JP2013116252A - Medical guide wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a guide wire having even more excellent torque transmission performance than a conventionally known guide wire provided with a core wire made of stainless steel, and having excellent shape retention performance in which the guide wire is less susceptible to permanent deformation even when bent within a blood vessel.SOLUTION: A guide wire is provided with: a core wire (4) having a proximal-end large-diameter section (20) and distal-end small-diameter sections (22, 24, 26); and a coil spring (12) mounted along the axial direction onto the outer periphery of the distal-end small-diameter sections (22, 24, 26) of the core wire (4). The core wire (4) comprises a wire material for which the amount of processing-induced martensite is 20-60 vol% obtained by subjecting a wire material of austenitic stainless steel to wire-drawing and straightening processing, and the warp angle of a leading-end portion imparted by winding is less than 5° when a tensile load of 150 gf is applied for ten seconds in a state where the distal-end small-diameter sections of the core wire (4) onto which the coil spring (12) has been mounted have been wound once along the outer periphery of a rod 20 mm in diameter.

Description

  The present invention relates to a medical guide wire, and more particularly to a medical guide wire that is excellent in torque transmission and hardly causes permanent deformation even when bent.

  As a guide wire for guiding a medical device such as a catheter to a predetermined position in a body cavity such as a blood vessel, the outer diameter of the distal end portion of the core wire is made smaller than the outer diameter of the proximal end portion. A medical guide wire is known in which a coil spring is attached to the outer periphery of the distal end portion to improve the flexibility of the distal end portion (see, for example, Patent Document 1).

  The medical guide wire as described above has good torque transmission (the rotation torque on the proximal end side is well transmitted to the distal end side), and has high bending rigidity (waist) It is required that the material is not easily deformed even when bent, and has excellent shape retention (bending resistance).

  Austenitic stainless steel (SUS316, SUS304) is used as a core wire from the viewpoint of obtaining a guide wire with good torque transmission and high bending rigidity (see, for example, Patent Document 2).

JP 2003-299739 A JP 2010-214054

However, the conventionally known guide wire provided with a core wire made of austenitic stainless steel is not sufficient in torque transmission, and further improvement is desired.
In addition, when a conventionally known guide wire having a core wire made of stainless steel is inserted into a blood vessel having a strong bend, the distal end portion of the guide wire is permanently deformed (plastic deformation), which hinders subsequent operations. Sometimes.

The present invention has been made based on the above situation.
An object of the present invention is a shape that has excellent torque transmission compared to a conventionally known guide wire provided with a core wire made of stainless steel, and is less likely to cause permanent deformation at the tip even when bent in a blood vessel. The object is to provide a guide wire excellent in retention.

The medical guide wire according to the present invention includes a core wire having a proximal end side large diameter portion and a distal end side small diameter portion having a smaller outer diameter than the proximal end large diameter portion, and a distal end small diameter of the core wire. A coil spring mounted along the axial direction on the outer periphery of the portion,
The core wire is composed of a wire material having a work-induced martensite amount of 20 to 60% by volume obtained by subjecting a wire rod of austenitic stainless steel to wire drawing and straightening.
When a 150 gf tensile load is applied for 10 seconds in a state where the distal end side small diameter portion of the core wire to which the coil spring is attached is wound once along the outer periphery of a rod having a diameter of 20 mm, a tip portion by winding The warpage angle is less than 5 °.

In a medical guide wire having such a configuration, a processing-induced martensite structure is precipitated in each crystal grain by wire drawing and straight processing (particularly straight processing).
Then, by processing the austenitic stainless steel subjected to processing (straightness index Md30), processing conditions (for example, tensile speed, torsion angle, processing temperature), etc. as appropriate, processing is performed by straight processing. The amount of induced martensite can be controlled.

  Here, the use of an austenitic stainless steel wire having a work-induced martensite amount of 20 to 60% by volume as the core wire can improve the torque transmission of the guide wire and has excellent shape stability ( A warp angle of less than 5 °).

In the medical guidewire according to the present invention, it is preferable that the amount of processing-induced martensite of the wire constituting the core wire is 30 to 40% by volume.
The austenitic stainless steel is preferably SUS304 or SUS316.

  The medical guide wire of the present invention has excellent torque transmission compared to a conventionally known guide wire provided with a core wire made of stainless steel, has excellent shape stability, and has a distal end even when bent in a blood vessel. Permanent deformation hardly occurs in the part.

