Catheter design for increased column strength

Abstract

To provide an improved catheter structure.SOLUTION: Objectives for designs presented herein can be for a variably flexible and kink-resistant catheter for vascular applications. The designs benefit from good compressive and tensile stiffness. A braided wire support structure can be disposed around an inner liner and an outer layer having a plurality of outer jackets of variable durometer. A metallic reinforcing layer can be cut from a hypotube and be used as a primary structure for catheter stiffness, reducing the reliance on and number of jackets to transition stiffness changes along a length of the catheter. The metallic reinforcing layer can have one or more ribbon cut segments and one or more axial hole patterns laser cut into the hypotube to progressively evolve the stiffness from proximally regions with more column stiffness and distal regions with greater lateral flexibility. The polymer jackets can be reflowed to bond the structure together.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates generally to devices and methods for accessing blood vessels during intravascular medical procedures, and more particularly, to catheters having improved flexibility while maintaining axial stiffness. [Background technology]

[0002] Catheters serve a wide variety of functions in intravascular medical procedures. Catheters are typically thin tubes made of medical-grade materials that can be inserted into the body and used to deliver drugs or other devices, perform surgical procedures, remove blockages from blood vessels, and for a variety of other purposes. By varying the materials or adjusting the method of manufacturing the catheter, different sections of the catheter can be tailored for specific uses.

[0003] For most intravascular catheters, it is preferable to have both a small outer diameter and a large inner diameter and lumen. A small outer diameter allows the catheter to be more easily manipulated when inserted into the body, allowing access to more distal sites such as neurovasculature. A large inner lumen allows larger medical instruments to be inserted and delivered through the catheter and / or allows larger fluid volumes or aspiration to be directed through the inner lumen. To minimize the outer diameter and simultaneously maximize the volume of the inner lumen, it is desirable to have a relatively thin catheter wall thickness that is still capable of having excellent flexibility and good resistance to stretching and compression.

[0004] Many access challenges exist that can make accessing a target site difficult. When access requires navigating the aortic arch (e.g., due to coronary or cerebral occlusion), the shape of the aortic arch makes it difficult to position a guide catheter in some patients. With conventional techniques, access to the neurovascular bed is particularly difficult because the target vessels are small in diameter, far from the insertion site, and highly tortuous. It is not uncommon for a catheter to have to navigate a tortuous path with multiple loops. In these locations, traveling just a few centimeters can result in a vessel segment with multiple extreme bends in succession, which can lead to kinking. In more confined areas of the arterial system, delicate vessels can be present that can be easily damaged by inflexible or high-profile devices.

[0005] Catheters for these procedures can be challenging to design in that they must be quite stiff at the proximal end to maintain pushability, responsiveness, and a comfortable operation for the user, while being flexible in the more distal portion to withstand high bending strains and pass through loops and progressively smaller vessel diameters without causing trauma. For these reasons, size, kink resistance, trackability, and flexibility are critical design parameters typically associated with catheters used in these procedures, and achieving the transition from softer to stiffer materials and regions is important for good patient outcomes.

[0006] Several designs and methods have been proposed for delivering catheters to target sites. In one method, the catheter is threaded over and slid along a guidewire used to access the target site. However, thin guidewires often have greater reach and distal flexibility than catheter tubing. New designs have been proposed that utilize various methods for varying the stiffness between the proximal and distal sections of the catheter, such as a set of polymer tubing, often with braids or windings incorporating wires or bands of other materials for reinforcement. Currently, most of these catheters control the transition from a harder material to a softer material by changing the configuration of the braided element (changing the braid P / C count or coil pitch) or by changing the durometer of the surrounding polymer material. However, too large a change in durometer between adjacent polymer segments can result in kink points at the transition. Therefore, current catheter designs are limited to similar polymer durometer transitions to mitigate the tendency for kink at such junctions, resulting in multiple polymer sections that add cost and manufacturing complexity.

[0007] The coils of braided wire or bands used to reinforce the polymer segments are often very finely sized continuous metallic superelastic or stainless steel. A sufficiently fine size or diameter of the coil or braid can make it prone to kinking, making it difficult to manufacture with the consistency required for a uniform product. Twisting the reinforcing layer can pose a risk of the metallic material cutting into the surrounding polymer at the twist. These materials also add cost and complexity.

[0008] Additionally, in thrombectomy procedures, aspiration catheters need to be very flexible to access remote occlusions, but also benefit from good compressive stiffness (for pushability and for stability and integrity when a clot retrieval device is retracted into them) and good tensile stiffness (to avoid stretching and deformation when tension is applied, such as when a large clot is retained and retrieved into an outer sheath). Traditional catheter designers have struggled to combine these properties without significant trade-offs. Thus, catheter designs often tend to sacrifice proximal column strength for flexibility and trackability. Summary of the Invention [Problem to be solved by the invention]

[0009] The present design aims to provide an improved catheter structure that addresses the above deficiencies. [Means for solving the problem]

[0010] The innovation of the present disclosure relates to a catheter having mechanisms for controlling axial and lateral stiffness and stiffness transition along the length of the catheter shaft. The catheter can be tubular with a proximal end, a distal end, and a longitudinal axis. The catheter can have a low-friction inner liner, a braided support structure disposed around the inner liner, a metallic stiffness transition reinforcement layer, and a series of outer polymer layers or jackets. The outer jacket can bond the reinforcement layer to the braided wire support structure. Near the distal end, a soft polymer tip can extend from the end of the braided wire support structure.

