Patent Publication Number: US-9844650-B2

Title: Guide wire for use with a catheter

Description:
CROSS-REFERENCFD TO RELATED APPLICATIONS 
     This application is a continuation application of application Ser. No. 13/958,903 filed Aug. 5, 2013, now U.S. Pat. No. 8,764,684 to be issued on Jul. 1, 2014, which is a continuation of application Ser. No. 10/539,399 filed Oct. 3, 2006, which is a non-provisional application of National Stage Entry of International Application No. PCT/IE03/00173 filed on Dec. 19, 2003, all of which are incorporated by reference in their entireties herein. 
    
    
     The present invention relates to a guide wire for use in a surgical or other procedure for accessing a remote site in the body of a human or animal subject, and in particular though not limited to a guide wire for use with a catheter. 
     Guide wires for locating a distal end of a catheter in a remote site in the body of a human or animal subject are known. Such guide wires are commonly used for guiding a catheter along narrow blood vessels to a site in the cardiovascular system of the subject for enabling a cardiovascular procedure to be carried out, for example, the insertion of a stent in a coronary artery. Depending on the type of guide wire and its use, the guide wire is typically introduced through a cannula into a suitable blood vessel in the thigh, arm or neck of the subject, and is passed through the blood vessels to the desired site in the cardiovascular or other system. In cases where a guide wire is for use with a catheter for inserting a stent in a coronary artery of the heart of a subject, the guide wire may be introduced through a guide catheter, and through the guide catheter to the coronary artery. Once the guide wire has reached the desired site, the appropriate catheter is then advanced over the guide wire to the site. 
     Due to the relatively narrow diameter of the blood vessels through which a guide wire has to pass, and in particular, due to the tortuous nature of the blood vessels, and particularly the tortuous nature of the blood vessels of the cardiovascular system, and the number of branched blood vessels, it is essential that the guide wire be of a construction which facilitates bending of the guide wire so that the guide wire can bend around corners, and additionally, it is essential that the guide wire can be selectively directed into branched blood vessels. In order to facilitate bending of the guide wire around corners, such guide wires are provided to be relatively flexible, and the desired flexibility, in general, is obtained by selecting the material and dimensions of the guide wire to provide the desired degree of flexibility. In order that such guide wires can be directed into a branched blood vessel, a distal portion of the guide wire is adapted to be bent to a set curved configuration, and to retain the set curved configuration as the guide wire is being urged through the vascular system. As the guide wire is being urged through the vascular system, when it is desired to direct the guide wire into a branched vessel, the guide wire is rotated in order to align the distal tip of the guide wire with the branched vessel, and once aligned with the branched vessel, further forward urging of the guide wire directs the guide wire into the branched vessel. Accordingly, in order that the distal tip of the guide wire can be directed towards and aligned with a branched vessel, it is important that the guide wire be torsionally rigid over its length, otherwise axial twisting of the guide wire occurs between the distal end and the proximal end, since rotation of the guide wire must be undertaken by rotating the proximal end of the guide wire. 
     In general, by appropriately selecting the material and dimensions of the guide wire, the required degree of torsional rigidity can be obtained relatively easily over most of the guide wire. However, in general a greater degree of flexibility is required towards the distal end of the guide wire, and in order to provide the extra degree of flexibility and to facilitate bending of the guide wire into a desired set curved configuration adjacent the distal end, in general, such guide wires are provided with a tapered portion adjacent the distal end. Such a guide wire is disclosed in U.S. Pat. No. 4,545,390 of Leary. While the provision of the tapered distal portion provides the additional degree of flexibility, and also lends itself readily to being bent to form a desired set curved configuration, unfortunately, the tapering of the guide wire at the distal portion significantly reduces the torsional rigidity of the guide wire in the distal portion. Thus, while the guide wire over the majority of its length is adequately torsionally rigid, the distal portion has little or no torsional rigidity, and thus, significant twisting can occur in the tapered distal portion between the proximal end and the distal tip of the guide wire. This leads to significant difficulty in aligning the distal tip of the guide wire with a selected branched vessel by rotating the guide wire at its proximal end. 
     In order to improve the torsional rigidity of the tapered distal portion of the guide wire of Leary in U.S. Pat. No. 4,545,390, a sleeve formed by a tightly wound coiled spring is provided, and the tapered distal portion is located coaxially within the tightly coiled spring. The spring is secured to the distal end of the distal portion and is also secured to the guide wire intermediate the tapered distal portion and the proximal end. However, while the provision of the tightly wound coiled spring extending around the tapered distal portion does to some extent enhance the torsional rigidity of the distal portion, the degree of enhancement of the torsional rigidity is limited, and axial twisting of the guide wire occurs between the proximal end and the distal tip. 
     U.S. Pat. No. 4,080,706 of Heilman discloses a guide wire comprising a main wire which extends between a proximal end and a distal end of the guide wire, and which is located within a tightly wound coiled spring sleeve. A distal portion of the guide wire is flattened and tapered to form a ribbon-like portion which increases the degree of flexibility of the guide wire adjacent the distal end thereof. However, the flattened ribbon-like distal portion of the main wire has little torsional rigidity, and the provision of the tightly wound coiled spring sleeve would add little to the torsional rigidity of the guide wire adjacent the ribbon-like distal portion of the main wire. Thus, if one were to form a set curved configuration in the flattened ribbon-like distal portion of the guide wire of Heilman in order to facilitate alignment of the distal tip of the guide wire with a branched vessel, the lack of torsional rigidity of the distal portion of the guide wire would render alignment of the distal tip of the guide wire with the branched vessel virtually impossible. Due to the lack of torsional rigidity of the flattened ribbon-like distal portion of the main wire, rotation of the proximal end of the guide wire would merely lead to twisting of the flattened ribbon-like distal portion, thereby rendering it impossible to align the distal tip of the guide wire with a branched vessel by rotating the guide wire at its proximal end. 
