Abstract:
An embolic protection device provides a filter for removing emboli from a fluid flowing in a vessel of a patient. The filter is mounted on an elongated tubular member that extends along a substantial distal portion of a core guidewire used to place the filter in the appropriate position within the vessel of the patient. The tubular member provides a way to permit rotation of the core guidewire independent of rotation of the filter while also reducing the friction between the core guidewire and the delivery sheath. Improved torque response result. The tubular member may be one or more pieces that may be either coil wire tube or polymeric tubing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an embolic protection device for use in percutaneous procedures and, more particularly, to an improved embolic protection device having a filter mounted on a rotatable tubular member for filtering bodily fluids flowing through a vessel of a patient. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various surgical and intravenous treatments have been developed for treating and/or removing obstructions such as plaque in stenosed regions of vessels of a patient. In balloon angioplasty, a balloon placed on the distal end of a catheter is inflated, usually with a fluid, in order to dilate the stenosed region of the vessel thereby improving fluid flow. In addition a stent may be placed in the stenosed region of the vessel in order to reduce the occurrence and severity of restenosis of the vessel. In an atherectomy or thrombectomy, a rotating blade or other similar cutting device can be used to remove plaque in a stenosed region. Surgery may also be used to remove plaque and improve fluid flow in the vessel. All of these treatments result in the production of small particles of plaque or other materials resulting in emboli that can travel in the direction of fluid flow in the vessel and block smaller vessels downstream of the stenosis resulting in stroke, tissue damage or other problems. 
         [0003]    In order to prevent such an occurrence various embolic protection devices have been suggested that place a filter distal to the stenosed region before and/or during the angioplasty, stenting, atherectomy or other emboli producing procedure. One type of filter is a woven wire mesh filter. Another type of filter is a polymeric material with filter pores placed on or around a filter frame often made of a self-expanding shape-memory metal such as a nickel-titanium alloy known as nitinol. These filter elements are mounted on the distal end of a guidewire or other elongated member which is used to place the filter into the vessel of the body through an external opening in the body containing the vessel. In some systems a guidewire is first inserted into the lumen of the vessel and is directed past a lesion or other are of interest. After insertion of the guidewire a filter element is pushed along the wire past the lesion or other area of interest where it is deployed. For example, U.S. Pat. No. 6,179,859 issued to Bates et al. and entitled “Emboli Filtration System and Method of Use” describes a filter that is restrained in a delivery sheath until it is placed in the vessel. 
         [0004]    In another type of embolic protection system the guidewire and filter element are simultaneously inserted into the lumen of the vessel and the filter element is directed past the lesion or other area of interest where it is deployed. For example, in U.S. Pat. No, 6,468,291 issued to Bates et al. and entitled “Emboli Filtration System Having Integral Strut Arrangement and Methods of Use” such an embolic protection device is disclosed. 
         [0005]    Filter elements are usually mounted on one or more collars either at the distal end, the proximal end or both. These collars are then either fixed to the guidewire or are allowed to travel between one or more stops placed on the guidewire to allow longitudinal movement of the filter basket in relation to the guidewire. The proximal and distal collars of the filter basket may be allowed to rotate on the guidewire to provide rotational movement of the basket relative to the guidewire. 
         [0006]    In such embolic protection devices when the guidewire, particularly a guidewire with an embolic protection device, is tracking through a tortuous artery, the guidewire and/or the delivery sheath restraining the embolic protection device is pushed against the vessel wall causing friction between the vessel wall and the device. If a full-length delivery sheath is used, the delivery sheath pushes against the vessel wall which would cause friction between the delivery sheath and the internal guidewire. This friction reduces the torque response of the guidewire. The torque response is defined here as the number of degrees rotated on the proximal end of the wire and the response on the distal end of the wire measured by the number of degrees the distal end of the wire rotates. If this friction were reduced, then the response of the torque response would be improved. Therefore, it would be desirable to have an embolic protection device that would enable the user to accurately navigate the embolic protection device through tortuous arteries and other vessels and provide improved torque response. 
