Guide wire

Abstract

A core shaft provided in a guide wire according to the present invention comprises: a first shaft including a first tip end and a first base end on the opposite side thereof from the first tip end; and a second shaft including a second tip end connected to the first base end and having a hardness higher than that of the first shaft. The second shaft comprises: a reduced section that is disposed near the second tip end and has a cross-sectional area smaller than the area of ​​the base end surface of the first shaft; a base section that is disposed farther from the first base end than the reduced section and has a constant cross-sectional area larger than the cross-sectional area of ​​the reduced section; and an intermediate section that is disposed between the reduced section and the base section and has a cross-sectional area that increases continuously or in a stepwise manner from the reduced section to the base section. The cross section of the reduced section has a rotationally symmetric shape. When the sum of the length of the reduced section and the length of the intermediate section is denoted by L1 and the minimum value of the length of a straight line that passes through the center of rotation and connects two points on the outer peripheral edge of the cross section of the reduced section is denoted by L2, L1 ≥ L2 × 10 is satisfied.

Description

Guidewire

[0001] The technology disclosed herein relates to guidewires.

[0002] The guide wire disclosed in Patent Document 1 includes, for example, a first shaft arranged at the tip side, and a second shaft arranged at the base end side of the first shaft and made of a material having a greater elastic modulus than the material constituting the first shaft.

[0003] Patent No. 4138583

[0004] The above guidewire has room for improvement in rotation durability.

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

[0006] The technology disclosed in this specification can be realized in the following forms, for example: (1) A guidewire disclosed by this specification includes a core shaft, the core shaft including a first shaft having a first tip and a first base end opposite the first tip, and a second shaft having a second tip connected to the first base end and having a higher hardness than the first shaft, the second shaft including a reduced section disposed near the second tip and having a cross-sectional area smaller than the area of ​​the base-end face of the first shaft, a base section disposed farther from the first base end than the reduced section and having a constant cross-sectional area larger than the cross-sectional area of ​​the reduced section, and an intermediate section disposed between the reduced section and the base and having a cross-sectional area larger than the cross-sectional area of ​​the reduced section and smaller than the cross-sectional area of ​​the base, the cross-section of the reduced section having a rotationally symmetric shape, and satisfying the following formula (1) when the sum of the lengths of the reduced section and the intermediate section is L1 and the minimum length of a straight line passing through the center of rotation and connecting two points on the outer circumferential edge in the cross-section of the reduced section is L2: L1 ≧ L2 × 10 (1)

[0007] According to the above configuration, the rotation durability of the guidewire is improved.

[0008] (2) The guide wire described in (1) above may satisfy the following formula (2): L1≧L2×100 (2)

[0009] This configuration further improves the rotation durability of the guidewire.

[0010] (3) In the guidewire described in (1) or (2) above, the cross-sectional area of ​​the intermediate portion may increase stepwise from the reduced portion toward the base portion.

[0011] With this configuration, the rotation durability of the guidewire is further improved, and distortion of the curved shape when the core shaft is bent can be suppressed.

[0012] (4) In the guide wire described in (3) above, the intermediate portion may comprise a first increasing portion, a constant portion, and a second increasing portion, arranged in this order from the second tip side, and the cross-sectional area of ​​the first increasing portion may increase as it approaches the base, the cross-sectional area of ​​the constant portion may be constant, and the cross-sectional area of ​​the second increasing portion may increase as it approaches the base.

[0013] This configuration increases the rotational durability of the guidewire and makes it easier to design the guidewire.

[0014] (5) In the guidewire described in (1) or (2) above, the cross-sectional area of ​​the intermediate portion may increase continuously from the reduced portion toward the base portion.

[0015] With this configuration, the rotation durability of the guidewire is further improved, and distortion of the curved shape when the core shaft is bent can be suppressed.

[0016] 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.

[0017] 1 is a cross-sectional view of a guide wire according to a first embodiment; 2 is a transverse cross-sectional view of a reduced portion according to the first embodiment; 3 is a cross-sectional view of a guide wire according to a second embodiment; and 4 is a cross-sectional view of a guide wire according to a third embodiment. 5 is a graph showing the relationship between the L1 / L2 value and the number of rotations until the core shaft breaks in a rotation durability test using samples S1-S10. 6 is a graph showing the relationship between the L1 / L2 value and the number of rotations until the core shaft breaks in a rotation durability test using samples S11-S16.