     There is therefore a need for a guide wire which is sufficiently flexible to facilitate bending of the guide wire around corners and bends in the vascular system, and which also is provided with a distal portion which is adapted to be bent to a set curved configuration, and which is sufficiently torsionally rigid to prevent axial twisting of the guide wire between the distal end of the guide wire and the proximal end thereof so that rotation of the guide wire adjacent its proximal end results in a corresponding degree of rotation of the guide wire adjacent its distal tip. 
     The present invention is directed towards providing such a guide wire. 
     According to the invention there is provided a guide wire for use in a surgical or other procedure for accessing a remote site in the body of a human or animal subject, the guide wire defining a longitudinally extending axis, and terminating at one end in a proximal portion, and at an opposite end in a distal portion for accessing the remote site, the distal portion terminating adjacent a distal end thereof in a guide portion, the guide portion being adapted to be shaped to a desired curved configuration for facilitating guiding of the guide wire into a branched vessel of the subject, wherein a reinforcing means is provided on the distal portion for minimising axial twisting of the distal portion between a proximal end of the distal portion and the guide portion thereof. 
     In one embodiment of the invention the reinforcing means is an elongated reinforcing means having a proximal end and a distal end. Preferably, the reinforcing means extends along at least a portion of the distal portion between the proximal end of the distal portion and the guide portion. Advantageously, the distal end of the reinforcing means is spaced apart from the distal end of the distal portion of the guide wire and defines with the distal end of the distal portion of the guide wire the guide portion thereof. Ideally, the reinforcing means extends from the proximal end of the distal portion, and preferably, the proximal end of the reinforcing means substantially coincides with the proximal end of the distal portion of the guide wire. 
     In one embodiment of the invention the reinforcing means extends in a generally axial direction. 
     In another embodiment of the invention the distal portion of the guide wire defines a longitudinally extending flat surface, and the reinforcing means extends along the flat surface and from the flat surface terminating in a longitudinally extending edge. 
     Preferably, the distal portion of the guide wire is of rectangular transverse cross-section defining a pair of opposite major flat surfaces, joined by a pair of opposite minor surfaces, the major flat surfaces defining a central major plane located midway between the major surfaces, and the minor surfaces defining a central minor plane located midway between the minor surfaces. 
     In one embodiment of the invention the reinforcing means is located on one of the major flat surfaces, and in another embodiment of the invention the reinforcing means is located on both of the major flat surfaces. 
     Advantageously, the respective major flat surfaces converge towards each other towards the distal end of the distal portion. 
     In one embodiment of the invention the transverse distance of the longitudinally extending edge of each reinforcing means from the central major plane is substantially constant along the reinforcing means. 
     In another embodiment of the invention each reinforcing means extends parallel to the central minor plane. Preferably, each reinforcing means coincides with the central minor plane. Alternatively, each reinforcing means extends at an angle greater than zero degrees to the central minor plane, and in one embodiment of the invention each reinforcing means extends adjacent one of the minor surfaces. 
     In one embodiment of the invention one reinforcing means extends from each of the major flat surfaces, one of the reinforcing means extending adjacent one of the minor surfaces, and the other reinforcing means extending adjacent the other minor surface. 
     In another embodiment of the invention each reinforcing means comprises an elongated reinforcing member. Preferably, each reinforcing member defines opposite longitudinally extending sides. Advantageously, the opposite longitudinally extending sides of each reinforcing member terminate along the longitudinally extending edge thereof, and preferably, the opposite longitudinally extending sides of each reinforcing member are parallel to each other. Alternatively, the opposite longitudinally extending sides of each reinforcing member converge towards the longitudinally extending edge thereof for defining the longitudinally extending edge as a longitudinally extending ridge. 
     In one embodiment of the invention the longitudinally extending edge of each reinforcing member converges towards the distal portion adjacent the distal end of the reinforcing member. 
     In another embodiment of the invention each reinforcing means is integrally formed with the distal portion. 
     In a further embodiment of the invention each reinforcing means and the distal portion are of metal and are formed by forging from a single piece of metal. Alternatively, each reinforcing means and the distal portion are of metal and are formed by rolling from a single piece of metal. 
     In one embodiment of the invention the distal portion of the guide wire extends through a sleeve, and a first securing means at the distal end thereof secures the distal portion to the sleeve, the first securing means defining the distal end of the guide wire. Preferably, the first securing means is shaped to form a dome shaped distal end for facilitating passage of the guide wire smoothly through a vessel of the subject. Advantageously, the guide portion is located between each reinforcing means and the first securing means. 
     In one embodiment of the invention the first securing means comprises a solder joint. Alternatively, the first securing means comprises an adhesive joint, or alternatively, the first securing means comprises a brazed joint. 
     In one embodiment of the invention the sleeve extends beyond the proximal end of the distal portion along a portion of the guide wire. Preferably, a proximal end of the sleeve is secured to the guide wire by a second securing means. 
     In one embodiment of the invention the second securing means comprises one of an adhesive joint, or a solder joint, or a brazed joint. 
     In another embodiment of the invention the sleeve is secured to the guide wire at at least one intermediate location intermediate the proximal end and the distal end of the sleeve by an intermediate securing means. 
     In a further embodiment of the invention the intermediate securing means comprises one of an adhesive joint, a solder joint, or a brazed joint. 
     In another embodiment of the invention at least a portion of the sleeve adjacent the distal end thereof is of a radiopaque material. 
     Preferably, the sleeve comprises a tightly wound coiled spring of a metal material. Additionally, or alternatively, the sleeve comprises a tubular member, and the tubular member may be of plastics material. 
     In another embodiment of the invention the sleeve is formed from alternate portions of the tightly wound coiled spring and the tubular member. 
     In a further embodiment of the invention at least a portion of the sleeve is formed from one or more of the following materials or alloys thereof:
         platinum,   gold,   tantalum.       