         [0007]    It is also desirable to provide an embolic protection device that allows the guidewire to be rotated independent of the basket. Compared with the distal end of the typical guidewire which is approximately 1.1 Fr in size, the profile of the basket is relatively much larger at around 3-4 Fr for a 6.0 mm basket. When the proximal end of the guidewire is rotated, it takes a relatively large amount of energy to rotate the distal end of the basket. This results in a delay in the response of the distal end when the torque is applied on the proximal end, which is undesirable. In some instances, the distal end does not rotate when the proximal end is rotated thereby storing the energy over the length of the wire. As additional torque is applied, the energy exceeds the frictional forces necessary to start rotating the basket at which time the basket/guide wire “whips” (defined here as uncontrolled rotation of the distal end of the basket/guide wire). This again is undesirable since the physician is unable to control the location of the guide wire tip to guide the tip of the guidewire into a vessel. By having the guide wire move independent of the basket, the phenomenon of guide wire tip “whip” can be significantly reduced. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention generally relates to an embolic protection device for capture and removal of emboli from a fluid flowing in a vessel. More particularly, the invention relates to the distal end of the guidewire on which the filter element of such a device is placed. In the present invention a portion of the distal section of the central guidewire or guidewire core is covered by a tubular member that is free to rotate around the guidewire core. The tubular member may be a coil wire tube made of multiple strands of wire that is wound to form a tubular section. By putting such a tubular member or “sleeve” on the guidewire core that is not attached to the guidewire core itself, the sleeve would push against the tortuous vessel wall while letting the wire rotate freely inside the tubular member. 
         [0009]    The present invention results in increased torque response of the guidewire and an improved ability to navigate the guidewire through tortuous vessels. Independent longitudinal movement of the basket with respect to the guidewire means that small movements of the guidewire will not result in the displacement of the basket. The distal section of the wire is well supported by the tubular member thereby preventing kinking of the wire. The tubular member gives more stiffness compared with a polymeric sleeve but yet flexible to track through tortuous vessels and provides additional support to reduce the occurrence of wire prolapse when tracking a stent deployment system over the guidewire. 
         [0010]    The length of the tubular member should be substantially the same as the length of the flexible distal section of the guidewire core. Not only is the filter basket independent of the guidewire, but also a substantial portion of the distal end of the device including the filter basket is independent of the guidewire core. 
         [0011]    Thus, the present invention is directed to an embolic protection device for filtering emboli in a fluid stream of a vessel of a patient comprising a guidewire core having a proximal end and a distal end and a distal portion extending a first distance from a point near the distal end, a tubular member rotatably mounted about substantially all of the distal portion of the guidewire core, said tubular member having a distal end and a proximal end and a filter fixedly mounted near the distal end of the tubular member. A tubular member is mounted along the first distance of the guidewire core, which extends approximately 10-40 centimeters for a 190 centimeter guidewire. More preferably the length of the tubular member at the distal portion should be between 15 and 35 centimeters for a 190 centimeter guidewire. 
         [0012]    The tubular member can be a coil wire tube or a polymeric tube. The embolic protection device may have a filter with a proximal collar and a distal collar to which one or more proximal and distal strut are attached and the tubular member terminates under the proximate collar of the filter. 
         [0013]    Alternatively, a second tubular member could extend from the proximal collar of the filter to distal collar of the filter. The filter can be of many types include a filter membrane on a filter frame or a wire mesh filter. The filter membrane could be polymeric, thin film or any other known type of filtering material. The filter may be self-actuating or actuated by a number of means including, but not limited to, mechanical compression, inflation members. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is an elevational view of a first embodiment of an embolic protection device in accordance with the present invention. 
           [0015]      FIG. 2A  is a perspective view of the embolic protection device of  FIG. 1  in accordance with the present invention. 
           [0016]      FIG. 2B  is a sectional perspective view of the embolic protection device of  FIG. 1 . 
           [0017]      FIG. 2C  is a sectional perspective view of the distal end of the embolic protection device of  FIG. 1 . 
           [0018]      FIG. 2D  is a sectional perspective view of the proximal end of the embolic protection device of  FIG. 1 . 
           [0019]      FIG. 3A  is a perspective view of another embodiment of an embolic protection device in accordance with the present invention. 
           [0020]      FIG. 3B  is a sectional view of the embolic protection device of  FIG. 3A . 
           [0021]      FIG. 3C  is a sectional view of the distal end of the embolic protection device of  FIG. 3A . 
           [0022]      FIG. 3D  is a sectional view of the proximal end of the embolic protection device of  FIG. 3A . 
           [0023]      FIG. 3E  is a perspective view of the filter basket portion of the embolic protection device of  FIG. 3A . 
           [0024]      FIG. 4A  is a perspective view of a further embodiment of an embolic protection device in accordance with the present invention. 
           [0025]      FIG. 4B  is a sectional perspective view of the embolic protection device of  FIG. 4A . 
           [0026]      FIG. 4C  is a sectional perspective view of the distal end of the embolic protection device of  FIG. 4A . 
           [0027]      FIG. 4D  is a sectional perspective view of the proximal end of the embolic protection device of  FIG. 4A . 
