JP2004065795A - Guide wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a guide wire, the longitudinal stiffness of which gently varies, and which is excellent in operabillity and kink resistant. <P>SOLUTION: The guide wire 1 has a first wire 2 of a linear form arranged on the tip side and a second wire 3 of a linear form arranged on the base side and formed of a material whose elastic modulus is higher than the component material of the first wire 2. The first wire 2 and the second wire 3 are linked by welding. The outside diameter of the first wire 2 and the second wire 3 gradually decreases toward the tips from the position nearer to the base than the welded portion 14 of the first wire 2 and the second wire 3 to the position nearer to the tip than the welded portion 14 crossing the welded portion 14. The first wire 2 is preferably formed of a superelastic alloy and the second wire 3 is preferably formed of a stainless steel. The first wire 2 and the second wire 3 are preferably welded by butt resistance welding. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a guidewire, particularly to a guidewire used for introducing a catheter into a body cavity such as a blood vessel.
[0002]
[Prior art]
The guide wire is used for treatment of a site where surgery is difficult, such as PTCA (Percutaneous Transluminal Coronary Angioplasty), treatment for the purpose of minimally invasive to the human body, and treatment of the heart. It is used to guide catheters used for examinations such as angiography. The guide wire used in the PTCA operation is inserted into the vicinity of a target vascular stenosis together with the balloon catheter with the distal end of the guide wire protruding from the distal end of the balloon catheter. Guide to nearby.
[0003]
The blood vessels are intricately curved, and the guide wire used when inserting the balloon catheter into the blood vessels has a moderate flexibility and resilience to bending, and a pushability to transmit the operation at the proximal end to the distal side. And torque transmission properties (collectively referred to as “operability”), as well as kink resistance (bending resistance) and the like. Among these properties, as a structure for obtaining a moderate flexibility, a structure with a metal coil that has flexibility against bending around a thin tip core material of a guide wire, and for imparting flexibility and resilience There is a guide wire using a superelastic wire such as Ni-Ti as a core material.
[0004]
In a conventional guide wire, a core material is substantially composed of one kind of material. In order to enhance the operability of the guide wire, a material having a relatively high elastic modulus is used. Has lost flexibility. If a material having a relatively low elastic modulus is used to obtain the flexibility of the distal end portion of the guide wire, the operability at the proximal end side of the guide wire is lost. Thus, it has been difficult to satisfy the required flexibility and operability with one kind of core material.
[0005]
In order to improve such a defect, for example, a Ni—Ti alloy wire is used as a core material, and heat treatment is performed on the distal side and the proximal side under different conditions to increase the flexibility of the distal end and increase the flexibility of the proximal side. Guide wires with increased rigidity have been proposed. However, there is a limit to the control of flexibility by such heat treatment, and even if sufficient flexibility is obtained at the distal end, satisfactory rigidity may not always be obtained at the proximal end.
[0006]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a guidewire which has a gradual change in rigidity in the longitudinal direction of the wire and is excellent in operability and kink resistance.
[0007]
[Means for Solving the Problems]
Such an object is achieved by the present invention of the following (1). Further, (2) to (9) are preferable.
[0008]
(1) a linear first wire disposed on the distal end side;
A linear second wire that is disposed on the base end side of the first wire and that is made of a material having a higher elastic modulus than the constituent material of the first wire;
The first wire and the second wire are connected by welding,
The outer diameter of the first wire and the second wire is from a position closer to the distal end than a welded portion of the first wire and the second wire to a position closer to the distal end than the welded portion across the welded portion. A guide wire, which gradually decreases in a distal direction.
[0009]
(2) The guide wire according to (1), wherein the first wire is made of a superelastic alloy.
[0010]
(3) The guide wire according to (1) or (2), wherein the second wire is made of stainless steel.
[0011]
(4) The guide wire according to any one of (1) to (3), wherein a connection end surface between the first wire and the second wire is substantially perpendicular to an axial direction of both wires.
[0012]
(5) The guide wire according to any one of (1) to (4), wherein the outer diameter of the first wire gradually decreases toward the distal end over substantially the entire length.
[0013]
(6) The guide wire according to any one of (1) to (5), further including a spiral coil that covers at least a portion of the first wire on the distal end side.