[0011] The design can have features that provide excellent column strength in the proximal portion of the catheter shaft and transition to a highly flexible distal section. The metallic reinforcing layer can be configured to balance the stiffness transition in the catheter. The design achieves the desired stiffness transition along the shaft by varying the configuration of these features across different axial segments of the shaft. This transition from a softer material to a harder material is important for the successful use of the catheter in vascular applications.

[0012] In some embodiments, the catheter can be a tube having a proximal end, a distal end, and a longitudinal axis. The catheter can be constructed of a series of layers. For example, the catheter can have an inner liner, a braided wire support structure disposed around the inner liner, and a metallic tubular reinforcing layer around the braided support structure configured to impart different stiffness characteristics to at least a portion of the catheter. Multiple outer polymer jackets can bind the aforementioned structures together. In one embodiment, the catheter can also have a soft polymer tip extending distally from the end of the braided wire support structure.

[0013] The braided wire support structure can be of a number of materials. In one embodiment, the wire is stainless steel. In another embodiment, the wire is nitinol or some other superelastic alloy. The wire diameter can be approximately 0.0015 inches or some other dimension. Other factors, such as the PIC count of the braid, can be varied to adjust the flexibility of the catheter. A first PIC count in a proximal portion of the braided wire support structure can be different from a second PIC count in a more distal portion of the braided wire support structure. In one embodiment, the first PIC count can be in the range of 20 to 70. In another embodiment, the second PIC count can be in the range of 120 to 200.

[0014] The metallic tubular reinforcing layer can be cut from a single continuous hypotube. In one embodiment, the tubular reinforcing layer can extend the entire distance between the proximal and distal ends of the catheter. In another embodiment, the reinforcing layer can extend from the proximal end and terminate midway along the braided support structure proximal to the distal end. The tubular reinforcing layer can be divided into a series of axial segments with the same or different cut patterns of removed material configured to impart different stiffness characteristics to at least a portion of the catheter. The cut patterns can be, for example, holes, slots, ribbons, and / or other features cut into the layer. The pattern and pattern density can vary along the axial segment of the catheter.

[0015] In some embodiments, at least one or more axial segments of the catheter can have one or more ribbon-shaped cut segments cut into a spiral extending longitudinally around the longitudinal axis. The dimensions and layout of the ribbon-shaped cut segments can be tailored to better transition between stiffness variations in various axial segments of the catheter. For example, one or more of the ribbon-shaped cut segments can have an axial portion having a first ribbon width that is different from a second ribbon width of another axial portion of the same ribbon-shaped cut segment. In another embodiment, a ribbon-shaped cut segment can have an axial portion having a first helical pitch that is different from a second helical pitch of another axial portion of the same ribbon-shaped cut segment.

[0016] In other embodiments, one or more of the axial segments can have an axial hole pattern cut from the tubular reinforcing layer. In some embodiments, the hole pattern can have a gradient that varies hole density, with greater distance between holes resulting in more residual material in the tubular reinforcing layer providing greater column strength to the catheter at those locations. Also, the holes in a hole pattern can be of different diameters and / or shapes, both within a given hole pattern or between two different hole patterns.

[0017] The hole pattern may also be arranged in a helical spiral pattern about the longitudinal axis. The helical pattern may have a variable pitch so that more or less raw metal may be present in a particular axial portion of the reinforcing layer. In one embodiment, the helical spiral pattern of holes may have an axial portion having a first helical pitch that is different from a second helical pitch in another axial portion of the helical spiral pattern. In another embodiment, the helical spiral pattern may have an axial portion having a first helical angle that is different from a second helical angle in another axial portion of the helical spiral pattern.

[0018] By varying the pitch and helix angle, the metallic reinforcement layer remains strong throughout, so column strength is not sacrificed axially. These changes to the hole pattern also mean that a gradient of material is removed. In some embodiments, multiple tiers of hole pattern types with increasing and decreasing sizes can be utilized to create an even smoother transition in stiffness within the catheter.

[0019] In one embodiment, a vascular access catheter can have a proximal end, a distal end, and a longitudinal axis extending therebetween. The catheter can have a braided wire support structure disposed about an inner liner, a metallic tubular reinforcement layer, and one or more outer polymer jackets.

[0020] In some embodiments, the braided wire support structure can extend from the proximal end of the catheter to a point near the distal end. The braid itself can feature a single PIC count or can have variable PIC counts in different axial portions of the catheter. The braid can also have different braid angles to vary bending characteristics along the axis of the catheter shaft.

[0021] A metallic tubular reinforcing layer can be disposed around the braided wire support structure. The reinforcing layer can extend the entire length of the wire support structure or a segment thereof from the proximal end. In some embodiments, the metallic tubular reinforcing layer can be formed from a single hypotube of shape memory alloy, stainless steel alloy, or other suitable material.

[0022] At least a proximal portion of the reinforcing layer can have one or more axial hole patterns with a gradient of varying hole densities cut into the layer. In one embodiment, the hole patterns can be arranged in a helical spiral pattern about the longitudinal axis. In another embodiment, the gradient can be achieved by varying the diameter and / or spacing of the hole pattern, which can be a linear axial geometry or a helical spiral pattern.

[0023] In another example, the reinforcement layer can have a portion having one or more ribbon-like cut segments arranged in a longitudinally extending spiral around the longitudinal axis. As with other examples, the ribbon-like cut segments can have design variables, such as ribbon width and pitch, that can be varied along the axial length of the segment to adjust the stiffness contribution of the reinforcement layer. The helix angle of the ribbon coil relative to the axis can also be adjusted for this purpose.