     Preferably, the guide wire is substantially torsionally rigid between the distal portion and the proximal portion of the guide wire for minimising axial twisting of the guide wire between the proximal portion thereof and the guide portion. 
     In one embodiment of the invention a portion of the guide wire adjacent the distal portion thereof tapers towards the distal portion. 
     In another embodiment of the invention the distal portion of the guide wire and the guide wire are integrally formed from one piece of material. 
     The invention also provides a distal portion for a guide wire of the type for use in a surgical or other procedure for accessing a remote site in the body of a human or animal subject, the guide wire defining a longitudinally extending axis, and the distal portion having a proximal end and a distal end, the proximal end of the distal portion being adapted for securing to the guide wire, the distal portion terminating in a guide portion adjacent the distal end thereof, the guide portion being adapted to be shaped to a desired curved configuration for facilitating guiding of the guide wire into a branched vessel of the subject, characterised in that a reinforcing means is provided on the distal portion for minimising axial twisting of the distal portion between a proximal end of the distal portion and the guide portion thereof. 
     The invention also provides in combination a catheter, and the guide wire according to the invention. 
     The advantages of the invention are many. The provision of the reinforcing means in the distal portion of the guide wire significantly increases the torsional rigidity of the distal portion, thereby any danger of axial twisting of the distal portion is minimised. By minimising axial twisting of the distal portion, provided the guide wire up to the distal portion is of adequate torsional rigidity, rotation of the guide wire at its proximal end results in rotation of the distal end through a corresponding angle to that through which the proximal end is rotated. Thus, when a desired curvature is formed in the guide portion of the distal portion, the distal tip of the guide wire can be readily directed towards and align with a branched vessel into which the guide wire is to be urged by rotating the proximal end of the guide wire through an appropriate angle for aligning the distal tip with the branched vessel. By locating the reinforcing means so that it extends from the proximal end of the distal portion to the guide portion, torsional rigidity of the distal portion is maintained over its length between its proximal end and the guide portion. The provision of the reinforcing means as an elongated reinforcing member which extends from a surface, and in particular a flattened major surface of the distal portion, further enhances the torsional rigidity of the distal portion. By locating the reinforcing member so that it substantially coincides with the central minor plane of the distal portion further enhances the torsional rigidity of the distal portion. When the distal portion is provided to be of rectangular cross-section with respective opposite major surfaces, the provision of the reinforcing means significantly enhances the torsional rigidity of the distal portion. Indeed, by providing the reinforcing means as an elongated reinforcing member, which preferably coincides with the central minor plane of the distal portion significantly enhances the torsional rigidity of the distal portion. The provision of a pair of reinforcing members, while not essential, on respective opposite major surfaces of the distal portion further enhances the torsional rigidity of the distal portion. 
    
