Guidewire and method for manufacturing the guidewire

Abstract

To improve resistance against torsional stress as a whole guide wire.SOLUTION: A guide wire includes: a first shaft; and a second shaft whose end is connected to a base end of the first shaft and formed by a material showing higher elastic rate than a material forming the first shaft. The second shaft has a rigidity change part which has a first part whose rigidity lowers as it goes from an end side of the second shaft to a base end side of the second shaft and a second part which is arranged nearer on the base end side of the second shaft than the first part and shows lower rigidity than that of the end of the first part. Length of the rigidity change part in an axial direction of the guide wire is longer than a diameter of the second shaft.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed herein relates to guidewires. [Background technology]

[0002] Methods using catheters are widely used to treat or examine stenosis or occlusion (hereinafter referred to as "lesion") in blood vessels, etc. Generally, a guidewire is used to guide the catheter to the lesion in blood vessels, etc. Some guidewires are known to include a first shaft and a second shaft whose distal end is joined to the proximal end of the first shaft and which is made of a material exhibiting a higher elastic modulus than the material forming the first shaft (see, for example, Patent Document 1). The first shaft, which is disposed on the distal end side of the guidewire, is made of a material with a relatively low elastic modulus, thereby ensuring relatively high flexibility. On the other hand, the second shaft, which is disposed on the proximal end side of the first shaft, is made of a material with a relatively high elastic modulus, thereby ensuring relatively high torque transmission from the proximal end side of the guidewire to the first shaft side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 113527 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described guidewire having a first shaft and a second shaft, for example, when the guidewire is rotated, the second shaft is subjected to a strong torsional stress due to the difference in hardness between the first shaft and the second shaft, which may result in, for example, a decrease in the operability and restorability of the guidewire. In other words, conventional guidewires as a whole have low durability against torsional stress.

[0005] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0006] The technology disclosed in this specification can be realized, for example, in the following forms.

[0007] (1) The guidewire disclosed in this specification is a guidewire comprising a first shaft and a second shaft whose tip is joined to the base end of the first shaft and formed of a material exhibiting a higher modulus of elasticity than the material forming the first shaft, wherein the second shaft has a hardness-changing portion having a first portion whose hardness decreases from the tip side of the second shaft toward the base end side of the second shaft, and a second portion that is located closer to the base end of the second shaft than the first portion and exhibits a hardness lower than the hardness of the tip of the first portion, and the length of the hardness-changing portion in the axial direction of the guidewire is longer than the diameter of the second shaft.

[0008] In this guidewire, the second shaft has a hardness change portion. The hardness change portion has a first portion whose hardness decreases from the distal end of the second shaft toward the proximal end of the second shaft, and a second portion that is located closer to the proximal end of the second shaft than the first portion and has a hardness lower than that of the distal end of the first portion. Therefore, with this guidewire, the durability of the second shaft as a whole against torsional stress is improved compared to a configuration in which the second shaft does not have a hardness change portion. Furthermore, the length of the hardness change portion in the axial direction of the guidewire is longer than the diameter of the second shaft. Therefore, with this guidewire, the durability of the second shaft as a whole against torsional stress is further improved compared to a configuration in which the length of the hardness change portion in the axial direction of the guidewire is shorter than the diameter of the second shaft. In this way, with this guidewire, the durability of the second shaft as a whole against torsional stress can be improved.

[0009] (2) In the above guidewire, the second shaft may have a distal end portion that includes the distal end of the second shaft, and the hardness change portion may be located closer to the proximal end of the second shaft than the distal end portion. With this guidewire, compared to a configuration in which the hardness change portion is located at the distal end of the second shaft, a portion with relatively low hardness exists at a position spaced from the junction between the first shaft and the second shaft toward the proximal end of the guidewire, thereby further improving the durability of the guidewire as a whole against torsional stress.

[0010] (3) In the above guidewire, the distal end portion of the second shaft may be configured to have a lower hardness than the distal end of the hardness varying portion. This guidewire can further improve the overall durability of the guidewire against torsional stress compared to a configuration in which the distal end portion of the second shaft has a higher hardness than the distal end of the hardness varying portion.

