Patent Application
20110160680
The present invention generally relates to a medical surgical device and specifically a wire guide for percutaneous placement within a body lumen. The flexibility of the wire guide can be varied by a cannula coaxially displaced on the wire core.
Wire guides are commonly used in vascular procedures, such as angioplasty procedures, diagnostic and interventional procedures, percutaneous access procedures, or radiological and neuroradiological procedures in general, to introduce a wide variety of medical devices into the vascular system. For example, wire guides are used for advancing intraluminal devices such as stent delivery catheters, balloon dilation catheters, atherectomy catheters, and the like within body lumens. Typically, the wire guide is positioned inside the inner lumen of an introducer catheter. The wire guide is advanced out of the distal end of the introducer catheter into the patient until the distal end of the wire guide reaches the location where the interventional procedure is to be performed. After the wire guide is inserted, another device such as a stent and stent delivery catheter is advanced over the previously introduced wire guide into the patient until the stent delivery catheter is in the desired location. After the stent has been delivered, the stent delivery catheter can then be removed from a patient by retracting the stent delivery catheter back over the wire guide. The wire guide may be left in place after the procedure is completed to ensure easy access if an additional procedure is required.
Conventional wire guides include an elongated wire core with one or more tapered sections near the distal end to increase flexibility. Generally, a flexible body such as a helical coil or tubular body is disposed about the wire core. The wire core is secured to the flexible body at the distal end. Especially for small diameter wire guides (0.014-0.018 inches), the wire core is made of either stainless steel or Nitinol with each having their own desired properties of flexibility with sufficient kink resistance and stiffness. In addition, a torquing means can be provided on the proximal end of the core member to rotate, and thereby steer a wire guide having a curved tip, as it is being advanced through a patient's vascular system.
A major requirement for wire guides and other intraluminal guiding members is that they have sufficient stiffness to be pushed through the patient's vascular system or other body lumen without kinking. However, they must also be flexible enough to pass through the tortuous passageways without damaging the blood vessel or any other body lumen through which they are advanced. Efforts have been made to improve both the strength and the flexibility of wire guides to make them more suitable for their intended uses, but these two properties tend to be diametrically opposed to one another in that an increase in one usually involves a decrease in the other.
For certain procedures, such as when delivering stents around challenging take-off, tortuosities, or severe angulation, substantially more support and/or vessel straightening is frequently needed from the wire guide. Wire guides that provide improved support over conventional wire guides have been commercially available for such procedures. However, such wire guides are in some instances so stiff they can damage vessel linings when being advanced.
For example, some wire guides comprise an assembly of a shape memory alloy wire core and cladding covering of a different metal extending along the wire core entirely. The assembly is drawn down in multiple steps to form an intimate mechanical bond between the wire core and cladded covering, thereby forming a wire of the composite structure. Annealing and cold working is typically required between drawing passes in order to achieve the desired properties of the composite. A combination of drawing and heat-treating and/or pressure-treating a cladded assembly is difficult and expensive, especially the manufacturing intensive steps to draw down fully to a wire guide size of about 0.018 inches. There is also excessive wear on the drawing equipment due to the abrasiveness of the shape memory core. The drawn composite structure usually requires the cladding covering material and the core material to run the entire length of the composite. This is problematic when the core wire alone has the desired flexibility, and the cladding covering material increases undesirably the stiffness of the distal end of the wire core.
In view of the above, it is apparent that there exists a need for an improved design for a wire guide.
One aspect provides a wire guide having sufficient flexibility and kink resistance, as well as sufficient pushability. In one embodiment, the wire guide includes an elongated mandrel and a cannula having a stiffness greater than the mandrel stiffness. The mandrel can be made of a shape memory alloy such as Nitinol and the cannula can be made of a metal alloy such as stainless steel, platinum, palladium, a nickel-titanium, or combinations thereof. The cannula lumen is sized to receive the mandrel therein, and has a length relative to the length of the mandrel such that a portion of the mandrel extends distal to the cannula when received in the cannula lumen. The extended distal portion of the mandrel can permit the wire guide to have sufficient flexibility and kink resistance at its distal region, while the cannula can permit the wire guide to have sufficient pushability at its proximal region. The cannula can be attached, preferably by soldering or welding, along the length of the mandrel at least at one attachment joint. The extended distal portion of the mandrel can have a taper from a first diameter to a second diameter to form a distal tip of the wire guide. A proximal portion of the mandrel may also have a taper from a first diameter to a second diameter to improve the flexibility along the proximal region of the wire guide. The wire guide may also include a polymer coating surrounding the extended portion of the mandrel to further form the distal tip, a hydrophilic coating disposed on a portion of the polymer coating, a lubricious polymer coating disposed on at least one of a portion of the cannula or a portion of the extended portion of the wire guide, or any combination of coatings.
