Patent Publication Number: US-2023158278-A1

Title: Guide wire

Description:
TECHNICAL FIELD 
     The present invention relates to a guide wire having a sensor and inserted into a blood vessel. 
     BACKGROUND ART 
     In order to detect various physical quantities in a blood vessel such as a blood pressure or a blood flow rate, inserting a guide wire having a sensor into the blood vessel is performed. The guide wire is inserted into a vein from a lower part of a clavicle or a femoral area, for example, and a tip end thereof is delivered to a coronary artery. Then, the blood pressure or the like at the coronary artery is measured by the sensor provided at the tip end of the guide wire (Patent Document 1). 
     The sensor is located in an internal space of a circular tube-shaped housing constituting a part of the guide wire. For example, a housing made of metal is suitable for protecting the sensor because rigidity is high, but is hard to bow along a curve of the blood vessel. As a result, there is a problem that it is hard to pass the housing through a curved portion of the blood vessel. For this problem, each of Patent Documents 2 and 3 discloses a configuration in which a slit is formed on the housing to make the housing easy to be curved. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2003-225312 
         Patent Document 2: Japanese Patent Application Laid-Open No. 2014-147459 
         Patent Document 3: Japanese Patent No. 6395826 
       
    
     SUMMARY OF THE INVENTION 
     Although the housing on which the slit is formed is easy to be curved, when the housing is curved, the slit is deformed and an end portion of the slit is easy to fracture. Furthermore, also when a tensile force acts on the housing, the end portion of the slit is easy to fracture. On the other hand, as disclosed in Patent Documents 2 and 3, when the length of the slit in an extending direction is relatively shortened, strength of the slit increases, but the housing becomes hard to be curved or hard to be extended, and operability is impaired. 
     The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a guide wire in which a housing of a sensor is easy to be curved and a slit is hard to fracture. 
     Means for Solving the Problems 
     (1) A guide wire according to the present invention includes a wire material, a circular tube-shaped housing attached to the wire material, and a sensor located in an internal space of the housing. The housing has a slit penetrating a peripheral wall of the housing and extending in a helix. The slit has a central portion extending in the helix in a constant extending direction along the peripheral wall, and an end portion including one end of the slit and bent with respect to the central portion along a bending direction, the bending direction intersecting the extending direction and increasing a pitch of the helix. 
     By the slit, the housing becomes easy to be curved and easy to be extended. By the end portion of the slit, even when a tensile force acts on the housing, the end portion is hard to fracture. 
     (2) Preferably, the bending direction is parallel with an axis of the housing. 
     (3) Preferably, the end portion is curved in a U-shape. 
     (4) Preferably, a bending point of the central portion and the end portion has a round shape. 
     (5) Preferably, the pitch of the helix in the central portion of the first slit is larger in both end sides than at a center. 
     In the central portion of the first slit, the both end sides become easy to withstand pulling, and the center becomes easy to be extended in an axial direction. 
     (6) Preferably, the housing further has a second slit penetrating the peripheral wall of the housing and extending in a helix, and the first slit and the second slit form a double helix located alternately with respect to an axial direction of the housing. 
     By the double helix, the housing becomes further easy to be curved. 
     (7) Preferably, a synthetic resin is filled in the internal space of the housing, the internal space surrounded by the peripheral wall on which the slit is located. 
     Since a tensile force acting on the housing also acts on the synthetic resin, tensile strength is improved as a whole of the housing and the synthetic resin. 
     (8) A guide wire according to the present invention includes a wire material, a circular tube-shaped housing attached to the wire material, and a sensor located in an internal space of the housing. The housing has a slit penetrating a peripheral wall of the housing and extending in a helix. A synthetic resin is filled in the internal space of the housing, the internal space surrounded by the peripheral wall on which the slit is located. 
     Since a tensile force acting on the housing also acts on the synthetic resin, tensile strength is improved as a whole of the housing and the synthetic resin. 