[0011] (4) In the above guidewire, the variable hardness portion may have a low-hardness portion exhibiting a lower hardness than the distal end portion of the second shaft. This guidewire can further improve the durability of the entire guidewire against torsional stress compared to a guidewire having a variable hardness portion without a low-hardness portion.

[0012] (5) In the above guidewire, the length of the low-hardness portion in the axial direction may be longer than the diameter of the second shaft. This guidewire can further improve the durability of the guidewire as a whole against torsional stress, compared to a guidewire configured such that the length of the low-hardness portion is shorter than the diameter of the second shaft.

[0013] (6) In the above guidewire, the hardness varying portion may include the tip of the second shaft. This guidewire can suppress unnecessary stress caused by a difference in hardness near the joint between the first shaft and the second shaft, compared to a guidewire in which the hardness varying portion does not include the tip of the second shaft.

[0014] (7) In the above guidewire, the second shaft may have a hardness increasing portion disposed closer to the base end of the second shaft than the hardness changing portion, the hardness of which increases from the tip end of the second shaft toward the base end of the second shaft. This guidewire allows for smooth rotational operation while improving durability against torsional stress, compared to a configuration in which the hardness of the second shaft increases stepwise on the base end side of the hardness changing portion.

[0015] (8) A method for manufacturing a guidewire disclosed in the present specification includes the steps of preparing a first shaft member and a second shaft member formed of a material exhibiting a higher elastic modulus than the material forming the first shaft member, joining a proximal end of the first shaft member to a distal end of the second shaft member, and softening a portion of the second shaft member that is located closer to the proximal end of the second shaft member than the joint between the first shaft member and the second shaft member by heat treatment. This method for manufacturing a guidewire can provide a guidewire that has improved durability against torsional stress as a whole.

[0016] In the manufacturing method (8) above, the guidewire may be the guidewire described in any one of (1) to (7) above.

[0017] The techniques disclosed in this specification can be realized in various forms, for example, in the form of a guidewire or a manufacturing method thereof. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a guidewire 100 according to a first embodiment. [Figure 2] FIG. 1 is an explanatory diagram showing Vickers hardness near the joint of the core shaft 10. [Figure 3] 1 is a flowchart showing the manufacturing process of the guidewire 100. [Figure 4] Illustrative diagram showing performance evaluation results from torsion tests [Figure 5] Graph showing the performance evaluation results from a tensile test [Figure 6] FIG. 10 is an explanatory diagram showing Vickers hardness in the vicinity of the joint of the core shaft 10 according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] A. First embodiment: A-1. Configuration of guidewire 100: FIG. 1 is an explanatory diagram schematically illustrating the configuration of a guidewire 100 according to a first embodiment. FIG. 1 illustrates a side view (YZ side view) of the core shaft 10 of the guidewire 100 and longitudinal cross sections (YZ cross sections) of the coil body 20 and the distal tip 30. In FIG. 1, the positive Z-axis direction corresponds to the distal end (distal side) inserted into the body, and the negative Z-axis direction corresponds to the proximal end (proximal side) manipulated by a surgeon such as a physician. While FIG. 1 illustrates the guidewire 100 as a whole in a linear shape substantially parallel to the Z-axis direction, the guidewire 100 is flexible enough to be bent. Hereinafter, the distal end and its vicinity will be referred to as the "distal end" and the proximal end and its vicinity will be referred to as the "proximal end" for the guidewire 100 and each of its constituent members.

[0020] The guidewire 100 is a medical device that is inserted into a blood vessel or the like to guide a catheter (not shown) to a lesion (a narrowed or blocked area) in the blood vessel or the like. The axial length of the guidewire 100 is, for example, about 150 cm or more and 300 cm or less.

[0021] As shown in FIG. 1, the guidewire 100 includes a core shaft 10, a coil body 20, a distal tip 30, and a proximal joint portion 40.

[0022] The core shaft 10 is a long member having a small diameter at the distal end and a large diameter at the proximal end. In this embodiment, the core shaft 10 has a distal shaft 12 and a proximal shaft 14. The distal shaft 12 is an example of a first shaft in the claims, and the proximal shaft 14 is an example of a second shaft in the claims.