[0014]
(7) The guide wire according to (6), wherein the welded portion is located closer to a base end than a base end of the coil.
[0015]
(8) The guide wire according to any one of (1) to (7), wherein the welding is performed by butt resistance welding.
[0016]
(9) The guidewire according to any one of (1) to (8), wherein the welded portion is used so as to be located in a living body.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a guidewire of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.
[0018]
FIG. 1 is a longitudinal sectional view showing an embodiment of the guide wire of the present invention, and FIG. 2 is a view showing a procedure for connecting a first wire and a second wire in the guide wire shown in FIG. For convenience of explanation, the right side in FIG. 1 is referred to as a “proximal end” and the left side is referred to as a “distal end”. Also, in FIG. 1, the length direction of the guide wire is shortened to make it easier to see, and the thickness direction of the guide wire is schematically exaggerated, and the ratio of the length direction to the thickness direction is It is very different from the actual situation.
[0019]
A guide wire 1 shown in FIG. 1 is a guide wire for a catheter used by being inserted into a catheter, and includes a first wire 2 disposed on a distal side and a second wire disposed on a proximal side of the first wire 2. It has a wire 3 and a spiral coil 4. The total length of the guidewire 1 is not particularly limited, but is preferably about 200 to 5000 mm. Further, the outer diameter of the guide wire 1 is not particularly limited, but is usually preferably about 0.2 to 1.2 mm.
[0020]
The first wire 2 is a wire having elasticity. The length of the first wire 2 is not particularly limited, but is preferably about 20 to 1000 mm.
[0021]
In the present embodiment, the outer diameter of the first wire 2 gradually decreases toward the distal end over substantially the entire length. Thereby, the rigidity (bending rigidity, torsional rigidity) of the first wire 2 can be gradually reduced in the distal direction, and as a result, the guide wire 1 obtains good flexibility at the distal end, and the The followability and safety are improved, and bending and the like can be prevented.
[0022]
In the illustrated configuration, the first wire 2 has a tapered shape in which the outer diameter continuously decreases gradually toward the distal end over substantially the entire length. The taper angle of the tapered portion of the first wire 2 may be constant along the longitudinal direction or may change along the longitudinal direction.
[0023]
Also, unlike the illustration, the first wire 2 may have a portion in which the outer diameter is constant along the longitudinal direction. For example, the first wire 2 is formed with a plurality of tapered portions in which the outer diameter gradually decreases in the distal direction along the longitudinal direction, and the outer diameter between the tapered portions is long. It may be such that a certain portion is formed along the direction. Even in such a case, the same effect as described above can be obtained. Further, unlike the illustration, the first wire 2 may have a constant outer diameter in the longitudinal direction at the tip side.
[0024]
The constituent material of the first wire 2 is not particularly limited. For example, various metal materials such as stainless steel can be used, but it is preferable to use an alloy (including a superelastic alloy) exhibiting pseudoelasticity. More preferably, it is an elastic alloy. The superelastic alloy is relatively flexible and resilient and hardly bends. Therefore, by forming the first wire 2 from a superelastic alloy, the guide wire 1 can have a sufficient amount at the distal end portion. Flexibility and resilience to bending are obtained, followability to a complicatedly curved or bent blood vessel is improved, and more excellent operability is obtained, and even if the first wire 2 repeats bending and bending deformation, Since the first wire 2 does not have a bending habit due to the restoring property, it is possible to prevent a decrease in operability due to the first wire 2 having a bending habit during use of the guide wire 1.
[0025]
Pseudoelastic alloys include those having a stress-strain curve due to tension in any shape, those in which transformation points such as As, Af, Ms, and Mf can be remarkably measured and those in which they cannot be measured. (Strain) and almost all return to the original shape by removing the stress are included.
[0026]
Preferred compositions of the superelastic alloy include a Ni-Ti alloy such as a 49-52 atomic% Ni-Ni alloy, a 38.5-41.5 wt% Zn Cu-Zn alloy, and a 1-10 wt% X (X is at least one of Be, Si, Sn, Al, and Ga), and a 36-38 atomic% Al-Ni-Al alloy. Of these, particularly preferred are the above-mentioned Ni-Ti alloys.