It is explanatory drawing which fractured | ruptured a part of medical guidewire which concerns on one Embodiment of this invention. It is a perspective view which shows typically the arrangement | sequence state of a crystal grain in the core wire which comprises the guide wire shown in FIG. It is explanatory drawing which shows the simulation apparatus for testing the torque transmission property of a guide wire. It is a graph which shows the torque transmissibility of the guide wire obtained by the Example and the comparative example.

Hereinafter, an embodiment of the present invention will be described.
The medical guide wire 2 of the present embodiment shown in FIG. 1 includes a core wire 4 having a proximal end side large diameter portion 20, distal end side small diameter portions 22, 24, 26, and tapered portions 21, 23, 25; And a coil spring 12 mounted along the axial direction on the outer circumference of the small-diameter portion on the distal end side of the core wire 4. The core wire 4 is obtained by drawing and straightening austenitic stainless steel wire. A state in which the small diameter portion of the core wire 4 on which the coil spring 12 is mounted is wound once along the outer periphery of a rod having a diameter of 20 mm, which is made of a wire material having a processing induced martensite amount of 20 to 60% by volume. When a tensile load of 150 gf is applied for 10 seconds, the warp angle of the tip portion due to winding is less than 5 °.

  The guide wire 2 of this embodiment includes a core wire 4 and a coil spring 12. The core wire 4 is formed continuously along the axial direction with respect to the proximal-end-side large-diameter portion 20 and the proximal-end-side large-diameter portion 20, and has an outer diameter larger than that of the proximal-end-side large-diameter portion 20. It is comprised by the distal end side small diameter part 22, 24, 26 which becomes small in steps. Tapered portions 21, 23, 25 are formed at the joint between the proximal end side large diameter portion 20 and the distal end side small diameter portion 22, and at the joint portions of the distal end side small diameter portions 22, 24, 26, respectively. The outer diameter of the core wire 4 is gradually reduced toward the distal end side along the axial direction. The coil spring 12 is mounted on the outer periphery of these distal end side small diameter portions 22, 24, 26.

The core wire 4 is integrally formed of a wire having a substantially circular cross section.
The core wire 4 is obtained by subjecting an austenitic stainless steel wire to wire drawing and straightening.
Here, as an example of the composition of the austenitic stainless steel, C is 0.08% or less, Si is 1.00% or less, Mn is 2.00% or less, Cr is 18.00 to 20.00%, Ni Is 8.00 to 10.50%, and the balance is Fe and inevitable impurities.
Suitable austenitic stainless steels include SUS304 and SUS316.

  The wire drawing performed on the wire rod of austenitic stainless steel is not particularly limited as long as the wire diameter of the steel material can be continuously reduced. May be. Moreover, it may be a wet drawing process or a dry drawing process. The drawn wire is wound around a bobbin and collected.

  Straightening is a process of straightening a wire rod that has been drawn and wound around a bobbin by pulling it while twisting it.

  By straight processing (twisting), the crystal grains of the austenitic stainless steel constituting the wire are oriented obliquely as shown in FIG. 2 (in the same figure, the range indicated by symbol C is one crystal grain). Further, a work-induced martensite structure (not shown) is precipitated in each crystal grain of the straight wire.

The wire rod that has been drawn and straightened is cut, and the end portion of this wire rod is tapered so that the outer diameter gradually decreases toward the tip, and the distal end side small-diameter portions 22, 24, and 26 are formed. By forming the core wire 4, the core wire 4 is obtained.
The residual stress remaining in the wire may be removed by performing an aging treatment.

  In the wire constituting the core wire 4, the amount of martensite precipitated in the crystal grains (processing-induced martensite amount) is usually 20 to 60% by volume, preferably 30 to 40% by volume.

  An austenitic stainless steel wire having an amount of work-induced martensite of 20 to 60% by volume has suitable toughness and ductility. By using such a wire as a core wire, the torque transmission performance of the guide wire is improved and excellent shape stability (bending wrinkle resistance) is exhibited, as is apparent from the results of Examples described later. Is done.

  A wire rod whose processing induced martensite amount is less than 20% by volume does not have sufficient toughness and torsional rigidity, and a guide wire using this as a core wire can sufficiently improve torque transmission. First, the rotational movement on the distal end side with respect to the rotation operation on the proximal end side is delayed (see evaluation of torque transmission in Comparative Example 1 described later).

  In addition, a guide wire that uses a wire having a work-induced martensite amount of less than 20% by volume as a core wire is prone to bending wrinkles and is inferior in shape retention (see evaluation of shape retention in Comparative Example 1). When a simple guide wire is inserted into a blood vessel with a strong bend, permanent deformation (plastic deformation) tends to occur at the distal end.