[0023] The distal shaft 12 has a thin diameter section 11, a thick diameter section 13, and a tapered section 15. Note that part of the thick diameter section 13 is not shown in FIG. 1 . The thin diameter section 11 is a section that includes the distal end of the core shaft 10. The thin diameter section 11 is rod-shaped and has a circular cross section. The cross section is a cross section (XY cross section in this embodiment) perpendicular to the axial direction of the core shaft 10 (Z-axis direction in this embodiment). Note that in this embodiment, the axial direction of the core shaft 10 coincides with the axial direction of the guidewire 100. The thick diameter section 13 is located closer to the base end of the core shaft 10 than the thin diameter section 11, and has a rod-like cross section that is circular and has a larger outer diameter than the thin diameter section 11. The tapered section 15 is located between the thin diameter section 11 and the thick diameter section 13. The outer diameter of the tapered section 15 gradually increases from the boundary with the thin diameter section 11 toward the boundary with the thick diameter section 13. The outer diameter of the thin-diameter portion 11 is, for example, about 0.03 mm or more and 0.085 mm or less, and the outer diameter of the thick-diameter portion 13 is, for example, about 0.2 mm or more and 0.9 mm or less. The cross-sectional shape of each portion of the core shaft 10 is not particularly limited, and may be a polygon such as a triangle or a rectangle.

[0024] The proximal shaft 14 is located at the end of the proximal end of the core shaft 10 relative to the distal shaft 12, and the proximal end of the distal shaft 12 and the distal end of the proximal shaft 14 are joined by welding. The proximal shaft 14 has a circular rod-like cross section with approximately the same outer diameter as the large-diameter portion 13 of the distal shaft 12. The axial length of the distal shaft 12 is approximately 10 cm or more and 50 cm or less, and the axial length of the proximal shaft 14 is approximately 100 cm or more and 200 cm or less.

[0025] The core shaft 10 is made of a known material, such as a metal material, more specifically, stainless steel (SUS302, SUS304, SUS316, etc.), a superelastic alloy such as a Ni-Ti alloy, piano wire, a nickel-chromium alloy, a cobalt alloy, or tungsten. However, the elastic modulus of the material forming the proximal shaft 14 is higher than that of the material forming the distal shaft 12. In this embodiment, for example, the material forming the distal shaft 12 is a Ni-Ti alloy, and the material forming the proximal shaft 14 is stainless steel.

[0026] 1, the coil body 20 is, for example, a coil-shaped member formed into a hollow cylinder by spirally winding a single wire. In this embodiment, the coil body 20 is arranged so as to surround the outer periphery of the tip end portion of the core shaft 10 (specifically, the small diameter portion 11, the tapered portion 15, and part of the large diameter portion 13). An inner cavity H is formed between the core shaft 10 and the coil body 20. The total length of the coil body 20 is, for example, about 10 mm or more and 500 mm or less, and the outer diameter of the coil body 20 is, for example, about 0.2 mm or more and 0.9 mm or less.

[0027] The coil body 20 is made of a known material, such as a metal material, more specifically, platinum, stainless steel (SUS302, SUS304, SUS316, etc.), superelastic alloys such as Ni-Ti alloys, piano wire, nickel-chromium alloys, cobalt alloys, tungsten, etc.

[0028] The distal tip 30 is a member that joins the distal end of the core shaft 10 and the distal end of the coil body 20. The distal end of the core shaft 10 and the distal end of the coil body 20 are embedded and fixed inside the distal tip 30. The outer peripheral surface on the distal side of the distal tip 30 is a smooth surface (for example, a substantially hemispherical or cylindrical surface). The distal tip 30 is made of a known material, such as a brazing material (aluminum alloy brazing, silver brazing, gold brazing, etc.), a metal solder (Ag-Sn alloy, Au-Sn alloy, etc.), or an adhesive (epoxy adhesive, etc.). In this embodiment, an Ag-Sn alloy is used as the material that constitutes the distal tip 30.

[0029] The base-end joint 40 is a member that joins the base-end side (large diameter portion 13) of the distal shaft 12 of the core shaft 10 to the base-end side of the coil body 20. A known material is used to form the base-end joint 40, such as a brazing material (aluminum alloy brazing, silver brazing, gold brazing, etc.), a metal solder (Ag—Sn alloy, Au—Sn alloy, etc.), or an adhesive (epoxy adhesive, etc.). In this embodiment, an Ag—Sn alloy is used as the material to form the base-end joint 40.

