Abstract:
A guidewire for intraluminal advancement of a medical device within a patient which has an elongate core member with a flexible body member disposed on a distal section thereof. In one embodiment, the distal section of the elongate core member has at least one flexible segment with at least one pair of opposed tapered or parallel faces. Preferably the flexible segment with the tapered or parallel faces is disposed at the distal end of the elongate core and forms a shapable segment.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to the field of guidewires for advancing intraluminal devices such as stent delivery catheters, balloon dilatation catheters, atherectomy catheters and the like within body lumens.  
           [0002]    In a typical percutaneous coronary procedure, a guiding catheter having a pre-formed distal tip is percutaneously introduced into a patient&#39;s peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced by itself through the guiding catheter until the distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. Then a rail type catheter, such as described in U.S. Pat. No. 5,061,395 (Yock) and the previously discussed McInnes, et al., is mounted onto the proximal portion of the guidewire which extends out of the proximal end of the guiding catheter which is outside of the patient. The catheter is advanced over the guidewire, while the position of the guidewire is fixed, until the operative means on the rail type catheter is disposed within the arterial location where the procedure is to be performed. After the procedure the intravascular device may be withdrawn from the patient over the guidewire or the guidewire repositioned within the coronary anatomy for an additional procedure.  
           [0003]    A guidewire may also be used in conjunction with the delivery of an intracorornary stent. One method and system involves disposing a compressed or otherwise small diameter stent about an expandable member such as a balloon on the distal end of a catheter, advancing the catheter through the patient&#39;s vascular system over a guidewire until the stent is in the desired location within a blood vessel and then expanding the expandable member on the catheter to expand the stent within the blood vessel. The dilated expandable member is then contracted and the catheter withdrawn, leaving the expanded stent within the blood vessel, holding the passageway thereof open. This latter method and system can be used concurrently with balloon angioplasty or subsequent thereto.  
           [0004]    Further details of guidewires, and devices associated therewith for various interventional procedures can be found in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.); U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); and U.S. Pat. No. 5,345,945 (Hodgson, et al.) which are hereby incorporated herein in their entirety by reference thereto.  
           [0005]    Conventional guidewires for angioplasty, stent delivery, atherectomy and other intravascular procedures usually comprise an elongate core member with one or more tapered segments near the distal end thereof. A flexible body member, such as a helical coil or a tubular body of polymeric material, is typically disposed about the distal portion of the core member. A shapable member, which may be the distal extremity of the core member or a separate shapeable ribbon which is secured to the distal extremity of the core member extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding, or an adhesive in the case of polymeric flexible bodies which forms a rounded distal tip. The leading tip is highly flexible and will not damage or perforate the vessel and the portion behind the distal tip is increasingly stiff which better supports a balloon catheter or similar device.  
           [0006]    The shapeable member or ribbon of a typical guidewire is a small diameter wire which has been flattened to a constant transverse profile. Flattening of the shapable member facilitates the shapability of the member, however, a shapable member having a constant transverse profile or flexibility can be subject to prolapse during use. Prolapse occurs when the shapable member gets bent back on itself in a constrained lumen and is difficult to straighten out with proximal manipulation. One method of preventing prolapse or reducing the occurrence thereof is to have increased stiffness at a proximal end of a shapable member. This has been done with incremental steps in the shapable member with thinner more flexible steps distally creating greater flexibility distally. However, the use of incremental steps can cause abrupt changes in flexibility of the shapable member which can be detrimental to smooth tracking and performance of the guidewire. What has been needed is a guidewire with a shapeable member at the distal section that is continuously varied in flexibility and maintains a shapeable character. The present invention satisfies these and other needs.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to a guidewire having an elongate core member with a proximal section and a distal section. The distal section preferably has at least one flexible segment with two or more opposed faces that are parallel or distally tapered in essentially the same or mirror image relationship to each other. The distal section may also have one or more tapered segments which have typical distally decreasing tapers with substantially round transverse cross sections.  
