Patent Publication Number: US-2005119691-A1

Title: Distal protection device and method

Description:
This application is a continuation-in-part of co-pending application Ser. No. 08/810,825 filed Mar. 6, 1997 entitled DISTAL PROTECTION DEVICE, and assigned to the same assignee as the present invention.  
      The following co-pending patent application is hereby incorporated by reference U.S. patent application Ser. No. 08/813,794, entitled DISTAL PROTECTION DEVICE which was filed on Mar. 6, 1997, and assigned to the same assignee as the present application. 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention deals with an emboli capturing system. More specifically, the present invention deals with an emboli capturing system and method for capturing embolic material in a blood vessel during an atherectomy or thrombectomy procedure.  
      Blood vessels can become occluded (blocked) or stenotic (narrowed) in one of a number of ways. For instance, a stenosis may be formed by an atheroma which is typically a harder, calcified substance which forms on the lumen walls of the blood vessel. Also, the stenosis can be formed of a thrombus material which is typically much softer than an atheroma, but can nonetheless cause restricted blood flow in the lumen of the blood vessel. Thrombus formation can be particularly problematic in a saphenous vein graft (SVG).  
      Two different procedures have developed to treat a stenotic lesion (stenosis) in vasculature. The first is to deform the stenosis to reduce the restriction within the lumen of the blood vessel. This type of deformation (or dilatation) is typically performed using balloon angioplasty.  
      Another method of treating stenotic vasculature is to attempt to completely remove either the entire stenosis, or enough of the stenosis to relieve the restriction in the blood vessel. Removal of the stenotic lesion has been done through the use of radio frequency (RF) signals transmitted via conductors, and through the use of lasers, both of which treatments are meant to ablate (i.e., super heat and vaporize) the stenosis. Removal of the stenosis has also been accomplished using thrombectomy or atherectomy. During thrombectomy and atherectomy, the stenosis is mechanically cut or abraded away from the vessel.  
      Certain problems are encountered during thrombectomy and atherectomy. The stenotic debris which is separated from the stenosis is free to flow within the lumen of the vessel. If the debris flows distally, it can occlude distal vasculature and cause significant problems. If it flows proximally, it can enter the circulatory system and form a clot in the neural vasculature, or in the lungs, both of which are highly undesirable.  
      Prior attempts to deal with the debris or fragments have included cutting the debris into such small pieces (having a size on the order of a blood cell) that they will not occlude vessels within the vasculature. However, this technique has certain problems. For instance, it is difficult to control the size of the fragments of the stenotic lesion which are severed. Therefore, larger fragments can be severed accidentally. Also, since thrombus is much softer than an atheroma, it tends to break up easier when mechanically engaged by a cutting instrument. Therefore, at the moment that the thrombus is mechanically engaged, there is a danger that it can be dislodged in large fragments which would occlude the vasculature.  
      Another attempt to deal with debris severed from a stenosis is to remove the debris, as it is severed, using suction. However, it may be necessary to pull quite a high vacuum in order to remove all of the pieces severed from the stenosis. If a high enough vacuum is not used, all of the severed pieces will not be removed. Further, when a high vacuum is used, this can tend to cause the vasculature to collapse.  
      A final technique for dealing with the fragments of the stenosis which are severed during atherectomy is to place a device distal to the stenosis during atherectomy to catch the pieces of the stenosis as they are severed, and to remove those pieces along with the capturing device when the atherectomy procedure is complete. Such capture devices have included expandable filters which are placed distal of the stenosis to capture stenosis fragments. Problems are also associated with this technique. For example, delivery of such devices in a low profile, pre-deployment configuration can be difficult. Further, some devices include complex and cumbersome actuation mechanisms. Also, retrieving such capture devices, after they have captured emboli, can be difficult as well.  
     SUMMARY OF THE INVENTION  
      An emboli capturing system captures emboli in a body lumen. A first elongate member has a proximal end and a distal end. An expandable emboli capturing device is mounted proximate the distal end of the first elongate member, and is movable between a radially expanded position and a radially contracted position. When in the expanded position, the emboli capturing device forms a basket with a proximally opening mouth. A second elongate member has a proximal and a distal end with a lumen extending therebetween. The lumen is sized to slidably receive a portion of the first elongate member. An expandable delivery device is mounted to the distal end of the second elongate member and is movable from a radially retracted position to a radially expanded position. The delivery device has a receiving end configured to receive the emboli capturing device, and retains at least the mouth of the emboli capturing device in a radially retracted position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a distal protection device of the present invention in a deployed position.  
       FIG. 2  shows the distal protection device shown in  FIG. 1  in a collapsed position.  
       FIG. 3  shows an end view of a portion of the distal protection device shown in  FIGS. 1 and 2 .  
       FIG. 4  shows a cross-sectional view of a portion of the distal protection device shown in  FIGS. 1-3  in the deployed position.  
       FIG. 5  shows a second embodiment of the distal protection device according to the present invention in a deployed position.  
       FIG. 6  shows an end view of the distal protection device shown in  FIG. 5 .  
       FIG. 7  shows a cross-sectional view of the distal protection device shown in  FIGS. 5 and 6  in the collapsed position.  
       FIG. 8  shows a third embodiment of a distal protection device according to the present invention in a deployed position.  
       FIG. 9  is a side sectional view of an alternate embodiment illustrating how the expandable members of the present invention are attached to a guidewire.  
       FIG. 10  is a sectional view taken along section lines  10 - 10  in  FIG. 9 .  
       FIGS. 11A and 11B  show a fourth and fifth embodiment, respectively, of a distal protection device according to the present invention in a deployed position.  
       FIG. 12  illustrates the operation of a distal protection device in accordance with the present invention.  
       FIGS. 13A-17B  show additional embodiments of distal protection devices which expand and collapse based on movement of a mechanical actuator.  
       FIGS. 18A-18D  illustrate an additional embodiment of a distal protection device which is deployed and collapsed using a rolling flap configuration.  
       FIG. 19  illustrates another embodiment in accordance with the present invention in which the protection device is deployed using fluid pressure and a movable collar.  
       FIGS. 20A and 20B  illustrate another aspect of the present invention in which two longitudinally movable members used to deploy the distal protection device are disconnectably locked to one another.  
       FIGS. 21A-21C  illustrate another embodiment in accordance with the present invention in which the protection device is formed with a shape memory alloy frame and an attached filter or mesh mounted to the frame.  
       FIGS. 22A-22C  illustrate another embodiment in accordance with the present invention in which the distal protection devices shown in  FIGS. 21A-21C  are delivered and deployed.  
       FIGS. 23A-23E  illustrate another embodiment in accordance with the present invention in which the distal protection devices shown in  FIGS. 21A-21C  are retrieved.  
       FIGS. 24A-24C  illustrate another embodiment in accordance with the present invention in which the distal protection devices shown in  FIGS. 21A-21C  are retrieved. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  illustrates protection device  10  in a deployed position within the lumen of a blood vessel  12 . Protection device  10  preferably includes hollow guidewire  14  (or a hypotube having the same general dimensions as a guidewire) having a coil tip  16 , and a capturing assembly  18 . Capturing assembly  18 , in the embodiment shown in  FIG. 1 , includes an inflatable and expandable member  20  and mesh  22 .  
