Abstract:
A removable intravascular filter system traps emboli and other solid materials in connection with intravascular medical procedures such as the placement of a stent or a catheter balloon. The system involves a hollow guidewire and an actuating wire movable within the guidewire to actuate the filter membrane. Embodiments of the filter system include biased closed and biased open filter configurations, and are easily routed through a patient&#39;s artery and deployed. Optionally, the actuating wire can be removed and a substitute wire can be inserted into the hollow guidewire. Control mechanisms can help the operator limit movement of the actuating wire during deployment and/or collapse of the filter membrane. Preferred filter membranes are configured to maximize both blood flow and emboli capture.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This patent application is a continuation-in-part of pending U.S. patent application Ser. No. 08/794,011, filed Feb. 3, 1997, pending U.S. patent application Ser. No. 09/155,753, filed Oct. 2, 1998, pending U.S. provisional patent application Serial No. 60/101,226, filed Sep. 21, 1998, pending U.S. provisional patent application Serial No. 60/101,227, filed Sep. 21, 1998, pending U.S. provisional patent application Serial No. 60/101,228, filed Sep. 21, 1998, and U.S. provisional patent application Serial No. 60/101,171, all of which are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to the treatment of vascular disease by either surgery or percutaneous angioplasty and stenting. More particularly, the invention relates to a system that reduces macro- and micro-embolization during the treatment of vascular stenosis.  
         BACKGROUND OF THE INVENTION  
         [0003]    A variety of surgical and non-surgical angioplasty procedures have been developed for removing obstructions from blood vessels. Balloon angioplasty utilizes a balloon-tipped catheter which may be inserted within a stenosed region of the blood vessel. By inflation of the balloon, the stenosed region is dilated. Surgery involves either removing the plaque from the artery or attaching a graft to the artery so as to bypass the obstructing plaque. Other techniques, such as atherectomy, have also been proposed. In atherectomy, a rotating blade is used to shave plaque from an arterial wall.  
           [0004]    One problem common with all of these techniques is the accidental release of portions of the plaque or thrombus, resulting in emboli which can lodge elsewhere in the vascular system. Such emboli are, of course, extremely dangerous to the patient, frequently causing severe impairment of the distal circulatory bed. Depending upon the vessel being treated, this may result in a stroke or myocardial infarction or limb ischemia.  
           [0005]    Vascular filters or embolism traps for implantation into the vena cava of a patient are well known, being illustrated by, for example, U.S. Pat. Nos. 4,727,873 and 4,688,553. Additionally, there is a substantial amount of medical literature describing various designs of vascular filters and reporting the results of the clinical and experimented use thereof. See, for example, the article by Eichelter &amp; Schenk entitled “Prophylaxis of Pulmonary Embolism,” Archives of Surgery, Vol. 97, August 1968, pp. 348 et seq. See, also, the article by Greenfield, et al., entitled “A New Intracaval Filter Permitting Continued Flow and Resolution of Emboli”, Surgery, Vol. 73, No. 4, pp. 599-606 (1973).  
           [0006]    Vascular filters are used, often during a postoperative period, when there is a perceived risk of a patient encountering a pulmonary embolus resulting from clots generated at the surgical site or the like. As a typical use of vascular filters, the filter is mounted in the vena cava to catch large emboli passing from the surgical site to the lungs.  
           [0007]    The vascular filters of the prior art are usually permanently implanted in the venous system of the patient, so that even after the need for the filter has abated, the filter remains in place for the lifetime of the patient, absent surgical removal. U.S. Pat. No. 3,952,747 describes a stainless steel filtering device which is permanently implanted transvenously within the inferior vena cava. The filtering device is intended to treat recurrent pulmonary embolism. U.S. Pat. No. 4,873,978 describes a catheter device comprising a catheter body having a strainer mounted at it distal end. The strainer is shiftable between an opened configuration where it extends substantially across the blood vessel to entrap passing emboli, and a closed configuration where it retains the captured emboli during removal of the catheter. A mechanism actuable at the proximate end of the catheter body allows selective opening and closing of the strainer. Typically, the strainer is a collapsible cone having an apex attached to a wire running from the distal end to the proximate end of the catheter body.  