[0030] A-2. Detailed configuration of the joint area of ​​the core shaft 10: FIG. 2 is an explanatory diagram showing the Vickers hardness near the joint of the core shaft 10. In FIG. 2, the vertical axis represents Vickers hardness (Hv), and the horizontal axis represents the relative distance from the joint interface in the axial direction of the core shaft 10. "0" on the horizontal axis represents the position of the joint interface of the core shaft 10 (the joint portion between the distal shaft 12 and the proximal shaft 14). In FIG. 2, the Vickers hardness of the distal shaft 12 is shown on the left side of the joint interface, and the Vickers hardness of the proximal shaft 14 is shown on the right side of the joint interface. In FIG. 2, graph G1 represents the Vickers hardness of the guidewire 100 of this embodiment, and graph G2 represents the Vickers hardness of a guidewire of a comparative example (not shown). The comparative examples are Samples 1 to 4 and G31 to G33, which will be described later.

[0031] The Vickers hardness of each portion of the core shaft 10 is measured as follows. The Vickers hardness is measured according to a method conforming to JIS 2244. In this embodiment, the Vickers hardness is measured at the center (near the central axis) of each portion of the core shaft 10 and used as the hardness of each portion. That is, a test piece near the joint of the core shaft 10 is cut along the axial direction to obtain a longitudinal cross section (YZ cross section) including the center. A pyramidal indenter is then pressed against the longitudinal cross section of the test piece with a constant load (test force: F (N), 0.1 N / sec), and the average diagonal length d (mm) of the indentation (depression) formed when the indenter is removed is measured. The Vickers hardness is determined by substituting the test force F and the average diagonal length d into the following equation. The load (test force) used in this test was 1 N. The load (test force) is preferably 1 N, and the Vickers hardness measured under a load of 1 N or less is sometimes called micro Vickers hardness. Vickers hardness = 0.01891 x F / d 2

[0032] As shown in FIG. 2, the proximal shaft 14 has a hardness transition portion 68. The hardness transition portion 68 has a first portion 68A and a second portion 68B. The first portion 68A is a portion whose hardness decreases from the distal end of the proximal shaft 14 toward the proximal end of the proximal shaft 14. The second portion 68B is located closer to the proximal end of the proximal shaft 14 than the first portion 68A and has a hardness lower than that of the distal end of the first portion 68A. In this embodiment, the first portion 68A and the second portion 68B are adjacent to each other in the axial direction. Also, as shown in FIG. 2, in the hardness transition portion 68, the hardness continuously decreases from the distal end of the hardness transition portion 68 toward the center of the hardness transition portion 68 and continuously increases from the center toward the proximal end of the hardness transition portion 68. The length of the hardness varying portion 68 in the axial direction of the guidewire 100 is longer than the diameter D (see FIG. 1) of the proximal shaft 14. In this embodiment, the length of the hardness varying portion 68 is, for example, 1500 μm or more, about 1700 μm.

[0033] The proximal shaft 14 further has a distal end portion 66. The distal end portion 66 includes the distal end of the proximal shaft 14 (the distal end surface facing the bonded interface). That is, the hardness varying portion 68 is disposed closer to the proximal end of the proximal shaft 14 than the distal end portion 66. In this embodiment, the distal end portion 66 and the hardness varying portion 68 are adjacent to each other in the axial direction. The hardness of the distal end portion 66 is lower than the hardness of the distal end of the hardness varying portion 68.

[0034] The hardness varying portion 68 has a low hardness portion 70. The low hardness portion 70 is a portion of the hardness varying portion 68 that exhibits a hardness lower than that of the tip portion 66 of the proximal shaft 14. In this embodiment, as shown in FIG. 2 , in the low hardness portion 70, the hardness continuously decreases from the tip of the low hardness portion 70 to the center of the low hardness portion 70, and the hardness continuously increases from the center to the proximal end of the low hardness portion 70. Furthermore, the length of the low hardness portion 70 in the axial direction (Z-axis direction) is longer than the diameter D of the proximal shaft 14.

