Cryotherapeutic devices having integral multi-helical balloons and methods of making the same

1. A method of forming a balloon from an extruded integral shaft having a plurality of lumens along the shaft, the plurality of lumens including at least a first lumen and a second lumen, the method comprising:

positioning a distal portion of the shaft in a mold configured to define an outer surface of the balloon;

clamping a first end region of the distal portion with the mold;

rotating the mold relative to the shaft thereby forming a twisted distal portion of the shaft; and

forming the balloon along the twisted distal portion, wherein the balloon is configured to deliver therapeutically effective cryogenic cooling to a treatment site.

2. The method of claim 1 wherein the first lumen defines a first fluid passageway and the second lumen defines a second fluid passageway independent of the first fluid passageway.

3. The method of claim 1 wherein the extruded integral shaft includes a third lumen extending along the shaft, wherein the third lumen is positioned radially inward from the first and second lumens and configured to receive a guide wire.

4. The method of claim 1 wherein forming the balloon comprises plastically enlarging the twisted distal portion of the first and second lumens.

5. The method of claim 1 wherein forming the twisted distal portion includes twisting at least a section of the shaft distal to the clamped first end region.

6. The method of claim 1 wherein the balloon includes an outer surface that is substantially continuous at transverse cross-sections of the balloon.

7. The method of claim 1 wherein the twisted distal portion terminates at a proximal end region of the balloon.

8. A method of forming an inflatable body from an extruded integral shaft having at least first and second lumens extending along the shaft substantially parallel to each other for at least a portion of the shaft, the method comprising:

positioning a distal portion of the shaft in a mold configured to define an outer surface of the inflatable body;

clamping a first end region of the distal portion with the mold;

rotating the mold relative to the shaft thereby twisting a distal portion of the shaft such that the first lumen has a first helical portion and the second lumen has a second helical portion intertwined with the first helical portion; and

plastically enlarging the intertwined first and second helical portions to form the inflatable body, wherein the inflatable body is configured to deliver therapeutically effective cryogenic cooling to a treatment site.

9. The method of claim 8 wherein the shaft further comprises a polymeric material, the shaft having a guide wire lumen positioned centrally between the at least first and second lumens, and wherein:

plastically enlarging the intertwined first and second helical portions comprises heating, pressurizing, and stretching the distal portion of the shaft; and

the method further comprises—

supporting the distal portion of the shaft with a mandrel extending through the guide wire lumen during twisting of the distal portion,

clamping the shaft at first and second end regions of the distal portion such that the first and second helical portions extend between the first and second end regions and the first and second lumens extend substantially straight proximally from the distal portion, and

applying heat to the distal portion as the distal portion of the shaft is twisted.

10. The method of claim 8 wherein the shaft has at least four lumens extending at least substantially parallel to one another along the shaft, and wherein the first and second lumens are two of the at least four lumens.

11. The method of claim 8 wherein the shaft comprises a guide wire lumen extending between the first and second lumens.

12. The method of claim 11 wherein twisting the distal portion of the shaft comprises:

supporting the shaft with a mandrel removably disposed within the guide wire lumen in at least the distal section;

clamping the shaft at a first end region of the distal portion; and

twisting a second end region of the distal portion, wherein a clamp pressure at the first end region is configured to retain the first end region during twisting without binding the shaft to the mandrel.

13. The method of claim 8 wherein plastically enlarging the first and second helical portions of the first and second lumens comprises:

stretch blow molding at least a length of the distal portion to form the inflatable body; and

maintaining pressure within the first and second lumens during the stretch blow molding.

14. The method of claim 8 wherein plastically enlarging the first and second helical portions of the first and second lumens comprises forming an inflatable body having a length of approximately 8-15mm and an outer diameter of approximately 3-8 mm in a deployed state.

15. The method of claim 8 wherein plastically enlarging the first and second helical portions of the first and second lumens comprises forming an inflatable body having an outer diameter of less than 2 mm in a delivery state.