     Effects of the Invention 
     According to the present invention, the housing of the sensor is easy to be curved, and the slit is hard to fracture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a guide wire system  10 . 
         FIG.  2    is a diagram showing a guide wire  30 . 
         FIG.  3    is a perspective view of a pressure sensor  11 . 
         FIG.  4    is a cross-sectional view showing an internal configuration of a housing  34 . 
         FIG.  5    is a diagram showing slits  51  to  54 . 
         FIG.  6    is a partially enlarged view of  FIG.  5   . 
         FIG.  7    is an enlarged view showing the slit  51  according to a modification example. 
         FIG.  8    is an enlarged view showing the slit  51  according to a modification example. 
         FIG.  9    is a diagram showing the housing  34  according to a modification example. 
         FIG.  10    is a diagram showing the housing  34  according to a modification example. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Hereinafter, preferred embodiments of the present invention are described. Note that it is needless to say that each embodiment is merely one embodiment of the present invention and that the embodiment can be changed without departing from the gist of the present invention. 
     [Guide Wire System  10 ] 
     As shown in  FIG.  1   , a guide wire system  10  includes a guide wire  30 , an arithmetic device  20 , and a female-type connector  40  connecting the guide wire  30  and the arithmetic device  20 . The guide wire  30  is an elongated rope body and is insertable into a blood vessel such as a coronary artery. The guide wire  30  includes, at a distal end portion, a pressure sensor  11  (see  FIG.  3   , an example of a sensor) that outputs electrical information in accordance with a pressure in the blood vessel. 
     The arithmetic device  20  includes a power supply unit  21  that supplies current to the pressure sensor  11  of the guide wire  30 , an arithmetic unit  22  that performs arithmetic processing on the electrical information output from the pressure sensor  11 , and a memory  23  that stores information necessary for the arithmetic processing. The electrical information output from the pressure sensor  11  is transmitted from the guide wire  30  via the female-type connector  40  and a cable  24  to the arithmetic unit  22 . The arithmetic unit  22  calculates a blood pressure based on the electrical information output from the pressure sensor  11 . In short, the guide wire system  10  is used to measure the blood pressure. 
     In  FIG.  1   , of both ends of the guide wire  30 , a fixed end (end connected to the female-type connector  40 ) is a proximal end (lower left end in  FIG.  1   ), and a free end (tip end when inserted into the blood vessel) is a distal end (upper left end in  FIG.  1   ). In the present specification, in the guide wire  30 , a side on which there is the proximal end is referred to as a proximal end side, and a side on which there is the distal end is referred to as a distal end side. 
     [Guide Wire  30 ] 
     The guide wire  30  is shown in  FIG.  2   . In  FIG.  2   , the left side is the distal end side of the guide wire  30 , and the right side is the proximal end side of the guide wire  30 . The guide wire  30  is roughly divided into a tip end portion  30 A (an example of a distal end portion), a core wire  31  (an example of a main body), and a male-type connector  39  (an example of a connector). The tip end portion  30 A includes a tip end guide portion  32 , a first helical body  33 , the housing  34 , and a second helical body  35 . Note that an axis  50  indicates an axis of the guide wire  30  when the guide wire  30  is in a straight state without being bowed or curved. 
     The core wire  31  is a columnar shaped-member and is a solid material made of stainless steel, for example. The tip end guide portion  32  is a hemispherical shaped-member disposed at the distal end and protruding to the distal end side, and abuts a blood vessel wall, thereby guiding a traveling direction of the guide wire  30  so as to follow the blood vessel. The first helical body  33  and the second helical body  35  are wire materials wound in a helical shape, and are configured to be bent more easily than the core wire  31  so that the distal end portion of the guide wire  30  is easy to follow the blood vessel. 
     The housing  34  is a casing that accommodates the pressure sensor  11  in an internal space thereof. The housing  34  has a circular tube shape. The housing  34  has two through holes  41 . Note that the two through holes  41  are disposed symmetrically by 180° with respect to the axis  50 , and only one of the through holes  41  appears in  FIG.  2   . Blood enters an inside of the housing  34  via the through holes  41  and contacts a diaphragm  13  ( FIG.  3   ) of the pressure sensor  11 . The housing  34  has slits  51 ,  52 ,  53 ,  54 . The slits  51 ,  52 ,  53 ,  54  will be described later in detail. 