           [0008]    Preferably the flexible segment is disposed at a distal end of the distal section where it can perform the function of a shapeable member. The flexible segment has a length typically ranging from about 1 to about 12 cm, preferably about 2 to about 10 cm, although longer segments may be used. The flexible segment provides a controlled longitudinal variation and transition in flexibility of the core segment. A flexible body member having a proximal end and a distal end is typically disposed about and attached to the distal section of the elongate core member. A flexible body member, such as a helical coil, polymer jacket, or the like, surrounds and covers at least a portion of the distal section of the elongate core member. The proximal end of the helical coil or flexible body typically is secured to the distal section of the elongate core member. Depending on the selected lengths of the helical coil and the flexible segment or shapeable member, the junction of the proximal end of the coil to the core may be at an intermediate position on the distal section or may be at an intermediate position on the flexible segment or anywhere in between.  
           [0009]    In one preferred embodiment of a guidewire having features of the invention, the distal section of the core member has at least one flexible segment with at least two opposed tapered faces tapering distally over the length of the flexible segment to a smaller transverse separation. Optionally, the opposed tapered faces may be mirror images and parallel as well as distally tapered. In addition, the tapered faces may have either a substantially straight or curved longitudinal profile. Other than the flexible segment, the construction of the guidewire is similar to the guidewire discussed above with a flexible body member disposed about at least a portion of the distal section and is secured thereto. The proximal section of the elongate core member is nominally round in cross section and preferably with a constant diameter and said round cross section preferably extends distally to a proximal end of the flexible segment disposed on the distal section of the core. The flexible segment may be disposed anywhere on the distal section, but preferably is disposed at a distal end of the distal section, serving as a shapable member.  
           [0010]    The taper geometry of the flexible segment may be modeled mathematically. Specific taper or face angles or contours may be selected in keeping with the principles and spirit of the invention to achieve optimum performance for specific usage requirements. These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is an elevation view, partially in section, of a guidewire embodying features of the invention.  
         [0012]    [0012]FIG. 2 is an enlarged elevational view of a portion of the distal section of the elongated core member of the guidewire shown in FIG. 1.  
         [0013]    [0013]FIG. 3 is an end view of the embodiment of FIG. 2, shown as viewed from line  3 - 3  in FIG. 2.  
         [0014]    [0014]FIG. 4 is an elevational view of an elongated core member for a guidewire having features of the invention.  
         [0015]    [0015]FIG. 5 is a side elevation view of the embodiment shown in FIG. 4.  
         [0016]    [0016]FIG. 6 is a end view of the embodiment of FIGS. 4 and 5, shown as viewed from line  6 - 6  in FIG. 5.  
         [0017]    [0017]FIG. 6A is a transverse cross sectional view of the flexible segment of FIG. 5 taken at lines  6 A- 6 A.  
         [0018]    [0018]FIG. 7 is an elevational view of a portion of an elongated core member for a guidewire having features of the invention.  
         [0019]    [0019]FIG. 8 is a side elevation view of the embodiment of FIG. 7.  
         [0020]    [0020]FIG. 9 is a end elevation view of the embodiment of FIGS. 7 and 8, shown as viewed from line  9 - 9  in FIG. 8.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    [0021]FIG. 1 is an elevational view of guidewire  10  which embodies features of the invention, and which includes an elongated core member  11  with a proximal core section  12 , a distal core section  13 , and a flexible body member  14  which is fixed to the distal core section. The distal core section  13  has a tapered segment  15 , a flexible segment  16  which is distally contiguous to the tapered segment  15 , a distal end  13   a , and a proximal end  13   b . The distal section  13  may also have more than one tapered segment  15  which have typical distally decreasing tapers with substantially round transverse cross sections. A guidewire having multiple continuous tapered segments in the distal section of the elongate core member is described in U.S. patent application Ser. No. 08/868,764, filed Jun. 4, 1997 (Cornish, et al.) entitled STEERABLE GUIDEWIRE WITH ENHANCED DISTAL SUPPORT, which is hereby incorporated by reference in its entirety.  