    
     
       The invention will be more clearly understood from the following description of some preferred embodiments thereof, which are given by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a side elevational view of a guide wire according to the invention, 
         FIG. 2  is an enlarged partly cut away side elevational view of the guide wire of  FIG. 1 , 
         FIG. 3  is an enlarged partly cut away plan view of the guide wire of  FIG. 1 , 
         FIG. 4  is a transverse cross-sectional end elevational view of the guide wire of  FIG. 1  on the line IV-IV of  FIG. 2 , 
         FIG. 5  is an enlarged side elevational view of the guide wire of  FIG. 1  illustrating a portion only of the guide wire of  FIG. 1 , 
         FIG. 6  is a side elevational view of the portion of the guide wire of  FIG. 5  in a different configuration, 
         FIGS. 7( a ) and 7( b ), and 8( a ) and 8( b )  are perspective views of a reference piece and a test piece representing a portion of the guide wire of  FIG. 1  during comparative finite element analysis, 
         FIGS. 9 and 10  are top plan views of portions of guide wires according to further embodiments of the invention, 
         FIGS. 11( a ) to ( p )  are transverse cross-sectional end elevational views similar to  FIG. 4  of guide wires according to further different embodiment of the invention, 
         FIG. 12  is a view similar to  FIG. 3  of a guide wire according to another embodiment of the invention, 
         FIG. 13  is a transverse cross-sectional end elevational view of the guide wire of  FIG. 12  on the line XIII-XIII of  FIG. 12 , 
         FIG. 14  is a view similar to  FIG. 3  of a guide wire according to another embodiment of the invention, and 
         FIG. 15  is a transverse cross-sectional end elevational view of the guide wire of  FIG. 14  on the line XV-XV of  FIG. 14 . 
     
    
    