[0018] A. First Embodiment: The first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is an explanatory diagram schematically illustrating a guidewire 10 according to an embodiment. FIG. 1 shows a longitudinal cross section of the guidewire 10. The longitudinal cross section is a YZ cross section. In the guidewire 10, the positive Z-axis side is the tip side that is inserted into the body, and the negative Z-axis side is the base side that is manipulated by a surgeon such as a doctor. The tip side is the distal side. The base side is the proximal side. In each drawing, illustration of a portion of the guidewire 10 may be omitted. FIG. 1 shows the guidewire 10 in a state in which the entire guidewire 10 is linear and substantially parallel to the Z-axis direction. The guidewire 10 is flexible enough to be bent. These points also apply to the subsequent drawings.

[0019] In this specification, the distal end of the guidewire 10 and each of its constituent parts is referred to as the "tip," the distal end and its vicinity are referred to as the "tip portion," the proximal end is referred to as the "proximal end," and the proximal end and its vicinity are referred to as the "proximal end portion."

[0020] The guidewire 10 is a medical device that is inserted into a body lumen, such as a blood vessel, to guide a catheter (not shown) to a lesion in the body lumen. The length of the guidewire 10 is, for example, 1500 mm or more and 3000 mm or less.

[0021] As shown in FIG. 1 , the guidewire 10 includes a core shaft 100 , a coil body 200 , a distal joint portion 300 , and a proximal joint portion 400 .

[0022] As shown in Fig. 1 , the core shaft 100 is a long, thin wire that can be bent. The core shaft 100 includes a first shaft 110 and a second shaft 120 arranged in this order from the tip. The first shaft 110 and the second shaft 120 are arranged coaxially along the central axis Ax of the core shaft 100. In this specification, the cross section of the core shaft 100 and its constituent members refers to the plane of a cut when the core shaft 100 and its constituent members are cut perpendicular to the central axis Ax.

[0023] The material forming the core shaft 100 is, for example, a metal material, and more specifically, stainless steel such as SUS301, SUS302, SUS303, SUS304, SUS305, SUS306, SUS309, SUS310, SUS316, SUS317, SUS321, SUS347, and SUS384, superelastic alloys such as Ni-Ti alloys, piano wire, nickel-chromium alloys, cobalt alloys, tungsten, etc. The hardness of the second shaft 120 is higher than the hardness of the first shaft 110. In this specification, "hardness" refers to Vickers hardness. In this embodiment, the material of the first shaft 110 is a Ni-Ti alloy, and the material of the second shaft 120 is stainless steel. The stainless steel may be, for example, austenitic stainless steel. The relatively low hardness of first shaft 110 ensures relatively high flexibility at the distal end of guidewire 10. The relatively high hardness of second shaft 120 ensures relatively high torque transmissibility at the proximal end of guidewire 10.

[0024] The first shaft 110 is a thin wire having a circular cross section, with its tip end designated as a first tip end 111 and its base end designated as a first base end 112. The length of the first shaft 110 is, for example, 100 mm or more and 500 mm or less. The first shaft 110 includes a thin wire portion 113, a tapered portion 114, and a thick wire portion 115, arranged in this order from the tip end. The thin wire portion 113 includes the first tip end 111 and has a constant outer diameter, i.e., a constant cross-sectional area. The thick wire portion 115 includes the first base end 112 and has a constant outer diameter larger than the outer diameter of the thin wire portion 113, i.e., a constant cross-sectional area larger than the cross-sectional area of ​​the thin wire portion 113. The tapered portion 114 is a portion connecting the thin wire portion 113 and the thick wire portion 115. The outer diameter of the tapered portion 114 continuously decreases from the thick wire portion 115 toward the thin wire portion 113. That is, the cross-sectional area of ​​the tapered portion 114 continuously decreases from the thick wire portion 115 toward the thin wire portion 113. The outer diameter of the thin wire portion 113 is 0.03 mm or more and 0.085 mm or less, and the outer diameter of the thick wire portion 115 is, for example, 0.1 mm or more and 10 mm or less.

[0025] The second shaft 120 is a thin wire having a circular cross section, with its tip end being a second tip end 121 and its base end being a second base end 122. The length of the second shaft 120 is, for example, 1000 mm or more and 2000 mm or less. The second tip end 121 is joined to the first base end 112 by, for example, welding. The second shaft 120 includes, arranged in this order from the tip, a fixed portion 130, a connecting portion 140, a reducing portion 150, an intermediate portion 160, and a base portion 170.