[0024] For example, the transition from one axial hole pattern to another, or from a hole pattern to an adjacent ribbon-like cut segment, can introduce stress concentrations and potential twist points. To avoid twisting and blending of stiffness transitions between various hole patterns and ribbon-like cut segments, the metallic reinforcement layer can also include transition features at and around the interfaces of adjacent axial segments. In some examples, the transition features can be intermediate transition holes to blend the progression from the hole pattern to the ribbon-like cut segment. In other examples, slots can be cut into the ribbon to bridge the transition from one ribbon-like cut segment having certain dimensions to another ribbon-like cut segment having different dimensions.

[0025] In another embodiment, one or more outer polymer jackets can be disposed around the tubular reinforcement layer. At least one outer polymer jacket can have a different durometer than the adjacent polymer jackets to adjust and transition the axial stiffness and bending characteristics in different sections of the catheter. For example, the outer jackets can have varying durometers to create a proximal section with greater column stiffness and a distal section with greater lateral flexibility. The jacket can be reflowed onto the underlying structure to bond the reinforcement layer to the braided wire support structure. The jacket polymer can flow through the holes in one or more axial hole patterns and the gaps in the ribbon-like cut segments of the metallic reinforcement layer when heat is applied.

[0026] Other aspects and features of the present disclosure will become apparent to those skilled in the art from the following detailed description considered in conjunction with the accompanying figures. [Brief explanation of the drawings]

[0027] These and further aspects of the present invention will be further considered with reference to the following description taken in conjunction with the accompanying drawings, in which: The drawings are not necessarily to scale, but instead focus on illustrating the principles of the invention. The figures depict one or more implementations of devices of the present invention, by way of example only, and not by way of limitation. [Figure 1] FIG. 1 is a diagram of a catheter having a metallic tubular reinforcing layer for increased column strength, in accordance with an embodiment of the present invention. [Figure 2] 2 is an enlarged view of the proximal end of the catheter of FIG. 1 in accordance with an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram of an example of an axial hole pattern in a metallic reinforcing layer, according to an aspect of the present invention. [Figure 4] 10A-10C are diagrams of alternative axial hole patterns having a helical configuration, according to aspects of the present invention. [Figure 5]10A-10C are diagrams of another example of a metallic reinforcing layer, according to an aspect of the present invention. [Figure 6] 1 is a diagram of a ribbon-like cut segment of a reinforcement layer according to an embodiment of the present invention. [Figure 7A] 10A-10C are diagrams of possible examples of transition mechanisms for the reinforcement layer, according to aspects of the present invention. [Figure 7B] 10A-10C are diagrams of possible examples of transition mechanisms for the reinforcement layer, according to aspects of the present invention. [Figure 8] 2 is an enlarged view of one of the outer polymer jacket transitions of FIG. 1 in accordance with an embodiment of the present invention. [Figure 9] 2 is an enlarged view of the distal end of the catheter of FIG. 1 in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The goal of the design presented herein may be for a variable flexibility, kink-resistant, elongated catheter shaft for vascular applications. The design is flexible enough to access remote vascular occlusions, but also benefits from good compressive and tensile stiffness. The catheter may have a braided wire support structure that serves as a framework with a low-friction inner liner disposed on the interior surface. An outer polymer layer or laminate jacket may cover this assembly.

[0029] This concept involves replacing the catheter's most proximal plastic segment with a metal-reinforced shaft incorporating a tapered, cut ribbon-like segment. To create this component, a gradual hole and / or slot pattern can be placed in the proximal portion of the metal shaft (proximal to the ribbon-like segment) to seamlessly integrate with the other plastic and braided components of the overall catheter design. This allows for a plastic jacket or jacket to be placed over the metal-reinforced shaft and braided structure. A seamless transition can be achieved by tapering the hole, ribbon, and / or slot pattern in the metal reinforcement layer without sacrificing axial column strength by maintaining a sturdy hypotube throughout.

[0030] Although this description is often in the context of mechanical thrombectomy or other treatments in the neurovascular bed, the described devices and methods may be readily adapted to other procedures and to other body passageways where catheters with highly adaptable stiffness requirements are needed. For example, microcatheters, which typically have much smaller diameters than other catheters, can also be made using these concepts.

[0031] Accessing the various vessels within the vascular system, whether coronary, pulmonary, or cerebral, involves well-known procedural steps and the use of many conventional, commercially available accessory products. These products include angiographic materials, rotating hemostatic valves, and guidewires that are widely used in laboratories and medical procedures. While they may not be specifically mentioned by name, these and similar products, when used with the systems and methods of the present invention in the following description, will not necessarily be described in detail as to their function and exact configuration.

[0032] Specific embodiments of the present invention will now be described in detail with reference to the figures, where like reference numbers indicate functionally similar or identical elements.

[0033] Referring to the figures, Figure 1 shows a catheter 100 for use in an endovascular procedure within a patient's blood vessels. The support tube 100 may generally be a tubular framework of layered construction between a proximal end 112 and a distal end 114, with a longitudinal axis 111 extending through the support tube 100. The innermost layer may be an inner liner 115 of PTFE or other low-friction material to facilitate passage of auxiliary devices through the catheter lumen. A braided wire support structure 120 may be disposed around the inner liner 115, having a braid or winding with wires or bands of other materials.

[0034] The coils of the braid can be very finely sized continuous metallic superelastic wire or stainless steel wire. The stiffness transition can be partially managed by modifying the configuration of the support structure 120 (e.g., by changing the braid's PIC count, wire diameter, or coil pitch). For example, the PIC count in the proximal portion of the braided wire support structure 120 can be less than a second PIC count in a more distal region. In one example, a PIC count of 120-170 can be used in the proximal region of the support structure 120 for good pushability characteristics. In another example, a first PIC count in one region can be in the range of 20-70, while a second PIC count in a more distal region can be in the range of 120-200.