     Referring to the drawings and initially to  FIGS. 1 to 6  thereof, there is illustrated a guide wire according to the invention, indicated generally by the reference numeral  1 , for use with a catheter (not shown) for guiding the catheter to a remote site in the body of a human or animal subject. The guide wire  1  according to this embodiment of the invention is particularly suitable for accessing a remote site, for example, a coronary artery in the cardiovascular system of a subject for in turn guiding a catheter to the remote site. However, it will be readily apparent to those skilled in the art that the guide wire  1  is suitable for accessing any remote site in the body, be it in a vasculature system or otherwise. For example, the guide wire  1  is suitable for accessing renal vessels, the neuro-vasculature system, the fallopian tubes, and other such vessels and sites. 
     The guide wire  1  comprises an elongated core wire  3  of metal, in this embodiment of the invention stainless steel, which extends between a proximal end  5  and a distal end  6 , and defines a longitudinally extending central axis  8 . The distal end  6  of the guide wire  1  forms a distal tip  9  which in use forms the leading end of the guide wire  1  as it is urged through the blood vessels or other vessels in the subject to the remote site. The core wire  3  over most of its length from the proximal end  5  is of circular transverse cross-section of constant diameter in the range of 0.2 mm to 0.5 mm, and towards its distal end at a location  10  commences to taper towards the distal end  6 . The core wire  3  tapers in multiple steps, in this embodiment of the invention three steps providing three tapering portions  14 ,  15  and  16  of circular transverse cross-section, between the location  10  and a distal portion  18  for increasing the flexibility of the guide wire  1  towards the distal end thereof. The tapering portions  14 ,  15  and  16  terminate in corresponding portions  19 ,  20  and  21 , respectively, which are of circular transverse cross-section of constant diameter. The constant diameter portion  21  terminates in the distal portion  18 . A sleeve  22  provided in this embodiment of the invention by a tightly wound coiled spring  23  of metal as will be described below extends from the tapering portion  14  to the distal end  6  of the guide wire  1 , and is secured to the core wire  3  at the distal end  6  by a first securing means, in this embodiment of the invention by a first solder joint  24 . The first solder joint  24  forms a dome shaped portion  25  which forms the distal tip  9  of the guide wire  1 . The dome shaped portion  25  minimises any risk of trauma to a subject as the guide wire  1  is being urged through the vascular system. 
     The distal portion  18  extends from the portion  21  at a proximal end  26  to a distal end  27 , and is flattened to be of ribbon-like construction defining a pair of opposite major surfaces  29  and  30  and opposite minor surfaces  31  and  32 . The distal portion  18  tapers gradually from its proximal end  26  to its distal end  27  with the respective major surfaces  29  and  30  converging towards each other. The major surfaces  29  and  30  define a central major plane  33  located midway between the major surfaces  29  and  30 , and the minor surfaces  31  and  32  define a central minor plane  34  midway between the minor surfaces  31  and  32 , and perpendicular to the central major plane  33 . 
     A reinforcing means comprising a reinforcing member  38  extends longitudinally along one of the major surfaces  29  and  30  of the distal portion  18  for increasing the torsional rigidity of the distal portion  18 . In this embodiment of the invention the reinforcing member  38  extends along the major surface  29 . The reinforcing member  38  coincides with the central minor plane  34 , and extends axially along the major surface  29  from the proximal end  26  and terminates at  40 . A guide portion  42  is defined in the distal portion  18  between the location  40  at which the reinforcing member  38  terminates and the first solder joint  24 . The guide portion  42  of the distal portion  18  is provided without the reinforcing member  38  for facilitating bending of the guide portion  42  to a desired set curved configuration prior to entering the guide wire  1  into the vascular system of the subject, so that the distal tip  9  of the guide wire  1  can be offset from the central axis  8  for facilitating aligning of the distal tip  9  with a branched vessel of the vascular system, and guiding the guide wire  1  into a branched vessel during urging of the guide wire  1  through the vascular system of the subject. 
     In this embodiment of the invention the distal portion  18  and the reinforcing member  38  are integrally formed with the tapering portions  14 ,  15  and  16  and the constant diameter portions  19 ,  20  and  21 , and with the core wire  3  by appropriately drawing, forging and/or rolling the core wire  3 . Typically, the distal portion  18  is formed by forging or rolling, while the tapering portions  14 ,  15  and  16  and the constant diameter portions  19 ,  20  and  21  typically are formed by centreless grinding. 
     In this embodiment of the invention the axial length A of the distal portion  18  extending from the proximal end  26  to the distal end  27  is approximately 23 mm. The distal portion  18  tapers from a thickness t 1  of approximately 0.06 mm at its proximal end  26  to a thickness t 2  of approximately 0.02 mm at its distal end  27 . The axial length C of the guide portion  42  is approximately 5 mm. The reinforcing member  38  extends for a length B of approximately 18 mm from the proximal end  26  to the location  40 . The reinforcing member  38  is of rectangular transverse cross-section and defines opposite sides  37  which extend to a longitudinally extending edge  44 . The reinforcing member  38  is of thickness t 3  of approximately 0.05 mm, and tapers at a portion  43  at its distal end towards the location  40  for an axial distance of approximately 0.05 mm. The distance d from the central major plane  33  to the longitudinally extending edge  44  of the reinforcing member  38  from the proximal end  26  to the commencement of the tapering portion  43  is substantially constant, and in this embodiment of the invention is approximately 0.03 mm. However, depending on the use to which the guide wire  1  is to be put, the axial length A of the distal portion  18  may vary between 13 mm and 25 mm, and the axial length C of the guide portion may vary between 4 mm and 8 mm. Additionally, the thickness t 1  of the distal portion  18  adjacent its proximal end may vary between 0.05 mm and 0.1 mm. 