  On the other hand, a wire rod whose work-induced martensite amount exceeds 60% by volume is inferior in ductility due to excessive toughness and rigidity. When a guide wire using such a wire rod as a core wire is rotated on the proximal end side, The rotation angle on the distal end side with respect to the rotation angle tends to be extremely small at the beginning of the operation and then suddenly increases (as if repelling), and such a guide wire is extremely inferior in operability (described later). (Refer to the evaluation of torque transmission in Comparative Example 2).

  In addition, a guide wire that uses a wire rod whose amount of work-induced martensite exceeds 60% by volume as a core wire has high bending rigidity, but it easily breaks and cracks when bending force is applied, and has extremely poor shape retention. (Refer to the evaluation of shape retention in Comparative Example 2).

  Further, since the wire rod having a work-induced martensite amount exceeding 60% by volume is hard and brittle, when a guide wire used as a core wire is inserted into a blood vessel having a strong bend, the inner wall of the blood vessel may be damaged. The guide wire (core wire) itself may break.

  A guide that has excellent torque transmission and excellent shape stability that hardly causes permanent deformation only when the amount of work-induced martensite in the wire (austenitic stainless steel) used as the core wire is 20 to 60% by volume. A wire can be obtained.

The total length of the core wire 4 varies depending on the purpose of use and is not particularly limited, but is, for example, 1000 to 3000 mm, and preferably 1800 to 2000 mm.

The outer diameter of the proximal end side large diameter portion 20 in the core wire 4 is usually about 0.10 to 0.90 mm.
The outer diameter of the distal end side small diameter portions 22, 24, and 26 is not particularly limited, but is preferably about 1/5 to 1/2 of the outer diameter of the proximal end side large diameter portion 20. is there.

A spherical or hemispherical ball portion 10 is joined to the tip of the distal end side small diameter portion 26 in the core wire 4. The ball portion 10 is a portion for smoothening the distal end portion of the guide wire 2 and preventing damage to the inner wall of the body cavity as much as possible when the guide wire 2 is inserted into a body cavity such as a blood vessel. It becomes the upper end side stopper.
The ball portion 10 is made of a metal such as silver, gold, or an alloy thereof, and is joined to the tip of the distal end side small diameter portion 26 by means such as welding or brazing. The outer diameter of the ball portion 10 is preferably about 0.5 to 2 times the outer diameter of the proximal end side large diameter portion 20 of the core wire 4.

  The distal end 14 of the coil spring 12 is joined to the back surface of the ball portion 10 by means such as welding or brazing. The proximal end 16 of the coil spring 12 may be joined to the outer periphery of the core wire 4 by means such as welding or brazing at a tapered portion 21 in the vicinity of the proximal end of the distal end side small diameter portion 22.

The outer peripheral surface of the core wire 4 that is not covered with the coil spring (proximal end side large diameter portion 20) may be covered with a biocompatible coating film.
Although it does not specifically limit as a biocompatible coating film, For example, normal polymers used for medical uses, such as olefins, such as polyethylene, nitrogen-containing polymers, such as a polyimide and polyamide, a siloxane polymer, and a fluororesin polymer (for example, PTFE) Can be mentioned. The coating film is not limited to a polymer, and may be an inorganic coating film such as silicon carbide, carbon such as pyrolite carbon and diamond-like carbon.

  The outer diameter of the coil spring 12 is not particularly limited, but is preferably equal to or less than the outer diameter of the ball portion 10. Although the outer diameter of the wire which comprises the coil spring 12 is not specifically limited, Preferably it is 20-150 micrometers, More preferably, it is the range of 50-100 micrometers.

  The material of the coil spring 12 is not particularly limited, and may be a radiation contrast material or a non-radiation contrast material. Examples of the radiation contrast material include materials having good contrast properties for X-rays such as platinum, platinum alloys (for example, Pt / Ir = 93/7), gold, gold-copper alloy, tungsten, and tantalum. Further, the radiation non-contrast material is not particularly limited, but stainless steel (for example, SUS316, SUS304) and the like are mainly exemplified. The coil spring 12 may be subjected to a hydrophilic lubrication coating treatment.

  The material of the coil spring 12 is not necessarily the same in the axial direction. For example, the distal end side may be a platinum coil and the proximal end side may be a stainless steel coil.