[0035] Extending at least a portion of the length of the braided wire support structure 120 from the proximal end 112 of the catheter 100 can be a metallic tubular reinforcement layer 210. The layer 210 can be cut from a single continuous hypotube, for example, of NiTi or another suitable alloy. The transition in stiffness along the axial length of the catheter 100 can be managed by cutting a gradual axial hole pattern 220 and / or ribbon-like spiral segments 240 along various lengths of the hypotube to tailor flexibility. The metallic tubular reinforcement layer 210 can be a replacement for the proximal portion of many current catheter shaft designs, which is plastic. The metallic tubular reinforcement layer 210 can extend from the proximal end 212 to the distal end 214 and can terminate at a point proximal to the distal end 114 of the catheter 100. Beyond this termination, the inner liner 115 and braided wire support structure 120 may extend distally before the catheter shaft terminates in a soft polymer tip 10 at the distal end 114. A radiopaque marker or band 12 (such as platinum) may be used adjacent the tip 10 to mark the end of the catheter 100 during the procedure.

[0036] Like many current designs, the catheter may retain a braided wire support structure as a skeleton and add an overlying metallic reinforcing layer 210. The use of the metallic reinforcing layer 210 allows for the use of finer gauge wire in the braid. In some embodiments, the diameter of the braided wire may be approximately 0.0030 inches. In other embodiments, finer wires such as 0.0015 inches may be used. The skeleton of the braided support 120 may also be covered by a series of axial plastic tubular jackets 180, 182. The jackets may be made from various medical-grade polymers, such as PTFE, polyether block amide (Pebax®), or nylon. For example, materials may be selected (by durometer, flexural modulus, etc.) such that the more proximal segments are generally more progressively stiffer and less flexible as one approaches the proximal end 112 of the catheter 100.

[0037] An enlarged view of the proximal portion of the catheter 100 of Figure 1 is shown in Figure 2. The inner liner 115 can have an outer diameter 117 that defines the inner lumen of the catheter, which is centered about the longitudinal axis 111. The outer diameter 117 of the liner 115 can be bonded to the inner surface of the braided wire support structure 120, which in this case is visible through the axial hole pattern 220 of the overlapping metallic tubular reinforcing layer 210. The inner liner 115 can have a very limited thickness 116 to provide a maximum lumen size for device passage and efficient aspiration.

[0038] As shown, the axial hole pattern 220 in the more proximal portion of the reinforcement layer 210 can feature large holes that are geometrically spaced apart, leaving significant stiff material remaining between the holes in the reinforcement layer. This configuration can maintain good axial stiffness near the proximal end 212, while the hole pattern 220 or patterns can have features that allow for a transition to less material and more lateral flexibility in the more distal portion of the metallic reinforcement layer 210.

[0039] The reinforcement layer 210 can be placed over the braided wire support structure 120 similar to a polymer segment from another catheter design and reflowed or laminated in place to continue distally as a transition from the metal layer to plastic. To best blend the reinforcement layer with the braided support structure 120 and portions of the inner liner 115, a first polymer jacket 180 can cover the proximal zone as shown in FIGS. 1-2. The first polymer jacket 180 can be a range of materials and hardnesses depending on the properties of the underlying structure. For example, the first polymer jacket 180 can have a hardness of 55-70 Shore D (55D-70D), allowing the jacket and metallic reinforcement layer 210 in this region to be replaced with a 72D-80D polymer segment of a different stiffness in an existing catheter design.

[0040] The characteristics of the individual gradual axial hole patterns or patterns 220 of the metallic reinforcing layer 210 can be varied in various ways to achieve a desired flexibility and stiffness transition function. Figure 3 shows an example of a metallic reinforcing layer 210 having a first hole pattern 222 near the proximal end 212 of the layer, a second hole pattern 226 in the middle portion of the layer, and a third hole pattern 230 near the distal end 214.

[0041] Desired local stiffness characteristics of the metallic reinforcement layer hypotube 210 can be achieved by varying the hole size, the number of holes cut in the radial plane, and / or the spacing between holes in the hole patterns 222, 226, 230. The hypotube shown in Figure 3, for example and without limitation, has five different hole sizes, six transition zones, six different numbers of holes in the radial plane, and eight different hole spacings. Each of the hole patterns 222, 226, 230 can have multiple hole sizes and spacings to tailor the stiffness and transition between patterns along the axial length of the catheter and prevent the formation of kink points.

[0042] In one example, the first hole pattern 222 can have holes with a first hole diameter 224. The holes can be 1.00 mm diameter 224 and can have three holes (spaced 120 degrees apart) and / or four holes (spaced 90 degrees apart) in the radial plane. The second hole pattern 226 can have a second hole diameter 228 of 1.00 mm diameter with six holes (spaced 60 degrees apart) in the radial plane. In another case, the second hole pattern 228 can have a second hole diameter of 0.75 mm diameter with eight holes (spaced 45 degrees apart) in the radial plane, or a combination of these two examples. The third hole pattern 230 near the distal end 214 may have a third hole diameter 232 of 0.50 mm diameter with 12 holes (spaced 30 degrees apart) in the radial plane holes, a fourth hole diameter 234 of 0.25 mm diameter with 24 holes (spaced 15 degrees apart) in the radial plane holes, or a combination pattern of these examples.

[0043] The design can have a transition pattern or feature to bridge the transition in stiffness between, for example, the first hole pattern 222 and the second hole pattern 226. Thus, one example transition zone can have a pattern of four 1.25 mm holes per radial plane between the first pattern 222 (four 1.00 mm holes) and the second pattern 226 (six 1.00 mm holes). Such a transition pattern, while very short in axial length, can remove an amount of material from the hypotube to ensure that the hypotube has sufficient lateral flexibility in the boundary zone between the patterns.

