Dimpled joint for guidewires

Abstract

To provide a guidewire for advancing intraluminal devices within body lumens.SOLUTION: A guidewire for use in intravascular procedures has a solder or weld joint at a distal end thereof. Multiple dimples are formed on the solder / weld joint to increase the engagement with and penetration into fibrous material including chronic total occlusions (CTOs).SELECTED DRAWING: Figure 11B

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to the field of guidewires for advancing intraluminal devices, such as stent delivery catheters, balloon dilatation catheters and atherectomy catheters, through body lumens. [Background technology]

[0002] In a typical coronary procedure, a guiding catheter with a preformed distal tip is percutaneously introduced into a patient's peripheral artery, e.g., the femoral or brachial artery, using a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is located at the ostium of the desired coronary artery. There are two basic techniques for advancing a guidewire into a desired location within a patient's coronary anatomy, the first being the preload technique, which is primarily used for over-the-wire (OTW) devices, and the second being the bare wire technique, which is primarily used for rapid exchange type systems. With the preload technique, the guidewire is positioned within the lumen of an OTW device, such as a dilatation catheter or stent delivery catheter, with the distal tip of the guidewire just proximal to the distal tip of the catheter, and then both are advanced through the guiding catheter to its distal end. The guidewire is first advanced out of the distal end of the guiding catheter into the patient's coronary vasculature until the distal tip of the guidewire passes through the arterial location where the interventional procedure is to be performed, e.g., the lesion to be dilated or the dilated area where the stent is to be deployed. A catheter slidably mounted on the guidewire is advanced out of the guiding catheter and over the previously introduced guidewire into the patient's coronary anatomy until the operative portion of the intravascular device, e.g., a balloon of a dilatation catheter or a stent delivery catheter, is properly positioned across the arterial location. Once the catheter is in place with the operative means in the desired arterial location, the interventional procedure is performed. The catheter can then be removed from the patient over the guidewire. Typically, the guidewire is left in place for a period of time after the procedure is completed to ensure re-access to the arterial location. For example, if an arterial occlusion occurs due to collapse of a dissected endothelium, a rapid exchange perfusion balloon catheter can be advanced over the guidewire in place to inflate the balloon to open the arterial passageway and allow blood to perfuse through the distal portion of the catheter to the distal location until the dissection reattaches the arterial wall through natural healing.

[0003] When using the bare wire technique, initially only the guidewire is advanced through the guiding catheter until the distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. A rapid exchange (RX) catheter is then attached to the proximal portion of the guidewire that extends from the proximal end of the guiding catheter outside the patient's body. The catheter is advanced over the guidewire while the position of the guidewire is fixed until the surgical means on the RX catheter is positioned within the arterial location where the procedure is to be performed. After the procedure, the intravascular device may be removed from the patient over the guidewire, or the guidewire may be advanced further within the coronary anatomy for further procedures.

[0004] Conventional guidewires for angioplasty, stent delivery, atherectomy and other vascular procedures typically include an elongated core member having one or more tapers near its distal end, and a flexible body, such as a helical coil, or a tubular body made of polymeric material disposed about the distal portion of the core member. A moldable member, which may be a distal end of the core member or a separate molded ribbon secured to the distal end of the core member, extends through the flexible body and is secured by soldering, brazing or welding to the distal end of the flexible body forming a rounded distal tip. A torque application means is provided at the proximal end of the core member for rotating and thereby steering the guidewire during advancement through the patient's vasculature.

[0005] For certain procedures, such as when delivering a stent around a difficult take-off, e.g., a shepherd's crook, tortuous section, or highly angulated section, it is very often necessary to provide substantially more support from the guidewire and / or straightening of the vessel than a conventional guidewire can provide. Although guidewires that provide improved distal support over conventional guidewires have been commercially introduced for such procedures, such guidewires are not very maneuverable and in some cases are so stiff that they may damage the vascular endothelium when advanced therethrough. What has been needed, but heretofore unavailable, is a guidewire that provides a high level of distal support with acceptable maneuverability, but with a reduced risk of damage when advanced through the patient's vasculature.

[0006] Also, conventional guidewires that use tapered distal cores as discussed above can be difficult to use in many clinical situations because they have abrupt stiffness changes along the length of the guidewire, especially where the taper begins and ends. As a guidewire having a core with an abrupt stiffness change travels through a patient's tortuous vasculature, the physician moving the guidewire can feel abrupt resistance as the stiffness change is deflected by the curvature of the patient's vasculature. The abrupt change in resistance felt by the physician can impede the physician's ability to safely and controllably advance the guidewire through the vasculature. What is needed is a guidewire that does not have abrupt stiffness changes in its distal portion, especially in the portion that is bent within the vasculature and guiding catheter. The present invention meets these and other needs by providing distal tip integrity, kink resistance, improved torque response, improved distal tip radiopacity, and a smooth transition region. Summary of the Invention

[0007] In one embodiment of the present invention, the guidewire has a radiopaque inner coil and a substantially non-radiopaque outer coil. The inner coil and outer coil are attached to the distal end of the guidewire, and the outer coil covers the inner coil and extends proximally along the guidewire proximal to the proximal end of the inner coil. The inner coil is formed from a radiopaque material so that a physician can easily detect the location of the distal end of the guidewire by fluoroscopy during the procedure. Both the inner coil and the outer coil may be formed from a single wire or multiple wires.

[0008] In another embodiment, a mold is used to form a solder distal tip or solder joint at the distal end of the guidewire. The solder distal tip attaches the distal end of the guidewire and the distal end of the inner coil and the distal end of the outer coil (if present) together. It is important that the solder distal tip is uniform from one guidewire to the next and repeatable in structural formation. A mold including a split mold provides a bullet-shaped solder tip or a micro-J-shaped tip at the distal end of the guidewire to attach the inner and outer coils to the guidewire. Other shapes of solder tips are contemplated, such as cone-shaped, truncated cone-shaped, and solder joints with textured surfaces.