      An interior of expandable member  20  is preferably coupled for fluid communication with an inner lumen of guidewire  14  at a distal region of guidewire  14 . When deployed, inflatable member  20  inflates and expands to the position shown in  FIG. 1  such that capturing assembly  18  has an outer periphery which approximates the inner periphery of lumen  12 .  
      Mesh  22  is preferably formed of woven or braided fibers or wires, or a microporous membrane, or other suitable filtering or netting-type material. In one preferred embodiment, mesh  22  is a microporous membrane having holes therein with a diameter of approximately 100 μm. Mesh  22  can be disposed relative to inflatable member  20  in a number of different ways. For example, mesh  22  can be formed of a single generally cone-shaped piece which is secured to the outer or inner periphery of inflatable member  20 . Alternatively, mesh  22  can be formed as a spiral strip which is secured about the outer or inner periphery of inflatable member  20  filling the gaps between the loops of inflatable member  20 . Alternatively, mesh  22  can be formed of a number of discrete pieces which are assembled onto inflatable member  20 .  
      Hollow guidewire  14  preferably has a valve  24  coupled in a proximal portion thereof. During operation, a syringe is preferably connected to the proximal end of guidewire  14 , which preferably includes a fluid hypotube. The syringe is used to pressurize the fluid such that fluid is introduced through the lumen of hollow guidewire  14 , through valve  24 , and into inflatable member  20 . Upon being inflated, inflatable member  20  expands radially outwardly from the outer surface of guidewire  14  and carries mesh  22  into the deployed position shown in  FIG. 1 . In this way, capturing assembly, or filter assembly,  18  is deployed distally of stenosis  26  so that stenosis  26  can be severed and fragmented, and so the fragments from stenosis  26  are carried by blood flow (indicated by arrow  28 ) into the basket or chamber formed by the deployed filter assembly  18 . Filter assembly  18  is then collapsed and removed from vessel  12  with the fragments of stenosis  26  contained therein.  
       FIG. 2  illustrates protection device  10  with filter assembly  18  in the collapsed position. Similar items to those shown in  FIG. 1  are similarly numbered.  FIG. 2  illustrates that mesh  22  is easily collapsible with inflatable member  20 . In order to collapse filter assembly  18 , fluid is preferably removed from inflatable member  20  through the lumen of hollow guidewire  14  and through two-way valve  24 . This can be done using the syringe to pull a vacuum, or using any other type of suitable fluid removal system.  
      Inflatable member  20  is preferably formed of a material having some shape memory. Thus, when inflatable member  20  is collapsed, it collapses to approximate the outer diameter of hollow guidewire  14 . In one preferred embodiment, inflatable member  20  is formed of a resilient, shape memory material such that it is inflated by introducing fluid under pressure through the lumen in hollow guidewire  14  into inflatable member  20 . When pressure is released from the lumen in hollow guidewire  14 , inflatable member  20  is allowed to force fluid out from the interior thereof through two-way valve  24  and to resume its initial collapsed position. Again, this results in filter assembly  18  assuming its collapsed position illustrated in  FIG. 2 .  
       FIG. 3  illustrates a view taken from the distal end of device  10  with mesh  22  removed for clarity.  FIG. 3  shows that, when inflatable member  20  is deployed outwardly, mesh  22  (when deployed between the loops of inflatable member  20 ) forms a substantially lumen-filling filter which allows blood to flow therethrough, but which provides a mechanism for receiving and retaining stenosis fragments carried into mesh  22  by blood flow through the vessel.  
       FIG. 3  also shows that inflatable member  20  preferably has a proximal end portion  29  which is connected to the outer periphery of guidewire  14 . Although end  29  need not be connected to guidewire  14 , it is preferably connected using adhesive or any other suitable connection mechanism. By fixedly connecting proximal end portion  29  to guidewire  14 , this increases the stability of the filter assembly  18  upon deployment.  
       FIG. 4  is a cross-sectional view of a portion of protection device  10 .  FIG. 4  shows protection device  10  with filter assembly  18  in the expanded or deployed position.  FIG. 4  also better illustrates that guidewire  14  is hollow and has a longitudinal lumen  30  extending therethrough. Longitudinal lumen  30  is connected in fluid communication with an interior of inflatable member  20  through aperture  32  which is provided in the wall of guidewire  14 .  FIG. 4  also shows that, in one preferred embodiment, a core wire  34  extends through lumen  30  from a proximal end thereof where it is preferably brazed to a portion of a hypotube which may be connected to the proximal portion of guidewire  14 . The core wire  34  extends to the distal end of guidewire  14  where it is connected to coil tip  16 . In one preferred embodiment, coil tip  16  is brazed or otherwise welded or suitably connected to the distal portion of core wire  34 .  
       FIG. 4  further shows that, in the preferred embodiment, inflatable member  20  inflates to a generally helical, conical shape to form a basket opening toward the proximal end of guidewire  14 .  FIG. 4  further illustrates, in the preferred embodiment, mesh  22  has a distal portion  38  which is connected to the exterior surface of guidewire  14 , at a distal region thereof, through adhesive  36  or any other suitable connection mechanism.  
       FIG. 5  illustrates a second embodiment of a distal protection device  40  in accordance with the present invention. Device  40  includes hollow guidewire  42 , filter assembly  44  and coil tip  16 . Filter assembly  44  includes a plurality of inflatable struts  46  and mesh  47 . Each strut  46  has a distal end  48  and proximal end  50 . Inflatable struts  46  also have an interior which is coupled in fluid communication, through distal end  48  thereof, with the lumen in hollow guidewire  42 . Struts  46  are preferably configured such that, upon being inflated, the proximal ends  50  deploy radially outwardly away from the outer surface of hollow guidewire  42  to assume a dimension which approximates the inner dimension of lumen  58  in which they are inserted.  
      Mesh  47 , as with mesh  22  shown in  FIG. 1 , is deployed either on the outer or inner surface of inflatable struts  46 , such that, when the inflatable struts  46  are deployed radially outwardly, mesh  47  forms a generally conical basket opening toward the proximal end of hollow guidewire  42 . As with the embodiment shown in  FIG. 1 , mesh  47  can be applied to either the outer or the inner surface of struts  46 . It can be applied to struts  46  as one unitary conical piece which is adhered about distal ends  48  of struts  46  using adhesive (or about the distal end of guidewire  42  using adhesive) and secured to the surface of the struts  46  also using adhesive. Alternatively, mesh  47  can be applied to struts  46  in a plurality of pieces which are individually or simultaneously secured to, and extend between, struts  46 .  
       FIG. 6  is an end view of distal protection device  40  shown in  FIG. 5  taken from the distal end of distal protection device  40 . When struts  46  are deployed outwardly, mesh  47  forms a substantially lumen-filling filter which allows blood to flow therethrough, but which provides a mechanism for receiving and retaining stenosis fragments from stenosis  56  carried into mesh  47  by blood flow through the vessel.  
       FIG. 7  is a cross-sectional view of a portion of distal protection device  40  shown in  FIGS. 5 and 6 .  FIG. 7  shows filter assembly  44  in the collapsed position in which it approximates the outer diameter of guidewire  42 .  FIG. 7  also shows that, in the preferred embodiment, the distal ends  48  of struts  46  are in fluid communication with an inner lumen  52  in hollow guidewire  42  through apertures  54  in the wall of guidewire  42 .  