[0027]
The distal end of the second wire 3 is connected (connected) to the proximal end of the first wire 2. The second wire 3 is a wire having elasticity. The length of the second wire 3 is not particularly limited, but is preferably about 20 to 4800 mm.
[0028]
The second wire 3 is made of a material having a higher elastic modulus (Young's modulus (longitudinal modulus), rigidity (transverse modulus), bulk modulus) than the constituent material of the first wire 2. Thereby, moderate rigidity (bending rigidity, torsional rigidity) is obtained for the second wire 3, and the guide wire 1 becomes so-called stiff, so that pushability and torque transmission are improved, and more excellent insertion operability. Is obtained.
[0029]
The constituent material (material) of the second wire 3 is not particularly limited, and stainless steel (for example, SUS304, SUS303, SUS316, SUS316L, SUS316J1, SUS316J1L, SUS405, SUS430, SUS434, SUS444, SUS429, SUS430F, SUS302, etc.) Various metal materials such as all types, piano wires, cobalt-based alloys and pseudoelastic alloys can be used, but stainless steel is preferred. When the second wire 3 is made of stainless steel, the guide wire 1 can have better pushability and torque transmission.
[0030]
Further, in the present invention, it is preferable that the first wire 2 and the second wire 3 are formed of different alloys, and that the first wire 2 is formed of a superelastic alloy and the second wire 3 is formed of stainless steel. It is particularly preferred to do so. Thus, the guide wire 1 has excellent flexibility at the distal end portion and has high rigidity (bending rigidity and torsional rigidity) at the proximal end portion. As a result, the guidewire 1 obtains excellent pushability and torque transmission and secures good operability, and at the distal end side, obtains good flexibility and resilience to follow the blood vessel and ensure safety. Is improved.
[0031]
It is preferable to use a Ni-Ti alloy as the superelastic alloy constituting the first wire 2 from the viewpoint of flexibility and restorability on the tip side.
[0032]
The coil 4 is a member formed by spirally winding a wire (thin wire), and is installed so as to cover a portion of the first wire 2 on the distal end side. In the illustrated configuration, a portion on the tip end side of the first wire 2 is inserted into a substantially central portion inside the coil 4. Further, a portion on the tip end side of the first wire 2 is inserted in non-contact with the inner surface of the coil 4. In the illustrated configuration, the coil 4 has a slight gap between the spirally wound wires in a state where no external force is applied. However, unlike the illustrated example, the coil 4 is spirally wound in a state where no external force is applied. Wires wound in a shape may be densely arranged without gaps.
[0033]
The coil 4 is preferably made of a metal material. Examples of the metal material forming the coil 4 include stainless steel, superelastic alloys, cobalt-based alloys, noble metals such as gold, platinum, and tungsten, and alloys containing these. In particular, when the guide wire 1 is made of an X-ray opaque material such as a noble metal, X-ray opacity is obtained for the guide wire 1, and the guide wire 1 can be inserted into a living body while confirming the position of the distal end portion under X-ray fluoroscopy. Yes, it is preferable. Further, the coil 4 may be configured such that the distal end side and the proximal end side are made of different materials. For example, the distal end may be constituted by a coil made of an X-ray opaque material, and the proximal end may be constituted by a coil made of a material that relatively transmits X-rays (such as stainless steel). In addition, the total length of the coil 4 is not particularly limited, but is preferably about 5 to 500 mm.
[0034]
The proximal end and the distal end of the coil 4 are fixed to the first wire 2 by fixing materials 11 and 12, respectively. Further, an intermediate portion (position near the tip) of the coil 4 is fixed to the first wire 2 by a fixing material 13. The fixing materials 11, 12, and 13 are made of solder (brazing material). The fixing materials 11, 12 and 13 are not limited to solder, but may be adhesives. Further, the method of fixing the coil 4 is not limited to the method using the fixing material, and may be, for example, welding. In addition, in order to prevent damage to the inner wall of the blood vessel, the distal end surface of the fixing material 12 is preferably rounded.
[0035]
In the present embodiment, since such a coil 4 is provided, the first wire 2 is covered by the coil 4 and has a small contact area, so that the sliding resistance can be reduced, and thus the guide wire can be reduced. 1 further improves operability.