[0026] The fixed portion 130 is a short, thin wire having a circular cross-section, includes the second tip 121, and has a constant outer diameter equal to the outer diameter of the thick wire portion 115, that is, a portion having a constant cross-sectional area equal to the cross-sectional area of ​​the thick wire portion 115.

[0027] The connecting portion 140 is disposed between the fixed-shape portion 130 and the contracting portion 150 and connects them. The connecting portion 140 is a short, thin wire with a circular cross section. The outer diameter of the connecting portion 140 continuously decreases from the fixed-shape portion 130 toward the contracting portion 150. In other words, the cross-sectional area of ​​the connecting portion 140 continuously decreases from the fixed-shape portion 130 toward the contracting portion 150.

[0028] It is preferable that the fixed portion 130 and the connecting portion 140 be as short as possible. This is to arrange the reducing portion 150 as close as possible to the second tip 121 and relieve stress that occurs at the joint between the first shaft 110 and the second shaft 120 due to twisting of the guidewire 10. The length of the fixed portion 130 may be, for example, 0.1 mm to 10 mm, or 1 mm to 5 mm. The length of the connecting portion 140 may be, for example, 0.1 mm to 5 mm, or 0.1 mm to 3 mm.

[0029] The reduced portion 150 is a short, thin, linear portion with a circular cross section that is connected to the connecting portion 140. The reduced portion 150 has a constant outer diameter that is smaller than the outer diameter of the thick line portion 115, i.e., a constant cross-sectional area that is smaller than the cross-sectional area of ​​the thick line portion 115. In other words, the cross-sectional area of ​​the reduced portion 150 is smaller than the area of ​​the base end surface 112S, which is the end surface on the base end side of the first shaft 110. The reduced portion 150 is the portion of the second shaft 120 with the smallest cross-sectional area.

[0030] The base portion 170 is a thin wire-like portion having a circular cross section and located farther from the first base end 112 than the reduced portion 150. The base portion 170 has a constant outer diameter larger than the outer diameter of the reduced portion 150, i.e., a constant cross-sectional area larger than the cross-sectional area of ​​the reduced portion 150. More specifically, the base portion 170 includes the second base end 122 and has a constant outer diameter equal to the outer diameter of the thick wire portion 115, i.e., a constant cross-sectional area equal to the cross-sectional area of ​​the thick wire portion 115. The second shaft 120 is typically obtained by processing a wire having a substantially constant outer diameter and cross-sectional area to form the reduced portion 150 and the intermediate portion 160. The base portion 170 has the constant outer diameter and cross-sectional area of ​​the wire before processing. Typically, from the viewpoint of productivity, processing to change the outer diameter and cross-sectional area of ​​the wire as described above is performed over a length that is 50% or less of the total length of second shaft 120, and therefore base portion 170 typically has a constant outer diameter and cross-sectional area that occupies 50% or more of the total length of second shaft 120. The portion of base portion 170 near second base end 122 is a gripping portion that is gripped by a technician such as a doctor.

[0031] The intermediate portion 160 is disposed between the reduced portion 150 and the base portion 170 and connects them. The cross-sectional area of ​​the intermediate portion 160 is larger than that of the reduced portion 150 and smaller than that of the base portion 170 over the entire length. In this embodiment, the outer diameter of the intermediate portion 160 increases stepwise from the reduced portion 150 to the base portion 170. In other words, the cross-sectional area of ​​the intermediate portion 160 increases stepwise from the reduced portion 150 to the base portion 170. The intermediate portion 160 includes a first increasing portion 161, a constant portion 162, and a second increasing portion 163, which are disposed in this order from the second tip 121 side.

[0032] The constant portion 162 is a portion having a constant outer diameter that is larger than the outer diameter of the contracting portion 150 and smaller than the outer diameter of the base portion 170. In other words, the constant portion 162 has a constant cross-sectional area that is larger than the cross-sectional area of ​​the contracting portion 150 and smaller than the cross-sectional area of ​​the base portion 170.

[0033] The first increasing portion 161 is disposed between the contracting portion 150 and the constant portion 162 and connects them. The outer diameter, i.e., the cross-sectional area, of the first increasing portion 161 is larger than that of the contracting portion 150 and smaller than that of the constant portion 162. The cross-sectional area of ​​the first increasing portion 161 continuously increases from the contracting portion 150 toward the constant portion 162, i.e., as it approaches the base portion 170.