       FIG. 8  illustrates another embodiment of a distal protection device  60  in accordance with the present invention. Distal protection device  60  is similar to those shown in other figures, and similar items are similarly numbered. However, distal protection device  60  includes hollow guidewire  63  which has a lumen in fluid communication with an interior of a pair of inflatable struts  62 . Inflatable struts  62  have an inner surface  64  which is generally concave, or hemispherical, or otherwise appropriately shaped such that it extends about a portion of the outer surface of hollow guidewire  63 . Mesh portions  66  extend between the inflatable struts  62  so that inflatable struts  62  and mesh portions  66 , when deployed outwardly as shown in  FIG. 8 , form a basket shape which opens toward the proximal end of hollow guidewire  63 .  
       FIG. 9  illustrates another system for attaching inflatable struts to a hollow guidewire for a distal protection device  70  in accordance with the present invention. Distal protection device  70  is similar to the distal protection devices shown in the previous figures in that a plurality of inflatable struts  72  are provided and preferably have a mesh portion extending therebetween. For the sake of clarity, the mesh portion is eliminated from  FIG. 9 . However, it will be understood that, when deployed, distal protection device  70  forms a generally basket-shaped filter assembly which opens toward the proximal end of hollow guidewire  74 .  
      In the embodiment shown in  FIG. 9 , hollow guidewire  74  has a distal end  75  which is open. An endcap  76  is disposed about the distal end  75  of hollow guidewire  74  and defines an internal chamber or passageway  78 . Endcap  76  has a proximal end  80  which has openings therein for receiving the ends of inflatable struts  72 . Thus, in order to inflate inflatable struts  72 , the operator pressurizes fluid within the lumen of hollow guidewire  74  forcing fluid out through distal end  75  of hollow guidewire  74 , through passageway  78 , and into inflatable struts  72 . In order to collapse distal protection device  70 , the operator draws a vacuum which pulls the fluid back out of inflatable struts  72 , through passageway  78  and, if necessary, into the lumen of hollow guidewire  74 .  
       FIG. 10  is an end view of endcap  76  taken along lines  10 - 10  in  FIG. 9 .  FIG. 10  shows that proximal end  80  of endcap  76  preferably includes a first generally central aperture  82  for receiving the distal end of hollow guidewire  74 . Aperture  82  is sized just larger than, or approximating, the outer diameter of hollow guidewire  74  such that it fits snugly over the distal end  75  of hollow guidewire  74 . Endcap  76  is then fixedly connected to the distal end  75  of hollow guidewire  74  through a friction fit, a suitable adhesive, welding, brazing, or another suitable connection technique.  
       FIG. 10  also shows that proximal end  80  of endcap  76  includes a plurality of apertures  84  which are spaced from one another about end  80 . Apertures  84  are sized to receive open ends of inflatable struts  72 . In the preferred embodiment, inflatable struts  72  are secured within apertures  84  using a suitable adhesive, or another suitable connection technique. Also, in the preferred embodiment, spring tip  16  is embedded in, or otherwise suitably connected to, endcap  76 .  
       FIGS. 11A and 11B  show two other preferred embodiments of a distal protection device in accordance with the present invention.  FIG. 11A  shows distal protection device  90  which includes hollow guidewire  92  having a lumen running therethrough, inflatable member  94  and mesh portion  96 .  FIG. 11A  shows that inflatable member  94 , when inflated, forms a ring about the outer surface of hollow guidewire  92 . The ring has an inner periphery  98  which is spaced from the outer surface of hollow guidewire  92  substantially about the entire radial periphery of hollow guidewire  92 . Mesh portion  96  extends between the outer surface of hollow guide  92  and the inner periphery  98  of inflatable member  94 . Thus, a substantially disc-shaped filter assembly is provided upon deployment of distal protection device  90 . As with the other embodiments, deployment of distal protection device  90  is accomplished by providing fluid through the inner lumen of hollow guidewire  92  into an interior of inflatable member  94  which is in fluid communication with the inner lumen of hollow guidewire  92 .  
      In one preferred embodiment, end  100  of inflatable member  94  is coupled to a coupling portion  102  of inflatable member  94  such that stability is added to inflatable member  94 , when it is inflated.  
       FIG. 11B  illustrates another distal protection device  104  which includes a hollow guidewire  106  and an inflatable member  108 . Device  104  is similar to distal protection device  90  except that, rather than having only a single inflatable ring upon deployment of distal protection device  104 , a plurality of generally equal-diameter rings are formed into a helix shape. In the preferred embodiment, distal protection device  104  includes a mesh sleeve  110  which extends about the outer or inner surface of the helix formed by inflatable member  108 . In one embodiment, mesh sleeve  110  is connected to the outer surface of hollow guidewire  106  in a region  112  proximate, but distal of, inflatable member  108 . In another preferred embodiment, the proximal end of mesh sleeve  110  is connected to the outer perimeter of inflatable member  108 . Thus, distal protection device  104  forms a generally basket-shaped filter assembly which opens toward a proximal end of guidewire  106 .  
      As with the other embodiments, both distal protection device  90  shown in  FIG. 11A  and distal protection device  104  shown in  FIG. 11B  are preferably collapsible. Therefore, when collapsed, the distal protection devices  90  and  104  preferably have an outer dimension which approximates the outer dimension of hollow guidewires  92  and  106 , respectively. Further, as with the other embodiments, distal protection devices  90  and  104  can either be biased in the deployed or collapsed positions, and deployment and collapse can be obtained either by pulling a vacuum, or pressurizing the fluid within the lumen of the hollow guidewires  92  and  106 .  
       FIG. 12  illustrates the use of a distal protection device in accordance with the present invention. For the sake of clarity, the present description proceeds with respect to distal protection device  10  only. Device  10  is shown filtering stenosis fragments from the blood flowing through the lumen of vessel  12 .  FIG. 12  also shows a dilatation device  120  which can be any suitable dilatation device for dilating, cutting, fragmenting, or abrading, portions of stenosis  26 . In the preferred embodiment, device  120  is used in an over-the-wire fashion over hollow guidewire  14 . Thus, filter assembly  18  is first advanced (using guidewire  14 ) distal of stenosis  26 . Then, filter assembly  18  is deployed outwardly to the expanded position. Dilatation device  120  is then advanced over guidewire  14  to stenosis  26  and is used to fragment or abrade stenosis  26 . The fragments are received within the basket of filter assembly  18 . Filter assembly  18  is then collapsed, and filter assembly  18  and dilatation device  120  are removed from vessel  12 . Alternatively, dilatation device  120  can be removed first and filter assembly  18  is then removed along with guidewire  14 .  
      It should be noted that the stenosis removal device (or atherectomy catheter)  120  used to fragment stenosis  26  can be advanced over guidewire  14 . Therefore, the device according to the present invention is dual functioning in that it captures emboli and serves as a guidewire. The present invention does not require adding an additional device to the procedure. Instead, the present invention simply replaces a conventional guidewire with a multi-functional device.  
       FIGS. 13A-17B  illustrate embodiments of various distal protection devices wherein deployment and contraction of the distal protection device is accomplished through a mechanical push/pull arrangement.  