[0009] In another embodiment, a laser is used to form dimples on the surface of the solder joint connecting the distal end of the guidewire. A laser is used to form the dimples on the distal end of the solder joint such that the dimples resemble the dimples on the surface of a golf ball and can have a specific spacing and pattern. The laser can be programmed to provide dimples that are spaced apart from one another and have a specific diameter and depth according to the user's requirements.

[0010] In another embodiment, the guidewire of the present invention uses coils with different cross-sectional shapes to enhance the torqueability of the guidewire without adversely affecting the bending stiffness and functionality of the guidewire. For example, the different cross-sectional shapes of the coils can include I-beam, vertical rectangular, vertical elliptical, square, peanut, vertical hexagonal, horizontal hexagonal and horizontal elliptical cross-sections. Considering manufacturing, dimensional and tolerance constraints, I-beam, peanut, vertical rectangular and vertical elliptical cross-sections are preferred over conventional round cross-section coils to enhance the torqueability without adversely affecting the bending stiffness of the guidewire. Coils with different cross-sectional shapes can be used to form single-strand or multi-strand coils.

[0011] In another embodiment, a guidewire tip shaping tool forms a micro-J shape at the distal tip of the guidewire. The shaping tool is provided to the physician along with the guidewire so that the physician can use the shaping tool to select the amount of bend at the distal tip of the guidewire. Traditionally, physicians bend the distal tip of the guidewire by hand, which lacks control over the bend angle and bend shape. The shaping tool includes many cavities with different angular orientations and depths so that the physician can select the bend length and bend angle at the distal tip of the guidewire. The shaping tool is spring-biased toward an open position so that the distal end of the guidewire can be inserted into the cavities. Once the guidewire is inserted into the cavities, the physician gently presses the end of the shaping tool to overcome the spring force and move the inner tube with the cavities relative to the outer tube to form a bend at the distal tip of the guidewire. The cavities of a predetermined angle and length provide a consistent micro-J shape for the physician to use.

[0012] In another embodiment of the invention, the distal portion of the guidewire is reduced in cross section for greater flexibility when navigating tortuous vessels. In this embodiment, the parabolic distal portion of the guidewire includes a substantial portion of the distal portion that is ground to form a continuous taper. The continuous taper is formed by a parabolic grind along the distal portion of the guidewire. The parabolic grind provides a smooth curvilinear transition along the distal portion of the guidewire that is highly flexible yet maintains a linear change in stiffness, thereby providing superior torque and tactile feedback to the physician when advancing the guidewire through tortuous anatomy. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is an elevational view of a prior art guidewire showing a coil at the distal end of the guidewire. [Diagram 2] FIG. 2 is an elevational view of a guidewire of the present invention showing the inner coil and outer coil at the distal end of the guidewire. [Diagram 3] FIG. 1 is an elevational view of a multi-filar guidewire for use as an inner or outer coil on a guidewire. [Figure 4A] FIG. 1 is an elevational view of an octagonal coil for use as an inner or outer coil on the distal end of a guidewire. [Figure 4B] FIG. 4B is a longitudinal cross-sectional view of the eight-strand coil of FIG. 4A. [Diagram 5] 1 is a chart showing torque analysis of a guidewire of the present invention having different numbers of coils. [Figure 6] 6 shows the guidewire shown in FIG. 5 and is a graph showing the radiopacity of a distal portion of the guidewire with a coil. [Figure 7A] FIG. 13 is an elevational view of a mold for forming a solder bond on a distal end of a guidewire. [Figure 7B] FIG. 7B is a cross-sectional view of the mold of FIG. 7A taken along line 7B-7B. [Figure 8A] FIG. 13 is an elevational view of a mold for forming a solder bond on a distal end of a guidewire. [Figure 8B] FIG. 8B is an elevational view of the mold part of FIG. 8A. [Figure 9A] FIG. 13 is a cross-sectional view of a mold used to form a solder bond on the distal end of a guidewire, showing cavities for receiving molten metal. [Figure 9B] FIG. 9B is a top view of a solder joint formed by the mold of FIG. 9A. [Figure 9C] FIG. 9B is an elevational view of a solder joint formed by the mold of FIG. 9A. [Figure 10A] FIG. 1 is an elevational view of a mold for forming a solder joint having a micro-J shape. [Figure 10B] FIG. 1 is an elevational view of a mold for forming a solder joint having a micro-J shape. [Figure 11A] FIG. 13 is a top view of a bond showing a series of dimples formed by a laser. [Figure 11B] FIG. 11B is an elevational view of the joint of FIG. [Figure 12A] FIG. 13 is a top view of a bond showing a series of dimples formed by a laser. [Figure 12B] FIG. 12B is an elevational view of the joint of FIG. 12A. [Figure 12C] FIG. 12B is an enlarged top view of the joint of FIG. 12A. [Figure 12D] FIG. 12D is a side view showing one dimple formed in the joint shown in FIG. 12C. [Figure 12E] 1 is a chart showing test data comparing lesion crossing time of a laser dimpled guidewire compared to a commercially available guidewire. [Figure 13] FIG. 1 is an elevational view of a prior art coil having a circular or round cross-section wire. [Figure 14] 1 is a chart showing the elastic modulus, yield strength and ultimate strength of 304V stainless steel. [Figure 15] 15A and 15B are elevation and front views of a prior art coil having a circular or round cross section. [Figure 16]16A and 16B are elevation and front views, respectively, of a coil having an I-beam cross section. [Figure 17] 17A and 17B are elevation and front views, respectively, of a coil having a vertical rectangular cross section. [Figure 18] 18A and 18B are elevation and front views, respectively, of a coil having a vertical elliptical cross section. [Figure 19] 19A and 19B are elevation and front views, respectively, of a coil having a square cross section. [Figure 20] 20A and 20B are elevation and front views, respectively, of a coil having a vertical hexagonal configuration. [Figure 21] 21A and 21B are elevation and front views, respectively, of a coil having a horizontal hexagonal cross section. [Figure 22] 22A and 22B are elevation and front views, respectively, of a coil having a flattened cross section. [Figure 23] 23A and 23B are elevation and front views, respectively, of a coil having a horizontal elliptical cross section. [Figure 24] FIG. 23 shows the torque response of single-strand coils having different cross sections as shown in FIGS. 15A-23B. [Diagram 25] 2 is a chart showing the bending stiffness of coils having different cross sections shown in FIGS. 15A-23B. [Figure 26] FIG. 13 is an elevational view of the distal end of a guidewire inserted into a fixture showing the angle shape of the micro-J bend at the distal tip of the guidewire. [Figure 27A] FIG. 13 is an exploded perspective view of a forming tool for forming a micro-J shaped bend in the distal end of a guidewire. [Figure 27B] FIG. 13 is an elevated perspective view of a forming tool for forming a micro-J shaped bend in the distal end of a guidewire. [Figure 28A] FIG. 13 is an elevational view of a forming tool in an open position for forming a micro-J shaped bend in the distal end of a guidewire. [Figure 28B]FIG. 13 is an elevational view of a forming tool in a closed position forming a micro-J shaped bend in the distal end of a guidewire. [Figure 29] FIG. 29 is an enlarged circular view taken along line 29-29 showing the channels and cavities for receiving the distal end of the guidewire. [Diagram 30] FIG. 30 is an enlarged circular view of the cavity of FIG. 29 with a guidewire inserted through the channel into the cavity and bent into a micro-J shape. [Diagram 31] FIG. 1 is an elevational view of a prior art guidewire showing a distal section having multiple tapers. [Diagram 32] FIG. 13 is an elevational view of a guidewire showing a distal section having a parabolic ground profile. [Diagram 33] 33 is a graph showing bending stiffness along the distal portion of the guidewire shown in FIGS. 31 and 32. FIG. [Diagram 34] 1 is a schematic diagram showing a tapered distal portion of a prior art guidewire bending in a branch vessel. [Diagram 35] 1 is a graph of a 0.014 inch diameter guidewire showing a distal section having a parabolic grind profile. [Diagram 36] 1 is a graph of a 0.014 inch diameter guidewire showing a distal section having a parabolic grind profile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Prior Art Guidewires Prior art guidewires typically comprise an elongate core wire having a flexible, atraumatic distal end. A prior art guidewire is shown in FIG. 1 and comprises an elongate core member 11 having a proximal core section 12, a distal core section 13 and a flexible body member 14 secured to the distal core section. Distal core section 13 has a tapered segment 15, a flexible segment 16 distally adjacent tapered segment 15, a distal end 13a and a proximal end 13b. Distal section 13 also has two or more tapered segments 15 having a typical distally decreasing taper with a substantially rounded cross-section.

