Abstract:
Catheters such as guide catheters can be configured for delivery of devices to vasculature portions such as intracranial spaces while retaining a desired level of flexibility. A catheter having an elongate shaft can include removable support means that can provide column support to the elongate shaft. The elongate shaft can include anchoring means that releasably secure the removable support means. The catheter can be deployed within a patient&#39;s vasculature, followed by deploying the removable support means.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates generally to elongate medical devices and more specifically to catheters. In particular, the invention relates to guide catheters that can include removable structure.  
       BACKGROUND  
       [0002]     Catheters such as guide catheters can be subject to a number of often conflicting performance requirements such as flexibility, strength, minimized exterior diameter, maximized interior diameter, and the like. In particular, often times there is a balance between a need for flexibility and a need for strength or column support. If a catheter is sufficiently flexible to reach and pass through tortuous vasculature, the catheter may lack sufficient column strength to remain in position while, for example, subsequent treatment devices are advanced through the catheter.  
         [0003]     Flexibility versus column strength can be a particular issue in intracranial access, which can require a catheter to pass through the aortic arch prior to making an essentially linear advancement to reach the brain, with again another perhaps tortuous path to a desired treatment site within a patient&#39;s head. Intracranial guide catheters have been configured to provide intracranial access to relatively soft elements, such as microcatheters and guide wires.  
         [0004]     However, accommodating intracranial delivery of therapeutic elements such as stent delivery catheters and other balloon catheters presents a new set of challenges as these devices can be significantly stiffer and, therefore, can exert significantly greater radial forces on a guide catheter. As a result, guide catheters can be subject to backing out of particular vasculature such as the aortic arch and, thus, require repositioning.  
         [0005]     Therefore, a need remains for catheters that are configured for delivering devices such as stent delivery catheters or other balloon catheters to intracranial locations. A need remains for a guide catheter that can provide sufficient column support while retaining a desired level of flexibility.  
       SUMMARY  
       [0006]     The invention is directed to catheters configured for device delivery while retaining a desired level of flexibility. In particular, the invention is directed to catheters that provide a desired level of flexibility for advancing the catheter into a patient&#39;s vasculature yet can be provided with sufficient column support once the catheter has reached a desired position within the vasculature. If desired, the column support can be removed prior to removal of the catheter.  
         [0007]     Accordingly, an illustrative embodiment of the invention can be found in a catheter that has an elongate shaft having a proximal region, a distal region, and an exterior surface extending therebetween. The catheter also includes removable support means for providing column support to the elongate shaft. The removable support means is disposed over a portion of the exterior surface of the elongate shaft.  
         [0008]     Another illustrative embodiment of the invention can be found in a modular guide catheter that has an elongate shaft having a proximal region, a distal region and an exterior surface. A lumen extends from the proximal region to the distal region of the elongate shaft. The modular guide catheter includes a plurality of support tracks that are disposed on the external surface of the elongate shaft and that are generally axially aligned with the elongate shaft. The modular guide catheter also includes a plurality of support ribs that are configured to be removably disposed over the plurality of support tracks.  