       FIGS. 13A and 13B  illustrate a distal protection device  122 .  FIG. 13A  shows device  122  in an undeployed position and  FIG. 13B  shows device  122  in a deployed position. Distal protection device  122  includes a slotted Nitinol tube  124  which has a lumen  126  extending therethrough. Tube  124  has a plurality of slots  128  at a distal region thereof. The distal portion of slots  128  are covered by mesh  130  which, in the preferred embodiment, is a flexible microporous membrane. Device  122  also preferably includes a mandrel  132  which extends through the inner lumen  126  of tube  124  and is attached to the distal end of tube  124 . In the preferred embodiment, mandrel  132  is attached to the distal end of tube  124  by an appropriate adhesive, brazing, welding, or another suitable connection technique. Tube  124  also has, on its inner periphery in a proximal region thereof, a plurality of locking protrusions  134 . Lock protrusions  134  are preferably arranged about a proximal expandable region  136  disposed on mandrel  132 .  
      In order to deploy device  122  into the deployed position shown in  FIG. 13B , the operator preferably first advances tube  124  distally of the lesion to be fragmented. In the preferred embodiment, tube  124  has a size on the order of a guidewire, such as a 0.014 inch outer diameter. Therefore, it easily advances beyond the stenosis to be fragmented. The operator then pushes on the proximal region of tube  124  and pulls on the proximal end of mandrel  132 . This causes two things to happen. First, this causes the struts formed by slots  128  to expand radially outwardly, and carry with them, microporous membrane  130 . Thus, microporous membrane  130  forms a generally basket-shaped filter assembly which opens toward the proximal end of tube  124 . In addition, proximal expandable member  136  expands and engages protrusions  134 . This locks device  122  in the deployed and expanded position. In order to move the device  122  to the collapsed position, the physician simply pushes on mandrel  132  and pulls on the proximal end of tube  124 . This causes device  122  to return to the undeployed position shown in  FIG. 13A .  
      It should be noted that device  122  can optionally be provided with a stainless steel proximal hypotube attachment. Also, the struts defined by slots  128  can be expanded and retracted using a fluid-coupling instead of a mandrel. In other words, the proximal end of tube  124  can be coupled to a pressurizable fluid source. By making slots  128  very thin, and pressurizing the fluid, the struts expand outwardly. Further, by pulling vacuum on the pressurizable fluid, the struts collapse.  
       FIG. 14A  illustrates distal protection device  140  which is similar to that shown in  FIGS. 13A and 13B , except that the struts  142  are formed of a metal or polymer material and are completely covered by mesh  144 . Mesh  144  includes two mesh portions,  146  and  148 . Mesh portion  146  is proximal of mesh portion  148  on device  140  and is a relatively loose mesh which will allow stenosis fragments to pass therethrough. By contrast, mesh  148  is a fairly tight mesh, or a microporous membrane, (or simply loose mesh portion  146  with a microporous membrane or other suitable filter material bonded or cast or otherwise disposed thereover) which does not allow the fragments to pass therethrough and therefore captures and retains the fragments therein. The mesh portions can provide a memory set which, in the relaxed position, is either deployed or collapsed.  
       FIG. 14B  illustrates a device  150  which is similar to device  140  shown in  FIG. 14A , except struts  142  are eliminated and the two mesh portions  146 ′ and  148 ′ are simply joined together at a region  152 . Also, the two mesh portions  146 ′ and  148 ′ are not two different discrete mesh portions but are formed of the same braided mesh material wherein the braid simply has a different pitch. The wider pitch in region  146 ′ provides a looser mesh, whereas the narrower pitch in region  148 ′ provides a tighter mesh that traps the embolic material.  
       FIG. 14C  illustrates a distal protection device  160  which is similar to that shown in  FIG. 14A . However, rather than simply providing a slotted tube, distal protection device  160  includes a plurality of struts  162  on a proximal region thereof and a plurality of struts  164  on the distal region thereof. Struts  162  are spaced further apart than struts  164  about the periphery of protection device  160 . Therefore, struts  162  define openings  166  which are larger than the openings  168  defined by struts  164  and allow stenosis fragments to pass therethrough. Also, struts  164  have secured to the interior surface thereof a filter or mesh portion  170 . When deployed, filter portion  170  forms a substantially basket-shaped filter device opening toward the proximal region of tube  172 .  
       FIG. 15  illustrates the operation of another distal protection device  176 . Distal protection device  176  includes a tube  178  and a push/pull wire  180 . Tube  178  has, at the distal end thereof, a filter assembly  182 . Filter assembly  182  includes a plurality of preferably metal struts  184  which have a microporous membrane, or other suitable mesh  186  disposed thereon. Tube  178  also preferably includes end cap  188  and umbrella-like expansion structure  190  disposed at a distal region thereof. Expansion structure  190  is connected to the distal region of tube  178  and to metal struts  184  such that, when push/pull wire  180  is pulled relative to tube  178 , expansion member  190  exerts a radial, outwardly directed force on struts  184  causing them to expand radially outwardly relative to the outer surface of tube  178 . This causes microporous membrane or mesh  186  to be deployed in a manner opening toward the proximal end of tube  178  to catch embolic material. Struts  184  can also be formed of an appropriate polymer material.  
       FIGS. 16A and 16B  illustrate a protection device in accordance with another embodiment of the present invention.  FIG. 16A  illustrates distal protection device  192 . Device  192  includes guidewire  194 , actuator wire  196 , and filter assembly  198 . Filter assembly  198  includes an expandable ring  200 , such as an expandable polymer or metal or other elastic material, which has attached thereto mesh  202 . Mesh  202  is also attached to guidewire  194  distally of ring  200 . Actuator wire  196  is attached to sleeve or sheath  204  which is positioned to fit about the outer periphery of expandable ring  200 , when expandable ring  200  is in the collapsed position.  
      Thus, when sheath  204  is moved distally of expandable ring  200 , expandable ring  200  has shape memory which causes it to expand into the position shown in  FIG. 16A . Alternatively, when sheath  204  is pulled proximally by pulling actuator wire  196  relative to guidewire  194 , sheath  204  collapses ring  200  and holds ring  200  in the collapsed position within sheath  204 . Manipulating wires  194  and  196  relative to one another causes device  192  to move from the deployed position to the collapsed position, and vice versa.  
       FIG. 16B  is similar to device  192  except that, instead of having an expandable ring  200  connected at one point to wire  194 , distal protection device  206  includes expandable member  208  which is formed of an elastic coil section of wire  194 . Thus, elastic coil section  208  has a shape memory which causes it to expand into the generally helical, conical shape shown in  FIG. 16B . However, when sheath  204  is pulled proximally relative to expandable member  208 , this causes sheath  204  to capture and retain expandable member  208  in a collapsed position. When sheath  204  is again moved distally of expandable member  208 , expandable member  208  returns to its expanded position shown in  FIG. 163  carrying with it mesh  210  into a deployed position. In the preferred embodiment, sheath  204  is formed of a suitable polymer material and expandable member  208  and expandable ring  200  are preferably formed of Nitinol.  
       FIGS. 17A and 17B  illustrate the operation of another distal protection device  212 . Protection device  212  includes guidewire  214  and filter assembly  216 . In the preferred embodiment, filter assembly  216  includes a wire braid portion  218  which extends from a distal region of guidewire  214  proximally thereof. Braid portion  218  is formed of braided filaments or fibers which have a shape memory causing them to form a deployed, basket-shaped filter, such as that shown in  FIG. 17A , in the unbiased position. Braided portion  218  terminates at its proximal end in a plurality of eyelets  220 . One or more cinch wires  222  are preferably threaded through eyelets  220 . By pushing on guidewire  214  and pulling on cinch wires  222 , the operator is able to cinch closed, and pull proximally, the proximal portion of mesh  218 . This causes mesh  218  to collapse tightly about the outer surface of wire  214 .  