[0035] The proximal shaft 14 has a hardness increasing portion 72. The hardness increasing portion 72 is located closer to the proximal end of the proximal shaft 14 than the hardness changing portion 68. The hardness increasing portion 72 is a portion where the hardness increases from the distal end of the proximal shaft 14 toward the proximal end of the proximal shaft 14. The hardness increasing portion 72 has a steep portion 74. The angle of inclination of the steep portion 74 with respect to the axial direction of the guidewire 100 is greater than the angle of inclination of the hardness changing portion 68 with respect to the axial direction of the guidewire 100. In other words, the hardness of the proximal shaft 14 increases sharply at the steep portion 74.

[0036] The distal shaft 12 has a base end 62 that includes the base end of the distal shaft 12. The hardness of the base end 62 is lower than the hardness of the portion of the distal shaft 12 that is closer to the tip than the base end 62. The base end 62 of the distal shaft 12 and the distal end 66 of the proximal shaft 14 are welded together in a joining step (S120) of the manufacturing method, which will be described later.

[0037] A-3. Method of manufacturing guidewire 100: 3 is a flowchart showing the manufacturing process of the guidewire 100. The guidewire 100 of this embodiment can be manufactured, for example, by the following method.

[0038] As shown in FIG. 3, first, a distal shaft member 12P and a proximal shaft member 14P are prepared by machining or the like (S110). The distal shaft member 12P corresponds to the distal shaft 12 before being joined (welded) to the proximal shaft member 14P. The proximal shaft member 14P corresponds to the proximal shaft 14 before being joined (welded) to the distal shaft member 12P. The elastic modulus of the material (e.g., stainless steel) forming the proximal shaft member 14P is higher than the elastic modulus of the material (e.g., Ni-Ti alloy) forming the distal shaft member 12P. The distal shaft member 12P is an example of a first shaft member in the claims, and the proximal shaft member 14P is an example of a second shaft member in the claims.

[0039] Next, the base end of the distal shaft member 12P and the distal end of the proximal shaft member 14P are welded together (S120). This welding forms a welded portion (the proximal end portion 62 of the distal shaft 12 and the distal end portion 66 of the proximal shaft 14) at the joint between the distal shaft member 12P and the proximal shaft member 14P.

[0040] Next, a portion of the proximal shaft 14 located closer to the proximal end of the proximal shaft 14 than the welded portion is softened by heat treatment (S130). A known method can be used for the heat treatment, for example, an electric current method in which an electric current is passed between both ends of the portion to be heat treated to generate heat, or a laser beam can be irradiated onto the portion to be heat treated to heat it. This produces a core shaft 10 having the hardness-changed portion 68 and the like in addition to the welded portion. As a result of this heat treatment, in the guidewire 100, the heat-affected area (the distal end 66, the hardness-changed portion 68, and the hardness-increased portion 72) of the proximal shaft 14 of the core shaft 10 due to the welding is longer than the heat-affected area (the proximal end 62) of the distal shaft 12. For example, if the proximal shaft 14 is made of stainless steel, the portion of the proximal shaft 14 corresponding to the hardness-changed portion 68 is heated to a temperature range of 300°C to 800°C.

[0041] Next, the coil body 20 is joined to the core shaft 10 (S140). Specifically, the coil body 20 is prepared by winding a coil wire, and the core shaft 10 is inserted into the hollow portion of the coil body 20 to form the distal tip 30 and the proximal joint portion 40 that join the coil body 20 to the core shaft 10. The distal tip 30 is formed, for example, by injecting molten resin into a mold capable of forming the shape of the distal tip 30, immersing the distal portions of the core shaft 10 and the coil body 20 in the resin, and cooling the resin. The proximal joint portion 40 is formed by brazing the proximal end of the coil body 20 to the core shaft 10. For example, the guidewire 100 having the above-described configuration can be manufactured by the above-described method.

[0042] A-4. Advantages of this embodiment: As described above, the guidewire 100 of this embodiment includes a core shaft 10 having a distal shaft 12 and a proximal shaft 14 (see FIG. 1). The distal end of the proximal shaft 14 is joined to the proximal end of the distal shaft 12. The proximal shaft 14 is formed of a material exhibiting a higher modulus of elasticity than the material forming the distal shaft 12. The proximal shaft 14 has a hardness transition portion 68 (see FIG. 2). The hardness transition portion 68 has a first portion 68A and a second portion 68B. The first portion 68A is a portion whose hardness decreases from the distal end side of the proximal shaft 14 toward the proximal end side of the proximal shaft 14. The second portion 68B is located closer to the proximal end of the proximal shaft 14 than the first portion 68A and exhibits a hardness lower than that of the distal end of the first portion 68A.