[0036]
In the present embodiment, the coil 4 has a wire having a circular cross section. However, the present invention is not limited to this. For example, the wire has a cross section of an ellipse, a square (especially a rectangle), or the like. Is also good.
[0037]
The guidewire 1 as described above may have a coating (plastic jacket) (not shown) of a synthetic resin that covers all or a part of the outer peripheral surface (outer surface). Thereby, the friction with the inner wall of the catheter used together with the guide wire 1 is reduced, the slidability is improved, and the operability of the guide wire 1 in the catheter is further improved. As the constituent material of such a coating, for example, polyethylene, polyvinyl chloride, polyester, polypropylene, polyamide, polyurethane, polystyrene, polycarbonate, fluororesin (PTFE, ETFE, etc.), silicone resin, other various elastomers, or these Are preferably used. In particular, a wire having flexibility and flexibility equal to or less than that of the first wire 2 is preferable. Further, the place where such a coating is provided is not particularly limited. For example, it may be provided on almost the entirety of the guide wire 1, and may be provided only on the distal end portion (outer peripheral surfaces of the first wire 2 and the coil 4). It may be provided.
[0038]
Further, the entire or a part of the outer peripheral surface of the guidewire 1 may be subjected to a process for suppressing friction generated by contact with an inner wall of a catheter used together with the guidewire 1. Thereby, friction with the inner wall of the catheter is suppressed, and the operability of the guidewire 1 in the catheter is further improved. As this treatment, for example, a coating (not shown) made of a hydrophilic material or a hydrophobic material can be provided on the outer peripheral surface of the guide wire 1.
[0039]
Examples of the hydrophilic material constituting the film include a cellulose-based polymer, a polyethylene oxide-based polymer, and a maleic anhydride-based polymer (for example, maleic anhydride such as methyl vinyl ether-maleic anhydride copolymer). Acid copolymer), acrylamide-based polymer substances (for example, polyacrylamide, block copolymer of polyglycidyl methacrylate-dimethylacrylamide (PGMA-DMAA)), water-soluble nylon, polyvinyl alcohol, polyvinylpyrrolidone, and the like. Examples of the hydrophobic material forming the coating include a fluorine-based resin such as polytetrafluoroethylene, a silicone-based material, and the like.
[0040]
In the guide wire 1, the first wire 2 and the second wire 3 are connected (fixed) to each other by welding. As a result, the welding portion (connection portion) 14 between the first wire 2 and the second wire 3 has a high bonding strength (joining strength), and therefore, the guide wire 1 has a torsion torque from the second wire 3 The pushing force is reliably transmitted to the first wire 2.
[0041]
In the present embodiment, the connection end face 21 of the first wire 2 to the second wire 3 and the connection end face 31 of the second wire 3 to the first wire 2 are each substantially perpendicular to the axial direction (longitudinal direction) of both wires. Although the plane is flat, the processing for forming the connection end faces 21 and 31 is extremely easy, and the above-described effect can be achieved without complicating the manufacturing process of the guide wire 1.
[0042]
Note that, unlike the configuration shown in the figure, the connection end surfaces 21 and 31 may be inclined with respect to a plane perpendicular to the axial direction (longitudinal direction) of both wires, or may be concave or convex.
[0043]
The method for welding the first wire 2 and the second wire 3 is not particularly limited, and includes, for example, butt resistance welding such as spot welding using a laser and butt seam welding, but butt resistance welding. Is preferred. Thereby, the welding part 14 can obtain higher bonding strength.
[0044]
In such a guide wire 1, the outer diameters of the second wire 3 and the first wire 2 are welded across the welded portion 14 from a position closer to the base end than the welded portion 14 (the base end 151 of the outer diameter gradually decreasing portion 15). It gradually decreases toward the distal end from the portion 14 to a position on the distal end side (the distal end 152 of the outer diameter gradually decreasing portion 15). In other words, the second wire 3 and the first wire 2 are positioned so as to straddle the welded portion 14, and the outer diameter gradually decreasing portion 15 in which the outer diameter of the second wire 3 and the first wire 2 gradually decreases toward the distal end. The welded portion 14 is located between a base end 151 of the outer diameter gradually decreasing portion 15 and a distal end 152 of the outer diameter gradually decreasing portion 15. Thereby, the stiffness (bending stiffness, torsional stiffness) of the site including the welded portion 14 gradually decreases toward the distal end. Therefore, the guide wire 1 extends along the longitudinal direction even in the vicinity thereof including the welded portion 14 where the first wire 2 and the second wire 3 made of materials having different elastic moduli are connected (joined). Therefore, the rigidity changes slowly (smoothly). As a result, the kink resistance (bending resistance) in the vicinity of the welded portion 14 is improved, and the guidewire 1 has excellent operability.