           [0008]    Permanent implantation is often deemed medically undesirable, but it has been done because vascular filters are implanted in patients primarily in response to potentially life threatening situations. Accordingly, the disadvantages of permanent implantations of a vascular filter are often accepted.  
           [0009]    To avoid permanent implantation, it would be highly desirable to provide an apparatus and method for preventing embolization associated with conventional surgery and angioplasty procedures. In particular, it would be desirable to provide a device which could be located within the vascular system to collect and retrieve portions of plaque and thrombus which have dislodged during the surgery or angioplasty procedure.  
         OBJECT OF THE INVENTION  
         [0010]    It is an object of this invention to provide a vascular filter system for reducing macro- and micro-embolization.  
           [0011]    It is also an object of the invention to provide a vascular filter system which is readily removable from the vascular system, or elsewhere, of a patient when the filter is no longer needed.  
           [0012]    It is a further object of the invention to provide a vascular filter system having a configuration which does not require hooks to penetrate and grip the blood vessel walls, so that the implantation results in less blood vessel injury.  
           [0013]    It is a yet further object of the invention to provide a vascular filter system of very low profile which is part of a guidewire and can be used in small vessels.  
           [0014]    These and other objects of the invention will become more apparent from the description below.  
         SUMMARY OF THE INVENTION  
         [0015]    The present invention generally relates to a vascular filter system useful in the surgical or interventional treatment of vascular disease, in particular, a novel percutaneous angioplasty and stenting system useful, for example, in the treatment of carotid stenoses. Macro- and micro-embolization occurs during percutaneous procedures such as angioplasty, which increases the risk of a minor or major stroke. The system of the present invention for reducing macro- and micro-embolization is very useful in helping to prevent the risk of stroke. However, this system would also be useful in any angioplasty or surgical procedure where embolization is a risk.  
           [0016]    The vascular filter system of the present invention will decrease embolism while allowing brain, or other distal tissue, perfusion. The filters are incorporated into a guidewire which is used for the entire procedure from crossing a lesion to deploying a stent. In one embodiment the filter consists of a thin membrane attached to the guidewire and supported by fine metal spines. Attachment of the filter membrane to the guidewire allows expansion of the filter membrane with a firm fit inside the artery. The attachment also allows for collapse of the filter membrane at the end of the procedure so it fits tightly against the guidewire and can be withdrawn through the guide catheter. In another embodiment, the filter membrane rests upon or is attached to a basket-like structure, at least one end of which is attached to the guidewire. The filter membrane has a pore size such that blood flow is not impeded when the filter membrane is expanded but micro- and macro-emboli are blocked. Expansion of the filter membrane is aided by the forward flow of blood against the filter. The filter design results in a very low profile so that the initial crossing of the lesion is minimally traumatic. Also, the small diameter and small profile facilitate use of the device in small or larger arteries with minimal or no obstruction of blood flow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which the reference characters refer to like parts throughout and in which:  
         [0018]    [0018]FIG. 1 is a lateral, partly cross-sectional view of the distal end of a guidewire of one embodiment of the invention with the filter membrane in a collapsed position;  
         [0019]    [0019]FIG. 2 is a lateral, partly cross-sectional view of the distal end of a guidewire of FIG. 1 with the filter membrane in an expanded, deployed position;  
         [0020]    [0020]FIG. 3 is a proximal end-on view of the filter membrane shown in FIG. 2;  
         [0021]    [0021]FIG. 4 is a lateral, partly cross-sectional view of another embodiment of the invention;  
         [0022]    [0022]FIG. 5A is a lateral, partly cross-sectional view of a further embodiment of the invention;  
         [0023]    [0023]FIG. 5B is a lateral, partly cross-sectional view of the embodiment of the invention shown in FIG. 5A with the filter membrane in an expanded, deployed position;  
         [0024]    [0024]FIG. 6 is a partly cross-sectional view of a control handle for the invention;  
         [0025]    [0025]FIG. 7 is a partly cross-sectional view of another embodiment of the invention;  