[0044] In another example, a seamless stiffness transition can be achieved by cutting one or more tapered ribbon or spiral hole patterns into the hypotube of the metallic tubular reinforcement layer 210, as seen in Figure 4. As with other designs, the gradual tapered pattern removes varying amounts of material from the metallic tubular reinforcement layer 210, allowing for a gradual transition from hard metal to soft plastic in a portion of the catheter shaft. After the hypotube is cut, it remains rigid throughout its structure, allowing for radial flexibility through a series of holes without sacrificing column strength.

[0045] The most flexible distal portion of the hypotube can be achieved by arranging the hole pattern 220 in a dense helical ribbon about the longitudinal axis 111. The hypotube can have a progressive helical pattern as shown in FIG. 4, for example, without limitation, the pattern can have a "large" first hole diameter 224 and a smaller second hole diameter 228, followed by a band of raw metal. In one example, the first hole diameter 224 can be approximately 0.25 mm ID and the second hole diameter 228 can be approximately 0.15 mm ID. The most flexible distal section can have a relatively short third helical pitch 233, with the hypotube of the reinforcement layer 210 having a minimal amount of remaining material. The pattern can follow a variable pitch helix proximally, with more raw metal remaining to add axial stiffness and strength. For example, the intermediate portion of the hypotube can have a second helical pitch 227 that is greater than a more distal third helical pitch 233. The proximal end 212 of the reinforcing layer can have a helical pattern with a maximum pitch 225 such that the tube is stiffest around this location.

[0046] In another embodiment, the metallic reinforcing layer 210 can have a helical pitch of the hole pattern that varies continuously along the length of the segmented hypotube. This configuration can create a constantly varying stiffness profile along the longitudinal length of the reinforcing layer 210.

[0047] Similarly, the helix angle of the hole pattern 220 can vary along the length of the metallic tubular reinforcing layer 210 to transition between different sections and pitches. For example, a first helix angle 235 near the proximal end 212 of the hypotube can be shallower, i.e., more acute, than a more distal portion of the helical hole pattern. As the tube transitions to more distal helical pitches 227, 233, the helix angles 236, 237 can form progressively more obtuse angles with the longitudinal axis 111.

[0048] Illustrated in Figure 4 is a two-tiered hole pattern design, however, it is envisioned that 3, 4, or even 10 different holes of increasing or decreasing size, or varying helical patterns, could be used to provide an even smoother packing transition along the catheter's axis.

[0049] The resulting structure behaves largely as a plastic body in bending, yet maintains the stiffness and strength of a metal in the axial direction. Additionally, by incorporating a metallic reinforcing layer 210 into the catheter structure, it can have significantly higher column strength than existing catheter designs that incorporate only a metal braid or coil at the proximal end. Furthermore, the disclosed design can have much greater resistance to kinking, making it less likely to fracture on the proximal shaft of the catheter.

[0050] Another embodiment of a metallic tubular reinforcing layer 210 incorporating both a variable hole pattern and progressive ribbon-like coil segments to transition shaft stiffness is shown in FIG. 5. A first axial hole pattern 222 near the proximal end 212 of the reinforcing layer hypotube can transition to a helical second hole pattern 226. The hole pattern can feature holes having the same diameter, different diameters, or a combination of the two. The hole pattern can lead to one or more ribbon-like cut segments 240 reaching mid- and more distally through the hypotube 210.

[0051] The hole patterns 222, 226 can be variably cut in a manner similar to that described above, but the ribbon-cut segments 240 can also be tailored for stiffness. The ribbon-cut segments 240 can have properties such as helix pitch and ribbon width that can vary continuously along the length of the segment, creating a segmented or constantly varying stiffness profile. In addition, various helix angles can be utilized along the length of the tube.

[0052] The bending stiffness of the reinforcement layer 210 can be further adjusted by varying the cut width and coil width of the ribbon-like cut segment 240, either alone or in combination. If the cut width is kept constant, then the bending stiffness can be adjusted by varying, for example, the laser beam width or coil width. If the cut width is varied, then the coil width may be kept constant or varied, and the laser can be used to remove material. It will be appreciated that by using a cut width equal to the cut width of the laser beam, no material is removed, significantly reducing manufacturing costs. In contrast, using a laser to remove material allows for greater variation in shaft design. It will also be appreciated that a combination of both approaches can be used, such that the shaft incorporates more cost-effective cutting / machining means at the proximal end, while more expensive approaches are maintained at a certain distance at the distal end, where more complex cutting may be required to achieve desired performance.

[0053] Additionally, different materials can be used. For example, a proximal section of the shaft can be cut from SS and joined with a distal section cut from NiTi to reduce overall cost while providing the benefits of NiTi at the distal end of devices requiring increased resilience to tight bends and additional expansion and recovery characteristics. In such devices, the SS and NiTi sections can be joined by direct welding or by welding to a more suitable intermediate metal, such as platinum. Alternatively, a laser-cut connecting mechanism can hold both cut tubes together longitudinally. Furthermore, a complete change from NiTi to a harder material, such as SS or cobalt chrome, can also supplement the metal hypotube and surpass the polymer as the primary source of catheter stiffness.

[0054] An outer jacket or jackets (not shown) can hold the layers together radially. When one or more polymer jackets are remelted onto the catheter subassembly, the polymer can melt into the holes and slots and interstices between the ribbon coils to physically connect the metal hypotube reinforcement layer 210 to the underlying metal braided component. The reinforcement layer then allows for the best transition to the more flexible distal section of the catheter with other polymer components.