      Therefore, during operation, the operator holds mesh  218  in the collapsed position and inserts protection device  212  distally of the desired stenosis. The operator then allows cinch wire  222  to move distally relative to guidewire  214 . This allows mesh  218  to open to the deployed position shown in  FIG. 17A  which has an outer diameter that approximates the inner diameter of the lumen within which it is disposed. Filter assembly  216  is then disposed to capture embolic material from blood flowing therethrough. Once the embolic material is captured, the operator again moves cinch wire  222  proximally relative to guidewire  214  to collapse filter assembly  216  and capture and retain the embolic material in filter assembly  216 . The device  212  is then removed.  
       FIG. 17B  shows distal protection device  212  except that in the embodiment shown in  FIG. 17B , protection device  212  is not disposed distally of the stenosis, but rather proximally. This results, for example, in an application where the blood flow is proximal of the stenosis rather than distal. Further, in the embodiment shown in  FIG. 17B , guidewire  214  is preferably hollow and the cinch wire  222  extends through the lumen therein. By pushing on guidewire  214 , a force is exerted on mesh  218  in the distal direction. This causes cinch wire  222  to tightly close the distal opening in filter assembly  216  and to collapse mesh portion  218 . By contrast, by allowing cinch wire  222  to move distal relative to hollow guidewire  214 , mesh portion  218  expands and filter assembly  216  is deployed as shown in  FIG. 17B .  
       FIGS. 18A and 18B  illustrate a distal protection device  250  in accordance with another aspect of the present invention. Device  250  includes inner wire  252  and outer tube  254 . In the preferred embodiment, inner wire  252  is a core wire and outer tube  254  has a lumen  256  therein large enough to accommodate longitudinal movement of inner wire  252  therein. Also, in the preferred embodiment, inner wire  252  has, coupled to its distal end  258 , a spring tip  260 .  
      Device  250  includes expandable mesh or braid portion  262 . Expandable portion  262  has a proximal end  264  which is attached to the distal end  266  of tube  254 . Also, expandable member  262  has a distal end  268  which is attached to the distal end  258  of inner wire  252 .  
      Expandable member  262  is preferably a mesh or braided material which is coated with polyurethane. In one preferred embodiment, a distal portion of expandable member  262  has a tighter mesh than a proximal portion thereof, or has a microporous membrane or other suitable filtering mechanism disposed thereover. In another preferred embodiment, expandable member  262  is simply formed of a tighter mesh or braided material which, itself, forms the filter.  FIG. 18A  illustrates device  250  in a collapsed, or insertion position wherein the outer diameter of mesh portion  262  closely approximates the outer diameters of either inner wire  252  or outer tube  254 .  
       FIG. 18B  illustrates device  250  in the deployed position in which expandable member  262  is radially expanded relative to the collapsed position shown in  FIG. 18A . In order to deploy device  250 , the outer tube  254  is moved distally with respect to inner wire  252  such that the distal ends  266  and  258  of wires  254  and  252  move longitudinally toward one another. Relative movement of ends  266  and  258  toward one another causes the mesh of expandable member  262  to buckle and fold radially outwardly. Thus, the outer diameter of expandable member  262  in the deployed position shown in  FIG. 18B  closely approximates the inner diameter of a vessel within which it is deployed.  
       FIG. 18C  illustrates device  250  in a partially collapsed position. In  FIG. 18C , the distal end  266  of outer tube  254  and the distal end  258  of inner wire  252  are moved even closer together than they are as shown in  FIG. 18B . This causes expandable mesh portion  262  to fold over itself and form a rolling, proximally directed flap  270 . As longitudinal movement of inner wire  252  proximally with respect to outer tube  254  continues, mesh portion  262  continues to fold over itself such that the rolling flap portion  270  has an outer radial diameter which continues to decrease. In other words, expandable mesh portion  262  continues to fold over itself and to collapse over the outer periphery of outer tube  254 .  
       FIG. 18D  illustrates device  250  in a fully collapsed position in which it retains emboli captured therein. In  FIG. 18D , the distal end  266  of outer tube  254  has been advanced as far distally as it can relative to the distal end  258  of inner wire  252 . This causes expandable mesh portion  262  to fold all the way over on itself such that it lies against, and closely approximates the outer diameter of, outer tube  254 . Device  250  thus captures any emboli filtered from the vessel within which it was deployed, and can be removed while retaining that embolic material.  
       FIG. 19  illustrates device  280  which depicts a further aspect in accordance with the present invention. Device  280  includes outer tube  282 , core wire  284 , transition tube  286 , movable plunger  288 , expandable member  290 , fixed collar  292  and bias member  294 .  
      In the preferred embodiment, tube  282  comprises a proximal hypotube which is coupled to a plunger that selectively provides fluid under pressure through an inflation lumen  296 . Inner wire  284  is preferably a tapered core wire which terminates at its distal end in a spring coil tip  298  and which is coupled at its proximal end  300  to transition tube  286 . Transition tube  286  is preferably an outer polymer sleeve either over hypotube  282 , or simply disposed by itself and coupled to a hypotube  282 . Transition tube  286  is capable of withstanding the inflation pressure provided by the fluid delivered through the inflation lumen  296 .  
      Movable collar  288  is preferably slidably engageable with the interior surface of transition tube  286  and with the exterior surface of core wire  284 , and is longitudinally movable relative thereto. Slidable collar  288  has, attached at its distal end, bias spring  294  which is preferably coiled about core wire  284  and extends to fixed collar  292 . Fixed collar  292  is is preferably fixedly attached to the exterior surface of a distal portion of core wire  284 .  
      Expandable member  290  is preferably formed, at a proximal portion thereof, of either discrete struts, or another suitable frame (such as a loose mesh) which allows blood and embolic material to flow therethrough. The proximal end  302  of expandable member  290  is coupled to a distal region of movable collar  288 . The distal portion of expandable member  290  is preferably formed of a filtering material which is suitable for allowing blood flow therethrough, but which will capture embolic material being carried by the blood.  
      In one preferred embodiment, spring  294  is biased to force collars  288  and  292  away from one another. Thus, as spring  294  urges collars  288  and  292  away from one another, collar  288  retracts within transition tube  286  pulling expandable member  290  into a collapsed position about core wire  284 . However, in order to deploy collapsible member  290  as shown in  FIG. 19 , the operator preferably actuates a plunger (not shown) which delivers pressurized fluid through lumen  296 . The pressurized fluid enters transition tube  286  and travels about the outer periphery of inner core wire  284 , thus forcing movable collar  288  to move distally along core wire  284 . This overcomes the spring force exerted by spring  294  thus causing collars  288  and  292  to move toward one another, relatively. This motion causes expandable member  290  to buckle and expand outwardly to the deployed position shown in  FIG. 19 .  