         [0026]    [0026]FIG. 8 is a partial cross-sectional view of an embodiment of the invention wherein the filter membrane has curved supports;  
         [0027]    [0027]FIG. 9 is a partial cross-sectional view of yet another embodiment of the invention wherein the filter membrane has a spiral wire;  
         [0028]    [0028]FIG. 10 is a top, cross-sectional view of the embodiment of the invention shown in FIG. 9;  
         [0029]    [0029]FIG. 11 is a partial cross-sectional view of another embodiment of the invention having inflatable support spines;  
         [0030]    [0030]FIGS. 12 and 13 represent partial cross-sectional views of another embodiment of the invention in collapsed and deployed positions, respectively;  
         [0031]    [0031]FIG. 14 is a lateral, partly cross-sectional view of one embodiment of the invention with the filter membrane in an open position;  
         [0032]    [0032]FIG. 15 is a lateral, partly cross-sectional view of the embodiment of the invention in FIG. 14 with the sheath closed;  
         [0033]    [0033]FIG. 16 is a schematic representation of a portion of a filter membrane useful according to the invention;  
         [0034]    [0034]FIG. 17 is a lateral view of a core wire useful according to the invention;  
         [0035]    [0035]FIG. 18 is a cross-sectional view across line  18 - 18  of a portion of the core wire of FIG. 17;  
         [0036]    [0036]FIG. 19 is a lateral, cross-sectional view of an alternative basket structure for the embodiment of FIG. 14  
         [0037]    [0037]FIG. 20 is a lateral, partly cross-sectional view of another embodiment of the invention;  
         [0038]    [0038]FIG. 21 is a lateral, partly cross-sectional view of a further embodiment of the invention;  
         [0039]    [0039]FIG. 22 is a schematic, partially cross-sectional view of another embodiment of the invention where the distal section of the filter basket is inverted; and  
         [0040]    [0040]FIG. 23 is a schematic, partially cross-sectional view of the embodiment shown in FIG. 22 where the filter basket is collapsed. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0041]    The present invention relates to a vascular filter system for use in percutaneous angioplasty and stenting and provides for the prevention of distal embolism during endovascular procedures. Further, the filter system of the invention allows for distal perfusion while preventing embolization.  
         [0042]    The system comprises a thin, perforated filter membrane which is capable of blocking emboli and which is attached to the distal end of a guidewire. In one embodiment the system uses thin fibers which are moveable and are attached to or encapsulated by the filter membrane to deploy and/or collapse the filter membrane. The invention also contemplates the use of metal spines or inflatable spines attached to the filter membrane to deploy the filter membrane. The fibers or spines can also be attached to a moveable core which is slidable within the guidewire and is used to deploy and collapse the filter membrane.  
         [0043]    The filter membrane deploys in an umbrella-like fashion with the unattached edge of the membrane moving upward, i.e., distally, and outward until it is in firm contact with an artery wall. When the filter membrane is deployed, it spans the cross-sectional area of the vessel lumen being treated for a stenosis such as carotid stenosis, or another condition likely to produce emboli.  
         [0044]    In another, preferred embodiment of the invention, a thin, flexible, perforated membrane is supported by four or more supports that form a distally extending basket. At least one end of the basket is attached to the guidewire, and the other, slidable end can be moved to cause the membrane to open or close.  
         [0045]    The invention can perhaps be better appreciated by reference to the drawings. FIG. 1 illustrates a lateral, cross-sectional view of a distal end of a guidewire  10  with a filter membrane  20  attached thereto. FIG. 1 shows guidewire  10  with a shapeable, tapered soft tip  15  at its extreme distal end which provides flexibility and maneuverability to guidewire  10 . The filter membrane in FIG. 1 is in a collapsed position. Filter membrane  20  has a fixed portion  24  which is movably attached to guidewire  10 , and filter membrane  20  lies adjacent guidewire  10  proximal to fixed portion  24  when filter membrane  20  is in the collapsed state. A moveable core  40  runs through a center lumen  11  of guidewire  10  and preferably extends distally a short distance beyond fixed portion  24  of filter membrane  20 . Deploying wires or fibers  30  are each firmly attached at one end  27  to moveable core  40  distal to fixed portion  21  of filter membrane  20 . The deploying fibers  30  are attached at their other ends to filter membrane  20  at attachment points  22 .  
