Patent Publication Number: US-10772649-B2

Title: Clot retrieval catheter

Description:
CROSS REFERENCE 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 14/842,268 filed on Sep. 1, 2015, which is hereby incorporated by reference. U.S. patent application Ser. No. 14/842,268 is a non-provisional application claiming priority to U.S. Provisional Patent Application No. 62/044,512 filed Sep. 2, 2014. Which is also hereby incorporated by reference. 
    
    
     BACKGROUND 
     The field of the present invention relates to devices to remove a thrombus from an intraluminal passage. Intravenous devices are commonly used during thrombectomies to remove a thrombus from blocking blood flow through an intraluminal passage. Frequently, an aspirator is brought to the blockage area to collect the thrombus by suction. However, aspirator catheters typically have a large cross-section and may be difficult to use in narrow intraluminal passages, particularly within the brain. 
     In such procedures, it is desirable to retrieve the thrombus or embolism and bring it to a wider area of the intraluminal passage for removal by an aspirator catheter. Several devices exist to accomplish this purpose, such as a wire within a catheter which deploys into a coil. However, these devices are difficult to maneuver to the desired intraluminal passage because of the tortuous angles within such area of vasculature and because the devices cannot be adequately steered to the site of the thrombus. Additionally, often the thrombus cannot be adequately contained within the device during retraction. If the thrombus fragments or escapes from the device during retraction, the thrombus or a portion of the thrombus may cause a blockage elsewhere in the vasculature causing significant harm to the patient. 
     It is desirable for a clot retrieval device to exist which has a small cross-sectional profile which can also be adequately steered to the clot within narrow intraluminal passages. Furthermore, it is desirable that such a device be capable of adequately capturing and containing the clot during retraction through the intraluminal passage. 
     SUMMARY 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     In one form of the present disclosure, a clot retrieval device is provided comprising an outer catheter comprising a distal end and a lumen through the distal end. The device further comprises an elongated member comprising an outer surface and a distal portion. The elongated member is configured to pass through the at least one lumen of the outer catheter and is movable relative to the outer catheter between an extended position and a compressed position. The device further comprises a knitted basket comprising a proximal end coupled to the distal portion of the elongated member. When the elongated member is in the extended position, the knitted basket is adjacent to the outer surface of the elongated member. When the elongated member is moved to the compressed position, at least a portion of the knitted basket expands radially from the outer surface of the elongated member. The knitted basket is comprised of a plurality of wires coupled together by a plurality of windings comprising one of the plurality of wires twisted about another of the plurality of wires. 
     In another form of the present disclosure, a clot retrieval device is provided comprising a catheter comprising a proximal end, a distal end, and a lumen through the distal end. The device further comprises an elongated member comprising an outer surface, a lumen, a proximal end, and a distal portion. The elongated member is configured to pass through the lumen of the catheter and is movable relative to the catheter between an extended position and a compressed position. The device further comprises a wire guide configured to pass through the lumen of the elongated member, and an expandable knitted basket comprising a proximal end coupled to the distal end of the catheter and a distal end coupled to the distal portion of the elongated member. The device further comprises an actuator comprising a first member coupled to the proximal end of the elongated member and a second member coupled to the proximal end of the elongated member. The actuator is configured to move the elongated member between the extended position and the compressed position. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       The invention may be more fully understood by reading the following description in conjunction with the drawings, in which: 
         FIGS. 1A-1C  are side plan views of a clot retrieval device, showing an outer catheter, an inner elongated member and a knitted basket; 
         FIGS. 2A-2C  are side plan views of a clot retrieval device, showing the device in an intraluminal passage alongside a thrombus; 
         FIG. 3  is a partial cross-sectional view of a clot retrieval device, showing an outer catheter, an inner elongated member, and a knitted basket which transitions to a several pairs of helical wires; 
         FIGS. 4A-4G  are side plan views of knitted baskets, showing several possible configurations for the structure of a knitted basket; 
         FIG. 5A  is a close-in, plan view of a knitted basket, showing a winding between two wires. 
         FIG. 5B  is a close-in, plan view of a twisted pair of wires in a continuous twist. 
         FIG. 6A  is a side plan view of a clot retrieval device, showing an outer catheter, an inner elongated member, and a knitted basket which includes proximal and distal coverings; 
         FIG. 6B  is a cross-sectional axial view of a clot retrieval device, showing an inner elongated member, a plurality of wires and a folded covering; 
         FIG. 7  is a side plan view of a clot retrieval system, showing an intraluminal passage, a thrombus, a clot retrieval device, and an inflatable aspirating sheath; 
         FIG. 8  is a partial cross-sectional view of a clot retrieval device, showing a plurality of knitted baskets, an outer catheter, an inner catheter, and an elongated member; 
         FIG. 9A  is a side plan view of an actuator for a clot retrieval device, showing the movement of a button in relation to a casing; 
         FIG. 9B  is a cross-sectional view of an actuator for a clot retrieval device, showing a button within a slot, and a sledge; 
         FIGS. 10A-10D  are partial cross-sectional views of an actuator for a clot retrieval device, showing the method of operation between an outer slidable member and an inner slidable member. 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     Referring now to the drawings, and particularly to  FIGS. 1A-1C , a clot retrieval device  22  is shown comprising a catheter  10  having at least one lumen  38  through the distal end  34  (shown in  FIG. 3 ), an elongated member  16  which is configured to pass through the lumen  38  of the catheter  10 , and a knitted basket  14  having a proximal end coupled to the distal end  34  of the catheter  10  and a distal end coupled to the distal portion  18  of the elongated member  16 . 