[0034] The second increasing portion 163 is disposed between the constant portion 162 and the base portion 170 and connects them. The outer diameter, i.e., the cross-sectional area, of the second increasing portion 163 is larger than that of the constant portion 162 and smaller than that of the base portion 170. The cross-sectional area of ​​the second increasing portion 163 increases continuously from the constant portion 162 toward the base portion 170.

[0035] In this specification, the cross section of the reduced portion has a rotationally symmetric shape. In this embodiment, the cross section 151 of the reduced portion 150 is a perfect circle. In this specification, the term "perfect circle" refers not only to a strict perfect circle, but also to a shape that deviates slightly from a perfect circle due to unavoidable circumstances such as manufacturing errors. As shown in FIG. 2 , in this embodiment, the center of rotation of the cross section 151 coincides with the central axis Ax of the core shaft 100.

[0036] Let L1 be the sum of the length of the reduced portion 150, which is the distance between the tip and base end of the reduced portion 150, and the length of the intermediate portion 160, which is the distance between the tip and base end of the intermediate portion 160. In the transverse cross section 151 of the reduced portion 150, let L2 be the minimum value of the length of a straight line that passes through the center of rotation and connects two points P1 and P2 on the outer periphery. The center of rotation is the central axis Ax. In this embodiment, the minimum value L2 of the length of a straight line that passes through the center of rotation of the transverse cross section 151 and connects two points P1 and P2 on the outer periphery is the length of the diameter of the transverse cross section 151. The center of rotation is the central axis Ax. L1 and L2 satisfy the following formula (1). L1 and L2 may further satisfy the following formula (2). L1 ≧ L2 × 10 (1) L1 ≧ L2 × 100 (2)

[0037] As shown in Fig. 1 , the coil body 200 is arranged to surround the distal end of the core shaft 100. More specifically, the coil body 200 is arranged to surround the first shaft 110 except for the first base end 112 and the vicinity thereof. The coil body 200 is a multi-thread coil formed by spirally winding a plurality of wires. The total length of the coil body 200 is, for example, 10 mm or more and 500 mm or less, and the outer diameter of the coil body 200 is, for example, 0.2 mm or more and 0.9 mm or less.

[0038] The material of the coil body 200 is, for example, a metal material, more specifically, stainless steel such as SUS302, SUS304, SUS316, superelastic alloy such as Ni-Ti alloy, piano wire, nickel-chromium alloy, cobalt alloy, tungsten, etc.

[0039] As shown in FIG. 1 , the tip joint portion 300 is a member that connects the tip of the core shaft 100 and the tip of the coil body 200. The tip of the core shaft 100 and the tip of the coil body 200 are embedded inside the tip joint portion 300. The tip surface of the tip joint portion 300 is a smooth surface, such as a substantially hemispherical surface. The material of the tip joint portion 300 may be, for example, a metal solder such as silver solder, gold solder, zinc, a Sn—Ag alloy, or a Au—Sn alloy, or an adhesive such as an epoxy adhesive. By disposing the tip joint portion 300 at the tip of the core shaft 100, the tip of the core shaft 100 is prevented from contacting a blood vessel wall or the like, thereby suppressing damage to the core shaft 100.

[0040] The base end joint portion 400 is a member that joins the base end of the coil body 200 to the core shaft 100. The base end joint portion 400 is made of, for example, the same material as the tip joint portion 300 described above.

[0041] The guidewire 10 advances inside a biological lumen while rotating as the operator rotates the gripping portion. When passing through a curved portion of the biological lumen, the guidewire 10 rotates while curving to follow the curved shape of the biological lumen. By rotating the guidewire 10, stress due to torsion is generated in the core shaft 100. The guidewire 10 is required to have high rotation durability, that is, the core shaft 100 is required to be less susceptible to breakage due to stress generated by the rotation of the guidewire 10.

[0042] Because the hardness of the second shaft 120 is higher than the hardness of the first shaft 110, when the core shaft 100 is twisted, stress is likely to increase at the joint between the first shaft 110 and the second shaft 120. In this embodiment, the cross-sectional area of ​​the second shaft 120, which has a relatively high hardness, decreases in stages from the base 170 to the second tip 121. In other words, the rigidity of the second shaft 120 decreases in stages from the base 170 to the second tip 121. This reduces the concentration of stress near the second tip 121, thereby suppressing breakage of the core shaft 100 at the joint between the first shaft 110 and the second shaft 120. In addition, distortion of the curved shape when the core shaft 100 is bent can be suppressed.