         [0046]    Collapsing fibers  35  are each firmly attached at one end  12  to the portion of moveable core wire  40  which is interior to filter membrane  20  when it is in the collapsed state. Collapsing fibers  35  are each attached at their other end  13  to filter membrane  20  at attachment points  22 . Accordingly, collapsing fibers  35  lie interior to filter membrane  20  when filter membrane  20  is in the collapsed state.  
         [0047]    Filter membrane  20  is deployed when the operator pulls moveable core  40  proximally through the interior of guidewire  10 . Prior to retraction of moveable core  40 , deploying fibers  30  are sufficiently relaxed so as not to create any tension at filter membrane attachment points  22 . Upon retraction of moveable core  40 , tension is created in deploying fibers  30 .  
         [0048]    There will preferably be from  2  to  6  each of evenly-spaced deploying fibers  30  and collapsing fibers  35 ,  3  or  4  being most preferred. The deploying fibers  30  and collapsing fibers  35  can be made of any flexible, medically acceptable material, including stainless steel, nitinol, or another metal or metallic alloy or a non-metallic substance such as graphite or a suitable polymer. In addition, guidewire  10  and moveable core  40  can be made from similar materials, as would be appreciated by those skilled in the art. Typically, guidewire  10  could have an external diameter of from about 0.014 mm to about 0.035 mm, a wall thickness of from about 0.002 mm to about 0.010 mm, and a length of from about 25 cm to about 300 cm. Also, moveable core  40  could have a diameter of from about 0.003 mm to about 0.010 mm and a length of from about 30 cm to about 350 cm.  
         [0049]    [0049]FIG. 2 illustrates the filter device of the invention in a deployed position on the inside of an artery wall  60 . Moveable core  40  is in a retracted state, i.e., pulled proximally through the interior of guidewire  10 . Tension is created in deploying fibers  30 , and filter membrane  20  extends to a deployed position where the outer edge  14  of filter membrane  20  contacts artery wall  60 . In this deployed position, collapsing fibers  35  are in a relaxed state and extend from filter membrane attachment points  22  to fixed attachment points  28  on moveable core  40 .  
         [0050]    The flow of blood in FIG. 2 is toward the distal end of guidewire  10 . As such, the force of the flow of blood pushes on deployed filter membrane  20  and helps to maintain filter membrane  20  in the deployed position.  
         [0051]    For withdrawal of guidewire  10  and the filter device, filter membrane  20  is collapsed so that it sits tightly against guidewire  10 . This is accomplished by extending moveable core  40  distally through guidewire  10 , thus relaxing deploying fibers  30  and creating tension in collapsing fibers  35 . The tension in collapsing fibers  35  collapses the filter membrane  20 , allowing it to fit tightly against guidewire  10  in recess  16  as depicted in FIG. 1.  
         [0052]    [0052]FIG. 3 illustrates the filter device of the invention from a distal end view in FIG. 2 with filter membrane  20  deployed. Guidewire  10  is centrally located, and structural wires  50  are seen extending from guidewire  10  to the outer edge  14  of filter membrane  20 . These wires  50  provide structural integrity and rigidity to filter membrane  20 . FIG. 3 depicts four, evenly-spaced structural wires  50 , but there can be more or less structural wires  50 . Preferably there are from two to six structural wires  50 , which may be spaced regularly or irregularly. The wires  50  may preferably be comprised of stainless steel or another medically acceptable metal or alloy.  
         [0053]    Filter membrane  20  of the invention is preferably a mesh such as that depicted in FIG. 3. The mesh should have pores of a size sufficient to block and capture any micro- and macro-emboli which may flow downstream from the site where the stenosis is being treated, but large enough such that blood flow is not impeded. The mesh used in the filter device of the invention can have a pore size of from about 20 to about 300 microns, preferably from about 50 to about 150 microns. Moreover, the size of filter membrane  20 , i.e., the distance from guidewire  10  to free ends  22 , is such as to allow a firm fit between filter membrane  20  and artery wall  60 . The diameter of filter membrane  20  will be directly related to the artery being treated, with typical diameters ranging from about 2 mm to about 40 mm, most preferably from about 2 mm to about 20 mm.  