      Expandable member  290  is collapsed by releasing the pressure applied through lumen  296  (i.e., by causing the plunger to move proximally). This allows spring  294  to again urge collars  288  and  292  away from one another to collapse expandable member  290 . In an alternative embodiment, the frame supporting expandable member  290  is imparted with a memory (such as a heat set, or a thermally responsive material which assumes a memory upon reaching a transition temperature) such that the resting state of the frame supporting expandable member  290  is in a collapsed position. This eliminates the need for spring  294 . The expandable member  290 , in that preferred embodiment, is expanded using the hydraulic pressure provided by the pressurized fluid introduced through lumen  296 , and it is collapsed by simply allowing the memory in expandable member  290  to force fluid from transition tube  286  back through lumen  296 .  
       FIGS. 20A and 20B  illustrate another aspect in accordance with the present invention. A device  310  includes a mesh portion  312  supported by a frame  314 . Expansion of frame  314  to the radially expanded position shown in  FIG. 20A  is driven by an expandable member, such as a balloon,  316  which is coupled to frame  314 . Balloon  316  is coupled to a distal end of a distal hypotube  318 , which is formed of a suitable material, such as nitinol. It should be noted that the distal tip of hypotube  318  includes a spring tip  320 .  
      Distal hypotube  318  is shown coupled to a proximal hypotube  322  which has a tapered portion  324  therein. In the preferred embodiment, proximal hypotube  322  is formed of a suitable material, such as stainless steel. A plunger  326  is longitudinally movable within the lumen of both proximal hypotube  322  and distal hypotube  318 .  
      Frame  314 , and consequently mesh portion  312 , are deployed by the operator moving plunger  326  distally within the lumens of hypotubes  318  and  322 . This causes pressurized fluid to enter balloon  316 , thereby inflating balloon  316  and driving deployment of frame  314  and mesh  312 . In order to collapse frame  314  and mesh  312 , the operator preferably moves plunger  326  proximally within the lumens of tubes  318  and  322  to withdraw fluid from within balloon  316 . Alternatively, mesh  312  or frame  314  can have a memory set which is either in the inflated or collapsed position such that the operator need only affirmatively move frame  314  and mesh  312  to either the deployed or collapsed position, whichever is opposite of the memory set.  
      In either case, it is desirable that the operator be able to lock plunger  326  in a single longitudinal position relative to hypotubes  318  and  322 . Thus, device  310  includes a locking region  328 .  
       FIG. 20B  illustrates locking region  328  in greater detail.  FIG. 20B  illustrates that, in locking region  328 , plunger  326  has a plurality of grooves  330  formed in the outer radial surface thereof. Also, in accordance with the present invention,  FIG. 20B  illustrates that one of hypotubes  318  or  322  has an inwardly projecting portion  332 . In one preferred embodiment, inwardly projecting portion  332  includes an inwardly extending, deflectable, annular rim which extends inwardly from either hypotube  318  or  322 . In another preferred embodiment, the inwardly projecting portion  332  includes a plurality of discrete fingers which extend inwardly from one of hypotubes  318  or  322  and which are angularly displaced about the interior periphery of the corresponding hypotube  318  or  322 .  
      In operation, as the operator advances plunger  326  distally within the lumens of hypotubes  318  and  322 , inwardly projecting portion  332  rides along the exterior periphery of plunger  326  until it encounters one of grooves  330 . Then, inwardly projecting portion  332  snaps into the groove  330  to lock plunger  326  longitudinally relative to tubes  318  and  322 .  
      It should be noted that, in the preferred embodiment, both inwardly projecting portions  332  and grooves  330  are formed such that, when gentle pressure is exerted by the operator on plunger  326  relative to hypotubes  318  and  322 , projection portions  332  follow the contour of grooves  330  up and out of grooves  330  so that plunger  326  can again be freely moved within the lumens of hypotubes  318  and  322 . Thus, the relative interaction between projecting portions  332  and grooves  330  provides a ratcheting type of operation wherein plunger  326  can be releasably locked into one of a plurality longitudinal positions relative hypotubes  318  and  322 , since a plurality of grooves  330  are provided. Plunger  326  can be moved back and forth longitudinally within the lumens of hypotubes  318  and  322  in a ratcheting manner and can be locked into one of a plurality of relative longitudinal positions because there are a plurality of grooves  330  in the exterior of plunger  326 . It should also be noted, however, that in another preferred embodiment, a plurality of sets of inwardly projecting portions  332  are provided along the inner longitudinal surface of hypotubes  318  and/or  322 . In that case, only a single groove  330  needs to be formed in the exterior surface of plunger  326 ; and the same type of ratcheting locking operation is obtained.  
      In the preferred embodiment, at least the exterior of hypotubes  318  and  322 , and preferably the exterior of plunger  326 , are tapered. This allows device  310  to maintain increased flexibility. It should also be noted that, in the preferred embodiment, hypotubes  318  and  322  are preferably sized as conventional guidewires.  
       FIG. 21A  illustrates a protection device in accordance with another embodiment of the present invention.  FIG. 21A  illustrates distal protection device  340 . Device  340  is similar to devices  192  and  206  shown in  FIGS. 16A and 16B . However, in the preferred embodiment, device  340  includes hoop-shaped frame  342 , filter portion  344 , and wire  346 . Hoop-shaped frame  342  is preferably a self-expanding frame formed of a wire which includes a shape memory alloy. In a more preferred embodiment hoop-shaped frame  342  is formed of a nitinol wire having a diameter in a range of approximately 0.002-0.004 inches.  
      Filter portion  344  is preferably formed of a polyurethane material having holes therein such that blood flow can pass through filter  344 , but emboli (of a desired size) cannot pass through filter  344  but are retained therein. In one preferred embodiment, filter material  344  is attached to hoop-shaped frame  342  with a suitable, commercially available adhesive. In another preferred embodiment, filter  344  has a proximal portion thereof folded over hoop-shaped frame  342 , and the filter material is attached itself either with adhesive, by stitching, or by another suitable connection mechanism, in order to secure it about hoop-shaped frame  342 . This connection is preferably formed by a suitable adhesive or other suitable connection mechanism.  
      Also, the distal end of filter  344  is preferably attached about the outer periphery of wire  346 , proximate coil tip  348  on wire  346 .  
      In one preferred configuration, filter  344  is approximately 15 mm in longitudinal length, and has a diameter at its mouth (defined by hoop-shaped frame  342 ) of a conventional size (such as 4.0 mm, 4.5 mm, 5 mm, 5.5 mm, or 6 mm). Of course, any other suitable size can be used as well.  
      Also, in the preferred configuration, filter  344  is formed of a polyurethane material with the holes laser drilled therein. The holes are preferably approximately 100 μm in diameter. Of course, filter  344  can also be a microporous membrane, a wire or polymer braid or mesh, or any other suitable configuration.  
      Wire  346  is preferably a conventional stainless-steel guidewire having conventional guidewire dimensions. For instance, in one embodiment, wire  346  is a solid core wire having an outer diameter of approximately 0.014 inches and an overall length of up to 300 cm. Also, in the preferred embodiment, wire  346  has a distal end  350 , in a region proximate filter  344 , which tapers from an outer diameter at its proximal end which is the same as the outer diameter of the remainder of wire  346 , to an outer diameter of approximately 0.055 inches at its distal end. At distal region  350 , guidewire  346  is preferably formed of stainless steel  304 .  
      Of course, other suitable guidewire dimensions and configurations can also be used. For example guidewires having an outer diameter of approximately 0.018 inches may also be used. For other coronary applications, different dimensions may also be used, such as outer diameters of approximately 0.010-inches to 0.014 inches. Further, it will be appreciated that the particular size of wire  346  will vary with application. Applications involving neural vasculature will require the use of a smaller guidewire, while other applications will require the use of a larger guidewire. Also, wire  346  can be replaced by a hollow guidewire, or hypotube of similar, or other suitable dimensions.  