     The elongated member  16  is movable relative to the catheter  10  between a longitudinally extended position (shown in  FIG. 1A ) and a longitudinally compressed position (shown  FIG. 1C ). In the extended position, the distal portion  18  of the elongated member  16  is farthest from the distal end  34  of the catheter  10 . In the compressed position, the distal portion  18  of the elongated member  16  is closest to the distal end  34  of the catheter  10 . When the elongated member  16  is in the extended position relative to the catheter  10 , the basket  14  is adjacent to or rests on the outer surface of the elongated member  16 . As the elongated member  16  moves to the compressed position relative to the catheter  10 , the basket  14  expands radially from the outer surface of the elongated member and compresses in length. 
     The distal portion  18  of the elongated member  16  may also include an atraumatic tip  20 . This atraumatic tip may take the form of a simple rounded end, as shown in  FIGS. 1A-1C  or in the form of a flexible, floppy tip. The atraumatic tip  20  ensures that the device  22  may be used in a narrow intraluminal passage  28  without damaging the walls  26  of the intraluminal passage  28 . 
     The elongated member  16  may also comprise a braid within the interior of the elongated member  16 . The braid within the elongated member  16  may comprise Nitinol wire and extend the entire length of the elongated member  16  or may be included only in the portions of the elongated member  16  which are configured to extend beyond the catheter  10 . The braid may extend into the distal portion  18  of the elongated member and may be connected to a portion of the wires  32  extending into the distal portion  18  by twisting, braiding, or welding. 
     The device  22  may also comprise a collar  12  coupled to the elongated member  16  so that, when the elongated member  16  is in the compressed position, the collar  12  is adjacent to or rests against the distal end  34  of the catheter  10 . The collar  12  may be sized to be larger than the lumen  38  of the catheter  10  so that the collar  12  cannot be retracted into the catheter  10 . When the collar  12  is moved against the distal end  34  of the catheter  10 , the elongated member  16  may be prevented from being proximally moved beyond the compressed position. Alternatively, the collar  12  may take the form of any other projection which would prevent retraction into the lumen  38  of the catheter  10 . 
     Additionally, the collar  12  may be used to monitor the positions of the elongated member  16  and the basket  14  using radioscopy. The device  22  may also comprise two radiopaque markers at the proximal and distal ends of the basket  14  to show the position of the basket within the intraluminal passage  28 . The proximal marker may be coupled to the distal end  34  of the catheter  10  and the distal marker may be coupled to the distal portion  18  of the elongated member  16 . When the elongated member  16  is moved towards the compressed position, the movement of the markers may be observed through radioscopy to indicate the position of the elongated member  16  relative to the catheter  10 . If the collar  12  is also radiopaque, the operator may observe that the elongated member  16  is in the compressed position when the collar  12  is adjacent to the proximal marker. 
     Alternatively, a portion of the elongated member  16  may be comprised of a radiopaque material and used in conjunction with the markers to determine the positions of the elongated member  16  and the basket  14  using radioscopy. When the elongated member  16  is in the compressed position, and the basket  14  has been radially expanded, a portion of the elongated member  16  is exposed and outside of the catheter  10 . This portion of the elongated member  16  may be made of a radiopaque material so that the operator may observe that the elongated member  16  is in the compressed position when the radiopaque portion of the elongated member  16  is adjacent to or overlapping with the proximal marker. 
     As another alternative, all or a portion of the wires  32  comprising the knitted basket  14  may be made from a radiopaque material, may have a radiopaque core, or may have a radiopaque coating applied to the wire  32 . The radiopaque material may be platinum, gold, iridium, or any other alloy which is opaque to under radioscopy, such as DFT Wire manufactured by Fort Wayne Metals. A single wire  32  or a plurality of wires  32  in the knitted basket  14  which are radiopaque may ease the ability of an operator to position and operate the clot retrieval device  22  while using radioscopy. 
     The device  22  may also comprise at least one support wire  24  having a first end coupled to the elongated member  16  and a second end coupled to the basket  14 . The first end is arranged proximally to the second end so that, as the basket  14  expands radially, the support wire  24  will contribute proximal force to the knitted basket  14 , assisting in compressing the length of the basket  14  evenly as the basket  14  expands radially. More than one support wire  24  may be desired depending on the length of the basket  14 . 