[0043] The cross-sectional area of ​​the intermediate portion 160 increases stepwise from the reduced portion 150 toward the base portion 170, with a step between the reduced portion 150 and the constant portion 162. Therefore, when the core shaft 100 is twisted, stress is concentrated to a certain extent in the reduced portion 150. This makes it possible to reliably fracture the core shaft 100 at the reduced portion 150 when a large amount of stress due to torsion accumulates. With this configuration, the magnitude of the stress that causes fracture in the core shaft 100 depends on the material of the core shaft 100 and the size of the reduced portion 150, making it easier to predict. This simplifies the design of the guidewire 10.

[0044] From the viewpoint of improving rotation durability, the value obtained by dividing L1 by L2 (L1 / L2) may be 10 or more and 1000 or less, 30 or more and 500 or less, 100 or more and 300 or less, or 150 or more and 250 or less. When the value of L1 / L2 is within the above range, stress caused by torsion of the core shaft 100 is appropriately dispersed, improving rotation durability.

[0045] In this embodiment, the ratio LA:LB of the length LA of the reduced portion 150 to the length LB of the intermediate portion 160 may be in the range of 1:99 to 99:1, or in terms of excellent rotation durability and bending state, may be in the range of 1:99 to 50:50, may be in the range of 1:99 to 30:70, may be in the range of 2:98 to 20:80, or may be in the range of 2:98 to 0:90.

[0046] In this embodiment, in order to achieve excellent rotational durability and bending state, the volume of the middle portion may be larger than the volume of the contracted portion, and the ratio of the volume of the contracted portion to the volume of the middle portion (volume of contracted portion / volume of middle portion) may be 0.50 or more and 0.01 or less, 0.10 or more and 0.01 or less, or 0.09 or more and 0.02 or less.

[0047] As described above, according to this embodiment, the guidewire 10 includes a core shaft 100. The core shaft 100 includes a first shaft 110 and a second shaft 120. The first shaft 110 has a first distal end 111 and a first proximal end 112 opposite the first distal end 111. The second shaft 120 has a second distal end 121 and a second proximal end 122 opposite the second distal end 121, with the second distal end 121 connected to the first proximal end 112. The second shaft 120 has a higher hardness than the first shaft 110. The second shaft 120 includes a reduced section 150, a base section 170, and an intermediate section 160. The reduced section 150 is disposed near the second distal end 121 and has a cross-sectional area smaller than the area of ​​the proximal end surface 112S of the first shaft 110. The base section 170 includes the second proximal end 122 and has a constant cross-sectional area. The intermediate portion 160 is disposed between the reduced portion 150 and the base portion 170, and has a cross-sectional area that is larger than that of the reduced portion 150 and smaller than that of the base portion 170. The cross-section 151 of the reduced portion 150 has a rotationally symmetric shape. When the sum of the length of the reduced portion 150 and the length of the intermediate portion 160 is L1, and the minimum length of a straight line that passes through the center of rotation and connects two points on the outer periphery in the cross-section 151 of the reduced portion 150 is L2, the following formula (1) is satisfied: L1≧L2×10 (1)

[0048] According to the above configuration, the rotation durability of the guide wire 10 is improved.

[0049] The guidewire 10 may further satisfy the following formula (2): L1≧L2×100 (2)

[0050] With this configuration, the rotation durability of the guidewire 10 is further improved.

[0051] The cross-sectional area of ​​the intermediate portion 160 increases stepwise from the reduced portion 150 toward the base portion 170. This configuration further improves the rotational durability of the guidewire 10. In addition, distortion of the curved shape when the core shaft 100 is bent can be suppressed.

[0052] The intermediate portion 160 includes a first increasing portion 161, a constant portion 162, and a second increasing portion 163, arranged in this order from the second tip 121 side. The cross-sectional area of ​​the first increasing portion 161 increases toward the base portion 170. The cross-sectional area of ​​the constant portion 162 is constant. The cross-sectional area of ​​the second increasing portion 163 increases toward the base portion 170. This configuration improves the rotational durability of the guidewire 10. In addition, the design of the guidewire 10 becomes easier.