In yet another embodiment, the wire guide can further include a slotted cannula to improve the flexibility of the wire guide where the cannula is located. The slots are formed in the wall of the cannula and are circumferentially disposed along the cannula wall. The slots formed in the cannula wall can be transverse to the longitudinal axis of the wire guide. More than one slot can be formed along a single circumferential region such that a first slot is circumferentially spaced from a second slot. More than one series of slots can be formed in the wall of the cannula to vary the flexibility along the wire guide. The slot of a series can be spaced from an adjacent slot of the same series at a longitudinal distance. This longitudinal distance at a proximal portion of the cannula can be greater than the longitudinal distance at a distal portion of the cannula to increase the longitudinal flexibility along the wire guide. The slots of a series can be circumferentially positioned relative to one another at an angle to form a generally helical pattern along the cannula wall to vary the circumferential flexibility along the wire guide. Slots of a second series can be interposed between adjacent slots of a first series. The second series slots may be circumferentially positioned relative to each of the first series slots at an angle such that the second series slots are circumferentially offset from the first series.
Another aspect provides a method of making a wire guide having sufficient flexibility and kink resistance, as well as sufficient pushability for use within a body vessel. An elongated mandrel having a taper from a first diameter to a second diameter and a cannula having a lumen is provided. The cannula lumen is sized to receive the mandrel therein. The cannula has a stiffness greater than the mandrel stiffness. The elongated mandrel is inserted into the cannula lumen such that a portion of the mandrel extends distal to the cannula. The cannula is attached, preferably by soldering or welding, to the mandrel to form a wire guide. A plurality of slots can be formed in the wall of the cannula by laser cutting.
Other features of the present invention and the corresponding advantages of those features will become apparent from the following discussion of the preferred embodiments of the present invention, exemplifying the best mode of practicing the present invention, which is illustrated in the accompanying drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.
In accordance with an embodiment of the present invention, a wire guide system includes a wire guide having sufficient flexibility and kink resistance, as well as sufficient pushability for use in a body vessel of a human or animal patient (“patient”).
The terms proximal and distal are used herein to refer to portions of a wire guide. As used herein, the term “distal” is defined as that portion of the wire guide closest to the end of the wire guide inserted into the patient's body lumen. The term “proximal” is defined as that portion of the wire guide closest to the end of the wire guide that is not inserted into the patient's body lumen. The terms distally and proximally are used herein to refer to directions along an axis joining the proximal and distal portions of the wire guide (“axial direction”). For example, proximal movement is movement towards the proximal portion of the wire guide. Distal movement is movement towards the distal portion of the wire guide.
The wire guide of the preferred embodiments includes a mandrel or wire core of a material having a desirable flexibility and kink resistance, which can run the entire length of the wire guide. The wire guide further includes a cannula of a stiffer material than the mandrel material coaxially disposed around the proximal portion of the mandrel to improve the stiffness more effectively along the proximal region of the wire guide for better pushability. Accordingly, this wire guide has sufficient stiffness to be pushed through the patient's vascular system or other body lumen without severe kinking. Also, the wire guide has an increased flexibility and kink resistance at the distal end for initial insertion around a challenging take-off and for navigation through the vasculature with tortuosities and/or severe angulation without damaging the blood vessel or any other body lumen through which the wire guide is advanced through.
Wire guide 10 includes a body 15 having a mandrel or elongated central core 12 and a cannula 14. Mandrel 12 can be made from many materials having flexible, elastic or bendable properties in order to traverse the vessels or arteries with sufficient kink resistance. The mandrel material can include stainless steel, such as spring temper stainless steel, Nitinol, or other materials that have properties similar to stainless steel and Nitinol, e.g., properties of kink resistance, capability of withstanding sterilization (heat and moisture), and non-toxicity. Depending on the application, the mandrel can be made of stainless steel because of its preferred properties of pushability and stiffness, although stainless steel can be more likely to plastically deform or kink. Compared to stainless steel, the mandrel can be made of Nitinol because of its preferred properties of flexibility and kink resistance, although Nitinol is less desirable for stiffness and pushability. Preferably, the mandrel is made of Nitinol wire core of about 50/50 mix of Nickel and Titanium in a super-elastic condition at or below a room temperature of 0 degrees Celsius.