[0015] The core member 11 may be formed from stainless steel, NiTi alloy, or combinations thereof. The core member 11 is optionally coated with a lubricious coating, such as a fluoropolymer, e.g., Teflon available from DuPont, that extends the length of the proximal core. A hydrophilic coating may also be used. The length and diameter of the prior art guidewire 10 may vary to suit the particular procedure for which it is to be used and the materials from which it is constructed. The length of the guidewire 10 generally ranges from about 65 cm to about 320 cm, more typically from about 160 cm to about 200 cm, and preferably from about 175 cm to about 190 cm for coronary anatomy. The diameter of the guidewire generally ranges from about 0.008 inches to about 0.035 inches (0.203 to 0.889 mm) for coronary anatomy, more typically from about 0.012 inches to about 0.018 inches (0.305 to 0.547 mm), preferably about 0.014 inches (0.336 mm).

[0016] The flexible segment 16 terminates at a distal end 18. A flexible body member 14, preferably a coil, surrounds a portion of the distal section of the elongate core 13 with a distal end 19 of the flexible body member 14 secured to the distal end 18 of the flexible segment 16 by a solder body 20. A proximal end 22 of the flexible body member 14 is similarly joined or secured to the distal core 13 by a solder body 23. Materials and structures other than solder may be used to join the flexible body 14 to the distal core 13, and the term "solder body" includes other materials such as polymer adhesives including wax, epoxies, cyanoacrylates, and the like.

[0017] The wire from which the flexible member 14 is made typically has a transverse diameter of about 0.001 to about 0.004 inches, preferably about 0.002 to about 0.003 inches (0.05 mm). The distal portion of the coil may have multiple turns to provide additional flexibility. The coil may have about the same diameter or transverse dimension as the proximal core 12. The flexible member 14 may have a length of about 2 to about 40 cm or more, preferably about 2 to about 10 cm. The flexible member 14 in the form of a coil may be formed from a suitable radiopaque material, such as platinum or an alloy thereof, or may be formed from other materials, such as stainless steel, and coated with a radiopaque material, such as gold.

[0018] Flexible segment 16 typically has a length ranging from about 1 to about 12 cm, preferably from about 2 to about 10 cm, although longer segments may be used. The tapered configuration of flexible segment 16 provides a controlled longitudinal deformation and transition in flexibility (i.e., degree of stiffness) of the core segment. The flexible segment is adjacent to core member 11 and is disposed distally on distal portion 13 to function as a moldable member.