     Referring to  FIGS. 2A-2C , a possible embodiment of the clot retrieval device  22  is shown within an intraluminal passage  28 .  FIG. 2A  shows the device  22  with the elongated member  16  in the extended position, with the knitted basket  14  adjacent to the outer surface of the elongated member  16 . In this position, the device  22  can more easily be positioned within the intraluminal passage  28 , and can pass through or around the thrombus  30  or blockage. 
     As shown in  FIG. 2B , once the distal end of the elongated member has passed through or around the thrombus  30  so that the knitted basket  14  overlaps at least a portion of the thrombus  30 , the inner elongated member  16  is moved to the compressed position. As the knitted basket  14  begins to expand radially in response to the movement of the elongated member  16 , the wires  114  that comprise the knitted basket  14  pass through or around the thrombus  30  and may reach the walls  26  of the intraluminal passage  28 . 
     As shown in  FIG. 2C , once the elongated member  16  is in the compressed position and the knitted basket  14  has been fully expanded, the thrombus  30 , or a portion of the thrombus  30 , will be contained within the knitted basket  14 . From this configuration, the clot retrieval device  22  may be retracted to remove the thrombus  30  from the intraluminal passage  28 . 
     Referring to  FIG. 3 , a partial cross-sectional view of the clot retrieval device  22  is shown. In this embodiment, the knitted basket  14  is comprised of a plurality of wires  114  which are embedded in both the catheter  10  and the distal portion  18  of the elongated member  16 . Although it is not readily apparent from the illustration of  FIG. 3  that the wires  32  are formed into helical wires  32  in a continuous braided twist within the catheter wall  36  and the distal portion  18  of the elongated member  16 , it is preferable for the helical wires  32  to be braided or twisted together within these embedded portions. Furthermore, the wires  32  embedded in the catheter wall  36  spiral around the catheter  10  as shown in  FIG. 3 . Between the distal end  34  of the catheter  10  and the distal portion  18  of the elongated member  16 , the wires  114  extend in a knitted pattern to form the knitted basket  14 , although the knitting of the wires  114  may not be apparent from the embodiment shown in  FIG. 3 . Although the embodiment shown in  FIG. 3  shows only two helical wires  32 , the clot retrieval device  22  may have many helical wires  32  which separate to be integrated into the knitted basket  14 . Alternatively, the wires  114  may be embedded within the catheter  10  without twisting, simply wrapping around within the walls  36  of the catheter  10  to the distal end  34  where the knitted basket  14  begins. The helical wires  32  are distinguished from the wires  114  in the knitted basket  14  in that the helical pairs  118  of wires  32  are continuously braided or twisted together so as to be adjacent to one another, never separating until transitioning to individual wires  114  to be incorporated into the knitted basket  14 . Within the walls  36  of the catheter  10 , it may be desirable for the wires  32  to extend the entire length of the catheter  10 , from the proximal end to the distal end  34  of the catheter  10 . 
     The wires  32  may have three stages of interaction depending upon their position along the catheter  10 . Within the catheter  10 , the wires  32  may be configured in a first stage comprising a braid, crossing over and under one another in as they circle about the catheter wall  36 . The wires  32  in this first stage may have a flat cross-sectional shape to reduce their cross-sectional area. As the wires  32  extend from the distal end  34  of the catheter  10 , but before the knitted basket  14 , the wires  32  may be configured in a second stage comprising a continuous twist (Example in  FIG. 5B , Reference Number  162 ). If the cross-sectional shape of the wire  32  changes between the first and second stage of the wires  32 , the wires  32  may be welded together inside or outside the catheter  10 . If the catheter  10  includes a radiopaque marker at the distal end  34  of the catheter  10 , the wires may transition from the first stage configuration to the second stage configuration under the radiopaque marker. The wires  32  are also configured in a third stage comprising the knitted basket  14 . The wires  32  may return to the second stage configuration and first stage configuration as the wires  32  extend distally beyond the knitted basket  14  and into the distal portion  18  of the elongated member  16 . 
     The distal portion  18  of the elongated member  16  may have a different diameter and may be made of a different material than the rest of the elongated member  16 . For ease of manufacture, it may be desirable that the distal portion  18  of the elongated member  16  have a similar diameter as the catheter  10 . If the distal portion  18  is a different diameter than the rest of the elongated member  16 , then the elongated member  16  may be embedded within the distal portion  18  to secure it in place. 
     The catheter wall  36  may comprise an inner layer which defines the lumen  38  of the catheter  10 . The inner layer of the catheter wall may comprise a material such as PTFE. The wires  32  formed in a braid may be positioned on this inner layer. Additionally, a polymer may be applied to the inner layer and the wires  32  to form the outer surface of the catheter  10 . The polymer may cover the first braided stage of the wires  32  entirely, filling in any gaps which may exist within the braid. 