[0045]
In the illustrated configuration, the distal end 152 of the outer diameter gradually decreasing portion 15 is at the position of the distal end of the first wire 2. However, the present invention is not limited to such a configuration, and the distal end 152 of the outer diameter gradually decreasing portion 15 The position may be a middle position in the longitudinal direction. That is, the outer diameter of the portion on the distal end side of the first wire 2 does not have to be gradually reduced toward the distal end.
[0046]
From the welding unit 14, the length of the to the proximal end 151 of the outer diameter gradually reducing unit 15 (the length indicated by _{L 1} in FIG. 1) is not particularly limited and is preferably about 5～900Mm, 10 to 250 mm More preferably, it is about Further, the welded portion 14, the length to the tip 152 of the outer diameter gradually reducing unit 15 (the length indicated by _{L 2} in FIG. 1) is not particularly limited and is preferably about 5～800Mm,. 10 to More preferably, it is about 250 mm. When L ₁ and L ₂ are in the above-described range, the change in the rigidity along the longitudinal direction can be made more gradual (smooth) in the vicinity thereof including the welded portion 14.
[0047]
In the present embodiment, the outer diameter gradually decreasing portion 15 has a tapered shape in which the outer diameter continuously decreases at a substantially constant decreasing rate toward the distal end. In other words, the taper angle of the outer diameter gradually decreasing portion 15 is substantially constant along the longitudinal direction. Thereby, in the guidewire 1 of the present embodiment, the change in the rigidity along the longitudinal direction can be made more gradual (smooth) in the vicinity thereof including the welded portion 14. Note that, unlike such a configuration, the outer diameter decreasing rate (the taper angle of the outer diameter gradually decreasing portion 15) in the distal direction of the outer diameter gradually decreasing portion 15 may change along the longitudinal direction. For example, a portion where the reduction rate of the outer diameter is relatively large and a portion where the outer diameter is relatively small may be alternately and repeatedly formed a plurality of times. In this case, there may be a portion where the outer diameter decreasing rate toward the distal end of the outer diameter gradually decreasing portion 15 becomes zero.
[0048]
Further, in the present embodiment, the welding portion 14 is located closer to the proximal end than the proximal end of the coil 4, but unlike the drawing, the welding portion 14 is located closer to the distal end than the proximal end of the coil 4. May be.
[0049]
Hereinafter, a procedure for joining the first wire 2 and the second wire 3 by butt seam welding, which is an example of butt resistance welding, will be described with reference to FIG. FIG. 3 shows procedures (1) to (4) when the first wire 2 and the second wire 3 are joined by butt seam welding.
[0050]
In procedure (1), the first wire 2 and the second wire 3 fixed (attached) to a butt welding machine (not shown) are shown.
[0051]
In procedure (2), the first wire 2 and the second wire 3 are connected to each other by applying a predetermined voltage by a butt welding machine to the connection end face 21 on the base end side of the first wire 2 and the distal end of the second wire 3. Is brought into pressure contact with the connection end face 31 on the side. Due to this pressure contact, a molten layer is formed at the contact portion, and the first wire 2 and the second wire 3 are firmly connected.
[0052]
In step (3), the protruding portion of the connection portion (welded portion 14) deformed by pressure contact is deleted.
[0053]
Next, in step (4), the portion including the connection portion (welded portion 14) is polished to form an outer diameter gradually decreasing portion 15 whose outer diameter gradually decreases toward the distal end. The procedure (3) may be omitted and the procedure (4) may be performed.
[0054]
FIG. 3 and FIG. 4 are views showing a use state when the guide wire 1 of the present invention is used for PTCA operation.