     A taper pin  38  (see  FIG.  3   ) extends from the distal end of the core wire  31  toward the housing  34  in an internal space of the second helical body  35 . The taper pin  38  is a member that reinforces bending rigidity of the second helical body  35 . The taper pin  38  has a columnar shape, and its outer diameter gradually decreases from the distal end of the core wire  31  toward the housing  34 . Note that although not shown in each drawing, a tip end guide pin extends from the distal end of the housing  34  toward the tip end guide portion  32  in an internal space of the first helical body  33 . The tip end guide pin has a columnar shape and is a member that reinforces bending rigidity of the first helical body  33 . The tip end guide pin is fixed to the housing  34  and the tip end guide portion  32 . The male-type connector  39  is provided at the proximal end of the core wire  31 . The male-type connector  39  is inserted into the female-type connector  40 , thereby the pressure sensor  11  and the arithmetic device  20  are electrically connected. The core wire  31 , the first helical body  33 , and the second helical body  35  are examples of a wire material. 
     As shown in  FIG.  3   , the pressure sensor  11  includes a sensor main body  12 , the diaphragm  13 , abridge circuit  14 , four conductive wires  15 , and a connecting portion  16 . The sensor main body  12  is fixed to the taper pin  38  fixed to the core wire  31 , by the connecting portion  16  configured by an adhesive, for example. The diaphragm  13 , the bridge circuit  14 , and the four conductive wires  15  are attached to the sensor main body  12 . The bridge circuit  14  is a full-bridge circuit in which all of four resistive bodies  17  function as strain gauges for measurement. The bridge circuit  14  includes the four resistive bodies  17 , four terminals  18 A,  18 B, and four connecting bodies  19 . The four resistive bodies  17  are fixed to the diaphragm  13 . The four terminals  18 A,  18 B consist of two input terminals  18 A and two output terminals  18 B. Each connecting body  19  electrically connects each resistive body  17  to each of the terminals  18 A,  18 B. Each conductive wire  15  is electrically connected to each of the terminals  18 A,  18 B, extends toward a base end in an internal space of the core wire  31 , and is electrically connected to each connecting terminal of the male-type connector  39 . 
     In a state in which the guide wire  30  is inserted into the blood vessel and the blood pressure is applied to the pressure sensor  11 , the diaphragm  13  is elastically deformed in accordance with the blood pressure. Along with the elastic deformation of the diaphragm  13 , the four resistive bodies  17  are elastically deformed, and electric resistance values of the four resistive bodies  17  are changed. When a voltage is applied between the two input terminals  18 A in this state, a potential difference is generated between the two output terminals  18 B. Based on the potential difference, the blood pressure is calculated in the arithmetic device  20  ( FIG.  1   ). 
     As shown in  FIG.  4   , the pressure sensor  11  is located on the proximal end side of the through hole  41  in the internal space of the housing  34 . A synthetic resin  43  is filled in the internal space of the housing  34 , the internal space located on the proximal end side of the sensor main body  12  of the pressure sensor  11 . Furthermore, the synthetic resin  43  is also filled in the internal space of the housing  34 , the internal space located on the distal end side of the through hole  41 . The slits  51  to  54  to be described later are located on a peripheral wall  42  of the housing  34 , the peripheral wall  42  partitioning the internal space filled with the synthetic resin  43 . The synthetic resin  43  is an epoxy resin, a urethane resin, or a polyamide elastomer resin, for example. 
     [Slits  51 ,  52 ] 
     As shown in  FIG.  5   , the slits  51  to  54  are formed on the housing  34 . Each of the slits  51  to  54  penetrates the peripheral wall  42  of the housing  34 . The slits  51  to  54  extend in helices, taking the axis  50  of the housing  34  as a center. As shown in  FIG.  6   , when the housing  34  is viewed from a direction orthogonal to the axis  50 , an included angle θ1 formed by intersecting an extending direction Ds in which each of the slits  51  to  54  extends and the axis  50  is constant, and is approximately 60° in the present embodiment. Note that the extending directions Ds in which the slits  51  to  54  extend are parallel. In the present embodiment, when the housing  34  is viewed from the proximal end to the distal end along the axis  50 , the slits  51  to  54  each extend toward the distal end while rotating clockwise. 