         [0009]     Another illustrative embodiment of the invention can be found in a method of deploying a catheter within a patient&#39;s vasculature. The catheter includes an elongate shaft having a proximal end, a distal end, an exterior surface extending therebetween and a plurality of support tracks axially disposed over the exterior surface. The catheter is advanced through the vasculature until the distal end of the elongate shaft reaches a desired position within the vasculature. One or more support ribs are disposed over one or more of the plurality of support tracks and are advanced over one or more of the plurality of support tracks to a position proximal of the distal end of the elongate shaft. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0010]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0011]      FIG. 1  is a side elevation view of an intravascular catheter in accordance with an embodiment of the invention;  
         [0012]      FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ;  
         [0013]      FIG. 3  is a closer view of a portion of the intravascular catheter of  FIG. 1 ;  
         [0014]      FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 3 ;  
         [0015]      FIG. 5  is a cross-sectional view of an intravascular catheter in accordance with an embodiment of the invention;  
         [0016]      FIG. 6  is a cross-sectional view of an intravascular catheter in accordance with an embodiment of the invention;  
         [0017]      FIG. 7  is a cross-sectional view of an intravascular catheter in accordance with an embodiment of the invention;  
         [0018]      FIG. 8  is a perspective view of a support rib in accordance with an embodiment of the invention;  
         [0019]      FIG. 9  is a cross-sectional view taken along line  9 - 9  of  FIG. 8 ;  
         [0020]      FIG. 10  is a perspective view of a portion of the intravascular catheter of  FIG. 3 , including the support ribs as shown in  FIG. 8 ;  
         [0021]      FIG. 11  is a cross-sectional view taken along line  11 - 11  of  FIG. 10 ;  
         [0022]      FIG. 12  is a view of  FIG. 5 , with the addition of an external support sheath in accordance with an embodiment of the invention;  
         [0023]      FIG. 13  is a schematic view of the intravascular catheter of  FIG. 3 , positioned through an introducer sheath within a patient&#39;s vasculature;  
         [0024]      FIG. 14  is a schematic view of the proximal portion of the introducer sheath of  FIG. 11 , showing initial placement of the support ribs of  FIG. 8 ;  
         [0025]      FIG. 15  is a schematic view of the intravascular catheter of  FIG. 13 , with the support ribs advanced fully into position;  
         [0026]      FIG. 16  is a schematic view of the intravascular catheter of  FIG. 15 , with the addition of a balloon catheter positioned proximate a lesion; and  
         [0027]      FIG. 17  is a schematic view of the intravascular catheter of  FIG. 16 , showing the balloon catheter with its balloon in an inflated position.  
     
    
     DETAILED DESCRIPTION  
       [0028]     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.  
         [0029]     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.  
         [0030]     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).  
         [0031]     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.  
         [0032]     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The drawings, which are not necessarily to scale, depict illustrative embodiments of the claimed invention.  
         [0033]      FIG. 1  is a plan view of a catheter  10  in accordance with an embodiment of the invention. The catheter  10  can be one of a variety of different catheters, but is preferably an intravascular catheter. Examples of intravascular catheters include balloon catheters, atherectomy catheters, drug delivery catheters, diagnostic catheters and guide catheters. As illustrated,  FIG. 1  portrays a guide catheter, but the invention is not limited to such. Except as described herein, the intravascular catheter  10  can be manufactured using conventional techniques and materials.  
         [0034]     The intravascular catheter  10  can be sized in accordance with its intended use. The catheter  10  can have a length that is in the range of about 50 centimeters to about 100 centimeters and can have a diameter that is in the range of about 4 F (French) to about 9 F.  
         [0035]     In the illustrated embodiment, the intravascular catheter  10  includes an elongate shaft  12  that has a proximal region  14 , a distal region  16  and a distal end  18 . A hub and strain relief assembly  20  can be connected to the proximal region  14  of the elongate shaft  12 . The hub and strain relief assembly  20  includes a main body portion  22 , a pair of flanges  24  designed to improve gripping, and a strain relief  26  that is intended to reduce kinking. The hub and strain relief assembly  20  can be of conventional design and can be attached using conventional techniques.  
         [0036]      FIG. 2  is a cross-sectional view of the elongate shaft  12 , taken along line  2 - 2  of  FIG. 1 . The elongate shaft  12  includes an outer layer  28  and an inner layer  30 . Each of the outer layer  28  and the inner layer  30  can extend from the proximal region  14  of the elongate shaft  12  to the distal region  16  of the elongate shaft  12 . The inner layer  30  defines a lumen  32  that extends through the elongate shaft  12 .  