[0019] Guidewire with radiopaque inner coil - Patent application In accordance with the present invention, in one embodiment shown in Figures 2-6, guidewire 30 has an elongate core member 32 having a proximal core portion 34 and a distal core portion 36. Distal core portion 36 is preferably tapered, having a tapered segment 38 that tapers to a smaller diameter from guidewire proximal end 40 toward guidewire distal end 42. Elongate core member 32 is preferably formed from stainless steel, although it may be formed from other metals or metal alloys known in the art.

[0020] To improve radiopacity, the guidewire 30 shown in Figures 2-6 includes a radiopaque inner coil 44 positioned over the elongated core member at its distal end 42. The inner coil 44 may be 3 cm long and may have a distal end 46 that abuts the distal end 42 of the elongated core member 32. While 3 cm is the preferred length for the radiopaque inner coil 44, the length of the inner coil 44 may range from 0.5 cm to 15 cm as needed to meet the needs of the physician. The radiopaque inner coil 44 has a proximal end 48 having a plurality of coils 50 of wire extending from the proximal end 48 to the distal end 46. The radiopaque inner coil 44 is made of a radiopaque material selected from the group of radiopaque metals including platinum (Pt), palladium (Pd), iridium (Ir), tungsten (W), tantalum (Ta), rhenium (Re) and gold (Au). In one embodiment shown in FIG. 2, the radiopaque inner coil 44 is formed from a monofilament coil 50, the diameter of which can be varied as needed to balance radiopacity, flexibility, torqueability and kink resistance (durability). In another embodiment shown in FIG. 3, the radiopaque inner coil 44 is formed from a tetrafilament coil 52. The tetrafilament coil 52 of wire can be made using Drawn Filled Tubing (DFT) known in the prior art (a tube filled with or sandwiched by radiopaque material). The inner coil 44 may be formed with any number of filaments, such as the 8 filament coil shown in FIG. 4A and FIG. 4B. In one embodiment, the 8 filament coil of FIG. 4A and FIG. 4B is 31 cm long, has an outer diameter of 0.0135±0.0005 inches, an inner diameter of 0.0095 inches, a pitch of 0.193 inches, a wire diameter of 0.002 inches, and a spacing between the 8 wire segments of 25% of the wire diameter. These dimensions are representative and can be varied according to different needs.Importantly, all of the various coil configurations may be formed from the radiopaque metals listed herein so that the radiopaque inner coil 44 is radiopaque and easily visible to the physician under fluoroscopy.

[0021] The embodiment in Figures 2-6 also includes a non-radiopaque outer coil 56 having an inner diameter 58 that is greater than the outer diameter 60 of the radiopaque inner coil 44 and greater than the outer diameter of the elongate core member 32. The non-radiopaque outer coil 56 is formed from non-radiopaque materials including stainless steel (SS), cobalt-chromium (CoCr) and nickel-titanium (NiTi) alloys. The non-radiopaque outer coil may range in length from distal end 62 to proximal end 64 from 10 cm to 60 cm. In one embodiment, the non-radiopaque outer coil 56 is 30 cm long.

[0022] As shown most clearly in FIG. 2, the distal end 46 of the radiopaque inner coil 44, the distal end 42 of the guidewire 30 and the distal end 62 of the non-radiopaque outer coil 56 are all connected together by solder, adhesive, welding or brazing. Preferably, a solder ball 66 is formed on the distal end 42 of the guidewire 30 in a known manner for connecting the radiopaque inner coil 44 to the non-radiopaque outer coil 56 and the distal end 42 of the guidewire. It is important to emphasize that the distal end 46 of the radiopaque inner coil 44 is preferably not in contact with the distal end 62 of the non-radiopaque outer coil 56, which are connected together by the solder ball 66, although they may be directly connected to each other after the solder ball 66 is formed. The distal end 46 of the radiopaque inner coil 44 is not in contact with the distal end 42 of the elongate core member 32. The proximal end 48 of the radiopaque inner coil 44 is connected to the elongate core member 32 by a first solder joint 70, welding, adhesive, or brazing in a known manner. The proximal end 48 of the radiopaque inner coil 44 is not attached to the non-radiopaque outer coil 56. The proximal end 64 of the non-radiopaque outer coil 56 is attached to the elongate core member 32 by a second solder joint 72, welding, adhesive, or brazing in a known manner. The first solder joint 70 is proximal to the solder ball 66 and distal to the second solder joint 72. The proximal end 64 of the non-radiopaque outer coil 56 is not connected to any portion of the radiopaque inner coil 44, thereby providing a seamless outer surface 68 along the non-radiopaque outer coil 56 without any solder joints with the radiopaque inner coil that would cause stiffness problems. 2, there are no gaps between the elongate core member 32 and the inner coil 44 and outer coil 56, and no gaps between the inner coil 44 and outer coil 56. Like the radiopaque inner coil 44, the non-radiopaque outer coil 56 may be formed from any number of coil strands, such as a single strand coil 50, a four strand coil 56 (FIG. 3) or an eight strand coil as shown in FIGs. 4A and 4B.

[0023] Experiments were performed to determine the effect of multi-filar coils on torque, as shown in the graph of Figure 5, where straight torque was measured for guidewires having inner and outer coils with only 1 filament, guidewires having inner and outer coils with 4, 6, and 8 filaments, and inner and outer coils that were laser cut in the form of a vertical rectangle. As seen in Figure 5, the single filament coils of the present invention and the multi-filar coils are preferably compared in torque performance.