     As shown in  FIG.  5   , the slits  51 ,  52  are located on a proximal side of the through hole  41 , in the housing  34 . The slits  53 ,  54  are located on a distal side of the through hole  41 , in the housing  34 . The slits  51 ,  52  form a double helix located alternately with respect to the axis  50  of the housing  34 . In other words, the slits  51 ,  52  are shifted in phase by a half cycle around the axis  50 . In further other words, the slit  52  is located at a position shifted by a half of a distance traveled by the slit  51  along the axis  50  in a cycle in which the slit  51  rotates one time around the axis  50 . The slits  53 ,  54  form a double helix as with the slits  51 ,  52 . 
     As shown in  FIG.  6   , the slit  51  has a central portion  55  forming a constant included angle θ1 with respect to the axis  50  and end portions  56  located on both sides of the axis  50  with respect to the central portion  55 . In the present embodiment, since the two end portions  56  are located symmetrically by 180° with respect to the axis  50 , the end portion  56  located on the distal end side is shown by a broken line in  FIG.  5   . Since the two end portions  56  has the same positional relationship with respect to the central portion  55  except that the positions with respect to the axis  50  and the extending directions are symmetric, hereinafter, the end portion  56  located on the proximal end side will be described in detail as an example. 
     As shown in  FIG.  6   , the central portion  55  extends forming a helix in which the extending direction Ds is constant. The end portion  56  is continuous with the proximal end of the central portion  55 . The end portion  56  constitutes one end of the slit  51 . Most part of the end portion  56  follows a bending direction De intersecting the extending direction Ds. In the present embodiment, the bending direction De is parallel with the axis  50 . A connecting point  57  of the central portion  55  and the end portion  56  forms a round shape bending smoothly. Most part of the end portion  56 , the part extending to the proximal end has a linear shape, and the linear-shaped portion follows the bending direction De. In the proximal end of the slit  51 , a pitch of the helix increases toward the proximal end, by the end portion  56 . 
     Although detailed description is omitted, the slit  53  has a central portion and end portions similar to those of the slit  51 . Furthermore, in the present embodiment, the slits  52 ,  54  do not have, on both ends, the end portions  56  such as the slit  51  has, and extend along the extending direction Ds over the entire range. 
     Actions and Effects of the Present Embodiment 
     According to the guide wire  30  according to the above-described embodiment, since the slits  51  to  54  are formed on the housing  34 , the housing  34  becomes easy to be curved and becomes easy to be extended along the axis  50 . Furthermore, since the formed slit  51  has the central portion  55  and the end portions  56 , even if a tensile force along the axis  50  acts on the housing  34 , the end portions  56  are hard to fracture. 
     Furthermore, since the synthetic resin  43  is filled in the internal space of the housing  34 , the space surrounded by the peripheral wall  42  on which the slits  51  to  54  are located, a tensile force acting along the axis  50  of the housing  34  also acts on the synthetic resin  43 , and tensile strength is improved as a whole of the housing  34  and the synthetic resin  43 . 
     Modification Examples 
     Although the bending direction De along which the end portion  56  extends follows the axis  50  in the above-described embodiment, the bending direction De may not necessarily follow the axis  50 . For example, as shown in  FIG.  7   , an included angle θ2 formed by the end portion  56  and the axis  50  may be 15°, 30°, 45°, or the like. Furthermore, as shown in  FIG.  8   , the end portion  56  may be curved in a U-shape from the central portion  55  and may extend in a so-called opposite direction. 
     Furthermore, although the slits  51 ,  53  have the end portions  56  in the above-described embodiment, the slits  51 ,  53  may not necessarily have the end portions  56  and may only have the central portion  55 , as shown in  FIG.  9   . In this aspect, tensile strength of the housing  34  is improved by the synthetic resin  43  filled in the internal space of the housing  34 , the internal space surrounded by the peripheral wall  42  on which the slits  51  to  54  are located. 