[0043] For this reason, in this embodiment, the durability of the proximal shaft 14 as a whole against torsional stress is improved compared to a configuration in which the proximal shaft 14 does not have the variable hardness portion 68. Furthermore, the length of the variable hardness portion 68 in the axial direction of the guidewire 100 is longer than the diameter of the proximal shaft 14. For this reason, in this embodiment, the durability of the proximal shaft 14 as a whole against torsional stress is further improved compared to a configuration in which the length of the variable hardness portion 68 is shorter than the diameter of the proximal shaft 14. As described above, according to this embodiment, the durability of the proximal shaft 14 as a whole against torsional stress can be improved by improving the durability of the proximal shaft 14, which has a relatively high elastic modulus, against torsional stress. Note that the length of the variable hardness portion 68 in the axial direction of the guidewire 100 is, for example, less than one-hundredth of the length of the proximal shaft 14, and therefore the presence of the variable hardness portion 68 does not significantly reduce the torque transmissibility of the proximal shaft 14.

[0044] In this embodiment, the proximal shaft 14 further has a distal end portion 66 (see FIG. 2 ). The distal end portion 66 includes the distal end of the proximal shaft 14. Therefore, in this embodiment, compared to a configuration in which the variable hardness portion 68 is located at the distal end of the proximal shaft 14, a portion with relatively low hardness is present at a position spaced from the joint between the distal shaft 12 and the proximal shaft 14 toward the proximal end of the guidewire 100. Therefore, according to this embodiment, the durability of the guidewire 100 as a whole against torsional stress can be further improved. Furthermore, in this embodiment, the variable hardness portion 68 is located closer to the proximal end of the guidewire 100 than the welded portion (the proximal end portion 62 of the distal shaft 12 and the distal end portion 66 of the proximal shaft 14) which is inherently low in hardness. Therefore, the durability of the guidewire 100 as a whole against torsional stress is improved while suppressing a decrease in the joint strength of the welded portion joining the distal shaft 12 and the proximal shaft 14.

[0045] In the present embodiment, the hardness of the distal end portion 66 is lower than the hardness of the distal end of the hardness change portion 68. Therefore, according to the present embodiment, the durability of the guidewire 100 as a whole against torsional stress can be further improved compared to a configuration in which the hardness of the distal end portion 66 of the proximal shaft 14 is higher than the hardness of the distal end of the hardness change portion 68. Furthermore, a portion with relatively high hardness is present at the boundary between the distal end portion 66 and the hardness change portion 68. Therefore, compared to a configuration in which a portion with relatively high hardness is not present at the boundary between the distal end portion 66 and the hardness change portion 68, for example, the portion over which a continuous portion with low hardness exists in the axial direction is shorter, thereby suppressing a decrease in torque transmissibility of the proximal shaft 14 due to the presence of the hardness change portion 68.

[0046] In this embodiment, the variable hardness portion 68 has a low hardness portion 70. The low hardness portion 70 is a portion of the variable hardness portion 68 that exhibits a hardness lower than that of the distal end portion 66 of the proximal shaft 14. Therefore, according to this embodiment, the durability of the guidewire 100 as a whole against torsional stress can be further improved compared to a configuration in which the variable hardness portion 68 does not have the low hardness portion 70.

[0047] In this embodiment, the length of the low-hardness portion 70 in the axial direction (Z-axis direction) is longer than the diameter D of the proximal shaft 14. Therefore, according to this embodiment, the durability of the guidewire 100 as a whole against torsional stress can be further improved compared to a configuration in which the length of the low-hardness portion 70 is shorter than the diameter of the proximal shaft 14.

[0048] In the present embodiment, the proximal shaft 14 has an increasing hardness portion 72. The increasing hardness portion 72 is located closer to the proximal end of the proximal shaft 14 than the varying hardness portion 68. The increasing hardness portion 72 is a portion in which the hardness increases from the distal end of the proximal shaft 14 toward the proximal end of the proximal shaft 14. Therefore, according to the present embodiment, the guidewire 100 can be smoothly rotated while improving durability against torsional stress compared to, for example, a configuration in which the hardness increases stepwise on the proximal side of the varying hardness portion 68 in the proximal shaft 14.