           [0028]      FIG. 5  is a cross-sectional view of an embodiment of a filter system in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Referring to  FIG. 1 , embolic protection device  100  comprises a guidewire core  102  having a proximal end  104  and a distal end  106 . Guidewire core  102  is of sufficient length to enable the user of the embolic protection device to route the device to a position in the lumen of a vessel where embolic protection is desired, such as distal to an area of plaque for which an angioplasty procedure is to be used to open the vessel. Typical lengths, y, of the guidewire core  102  are between 150 to 200 centimeter for rapid-exchange systems and between 280 and 330 cm over-the-wire systems but other lengths could be used depending on the application. Guidewire core  102  is metal, preferably stainless steel or another type of non-reactive metal or metal alloy with or without a lubricous coating. The types of lubricious coatings that can be applied to guidewire core  102  include Polytetrafluoroethylene (“PTFE”) coatings, silicone coatings and hydrophilic coatings. 
         [0030]    A tubular member  110  is placed over a portion of guidewire core  102  near its distal end  106 . Tubular member  110  is a polymeric tube or coil wire tube. In a preferred embodiment a coil wire tube from Asahi Intec Co., Ltd. is used. Tubular member  110  has a diameter slightly larger than the diameter of the core guidewire  102  at the distal end. The tolerance between the guidewire core  102  and the tubular member  110  is preferably approximately 0.001″ but could be 0.0005 or greater. The tubular member  110  can also be coated with a lubricious coating, such as PTFE, internally and/or externally if desired. 
         [0031]    For a tubular member  110  that is a coil wire tube the ends are preferably soldered to prevent the wire from unraveling. Also, the ends of the tubing can be ground down a small amount if necessary to approximately 50% of the original wall thickness. 
         [0032]    Tubular member  110  may also be composed of a polymer polymeric blend or a polymer fabric. This would give the same torque characteristics, but would results in less stiffness of the distal end. Polymers that could be used for tubular member  110  include PEEK™ polymer from Victrex plc, polyamide, polyurethane, nylon PTFE and polyethylene, among others. VICTREX PEEK polymer, is a repeat unit that comprises of oxy-1, 4-phenylenoeoxy-1, 4-phenylene-carbonyl-1, 4-phenylene, PEEK is a linear aromatic polymer that is semi-crystalline. 
         [0033]    Tubular member  110  floats freely on the core guidewire  102  and is not attached to the core guidewire at any point along its length. Tubular member  110  is of a length, x, that is between approximately 10 and 40 centimeters for a rapid exchange system that would be between 150 to 200 centimeters in length. Preferably tubular member should have a length between 15 and 35 centimeters for such a rapid exchange system. Tubular member  110  should have a length between approximately 15 and 35 centimeters for an over-the-wire system that would be between approximately 280 and 330 centimeters in length. The important attribute of the present invention is that the tubular member  110  extend not only under the proximal end of filter  120  but that it extends a substantial distance proximal the filter  120 . Preferably tubular member  110  extends at least approximately 15 centimeters along the guidewire core  102  in the proximal direction. Too long of a tubular member will unnecessarily add to the cost of the device without providing significant added benefit. Additionally, a significantly longer tubular member  110  will result in reduced pushability. 
         [0034]    A longitudinal motion limiter  140  is a polymer sleeve or other motion limiting device attached to the core guidewire  102  to prevent migration of the tubular member  110  toward the proximal end of the core guidewire  102 . Attachment of the polymer sleeve may be by any appropriate bonding means. Alternatively, core guidewire may be tapered at this point to transition to a larger diameter at the proximal end of the distal portion in order to prevent such migration. 
         [0035]    Filter  120  in  FIG. 1  is depicted as having a filter frame  128  having a plurality of proximal struts  122  connected at the proximal end to proximal collar  130  and at the distal end to apposition member  124 . The number of proximal struts is not critical to the invention, but preferably there are at least two proximal struts and more preferably four proximal struts. Apposition member  124  is used to provide proper apposition of the filter  120  against the wall of the vessel. Apposition member  124  is also connected to a plurality of distal struts  126  which are connected to a distal collar  130 . Filter frame  128  may be constructed by cutting a single tube of material or may be constructed from a number of different combinations of proximal and distal struts and an apposition member, proximal collar and distal collar which may be interconnected by a number of known means such as welding, brazing or chemical bonding. Filter frame  128  may be made of any number of metal alloys but is preferably made from a “shape memory” metal such as nitinol. 
         [0036]    Filter membrane  129  is attached to filter frame  128  and may be comprised of a polymeric blend or may also be made of a thin film of nitinol or other similar metal exhibiting memory characteristics. If filter membrane  129  is a polymeric membrane it can be bonded to filter frame  128  or can be molded around the filter frame  128  as part of the manufacturing process. Filter membrane  129  contains a plurality of holes which are sized to provide a path for fluid flow but are not large enough to permit emboli to pass. The preferred hole size is 0.00394″ (0.1 mm) and there are preferably approximately 3100 holes per square centimeter. Distal tip  150  is a tapered polymeric sleeve or a tapered coil that provides an atraumatic transition between the distal end  106  of the core guidewire  104  and the filter  120 . 