     Returning now to the sleeve  22 , the sleeve  22  is formed by the spring  23  which in this embodiment of the invention comprises a proximal spring  45  and a distal spring  46 . Both springs  45  and  46  are tightly wound helical springs, the distal spring  46  being less tightly wound than the proximal spring  45  to increase the flexibility of the guide wire adjacent the distal portion  18 . The proximal spring  45  is of stainless steel and is brazed to the core wire  3  at the tapering portion  14  by a second securing means, namely, by a second solder joint  47 . The proximal and distal springs  45  and  46  are secured together by an intermediate securing means, namely, an intermediate solder joint  49 . The intermediate solder joint  49  secures the proximal and distal springs  45  and  46  only together, and the springs  45  and  46  are free floating at the intermediate solder joint  49  relative to the core wire  3 . The distal spring  46  is of a radiopaque material, in this embodiment of the invention platinum alloy. 
     In use, prior to entering the guide wire  1  into the vascular system of a subject, the guide portion  42  of the distal portion  18  is bent to a desired set curved configuration for facilitating guiding and directing the guide wire  1  into branched vessels. Once bent, the guide portion  42  retains the set curved configuration during use of the guide wire  1 . The guide wire  1  is then entered into the vascular system of the subject, and when it is desired to enter the guide wire  1  into a branched vessel, the guide wire  1  is rotated about its axis by rotating the proximal end  5  of the guide wire  1  until the distal tip  9  is directed towards and aligned with the branched vessel into which the guide wire  1  is to be entered. The guide wire  1  is then urged further into the vascular system so that the distal tip  9  enters the branched vessel, and further urging of the guide wire  1  into the vascular system urges the guide wire  1  through the branched vessel, and so on until the distal tip  9  of the guide wire is at the remote site at which the surgical procedure is to be carried out. 
     By virtue of the fact that the reinforcing member  38  is provided on the distal portion  18  from its proximal end  26  to the location  40  adjacent the guide portion  42 , axial twisting of the distal portion  18  is substantially avoided, and accordingly, each incremental angular rotation of the guide wire  1  at the proximal end  5  results in a corresponding incremental angular rotation of the distal end  6  of the guide wire  1 , and thus, when the guide portion  42  is bent to a desired set curved configuration, the distal tip  9  can readily easily be aligned with a branched vessel into which the guide wire  1  is to be urged. 
     Comparative finite element analysis was carried out on a computer simulated test piece which was of similar transverse cross-section to that of the distal portion  18  of the guide wire  1  with a member similar to the reinforcing member  38 . The analysis was also carried out on a computer simulated reference piece, which was also of similar transverse cross-section to that of the distal portion  18 , but which was provided without the reinforcing member. The comparative finite element analysis was carried out in order to establish the increase in torsional rigidity provided by one reinforcing member on the distal portion  18  of the guide wire  1 . The finite element analysis is described with reference to  FIGS. 7 and 8 . The reference piece is illustrated in  FIGS. 7( a ) and 8( a ) , while the test piece is illustrated in  FIGS. 7( b ) and 8( b ) . 
     In order to investigate the torque response of the test piece and the reference piece, a Finite Element Analysis Method (FEAM) was utilised. The reference piece and the test piece were simulated to be of the same material and of equal length, and formed by the same forming process, and of similar lengths. The material of both the test piece and the reference piece was simulated to be 304v stainless steel with a modulus of elasticity of 210 Gpa and a Poisson&#39;s Ratio of 0.3. For modelling purposes, the material was assumed to be linear elastic in behaviour. The reference piece and the test piece were constrained in all degrees of freedom in the end plane (z=0) plane. Simulated forces F were applied to the corners at opposite sides in the vertical y-direction as shown in  FIGS. 8( a ) and 8( b ) . The meshes generated by the analysis are illustrated in  FIGS. 8( a ) and 8( b ) . The force F applied to the respective opposite sides of the reference piece had a magnitude of 0.01 lbf. In order to have the same moment applied to the test piece as that applied to the reference piece, forces were applied to the respective opposite sides of the test piece with a magnitude of 0.008772 lbf. 
     The deformed geometry plots for both the reference piece and the test piece when subjected to the loading condition described above are shown in  FIGS. 8( a ) and 8( b ) . The y-direction reaction forces on the constrained corner nodes of the unloaded end of each of the reference and the test pieces were investigated. The maximum values of these reaction forces in both the positive and negative y-directions are shown in Table 1 below. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Maximum values of the y-direction reaction 
               