     Furthermore, although the slits  51 ,  52  and the slits  53 ,  54  form the double helix in the above-described embodiment, the slit  51  and the slit  53  may be formed on the housing  34  as a single helix, without being provided with the slit  52  and the slit  54 . Furthermore, the pitch of the slits  51  may not necessarily be constant. For example, as shown in  FIG.  10   , the slit  51  may be formed on the housing  34  as the single helix, and regarding a pitch (distance along the axis  50  between adjacent slits  51 ) of the helix in the central portion  55  of the slit  51 , a pitch P1 in both end sides may be larger than a pitch P2 at a center (P1&gt;P2). 
     As the pitch of the helix of the slit  51  becomes smaller, the housing  34  becomes easy to be extended along the axis  50 , whereas as the pitch becomes larger, tensile strength along the axis  50  becomes larger. When a tensile force along the axis  50  acts on the housing  34 , in the central portion  55  of the slit  51 , the center having the smaller pitch (P2) is extended more than the both ends having the larger pitch (P1). The central portion  55  of the slit  51  is extended along the axis  50 , thereby tensile length (stroke) until the housing  34  fractures becomes longer. 
     When the central portion  55  of the slit  51  is fully extended both at the center and in the both ends and tensile strength of the both ends of the central portion  55  is eventually exceeded, the housing  34  fractures near a boundary of the central portion  55  and the end portion  56  (near both ends of the central portion  55 ). Therefore, by decreasing the pitch P2 at the center of the central portion  55  of the slit  51 , the slit  51  can be made to be easy to extended along the axis  50  and stroke needed until the housing  34  fractures can be increased, whereas, by increasing the pitch Plat the both ends of the central portion  55  of the slit  51 , tensile force capable of withstanding until the fracture can be increased. 
     Furthermore, the pressure sensor  11  provided to the guide wire  30  is merely an example of a sensor, and other sensors or electronic circuits that measure physical quantities (temperature, flow velocity, or the like) of blood or the blood vessel other than the pressure may be provided. Furthermore, it is needless to say that the configuration of the distal end side of the guide wire  30  shown in the above-described embodiment is merely an example, and that the configurations of the helical body, the taper pin, the housing, or the like may be changed appropriately. 
     EXAMPLES 
     Examples 1 to 5 
     A circular tube made of stainless steel (SUS304) having a length of 7 mm, an outer diameter of 0.37 mm, and a thickness of 0.03 mm was used as the housing, the width of the slit was set to 0.02 mm, the included angle θ1 formed by the axis and the slit on a single helix was set to 60°, guide wires in which the included angle θ2 formed by the axis and an extending direction of the end portion of the slit was set to 15°, 30°, and 45°, a guide wire in which the end portion is parallel with the axis, and a guide wire in which the end portion is curved in a U-shape (see  FIG.  8   ) were formed, and these were respectively named Examples 1 to 5. 
     Examples 6 to 8 
     A circular tube made of stainless steel (SUS304) having a length of 7 mm, an outer diameter of 0.37 mm, and a thickness of 0.03 mm was used as the housing, the width of the slit was set to 0.02 mm, the axis and the end portion of the slit on a single helix were extended in parallel with the axis, guide wires in which a radius R at a boundary of the central portion and the end portion was set to 0.05, 0.3, and 0.4 were formed, and these were respectively named Examples 6 to 8. 
     Comparative Example 
     A circular tube made of stainless steel (SUS304) having a length of 7 mm, an outer diameter of 0.37 mm, and a thickness of 0.03 mm was used as the housing, the width of the slit was set to 0.02 mm, a guide wire having the axis and the slit on a single helix, the slit not having the end portion was formed, and this was named a comparative example. 
     [Tensile Strength] 
     In a state in which a wire material having a diameter of 0.08 mm was inserted into the housing for stabilizing the shape of a slit helical portion at the time of pulling, tensile strength when one end of the housing of each example and the comparative example was fixed and the other end was pulled was obtained using a simulation software. As for material properties of SUS304, Young&#39;s modulus was set to 200 GPa, Poisson&#39;s ratio was set to 0.3, yield stress was set to 250 MPa, and tangent modulus was set to 1, 450 MPa. The results are shown in Table 1. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Example 4 
                 Example 5 
                   