[0024] Tests were also conducted to measure radiopacity on the guidewires of the present invention, as seen in Figure 6. Guidewires in groups 1-6 have a radiopaque inner coil and a non-radiopaque outer coil as disclosed in Figure 2. The radiopacity of the radiopaque inner coil is preferably comparable when compared under fluoroscopy to the commercially available WHISPER® guidewire sold by Abbott Cardiovascular Systems, Inc. (Santa Clara, Calif.).

[0025] 2, the proximal portion 74 of the guidewire 30 has a silicone-based hydrophobic coating and a polytetrafluoroethylene (PTFE) coating. The distal portion 76 has a polyvinylpyrrolidone (PVP) hydrocoat coating. Typically, the distal end 42 of the guidewire 30 is uncoated.

[0026] Mold for forming the solder distal tip Guidewires are available in many different configurations, including tip loading, support contours, and materials of construction, all selected by the physician for the specific clinical case requirements. It has been recognized that for certain situations, a guidewire distal tip with a specific geometry provides the physician with a mechanical advantage in navigating tortuous pathways or occluded segments. In this embodiment, the characteristics of molten solder flow are overcome to contain the molten solder flow within a predetermined shape. Currently, a solder joint is formed at the distal tip of the guidewire that attaches the elongated core to the outer coil. This solder joint is formed utilizing a conventional soldering iron to heat and flow the solder onto the core and secure the coil to the core when it solidifies. The present invention allows for the creation of a soldered tip by different means and achieving a specific shape by casting molten solder into a predetermined shape.

[0027] As shown in Figures 7A-10B, a mold 80 is used to cast a soldered tip that overcomes many obstacles in both cost and manufacturability. Using the mold 80 to form the predetermined soldered shape not only obtains the intended geometry of the solder joint, but also makes the necessary solder joint that attaches the elongated core of the guidewire to the outer coil (see, for example, Figures 2-6). The mold can be machined as simply as a bullet shaped tip 82, or can be machined to include small angular features in what is called a micro-J shaped tip 84. Utilizing the mold 80 to perform this solder tip operation gives the engineering team the ability to modify the configuration to fit the requirements of the product being made.

[0028] Mold 80 is made as a solid mold constructed of ceramic or other suitable material capable of withstanding the temperatures required to receive molten solder. Mold 80 has a cavity 86 that receives the molten solder and the distal tip of the elongate core of the guidewire and the distal end of the coil, if present. The shape of cavity 86 determines the shape of the solder joints, such as bullet shaped tip 82 and micro-J shaped tip 84.

[0029] More complex shapes can be achieved by utilizing a split mold 90 in which a first shell 92 and a second shell 94 are held together while the solder is molten and then separated to demold the solder tip 88. The split mold 90 has the solder tip 88 configuration machined on a first side 96 and a mirror image machined on a second side 98. The split mold 90 can be machined as a bullet shaped tip 82 or to include small angle features to form a micro-J shaped tip 84. A variety of other solder tip 88 shapes can be formed by the split mold 90, such as a cone shape, a truncated cone shape, and a textured surface.

[0030] The method for forming the solder tip 88 includes placing the mold in a heating apparatus and allowing the solder to become molten. Once melted, the distal tip of the elongated core of the guidewire is dipped into the mold cavity 86 to allow the solder to flow onto the distal tip and the first few turns of the outer coil (if present). A heat conductor can be placed around a segment of the outer coil just above the mold cavity 86 to prevent the solder from flowing to undesired locations and to control the precise placement of the solder tip 88. Once the solder has flowed into the designated area, the split mold 90 is rapidly cooled to solidify the solder and allow the solder to bond the distal tip and coil of the guidewire together. Once cooled, the part may be removed from the mold 80 or the first and second shells 92, 94 may be separated and the solder tip 88 removed.

[0031] Utilizing the mold 80 to form the solder tips 88 gives the engineering team the ability to quickly change configurations for the product being made.

[0032] Additionally, the first and second surfaces 96, 98 can be modified to provide several types of features or textures depending on the needs of a particular product as determined by the application. The mold 80 may have some form of texture or even grooves (raised or recessed) to allow for a particular exterior geometry as needed for a specified product requirement. For example, as shown in Figures 9A-9C, a split mold 90 has an angled groove 100 formed in the mold cavity 86 such that the solder tip 88 has a matching angled groove 102.

[0033] Most guidewires use solder to form a bond at the distal tip to connect the coil, although some guidewires may use epoxy or another similar material instead of solder. The above discussion of Figures 7A-10B regarding solder tip 88 also applies to other suitable metals and epoxies.

[0034] Laser for forming dimpled joints Generally, most commercially available guidewires have guidewire tips made from solder or welded materials and have a smooth dome-shaped surface. Such guidewires face challenges when used to pass through calcified and fibrous tissue to treat chronic total occlusions (CTOs). Certain commercially available guidewires are designed with higher tip loads to treat CTOs and penetrate complex and stenosed lesions. Optimal wire strength, tip load and tip shape aid in pushability and maneuvering the guidewire through the lesion, but a smooth tip surface would likely have challenges engaging calcified and fibrous tissue, causing the tip to deflect and fail to penetrate the lesion. In one embodiment shown in Figures 11A-12D, a laser (not shown) is used to create a roughened surface 154 at the solder / weld joint 156 at the distal tip of the guidewire 150. Commercially available lasers, such as fiber lasers, can provide a focused spot of approximately 0.0254 millimeters and can provide random or closely stitched patterns as shown in Figures 11A and 11B, or spaced dimples 158 as shown in Figures 12A-12C. The dimples 158 resemble the dimples on the surface of a golf ball and can have a particular spacing and pattern. In one embodiment, the laser forms a series of dimples 158 that have a diameter of 0.0254 millimeters and are spaced 0.0254 millimeters apart from one another. In another embodiment, the dimples 158 have a diameter in the range of 0.0127 millimeters to 0.127 millimeters and have a spacing between the dimples 158 in the range of 0.0127 millimeters to 0.127 millimeters. In another embodiment, the laser forms dimples 158 that have a diameter of 0.0254 millimeters and are spaced 0.0127 millimeters apart forming a roughened surface 154. It is also possible to provide a larger spacing between the dimples 158 to provide a mechanical advantage in certain clinical cases.The laser may be programmed to provide areas to be left untouched (i.e. smooth) on the solder / weld joint 156 depending on the application. The pattern (dimples 158) to be removed is easily modified by simply changing the laser frequency, lattice spacing (how spaced dimples 158 are from each other), or by programming each dimple to achieve the optimum configuration.