     In  FIGS. 4A-4G , eight possible embodiments of the knitted basket  14  are shown. These embodiments in no way comprise a complete list of possible embodiments, but only illustrate how various embodiments of the knitted basket  14  may be configured. All of the embodiments of the knitted basket  14  shown in  FIGS. 4A-4G  share some common elements. The knitted baskets  14  comprise a plurality of helical pairs  118  of wires  114  on the proximal and distal ends of the knitted basket  14 . These helical pairs  118  comprise a continuous wrapping of the two component wires  114  around each other. Between the proximal and distal ends of the knitted basket  14 , the helical pairs  118  of wires  114  separate into individual wires  116  which are integrated into the structure of the knitted basket  14 . In the knitted basket  14 , a individual wires  116  separate so that each wire  114  forms a series of interconnected windings  106 . The interaction of these wires  114  form empty cells  110 ,  124 ,  130 ,  140 ,  148 ,  149  having a cell width  104 ,  122 ,  128 ,  138 ,  146 ,  152  when the knitted basket  14  is in its radially expanded position. 
     Each cell is comprised of four wires  114 , a first pair  164  and a second pair  166 , and four windings  106 , a first winding  168 , a second winding  170 , and two side windings  172 . The designation of each of the wire pairs  164 ,  166  and windings  106  are entirely dependent upon the individual cell  110 ,  124 ,  130 ,  140 ,  148 ,  149 . A first pair  164  for one cell  110 ,  124 ,  130 ,  140 ,  148 ,  149  will form the second pair  166  for a different cell  110 ,  124 ,  130 ,  140 ,  148 ,  149 . Similarly each side winding  172  will also be a first winding  168  and a second winding  170  depending on the cell  110 ,  124 ,  130 ,  140 ,  148 ,  149 . 
     From the first winding  106 , the first pair of wires  164  separate from the first winding  168  towards respective side windings  172  on either side of the cell  110 ,  124 ,  130 ,  140 ,  148 ,  149 . The first pair of wires  164  proceed from the first winding  168  at a first angle  102 ,  120 ,  134 ,  136 ,  144  relative to the axis of the device&#39;s  22  movement within the intraluminal passage  28 , a longitudinal axis. Similarly, the second pair of wires  164  converges toward the second winding  170  from respective side windings  172 . The second pair of wires  166  converges on the second winding  170  at a second angle  103 ,  121 ,  135 ,  137 ,  144  relative to the axis of the device&#39;s  22  movement within the intraluminal passage  28 , the longitudinal axis. These first and second angles  102 ,  103 ,  120 ,  121 ,  134 ,  135 ,  136 ,  138 ,  144 , along with the radially expanded knitted basket  14  diameter  112  determines the cell  110 ,  124 ,  130 ,  140 ,  148 ,  149  shape and the radially expanded knitted basket length  108 ,  126 ,  132 ,  142 ,  150 ,  154 ,  156 . 
     In determining the design of the knitted basket  14 , several considerations may be taken into account. For example, the radial force that knitted basket  14  exerts as it expands is important to ensure that the wires  114  are forceful enough to pass through the thrombus  30 . Additionally, the size of the cells  110 ,  124 ,  130 ,  140 ,  148 ,  149  formed by the knitted wires  114  in the knitted basket&#39;s  14  radially expanded position should be considered. If the cell width  104 ,  122 ,  128 ,  138 ,  146 ,  152  is too wide, the thrombus  30  may not be contained within the knitted basket  14  during retraction. However, if the wires  114  in the knitted basket  14  are spaced too closely together, creating very small cell width  104 ,  122 ,  128 ,  138 ,  146 ,  152 , the thrombus  30  may fragment during the radial expansion of the knitted basket  14 . 
     The length of the basket  14  in its expanded form may also be considered to ensure that the thrombus  30  can be contained within the knitted basked  14 . The ratio of the lengths of the knitted basket  14  between its extended position over its radially expanded position may be another consideration. A high length ratio may allow for smaller cells  110 ,  124 ,  130 ,  140 ,  148 ,  149  to better capture the thrombus  30 , however the knitted basket  14  may also require one or more support wires  24  to evenly expand. A small length ratio may allow for a shorter device  22  and easier radial expansion, but it may also create larger cells  110 ,  124 ,  130 ,  140 ,  148 ,  149  by which the thrombus  30  may escape during retraction. 
     The design of the knitted basket may also consider the effect of the knitted basket  14  while moving against the walls  26  of the intraluminal passage  28 . During retraction of the knitted basket  14 , the device  22  has a much larger cross-sectional profile as the knitted basket  14  is radially expanded. This may cause irritation or damage as the knitted basket  14  scrapes against the walls  26  of the intraluminal passage  28 . To reduce the irritation to the walls  26  of the intraluminal passage  28 , it may be desirable to utilize a basket  14  with wires  114  which, when the knitted basket  14  is radially expanded, form cells  110 ,  124 ,  130 ,  140 ,  148 ,  149  with wires  114  at small angles  102 ,  120 ,  134 ,  136 ,  144  relative to the axis of the device&#39;s  22  movement within the intraluminal passage  28 , the longitudinal axis. Wires  114  on the knitted basket  14  which are oriented at high angles or perpendicular to the movement of the device  22  within the intraluminal passage  28  may cause more irritation to the walls  26  of the intraluminal passage  28 . 
