Delivery catheter that controls foreshortening of ribbon-type prostheses and methods of making and use

1. A vascular prosthesis assembly comprising:

a delivery device comprising:

an elongate member; and

a sheath over at least a portion of the elongate member;

a vascular prosthesis comprising a self expanding helical portion, the helical portion placeable in a contracted, delivery state and an expanded, deployed state, the vascular prosthesis defining a central axis;

the vascular prosthesis mounted on the elongate member in the contracted, delivery state with at least the helical portion located between the sheath and the elongate member;

the helical portion comprising a continuous helical element extending along a helical path along the central axis in an axial direction and extending along the helical path completely around the central axis in a rotary direction in both the contracted, delivery state and the expanded, deployed state;

the helical portion having a first wrap angle around said central axis and a first axial length along said central axis when in the contracted, delivery state;

the helical portion having a second wrap angle around said central axis and a second axial length along said central axis when in the expanded, deployed state; and

the first axial length being equal to the second axial length and the first wrap angle being equal to the second wrap angle.

2. The assembly according to claim 1 , wherein the elongate member comprises:

an outer surface;

a helical ledge on the outer surface comprising at least one full turn; and

the helical ledge having a third wrap angle equal to the first wrap angle; and wherein:

the helical portion has a leading, distal edge and a trailing, proximal edge, the trailing, proximal edge contacting the helical ledge to aid in placement of the helical portion on the elongate member and to help maintain the helical portion in position relative to the elongate member when the sheath is moved proximally relative to the elongate member.

3. The assembly according to claim 1 , wherein the vascular prosthesis comprises one self expanding helical portion.

4. The assembly according to claim 1 , wherein the expanded, deployed state is a fully expanded state of the helical portion.

5. The assembly according to claim 1 , wherein:

the vascular prosthesis further comprises a self expanding anchor ring disposed distal of the helical portion; and

the elongate member further comprises means for engaging the self expanding anchor ring to help prevent axial translation of the vascular prosthesis during proximal retraction of the sheath.

6. The assembly according to claim 5 , wherein the means for engaging comprises a polymer layer that has been treated to enhance frictional engagement with the self expanding anchor ring.

7. The assembly according to claim 1 , further comprising a balloon disposed adjacent to a distal end of the elongate member.

8. The assembly according to claim 1 , further comprising means for engaging a wall of a vessel of a patient during deployment of the vascular prosthesis to help prevent axial displacement of the delivery device.

9. A method for assembling a vascular prosthesis assembly comprising:

determining a target expanded diameter for a vascular prosthesis at a target site within a vessel of a patient;

selecting a vascular prosthesis defining a central axis and having a self expanding helical portion;

the helical portion comprising a continuous helical element extending along a helical path along the central axis in an axial direction and extending along the helical path completely around the central axis in a rotary direction in both the contracted, delivery state and the expanded, deployed state;

selecting a first pitch;

wrapping the vascular prosthesis onto an elongate member of a delivery device at the first pitch with the helical portion placed against the elongate member in a radially contracted state, the helical portion having a first axial length along said central axis and a first wrap angle around said central axis when in the contracted, delivery state;

the helical portion having a second axial length along said central axis, a second pitch and a second wrap angle around said central axis when self expanded to the target expanded diameter;

the first pitch selecting step carried out so that the first axial length is equal to the second axial length and the first wrap angle is equal to the second wrap angle; and

placing a sheath over at least a portion of the helical portion.

10. The method according to claim 9 , wherein:

the selecting step further comprises selecting an elongate member having a substantially continuous helical ledge extending outwardly from an outer surface thereof, the helical ledge having a third wrap angle equal to the first wrap angle; and

the wrapping step further comprises placing a trailing, proximal edge of the vascular prosthesis against the helical ledge.

11. A method for using a vascular prosthesis assembly comprising:

selecting a vascular prosthesis assembly made according to the method of claim 9 ;

placing a distal portion of the vascular prosthesis assembly at the target site;

removing the sheath from at least the helical portion to permit the helical portion of the vascular prosthesis to expand towards the target expanded diameter; and

removing the delivery device from the patient leaving the vascular prosthesis at the target site.

12. The method according to claim 11 , wherein the sheath removing step is carried out by pulling the sheath proximally relative to the vascular prosthesis.

13. The method according to claim 9 , wherein the wrapping step comprises wrapping the helical portion at least twice around the axis to create first and second complete helical turns, the helical turns having lateral edges.

14. The method according to claim 13 , wherein the selecting step is carried out so that the lateral edges of the first and second helical turns are not attached to one another.

15. The assembly according to claim 1 , wherein the helical portion extends at least twice around the central axis to define at least first and second complete helical turns.

16. The assembly according to claim 15 , wherein the helical portion comprises:

first and second edges extending in an axial direction and a rotary direction; and wherein:

the first and second edges of the first helical turn are disconnected from the first and second edges of the second helical turn.