[0035] The dimples 158 also have a depth dimension 160 and a diameter 162, as shown in Figure 12D. Preferably, the dimples 158 have a depth dimension 160 in the range of 0.5μ to 1.5μ, more preferably 1.0μ.

[0036] Similarly, the radial dimension 162 of the dimple 158 may range from 0.3μ to 6.0μ, preferably 2.0μ to 4.0μ, and more preferably 3.0μ. In this process, a commercially available fiber laser is utilized to selectively soften and dimple the solder / weld surface of the guide wire tip, where the beam is directed, while the wire tip is placed at the end of a fixture. This process is accomplished without destroying the structural integrity of the solder / weld of the solder or weld material due to the extremely fast pulse speed of the laser, which provides focused heating only where the beam is targeted. In one embodiment, the cycle time for the laser process is 50 ms, which allows for modified tip texture in a time acceptable in a production environment. Higher or lower laser cycle times are acceptable depending on the composition of the solder / weld and the size and depth of the dimple.

[0037] In addition to using commercially available lasers, the dimples 158 can be formed by other processes such as bead blasting, chemical etching or mechanical impact, so long as the integrity of the solder / weld joint 156 is maintained.

[0038] The dimples 158 can be formed in the surface of the solder / weld joint 156 after the joint is formed in the distal tip 152 of the guidewire 150. Alternatively, the solder / weld joint 156 is manufactured at the component level and the dimples 158 are then formed in the surface of the joint. The solder / weld joint 156 with the pre-formed dimples 158 can then be attached to the distal tip 152 of the guidewire 150.

[0039] Experiments were conducted to compare the lesion crossing performance of the laser dimpled guidewire with a commercially available guidewire, as shown in FIG. 12E. Tests were conducted against a clinically relevant chronic total occlusion (CTO) model to determine the time it takes for the guidewire to cross the lesion. Round dots represent the time in seconds it takes for the guidewire to cross the lesion, and triangular dots represent guidewires that failed to cross the lesion. As can be seen from FIG. 12E, the laser dimpled guidewire performed substantially better than the commercially available guidewire and the wire without dimples, in terms of consistently better crossing times and no failed attempts to cross the lesion.

[0040] Coils with different cross-sectional shapes Generally, the distal end of the guidewire must have a small supportive shape to make it flexible enough for passing capability. Therefore, the distal end of the core is ground (tapered) and covered with a coil to make it flexible and atraumatic (see, e.g., Figures 2-3). The coil also helps to maintain a consistent outer diameter of the guidewire. Prior art coils are formed from wire with a circular cross section (Figure 13) and are cut with a laser.

[0041] For next generation guidewires, good torque response without adversely affecting the bending stiffness of the guidewire is an important functional attribute.

[0042] In the present invention, several wire cross sections were designed to improve the functionality of the guidewire, and finite element analysis (FEA using ABAQUS commercial software) was performed on these guidewire cross sections to determine the effect of different cross sections on the torque response and bending stiffness.

[0043] The present invention uses coils of different cross-sectional shapes to increase torqueability without adversely affecting the bending stiffness and functionality of the guidewire. As shown in Figures 15A-23B, different embodiments include circular 178 (prior art), I-beam 180, vertical rectangular 182, vertical elliptical 183, square 184, vertical hexagonal 186, horizontal hexagonal 188, flat 190 and horizontal elliptical 192 cross sections. FEA demonstrates that more material is removed from the neutral axis (NA) of the coil wire, thus increasing torqueability while decreasing bending stiffness. Coils with different cross sections were fabricated and torque was applied while keeping other parameters such as the coil wire material and volume constant. For this study, the coil material considered was 304V stainless steel. Figure 14 shows the material properties of 304V stainless steel. To keep the volume constant, the cross-sectional area, length, nominal diameter and pitch of the wire were kept constant.

[0044] Coils with different cross sections with the same length, pitch, average diameter and cross section (dimensions scaled up to 100) are shown in Figures 15A-23B. Figure 24 shows the torque response of single strand coils with different cross sections analyzed by ABAQUS with the material properties provided. The I-beam shape has the highest torsional stiffness, followed by rectangular and vertical elliptical cross sections. Peanut cross section wire also showed high torsional stiffness (Figure 24). Figure 25 shows the bending stiffness of coils with different cross sections. Thus, changing the wire cross section of the coil from circular to I-beam shape increased the torque response by 250% while decreasing the bending stiffness by 50%. Considering the constraints due to manufacturing, dimensions and tolerances, I-beam, peanut, vertical rectangular and vertical elliptical shapes depending on the application or other limitations are preferred over conventional round cross section coils.

[0045] In Figures 15A-23B, the shapes and sizes of coils 178, 180, 182, 183, 184, 186, 188, 190 and 192 are for illustrative purposes and to ensure that parameters such as coil wire length, pitch, average diameter and cross-sectional area are constant for testing purposes.