               
                 forces at the constrained nodes. 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Increase in 
               
               
                   
                   
                   
                 torque response 
               
               
                   
                 Uniform 
                 Uniform 
                 of uniform 
               
               
                   
                 cross-section 
                 cross-section 
                 cross-section 
               
               
                 Force 
                 reference piece 
                 test piece 
                 test piece 
               
               
                   
               
               
                 Max. positive y- 
                  0.94861E−02 
                  0.10974E−01 
                 15.7% 
               
               
                 direction reaction force 
               
               
                 Max. negative y- 
                 −0.94730E−02 
                 −0.11363E−01 
                 20.0% 
               
               
                 direction reaction force 
               
               
                   
               
            
           
         
       
     
     From Table 1, it can be seen that the reaction forces, and hence the torque response of the test piece was increased by approximately 15% to 20% over the reference piece, thus significantly enhancing the torsional rigidity of the test piece, and in turn minimising its tendency to axially twist. Thus, the results of the comparative finite element analysis indicate that the provision of the reinforcing member  38  on the distal portion  18  significantly increased the torsional rigidity of the distal portion  18  over and above its torsional rigidity if it were not provided with the reinforcing member  38 . Accordingly, the provision of the reinforcing member  38  on the distal portion  18  significantly reduces axial twisting of the distal portion  18  about the central axis  8  as a result of torque induced in the guide wire by rotating the proximal end  5  for in turn rotating the distal tip  9  for alignment with a branched vessel. 
     Referring now to  FIG. 9 , there is illustrated a distal portion  50  of a guide wire according to another embodiment of the invention. The guide wire of which the distal portion  50  forms a part is substantially similar to the guide wire  1 , and similar components are identified by the same reference numerals. The only difference between the distal portion  50  and the distal portion  18  of the guide wire  1  is that the reinforcing member  38 , instead of being located to coincide with the central minor plane  34  of the distal portion  18 , extends at an angle to the central minor plane  34 . The reinforcing member  38  on the major surface  29  extends diagonally from the minor surface  31  adjacent the proximal end  26  to the minor surface  32  adjacent the location  40 . A second reinforcing member could be provided on the opposite major surface  30 , and could extend at a similar angle to the central minor plane  34 , but in the opposite direction. 
     Referring now to  FIG. 10 , there is illustrated a distal portion  55  of a guide wire according to another embodiment of the invention. The guide wire of which the distal portion  55  forms a part is similar to the guide wire  1  and similar components are identified by the same reference numerals. The main difference between the distal portion  55  and the distal portion  18  is that in this embodiment of the invention, while the reinforcing member  38  coincides with the central minor plane  34 , the sides  37  of the reinforcing member  38  converge towards the central major plane  33  adjacent the location  40 . 
     Referring now to  FIGS. 11( a ) to 11( p ) , end views of distal portions  60   a  to  60   p  are illustrated of guide wires according to other embodiments of the invention. The guide wires of which the distal portions  60   a  to  60   p  form part are similar to the guide wire  1  and similar components are identified by the same reference numerals. The distal portions  60   a  to  60   p  of the guide wires according to these other embodiments of the invention are views looking in from the distal end of the respective distal portions. As can be seen, different types of reinforcing means are provided on the distal portions  60   a  to  60   p.    
     In the distal portions of  FIGS. 11( a ) and ( i )  the reinforcing means is provided by a reinforcing ridge  61  formed by shaping the distal portion  60 . In the distal portion of  FIG. 11( j )  the reinforcing means is also provided by shaping the distal portion to form a twisted portion  62 . 
     In the distal portion  60  of  FIG. 11( b )  a pair of reinforcing ridges  63  are provided on the respective opposite major surfaces  29  and  30 . Similarly, in the distal portion  60  of  FIGS. 11( d ), ( e ), ( k ), ( l ), ( n ) and ( o )  the reinforcing ridges  63  are provided on the respective opposite major surfaces  29  and  30 . The distal portion  60  of  FIG. 11( i )  is similar to that of  FIG. 11( e )  with the exception that only a single reinforcing ridge  63  is provided. 
     In the distal portion  60  of  FIGS. 11( m ) and ( p )  instead of the reinforcing means being formed by reinforcing ridges, the reinforcing means are provided by increasing the cross-section of the distal portion  60  adjacent the edges defining the minor surfaces  31  and  32 . 
     Otherwise the reinforcing means of the distal portion  60  of the remaining distal portion  60  of  FIG. 11  are clear from the drawings. 