         [0054]    The membrane can be comprised of fabric or non-fabric meshes, such as those used in known hemodialysis filters or heart-lung bypass machine filters. Suitable materials include polymers or physiologically acceptable metals or alloys.  
         [0055]    In alternative embodiments of the invention shown in FIGS. 4, 5A and  5 B, filter membrane  20  will be suspended between from two to eight, preferably from four to eight, thin metal wires  51  which serve as spines for filter membrane  20 . Wires  51  may be comprised of stainless steel or another metallic alloy, nitinol, or another shape-memory material. Wires  51  will be constructed so that they assume a 90° angle with guidewire  10  when they are in an unconstrained state. This will result in expansion of the filter membrane  20  to a position normal to guidewire  10 . A set of thin fibers  17  are attached at attachment points  18  to filter membrane outer edge  14  and are used to collapse filter membrane  20 .  
         [0056]    [0056]FIG. 4 shows an embodiment of this invention in which metal wires  51  are allowed to regain their 90° angle unconstrained state by use of a moveable core  40  that runs through guidewire  10 . Prior to retraction of moveable core  40 , fibers  17  are sufficiently tensed so as to restrain wires  51 . Upon retraction of moveable core  40 , tension in fibers  17  is released and wires  51  are allowed to revert to their relaxed shape, which will result in expansion of filter membrane  20  to a position normal to guidewire  10 .  
         [0057]    [0057]FIGS. 5A and 5B show an embodiment of the invention wherein wires  51  are restrained by fibers  17  that run through guidewire  10  and that are controlled at a remote location. In FIG. 5A, there is sufficient tension in fibers  17  to maintain wires  51  in a constrained position. In FIG. 5B, tension in fibers  17  has been relaxed such that wires  51  are allowed to revert to their relaxed shape, which will result in expansion of filter membrane  20  to a position normal to guidewire  10 .  
         [0058]    [0058]FIG. 6 depicts a control handle especially suitable for the embodiment of the invention shown in FIGS. 5A and 5B. The proximal end  32  of guidewire  10  is rotatably attached to handle  33 , such that rotation of handle  33  causes handle  33  to move distally or proximally relative to proximal guidewire end  32 . For example, handle  33  may have threads  34  which engage threads  35  on guidewire proximal end  32 . Fibers  17  attached to filter membrane  20  are secured in a base  36  of handle  33 . Then, as handle  33  is turned, the fibers  17  move distally or proximally to open or close filter membrane  20 .  
         [0059]    As handle  33  is turned clockwise in the direction of arrow A and fibers  17  are allowed to move distally in the direction of arrow C, the tension on the filter membrane fibers  17  decreases and wires  51  are allowed to assume their natural 90° angle with respect to the guidewire, resulting in opening of filter membrane  20 . Similarly, when handle  33  is turned counter-clockwise in the direction of arrow B and fibers  17  are pulled proximally in the direction of arrow D, the tension on filter fibers  17  increases, causing filter membrane  20  to collapse tightly against guidewire  10 . Of course, the direction of turn of handle  33  as discussed above can be reversed, as long as threads  34 , 35  are properly formed to allow appropriate movement of handle  33  relative to guidewire proximal end  32 .  
         [0060]    In yet another embodiment of the invention, shown in FIG. 11, filter membrane  20  can be supported by inflatable spines  135  supporting the filter membrane  20 . Spines  135  supporting the filter membrane  20  are from two to six hollow plastic tubes which are inflatable using, for example, a standard balloon angioplasty inflation device or endoflator in fluid connection through channel  137  with spines  135 . Inflation of spines  135  causes them to become rigid and deploys filter membrane  20 . The underside of the filter membrane is attached to very thin fibers  17  which are attached to moveable core  40  inside hollow guidewire  10 . Filter membrane  20  is collapsed by deflating the spines  135  and withdrawing the moveable core  40  in the direction of arrow E until the membrane  20  fits tightly against guidewire  10 .  
