Patent Publication Number: US-2005131316-A1

Title: Guidewire with flexible tip

Description:
FIELD OF THE INVENTION  
      The present invention relates to medical devices. More specifically, the present invention relates to guidewires for placement within a body vessel.  
     BACKGROUND OF THE INVENTION  
      Minimally invasive medical procedures allow medical practitioners to conduct procedures inside a patient&#39;s body with minimal surgical trauma. Such procedures often involve the navigation of an endoluminal device, such as a catheter or other cannula, through a body vessel to a distant point of treatment. For example, a physician can reinforce a cardiac artery by implanting a stent in the artery. The physician can place the stent at the point of treatment by navigating a catheter with a mounted stent through the vasculature. Once the point of treatment is reached, the physician deploys the stent and subsequently retracts the catheter from the point of treatment and eventually from the patient&#39;s body. The entire procedure, therefore, is conducted through a small opening providing access to the vasculature as opposed to direct surgical access to the cardiac artery.  
      In minimally invasive procedures, a guidewire can be used to aid navigation of endoluminal devices through body vessels. Guidewires are typically elongate metal members with a distal tip having a protective means, such as a ball or soft coating, that minimizes trauma to the vessel lining during navigation of bends and other potential obstacles. Guidewires can be initially navigated through a vessel to provide an established route of access for subsequent endoluminal devices, such as catheters, that can be advanced over the placed guidewire. Also, a guidewire/catheter combination can be advanced through the vasculature as a single unit. Furthermore, upon retraction of a catheter, a guidewire can be left in place to provide an established track for subsequent access to a particular point of treatment using the same or another catheter.  
     SUMMARY OF THE INVENTION  
      The present invention provides a guidewire with a flexible tip that axially extends beyond the distal end of the elongate body of the guidewire. A ratio of the length of the flexible tip to the diameter of the main body of the guidewire can be greater than 3:1. Also, the length of the flexible tip can be equal to or greater than the length of a distal tip portion of the elongate member of the guidewire.  
      In one embodiment, a guidewire according to the invention comprises an elongate member having a proximal end, a main body, a distal end, and a taper portion. The main body has a first diameter and the distal end has a second diameter. The taper portion is disposed between the main body and the distal end and defines a taper between the first and second diameters. A coating is disposed on the distal end and comprises a flexible tip. The flexible tip comprises a length axially extending beyond the distal end of the elongate member. The ratio of the length of the flexible tip to the first diameter is greater than 3:1.  
      In another embodiment, a guidewire according to the invention comprises an elongate member having a proximal end, a main body, a distal tip, and a taper portion. The main body has a first diameter and the distal tip has a second diameter. The taper portion is disposed between the main body and the distal tip and defines a taper between the first and second diameters. A coating is disposed on the distal tip and comprises a flexible tip. The flexible tip has a length that axially extends beyond the distal tip. The length of the flexible tip is equal to or greater than the length of the distal tip portion of the elongate member.  
      In another embodiment, a guidewire according to the present invention comprises an elongate member having a proximal end, a main body, a distal tip, and a taper portion. The main body has a first diameter and the distal tip has a second diameter. The taper portion is disposed between the main body and distal tip and defines a taper between the first and second diameters. A coating is disposed on the distal tip and at least a portion of the taper portion. The coating comprises a flexible tip having a length that axially extends beyond the distal tip of the elongate member. The ratio of the length of the flexible tip to the first diameter is greater than 3:1. A radiopaque marker is disposed in the flexible tip and a lubricious coating is disposed on at least a portion of the main body.  
      Additional understanding of the invention can be obtained from the description of exemplary embodiments appearing below and the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a guidewire according to one embodiment of the invention, with portions in cross section.  
       FIG. 2  is a magnified view of the distal end of the guidewire illustrated in  FIG. 1 .  
       FIG. 3  is a magnified view of a distal end of a guidewire according to another embodiment of the invention.  
       FIG. 4  is a side view of a guidewire according to another embodiment of the invention, with portions in cross section.  
       FIG. 5  is a magnified view of the distal end of the guidewire illustrated in  FIG. 4 .  
       FIG. 6  is a magnified view of the distal end of a guidewire according to another embodiment of the invention.  
       FIG. 7  is a side view of a guidewire according to another embodiment of the invention, with portions in cross section.  
       FIG. 8  is a side view of a guidewire according to another embodiment of the invention, with portions in cross section.  
       FIG. 9  is a side view of a guidewire according to another embodiment of the invention, with portions in cross section.  