[0055] FIG. 6 illustrates an example of a section of a ribbon-shaped cut segment 240 having a helical arrangement wound around the longitudinal axis 111 to provide the segment with particular flexibility advantages. The ribbon-shaped cut segment 240 can be cut so that the helical pitch and coil width vary along the axial length of the segment. For example, a first helical pitch 242 can be shortened or increased relative to a second helical pitch 246. Similarly, the ribbon-shaped segment 240 can have a second coil width 247 that is wider than a first coil width 243. As the pitch and width vary, the helical angle formed by the ribbon-shaped coil with the longitudinal axis 111 must also vary, so the more proximal first helical angle 244 is more obtuse than the second helical angle 248. It should also be appreciated that parameters such as pitch and coil width can be continuously tapered as cut between the proximal and distal ends 212 and 214 of the metallic reinforcement layer to avoid abrupt transitions in stiffness. As a result, a higher level of variability can be achieved by cutting the turns of a single ribbon-like cut segment than if the pitch, coil width, and helix angle were held constant throughout the length of the segment.

[0056] Therefore, the design of these features and dimensions can be tailored to provide better compliance, push force, and torque response closer to the proximal end 212 of the reinforcement layer 210. Similarly, near the distal end 214 of the assembly, where flexibility is more critical, the ribbon-like cut segments 240 can have spacing between transitions to a gradual helical pitch to better optimize their physical capabilities.

[0057] During prototype testing of several proposed designs, additional mechanisms for improving performance were discovered. Where the ribbon-cut segments 240 proximally join with the hole patterns 222, 226, kink points can potentially occur where the hypotube of the metallic reinforcement layer 210 contributes a significant portion of the catheter's stiffness. This is due to stress concentrations resulting from geometric differences between the laser cutting mechanisms. If the differences are sharp enough at these locations, the metal ribbon-cut segments 240 can cut into the outer polymer jacket and split and / or separate from the structure. Furthermore, even with corner radiuses, cracks can form at the proximal-most corners of the ribbon-cut segments 240 where the metal hypotube transitions to the solid metal with the corresponding hole pattern. While the ribbon-cut segments 240 can have a continuous taper (the metal ribbon width gradually increases proximally), the abrupt transition from ribbon to hole pattern may be too abrupt to avoid kink / fracture points.

[0058] 5 and 7A-7B show that a transition feature easily incorporated into the design can prevent the concentration of forces from the ribbon segment to the perforation configuration during compression and bending loads. If the amount of material cut away to create the ribbon segment 240 is constant (distal to proximal within the ribbon segment), the concentration may be more severe. Therefore, the purpose of the transition feature may be to provide a better and more flexible transition between the ribbon section and the perforated section of the hypotube by allowing additional degrees of freedom of movement.

[0059] In the illustrated embodiment, the proximal end of the ribbon-like cut segment 240 can be gradually transitioned to the more robust hypotube of the reinforcement layer 210 by including one or more transition holes 260. As shown in FIGS. 5 and 7A, the transition holes 260 can begin at the proximal end of the breaks between the ribbon-like coils so that material is removed to aid flexibility, but is not continuous around the circumference of the tube. This pattern allows for similar material removal as that used to form the ribbon-like cut segment 240, but some material is left behind (metal spaces between the cut holes). The transition holes 260 can also form part of the second hole pattern 226, as the more geometric first hole pattern 222 does not necessarily have to begin immediately after the ribbon-like segment 240 is completed.

[0060] Similarly, once the ribbon-like cut segment 240 reaches a more proximal second coil width 247 that is greater than the target width, a transition mechanism of spiral cut slots 262 can be created in the remaining proximal metal ribbon, as shown in Figures 5 and 7B. This allows some freedom of movement for the wider ribbon-like section, but not so much that it loses the greater bending stiffness profile within the ribbon-like segment 240 (this section may behave less like a ribbon, and as shown in Figure 5, this section will more resemble a rigid body).

[0061] As mentioned above, multiple outer polymer jackets can be combined to form the outer layer of the catheter 100. A close-up view of the transition from the more proximal first polymer jacket 180 to the second polymer jacket 182 in the example shown in FIG. 1 is shown in FIG. 8. The use of a laser-cut metallic reinforcement layer 210 to manage the stiffness transition within the catheter shaft can mean less reliance on the material properties of the various polymer jackets. Current catheter designs are often limited to similar polymer durometer transitions to mitigate the tendency for kinking at such junctions. Thus, the metallic reinforcement layer 210 can simplify catheter construction and assembly by reducing the number of components and allowing for a greater difference between the hardness of the first jacket 180 and the second jacket 182. While designs incorporating the reinforcement layer 210 can also utilize one or two polymer segments, other current designs may involve the use of up to twelve polymer segments to provide an appropriate transition along the longitudinal length and prevent kinking between segments. The disclosed design therefore allows for the use of fewer jackets along the length of the catheter shaft, thereby eliminating some of the butt joints between jackets of different durometers.

[0062] The outer polymer jackets 180, 182 can be made from a variety of medical grade polymers, such as PTFE, polyether block amide (Pebax®), or nylon. For example, to add column strength and pushability to the catheter, materials can be selected such that the more proximal segments are generally stiffer and less flexible (by durometer, flexural modulus, etc.) as they approach the proximal end 112. Similarly, more flexible segments can be used distally.

[0063] As with other embodiments, the second polymer jacket 182 can be reflowed onto the underlying structure. Because the second polymer jacket 182 encompasses the desirably more flexible distal portion of the catheter shaft, the second polymer jacket 182 can be a softer material than the material used for the first polymer jacket 180. In one embodiment, the second jacket 182 can be low durometer Pebax® (25D-40D). In another embodiment, the second jacket 182 can be low durometer urethane or NeuSoft™ (42-73 Shore A). The transition between the jackets can also be tapered or slotted to provide a more seamless transition between the flexibility profiles of abutting jackets positioned longitudinally in series.