         [0022]    The core member  11  may be formed of stainless steel, NiTi alloys or combinations thereof such as described in U.S. Pat. No. 5,341,818 (Abrams et al) which has been incorporated herein. Other materials such as the high strength alloys as described in U.S. Pat. No. 5,636,641 (Fariabi), entitled HIGH STRENGTH MEMBER FOR INTRACORPOREAL USE, which is incorporated herein by reference, may also be used.  
         [0023]    The core member  11  is optionally coated with a lubricious coating such as a fluoropolymer, e.g. TEFLON® available from DuPont, which extends the length of the proximal core section. The distal section  13  is also provided with a lubricous coating, such as a MICROGLIDE™ coating used by the present assignee, Advanced Cardiovascular Systems, Inc. on many of its commercially available guidewires. Hydrophilic coatings may also be employed.  
         [0024]    The length and diameter of guidewire  10  may be varied to suit the particular procedures in which it is to be used and the materials from which it is constructed. The length of the guidewire  10  generally ranges from about 65 cm to about 320 cm, more typically ranging from about 160 cm to about 200 cm, and preferably from about 175 cm to about 190 cm for the coronary anatomy. The guidewire diameter generally ranges from about 0.008 in. to about 0.035 in. (0.203 to 0.889 mm), more typically ranging from about 0.012 in. to about 0.018 in. (0.305 to 0.547 mm), and preferably about 0.014 in. (0.336 mm) for coronary anatomy.  
         [0025]    The flexible segment  16  terminates in a distal end  18 . Flexible body member  14 , preferably a helical coil, surrounds a portion of the distal section of the elongated core  13 , with a distal end  19  of the flexible body member  14  secured to the distal end  18  of the flexible segment  16  by the body of solder  20 . The proximal end  22  of the flexible body member  14  is similarly bonded or secured to the distal core section  13  by a body of solder  23 . Materials and structures other than solder may be used to join the flexible body  14  to the distal core section  13 , and the term “solder body” includes other materials such as braze, epoxy, polymer adhesives, including cyanoacrylates and the like.  
         [0026]    The wire from which the flexible body  14  is made generally has a transverse diameter of about 0.001 to about 0.004 inch, preferably about 0.002 to about 0.003 inch (0.05 mm). Multiple turns of the distal portion of coil may be expanded to provide additional flexibility. The helical coil may have a diameter or transverse dimension that is about the same as the proximal core section  12 . The flexible body member  14  may have a length of about 2 to about 40 cm or more, preferably about 2 to about 10 cm in length. The flexible body member  14  may also be made from a polymer. Polymers suitable for forming a flexible body member  14  can include polyimide, polyethylene, polyurethane, TFE, PTFE, ePTFE and other similar materials. A flexible body member  14  in the form of a helical coil may be formed of a suitable radiopaque material such as platinum or alloys thereof or formed of other material such as stainless steel and coated with a radiopaque material such as gold.  
         [0027]    The flexible segment  16  has a length typically ranging about 1 to about 12 cm, preferably about 2 to about 10 cm, although longer segments may be used. The form of taper of the flexible segment  16  provides a controlled longitudinal variation and transition in flexibility (or degree of stiffness) of the core segment. The flexible segment is contiguous with the core member  11  and is distally disposed on the distal section  13  so as to serve as a shapable member.  
         [0028]    Referring to FIG. 2, the flexible segment  16  of guidewire  10  is shown in more detail. The flexible segment  16  is tapered distally both in height and width and has a generally square cross section defined by a first pair of opposed tapered faces and a second set of opposed tapered faces. The first set of opposed tapered faces consists of a top face  25  and a bottom face  26 , which taper distally together to a smaller transverse separation. The second set of opposed tapered faces consists of a first side face  27  and a second side face  28  which taper distally together to a smaller transverse separation. Each of the tapered faces  25 - 28  are substantially axially coextensive and extend from the transition portion  24  of the distal section  13  to the distal end  18  of the flexible segment  16 . Thus flexible segment  16  tapers to become progressively narrower in both transverse directions as the distal end  18  is approached. This results in a smooth decrease in cross sectional area and stiffness distally. Each of the tapered faces  25 - 28  has a longitudinal contour that is substantially straight. In addition, the top face  25  is a mirror image of the bottom face  26  about the longitudinal axis  17 . The first side face  27  is a mirror image of the second side face  28  about the axis  17 .  