       FIG. 4A  shows a knitted basket  14  wherein each cell  110  comprises a first pair of wires  164  and a second pair of wires  166  having a first and a second angle  102 ,  103  at or near 90 degrees. These angles angle  102 ,  103  results in cell  110  shapes which are roughly rectangular and have a very narrow cell width  104 . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 200% longer than the length  108  of the radially expanded knitted basket  14 . 
       FIG. 4B  shows a knitted basket  14  wherein each cell  124  comprises a first pair of wires  164  having a first angle  120  at or near 55 degrees, and a second pair of wires  166  having a second angle  121  at or near 90 degrees. These angles  120 ,  121  result in a cell  124  shape which is nearly triangular, with a wider cell width  122  than the cell  110  shape shown in  FIG. 4A . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 90% longer than the length  126  of the radially expanded knitted basket  14 . 
       FIG. 4C  shows a knitted basket  14  wherein each cell  130  comprises a first pair of wires  164  having a first angle  134  at or near 40 degrees, and a second pair of wires  166  having a second angle  135  at or near 90 degrees. These angles  134 ,  135  result in a cell  130  shape which is nearly triangular, with a wider cell width  128  than the cell  124  shape shown in  FIG. 4B . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 50% longer than the length  132  of the radially expanded knitted basket  14 . 
       FIG. 4D  shows a knitted basket  14  wherein each cell  140  comprises a first pair of wires  164  having a first angle  136  at or near 35 degrees, and a second pair of wires  166  having a second angle  137  at or near 90 degrees. These angles  136 ,  137  result in a cell  140  shape which is nearly triangular, with a wider cell width  138  than the cell  130  shape shown in  FIG. 4C . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 30% longer than the length  142  of the radially expanded knitted basket  14 . 
       FIG. 4E  shows a knitted basket  14  wherein each cell  148  comprises a first pair of wires  164  and a second pair of wires  166  having identical angles  144  at or near 55 degrees. This results in a cell  148  shape which is nearly diamond-shaped, with a wider cell width  122  than the cell  124  shape shown in  FIG. 4B  but a shorter cell width  122  than the cell  130  shown in  FIG. 4C . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 90% longer than the length  150  of the radially expanded knitted basket  14 . 
       FIG. 4F  shows a knitted basket  14  comprising wires  114  at varying angles  120 ,  121 ,  134 ,  135 ,  136 ,  137  to create cell  124 ,  130 ,  140  shapes which having an increasing cell width  122 ,  128 ,  138  as the cells approach the center of the knitted basket  14 . In the embodiment shown, the knitted basket  14  has one set of cells  124  similar to those shown in  FIG. 4B  on both the proximal and distal end of the knitted basket  14 . Closer to the center from that layer, is an additional layer of cells  130  similar to those shown in  FIG. 4C , which are wider than the cells  124  shown in  FIG. 4B . In the center of the knitted basket  14  is a single layer of cells  140  similar to those found in  FIG. 4D , which has the widest cell width  138 . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 60% longer than the length  154  of the radially expanded knitted basket  14 . 
       FIG. 4G  shows a knitted basket similar to that shown in  FIG. 4F , wherein the cell width  122 ,  128 ,  138 ,  152  increases closer to the center of knitted basket  14 . However, unlike  FIG. 4F , the cells  124 ,  130 ,  140  are arranged in such a way to create large diamond cells  149  at the center of the knitted basket  14 , each having a very large cell width  152 , wider than any of the other cell widths  122 ,  128 ,  152 . When the knitted basket  14  is extended by the elongated member  16 , the length of the knitted basket  14  proximal to the elongated member  16  may be up to 40% longer than the length  150  of the radially expanded knitted basket  14 . 
       FIG. 5A  shows an example of a winding  106  between wires  114  in the knitted basket  14 . The configuration shown in  FIG. 5  is a double-twist winding  106 , wherein the wires  114  are twisted ( 158 ,  160 ) around each other twice, each wire  114  being twisted substantially 360 degrees. Each twist  158  alters the direction of the wires  114  substantially 180 degrees. The first twist  158  alters the direction of the wire  114  and reflects its direction, while the second twist  160  maintains each wire  114  along its original path prior to the winding  106 . Although a double-twist winding  106  is shown here, other number of windings  106  may be appropriate for various circumstances. Knitted baskets  14  consisting of fewer twists in their windings  106  will use less wire  114  length and may be more flexible. However, knitted baskets  14  with more twists in their windings  106  may be more structurally rigid, holding their shape more consistently in the extended and compressed forms. A high number of twists in each winding may, however, affect the shape of the cell,  110 ,  124 ,  130 ,  140 ,  148 ,  149 , decreasing the knitted basket&#39;s  14  ability effectively compress and expand. As a result, it may be desirable to limit windings to 5 or fewer twists. 