[0064] The braided wire support structure 120 can continue distally to the ribbon-like cut segment 240 and terminate near the distal end 114 of the catheter 100, as shown in FIG. 9 . As a result, there can be a distal section of the catheter having only the inner liner 115, the braided structure 120, and the second polymer jacket 182. A radiopaque marker band, which can be platinum or another suitable material, can be crimped or otherwise connected to mark the distal end 114 of the catheter 100 during the procedure. The distal end can have a very soft polymer tip 10 around the inner liner 115 and the longitudinal axis 111. The tip 10 can be NeuSoft™ or other suitable engineered thermoplastic material, which has good elasticity and abrasion resistance while providing UV stability and barrier properties against moisture and oxygen. Such materials typically have a standard durometer of 42 to 73 Shore A, although this range can be extended to meet specific design specifications.

[0065] The present invention is not necessarily limited to the examples described, which may vary in configuration and details. The terms "distal" and "proximal" are used throughout the foregoing description and are meant to refer to a location and direction relative to the treating physician. Thus, "distal" or "distally" refers to a location away from or a direction away from the physician. Similarly, "proximal" or "proximally" refers to a location closer to or a direction toward the physician. Furthermore, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0066] As used herein, the term "about" or "approximately" with respect to any numerical value or range of values ​​indicates a suitable dimensional tolerance that enables a portion of a component or a collection of components to function in accordance with its intended purpose as described herein. More specifically, "about" or "approximately" may refer to a range of values ​​of ±20% of the recited value, for example, "about 90%" may refer to a range of values ​​of 71% to 99%.

[0067] In describing exemplary embodiments, technical terminology is employed for the sake of clarity. Each term is intended to have its broadest meaning as understood by one of ordinary skill in the art and is intended to include all technical equivalents that similarly operate to achieve similar purposes without departing from the scope and spirit of the present disclosure. It should also be understood that a reference to one or more steps of a method does not preclude the presence of additional or intervening method steps between those explicitly identified steps. Similarly, some steps of a method can be performed in a different order than set forth herein without departing from the scope of the disclosed technology. For the sake of clarity and conciseness, not all possible combinations have been listed; such variations will often be apparent to those skilled in the art and are intended to be within the scope of the following claims.

[0068] [Embodiment] (1) A catheter, a proximal end, a distal end, and a longitudinal axis; An inner liner and a braided wire support structure disposed about the inner liner; a metallic tubular reinforcing layer disposed about the braided wire support structure, the reinforcing layer including one or more axial segments configured to impart different stiffness characteristics to at least a portion of the catheter; a plurality of outer polymer jackets disposed about the tubular reinforcing layer, the plurality of outer polymer jackets bonding the reinforcing layer to the braided wire support structure; at least one of the one or more axial segments includes one or more ribbon-like cut segments arranged in a longitudinally extending spiral around the longitudinal axis; A catheter wherein at least one of the one or more axial segments further comprises one or more axial hole patterns cut from the tubular reinforcing layer. (2) A catheter as described in embodiment 1, wherein the catheter further comprises a soft polymer tip extending distally from the end of the braided wire support structure. (3) A catheter as described in embodiment 1, wherein the braided wire support structure comprises stainless steel wire having a diameter of approximately 0.0381 mm (0.0015 inches). (4) A catheter as described in embodiment 1, wherein the braided wire support structure includes a first PIC count at a proximal portion of the braided wire support structure that is less than a second PIC count at a more distal portion of the braided wire support structure. (5) The catheter according to embodiment 4, wherein the first PIC count is within the range of 20 to 70.

[0069] (6) The catheter according to embodiment 4, wherein the second PIC count is within the range of 120 to 200. (7) A catheter as described in embodiment 1, wherein the tubular reinforcing layer is cut from a single continuous hypotube. (8) A catheter according to claim 1, wherein the tubular reinforcing layer extends the entire distance between the proximal and distal ends of the catheter. (9) A catheter according to embodiment 1, wherein the tubular reinforcing layer extends an intermediate distance from the proximal end of the catheter. (10) A catheter as described in embodiment 1, wherein at least one of the one or more hole patterns includes a gradient of varying hole density.

[0070] (11) A catheter as described in embodiment 1, wherein at least one of the one or more hole patterns includes holes of different diameters. (12) A catheter as described in embodiment 1, wherein at least one of the one or more hole patterns comprises a helical spiral pattern around the longitudinal axis. (13) The helical spiral pattern includes an axial portion having a first helical pitch that is different from a second helical pitch of another axial portion of the helical spiral pattern; A catheter as described in embodiment 12, wherein the helical spiral pattern includes an axial portion having a first helical angle that is different from a second helical angle of another axial portion of the helical spiral pattern. (14) A catheter as described in embodiment 1, wherein at least one of the one or more ribbon-shaped cutting segments includes an axial portion having a first ribbon width that is different from a second ribbon width of another axial portion of the same ribbon-shaped cutting segment. (15) A catheter as described in embodiment 1, wherein at least one of the one or more ribbon-shaped cutting segments includes an axial portion having a first helical pitch that is different from a second helical pitch of another axial portion of the same ribbon-shaped cutting segment.

