Enhanced flexibility neurovascular catheter
A catheter is provided comprising localized regions of modified flexibility. The regions of modified flexibility may comprise a softened inner liner, for example softened via stretching the inner liner or disposing a plurality of holes in the inner liner, to modify the bending stiffness and/or tensile stiffness of the catheter. The catheter may further include an axially extending filament that at least partially overlaps the softened portion of the inner liner. The axially extending filament may include an anchoring section to anchor the at least one axially extending filament in a section of the catheter that includes the helical coil.
1. A method of making a flexible distal zone on a neurovascular catheter, having an elongate tubular body with a distal end, comprising:
dip coating a removable mandrel to form a tubular inner liner on the mandrel;
softening a portion of the tubular inner liner on the mandrel, softening comprising applying tension axially to the portion of the tubular inner liner such that the tubular inner liner comprises a stretched portion and an unstretched portion after softening the portion of the tubular inner liner;
applying a helical coil to an outside of the inner liner;
positioning a plurality of tubular segments over the helical coil, the plurality of segments having durometers that decrease in a distal direction;
heating the tubular segments to form the flexible distal zone on the neurovascular catheter; and
removing the mandrel.
2. The method of claim 1 , wherein the softened portion of the tubular inner liner comprises a distal 15 mm to 20 mm of the tubular inner liner.
3. The method of claim 1 , further comprising achieving a thickness of the softened portion of the tubular inner liner of 0.00025 inches to 0.00075 inches.
4. The method of claim 1 , further comprising aligning one or more polymer chains of the stretched portion of the tubular inner liner relative to one another in a similar or substantially similar direction as the applied tension.
5. The method of claim 1 , further comprising coating the tubular inner liner with a tie layer.
6. The method as in claim 5 , wherein the tie layer comprises polyurethane.
7. The method as in claim 5 , wherein the tie layer has a wall thickness of no more than 0.005 inches.
8. The method as in claim 5 , wherein the tie layer extends along at least a most distal 20 cm of the neurovascular catheter.
9. The method as in claim 5 , further comprising positioning at least one axially extending tensile strength enhancing filament over the tie layer.
10. The method as in claim 9 , further comprising overlapping the softened portion of the tubular inner liner with the at least one axially extending filament.
11. The method of claim 9 , wherein the at least one axially extending filament includes an anchoring section, such that the method further comprises anchoring the at least one axially extending filament in a section of the catheter that includes the helical coil.
12. The method as in claim 9 , wherein the filament extends along at least a most distal 15 cm of a length of the catheter.
13. The method as in claim 9 , wherein the filament extends along at least a most distal 20 cm of a length of the catheter.
14. The method as in claim 9 , wherein the filament comprises multiple fibers.
15. The method of claim 1 , wherein the plurality of tubular segments form a proximal section having a proximal end and a distal end and a durometer equal to or greater than 65D at all points along a length from the proximal end to the distal end of the proximal section, a distal section having a proximal end and a distal end and a durometer equal to or less than 35D at all points along a length extending from the proximal end to the distal end of the distal section, and a transition section extending from the distal end of the proximal section to the proximal end of the distal section, the transition section comprising at least two tubular segments of the plurality of tubular segments and having a durometer less than 65D and greater than 35D at all points along a length extending from the distal end of the proximal section to the proximal end of the distal section, the transition section being shorter in length than the proximal section and shorter in length than the distal section.
16. The method as in claim 15 , wherein the transition section comprises at least three tubular segments of the plurality of tubular segments.
17. The method as in claim 15 , wherein the distal section is at least twice as long as the transition section.
18. The method as in claim 1 , wherein removing the mandrel step includes axially elongating the mandrel.
19. The method as in claim 1 , wherein positioning segments on the helical coil comprises positioning at least seven tubular segments of the plurality of tubular segments on the helical coil.
20. The method as in claim 1 , wherein positioning segments on the helical coil comprises positioning at least nine tubular segments of the plurality of tubular segments on the helical coil.
21. The method as in claim 1 , wherein the tubular inner liner comprises PTFE.
22. The method as in claim 1 , wherein the coil comprises a shape memory material.
23. The method as in claim 22 , wherein the coil comprises Nitinol.
24. The method as in claim 23 , wherein the Nitinol comprises an Austenite state at body temperature.
25. The method as in claim 1 , wherein the stretched portion is on a distal portion of the tubular inner liner.
26. The method as in claim 1 , wherein softening the portion of the inner liner comprises stretching the portion of the tubular inner liner 50% to 90% of a pre-stretch length.