CATHETER SHAFT AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS
Catheter shafts and associated devices, systems, and methods are disclosed herein. A representative catheter in accordance with an embodiment of the disclosure includes a generally tubular outer structure and an inner structure surrounded by the outer structure. The inner structure surrounds a catheter lumen. The inner structure includes over-lapping edges such that, when the catheter is bent along its longitudinal axis, the over-lapping edges move relative to one another.
This application is a continuation of U.S. patent application Ser. No. 16/062,877, filed on Jun. 15, 2018, and titled “CATHETER SHAFT AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS,” which is a 35 U.S.C. § 371 U.S. National Phase application of International Patent Application No. PCT/US2016/067628, filed on Dec. 19, 2016, and titled “CATHETER SHAFT AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS,” which claims priority to U.S. Provisional Application No. 62/269,372, filed on Dec. 18 2015, and titled “CATHETER SHAFT AND ASSOCIATED DEVICES, SYSTEMS, AND METHODS,” each of which is herein incorporated by reference in its entirety.
TECHNICAL FIELDThe present technology is directed generally to catheters. More specifically, the present technology relates to catheter shaft construction.
BACKGROUNDA wide variety of medical devices have been developed for intravascular use. Catheters, for example, are commonly used to facilitate navigation through and/or treatment within the anatomy of a patient. Because of the compromises involved between the mechanical, biological and chemical requirements for catheter performance, many existing catheters are a composite of two or more different materials in order to take advantage of the unique properties of the different materials. For example, a common composite catheter construction includes (1) an outer jacket made of a material that provides longitudinal rigidity to resist kinks and (2) a chemically-inert inner surface liner (typically a fluoropolymer) having a low coefficient of friction to ease delivery of one or more components through the shaft lumen. Inner liner materials, however, are significantly less flexible than the materials used for the outer jacket, and thus greatly affect the flexibility of the composite catheter shaft. For example, the modulus of elasticity of materials commonly used as inner surface liners is about 70,000 psi, while the modulus of elasticity for common outer jacket material(s) is about 2,900 psi. Although some conventional catheters are made with low durometer polymers, (e.g., extremely soft), such catheters generally have little kink resistance. Accordingly, a need exists for a kink-resistant catheter shaft with improved flexibility.
The present technology is directed to catheters and associated methods of manufacture. Specific details of several embodiments of catheter devices, systems, and methods in accordance with the present technology are described below with reference to
The size of the lumen 104 can vary depending on the desired characteristics of the shaft 100. For example, in some embodiments the shaft 100 can have an inner diameter (e.g., lumen diameter) between about 0.01 inches and about 0.5 inches, and in some embodiments between about 0.2 inches and about 0.4 inches. Although the shaft 100 shown in
As shown in
As shown in the enlarged, cross-sectional view of the shaft 100 in
The overlapping region 122 includes an outer portion 124 of the strip 113 and an inner portion 126 of the strip 113 positioned radially inwardly of the outer portion 124, as shown in
The outer portion 124 can have an outer surface 124a facing radially outwardly and an inner surface 124b opposite the outer surface 124a and facing the lumen 104. The inner portion 126 has an outer surface 126a facing radially outwardly and an inner surface 126b opposite the outer surface 126a and facing the lumen 104. In the embodiment shown in
The catheter shaft 100 of the present technology provides several advantages over existing catheters. For example, the helical or spiral geometry of the inner structure 112, as well as the inner structure's 112 interrupted bonding with the outer structure 114, greatly increases the overall flexibility of the inner structure 112 as compared to a continuous tube made of the same material and having the same thickness. As such, the catheter shaft 100 of the present technology is significantly more flexible than conventional catheter shafts. For example, in some embodiments, the bending stiffness of the shaft 100 may be 25% less than that of a comparable composite catheter shaft (e.g., a shaft having the same outer structure and an inner structure made of a continuous tube made of the same material, having the same thickness and the same inner diameter). In some embodiments, the bending stiffness may be between about 30% and about 60% less than that of a comparable composite catheter. In some embodiments, the inner structure may provide less than about 50%, and in other embodiments less than about 25%, of the total bending stiffness of the composite catheter. Such improved flexibility is most dramatic in larger diameter catheters (assuming wall thickness does not vary based on diameter), such as guide catheters. For a given bend radius and wall thickness, the walls of catheters with a large ID are subject to greater strain than the walls of small ID catheters.