     Furthermore, an even number of twists in each winding  106  will result in individual wires  114  being twisted by an angle of substantially 360 degrees, 720 degrees, or some other similar angle. Such a winding  106 , when repeated on the entire knitted basket  114 , will result in the wires  114  spiraling around the circumference of the knitted basket  14 . This configuration may be desirable to give the knitted basket  14  additional stability and to prevent collapsing or kinking during radial expansion. Alternatively, an odd number of twists in each winding  106  will result in individual wires  114  being twisted by an angle of substantially 180 degrees, 540 degrees, or some similar angle. Such a winding  106 , when repeated on the entire knitted basket  14 , will result in the wires  114  reconnecting with the same individual wire  114  every other winding  106  and remaining in a circumferentially stable position along the length of the knitted basket  14 . This configuration may however be less stable and may cause kinking or collapsing of the knitted basket  14  during radial expansion, depending on the forces exerted on the wires  114  during radial expansion. 
     Referring to  FIG. 5B , an example of a helical pair  118  of wires  32  is shown in a continuous twist  162 . In contrast to the winding  106  shown in  FIG. 5A , the helical pair  118  of wires  32  are arranged in a continuous braid or twist typically comprising at least 5 consecutive twists, so that each of the helical pair  118  of wires  32  is continuously adjacent to each other. The braiding or twisting may, however, extend the entire length of the catheter  10 . The arrangement of the helical pairs  118  is advantageous since it allows the helical pairs to take up a small amount of space while spiraling within the wall  26  of the catheter  10 . After passing through the distal end  34  of the catheter  10 , however, the helical pair  118  can be separated to be integrated into the knitted basket  14 . It may be desirable that the helical pairs  118  are twisted in the same direction at the windings  106  in the knitted basket  14  to increase the stability of the knitted basket  14  and to prevent collapsing or kinking during radial expansion. For example, if the helical pairs  118  are twisted or braided together in a clockwise fashion, then it may be desirable to twist the windings  106  in in the knitted basket  14  in the same clockwise direction. 
     Referring to  FIGS. 6A and 6B , another embodiment of the clot retrieval device  62  is shown with proximal and distal coverings  56 ,  58  on the proximal and distal ends of the knitted basket  14 . The coverings may be made of a thin flexible material which is compressible. The coverings  56 ,  58  are coupled to the wires  114  of the knitted basket  14 . The proximal covering&#39;s  56  proximal side may also be coupled to the catheter&#39;s  10  distal end  34 , while distal covering&#39;s  58  distal side may also be coupled to the distal portion  18  of the elongated member  16 . When the elongated member  16  is in the extended position, the proximal and distal coverings  56 ,  58  compress so that the entire cover  56 ,  58  is adjacent to the outer surface of the elongated member  16 . When the elongated member  16  is in the compressed position, the proximal and distal coverings  56 ,  58  expand radially along with the knitted basket  14 . The coverings  56 ,  58  may be configured on the knitted basket  14  so that the portions of the coverings further from the center of the knitted basket  14  expand less than the portions closer to the center of the knitted basket. If the ends of the coverings  56 ,  58  are coupled to the catheter&#39;s  10  distal end  34  or the elongated member&#39;s  16  distal portion  18 , those ends of the coverings  56 ,  58  may not expand at all. While expanded, the coverings  56 ,  58  are effective in controlling the proximal and distal motion of the thrombus  30  which is contained within the knitted basket  14 . 
     To ensure that the cross-sectional profile of the clot retrieval device  62  is as small as possible, it may be desirable to include pre-set folds into the proximal and distal coverings  56 ,  58  by defining fold lines  60  on the surface of the coverings  56 ,  58 . It may be desirable to place these fold lines  60  off-center between the wires  114  of the knitted basket  14 , so that when the elongated member  16  is in the extended position, the proximal and distal coverings  56 ,  58  fold at the fold lines in a spiral pattern, as shown in  FIG. 6B . 
     Referring to  FIG. 7 , a clot retrieval system is shown which includes a wire guide  21 , a knitted basket  14  coupled to a catheter  10  and an elongated member  16 , an aspiration catheter  96 , and a sheath  98  which includes an inflatable member  100 . 
     For narrow or tortuous intraluminal passages  28 , it may be desirable to initially advance a wire guide  21  to the thrombus  30  because of a wire guide&#39;s smaller cross-sectional profile and steerability. As shown in  FIG. 7 , the clot retrieval device  22 , may configured to be advanced over a wire guide  21 . To accommodate a wire guide  21 , the elongated member  16  may comprise a lumen. The wire guide  21  passes through this lumen so that the clot retrieval device  22  may be advanced to the thrombus  30 . 
