Variable stiffness steering mechanism for catheters

• US 9,795,765 B2
• Filed: 04/11/2011
• Issued: 10/24/2017
• Est. Priority Date: 04/09/2010
• Status: Active Grant

• Current Assignee: ST JUDE MEDICAL INTERNATIONAL HOLDING S. R.L.
• Original Assignee: ST JUDE MEDICAL INTERNATIONAL HOLDING S. R.L.
• Inventors: Romoscanu, Alexandre
• Primary Examiner(s): TOWA, RENE T
• Application Number:
  US13/084,155
• Publication Number:
  US 20110251519A1
• Time in Patent Office: 2,388 Days
• Field of Search: 600433-435, 600585, 60416413
• CPC Class Codes: A61B 1/00078 with stiffening means
• CPC Class Codes: A61B 1/0055 Constructional details of insertion parts, e.g. vertebral elements
• CPC Class Codes: A61M 2025/0046 Coatings for improving slidability
• CPC Class Codes: A61M 2025/0059 having means for preventing the catheter, sheath or lumens from collapsing due to outer forces, e.g. compressing forces, or caused by twisting or kinking
• CPC Class Codes: A61M 25/0013 Weakening parts of a catheter tubing, e.g. by making cuts in the tube or reducing thickness of a layer at one point to adjust the flexibility
• CPC Class Codes: A61M 25/0051 made from fenestrated or weakened tubing layer
• CPC Class Codes: A61M 25/0052 Localized reinforcement, e.g. where only a specific part of the catheter is reinforced, for rapid exchange guidewire port
• CPC Class Codes: A61M 25/0053 having a variable stiffness along the longitudinal axis, e.g. by varying the pitch of the coil or braid
• CPC Class Codes: A61M 25/0054 with regions for increasing flexibility
• CPC Class Codes: A61M 25/0138 having flexible regions as a result of weakened outer material, e.g. slots, slits, cuts, joints or coils
• CPC Class Codes: A61M 25/0147 with movable mechanical means, e.g. pull wires

Abstract

A catheter assembly including a tapered steering spine having a varying stiffness along an axial length. The tapered steering spine is tailored to provide increasing flexibility from proximal to distal in a way that makes the bend radius more uniform along the length of the steering section. In one embodiment, the tapered steering spine includes structures on adjacent rings that engage with each other when the steering section is flexed to limit the minimum bend radius to a predetermined minimum and which enhances the torsional rigidity of the steering section regardless of the degree of flexure of the steering section. The limited bend radius can prevent excessive bending of components such as fiber optics. The enhanced torsional rigidity can negate the need for torque braid in the section of the catheter shaft that surrounds the tapered steering spine.

Claims

1. A tapered steering spine for a catheter system, comprising:

a unitary body having a proximal end and a distal end and defining a longitudinal axis, said unitary body including a plurality of axially spaced rings that extend from a continuous and straight spine portion that runs along a same side of the tapered steering spine, said spine portion being parallel to said longitudinal axis,

the axially spaced rings defining a plurality of slots along said length of said unitary body, each slot having a tangential dimension relative to said outer surface of said unitary body in a direction substantially orthogonal to said longitudinal axis, said tangential dimension of a first of said respective slots being greater than said tangential dimension of a second of said respective slots, said first of said respective slots being distal to said second of said respective slots; and

a deflecting tab proximate the distal end of the tapered steering spine, said tab comprising first and second legs that are cantilevered from a distal end of the unitary body and extend proximally, wherein the proximal end of the legs are joined by an apex portion; and

a stop portion that extends proximally from the distal end of the unitary body between the first and second legs, wherein a gap is defined between the apex portion and the proximal end of the stop portion, through which a hooked distal end of a pull wire is inserted.

2. The tapered steering spine of claim 1, wherein the pull wire is diametrically opposed to said spine portion to control tip deflection.

3. The tapered steering spine of claim 2 wherein said pull wire is mechanically fastened at said distal end of said unitary body.

4. The tapered steering spine of claim 1 wherein said tab is adapted to deflect inwardly in unison with the distal end portion of the pull wire upon insertion into a catheter shaft, said tab exerting a negligible reaction force on said catheter shaft.

5. The tapered steering spine of claim 1 further comprising a high lubricity coating that extends over at least a portion of said unitary body.

6. The tapered steering spine of claim 5 wherein said high lubricity coating is exclusive of portions of said unitary body near said proximal and distal ends to provide bonding surfaces for fixation of said unitary body to a catheter shaft.

7. A method of making a tapered steering spine for a catheter system, comprising:

providing a unitary tube of a material defining a longitudinal axis;

forming a plurality of slots in said unitary tube that are spaced axially along said length of said unitary tube to define a plurality of axially spaced rings that extend from a continuous and straight spine portion that runs along a same side of the tapered steering spine and in a direction that is lateral to said longitudinal axis, said axially spaced rings including structures that slidingly interlock with each other across a range of deflection of said continuous spine portion from a substantially straight orientation through a maximum deflection orientation to provide torsional rigidity while providing flexibility in a direction lateral to said longitudinal axis, wherein each of the axially spaced rings includes the structures that slidingly interlock with each other on a second side of each of the axially spaced rings that is diametrically opposed to the first side;

providing a deflecting tab proximate a distal end of the tapered steering spine, the deflecting tab comprising first and second legs that are cantilevered from a distal end of the unitary tube and extend proximally, wherein the proximal end of the legs are joined by an apex portion;

providing a stop portion that extends proximally from the distal end of the unitary body between the first and second legs, wherein a gap is defined between the apex portion and the proximal end of the stop portion;

coating said unitary tube with a high lubricity coating; and

affixing a catheter shaft to said unitary tube.