       FIG. 10  is a sectional view of a guidewire according to another embodiment of the invention.  
       FIG. 11  is a magnified view of the distal end of the guidewire illustrated in  FIG. 10 .  
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION  
      The following provides a detailed description of embodiments of the invention. The embodiments described and illustrated herein are exemplary in nature, and are not intended to limit the scope of the invention in any manner. Rather, the embodiments serve simply as examples to aid in enabling one of ordinary skill in the art to make and use the invention.  
      The present invention provides a guidewire with a flexible tip that axially extends beyond the distal end of the elongate body of the guidewire.  FIGS. 1 and 2  illustrate a guidewire  10  according to one embodiment of the invention. In this embodiment, the guidewire  10  comprises an elongate member  12  that has a proximal end  14 , a main body  16  with a first diameter  18 , and a distal end  20  with a second diameter  22 . A taper portion  24  is disposed between the main body  16  and distal end  20 , and defines a taper  26  between the first  18  and second  22  diameters. A coating  28  is disposed on the distal end  20  of the elongate member  12 . The coating  28  comprises a flexible tip  30  that has a length  32  extending axially beyond the distal end  20  of the elongate member  12 . The coating  28  can be adhered to the elongate member  12  by way of its physical characteristics, an additional adhesive, over-molding techniques, or other suitable manners known in the art.  
      The elongate member  12  can comprise any member suitable for use as a guidewire. The guidewire art contains numerous examples of suitable elongate members, such as unitary wire members, wound wire members, and members comprising one or more wires wound around a mandril. Further, the elongate member  12  can comprise a unitary construction or two or more components arranged together to form a suitable elongate member.  
      The elongate member  12  can be fabricated from any suitable material, and need only be biocompatible or be able to be made biocompatible by techniques such as coating, chemical treatment, and the like. Examples of suitable materials include polymeric materials, such as polyethylenes and other plastics, and metals, such as stainless steel, nitinol, and other shape memory metals.  
      The elongate member  12  includes proximal  14  and distal  20  ends. During a procedure using the guidewire  10 , the proximal end  14  of the elongate member  12  typically remains outside the patient and is used by the practioner to effect navigation of the guidewire  10  through a body vessel. Accordingly, the proximal end  14  may include adaptations and/or structures that aid in handling the guidewire  10 , such as a handle or other gripping structure. The distal end  20  provides the leading end for navigation through a body vessel.  
      The elongate member  12  also includes a main body  16  between the proximal  14  and distal  20  ends. The main body  16  typically comprises the majority of the overall length of the elongate member  12 . The main body  16  has a diameter  18  that may vary or remain constant along the length of the elongate member  12 . The diameter  18  represents the finished diameter of the main body  16  and, therefore, includes any coatings, layers, or other materials placed on the exterior surface of the main body  16  to create the finished guidewire  16 .  
      The diameter  22  of the distal end  20  can be smaller than the diameter  18  of the main body  16 . The embodiment illustrated in  FIGS. 1 and 2  includes a guidewire  10  having a distal end  20  with a diameter  22  that is smaller than a diameter  18  of the main body  16 . With this arrangement, the elongate member  12  can include a taper portion  24  disposed between the main body  16  and the distal end  20 . The taper portion  24  defines a taper  26  between the diameter  18  of the main body  16  and the diameter  22  of the distal end  20 . The taper portion  26  can be integrally formed with the main body  16  and/or distal end  20 , or can be a separately attached member. For example, a frusto-conical member can be attached to an end of a main body portion, thereby providing the distal end and taper portion of an elongate member for use in a guidewire according to the invention. The taper portion  24  provides a portion that accomplishes a reduction in diameter, and may enhance flexibility. The distal end  20  can comprise a rounded tip, as illustrated, or any other suitable configuration, including a pointed tip.  
      A coating  28  is disposed on the distal end  20  of the elongate member  12 . The coating  28  can comprise any suitable coating, and need only be biocompatible or be able to be made biocompatible. Furthermore, the coating must be able to provide the flexible tip as described herein. Suitable materials for the coating  28  include polymeric materials, such as polyurethane and other polymers capable of being flexible at human body temperatures. If a polymeric coating is used, the coating  28  can comprise a single polymer or a blend of one or more polymers. The specific polymer(s) chosen will depend on several factors, including the desired flexibility of the coating  28  and flexible tip  30  (described more fully below) and the material used for the distal end  20  of the elongate member  12 .  