Cannula 14 is disposed coaxially around the mandrel 12, preferably defining a region from the proximal end 16 of wire guide 10 to an intermediate portion of the wire guide. The material of cannula 14 can be any material having a stiffness greater than the stiffness of the material of mandrel 12. For example, the cannula can be made of a metal alloy, such as stainless steel alloy, such as a hypotube catheter shaft, platinum alloy, palladium alloy, nickel-titanium alloy, or combinations thereof. Cannula 14 comprises a cylindrical tubular body having a lumen with an interior diameter that is sized to fit snugly over a substantial portion of mandrel 12. The interior diameter of the cannula lumen depends on the size of the mandrel and, e.g., can be in the range of about 0.008 inches to about 0.015 inches. The outer diameter of cannula 14 can be in the range of about 0.016 inches to about 0.02 inches. The longitudinal length of cannula 14 is shorter than the length of the mandrel, being any length to increase sufficiently the stiffness of the proximal portion of mandrel 12. Also, in alternative embodiments, a portion of cannula 14 may also have a rectangular shape or any other shape adapted to provide a good grip that helps the physician maneuver wire guide 10 through the vascular anatomy.
Cannula 14 can be attached to mandrel 12 at one or more joints by any numerous attachment methods, including adhesives, soldering, such as ultrasonic soldering, and welding, such as laser or fusion welding. For example, the embodiment shown in
As shown in
In one embodiment, mandrel 12 has a substantial proximal portion 33 with a uniform outer diameter, typically associated with cannula 14. Proximal portion 33 of mandrel 12 has a longitudinal length that can range from about 20 cm to about 300 cm. To that end, the length of the cannula can be identical to the length of the proximal portion of the mandrel or much less, e.g., the length can be in the range of about 25% to about 100% the length of the mandrel, or about 100 cm to about 180 cm for a 300 cm mandrel. Extended portion 34 can be about 10 cm to about 30 cm.
Extended portion 34 of mandrel 14 can also include a portion 36 with the uniform outer diameter, as well as a distal tapering portion 38 which tapers from the uniform outer diameter to a smaller outer diameter, as shown in
The entire length of the wire guide or discrete lengths of the wire guide can be coated with a coating. For example, wire guide 10, preferably distal tip 32, can be covered by a first coating 42 that sufficiently bonds to mandrel 14. First coating 42 can be a polymeric material, such as nylon, polyethylene, polyurethane, fluoropolymer or the like. The thickness of coating 42 will vary in order to give a substantially uniform diameter, removing the discontinuities along its length that might otherwise exist. The thickness of coating 42 can vary proportionally to the tapering rate to the mandrel, and can range from about 0.001 inches to about 0.01 inches. The distal portion of distal tip 32 may be shaped and configured to be atraumatic.
A substantial length of wire guide body 15, including cannula 14, may be covered by a second coating 44 that is in addition to or instead of first coating 42. Second coating 44 can be any polymeric material having a surface exhibiting a low coefficient of friction, preferably lower than the bare metal cannula. In preferred embodiments, coating 44 is polytetrafluoroethylene (Teflon), but can also be nylon, polyethylene, polyurethane, fluoropolymer or the like. The thickness of second coating 44 can range from about 0.00002 inches to about 0.08 inches, and preferably ranges from about 0.0002 inches to about 0.02 inches. When the cannula has slots as described later, the slots may also have a coating of material within to protect the body vessel from possible sharp edges of the slots and/or make the slotted cannula smoother along the entire length.
A third coating 45 may also be applied to the outside of first coating 42 and/or the outside of second coating 44. In some instances, first coating 42 acts as primer or adhesion promoter between the mandrel material and the hydrophilic coating. Third coating 45 preferably is a hydrophillic coating comprising polyvinylpryrrolidones, polyethylene oxides, polyacrylates or a mixture thereof. Preferably, third coating 45 forms an exterior surface of the distal portion of the wire guide, having a lubricity with a coefficient of friction at least as low as second coating 44, if not lower. Each of the coatings described herein can be applied by any method known to a skilled artisan, e.g., spray, extrusion, brush, dip, or any combination thereof. It is to be understood by one of ordinary skill in the art that the wire guide can be bare metal without any coating or can include various combinations of coatings as described herein.
In alternative embodiments, distal tip 32 may include a coil (not shown) disposed circumferentially around extended portion 34 of the mandrel 14. An example of a coil construction distal tip is found in U.S. Pat. No. 7,001,345 to Connors, III et al., which is incorporated herein by reference in its entirety.
In some applications, it is desirable to have more flexibility toward the proximal end of the wire guide in order to distribute stress caused by flexing or bending the wire guide more evenly along the cannula, without sacrificing pushability performance. According to
The slots can have a variety of shapes and orientations. Preferably, slots 150 are formed to be transverse to the longitudinal axis into the wall of cannula 114.
One slot may be formed along a portion of any circumferential region of the cannula, or optionally, two or more slots can be formed at a particular circumferential region of the cannula. For example, in
Cannula 114 can have one or more series of slots. According to
One factor for the arrangement of the slots is the longitudinal spacing between slots located at adjacent circumferential regions of the cannula. The longitudinal spacing between adjacent slots of the same series can be any distance depending on the application. For example, in
With reference to
The number of longitudinal segments alone, or combined with the different arrangements of slots described herein, can vary the flexibility of the proximal portion of the wire guide at different rates. For example, the longitudinal spacing between adjacent slots of a series can be fixed within each of the longitudinal segments, but can also decrease (or increase) for each longitudinal segment in the distal direction along the cannula. According to
Another factor for the arrangement of the slots is the relative angular placement between slots of a series located at adjacent circumferential regions of the cannula, which can be any angle depending on the application.