II. Selected Methods of ManufactureIn one embodiment of manufacturing a catheter shaft in accordance with the present technology, a strip of material is provided. In some embodiments, the strip can be made of the desired inner structure material, such as PTFE. The strip can be a PTFE tape, a longitudinally-cut PTFE tube (described in greater detail below), or other polymer structures in a strip form. For example, in some embodiments, the strip is constructed by splitting the wall of a polymer tube along a helical path about the tube's longitudinal axis. In any of the foregoing embodiments, the strip of material may be wound around a mandrel. In a representative embodiment, the strip is wound from the proximal end to the distal end such that the strips' free edges or steps face distally within the lumen. The strip can be wound in this manner to provide a smoother path through the lumen for one or more devices delivered therethrough. In other embodiments, the strip can be wound from its distal end to its proximal end.
The strip can be wound to have a desired pitch angle (e.g., the distance between successive turns of the strip). The pitch angle affects the flexibility of the resulting wound structure since the pitch angle affects the amount of overlapping regions per unit length of the shaft, which in turn affects the width of bonded strip that (eventually) undergoes bending stress. In some embodiments, the maximum pitch angle to achieve 50% coverage can be governed by the equation max pitch angle=tan−1(2π/w), and the minimum pitch angle to achieve no overlap can be governed by the equation min pitch angle=tan−1(π/w), where D is the desired inner diameter for the shaft and w is the width of the strip of material.
Once the strip is wound around the mandrel as desired, a tube of material (e.g., a polymer commonly used for the outer structure) is positioned over the wound strip. Next, a heat-shrinkable tube (e.g., a fluoropolymer) can be positioned over the tube. The assembly (e.g., the mandrel, the wound strip, the tube, and the heat-shrinkable tube) is then gradually heated from its distal end to its proximal end (or vice versa) to fuse the tube with the strip. The amount of calories absorbed by the assembly, and the rate at which the calories are transferred to the mandrel, will depend on the geometry of the assembly (e.g., the length of the assembly, the diameter of the assembly, the thickness of the materials used, etc.). The temperature can be high enough to shrink the heat-shrinkable tube and raise the temperature of the tube material above its glass transition temperature (e.g., between about 380° F. and about 440° F.), yet low enough so as not to affect the durometer of the tube material and affect its resultant molecular weight (thereby changing the mechanical properties of the resultant outer structure). Also, the duration of heat application can be monitored to avoid for applying too high of a temperature for too long, which may cause the tube material to flow between the overlapping portion of the strip and into the lumen thereby raising the coefficient of friction within the catheter lumen. Additionally, the mandrel material can be chosen to provide a heatsink to quickly remove heat from the melted tube and freeze it before the tube material flows between the overlaps. For example, in some embodiments the mandrel is a steel tube, and the wall thickness of the tube can be varied to add or subtract heat transfer rate. Once the assembly has cooled, the heat shrinkable tube can be removed and the newly-formed composite shaft can be removed from the mandrel.
In any of the devices and methods disclosed herein, the inner structure is formed of a polymer tube (e.g., a PTFE tube) that is cut into strips in a direction parallel to the longitudinal axis of the tube. The width of the strip is then (πD) where D is the tubing diameter. The thickness of the strip is the wall thickness of the tubing. Another method of creating strip from tubing is to slice the tube helically. The maximum width of the strip is then (πD)/(tanθ), where θ is the angle of the helix from the tube axis.