     Referring now to  FIGS. 12 and 13 , there is illustrated a guide wire  70  according to another embodiment of the invention. The guide wire  70  is substantially similar to the guide wire  1  and similar components are identified by the same reference numerals. The main difference between the guide wire  70  and the guide wire  1  is in the sleeve  22 . In this embodiment of the invention the proximal spring  45  is replaced with a tubular sleeve  71  of plastics material having a proximal end  72  and a distal end  73 . The proximal end  72  forms a tight fit on the tapering portion  14 , and the distal end  73  of the sleeve  71  is secured to the core wire  3  by an intermediate securing means provided by a securing ring  75  of stainless steel, which is soldered to the core wire  3 . The tubular sleeve  71  engages the securing ring  75  with a tight engagement fit. The proximal end of the distal spring  46  is soldered to the securing ring  75  by a solder joint. Otherwise the guide wire  70  is similar to the guide wire  1  and its use is likewise similar to that of the guide wire  1 . 
     Referring now to  FIGS. 14 and 15 , there is illustrated a guide wire according to a further embodiment of the invention, indicated generally by the reference numeral  80 . The guide wire  80  is substantially similar to the guide wire  1  and similar components are identified by the same reference numerals. In this embodiment of the invention the sleeve  22  is formed by a tubular sleeve  81  of plastics material, which is similar to the tubular sleeve  71  of the guide wire  70 , and proximal and distal springs  83  and  84 , respectively, which are similar to the proximal and distal springs  45  and  46  of the guide wire  1 . The springs  83  and  84  are secured together by an intermediate solder joint  85 , similar to the intermediate solder joint  49  of the guide wire  1 . The proximal end of the proximal spring  83  is secured to the core wire  3  by an intermediate securing means, provided by a securing ring  86 , which is similar to the securing ring  75  of the guide wire  70 . The proximal spring  83  is soldered to the securing ring  86 , and the tubular sleeve  81  is bonded to the securing ring  86  by an adhesive. Additionally, in this embodiment of the invention a pair of reinforcing members  38  are provided, one reinforcing member  38  being provided on each of the major surfaces  29  and  30 . Otherwise, the guide wire  80  is similar to the guide wire  1 . 
     While the guide wires according to the invention have been described for use with a catheter, it is envisaged that in certain cases the guide wires may be used without a catheter, or may be used for other purposes. 
     Additionally, while the guide wires have been described as comprising a core wire of stainless steel, the core wire may be of any suitable material. Similarly, while it is preferable, it is not essential that the distal portion of the core wire should be integrally formed with the core wire. Similarly, it is not essential that the reinforcing member or members be integrally formed with the distal portion, it or they may be brazed, soldered, welded or otherwise secured onto the distal portion, and in which case, it will be appreciated that the material of the reinforcing member or members may be different to that of the distal portion, and where the distal portion is not integrally formed with the core wire, the distal portion may be of a different material to that of the core wire. 
     While the guide wire of  FIGS. 1 to 6  has been described as comprising one reinforcing member, in certain cases, it is envisaged that a pair of reinforcing members may be provided, one being provided on each of the major surfaces of the distal portion. 
     While the distal portion has been described as being of flat ribbon-like construction, this is not essential, the distal portion may be of any suitable or desired cross-section. 
     Needless to say, the sleeve, be it in the form of a spring or of a tubular member, may be of any desired or suitable material. It is also envisaged that in certain cases the sleeve may be provided as a single tubular member, or a pair of tubular members, or a single spring or otherwise, and indeed, in certain cases, it is envisaged that the sleeve in certain embodiments of the invention may be omitted. 
     While the sleeve has been described as comprising a spring which is soldered to the distal end of the distal portion, the spring may be secured by any other securing means to the distal end of the distal position, for example, the sleeve, be it a spring or a tubular member of metal or plastics, may be secured to the distal end of the distal portion by an adhesive, such as, for example, an epoxy adhesive, which would similarly be dome shaped. Additionally, instead of soldering, the spring may be secured to the distal end by brazing or welding. Furthermore, the sleeve at its proximal end may terminate at any suitable location along the core wire, and not necessarily at any of the tapered portions. 
     While the core wire has been described as being tapered over a number of tapering portions with portions of constant diameter in between, while this is preferable, it is not essential, and indeed, the core wire may be tapered over one continuous tapering portion only. It is envisaged that in certain cases, the core wire may not taper towards the distal portion, and in which case it would be of constant diameter to the distal portion. 
     While the distal portion and the reinforcing member as well as the guide portion have been described as being of specific dimensions, the distal portion, the reinforcing member and the guide portion may be of any other suitable or desired dimensions.