      In addition, in order to make wire  342 , hoop  346 , or filter  344  radiopaque, other materials can be used. For example, radiopaque loaded powder can be used to form a polyurethane sheath which is fitted over wire  346  or hoop  342 , or which is implemented in filter  344 . Also, hoop  342  and wire  346  can be gold plated in order to increase radiopacity. Also, marker bands can be used on wire  346  or filter  344  to increase the radiopacity of the device.  
      In operation, hoop  342  (and thus filter  344 ) is preferably collapsed to a radially contracted position which more closely approximates the outer diameter of wire  346 . Methods of performing this contraction are described later in the specification. Once retracted to a more low profile position, wire  346  is manipulated to position hoop  342  and filter  344  distal of a restriction to be treated. Then, the restraining force which is used to restrain hoop  342  in the predeployment, low profile position is removed, and the superelastic properties of nitinol hoop  342  (or the shape memory properties of another shape memory alloy) are utilized in allowing hoop  342  to assume its shape memory position. This causes hoop  342  to define a substantially lumen filling mouth to filter  344  which is positioned distal of the restriction to be treated.  
      A suitable dilatation device is then advanced over wire  346  and is used to treat the vascular restriction. Emboli which are carried by blood flow distal of the restriction are captured by filter  344 . After the dilatation procedure, filter  344 , along with the emboli retained therein, are retrieved from the vasculature. Various retrieval procedures and devices are described later in the specification.  
      By allowing hoop-shaped frame  342  to be unattached to wire  346 , and only connected to wire  346  through filter  344  (or other super structure used to support filter  344 ), wire  346  is allowed to substantially float within hoop  342 . This configuration provides some advantages. For instance, hoop  342  can better follow the vasculature without kinking or prolapsing (i.e., without collapsing upon itself). Thus, certain positioning or repositioning of filter  344  can be accomplished with less difficulty.  
       FIG. 21B  illustrates a protection device  352  in accordance with another embodiment of the present invention. Protection device  352  is similar to protection device  340 , and similar items are similarly numbered. However, rather than having simply a hoop-shaped frame  342  to support filter  344 , and drive filter  344  into its expanded and deployed position, device  352  includes frame  354  which includes a hoop-shaped portion  356 , and a pair of tails  358  and  360 .  
      Tails  358  and  360  extend proximally from hoop-shaped portion  356  to an attachment region  362 . In the preferred embodiment, tails  358  and  360  are attached to wire  346  at attachment region  362  by soldering, welding, brazing, adhesive, or any other suitable attachment mechanism. In the embodiment shown in  FIG. 21B , attachment sleeve  364 , formed of a weldable material, is attached at its inner periphery to tails  358  and  360 . Sleeve  364  is then attached, using welding or brazing, to wire  346 .  
      By providing tails  358  and  360 , frame  354  is directly connected to wire  346 . However, tails  358  and  360  are provided so that the point of attachment of frame  354  to wire  346  is located several millimeters proximal of hoop-shaped portion  356 . This provides some additional structural integrity to frame  354 , but still allows frame  354  to substantially float about wire  346  in the region of hoop-shaped frame portion  356 .  
       FIG. 21C  illustrates a protection device  366  in accordance with another embodiment of the present invention. Protection device  366  is similar to protection devices  340  and  352  shown in  FIGS. 21A and 21B , and similar items are similarly numbered. However, device  366  includes hoop-shaped frame  368 . Frame  368  is similar to frame  342  shown in  FIG. 21A . However, unlike frame  342 , hoop  368  does not allow wire  346  to float freely therein. Instead, hoop  368  is directly attached to wire  346  at attachment point  370 . This causes hoop-shaped frame  368  and filter  344  to reside eccentrically about wire  346 .  
       FIGS. 22A-22C  illustrate one preferred embodiment for delivering one of devices  340 ,  352  and  366 . For the sake of clarity, only device  352  is illustrated in  FIGS. 22A-22C .  
       FIG. 22A  illustrates delivery device  372 . In the preferred embodiment, delivery device  372  includes proximal hub  374 , shaft  376 , and distal retaining section  378 . Also, in one preferred embodiment, device  372  also includes marker band  380 . In the preferred embodiment, delivery device  372  is similar to a conventional balloon catheter in that proximal hub  374  is a conventional hub, and shaft  376  is a conventional balloon catheter shaft. Further, distal retaining section  378  is preferably a conventional angioplasty balloon having an inflated diameter of approximately 1.5-2.0 millimeters, but having its distal end cutoff such that the distal end  382  of balloon  378  is open.  
      Prior to insertion of device  372  into the vasculature, hoop-shaped frame  354  is retracted into its low profile deployment position and is withdrawn through end  382  into balloon  378 . Then, the distal end of balloon  378  is exposed to heat to heat shrink or heat set the distal end of balloon  378  around the radially retracted device  352 . Device  372 , including device  352 , is then inserted in the vasculature either through a preplaced guide catheter, along with a guide catheter, or simply without a guide catheter utilizing coil tip  348 .  
      In any case, once device  372  is properly placed such that balloon  378  is located distal of the restriction to be treated, distal protection device  352  is then removed from within heat collapsed balloon  378 . In one preferred embodiment, the physician simply accomplishes longitudinal movement of wire  346  relative to catheter  376 . For instance, the physician may simply hold wire  346  longitudinally in place and withdraw catheter  376  proximally relative to wire  346  by pulling on hub  374 . This causes balloon  378  to move proximally relative to device  352 , and thereby to expose device  352  to the vasculature.  
       FIG. 22B  illustrates another preferred embodiment for removing device  352  from within balloon  378 . In the embodiment shown in  FIG. 22B , syringe  384 , which contains fluid, is inserted into coupling  386  in hub  374 . The physician then introduces pressurized fluid into the lumen of catheter  376 . The pressurized fluid advances down the lumen of catheter  376  to the distal end where it encounters collapsed balloon  378 . The pressure exerted on balloon  378  by the pressurized fluid causes balloon  378  to open radially. Then, the physician withdraws catheter  376  relative to device  352  thereby exposing device  352  to the vasculature.  
      In any case, once device  352  is no longer restrained by balloon  378 , device  352  assumes its shape memory position in the vasculature, as illustrated in  FIG. 22C . Thus, device  352  substantially forms a lumen-filling basket or filter which allows blood to pass distally therethrough, but which retains or captures embolic material carried by the blood flow. The physician then simply removes device  372  from the vasculature, leaving device  352  in place during subsequent procedures. In one preferred embodiment, shaft  376  includes a predefined slit or score from a region just proximal of marker band  380  to, or through, hub  374 . Thus, as the physician removes device  372 , it can be peeled away from device  352 . Also, or alternatively, device  372  can be provided with an aperture in shaft  376  near its distal end. The proximal end of wire  346  will thus lie outside of shaft  376 . Wire  346  can enter shaft  376  through the aperture and extend through the distal end of shaft  376 . This also facilitates easier withdrawal of device  372  over wire  346 .  