         [0037]     In some embodiments, the elongate shaft  12  can optionally include a reinforcing braid or ribbon layer to increase particular properties such as kink resistance. If a reinforcing braid or ribbon layer is included, it can be positioned between the outer layer  28  and the inner layer  30 . The optional reinforcing braid or ribbon layer can be provided in a configuration that provides adequate kink resistance without substantially increasing the overall profile of the elongate shaft  12 , as the elongate shaft  12  can be provided with other means of column support, as will be discussed in greater detail hereinafter.  
         [0038]     In some embodiments (not illustrated), the elongate shaft  12  can include one or more shaft segments having varying degrees of flexibility. For example, the elongate shaft  12  can include a proximal segment, an intermediate segment and a distal segment. In some embodiments, the elongate shaft  12  can also include a distal tip segment that can be formed from a softer, more flexible polymer. The elongate shaft  12  can include more than three segments, or the elongate shaft  12  can include fewer than three segments.  
         [0039]     If the elongate shaft  12  has, for example, three segments such as a proximal segment, an intermediate segment and a distal segment, each segment can include an inner layer  30  that is the same for each segment and an outer layer that becomes increasingly more flexible with proximity to the distal end  18  of the elongate shaft  12 . For example, the proximal segment can have an outer layer that is formed from a polymer having a hardness of 72 D (Durometer), the intermediate segment can have an outer layer that is formed from a polymer having a hardness of 68 D and the distal segment can be formed from a polymer having a hardness of 46 D.  
         [0040]     If the elongate shaft  12  has three segments, each of the segments can be sized in accordance with the intended function of the resulting catheter  10 . For example, the proximal segment can have a length of about 35 inches, the intermediate segment can have a length that is in the range of about 2 inches to about 3 inches, and the distal segment can have a length that is in the range of about 1 inch to about 1.25 inches.  
         [0041]     The inner layer  30  can be a uniform material and can define a lumen  32  that can run the entire length of the elongate shaft  12  and that is in fluid communication with a lumen (not illustrated) extending through the hub assembly  20 . The lumen  32  defined by the inner layer  30  can provide passage to a variety of different medical devices, and thus the inner layer  30  can include, be formed from or coated with a lubricious material to reduce friction within the lumen  32 . An exemplary material is polytetrafluoroethylene (PTFE), better known as TEFLON®. The inner layer  30  can be dimensioned to define a lumen  32  having an appropriate inner diameter to accommodate its intended use. In some embodiments, the inner layer  30  can define a lumen  32  having a diameter of about 0.058 inches and the inner layer  30  can have a wall thickness of about 0.001 inches.  
         [0042]     The outer layer  28  can be formed from any suitable polymer that will provide the desired strength, flexibility or other desired characteristics. Polymers with low durometer or hardness can provide increased flexibility, while polymers with high durometer or hardness can provide increased stiffness. In some embodiments, the polymer material used is a thermoplastic polymer material. Some examples of some suitable materials include polyurethane, elastomeric polyamides, block polyamide/ethers (such as PEBAX®), silicones, and co-polymers. The outer layer  28  can be a single polymer, multiple layers, or a blend of polymers. By employing careful selection of materials and processing techniques, thermoplastic, solvent soluble, and thermosetting variants of these materials can be employed to achieve the desired results.  
         [0043]     In particular embodiments, a thermoplastic polymer such as a co-polyester thermoplastic elastomer such as that available commercially under the ARNITEL® name can be used. The outer layer  28  can have an inner diameter that is about equal to the outer diameter of the inner layer  30 .  
         [0044]     In some embodiments, the outer layer  28  can have an inner diameter in the range of about 0.0600 inches to about 0.0618 inches and an outer diameter in the range of about 0.0675 inches to about 0.0690 inches. Part or all of the outer layer  28  can include materials added to increase the radiopacity of the outer layer  28 , such as 50% bismuth subcarbonate.  