[0053] B. Second Embodiment A second embodiment will be described with reference to Fig. 3. A guidewire 10B of this embodiment differs from the first embodiment in the shape of an intermediate portion 160B. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0054] The core shaft 100B included in the guidewire 10B includes a first shaft 110 and a second shaft 120B having a higher hardness than the first shaft 110, similar to the first embodiment.

[0055] The second shaft 120B is a thin wire having a circular cross section, and includes a reduced section 150, an intermediate section 160B, and a base section 170. The intermediate section 160B is disposed between the reduced section 150 and the base section 170 and connects them. The outer diameter of the intermediate section 160B increases continuously from the reduced section 150 toward the base section 170. In other words, the cross-sectional area of ​​the intermediate section 160B increases continuously from the reduced section 150 toward the base section 170.

[0056] As in the first embodiment, when the sum of the length of the contracted portion 150 and the length of the intermediate portion 160B is L1, and the minimum length of a straight line passing through the center of rotation and connecting two points on the outer periphery in the cross section 151 of the contracted portion 150 is L2, L1 and L2 satisfy the following formula (1). L1 and L2 may further satisfy the following formula (2): L1≧L2×10 (1) L1≧L2×100 (2)

[0057] According to the guidewire 10B of this embodiment, similarly to the first embodiment, the rotation durability of the guidewire 10 is improved. In addition, distortion of the curved shape when the core shaft 100 is curved can be suppressed.

[0058] C. Third Embodiment A third embodiment will be described with reference to Fig. 4. A guidewire 10C of this embodiment differs from the first embodiment in the shapes of a reduced section 150C and an intermediate section 160C. In this embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0059] Similar to the first embodiment, the core shaft 100C included in the guidewire 10C includes a first shaft 110 and a second shaft 120C having a higher hardness than the first shaft 110. The second shaft 120C is a thin wire having a circular cross section, and includes a reduced portion 150C, an intermediate portion 160C, and a base portion 170.

[0060] The reduced portion 150C is disposed at the base end of the connecting portion 140 and is the portion of the core shaft 100C that has the smallest cross-sectional area. The reduced portion 150C may have a length of, for example, about 0.01 mm, and may be shaped so that its length is practically invisible.

[0061] Intermediate portion 160C is disposed between and connects reduced portion 150C and base portion 170. The outer diameter of intermediate portion 160C increases continuously from reduced portion 150 toward base portion 170. In other words, the cross-sectional area of ​​intermediate portion 160C increases continuously from reduced portion 150C toward base portion 170.

[0062] As in the first embodiment, when the total length of the reduced portion 150C and the intermediate portion 160C is L1, and the minimum length of a line passing through the center of rotation and connecting two points on the outer periphery of the cross section 151C of the reduced portion 150C is L2, that is, the diameter of the reduced portion 150C, L1 and L2 satisfy the following formula (1). L1 and L2 may further satisfy the following formula (2): L1≧L2×10 (1) L1≧L2×100 (2)

[0063] In the second embodiment, the ratio LA:LB of the length LA of the reduced portion to the length LB of the intermediate portion may be in the range of 1:99 to 99:1, or in terms of excellent rotation durability and bending state, may be in the range of 1:99 to 50:50, may be in the range of 1:99 to 30:70, may be in the range of 2:98 to 20:80, or may be in the range of 2:98 to 10:90.

[0064] In the second embodiment, in order to achieve excellent rotational durability and bending state, the volume of the intermediate portion may be larger than the volume of the contracted portion, and the ratio of the volume of the contracted portion to the volume of the intermediate portion (volume of the contracted portion / volume of the intermediate portion) may be 0.50 or more and 0.01 or less, 0.10 or more and 0.01 or less, or 0.09 or more and 0.02 or less.

[0065] According to the guidewire 10C of this embodiment, similarly to the first embodiment, the rotation durability of the guidewire 10 is improved. In addition, distortion of the curved shape when the core shaft 100 is curved can be suppressed.

[0066] D. Performance Evaluation: 1) Performance Evaluation 1 Ten types of core shaft samples S1-S10 having the same shape as that of the second embodiment were produced, and rotation durability and flexure were evaluated.

[0067] The first shaft was formed using a Ni-Ti alloy base material with an outer diameter of 0.42 mm. The composition, in mass%, was Ni: 56.1%, C: 0.032%, O: 0.025%, and Ti: balance. The second shaft was formed using stainless steel (SUS304) with an outer diameter of 0.42 mm as the base material. The first shaft and the second shaft were joined to produce multiple core shafts. For all core shafts, the length of the first shaft was 100 mm, the length of the second shaft was 1900 mm, and the total length was 2000 mm.