8. The method of making a tapered steering spine according to claim 7, wherein slots in said unitary tube are formed using laser cutting or electroerosion wire cutting.

9. The method of making a tapered steering spine according to claim 8, wherein said unitary tube provided in said step of providing is made of a nickel-titanium alloy.

10. The method of making a tapered steering spine according to claim 8, wherein said unitary tube provided in said step of providing is made of a nickel-cobalt alloy.

11. The method of making a tapered steering spine according to claim 8, wherein said unitary tube provided in said step of providing is made of spring steel.

12. The method of making a tapered steering spine according to claim 8, wherein said high lubricity coating provided in said step of coating does not extend over a length of said unitary tube near said proximal and distal ends of said unitary tube to provide bonding surfaces for affixing said catheter shaft to said unitary tube.

13. The method of making a tapered steering spine according to claim 8, wherein said high lubricity coating provided in said step of coating contains polytetrafluoroethylene, fluorinated ethylene propylene, or poly (p-xylylene) polymers.

14. A tapered steering spine for a catheter system, comprising:

a unitary body of generally tubular shape having a proximal end and a distal end and defining a longitudinal axis, said unitary body including a plurality of axially spaced rings that extend from a continuous and straight spine portion that runs along a same side of the tapered steering spine, said spine portion being substantially parallel to said longitudinal axis;

the plurality of axially spaced rings defining a plurality of slots along said length of said unitary body, each slot having a tangential dimension on said surface of said unitary body, said tangential dimension of said respective slots increasing from said proximal end to said distal end of said unitary body to provide increasing flexibility of said unitary body from said proximal end to said distal end;

a single pull wire fastened at said distal end of said unitary body and diametrically opposed to said spine portion to control tip deflection from a substantially straight orientation through a maximum deflection orientation, wherein the single pull wire is fastened to a deflecting tab located proximate to the distal end of the tapered steering spine, the deflecting tab comprising first and second legs that are cantilevered from a distal end of the unitary tube and extend proximally, wherein the proximal end of the legs are joined by an apex portion; and

a stop portion that extends proximally from the distal end of the unitary body between the first and second legs, wherein a gap is defined between the apex portion and the proximal end of the stop portion, through which a hooked distal end of the single pull wire is inserted.

15. A steering spine for a catheter system, comprising:

a body having a proximal end and a distal end and defining a longitudinal axis, said body including a plurality of axially spaced rings that extend from a continuous spine portion that runs along a same side of the tapered steering spine, said continuous spine portion being parallel to said longitudinal axis, said continuous spine portion and said longitudinal axis being located in a steering plane of said steering spine, said axially spaced rings defining a plurality of slots along said length of said body, said axially spaced rings including structures that engage with complementary structures of adjacent rings, wherein the spine portion runs along a first side of each of the axially spaced rings, wherein each of the axially spaced rings includes the structures that engage with complementary structures on a second side of each of the axially spaced rings that is diametrically opposed to the first side, said structures and complementary structures being dimensioned to limit said minimum bend radius of said body when said body is flexed in a lateral direction away from said spine portion;

wherein said body includes one or more laterally flexible regions, each region including at least one flexure, a first of said at least one flexure being in line with said continuous spine portion, said first flexure defining a perpendicular axis that is perpendicular to said longitudinal axis, said perpendicular axis being substantially in said steering plane;

a deflecting tab proximate the distal end of the steering spine, comprising first and second legs that are cantilevered from a distal end of the unitary body and extend proximally, wherein the proximal end of the legs are joined by an apex portion; and

a stop portion that extends proximally from the distal end of the unitary body between the first and second legs, wherein a gap is defined between the apex portion and the proximal end of the stop portion, through which a hooked distal end of a pull wire is inserted.

16. The steering spine of claim 15, wherein said at least one flexure includes a second flexure that is substantially at the same axial location as and in diametric opposition with said first flexure, said perpendicular axis passing through said first flexure and said second flexure.

17. The steering spine of claim 15, wherein at least one of said one or more laterally flexible regions includes an offset flexure pair that is rotationally offset with respect to said first flexure, the flexures of said offset flexure pair being in diametric opposition with each other.

18. The steering spine of claim 17 wherein said offset flexure pair is rotationally offset with respect to said first flexure by 90°

.

19. The tapered steering spine of claim 15, wherein:

the distal end portion of the pull wire is coupled to a proximal end of the deflecting tab; and

a passage is defined through a wall of the body that borders a proximal end of the apex portion, the passage configured to enable a portion of the hooked distal end of the pull wire to pass through as the deflecting tab and the pull wire are deflected inward.