         [0045]     Turning to  FIG. 3 , a portion of elongate shaft  12  is illustrated in greater detail. In particular, elongate shaft  12  includes several axially aligned support tracks  34  that extend from the proximal region  14  of the elongate shaft  12  to the distal region  16  of the elongate shaft  12 . A support track  34  can be considered to be generally axially aligned with the elongate shaft  12  if the support track  34  is generally parallel with a long axis of the elongate shaft  12 . In some embodiments, the support tracks  34  extend distally to a position that is proximal of the distal end  18 , thereby not interfering with the flexibility of the distal end  18 . The function of the support tracks  34  will be discussed in greater detail hereinafter.  
         [0046]      FIG. 4 , which is a cross-sectional view taken along line  4 - 4  of  FIG. 3 , illustrates a particular profile of the support tracks  34  as well as a particular configuration employing four support tracks  34 . As illustrated, the support tracks  34  are formed independently of the elongate shaft  12  and are subsequently attached to the outer surface  36  of the elongate shaft  12 . In other embodiments, the support tracks  34  can be co-extruded with the elongate shaft  12 .  
         [0047]     The support tracks  34  can be formed from any suitable polymeric material. Examples of suitable polymeric materials include polyolefins, polymers that have been surface-treated to provide reduced friction, and fluoropolymers such as TEFLON®. The support tracks  34  can be formed having any suitable dimensions.  
         [0048]     In some embodiments, each of the support tracks  34  have an overall length that is about the length of the catheter  10 . In some embodiments, each of the support tracks  34  can have a length that is somewhat less than the length of the catheter  10 . Each of the support tracks  34  can have a width that is in the range of about 0.004 inches to about 0.010 inches and a total depth relative to the outer surface  36  of the elongate shaft  12  that is in the range of about 0.006 inches to about 0.017 inches.  
         [0049]      FIG. 4  shows an embodiment in which a total of four support tracks  34  are equidistantly radially spaced about the elongate shaft  12 . The support tracks  34  can be spaced about ninety degrees apart. In some embodiments, the support tracks  34  do not have to be equidistantly spaced. In such embodiments, there can be flexibility or curvability advantages to grouping the support tracks  34  along one side of the elongate shaft  12 .  
         [0050]     In other embodiments, either less than four or more than four support tracks  34  can be used, as illustrated, for example, in  FIGS. 6 and 7 . In  FIG. 6 , a total of three support tracks  34  have been secured to the exterior surface  36  of the elongate shaft  12 . As shown, the support tracks  34  are equally spaced about 120 degrees apart. In  FIG. 7 , a total of eight support tracks  34  are spaced about the outer surface  36  of the elongate shaft  12 . In this embodiment, the support tracks  34  can be spaced about forty-five degrees apart. In other embodiments, the support tracks  34  do not have to be equidistantly spaced. In other embodiments, there can be a total of one, two, three, four, five, six, seven, eight or more support tracks  34  spaced about the outer surface  36  of the elongate shaft  12 .  
         [0051]     In each of these embodiments, the support tracks  34  can be formed separately and then attached to the outer surface  36  of the elongate shaft  12 . In some embodiments, the support tracks  34  can be heat bonded to the exterior surface  36  of the elongate shaft  12 . In some embodiments, the support tracks  34  can be adhesively attached to the exterior surface  36  of the elongate shaft  12  using any suitable adhesive, such as a cyanoacrylate or an epoxy.  
         [0052]      FIG. 5  illustrates another embodiment in which a catheter shaft has an inner layer  38  defining a lumen  40 . The inner layer  38  can be constructed and dimensioned similar to that discussed above with respect to the inner layer  30 . The catheter shaft also has an outer layer  42  that can be constructed from any suitable polymer, as discussed previously with respect to the outer layer  28 . However, in the illustrated embodiment, the outer layer  42  includes several support tracks  44  that are integrally formed with the outer layer  42 . The outer layer  42  can be extruded or otherwise formed to include the support tracks  44 .  