[0055]
3 and 4, reference numeral 40 denotes an aortic arch, reference numeral 50 denotes a right coronary artery of the heart, reference numeral 60 denotes a right coronary artery opening, and reference numeral 70 denotes a vascular stenosis. Reference numeral 30 denotes a guiding catheter for reliably guiding the guide wire 1 from the femoral artery to the right coronary artery, and reference numeral 20 denotes a balloon catheter for expanding a stenosis having a balloon 201 which can be expanded and contracted at the distal end. .
[0056]
As shown in FIG. 3, the distal end of the guidewire 1 is projected from the distal end of the guiding catheter 30 and inserted into the right coronary artery 50 from the right coronary artery opening 60. Further, the guide wire 1 is advanced, inserted into the right coronary artery from the distal end, and stopped at a position where the distal end exceeds the vascular stenosis 70. Thereby, the passage of the balloon catheter 20 is secured. At this time, the welded portion 14 of the guidewire 1 is located near the base of the aortic arch 40 (in a living body).
[0057]
Next, as shown in FIG. 4, the distal end of the balloon catheter 20 inserted from the proximal end side of the guide wire 1 is made to protrude from the distal end of the guiding catheter 30 and further advanced along the guide wire 1 to open the right coronary artery opening. It is inserted into the right coronary artery 50 from the portion 60 and stops when the balloon reaches the position of the vascular stenosis 70.
[0058]
Next, a balloon dilatation fluid is injected from the proximal end side of the balloon catheter 20 to dilate the balloon 201 and dilate the vascular stenosis part 70. By doing so, the deposits such as cholesterol adhering and depositing in the blood vessels of the blood vessel stenosis part 70 are physically spread out, and the obstruction of blood flow can be eliminated.
[0059]
As described above, the guide wire of the present invention has been described with respect to the illustrated embodiment, but the present invention is not limited to this, and each part constituting the guide wire has an arbitrary configuration capable of exhibiting the same function. Can be replaced by Further, an arbitrary component may be added.
[0060]
【The invention's effect】
As described above, according to the present invention, the first wire disposed on the distal end side and the second wire disposed on the proximal end side of the first wire and made of a material having a higher elastic modulus than the first wire With this arrangement, a guide wire having a flexible distal end portion and a rigid base end portion and having excellent pushability, torque transmission, and followability can be configured.
[0061]
In addition, since the first wire and the second wire are connected by welding, the connection strength of the connection portion (welded portion) is high, and the torsional torque and the pushing force can be reliably transmitted from the second wire to the first wire. it can.
[0062]
In addition, since the outer diameter of the first wire and the second wire gradually decreases in the distal direction from the position on the base end side of the welded portion to the position on the distal end side from the welded portion across the welded portion, the welding is performed. The stiffness change along the longitudinal direction of the portion including the portion in the longitudinal direction is gentle, and it is possible to reliably prevent the kink (bending) near the welded portion.
[0063]
Thus, according to the present invention, a guidewire excellent in operability and kink resistance can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a guide wire of the present invention.
FIG. 2 is a view showing a procedure for connecting a first wire and a second wire in the guide wire shown in FIG. 1;
FIG. 3 is a schematic diagram for explaining an example of use of the guide wire of the present invention.
FIG. 4 is a schematic view for explaining an example of using the guide wire of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 guide wire 2 first wire 21 connection end face 3 second wire 31 connection end face 4 coils 11, 12, 13 fixing material 14 welded portion 15 outer diameter gradually decreasing portion 151 base end of outer diameter gradually decreasing portion 152 distal end 20 of outer diameter gradually decreasing portion Balloon catheter 201 balloon 30 guiding catheter 40 aortic arch 50 right coronary artery 60 right coronary artery opening 70 vascular stenosis

Claims (1)

A first linear wire disposed on the distal end side;
A linear second wire that is disposed on the base end side of the first wire and that is made of a material having a higher elastic modulus than the constituent material of the first wire;
The first wire and the second wire are connected by welding,
The outer diameter of the first wire and the second wire is from a position closer to the distal end than a welded portion of the first wire and the second wire to a position closer to the distal end than the welded portion across the welded portion. A guide wire, which gradually decreases in a distal direction.

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