       FIGS. 23A-23E  illustrate one preferred embodiment for retrieving one of the devices  340 ,  352  and  366  described in  FIGS. 21A-21C . For the sake of clarity, only device  352  is illustrated in  FIGS. 23A-23E .  FIG. 23A  illustrates retrieval device  388 . Retrieval device  388  is preferably formed of proximal shaft  390 , mesh portion  392 , and end cap  394 . Items  390 ,  392  and  394  preferably each have lumens therein to define a passageway for receiving wire  346 . Also, wire  346  may optionally be provided with an positive stop  396  (which can be embodied as a radiopaque marker band). Optional stop  396  may also simply be an annular ring attached to wire  346  proximate to filter  344 , or may be any other suitable stop.  
      Proximal shaft  390  is preferably simply a polymer or nitinol tube sized and configured to track over wire  346 . End cap  394  is also preferably formed to track over wire  346 , but also contains radiopaque material to serve as a distal marker band for retrieval device  388 . Mesh  392  is preferably a braid or mesh formed of wire or polymer material having sufficient flexibility that it can be deflected as described below.  
      Mesh  392  preferably has a proximal end coupled to proximal shaft  390 , by adhesive, welding, or other suitable attachment mechanisms. Mesh  392  also preferably includes a distal end connected to end cap  394 , also by a suitable connection mechanism.  
      In order to retrieve filter  344 , which likely contains embolic material, device  388  is inserted in the low profile position shown in  FIG. 23A , over wire  346 , to a position proximate filter  344 . Then, device  388  is advanced toward filter  344 , until end cap  394  abuts positive stop  396 , or the hoop-shaped frame  354 . Continued advancement of proximal shaft  390  relative to wire  346  causes compression of mesh  392 . This results in a radial expansion of an intermediate portion of mesh  392  (between the proximal and distal ends of mesh  392 ). The radial expansion of mesh portion  392  is illustrated in  FIG. 23B .  
      By continuing to advance proximal shaft  390  relative to wire  346 , the intermediate portion of mesh  392  is configured to bend over on itself such that it is axially displaced toward filter  344 , in the direction generally indicated by arrows  398  in  FIG. 23C . In the preferred embodiment, mesh  392  is sized and configured such that, with continued advancement of proximal shaft  390  relative to wire  346 , this action continues as shown in  FIGS. 23D and 23E  until the intermediate portion of mesh  392  encompasses at least the mouth of filter  344 . Also, in the preferred embodiment, the intermediate portion of mesh  392 , when driven as described above, engages and contracts the mouth of filter  344  to a lower profile position, such as that shown in  FIG. 23E . In yet another preferred embodiment, mesh  392  is sized and configured to substantially engulf the entire filter  344 .  
      Once at least the mouth of filter  344  is encompassed by mesh  392 , device  388 , along with device  352 , are simply withdrawn from the vasculature. In one preferred embodiment in which a guide catheter is used, devices  388  and  352  are simply withdrawn either into the guide catheter and the guide catheter is removed with those devices, simultaneously, or devices  388  and  352  are removed from the guide catheter prior to removal of the guide catheter. In another preferred embodiment, in which no guide catheter is used, devices  388  and  352  are simply removed from the vasculature simultaneously.  
      It will also be appreciated, of course, that rather than providing device  388  with a single proximal tube  390  and end cap  394 , a second actuation tube or wire can also be provided which is attached to end cap  394 , and which extends back through the lumen in proximal tube  390  and is longitudinally movable relative to proximal shaft  390 . In that way, the actuation wire or elongate member can be used to pull cap  394  closer to the distal portion of proximal shaft  390  in order to accomplish the action illustrated in  FIGS. 23A-23E . This feature is also illustrated in  FIGS. 18A-18D  which illustrate the mesh portion folded proximally rather than distally.  
       FIGS. 24A-24C  illustrate another preferred embodiment in accordance with the present invention, for retrieving any of the distal protection devices  340 ,  352  or  366  shown in  FIGS. 21A-21C . For the sake of clarity, only device  352  is illustrated in  FIGS. 24A-24C .  
       FIG. 24A  illustrates retrieval device  400 . Retrieval device  400  preferably includes retrieval sheath  402 , proximal locking device  404 , dilator sheath  405 , and nose cone  406 . In the preferred embodiment, retrieval sheath  402  is preferably formed of polyether block amide (PEBAX) material having an outer diameter of approximately six French (i.e., approximately 2 mm) and having a shore D hardness of approximately 40. Also, retrieval sheath  402  preferably has a wall thickness of approximately 0.004 inches. Dilator sheath  405 , and nose cone  406 , are preferably formed of low density polyethylene, or high density polyethylene. Sheath  405  preferably has an outer diameter which is approximately equal to the inner diameter of sheath  402 . In addition, the inner diameter of sheath  405  and nose cone  406  is preferably just large enough to fit over, and track over, wire  346 . Nose cone  406  preferably has a proximal portion which is either attached to, or formed integrally with, sheath  405 . The outer diameter of the proximal portion of nose cone  406  is also approximately the same as the outer diameter of sheath  405 . However, nose cone  406  also preferably has a distal portion which tapers, or reduces along preferably a smooth curve, to an outer diameter which terminates at the inner diameter of nose cone  406 .  
      Proximal locking device  404  is preferably any suitable, and commercially available, locking device which can be configured to lock dilator sheath  405  to guidewire  346 .  
      In order to retrieve device  352  from the vasculature, device  400  is preferably advanced over guidewire  346  to a position shown in  FIG. 24B , in which the distal portion of nose cone  406  is closely proximate, or adjacent to, either optional stop  396  or the mouth of filter  344 . Then, proximal locking device  404  is actuated to lock dilator sheath  405  to wire  346  so that wire  346  and dilator sheath  405  (as well as nose cone  406 ) can be moved as a unitary piece.  
      Next, wire  346  (and hence dilator sheath  405  and nose cone  406 ) are withdrawn longitudinally relative to retrieval sheath  402 . This causes the mouth of filter  344  to enter within the distal opening in retrieval sheath  402 . This results in device  352  being positioned relative to sheath  402  as shown in  FIG. 24C . Of course, wire  346 , dilator sheath  405  and nose cone  406  can be withdrawn further into sheath  402  such that the entire filter  344 , and wire tip  348 , are disposed within the lumen of sheath  402 .  
      In any case, once at least the mouth of filter  344  is within sheath  402 , device  352  is configured to be removed from the vasculature. This can be accomplished by either removing dilator sheath  405 , nose cone  406  and device  352  as a unitary piece, leaving sheath  402  in place for later removal, or by removing sheath  402  with the remainder of the system, either through a guide catheter or simply through the vasculature, simultaneously. Also, where a guide catheter is used, device  352  and device  400  can be removed through the guide catheter leaving the guide catheter in place, or the guide catheter can be removed simultaneously with the other devices  352  and  400 .  
      It should be noted that all of the devices according to the present invention can optionally be coated with an antithrombotic material, such as heparin (commercially available under the tradename Duraflow from Baxter), to inhibit clotting.  
      Thus, in accordance with one preferred embodiment of the present invention, the superelastic properties of nitinol are used to form a frame at least in the area of the mouth of the distal protection filter. Thus, the distal protection device can be deployed, retrieved, and re-deployed any number of times without incurring plastic deformation. In addition, in other preferred embodiments in accordance with the present invention, various deployment and retrieval techniques and systems are provided which address various problems associated with such systems.  
      Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.