[0049] A-5. Performance evaluation: The performance evaluation conducted using multiple core shaft 10 samples will be described below. FIG. 4 is an explanatory diagram showing the performance evaluation results of a torsion test. Samples 1 to 8 were all formed by joining the distal shaft member 12P (made of Ni-Ti alloy) and the proximal shaft member 14P (made of stainless steel) by welding (see S120 in FIG. 3), and were produced under the same conditions. However, Samples 1 to 4 were not subjected to the heat treatment (S130 in FIG. 3) for forming the hardness-varying portion 68, while Samples 5 to 8 were subjected to the heat treatment under the same conditions. This heat treatment heated the portion of the proximal shaft member 14 corresponding to the hardness-varying portion 68 to a temperature of approximately 500°C. The axial length of each of Samples 1 to 8 was approximately 100 mm, and the joining interface was located at the axial center of each sample. Furthermore, each of Samples 1 to 8 had a diameter of approximately 0.3 mm.

[0050] A torsion test was conducted in which a torsional force was applied to each of Samples 1 to 8. In the torsion test, one end of each of Samples 1 to 8 was fixed, and the other end was rotated to apply a torsional force. The "number of twists" in Figure 4 is the number of twists at which each of Samples 1 to 8 broke. The rotation direction was opposite for Samples 1, 3, 5, and 7 and Samples 2, 4, 6, and 8.

[0051] 4, the results of the torsion test show that the number of twists for Samples 5 to 8 was generally greater than the number of twists for Samples 1 to 4. This means that by subjecting the proximal shaft 14 to heat treatment to form the hardness-changed portion 68, the durability of the guidewire 100 as a whole against torsional stress is improved.

[0052] FIG. 5 is an explanatory diagram showing the results of performance evaluation by tensile testing. Samples G31 to G43 were all prepared by welding (see S120 in FIG. 3) the distal shaft member 12P (made of Ni-Ti alloy) and the proximal shaft member 14P (made of stainless steel) described above, and were all produced under the same conditions. However, samples G31 to G33 were not subjected to the heat treatment (S130 in FIG. 3) for forming the hardness-varying portion 68, whereas samples G41 to G43 were subjected to the heat treatment under the same conditions. This heat treatment heated the portion of the proximal shaft member 14 corresponding to the hardness-varying portion 68 to a temperature of approximately 500°C. The axial length of each of samples G31 to G43 was approximately 100 mm, and the bonded interface was located at the axial center of each sample. Furthermore, each of samples G31 to G43 had a diameter of approximately 0.3 mm.

[0053] A tensile test was carried out on each of the samples G31 to G43. The tensile test conditions were standard conditions (temperature 20°C, relative humidity 65%), a pulling speed of 200 mm / min, and a grip distance of 100 mm. The load (tensile strength (N / mm 2 )) and elongation (%) were measured.

[0054] As shown in FIG. 5, the results of the tensile test showed that samples G31 to G43 all had similar tensile strength and elongation. In addition, the tensile strength variation range was within a predetermined range (700 N / mm 2 More than 900N / mm 2 The elongation variation range is within a predetermined range (4% or more and 5.5% or less). This means that even if the proximal shaft 14 is subjected to a heat treatment to form the hardness-changed portion 68, the strength of the guide wire 100 is not reduced.

[0055] B. Second embodiment: 6 is an explanatory diagram showing the Vickers hardness near the joint of the core shaft 10a in the second embodiment. In the following, among the configurations of the core shaft 10a in the second embodiment, the same configurations as those of the core shaft 10 in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0056] The core shaft 10a of the second embodiment differs from the core shaft 10 of the first embodiment in the configuration of the proximal shaft 14a. That is, in the proximal shaft 14 of the first embodiment, the distal end portion 66 is formed closer to the distal end of the proximal shaft 14 than the hardness varying portion 68. In contrast, in the proximal shaft 14a of the second embodiment, the hardness varying portion 68 includes the distal end of the proximal shaft 14. As a result, according to the second embodiment, it is possible to suppress the generation of unnecessary stress due to the difference in hardness near the joint between the distal shaft 12 and the proximal shaft 14a, compared to a configuration in which the hardness varying portion 68 does not include the distal end of the proximal shaft 14a.