[0071] (16) A catheter as described in embodiment 1, wherein at least one of the one or more ribbon-shaped cutting segments includes an axial portion having a first helical angle that is different from a second helical angle of another axial portion of the same ribbon-shaped cutting segment. (17) A catheter as described in embodiment 1, wherein the transition mechanism includes one of a hole or a slot configured to blend a longitudinal stiffness transition between the one or more axial segments of the tubular reinforcing layer. (18) A catheter for vascular access, the catheter comprising: a proximal end, a distal end, and a longitudinal axis; a braided wire support structure disposed about an inner liner, the support structure extending from the proximal end of the catheter to a point near the distal end; a metallic tubular reinforcing layer disposed about the braided wire support structure, the reinforcing layer including portions having one or more axial hole patterns cut therefrom having various hole density gradients, and portions having one or more ribbon-like cut segments arranged in a longitudinally extending spiral about the longitudinal axis; one or more outer polymer jackets disposed about the tubular reinforcement layer, at least one of the one or more outer polymer jackets comprising a durometer hardness that is different from a durometer hardness of an adjacent polymer jacket. (19) A catheter as described in embodiment 18, wherein the transition mechanism is configured to reduce stress and blend longitudinal stiffness transitions between one or more axial segments of the tubular reinforcing layer. (20) The catheter of embodiment 19, wherein the transition mechanism includes one of a hole or a slot.

Claims

1. A catheter comprising: a proximal end, a distal end, and a longitudinal axis; An inner liner and a braided wire support structure disposed about the inner liner; a metallic tubular reinforcing layer disposed about the braided wire support structure, the reinforcing layer including one or more axial segments configured to impart different stiffness characteristics to at least a portion of the catheter; a plurality of outer polymer jackets disposed about the tubular reinforcing layer, the plurality of outer polymer jackets bonding the reinforcing layer to the braided wire support structure; at least one of the one or more axial segments includes one or more ribbon-like cut segments arranged in a longitudinally extending spiral around the longitudinal axis; at least one of the one or more axial segments further includes one or more axial hole patterns cut from the tubular reinforcing layer; A catheter wherein the tubular reinforcing layer extends an intermediate distance from the proximal end of the catheter and terminates proximally of the distal end of the braided wire support structure.

2. The catheter of claim 1 , further comprising a soft polymer tip extending distally from the terminus of the braided wire support structure.

3. 10. The catheter of claim 1, wherein the braided wire support structure comprises stainless steel wire having a diameter of approximately 0.0015 inches.

4. The catheter of claim 1 , wherein the braided wire support structure includes a first PIC count at a proximal portion of the braided wire support structure that is less than a second PIC count at a more distal portion of the braided wire support structure.

5. The catheter of claim 4, wherein the first PIC count is in the range of 20 to 70.

6. The catheter of claim 4, wherein the second PIC count is in the range of 120 to 200.

7. The catheter of claim 1 , wherein the tubular reinforcing layer is cut from a single continuous hypotube.

8. A catheter as described in claim 1, wherein the proximal end of the slit between the ribbon-shaped coils of the ribbon-shaped cutting segment is formed with a hole having a diameter larger than the width of the slit.

9. The catheter of claim 1 , wherein at least one of the one or more hole patterns comprises a gradient of varying hole density.

10. The catheter of claim 1 , wherein at least one of the one or more hole patterns includes holes of different diameters.

11. The catheter of claim 1 , wherein at least one of the one or more hole patterns comprises a helical spiral pattern about the longitudinal axis.

12. the helical spiral pattern includes an axial portion having a first helical pitch that is different from a second helical pitch of another axial portion of the helical spiral pattern; The catheter of claim 11 , wherein the helical spiral pattern includes an axial portion having a first helical angle that is different from a second helical angle of another axial portion of the helical spiral pattern.

13. 2. The catheter of claim 1, wherein at least one of the one or more ribbon-shaped cut segments includes an axial portion having a first ribbon width that is different from a second ribbon width of another axial portion of the same ribbon-shaped cut segment.

14. 2. The catheter of claim 1, wherein at least one of the one or more ribbon-shaped cutting segments includes an axial portion having a first helical pitch that is different from a second helical pitch of another axial portion of the same ribbon-shaped cutting segment.

15. 2. The catheter of claim 1, wherein at least one of the one or more ribbon-shaped cutting segments includes an axial portion having a first helical angle that is different from a second helical angle of another axial portion of the same ribbon-shaped cutting segment.

16. The catheter of claim 1 , wherein the transition feature comprises one of a hole or a slot configured to blend a longitudinal stiffness transition between the one or more axial segments of the tubular reinforcing layer.

17. A catheter for vascular access, the catheter comprising: a proximal end, a distal end, and a longitudinal axis; a braided wire support structure disposed about an inner liner, the support structure extending from the proximal end of the catheter to a point near the distal end; a metallic tubular reinforcing layer disposed about the braided wire support structure, the reinforcing layer including portions having one or more axial hole patterns cut therefrom with varying hole density gradients and portions having one or more ribbon-like cut segments arranged in a longitudinally extending spiral about the longitudinal axis, the metallic tubular reinforcing layer extending an intermediate distance from the proximal end of the catheter and terminating proximal to the distal end of the braided wire support structure; two or more outer polymer jackets disposed around the tubular reinforcing layer, at least one of the two or more outer polymer jackets comprising a durometer hardness that is different from a durometer hardness of an adjacent polymer jacket in the direction of the longitudinal axis.

18. 18. The catheter of claim 17, wherein the transition feature is configured to reduce stress and blend longitudinal stiffness transitions between one or more axial segments of the tubular reinforcing layer.

19. The catheter of claim 18 , wherein the transition feature comprises one of a hole or a slot.

20. A catheter as described in claim 17, wherein the proximal end of the slit between the ribbon-shaped coils of the ribbon-shaped cutting segment is formed with a hole having a diameter larger than the width of the slit.

Images