      The coating  28  comprises a flexible tip  30 . The flexible tip  30  is a portion of the coating  28  that axially extends beyond the distal end  20  of the elongate member  12 . Thus, the flexible tip  30  does not include any portion of the elongate member  12 . As best illustrated in  FIG. 2 , the flexible tip  30  has a length  32  that represents the distance by which the tip  30  axially extends beyond the distal end  20  of the elongate member  12 . The length  32  can be defined in comparison to dimensions of the main body  16 . For example, the length  32  can be defined as a particular ratio to the diameter  18  of the main body  16 . When defined in this manner, the ratio of the length  32  to the diameter  18  can be greater than 3:1. Also, the ratio of the length  32  to the diameter  18  can be between 10:1 and 500:1, between 10:1 and 300:1, and between 12:1 and 250:1.  
      The length  32  of the flexible tip  30  can also be defined as a length measurement. The length  32  should be greater than  3  mm for most guidewires, and can be between 3 and 100 mm, between 4 and 80 mm, between 5 and 20 mm, and between 8 and 12 mm. A 10 mm length is a particularly well suited length for a flexible tip on a guidewire for use in some vascular applications.  FIG. 2  illustrates a length  32  of the flexible tip  30  and  FIG. 3  illustrates an alternate length  32 ′ of a flexible tip  30 ′.  
      The specific length chosen for the flexible tip  30  will depend on various factors, and can be optimized based on these factors. For example, the flexible tip  30  provides a flexible end to the guidewire  10 , and may provide flow direction to the guidewire  10 . That is, the flexible tip  30  can lead the guidewire  10  by following the flow of blood or other fluid through the body vessel in which the guidewire  10  is placed, which may aid in navigation into smaller vessels, such as distal arteries. A longer flexible tip  30  may better respond to curves and other turns and/or bifurcations in the vessel than a shorter flexible tip. Also, the length of the flexible tip  30  must not be so excessive as to negatively affect the pushability and/or steerability of the guidewire  10 . Furthermore, the length of the flexible tip  30  can be optimized based on the intended use of the guidewire, such as the typical vessels into which the guidewire  10  will be placed.  
      For example, if a guidewire will be used to traverse a narrow stenosis in the peripheral vasculature, or if a guidewire will be used with large, bulky catheters or other devices, a relatively shorter tip may be desirable. On the other hand, if a guidewire will be used in distal, tortuous vasculature, a relatively longer flexible tip may be desirable. Longer flexible tips may be up to 100 mm or longer and may be associated with guidewires of relatively small diameter, such as guidewires having a diameter of 0.018″. Shorter flexible tips may be as short as 3 mm and may be associated with guidewires of relatively larger diameter, such as guidewires having a diameter of 0.038″.  
      In the embodiment illustrated in  FIG. 1 , the coating  28  is further disposed on part of the taper portion  24  of the elongate member  12 . This may provide additional anchoring of the coating  28  to the elongate member  12 . Also, the coating  28  in this embodiment includes a taper  34  that roughly approximates the taper  26  of the elongate member  12  taper portion  24 .  
       FIGS. 4 and 5  illustrate a guidewire  110  according to another embodiment of the invention. The guidewire  110  of this embodiment is similar to the guidewire  10  illustrated in  FIGS. 1 and 2 , except as detailed below. Thus, the guidewire  110  includes an elongate member  112  having proximal  114  and distal  120  ends. A main body  116  extends between the proximal  114  and distal  120  ends. The main body  116  has a first diameter  118  and the distal end  120  has a second diameter  122 . A taper portion  124  is disposed between the main body  116  and distal end  120  and defines a taper  126  between the first  118  and second  122  diameters. A coating  128  is disposed on the distal end  120  and comprises a flexible tip  130  that has a length  132  that axially extends beyond the distal end  120  of the elongate member  112 .  
      In this embodiment, the elongate member  112  further includes a distal tip portion  121  disposed adjacent the taper portion  124 . The distal tip portion  121  is an elongate tip of substantially uniform diameter  122  and comprises the distal end  120  of the elongate member  112 . The distal tip portion  121  may provide additional rigidity to the distal end of the guidewire  110  and may enhance securement of the coating  128  to the elongate member  112 .  