         [0053]     In  FIG. 5 , the support tracks  44  have a substantially semicircular profile.  FIGS. 4, 6  and  7 , however, show an embodiment in which the support tracks  34  have an ovoid cross-sectional profile having a minor dimension that is perpendicular to the exterior surface of the elongate surface and a major dimension that is perpendicular to the minor dimension. The major dimension can vary as a function of distance from the exterior surface of the elongate shaft  12 , with the major dimension being minimized at a position proximate the exterior surface  36  of the elongate shaft  12  and maximized at a position radially displaced from the exterior surface  36  a distance equal to or less than the minor dimension.  
         [0054]     The support tracks  34  as described herein are configured to complement a support rib  46  as illustrated, for example, in  FIG. 8 .  FIG. 8  is a perspective view of a support rib  46  that has a distal region  48 , a distal end  50  and a proximal region  52 . The support rib  46  has an outer surface  54  and an inner surface  56 . A comparison of the inner surface  56  to the support tracks  34  as previously described illustrates that the inner surface  56  of the support rib  46  is complementary to the cross-sectional profile of the support tracks  34 .  
         [0055]      FIG. 9  is a cross-sectional view of the support rib  46 , taken along the line  9 - 9  of  FIG. 8 . The inner surface  56  can be seen to have a minor dimension d 1  that is perpendicular to a long axis of the support rib  46  and a major dimension d 2  that is perpendicular to the minor dimension d 1 . As discussed above with respect to the support track  34 , the major dimension can vary as a function of distance from the exterior surface of the elongate shaft  12 . As a result of the complementary profiles of the inner surface  56  of the support rib  46  and the outer surface of the support track  34 , axial movement of the support rib  46  with respect to the support track  34  is permitted, while relative radial movement is restricted.  
         [0056]      FIG. 10  illustrates a portion of the elongate shaft  12  in which several support ribs  46  have been positioned over the support tracks  34 .  FIG. 11  is a cross-sectional view taken along line  11 - 11  of  FIG. 10 . This view is essentially the same as  FIG. 4 , with the addition of four support ribs  46 , with one support rib  46  positioned over each of the four support tracks  34 .  
         [0057]     The support ribs  46  can be made of any suitable polymeric material. In some embodiments, the support ribs  46  can be made of a suitable polymeric material having a low coefficient of friction. Examples of suitable polymeric materials include fluorinated polyethylenes such as polytetrafluoroethylene. The support ribs  46  can be formed to have any suitable dimensions. The support ribs  46  can be about the same length as the catheter  10 , or the support ribs  46  can be longer than the catheter  10  in order to provide handling advantages.  
         [0058]     In some embodiments, the support ribs  46  can have an overall length that is in the range of about 80 centimeters to about 150 centimeters. The support ribs  46  can have an overall diameter that ranges from about 0.010 inches to about 0.020 inches. The dimensions d 1  and d 2  can range from about 0.004 inches to about 0.008 inches and from about 0.006 inches to about 0.015 inches, respectively.  
         [0059]     In some embodiments, a variety of support ribs  46  can be provided, each having a different diameter. If a greater level of column support is desired, a physician or other professional can use one or more support ribs  46  that have a larger diameter and, thus, can provide a greater level of support. If less column support is needed, or if the patient has a relatively constricted vasculature, support ribs  46  having a smaller diameter can be used. In some embodiments, a physician or other professional can use a greater number of support ribs  46  or a lesser number of support ribs  46 . For example, if the elongate shaft  12  includes four support tracks  34 , the physician has the option to use no support ribs  46 , one support rib  46 , two, three or even four support ribs  46 , depending on the desired level of support.  
         [0060]     It should be noted that the support ribs  46  are not limited to the inner surface  56  profile illustrated. In some embodiments, the inner surface  56  can have a rectangular profile, with a relatively reduced dimension perpendicular to the long axis of the support rib  46  and a relatively greater dimension perpendicular to the relatively reduced dimension. In other embodiments, the inner surface  56  can have any other profile that permits axial movement of the support rib  46  with respect to the support track  34 , while restricting or eliminating relative radial movement.  