[0068] For these core shafts, the tip of the second shaft was polished to form a connecting section, a reduced section, and an intermediate section. The length of the regular section was 1 mm, the length of the connecting section was 1 mm, the length of the reduced section was 4 mm, and the length of the intermediate section was as shown in Table 1.

[0069]

[0070] A rotation durability test was conducted using samples S1-S10. Each sample was placed inside a U-shaped groove having a semicircular portion with a curvature radius of 15 mm. The joint between the first shaft and the second shaft was positioned at the center of the semicircular portion of the groove, and the distal end of the first shaft and the proximal end of the second shaft were positioned so as to protrude from the groove. Next, the distal end of the first shaft was fixed, and a portion of the proximal end of the second shaft, located 100 mm from the exit of the groove, was rotated around the central axis of the core shaft at a rotational speed of 3000 rpm, and the number of rotations until fracture was measured. Additionally, the fracture location was observed.

[0071] As shown in Table 1 and Figure 5, it was confirmed that, overall, the larger the L1 / L2 value, the greater the number of revolutions until fracture and the higher the rotation durability. In particular, it was confirmed that the number of revolutions until fracture was significantly increased in samples S5-S10, in which the L1 / L2 value was 100 or more, compared to samples S1-S4, in which the L1 / L2 value was less than 100.

[0072] A bending test was conducted using samples S1-S10. Two thick iron plates were prepared and fixed parallel to each other, 30 mm apart. Each sample was curved and placed between the two iron plates. At this time, the joint between the first shaft and the second shaft was positioned at the center of the two iron plates. The state of bending of the sample was visually observed. A sample was evaluated as A when it was roughly symmetrical with respect to a line drawn parallel to the two iron plates at the center position of the two iron plates, and as B when slight distortion was observed but it was not bent in a V shape. As a comparison, a similar test was conducted using a comparative sample in which the second shaft had an outer diameter equal to the outer diameter of the first shaft along its entire length.

[0073] In the comparative sample, a V-shaped bend was observed at the joint between the first shaft and the second shaft. No V-shaped bend was observed in any of samples S1-S10, which had a reduced section and an intermediate section. In samples S1-S4, in which the L1 / L2 value was 10 or greater but less than 100, slight distortion in the curved shape was observed, but this was not enough to interfere with use as a core shaft. Samples S5-S10, in which the L1 / L2 value was 100 or greater, were curved in a generally line-symmetrical manner, and it was observed that the curved shape was generally uniform. Thus, when the curved shape of the core shaft is uniform, the guidewire can be smoothly curved within a biological lumen.

[0074] Next, a core shaft sample S11 having the same shape as that of the first embodiment was produced, and rotation durability was evaluated.

[0075] 2) Performance Evaluation 2 Six types of core shaft samples S11 to S16 having the same shape as that of the first embodiment were produced, and rotation durability and bending properties were evaluated.

[0076] The first shaft was formed using a Ni-Ti alloy base material with an outer diameter of 0.34 mm. The composition, in mass%, was Ni: 56.1%, C: 0.032%, O: 0.025%, and Ti: balance. The second shaft was formed using stainless steel with an outer diameter of 0.34 mm as the base material. The first shaft and the second shaft were joined to produce multiple core shafts. For all core shafts, the length of the first shaft was 100 mm, the length of the second shaft was 1900 mm, and the total length was 2000 mm.

[0077] For these core shafts, the tip end of the second shaft was polished to form a connecting section, a reducing section, and an intermediate section having a first increasing section, a constant section, and a second increasing section. The length of the constant section was 1 mm, the length of the connecting section was 1 mm, the length of the reducing section was 4 mm, the length of the first increasing section was 5 mm, and the length of the second increasing section was 5 mm. The lengths of the constant section and the entire length of the intermediate section were as shown in Table 2.

[0078]

[0079] Using these samples S11-S16, a rotation durability test was conducted in the same manner as in Performance Evaluation 1. As shown in Table 2 and FIG. 6, it was confirmed that, overall, the larger the L1 / L2 value, the greater the number of rotations until fracture, and the higher the rotation durability. In particular, compared to sample S11, which had an L1 / L2 value of less than 100, samples S12-S16, which had an L1 / L2 value of 100 or more, showed a significantly higher number of rotations until fracture. It was also confirmed that all of samples S11-S16 fractured at the contracted portion, not at the joint portion.