     Fragmentation of the thrombus  30  during retrieval may be a risk in some operations. To prevent fragmentation from causing complications to the patient, it may be desirable to include an additional sheath  98  with the clot retrieval device  22 . This sheath  98  may be advanced over the clot retrieval device  22 , or alongside the device. If the sheath  98  is to be advanced over the clot retrieval device  22 , the sheath  98  will have a first lumen which the device  22  may pass through. 
     The sheath  98  may also have a second lumen to accommodate an aspiration catheter  96 , which may use suction to collect fragmented portions of the thrombus  30  and prevent their circulation throughout the patient&#39;s body. Alternatively, the aspiration catheter  96  may also be brought in proximity of the knitted basket  14  after the capture of the thrombus  30  to safely remove the thrombus  30 . In this way, it would not be necessary to maintain the elongated member  16  in its extended position during the retraction of the clot retrieval device  22 . 
     The sheath  98  may also include an inflatable member  100  located proximally from the knitted basket  14 . This inflatable member  100  may be inflated to block the flow of blood within the intraluminal passage  28 , allowing safe retrieval of the thrombus  30  and any fragments which may result from its capture within the knitted basket  14 . The inflatable member  100  may be inflated by a third lumen within the sheath  98 . 
     In some operations, it may be desirable to have multiple knitted baskets  40 ,  42  to retrieve more than one thrombus  30 . Referring to  FIG. 8 , yet another embodiment of the clot retrieval device  50  is shown having a plurality of knitted baskets  40 ,  42 . For simplicity, the bodies of the baskets  40 ,  42  are omitted, however the design of the baskets  40 ,  42  may be similar to any of the designs discussed above. In the embodiment of  FIG. 8 , an first outer catheter  48  is shown having a second inner catheter  44  disposed within a lumen of the first outer catheter  48 . Furthermore, an elongated member  46  is disposed within a lumen of the second inner catheter  44 . The first outer catheter  48  and the second inner catheter  44  are movable between a longitudinally extended position, and a longitudinally compressed position, which controls the radial expansion of the first basket  40 . Similarly, the second inner catheter  44  and the elongated member  46 , are separately movable between a longitudinally extended position and a longitudinally compressed position, which controls the radial expansion of the second basket  42 . In this way, each knitted basket  40 ,  46  may be separately radially expanded to capture different thrombi  30  or different portions of a larger thrombus  30 . 
     The knitted baskets  40 ,  42 , shown in  FIG. 8  comprise a single set of wires  114  which run at least from the distal end of the first outer catheter  48  to the distal portion  54  of the elongated member  46 . Within the first outer catheter, the wires  114  are arranged in helical pairs  118 , which spiral within the walls of the first outer catheter  48 . Distal from the distal end of the first outer catheter  48 , the helical pairs  118  separate to be integrated into the first knitted basket  40 . Distal from the first knitted basket  40 , helical pairs  118  are reformed and are embedded within the walls of the distal end of the second inner catheter  44 . Distal from the distal end of the second inner catheter  44 , the helical pairs  118  separate to be integrated into the second knitted basket  42 . At the distal portion  54  of the elongated member  46 , the wires  114  form helical pairs  118  and are embedded within the elongated member  46 . Alternatively, the first and second baskets  40 ,  42  may comprise two unconnected sets of knitted wires  114 , however, this may increase the size and cost of manufacturing the device  50 . 
     When using the multi-basket device  50 , it may be desirable to pass through or around the first proximal thrombus with the elongated member  46  and the second inner catheter  44 , positioning at least a portion of the first proximal thrombus to overlap with the first basket  40 . The first outer catheter  48  and the second inner catheter  44  may be moved to the compressed position to radially expand the first basket  40  and capture the first proximal thrombus within. The device may then be advanced further so that the elongated member  46  passes through or around a second distal thrombus, positioning at least a portion of the second distal thrombus to overlap with the second basket  42 . The second inner catheter  44  and the elongated member  46  may then be moved to the compressed position to radially expand the second basket  42  and capture the second distal thrombus within. The device  50  may then be retracted to clear the intraluminal passage  28 . 
     Alternatively, if the thrombus  30  is too large to be retrieved with a single knitted basket  14 , the multi-basket device  50  may be used so that a proximal portion of the thrombus  30  may be captured within the first basket  40 , and the distal portion of the thrombus  30  may be captured within the second basket  42 . Similar designs could be used providing additional baskets to retrieve a larger thrombus  30  within a narrow intraluminal passage  28 . 