         [0061]    A catheter-based configuration is also possible, as shown in FIG. 7. In this design, the guidewire is not part of the filter catheter; the guidewire and filter catheter are two separate components. The filter catheter has an entry hole for the guidewire below the attachment of the filter membrane and the guidewire exits out the end of the filter catheter. The filter catheter could be designed to accommodate a variety of guidewire sizes, most commonly a 0.014 inch guidewire. The advantages of this design are that a variety of guidewires could be used; the lesion could be crossed with the guidewire prior to crossing with the filter catheter; the filter catheter could be removed from the artery without removing the guidewire; and the filter catheter could be made smaller.  
         [0062]    In the embodiment of the invention shown in FIG. 7 a catheter  101  comprises a longitudinally extending lumen  103 , which has an annular recess  105  adjacent the distal end of catheter  101 . Positioned within recess  105  is a filter  107  comprised of structural wires  109  and a filter membrane  111 . The distal end of each of wires  109  is attached at point  113  in recess  105 . Fibers  117  extend from the proximal ends  119  of wires  109  proximally to a control means such as described in FIG. 6.  
         [0063]    Catheter  101  contains guidewire port  125  located proximal to recess  105 . It is intended that in use the distal portion  128  of a guidewire  127  will be threaded into the distal end  129  of catheter  101  and out through port  125 .  
         [0064]    Alternatively, and not shown here, a catheter  101  could comprise a longitudinally extending lumen and a shorter tracking lumen that extends from distal end  129  to a point proximal to recess  105 . The distal end of guidewire  127  would then be threaded into the distal opening of the tracking lumen and out the proximal end of the tracking lumen.  
         [0065]    Spiral or curved structural wires may be used to deploy the filter membrane instead of straight wires. FIG. 8 illustrates the use of four curved wires  120 . The angulation of the filter attachment point of wires  120  relative to their guidewire attachment has the effect of wrapping the filter fabric around the guidewire in the undeployed state. This leads to a lower profile for the undeployed filter.  
         [0066]    [0066]FIGS. 9 and 10 illustrate the use of a single spiral structural wire  130  which is attached to the filter  107 . As tension fiber  131  is released, wire  130  unwinds and deploys filter  107  in a conical configuration. This configuration has the simplicity of using a single wire and, when the tension on fiber  131  is increased, allows filter  107  to be wrapped very tightly around the guidewire shaft  131 , resulting in filter  107  having a low profile in its undeployed state.  
         [0067]    Another modification shown in FIGS. 12 and 13 comprises a retractable sheath  140  at the distal end of guidewire  142  which covers filter membrane  144  in the collapsed state. Sheath  140 , the distal portion of which is affixed to guidewire tip  146 , which is affixed to the distal end of moveable core  148 , would prevent an edge  150  of filter membrane  144  from becoming entangled in an artery or guide catheter as it was being withdrawn from a patient.  
         [0068]    More specifically, when guidewire  142  with tapered tip  146  is inserted percutaneously into a patient, sheath  140  covers collapsed filter membrane  144 . After the filter membrane is determined by fluoroscopy to be in proper position, moveable core  148  is pushed distally to cause sheath  140  to “release” filter membrane  144 , which has spines  152 , to cause filter membrane  144  to deploy, as shown in FIG. 13.  
         [0069]    [0069]FIG. 14 illustrates a lateral, cross-sectional view of a distal end of a guidewire  160  with a filter membrane  170  attached thereto. FIG. 14 shows guidewire  160  with a shapeable soft “floppy” tip  162  at its extreme distal end which provides flexibility and maneuverability to guidewire  160 . The filter membrane in FIG. 14 is in an open position.  