[0046] Coils 180, 182, 183, 184, 186, 188, 190 and 192 may be used with guidewire 30 shown in Figures 2-6 and may be used as either inner coils or outer coils.

[0047] Guidewire tip forming tool - Micro J Guidewires are sold in either straight or preformed "J" shaped configurations. Typically the distal tip of the guidewire is a micro "J" shape to aid in maneuverability. The wire can be shaped by the manufacturer or by the physician using a shaping tool provided with the guidewire. Shaping by the manufacturer is an automated process that is more repeatable and does not compromise the integrity of the wire. The majority of users prefer a straight wire and shape the tip themselves. Guidewire manufacturers provide mandrels and introducers to assist the physician in shaping the wire.

[0048] It has been found that users do not have good control in how they shape the wire and can easily damage the wire. Tests have shown that there is an optimal angle (i.e., about 20°-30°) and distance from the tip (2-3mm) that can significantly aid wire performance. Even though physicians know what their desired specifications are for the bend depending on the size, most physicians do not know where they are close to the intended optimal dimensions. Also, there is a higher risk that the wire will lose its integrity and functional performance when the physician performs the shaping.

[0049] In the embodiment shown in Figures 26-30, a micro "J" forming tool can be shipped with the guidewire or sold as a separate accessory. This forming tool has pre-defined pre-existing slots where the physician can determine the angle and distance from the tip to form the micro-J shaped bend. This tool also has a universal design and can fit all of the manufacturer's guidewires.

[0050] In the embodiment shown in Figures 27A-30, the forming tool 200 comprises a first member 202 and a second member 204 and a plurality of cavities 206 having different depths and shapes. A channel 208 extends through a wall 210 of the first member 202 to provide access for a distal end 212 of a guidewire 214. The second member 204 is slidably contained within the first member 202 and a third member 205 is inserted into a slot 207 of the first member 202 to hold the second member 204 within the first member 204. The third member 205 may be glued or laser welded within the slot 207 while allowing longitudinal movement or sliding between the first member 202 and the second member 204. A pair of springs 216 are spring biased to maintain the spacing tool 200 in an open position 218. In the open position 218, the distal end 212 of the guidewire 214 can be inserted through the channel 208 and advanced into one of the cavities 206 (see FIG. 27B). To form a micro-J tip, the user pushes the end of the second member 204 in the direction of the arrow in FIGS. 28A and 28B, thereby overcoming the spring force of the spring 216. As shown in FIGS. 28A-30, the second member 204 slides relative to the first member 202 to a closed position 220. In the closed position 220, the cavity 206 has moved relative to the channel 208 such that the distal end 212 of the guidewire is bent at a predetermined angle and the bend sets a predetermined length from the end 222 of the distal end 212. When the user releases pressure on the end of the forming tool 200, the spring 216 springs open, moving the first member 202 to an open position 218 so that the guidewire 214 can be removed from the cavity 206. The cavity 206 shows bends at angles of 25° and 30°, although bends at angles ranging from 5° to 40° are contemplated. Similarly, the bend length from the distal end 220 to the unbent portion of the guidewire 214 is preferably 1 mm or 2 mm, although the length may range from 0.5 mm to 5 mm.

[0051] Parabolic grinding profile In another embodiment of the invention, the distal portion of the guidewire is reduced in cross section to be more flexible when navigating tortuous vessels such as coronary arteries. The distal portion of the guidewire must be flexible and pushable, i.e., it must be able to bend and steer through tortuous arteries, and also have some stiffness so that it can be pushed or advanced through the arteries without bending or kinking. A prior art guidewire is shown in FIG. 31 and has a distal portion consisting of a tapered section and a non-tapered core. The resulting bending stiffness is shown in the graph of FIG. 33, where the bending stiffness decreases at each taper, and the bending stiffness remains constant along the non-tapered core. The tapered distal portion of the prior art guidewire of FIG. 31 provides an abrupt change in bending stiffness, which may reduce tactile sensation to the physician when advancing the guidewire through tortuous anatomy. Indeed, in some prior art guidewires, the sudden change in bending stiffness can cause the distal tip of the guidewire to kink or become dislodged into a branching vessel as shown diagrammatically in FIG. 34. Dislodgment can be dangerous to the patient in that the artery may be damaged or punctured. Importantly, it is preferable to maintain the outer diameter of the core as distally as possible to maintain torque. Each taper loses significant torque when advancing the guidewire through a tortuous vessel.

[0052] In keeping with the present invention, a parabolic distal section 232 of guidewire 230 is shown in FIG. 32 where a significant portion of the distal section has been ground to form a continuous taper. More specifically, the continuous taper is formed by a parabolic grind along parabolic distal section 232 of guidewire 230. The parabolic grind provides a smooth curvilinear transition along section 232 that is highly flexible yet maintains a linear change in stiffness, as shown in the graph of FIG. 33. Not only is parabolic distal section 232 flexible, it also has a linear change in stiffness, thereby providing the physician with superior torque and tactile feedback when advancing the guidewire through tortuous anatomy. A non-curved tapered section 234 (not the parabolic ground section) is located on guidewire 230 distal to parabolic distal section 232, which provides a reduced bending stiffness and linear change in bending stiffness, as shown in the graph of FIG. 33.