     Referring to  FIGS. 9A and 9B , an embodiment of an actuator  64  for controlling a clot retrieval device  22  is shown. The actuator  64  comprises a casing  70  which encircles the elongated member  16  with a button  66  protruding from the casing&#39;s outer surface. This button  66  may be moved proximally  68  to move the inner elongated member  16  from the extended position to the compressed position, causing the knitted basket  14  to radially expand. In the embodiment shown, the button  66  is coupled to a sledge  76  which is configured to move distally within a slot  74 . The sledge  76  is coupled to a stopping plate  78  which is configured to limit the proximal motion of the button. The stopping plate  78 , button  66 , or sledge  76  may be coupled to a grip  72  which is in turn coupled to the elongated member  16 . Relative movement between the catheter  10  and the elongated member  16  is achieved by embedding the proximal end of the catheter  10  within the casing  70  of the handle  64 , which ensures that the catheter&#39;s  10  position is unchanged when the button is moved proximally or distally. Additionally, an introducer  80  may be included on the proximal end of the handle  70  if a wire guide  21  is to be utilized. The wire guide  21  is placed within a lumen of the introducer  80 , which is configured to enter into a lumen of the elongated member  16 . 
     The radially expansion of the knitted basket  14  may be finely controlled by movement of the button  66  proximally or distally. If the knitted basket  14  is being expanded within a very narrow intraluminal passage  28 , there may not be sufficient space to fully expand the knitted basket  14 . The operator may track the expansion and placement of the basket  14  through a method such as fluoroscopy and use the button  66  to adjust the expansion of the basket  14  to capture the thrombus  30  without straining the walls  26  of the intraluminal passage. Once captured, the thrombus  30  may be partially retracted to a position within the intraluminal passage  28  where the basket  14  may be fully radially expanded. 
     During manufacture of the device  22 , it may be desirable to heat set the knitted basket  14  in the radially expanded or the radially unexpanded position. In this way, the knitted basket  14  will exert a force to return to that position. If the basket  14  is heat set in the radially expanded position, there may be a slight constant proximal force on the button  66  which the operator would have to overcome. Similarly, if the basket  14  is heat set in the radially unexpanded position, the knitted basket  14  may exert a slight distal force on the button  66 . In such a design, once deployed, the operator would have to exert a proximal force to maintain the radial expansion of the knitted basket  14  and could release the thrombus  30  by releasing the button  66 . 
     Referring to  FIGS. 10A-10D , another embodiment of a handle  82  for operating a clot retrieval device  22  is shown. The handle  82  shown comprises an inner slidable member  90  and an outer sleeve  84 . The outer sleeve  84  encircles the elongated member  16  and has a plurality of inwardly projecting members  92  arranged in a straight line along the longitudinal axis of the device. The inner slidable member  90  extends from the proximal end of the outer sleeve  84  and comprises a cavity  86  at least large enough to accommodate the inwardly projecting members  92  of the outer sleeve  84 . The cavity  86  is arranged on the outer surface of the slidable member  90  and is defined by a region of increased separation between the outer surface of the slidable member  90  and the inner surface of the outer sleeve  84 . The inner slidable member  90  also comprises at least one engaging member  94  projecting into a portion of the cavity  86 , and at least one control surface  88  on the distal portion of the inner slidable member  90 . 
     The outer sleeve  84  is coupled to the catheter  10  of the clot retrieval device  22 . The inner slidable member  90  is coupled to the elongated member  16 , so that moving the inner slidable member  90  relative to the outer sleeve  84 , moves the elongated member  16  relative to the catheter  10  between the extended position and the compressed position.  FIGS. 10A-10C  show the handle  82  when the elongated member  16  is in the compressed position. To adjust the position of the elongated member  16  to the extended position, the slidable member is advanced distally. 
     The handle  82  allows the operator to finely adjust and lock the position of the elongated member  16  and the radial expansion of the knitted basket  14 . The handle is in the locked position in  FIG. 10C , with the elongated member in the compressed position. In this position, the inwardly projecting members  92  of the outer sleeve  84  overlap with the engaging members  94  within the cavity  86  of the inner slidable member  90 . To unlock the handle  82 , the inner slidable member  90  may be rotated relative to the outer sleeve  84  so that the inwardly projecting members  92  no longer overlap with the engaging member  94  within the cavity  86 . In this position, the inner slidable member  90  may be advanced as need by the operator to change the position of the elongated member  16  and the radial expansion of the knitted basket  14 , as shown in  FIG. 10D . Once the position is reached, the handle  82  may be locked by rotating the inner slidable member  90  relative to the outer sleeve  84  so that the inwardly projecting members  92  again overlap with the engaging members  94  within the cavity  86 . 
     Accordingly, it is now apparent that there are many advantages of the invention provided herein. In addition to the advantages that have been described, it is also possible that there are still other advantages that are not currently recognized but which may become apparent at a later time. 
     While preferred embodiments of the invention have been described, it should be understood that the invention is not so limited, and modifications may be made without departing from the invention. The scope of the invention is defined by the appended claims, and all devices that come within the meaning of the claims, either literally or by equivalence, are intended to embrace them.