         [0061]      FIG. 12  illustrates a particular embodiment of the invention employing a support sheath  47 , rather than the distinct support ribs  46  previously discussed. The support sheath  47  can be sized to have an inner diameter that is approximately the same as the outer diameter of the outer layer  42 , including the support tracks  44 . The support sheath  47  can have an inner diameter that is slightly larger than the aforementioned outer diameter, in order to reduce friction in advancing the support sheath  47 . The support sheath  47  also can be used in conjunction with the ovoid-shaped support tracks  34  as illustrated in the other Figures.  
         [0062]     The support sheath  47  can be formed from any suitable polymeric material, such as a polyolefin. In some embodiments, the inner surface of the support sheath  47  can be formed from or coated with a material having a low coefficient of friction. Polytetrafluoroethylene is an exemplary material.  
         [0063]      FIGS. 13-17  demonstrate an intended use of the catheter  10 . In  FIG. 13 , an introducer sheath  48  having a distal end  70  and a proximal end  72  has been extended through a patient&#39;s tissue  74  into the patient&#39;s vasculature  76  as is well known in the art. The catheter  10  has been inserted into the proximal end  72  of the introducer sheath  48  and has been advanced to a position near a desired treatment site, such as a lesion  58 . When introduced, the catheter  10  includes the aforementioned support tracks  34 , but does not include the support ribs  46 .  
         [0064]     Once the catheter  10  has been appropriately positioned, the support ribs  46  can be advanced over the support tracks  34  to provide a desired level of column support prior to introducing any treatment devices through the catheter  10 .  FIG. 14  illustrates the proximal end  72  of the introducer sheath  48 . The support ribs  46  are configured such that they can be slid axially over the support tracks  34 . Once the distal ends  50  of each support rib  46  is started over the corresponding support track  34 , the support ribs  46  can be advanced until they reach the distal end  60  of the support tracks  34 .  FIG. 15  shows the catheter  10  with the support ribs  46  fully advanced over the support tracks  34 .  
         [0065]     At this point, the catheter  10  is configured for passage of a treatment device such as a balloon catheter, stent delivery catheter, atherectomy device or the like. The addition of the support ribs  46  provide the catheter  10  with additional column support.  FIG. 16  illustrates the catheter  10  including the support ribs  46  positioned within the patient&#39;s vasculature  76 . In the illustrated embodiment, a balloon catheter  62  having a proximal region  64  and a distal region  66  has been positioned within the lumen  32  extending through the catheter  10 .  
         [0066]     The proximal region  64  of the balloon catheter  62  extends proximally from the patient so that the balloon catheter  62  can be controlled as is known in the art. The distal region  66  is positioned distal of the distal end  18  of the catheter  10  such that it is proximate a treatment region such as the lesion  58 . The distal region  66  of the balloon catheter  62  includes an inflatable balloon  68 . As illustrated in  FIG. 17 , the inflatable balloon  68  can be inflated to compress the lesion  58 .  
         [0067]     While not explicitly illustrated, subsequent treatment can include atherectomy, should the lesion  58  not be sufficiently compressed. Other possible subsequent treatments include compressing the lesion  58  with a different diameter inflatable balloon or positioning and deploying a stent. Once the physician has determined that no subsequent treatments are necessary, the support ribs  46  can be withdrawn proximally while the catheter  10  remains within the patient&#39;s vasculature  56 . Alternatively, the catheter  10  can be withdrawn proximally from the patient while the support ribs  46  remain in position on the support tracks  34 .  
         [0068]     In some embodiments, part or all of the catheter  10  can include a lubricious coating. Lubricious coatings can improve steerability and improve lesion crossing capability. Examples of suitable lubricious polymers include hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers can be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. In some embodiments, a distal portion of the catheter can be coated with a hydrophilic polymer, while the more proximal portions can be coated with a fluoropolymer.  
         [0069]     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.