[0057] C. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the spirit thereof, for example, the following modifications are also possible.

[0058] The configurations of the guidewire 100 and core shafts 10, 10a in the above-described embodiment are merely examples and can be modified in various ways. For example, the distal shaft 12 may be cylindrical with a constant outer diameter along its entire length. Furthermore, the distal shaft 12 and the proximal shafts 14, 14a may be joined by other joining methods (e.g., adhesive bonding) rather than by welding.

[0059] In each of the above embodiments, the Vickers hardness was measured at the center (near the central axis) of each part of the core shaft 10, 10a and used as the hardness of each part, but this is not limited to this. For example, the Vickers hardness may be measured on the outer peripheral surface of each part of the core shaft 10, 10a and used as the hardness of each part.

[0060] In the first embodiment, the hardness of the distal end portion 66 of the core shaft 10 may be the same as or higher than the hardness of the distal end of the hardness changing portion 68. In each of the above embodiments, the hardness changing portion 68 of the core shaft 10, 10a may not have a low hardness portion 70. In each of the above embodiments, the length of the low hardness portion 70 in the axial direction may be the same as or shorter than the diameter D of the proximal shaft 14. In each of the above embodiments, the proximal shaft 14 may not have a hardness increasing portion 72.

[0061] The materials of the components in the above-described embodiments are merely examples and can be modified in various ways. Furthermore, the manufacturing method of the guidewire in the above-described embodiments is merely an example and can be modified in various ways. [Explanation of symbols]

[0062] 10, 10a: Core shaft 11: Thin diameter portion 12: Distal shaft 12P: Distal shaft member 13: Thick diameter portion 14, 14a: Base end shaft 14P: Base end shaft member 15: Tapered portion 20: Coil body 30: Distal tip 40: Base end joint portion 62: Base end portion 66: Distal portion 68: Hardness change portion 68A: First portion 68B: Second portion 70: Low hardness portion 72: Hardness increase portion 74: Steep portion 100: Guide wire H: Lumen

Claims

1. A guidewire comprising: a first shaft formed from a first material; and a second shaft formed from a second material having a tip joined to the base end of the first shaft and exhibiting a higher modulus of elasticity than the material forming the first shaft, The second shaft includes: a hardness varying portion including a first portion whose hardness decreases from the tip end side of the second shaft toward the base end side of the second shaft, and a second portion that is located closer to the base end side of the second shaft than the first portion and has a hardness lower than the hardness of the tip end of the first portion, a length of the variable hardness portion in the axial direction of the guide wire is longer than a diameter of the second shaft; the hardness is a Vickers hardness at the center of each portion in a longitudinal cross section including the center of the second shaft, The second shaft has a hardness increasing portion that is disposed closer to the base end of the second shaft than the hardness changing portion, and the hardness increases from the tip end side of the second shaft toward the base end side of the second shaft. Guide wire.

2. 2. The guidewire of claim 1, the second shaft has a tip portion that includes the tip of the second shaft; the hardness varying portion is disposed closer to the base end of the second shaft than the tip portion. Guide wire.

3. 3. The guidewire according to claim 2, the tip portion of the second shaft exhibits a lower hardness than the tip of the hardness varying portion; Guide wire.

4. The guide wire according to claim 2 or 3, the hardness varying portion has a low hardness portion exhibiting a hardness lower than that of the tip portion of the second shaft. Guide wire.

5. 5. The guidewire according to claim 4, a length of the low hardness portion in the axial direction is longer than the diameter of the second shaft; Guide wire.

6. 2. The guidewire of claim 1, the variable hardness portion includes the tip of the second shaft. Guide wire.

7. A method for manufacturing the guide wire according to any one of claims 1 to 6, comprising: providing a first shaft member and a second shaft member formed from a material exhibiting a higher modulus of elasticity than the material forming the first shaft member; joining a proximal end of the first shaft member and a distal end of the second shaft member; a step of softening a portion of the second shaft member that is located closer to the base end of the second shaft member than the joint between the first shaft member and the second shaft member by performing a heat treatment; A method for manufacturing a guidewire, comprising:

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