  In the guide wire 2 of the present embodiment, the distal end side small diameter portions 22, 24, 26 of the core wire 4 to which the coil spring 12 is attached are tensioned by 150 gf in a state where the distal end side small diameter portions 22, 24, 26 are wound once along the outer periphery of a 20 mm diameter rod. When the load is applied for 10 seconds, the warp angle (bending wrinkle) of the tip portion by winding is less than 5 °, and the shape retention (bending wrinkle resistance) is extremely excellent. Therefore, even if the guide wire 2 is inserted into a blood vessel (for example, coronary artery system) having a strong bend, the distal end portion hardly undergoes permanent deformation (plastic deformation). As a result, the guide wire 2 can be easily followed and inserted into a blood vessel having a strong bent portion near the tip.

<Example 1>
The SUS403 wire was drawn and straightened to obtain a wire having a diameter of 0.34 mm in which the amount of work-induced martensite was in the range of 30 to 40% by volume. Next, the end portion of this wire is tapered so that the outer diameter gradually decreases toward the tip, and the distal end side small diameter portions 22 (outer diameter 0.16 mm), 24 (outer diameter 0.10 mm), 26 (outer diameter 0.06 mm) was formed.
The total length of the core wire 4 is about 1800 mm, the proximal end side large diameter portion 20 has an outer diameter of 0.34 mm, the distal end side small diameter portion 22 has a length of 100 mm, 24 has a length of 30 mm, and 26 has a length of 26. 40 mm.
A coil spring 12 was attached to the obtained core wire 4 to produce three guide wires of the present invention having a structure as shown in FIG.

<Comparative Example 1>
In the same manner as in Example 1, except that the wire rod of SUS403 was drawn and straightened to obtain a wire rod having a diameter of 0.34 mm in which the amount of work-induced martensite was in the range of 10 to 15% by volume. Three guide wires for comparison having a structure as shown in FIG.

<Comparative example 2>
In the same manner as in Example 1, except that a wire made of SUS403 was drawn and straightened to obtain a wire having a diameter of 0.34 mm in which the amount of work-induced martensite was in the range of 65 to 80% by volume. Three guide wires for comparison having a structure as shown in FIG.

(1) Evaluation of torque transmission property Each of the guide wires obtained in Example 1 and Comparative Examples 1 and 2 is inserted into a jig simulating a human coronary artery shown in FIG. The distal end (hand side) was twisted and rotated at a predetermined hand side angle of 0 to 360 ° by a motor, and the tip rotation angle (twist angle) at the distal end (tip) of the guide wire was measured. The results are shown in FIG. In FIG. 4, the curve for one of the three guide wires obtained in each example is shown, but the same result was obtained for the other two obtained in the same example.
The closer to the theoretical straight line shown in FIG. 4, the better the torque transmission and the better the operability. If the torque transmission is good, the rotational force on the hand side is easily transmitted to the tip, and it becomes easy to advance to the target blood vessel by selecting the blood vessel branch, and the insertion workability is improved.
From the results shown in FIG. 4, it can be said that the guide wire obtained in Example 1 has a small delay in the rotational operation on the distal end side with respect to the rotation operation on the proximal end side, and has good torque transmission. On the other hand, the guide wire obtained in Comparative Example 1 has a large delay in the rotational operation on the distal end side and is inferior in torque transmission. In addition, the guide wire obtained in Comparative Example 2 has a sharply increased rotational angle on the distal end side and is extremely inferior in torque transmission.

(2) Evaluation of Shape Retention Property For each of the guide wires obtained in Example 1 and Comparative Example 1, the warp angle of the tip portion due to winding was measured by the method described above. The results are shown in Table 1 below.

  * When wound around the rod, it was broken and cracked, and the shape did not return to its original shape.

2 Medical Guide Wire 4 Core Wire 10 Ball Part 12 Coil Spring 20 Proximal End Side Large Diameter Part 21, 23, 25 Taper Part 22, 24, 26 Distal End Side Small Diameter Part

Claims (3)

A core wire having a proximal-end large-diameter portion and a distal-end-side small-diameter portion having a smaller outer diameter than the proximal-end-side large-diameter portion, and an outer periphery of the core-wire distal end-side small-diameter portion along the axial direction With a mounted coil spring,
The core wire is composed of a wire material having a work-induced martensite amount of 20 to 60% by volume obtained by subjecting a wire rod of austenitic stainless steel to wire drawing and straightening.
When a 150 gf tensile load is applied for 10 seconds with the small-diameter portion on the distal end side of the core wire, to which the coil spring is mounted, wound once along the outer periphery of a rod having a diameter of 20 mm, a tip portion by winding A medical guide wire characterized by a warp angle of less than 5 °.   The medical guide wire according to claim 1, wherein the amount of processing-induced martensite of the wire constituting the core wire is 30 to 40% by volume.   The medical guide wire according to claim 1 or 2, wherein the austenitic stainless steel is SUS304 or SUS316.

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