      In this embodiment, the length  132  of the flexible tip  130  comprises the distance by which the coating  128  axially extends beyond the distal end  120  of the elongate member  112 , which is the end of the distal tip portion  121 . The length  132  of the flexible tip  130  can be defined by the same comparative ratios to the finished diameter  118  of the main body  116  and/or length values as in the embodiment illustrated in  FIG. 1 , described above.  FIG. 6  illustrates an alternate flexible tip  130 ′ having alternate length  132 ′. The distal tip  121  has the same diameter  122  as in the embodiment illustrated in  FIG. 5 .  
       FIG. 7  illustrates a guidewire  210  according to another embodiment of the invention. The guidewire  210  of this embodiment is similar to the guidewire  110  illustrated in  FIG. 4 , except as described below. Thus, the guidewire  210  includes an elongate member  212  having proximal  214  and distal  220  ends. A main body  216  extends between the proximal  214  and distal  220  ends and has a diameter  218 . A distal tip portion  221  is disposed adjacent a taper portion  224 . The distal tip portion  221  comprises an elongate tip of a second, substantially uniform diameter and comprises the distal end  220  of the elongate member  212 . The taper portion  224  is disposed between the main body  216  and the distal end  220  and defines a taper  226  between the first diameter  218  and the diameter of the distal tip portion  221 . A coating  228  is disposed on the distal end  220  and comprises a flexible tip  230  that has a length that axially extends beyond the distal end  220  of the elongate member  212 .  
      In this embodiment, the coating  228  further comprises radiopaque material  236 . The radiopaque material  236  provides radiopacity to the coating  228 , allowing enhanced visualization under fluoroscopy. The radiopaque material  236  can comprise any suitable opacifying agent loaded into the coating  228 , such as bismuth, tantalum, or other suitable agents known in the art. The concentration of the agent in the coating  228  may require adjustment based on the size of the elongate member  212  and/or the coating  228 . For example, guidewires with distal ends of relatively small diameter may require an 80% load of radiopaque material  236  to be adequately visible under fluoroscopy. Larger guidewires, however, may require only a 30% load.  
      A radiopaque marker  238  can be disposed in the flexible tip  230 . The radiopaque marker  238  is a solid member disposed in the flexible tip  230  and spaced from the distal end  220  of the elongate member  212 . Thus, as illustrated in  FIG. 7 , a portion of the coating  228  can be disposed between the radiopaque marker  238  and the distal end  220  of the elongate member  212 . The radiopaque marker  238  can comprise any suitable radiopaque material, such as gold, platinum, or other suitable materials known in the art. The radiopaque marker  238  may provide additional visibility to the flexible tip  230  under fluoroscopy, and can be used in conjunction with or in the absence of radiopaque material  236 . Also, as a solid member, the radiopaque marker  238  provides additional localized weight to the flexible tip  230 , which may enhance the flow direction properties of the flexible tip  230 , as described above. If only the additional localized weight provided by the marker  238  is desired, any suitable solid member can be used. For example, if only additional localized weight is desired in the flexible tip  230 , a solid member that is not radiopaque can be used. In such embodiments, essentially any material that can be placed in the flexible tip  230  can be used, and suitable materials include metals and polymeric materials. Also, the radiopaque marker  238 , or solid member that is not radiopaque, can be disposed around the flexible tip  230 , or in any other suitable arrangement in or on the flexible tip  230 .  
      In this embodiment, a lubricious coating  240  is disposed on at least a portion of the main body  216  of the elongate member  212 . The lubricious coating  240  reduces friction during navigation of the guidewire  210  through a body vessel. A variety of lubricious coatings are known in the guidewire art, and any suitable coating can be used in accordance with the present invention. An example of a suitable coating is ePTFE. The lubricious coating  240  can be disposed on any portion of the main body  212 , and may be disposed over the entire surface of the elongate member  212 . Also, the lubricious coating  240  may be disposed on a portion of the taper portion  224  of the elongate member  212 . For example, the lubricious coating  240  may be disposed on the part  241  of the taper portion  224  that is not covered by the polymer coating  228 .  
      Also, in this embodiment, the coating  228  comprising the flexible tip  230  has a substantially uniform diameter along its length. Thus, in contrast to the embodiments described above, the exterior surface of the coating  228  does not include a taper that roughly approximates the taper  226  of the taper portion  224  of the elongate member  212 . Rather, the exterior surface of the polymer coating  228  is substantially linear.  