         [0037]    Other types of filter elements can be substitute for the filter  120  of  FIG. 1  of the present invention without departing from the spirit of the present invention. For example, filter  120  could be a wire mesh filter made of a woven wire fabric wherein the interstices between the metal wires provides the proper filtering function or a thin film nitinol mesh. Additionally filter  120  and/or filter membrane  129  could be comprised of woven polymeric threads. Filter  120  may be a self-actuating filter, i.e., one that expands to oppose the vessel wall upon removal from a restraining sheath or other restraining mechanism or the filter may be one that requires actuation such as through mechanical compression or inflation of an actuation balloon. A self-actuating filter is preferred because lack of an actuator results in a lower profile embolic protection device. Additionally, filter  120  could be a mechanically actuated filter requiring one or more wires, rods or other means of mechanical actuation. Other means of filter actuation are also possible. 
         [0038]      FIGS. 2A-D  depict the embolic protection device of  FIG. 1  in perspective and sectional perspective views including the additional feature of a motion limiter  140  which limits the axial movement of the filter assembly relative to the guidewire. The sectional view of  FIG. 2B  shows that guidewire core  102  extends the length of the embolic protection device from motion limiter  140  to the distal end covered by distal tip  150  with an atraumatic bullet nose  152 . Tubular member  110  extends from a substantial distance proximally of the filter basket  128  under proximal collar  130  and past distal collar  134 . Proximal collar  130  is fixedly mounted on the tubular member  110  using one of many known means of fixation such as bonding, soldering, brazing, or epoxying. Distal collar  134  is free floating on the tubular member  110 . In an alternative configuration proximal collar  130  and distal collar  134  could be rotatably mounted on tubular member  110  through the use of one or more longitudinal motion limiters (not shown) and or bearing surfaces (not shown) that would provide a second level of rotational freedom between the guidewire core  102  and the filter  120 . 
         [0039]      FIGS. 3A-E  depict another embodiment of the present invention in which the tubular member  210  extends from the same distance at the proximal end of the distal portion of the core guidewire  102  to the proximal collar  130  of the filter  120 . This reduces the profile of the filter  120  further. A thin walled polyimide sleeve (not shown) may be placed around the guidewire core  102  so that the filter membrane  129  will not grab on the guidewire core  102  when the filter is in a collapsed configuration. When filter frame  128  is made from a single tube of material such as when it is cut from a nitinol tube, the ID of each of the proximal collar  130  and the distal collar  134  is fixed. Since the tubular member  210  does not extend under the distal collar  134  of the filter the ID must be reduced so that it rotates around the guidewire core  102 . Two possible options to reduce the ID are to place a sleeve (which could be radiopaque) on the ID of the distal collar  134  or to position the guidewire coil such that the guidewire coil resides inside of the distal leg when the filter is in an expanded state. Clearance between the guidewire core  102  and the distal collar  134  should be minimized in order to prevent emboli from escaping the filter  120 . The embodiment in  FIGS. 3A-E  also include a second longitudinal motion limiter  240  which limits the movement of the filter assembly relative to the guidewire. 
         [0040]    An additional alternative embodiment is depicted in  FIGS. 4A-4D . A first tubular member  310  extends from the proximal end of the distal portion of the core guidewire (as discussed above with regard to  FIG. 1 ) to the proximal collar  130  of filter  120 . A second tubular member  320  extends from proximal collar  130  to distal collar  134 . Tubular member  320  may be connected to tubular member  310  or may rotate independently. Tubular member  320  may extend beyond the distal end of the basket giving a flexible transition between the filter  120  and the distal tip  150 . 
         [0041]      FIG. 5  depicts an embodiment of an embolic protection filter system in accordance with the present invention. In  FIG. 5  the embolic protection device  100  is placed within a deployment and delivery system  500  that comprises a distal portion  510  coaxially disposed around the core guidewire  102  and the filter  120  with filter frame  128 , proximal collar  130 , distal collar  134 , and tubular member  110 . Narrower proximal portion  508  of delivery system  500  is disposed around core guidewire  102 . In use the deployment and delivery system  500  with an embolic protection device  100  contained therein is placed through an incision in the patient into the lumen of a vessel of the patient. Once the distal end of the embolic protection filter system is placed distally of the region of interest and/or treatment such as a lesion, the filter is uncovered and the filter basket radially expands to oppose the lumen of the vessel of the patient. Upon completion of the procedure at the treatment site, the filter is collapsed using a retrieval catheter (not shown) as is known in the art. The embolic protection filter system is then removed from the vessel of the patient. 
         [0042]    The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. 
         [0043]    Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.