow-control structure permits blood flow, and protrude radially further than the flow-control structure,

wherein at least one end of the support structure comprises a plurality of apexes of the framework,

wherein the support structure is collapsible from the fully expanded state into the compressed state by pulling on the apexes, to enable it to be drawn into a sheath in the compressed state, the sheath having an inner radial dimension smaller than the radial dimension of the support structure in the expanded state, and

wherein the smoothly curved ribs are a single bent wire.

2. A prosthesis according to claim 1 , wherein the support structure comprises a second set of petal-like portions that protrude beyond the flow-control structure axially in the downstream first direction, and protrude radially further than the flow-control structure.

3. A prosthesis according to claim 2 , wherein the first set of petal-like portions and the second set of petal-like portions are configured so as to clamp the structure in position.

4. A prosthesis according to claim 1 , wherein loops are provided at the apexes for attaching members for pulling thereon for collapsing the heart valve.

5. A prosthesis according to claim 1 , further comprising clefts in the support structure between apexes, wherein at least one of the clefts is a deep cleft having a length in the axial direction greater than the average radius of the support structure.

6. A prosthesis according to claim 5 , wherein the length in the axial direction of the deep cleft is greater than the average diameter of the support structure.

7. A prosthesis according to claim 5 , comprising at least three deep clefts.

8. A prosthesis according to claim 1 , wherein the support structure is elastically deformable, and is self-expanding from the compressed state to the expanded state.