Before cutting the tube, the tube can be etched on only its exterior surface to increase the coefficient of friction between the exterior surface of the tube and other polymers (i.e., the outer structure material) that may be bonded to the exterior surface of the tube. The tubing may be etched with a strong base (e.g., sodium hydroxide, potassium hydroxide, sodium/ammonia, etc.) by immersing the tube in liquid etchant as an on-line process during extrusion, or as a batch process after extrusion. The latter method includes plugging the ends of the PTFE tubing before immersion or otherwise keeping the open ends out of the liquid etchant. This way, only one surface of the polymer tubing material is etched while the other surface is not etched.
III. Additional EmbodimentsThe following examples are illustrative of several embodiments of the present technology:
-
- 1. A catheter, comprising:
- a generally tubular outer structure; and
- an inner structure surrounded by the outer structure and that surrounds a catheter lumen.
- 2. The catheter of example 1, wherein the inner structure includes over-lapping edges.
- 3. The catheter of example 1 or example 2, wherein the inner structure is non-continuous in a longitudinal direction.
- 4. The catheter of any one of examples 1-3, wherein the inner structure has freely sliding interfaces with itself.
- 5. The catheter of any one of examples 1-4, wherein the inner structure provides less than 50% of the total bending stiffness of the catheter.
- 6. The catheter of any one of examples 1-5, wherein the inner structure has portions that slide tangentially during bending of the catheter.
- 7. A catheter, comprising
- a generally tubular outer structure, the outer structure having an outer surface and an inner surface; and
- an inner structure surrounded by the outer structure, the inner structure having a relaxed state and a stressed state, and wherein—
- the inner structure is composed of a strip of material that is helically wound around a central longitudinal axis to form a generally tubular member defining a lumen, wherein the strip has an outer surface and an inner surface,
- a first portion of the strip overlaps a second portion of the strip along the longitudinal axis of the strip,
- only a portion of the outer surface is bonded to the inner surface of the outer structure, and
- when the catheter is bent along its longitudinal axis, the second portion is configured to slide relative to the first portion.
- 8. The catheter of example 7, wherein the inner structure includes over-lapping edges.
- 9. The catheter of example 7 or example 8, wherein the inner structure is non-continuous in a longitudinal direction.
- 10. The catheter of any one of examples 7-9, wherein the inner structure provides less than 50% of the total bending stiffness of the catheter.
- 11. The catheter of any one of examples 7-10, wherein the first portion slides tangentially relative to the second portion during bending of the catheter.
- 12. The catheter of any one of examples 7-11, wherein the strip of material is formed from a polymer tube that has been cut in a direction parallel to a longitudinal axis of the tube.
- 13. The catheter of any one of examples 7-11, wherein the strip of material is formed from a polymer tube that has been cut in a helical direction.
- 14. The catheter of any one of examples 7-13, wherein the polymer tube has an etched exterior surface and an inner surface that is not etched.
- 14. The catheter of any one of examples 7-13, wherein the polymer tube is a PTFE tube.
Many embodiments of the present technology can be used to access or treat targets located in tortuous and narrow vessels, such as certain sites in the neurovascular system, the pulmonary vascular system, the coronary vascular system, and/or the peripheral vascular system. The catheter shaft of the present technology can also be suited for use in the digestive system, soft tissues, and/or any other insertion into an organism for medical uses.
It will be appreciated that specific elements, substructures, advantages, uses, and/or other features of the embodiments described with reference to
Claims
1. A catheter, comprising:
- a strip of material wound about a longitudinal axis to define a catheter lumen, wherein the strip of material includes edges that overlap in a radial direction relative to the longitudinal axis, wherein the overlapping edges extend entirely circumferentially about the longitudinal axis, and wherein the over-lapping edges are not adhered together.
2. The catheter of claim 1 wherein the strip of material has a first region and a second region, wherein adjacent ones of the edges overlap by a first distance in a direction parallel to the longitudinal axis in the first region, wherein adjacent ones of the edges overlap by a second distance in the direction parallel to the longitudinal axis in the second region, and wherein the first distance is different than the second distance.
3. The catheter of claim 1 wherein adjacent ones of the edges overlap by an overlap distance, and wherein the overlap distance varies along the longitudinal axis.