In
The slots as mentioned may include additional series of slots with the same arrangement as the first series or with different arrangements. The additional series can be associated with the entire cannula or only a longitudinal segment of the cannula. The additional series may be associated with the same longitudinal segments as the first series, or each series may be associated with different longitudinal segments so as to take advantage of the features of each pattern along different segments of the cannula. According to
The longitudinal spacing between adjacent slots of different series can be any distance depending on the application. For example, the longitudinal spacing between slot 168 of the first series slots and slot 169 of the second series slots, adjacent to slot 168, can be in the range of about 0.008 inches or less to about 0.064 inches or more. Like the longitudinal spacing between adjacent slots in the same series, the longitudinal spacing between adjacent slots of different series can be fixed along the cannula, or can vary along the cannula. For example, the longitudinal spacing between adjacent slots of a different series can be fixed within each of the longitudinal segments, but can also decrease (or increase) for each longitudinal segment in the distal direction along the cannula. According to
The relative angular placement between adjacent slots of the first series 164 and the second series 166 can be any angle depending on the application. For example according to
In accordance with
A wire guide can be made having one or more features described herein, or any combinations thereof, with respect to the figures. Further detail, however, will be given to a method of manufacturing a wire guide with the slotted cannula of
A stainless steel cannula having an outer diameter of 0.018 inches and a wall thickness of 0.004 inches is cut to a specified length. The slots are laser cut to have the size, shape and/or pattern as described herein to form cannula 114. For example, each slot is laser cut to have a width of about 0.015 inches and to have a triangular shape with angle 155 of about 110 degrees between edges 152, 153 of the slot.
Each series of slots can be laser cut in consecutive order or concurrently. Cannula 114 includes a first series 164 of slots and a second series 166 of slots disposed along three discrete longitudinal segments 172A-C. A slot 168 of the first series 164 is disposed along a portion of a first circumferential region of cannula 114, and an adjacent slot 170 of the first series 164 is disposed along a portion of a second circumferential region of the cannula. Slot 168 of the first circumferential region and slot 170 of the second circumferential region are circumferentially disposed relative to one another at angle 174 of about 20 degrees. Slots of the second series 166 are shown interposed between adjacent slots of the first series 164. A second series slot 169 of a first circumferential region, interposed between slots 168, 170 of the first series 164, and the second series slot 171 of a second, adjacent circumferential region are circumferentially disposed relative to one another at an angle, identical to angle 174, of also about 20 degrees. The slot 168 of the first series 164 and the slot 169 of the second series 166 are shown circumferentially disposed relative to one another at an angle 183 of about 90 degrees.
The slots of each series within first longitudinal segment 172A are longitudinally spaced from one another at a distance of about 0.016 inches, while the distance between a first series slot and an adjacent second series slot is about 50% of the longitudinal distance between slots of the same series, or about 0.008 inches. The slots of each series within second longitudinal segment 172B have an increased longitudinally spacing from one another of a distance of about two times the distance, or 0.032 inches, of the slots in first longitudinal segment 172A, while the distance between a first series slot and a second series slot is about 0.016 inches. The slots of each series within third longitudinal segment 172C have an even larger spacing from one another of a distance of about four times the distance, or 0.064 inches, of the slots in first longitudinal segment 172A, while the distance between a first series slot and a second series slot is about 0.032 inches. The slots end at longitudinal segment 172C and a portion 172D of cannula 114 from the end of the last slot to the proximal end 124 of the cannula does not have any slots. The most distal slot of the first longitudinal segment 172A is spaced from the distal end 128 of cannula 114 by a distance of 1 inch, although it can be any distance. The longitudinal distance of the first longitudinal segment 172A is about 5 inches, of the second longitudinal segment is about 1 inch, and of the third longitudinal segment is about 1 inch.
With reference to
The tapered mandrel 12 is then inserted through the lumen of the slotted cannula 114, and axially positioned such that the proximal ends of the respective cannula and the mandrel are aligned and the tapered portion of the mandrel extends past the distal end of the cannula, as shown in
Although the invention has been described and illustrated with reference to specific illustrative embodiments thereof, it is not intended that the invention be limited to those illustrative embodiments. Those skilled in the art will recognize that variations and modifications can be made without departing from the true scope and spirit of the invention as defined by the claims that follow. It is therefore intended to include within the invention all such variations and modifications as fall within the scope of the appended claims and equivalents thereof.