       FIG. 8  illustrates a guidewire  310  according to another embodiment of the invention. The guidewire  310  of this embodiment is similar to the guidewire  110  illustrated in  FIG. 4 , except as described below. Thus, the guidewire  310  includes an elongate member  312  having proximal  314  and distal  320  ends. A main body  316  extends between the proximal  314  and distal  320  ends and has a diameter  318 . A distal tip portion  321  is disposed adjacent a taper portion  324 . The distal tip portion  321  comprises an elongate tip of a second, substantially uniform diameter and comprises the distal end  320  of the elongate member  312 . The taper portion  324  is disposed between the main body  316  and the distal end  320  and defines a taper  326  between the first diameter  318  and the diameter of the distal tip portion  321 . A coating  328  is disposed on the distal end  320  and comprises a flexible tip  330  that has a length that axially extends beyond the distal end  320  of the elongate member  312 .  
      In this embodiment, the coating  328  is disposed on the distal end  320 , the taper portion  324 , and at least a portion of the main body  316 . Also, a lubricious coating  340  is disposed on at least a portion of the coating  328 . As illustrated in  FIG. 8 , the lubricious coating  340  can be disposed on the surface of the entire coating  328 .  
      The length  332  of the flexible tip  330  can be defined by the comparative ratios and/or length values as in all previous embodiments described above. Also, in this embodiment, the length  332  of the flexible tip  330  can be defined as being equal to or greater than a length  342  of the distal tip portion  321  of the elongate member  312 .  
       FIG. 9  illustrates a guidewire  410  according to another embodiment of the invention. The guidewire  410  of this embodiment is similar to the guidewire  310  illustrated in  FIG. 8 , except as described below. Thus, the guidewire  410  includes an elongate member  412  having proximal  414  and distal  420  ends. A main body  416  extends between the proximal  414  and distal  420  ends and has a diameter  418 . A distal tip portion  421  is disposed adjacent a taper portion  424 . The distal tip portion  421  comprises an elongate tip of a second, substantially uniform diameter and comprises the distal end  420  of the elongate member  412 . The taper portion  424  is disposed between the main body  416  and the distal end  420  and defines a taper  426  between the first diameter  418  and the diameter of the distal tip portion  421 . A coating  428  is disposed on the distal end  420  and comprises a flexible tip  430  that has a length that axially extends beyond the distal end  420  of the elongate member  412 .  
      In this embodiment, the flexible tip  430  includes a curvilinear portion  450 . The curvilinear portion  450  can define any suitable curve, and the actual curve chosen will depend on at least the application to which the guidewire  410  will be applied. As illustrated in  FIG. 9 , the curvilinear portion  450  can comprise a J-shape. This configuration may be suitable for use of the guidewire  410  in applications that may require a protective atraumatic tip, or a distal end suitable for selection of a vessel at a vessel junction, i.e., a selection tip.  
       FIGS. 10 and 11  illustrate a guidewire  510  according to another embodiment of the invention. In this embodiment, the guidewire  510  comprises an elongate member  512  having proximal  514  and distal  520  ends. A main body  516  extends between the proximal  514  and distal  520  ends and has a diameter  518 . The distal end  520  has a diameter  522  that may be the same as, larger than, or smaller than the diameter  518  of the main body  516 . A coating  528  is disposed on the distal end  520  and at least a portion of the main body  516 . The coating  528  comprises a flexible tip  530 . The flexible tip  530  has a length  532  that axially extends beyond the distal end  520  of the elongate member  512 . The ratio of the length  532  to the diameter  518  of the distal end  520  can be greater than 3:1. Also, the ratio of the length  532  to the diameter  518  can be between 10:1 and 500:1, between 10:1 and 300:1, and between 12:1 and 250:1. The length  532  should be greater than 3 mm for most guidewires, and can be between 3 and 100 mm, between 4 and 80 mm, between 5 and 20 mm, and between 8 and 12 mm. A 10 mm length is a particularly well suited length for a flexible tip on a guidewire for use in some vascular applications.  
      The coating  528  can have a radial thickness along a portion or the entire length of the main body  516  that is greater than the diameter  518  of the main body  516 . This may provide enhanced rigidity to the guidewire  510 .  
      A radiopaque marker  538  is disposed in the flexible tip  530  and spaced from the distal end  520  of the elongate member  512 . A portion of the coating  528  can be disposed between the radiopaque marker  538  and the distal end  520  of the elongate member  512 . The radiopaque marker  538  can be any suitable radiopaque marker, as described above.  
      The foregoing detailed description provides exemplary embodiments of the invention and includes the best mode for practicing the invention. These embodiments are intended only to serve as examples of the invention, and not to limit the scope of the invention in any manner.