         [0070]    Guidewire  160  comprises a core wire  164 , which extends into floppy tip  162 , and a sheath  166 . Filter membrane  170  is supported by a basket  169  comprising two or more filter basket wires  168 , having distal ends  172  and proximal ends  174 . The distal ends  172  of basket wires  168  are fixedly attached by distal radiopaque marker or crimp band  176  to core wire  164 , and the proximal ends  174  of basket wires  168  are attached to proximal radiopaque marker or crimp band  178 , which is slidable over core wire  164 , optionally with a polymeric, such as polyimide, or metallic sleeve between core wire  164  and proximal ends  174 . Optionally, and preferably, proximal marker  178  is fixedly attached to core wire  164 , and distal marker  176 , with a polymeric or metallic sleeve, is slidable over core wire  164 .  
         [0071]    A sheath member  180  is attached to the distal end of sheath  166 , sheath member  180  having a lumen  182  with a diameter and length sufficient to receive or slide over proximal marker  178 . Sheath  166  and sheath member  180  can be either separate pieces bonded together or a continuous, integral structure. Sheath  166  and sheath member  180  are each made from low friction polymeric material, preferably polytetrafluoroethylene, polyethylene, nylon, or polyurethane.  
         [0072]    Filter membrane  170  can comprise a number of different metallic or non-metallic permeable membranes having sufficient porosity to facilitate blood flow but having sufficiently small openings to capture emboli. Filter membrane  170  must be affixed at least at its distal portion  184  to core wire  164  and/or basket wire distal ends  172  and, optionally, to basket wires  168 . The remainder of filter membrane  170  can be unattached or, preferably, attached to basket wires  168 , such as by a suitable adhesive. Preferably basket wires  168  are encapsulated in membrane  170 .  
         [0073]    Basket  169  can be somewhat cylindrical in its middle with tapered, conical proximal and distal portions. Alternatively, basket  169  can be slightly spherical, optionally with a flat, cylindrical middle portion. Preferably basket  169  is from about 5 to about 40 mm in length and from about 2 to about 30 mm, or from about 2 to about 20 mm, in diameter at its widest.  
         [0074]    The proximal end of sheath  180  is attached to control handle or guidewire torquer  186 . Control handle  186  has an opening  188  for core wire  164  so that sheath  180  can move slidably over core wire  164 . For example, when sheath  180  is moved distally toward basket wires  168 , filter membrane  170  collapses. Also, there may be instances where sheath  180  will be removed proximally so that other catheters or cardiovascular appliances can be introduced over core wire  164 . Control handle  186 , which functions as a torque device, also primarily functions to lock sheath  180  to core wire  164  during insertion.  
         [0075]    There are a number of known, commercially available guidewire torquers that can be modified to function as control handle  186 . Modification includes, but is not limited to, providing a slightly larger central lumen.  
         [0076]    In FIG. 15 sheath  166  and sheath member  180  are shown advanced distally so that basket wires  168  and filter member  170  are collapsed against core wire  164 . The distal end  192  of sheath member  180  may optionally be slightly tapered to provide a better profile for insertion.  
         [0077]    In a preferred embodiment of the invention, as shown in FIG. 16, filter membrane  170  comprises a polymeric material such as polyurethane or silicone elastomer that has laser-drilled holes  190 . Such holes  190 , a pattern for which can be seen in FIG. 16, are preferably only on the conical portion of filter membrane  170 . The holes  190  could be from about 50 to 300 μm in diameter. The vertical row separation of holes  190  can be from 1.2 to 1.4 times the hole diameter and the center-to-center diameter of holes  190  can be from about 1.4 to 1.6 times the hole diameter, or in a preferred embodiment the vertical and horizontal spacing of the holes is such that the center-to-center spacing of the holes is from about 1.2 to 2.0 times the hole diameter. Preferably the open area of the holes represents from about 10 to 50 percent, more preferably from about 10 to 40%, of the filter surface.  
         [0078]    Basket wires  168  could be comprised of a suitable, physiologically acceptable metal. Stainless steel or nitinol are preferred, although titanium or other metal alloys could be used.  