4. The catheter of claim 1 wherein the strip of material is wound about the longitudinal axis to have a pitch, wherein the pitch varies along the longitudinal axis such that the strip of material defines a first region having a first stiffness and a second region having a second stiffness, and wherein the first stiffness is different than the second stiffness.
5. The catheter of claim 1 wherein the catheter further comprises a tubular structure surrounding the strip of material.
6. The catheter of claim 5 wherein the strip of material has an inner surface defining the catheter lumen and an outer surface opposite the inner surface, and wherein the tubular structure is bonded to only a portion of the outer surface.
7. The catheter of claim 5 wherein the tubular structure is an elongated polymer tube.
8. The catheter of claim 1 wherein the strip of material is formed from a polymer tube that has been cut in a direction parallel to a longitudinal axis of the polymer tube.
9. The catheter of claim 1 wherein the strip of material is formed from a polymer tube that has been cut in a helical direction about a longitduinal axis of the polymer tube.
10. The catheter of claim 1 wherein the strip of material has an inner surface defining the catheter lumen and an outer surface opposite the inner surface, wherein the outer surface is etched, and wherein the inner surface is not etched.
11. The catheter of claim 1 wherein the strip of material is formed from a PTFE tube.
12. A catheter, comprising:
- a strip of material wound about a longitudinal axis, wherein the strip of material has freely sliding interfaces with itself in a radial direction relative to the longitudinal axis, and wherein the freely sliding interfaces extend entirely circumferentially about the longitudinal axis.
13. The catheter of claim 12 wherein the strip of material has a first region and a second region, wherein the strip of material has edges that overlap at the freely sliding interfaces, wherein adjacent ones of the edges overlap by a first distance in a direction parallel to the longitudinal axis in the first region, wherein adjacent ones of the edges overlap by a second distance in the direction parallel to the longitudinal axis in the second region, and wherein the first distance is different than the second distance.
14. The catheter of claim 12 wherein the strip of material has edges that overlap at the freely sliding interfaces, wherein adjacent ones of the edges overlap by an overlap distance at the freely sliding interfaces, and wherein the overlap distance varies along the longitudinal axis.
15. The catheter of claim 12 wherein the strip of material is wound about the longitudinal axis to have a pitch, wherein the pitch varies along the longitudinal axis such that the strip of material defines a first region having a first stiffness and a second region having a second stiffness, and wherein the first stiffness is different than the second stiffness.
16. The catheter of claim 1 wherein the catheter further comprises a tubular structure surrounding the strip of material, wherein the strip of material has an inner surface defining a catheter lumen and an outer surface opposite the inner surface, and wherein the tubular structure is bonded to only a portion of the outer surface.
17. A catheter, comprising
- a strip of material wound about a longitudinal axis, wherein the strip of material has inner portions and outer portions that overlap in a radial direction relative to the longitudinal axis, wherein the inner portions and the outer portions overlap entirely circumferentially about the longitudinal axis, and wherein the inner portions are configured to slide tangentially relative to the outer portions during bending of the catheter.
18. The catheter of claim 17 wherein the strip of material has a first region and a second region, wherein adjacent ones of the of the inner portions and the outer portions overlap by a first distance in a direction parallel to the longitudinal axis in the first region, wherein adjacent ones of the inner portions and the outer portions overlap by a second distance in the direction parallel to the longitudinal axis in the second region, and wherein the first distance is different than the second distance.
19. The catheter of claim 17 wherein adjacent ones of the inner portions and the outer portions overlap by an overlap distance, and wherein the overlap distance varies along the longitudinal axis.
20. The catheter of claim 17 wherein the strip of material is wound about the longitudinal axis to have a pitch, and wherein the pitch varies along the longitudinal axis such that the strip of material defines a first region having a first stiffness and a second region having a second stiffness, wherein the first stiffness is different than the second stiffness.
Type: Application
Filed: Jul 28, 2022
Publication Date: Nov 17, 2022
Inventors: Richard Quick (Mission Viejo, CA), Brian J. Cox (Laguna Niguel, CA)
Application Number: 17/876,188