         [0029]    The short transition portion  24  is shaped to provide a generally continuous transition from the circular cross section of the distal end  29  of the tapered segment  15  to the substantially square cross section of the proximal end  30  of the flexible segment  16 . Referring to FIG. 3, the first set of opposed tapered faces  25  and  26  are substantially normal at any given transverse cross section to the second set of opposed tapered faces  27  and  28 . Or in other words, in any transverse cross section of the flexible segment  16 , the lines representing the surfaces of the first set of opposed tapered faces  25  and  26  will be substantially normal to the lines representing the second set of opposed tapered faces  27  and  28 .  
         [0030]    The multiple tapers or faces of the flexible segment  16  may be ground simultaneously or as separate operations. A centerless grinder with profile capabilities may be used to grind the tapers or faces simultaneously. A manual centerless grinding may be employed to create separate tapers or faces in separate operations. Tapers or faces may also be formed by other means such as chemical means, e.g. etching, or laser means.  
         [0031]    [0031]FIGS. 4, 5 and  6  depict an alternative embodiment of a flexible segment  40  wherein one pair of opposed tapered faces taper distally to a smaller transverse separation. This results in a smooth decrease in cross sectional area and stiffness distally over the length of the flexible segment  40 . The flexible segment  40  is preferably integrally formed with a tapered segment  41  of a distal core section  42 . The first opposed tapered face  43  and second opposed tapered face  44  slope distally and incline towards the axis  45  of the segment  40 . The opposed faces  43  and  44  terminate distally at the distal end  46  of the flexible segment  40 . The width of the distal end  46  can be the diameter of the proximal end  47  of the flexible segment  40 . In the embodiment shown, the round cross section of the tapered segment  41  is continued in the flexible segment  40  except to the extent that the material of the core  42  has been removed or shaped in order to form the first and second opposed tapered faces  43  and  44 . Thus, the side surfaces  48  and  49  of the flexible segment  40  may have a curved profile. The longitudinal contours of each of the first and second opposed tapered faces are substantially straight, in addition to being mirror images about longitudinal axis  45 . In FIG. 6A a transverse cross sectional view of the flexible segment  40  taken at lines  6 A- 6 A in FIG. 5 shows the curved profile of the side surfaces  48  and  49 . In addition, the flattened shape of the cross section is indicated by the major transverse dimension  49   a  and the short transverse dimension  49   b  of the flexible segment  40 . In the cross section of FIG. 6A, the major transverse dimension  49   a  is substantially greater than the small transverse dimension  49   b.    
         [0032]    [0032]FIGS. 7, 8 and  9  depict an embodiment of a flexible segment  50  with two pairs of opposed faces which are generally coextensive in an axial direction. The first pair of opposed faces consists of a first tapered face  51  and a second tapered face  52 . The second pair of opposed faces consists of a first parallel face  53  and a second parallel face  54 . The first tapered face  51  and second tapered face  52  taper distally to a smaller transverse separation with respect to each other such that the distance between the first tapered face  51  and the second tapered face  52  is greater at the proximal end  55  of the flexible segment  50  than at the distal end  56  of the flexible segment.  
         [0033]    The first parallel face  53  is substantially parallel to the second parallel face  54  along the length of the flexible segment  50  except at the proximal end  55  of the flexible segment where the first and second parallel faces terminate proximally at the first transition segment  57  and a second transition segment  58 . The optional first and second transition segments  57  and  58  span the difference in transverse dimension from the proximal end  55  of the flexible segment  50  to the distal end  61  of the tapered segment  62  of the distal core section  63 . Although the first and second tapered faces  51  and  52  have substantially straight longitudinal contours, these contours may also be curved. The first and second transition segments  57  and  58  may also be curved so as to create a smooth transition at the proximal end  55  of the flexible segment  50 .  
         [0034]    While particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.