                   
                   
                   
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Parallel with 
                 Curved in 
                 Example 6 
                 Example 7 
                 Example 8 
                 Comparable 
               
               
                   
                 θ2 = 15° 
                 θ2 = 30° 
                 θ2 = 45° 
                 axis 
                 U-shape 
                 R = 0.05 
                 R = 0.3 
                 R = 0.4 
                 example 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Tensile strength (N) 
                 0.76 
                 1.09 
                 1.48 
                 1.78 
                 1.72 
                 1.15 
                 1.72 
                 1.99 
                 0.37 
               
               
                   
               
            
           
         
       
     
     As is clear from Table 1, in all of Examples 1 to 8, tensile strength was improved compared with the comparative example. Among Examples 1 to 5, as the included angle θ1 became larger, the tensile strength became stronger. Furthermore, Example 4 in which the extending direction of the end portion of the slit was parallel with the axis represented the strongest result. Among Examples 6 to 8, as the radius R became larger, the tensile strength became stronger. 
     Examples 9 to 12 
     A circular tube made of stainless steel (SUS304) having a length of 7 mm, an outer diameter of 0.37 mm, and a thickness of 0.03 mm was used as the housing, the width of the slit was set to 0.02 mm, the axis and the end portion of the slit on a single helix extends in parallel with the axis of the housing, guide wires in which the pitch (length between adjacent slits along the axial direction of the circular tube) of the slit on the single helix of 7 mm in total length was set to 100 μm, 150 μm, 200 μm, and 280 μm were formed, and these were named Examples 9 to 12. 
     A tensile strength test was performed on Examples 9 to 12 using the simulation software to which the same setting as the above-described one has been performed. Stroke length (mm) and tensile strength (N) at the time of the fracture are shown in Table 2. Note that in Example 9, even when the stroke length became 15 mm, a maximum equivalent stress needed for the fracture was not reached. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Example 
                 Example 
                 Example 
                 Example 
               
               
                   
                 9 
                 10 
                 11 
                 12 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Helical pitch 
                 100 μm 
                 150 μm 
                 200 μm 
                 280 μm 
               
               
                 Stroke (mm) 
                 &gt;15 
                 9.5 
                 6.5 
                 3.8 
               
               
                 Tensile strength (N) 
                 — 
                 1.6 
                 1.8 
                 2.3 
               
               
                   
               
            
           
         
       
     
     As is clear from Table 2, as the pitch of the slits became larger, the stroke length became shorter and the tensile strength became larger. From this, it can be said that when the pitch of the slit increases, although the slit portion becomes hard to be extended, the tensile strength becomes stronger. 
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
         
           
               11  pressure sensor (sensor) 
               30  guide wire 
               31  core wire (wire material) 
               33  first helical body (wire material) 
               34  housing 
               35  second helical body (wire material) 
               42  peripheral wall 
               43  synthetic resin 
               51  to  54  slit 
               55  central portion 
               56  end portion