[0053] Bending stiffness can be measured in a variety of ways. A typical method of measuring bending stiffness involves extending a portion of the sample to be tested from a fixed block while the sample is immovably fixed to the fixed block, and measuring the amount of force required to deflect the end of the sample a predetermined distance away from the fixed block. A similar approach can be used by fixing two points along the length of the sample and measuring the force required to deflect the middle of the sample a fixed amount. Those skilled in the art will appreciate that there are numerous variations on these basic methods, including measuring the amount of deflection resulting from a fixed amount of force on the free end of the sample. Other methods of measuring bending stiffness may produce values ​​in different units of different overall magnitude, but the overall shape of the graph will remain the same regardless of the method used to measure bending stiffness.

[0054] Parabolic grind profiles for a 0.014 inch diameter guidewire are shown in Figures 35 and 36, respectively. The guidewire in Figure 35 has a tip load of 11 grams and the guidewire in Figure 36 has a tip load of 14 grams. The units of scale on the Y-axis are inches and the X-axis are centimeters. In both Figures 35 and 36, two parabolic grind profiles are separated by a uniform diameter core wire segment. More specifically, each graph shows a first parabolic grind profile beginning about 23.1 cm from the distal tip of the guidewire and ending about 17.9 cm from the distal tip. Additionally, each graph shows a second parabolic grind beginning about 4.8 cm from the distal tip. There is a uniform diameter core wire segment between the parabolic grind segments and a uniform diameter core wire segment beginning about 1.2 cm from the distal tip. The parabolic grind profile shown in Figures 35 and 36 provides a guidewire that has a linear change in stiffness, is flexible, and still maintains a high degree of torque on the distal end of the guidewire for navigating tortuous arteries and other blood vessels.

[0055] Conventional materials and manufacturing methods may be used to form the parabolic grinding profile of the presently disclosed guidewire. Those skilled in the art will be able to use a computerized grinding machine to form the parabolic grinding profile disclosed herein.

[0056] Although the present invention has been shown and described herein with respect to its use as a guidewire, it will be apparent to those skilled in the art that the guidewire may be used in any blood vessel in the body. All dimensions disclosed herein are by way of example only. Other modifications and improvements can be made without departing from the scope of the invention.

Claims

1. 1. A tool for preforming a bend in a distal end of a guidewire, said tool comprising: a forming tool having a first member and a second member having a common longitudinal axis, the second member being slidably contained within the first member; a spring disposed between the first member and the second member, spring biasing the first member away from the second member along the common longitudinal axis, the spring being fully enclosed within the forming tool; at least one cavity having an open end and a closed end, located in the second member and configured to receive a distal end of the guidewire such that a bend is formed in the distal end when the second member slides relative to the first member to overcome a spring force; A tool equipped with

2. The tool of claim 1 , wherein the at least one cavity is located in the second member, and each of the at least one cavity has a different depth and angle of bend.

3. a channel extends through a wall of the first member into each of the at least one cavity; The tool of claim 2 , sized to receive the distal end of the guidewire.

4. The tool of claim 3 , wherein the spring is disposed between the first member and the second member and is spring biased to maintain the molding tool in an open position so that the distal end of the guidewire can be inserted through the channel and into the at least one cavity.

5. The tool of claim 2 , wherein the depth of the at least one cavity is in the range of 0.5 mm to 6.0 mm.

6. The tool of claim 2 , wherein the at least one cavity has an angular bend range of 5 degrees to 40 degrees.

7. 2. The tool of claim 1, wherein a third member is attached to a slot of the first member such that the second member is held by the first member after the second member is inserted into the first member.

8. The tool of claim 7 , wherein the third member is attached to the slot by an adhesive, a laser weld, or fasteners.

9. The tool of claim 8 , wherein the second member is axially movable relative to the first member along the common longitudinal axis after the third member is attached to the slot.

10. The tool of claim 4 , wherein the mold tool has the open and closed positions.

11. The tool of claim 10 , wherein the spring is extended when the mold tool is in the open position and the spring is compressed when the mold tool is in the closed position.

12. The tool of claim 11 , wherein movement of the shaping tool to the closed position moves the location of the plurality of cavities relative to the respective channels, thereby imparting a predetermined bend to the distal end of the guidewire.

13. 13. The tool of claim 12, wherein the spring urges the first member relative to the second member to the open position to allow a user to release pressure on the second member and remove the guidewire from the molding tool.

14. The tool of claim 1 , wherein the mold tool includes at least one spring biasing the mold tool toward the open position.

15. The tool of claim 2 , wherein the depth of the cavity provides a predetermined length of the bend in the guidewire.

16. 1. A method of forming a bend in a distal end of a guidewire, the method comprising: providing a mold tool having a first member and a second member slidably contained within the first member; disposing a spring between the first member and the second member, thereby spring biasing the first member away from the second member and completely encapsulating the spring within the mold tool; inserting the distal end of the guidewire into an open end of a cavity located in the second member such that the distal end of the guidewire advances to a closed end of the child cavity; axially moving the second member relative to the first member along a common longitudinal axis to apply a force to overcome a spring force, thereby displacing the cavity and forming a bend in the distal end of the guidewire. The method includes:

17. The method of claim 16 , wherein the distal end of the guidewire is inserted into the cavity through a channel in a wall of the first member.

18. The method of claim 17 , wherein as the second member moves axially relative to the first member, the cavity moves relative to the channel, thereby imparting the bend to the distal end of the guidewire.

19. 20. The method of claim 18, further comprising removing the force axially moving the second member relative to the first member to move the cavity relative to the channel to allow removal of a guidewire through the channel.

20. 20. The method of claim 19, further comprising applying a spring force to the spring to spring bias the molding tool to an open position such that the distal end of the guidewire is inserted through the channel and into the cavity.

21. 21. The method of claim 20, further comprising applying a force to the second member to overcome the spring force to axially move the second member relative to the first member, thereby moving the cavity relative to the channel and imparting the bend to the distal end of the guidewire.

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