Prosthesis delivery system

1. A prosthesis delivery system comprising:

a sheath defining an axial direction;

a plurality of tethers movable axially relative to the sheath;

a holder movable axially within the sheath, wherein the holder is a single tube configured to constrain radially the plurality of tethers; and

a collapsible prosthesis that is attached to at least one of the plurality of tethers, the collapsible prosthesis comprising a support structure comprising a plurality of apexes, wherein each tether in the plurality of tethers passes through a plurality of the apexes, and further wherein the prosthesis delivery system is configured to deliver the prosthesis to a target position in a living being.

2. The prosthesis delivery system of claim 1 , wherein each tether is movable axially within the holder.

3. The prosthesis delivery system of claim 1 , wherein a lead end of the holder is configurable to extend beyond a lead end of the sheath.

4. The prosthesis delivery system of claim 1 , wherein the holder is movable relative to the sheath between an extended position at which a lead end of the holder extends beyond. a lead end of the sheath and a retracted position at which the lead end of the sheath extends beyond the lead end of the holder.

5. The prosthesis delivery system of claim 1 , wherein each tether is configured to be controllable to detach the tether from a prosthesis attached to a lead end of the tether via the opposite end of the tether.

6. The prosthesis delivery system of claim 1 wherein the holder is a tube substantially coaxial with the sheath.

7. The prosthesis delivery system of claim 1 , wherein each tether comprises an unclosed loop of filiform material.

8. The prosthesis delivery system of claim 1 , wherein each tether comprises a hooked rib configured to he movable axially relative to the holder between a collapsed position at which the hooked rib is held by the holder in a deformed state and an expanded position at which the hooked rib extends radially beyond the holder.

9. The prosthesis delivery system of claim 1 , wherein, the holder constrains radially the tethers that are configured to attach to a collapsed end of a prosthesis so as to constrain radially the collapsed end of the prosthesis such that the collapsed end of the prosthesis fits within an opening into which the prosthesis is to be withdrawn at a lead end of the sheath.

10. The prosthesis delivery system of claim 1 , configured to be inserted into the vasculature of a mammal.

11. The prosthesis delivery system of claim 1 , wherein the plurality of tethers comprises three tethers.

12. The prosthesis delivery system of claim 1 , wherein the plurality of tethers comprises four tethers.

13. The prosthesis delivery system of claim 1 , wherein the target position is an organ of a living being.

14. The prosthesis delivery system of claim 13 , wherein the organ is a heart.

15. The prosthesis delivery system of claim 1 sized to deliver the prosthesis through the vasculature of the living being.

16. The prosthesis delivery system of claim 1 , wherein the support structure is collapsible from a fully expanded state into a compressed state by pulling on the apexes and can be drawn into the sheath when it is in the compressed state.

17. A method of collapsing a prosthesis to a collapsed state in a sheath using the prosthesis delivery system of claim 1 , the method comprising the steps of:

constraining radially with the holder the plurality of tethers, each of which is attached to the prosthesis; and

moving the tethers and the holder axially within the sheath such that the prosthesis is forced to collapse into the sheath and the holder is retracted into the sheath.

18. The method of claim 17 , further comprising the step of:

moving the tethers axially through the holder so as to bring a lead end of each tether attached to the prosthesis towards the holder so as to collapse partially the prosthesis.

19. A method of delivering a prosthesis collapsed in a sheath to a target position using the prosthesis delivery system of claim 1 , the method comprising the steps of:

retracting the sheath axially away from the prosthesis attached to the plurality of tethers such that the prosthesis partially expands from the collapsed state, wherein the tethers to which the prosthesis is attached are constrained radially by the holder that is movable axially within the sheath;

positioning in the target position the prosthesis that is in as partially collapsed state, attached to the tethers; and

relaxing the tension in the tethers.