[0080] A bending test was conducted using samples S11-S16 in the same manner as in Performance Evaluation 1. No V-shaped bending was observed in any of samples S11-S16. In sample S11, where the L1 / L2 value was 10 or more and less than 100, slight distortion was observed in the curved shape. Samples S12-S16, where the L1 / L2 value was 100 or more, were curved in a generally line-symmetrical manner, and it was observed that there was generally no deviation in the curved shape. Thus, when there is no deviation in the curved shape of the core shaft, the guidewire can be smoothly curved within a biological lumen.

[0081] E. Modifications: 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 and scope of the present invention. For example, the following modifications are also possible. (1) The cross section of the contracting portion may have any rotationally symmetric shape, such as an ellipse, oval, rectangle, rhombus, or regular polygon. Regular polygons include, for example, an equilateral triangle, square, regular pentagon, regular hexagon, regular heptagon, regular octagon, regular nonagon, and regular decagon. (2) The second shaft may not have a fixed portion. The second shaft may not have a connecting portion. The second shaft may not have either a fixed portion or a connecting portion. (3) The intermediate portion may not have an increasing portion connecting the contracting portion and the constant portion, and the constant portion may be adjacent to the contracting portion. Alternatively, the intermediate portion may not have an increasing portion connecting the contracting portion and the base portion, and the constant portion may be adjacent to the base portion. (4) The intermediate portion may have two or more constant portions. In this case, the cross-sectional area of ​​a constant portion closer to the base may be larger than the cross-sectional area of ​​a constant portion further from the base. Two adjacent constant portions may be connected by an increasing portion whose cross-sectional area increases with increasing distance from the base. (5) The base portion may not include the base end of the second shaft, and the second shaft may include a portion between the base and the base end that has a cross-sectional area different from that of the base. For example, the base end side of the base may include a portion that has a smaller outer diameter and cross-sectional area than the base.

Claims

1. A core shaft (100, 100B, 100C) is provided, wherein the core shaft (100, 100B, 100C) comprises: a first shaft (110) having a first tip (111) and a first base end (112) opposite the first tip (111); and a second shaft (120, 120B, 120C) having a second tip (121) connected to the first base end (112) and having a hardness higher than that of the first shaft (110), wherein the second shaft (120, 120B, 120C) comprises: a reduced portion (150, 150C) arranged near the second tip (121) and having a cross-sectional area smaller than the area of ​​the base end surface (112S) of the first shaft (110); a base portion (170) disposed farther from the first base end (112) than the reduced portion (150, 150C) and having a constant cross-sectional area larger than the cross-sectional area of ​​the reduced portion (150, 150C); and an intermediate portion (160, 160B, 160C) disposed between the reduced portion (150, 150C) and the base portion (170) and having a cross-sectional area larger than the cross-sectional area of ​​the reduced portion (150, 150C) and smaller than the cross-sectional area of ​​the base portion (170), wherein the cross-section (151, 151C) of the reduced portion (150, 150C) has a rotationally symmetric shape, A guidewire (10, 10B, 10C) that satisfies the following formula (1), where L1 is the sum of the length of the reduced portion (150, 150C) and the length of the intermediate portion (160, 160B, 160C), and L2 is the minimum value of the length of a straight line that passes through the center of rotation and connects two points (P1, P2) on the outer periphery in a cross section (151, 151C) of the reduced portion (150, 150C): L1≧L2×10 (1) 2. The guidewire (10, 10B, 10C) according to claim 1, which satisfies the following formula (2): L1 ≥ L2 × 100 (2) 3. A guidewire (10) according to claim 1 or claim 2, wherein the cross-sectional area of ​​the intermediate portion (160) increases stepwise from the reduced portion (150) to the base portion (170).

4. A guidewire (10) according to claim 3, wherein the intermediate section (160) comprises, in order from the second tip (121) side, a first increasing section (161), a constant section (162), and a second increasing section (163), the cross-sectional area of ​​the first increasing section (161) increasing as it approaches the base section (170), the cross-sectional area of ​​the constant section (162) being constant, and the cross-sectional area of ​​the second increasing section (163) increasing as it approaches the base section (170).

5. A guidewire (10B, 10C) according to claim 1 or 2, wherein the cross-sectional area of ​​the intermediate portion (160B, 160C) increases continuously from the reduced portion (150, 150C) towards the base portion (170).

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