         [0079]    Core wire  164  can be seen better in FIG. 17, where the proximal and middle portions  200  and  202  are substantially uniform in diameter, and then the distal portion  204  tapers to an end point  206 . In fact, distal portion  204  could taper uniformly or, more preferably, non-uniformly, as shown in FIG. 17. Typically core wire  164  is from about 250 to 300 cm in length, with an initial diameter of from about 0.009 to 0.038 in., preferably from about 0.014 to 0.018 in. Distal section  204  is typically from about 8 to 10 cm. in total. With a diameter that tapers to from about 0.001 to 0.005 in. Core wire  164  may optionally have a thin polymeric coating  207  for friction reduction. Preferably end point  206  is a solid, squat cylinder, as shown in FIGS. 17 and 18.  
         [0080]    Floppy tip  162  preferably comprises a radiopaque helical spring  210  that is fixedly attached, e.g., by welding, brazing, or soldering, to end point  206  and, optionally, attachment point  208 . Optionally spring coil  210  may have a polymeric or lubricious coating  212 .  
         [0081]    [0081]FIG. 19 represents an alternate design where basket wires  220  are substantially helical in shape. Filter member  222  covers or encompasses the distal portion of basket wires  220 , and the proximal and distal portions of basket wires  220  are secured by proximal radiopaque marker or crimp band  224  and distal radiopaque marker or crimp band  226 , respectively. Markers  224  and  226  are fixed or slidable on core wire  228  as described above. Preferably there are from 4 to 8 basket wires  220 , each with a rotation of from about 45° to 360° 
         [0082]    Additional embodiments of the invention can be seen in FIGS. 20 and 21. The schematic representation in FIG. 20 depicts a filter membrane  280  supported by strut wires  282 . The distal ends  284  of strut wires  282  are attached to the distal portion of a tubular member  286 . A movable core wire  290  extends through a lumen  292  in tubular member  286  to a distal floppy section  294 , where a helical spring coil  296  surrounds the distal portion  298  of core wire  290  and is attached to end point  300 . There is an attachment point  302  of weld or solder at the proximal portion of spring coil  296  where the distal portion  304  of sheath member  306  is also attached to core wire  290 . The lumen  308  of sheath member  306  is large enough so that as core wire  290  is pulled proximally, or tubular member  286  is advanced distally, the distal ends  284  of strut wires  282  move into lumen  308  and collapse filter membrane  280 .  
         [0083]    Moveable core wire  250  of the structure shown in FIG. 21 comprises a floppy tip  252  where a helical spring coil  254  encompasses the distal portion  256  of core wire  250 . A basket wire structure component of two or more basket wires  258  supports a filter membrane  260  on the distal portion  262  of the basket structure. Distal ends  264  of the basket wires  258  are encompassed by a radiopaque marker or crimp band  266  that is attached to core wire  250  and/or spring coil  254 . The proximal ends  268  of basket wires  258  are attached to the distal portion of a sheath  270  that surrounds core wire  250 . Sheath  270  moves slidably over core wire  250  so that when sheath  270  is pulled proximally into core wire  250 , filter membrane  260  collapses.  
         [0084]    In FIG. 22 a basket  320  comprised of from 4 to 8 strut wires  322  is secured by a distal fixed grommet  324  and a proximal slidable grommet  326 . Grommet  326  is slidable over core wire  328 . Filter membrane  330  is attached to or arranged upon basket  320 , with the proximal section  332  of the membrane  290  being open to flow, represented by arrows  334 . The distal portion  336  of membrane  330  forms a conical shape  340  that extends proximally. The filter could be deployed by, for example, a sheath or a tube fixed to the proximal slidable crimp band  336 . This design is optimized for perfusion and emboli collection. For example, as more emboli is collected, it tends to collect in outer, non-filter areas, leaving the pores open for perfusion.  
         [0085]    Membrane  330  preferably has holes only in distal section  336 / 340 , which holes are arranged as described above. It is believed that under normal, substantially laminar flow conditions debris or emboli  342  will tend to collect in annular recesses  344 .  
         [0086]    To close and capture emboli, as shown in FIG. 23, slidable grommet  326  is moved proximally to collapse basket  320  and membrane  336 . This can be accomplished with, for example, sheath  350  or a fixed tubular member or other apparatus that is preferably slidable over the core wire.  
         [0087]    The wires, membrane, and other materials of this embodiment are consistent with those described above.  
         [0088]    The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, however, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims.