Abstract:
An embolic filter having a filter support frame with a collapsed and an expanded configuration and a collapsible filter body supported by the support frame. The filter body has inlet and outlet ends. The filter body includes a proximal section having a longitudinally extending cylindrical shape and a distal section having a longitudinally extending conical shape that tapers in the distal direction. The support frame includes a plurality of alternating first segments such that, when the support frame is in the expanded configuration, the alternating first segments circumferentially extend in a first zigzag path to support the proximal, cylindrically shaped section of the filter body. The support frame includes a plurality of alternating second segments such that, when the support frame is in the expanded configuration, the alternating second segments circumferentially extend in a second zigzag path to support the proximal, cylindrically shaped section of the filter body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of U.S. application Ser. No. 11/534,004, filed Sep. 21, 2006, which is a continuation of U.S. application Ser. No. 10/379,434, filed Mar. 5, 2003 (now U.S. Pat. No. 7,144,408), which claims the benefit of U.S. Provisional Application No. 60/361,340, filed Mar. 5, 2002, each of which is incorporated herein by reference in its entirety. 
     
    
     INTRODUCTION 
       [0002]    This invention relates to a transvascular embolic protection system for safely capturing and retaining embolic material released during an interventional procedure while maintaining blood flow. 
         [0003]    Embolic protection systems of this general type are described in our published international patent applications WO 01/80776 and WO 01/80777. 
         [0004]    There is an economical and clinical need to provide an embolic protection system which will be easy and convenient for a clinician to prepare for use, to deploy and to retrieve. In addition there is a need to provide such a system which is suitable for use with standard medical equipment and will facilitate a wide range of clinical procedures to be carried out. 
       STATEMENTS OF INVENTION 
       [0005]    According to the invention, there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter;
       the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature;   the filter at least in the collapsed configuration having a guidewire lumen defined at least partially therethrough for passing the filter over a guidewire;   wherein the guidewire lumen is defined by a lumen-defining member which is movable or removable reactive to the filter.       
 
         [0009]    In one embodiment, the lumen-defining member is a substantially tubular member. 
         [0010]    In one embodiment, the tubular member has a slit extending the length thereof for removal of the member from a guidewire. 
         [0011]    In another embodiment, the lumen-defining member comprises a portion of a delivery system. 
         [0012]    Preferably the lumen-defining member comprises a pusher element of the delivery system, the pusher being movable from an extended lumen-defining configuration for loading of a filter to a retracted configuration for deployment of the filter. 
         [0013]    According to another aspect of the invention, there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter;
       the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature in apposition with a vasculature wall;   in the outwardly extended configuration the filter exerting an outward radial force on a vasculature wall sufficient to retain the filter in position against substantial longitudinal movement.       
 
         [0016]    In one embodiment, the filter comprises a filter body and a filter support frame to support the filter body in the outwardly extended configuration in apposition with a vasculature wall, the filter support frame providing the outward radial force. 
         [0017]    In one embodiment, the filter comprises a low-friction outer layer. 
         [0018]    Preferably the outer layer is of a hydrophilic material. 
         [0019]    In one embodiment, the filter comprises an inflatable member to enhance the outward radial force. 
         [0020]    In another embodiment, the filter defines a guidewire lumen for passing the filter over a guidewire. 
         [0021]    In one embodiment, the filter comprises an anchor for fixing the filter to the vasculature in the deployed configuration. 
         [0022]    In another embodiment, the filter comprises a filter body and a filter support frame to support the filter body in the deployed configuration. 
         [0023]    In one embodiment, the support frame comprises the anchor. 
         [0024]    In one embodiment, the filter body comprises the anchor. 
         [0025]    In another embodiment, the anchor comprises a plurality of anchor elements. 
         [0026]    In one embodiment, the anchor elements are spaced-apart circumferentially around the filter when the filter is in the deployed configuration. 
         [0027]    In one embodiment, the support frame comprises at least one support hoop. 
         [0028]    In another embodiment, the support frame has a longitudinal aspect. 
         [0029]    In a further embodiment, the filter is self supported in a vasculature in the absence of a guidewire. 
         [0030]    According to another aspect of the invention, there is provided an embolic protection filter assembly for deployment in a vasculature, the assembly comprising:—
       a filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; and   a receiver to guide a docking device into association with the filter.       
 
         [0033]    In one embodiment, the filter has a guidewire lumen for passing the filter over a guidewire, and the receiver is configured to guide a guidewire into the guidewire lumen. 
         [0034]    In one embodiment, the guidewire lumen extends only partially through the filter. 
         [0035]    In another embodiment, the receiver is configured to guide a coupling member towards the filter for coupling to the filter. 
         [0036]    In one embodiment, the receiver comprises a funnel. 
         [0037]    In another embodiment, the funnel is movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for guiding a docking device. 
         [0038]    In one embodiment, the funnel is biased towards the outwardly extended configuration. 
         [0039]    In another embodiment, the funnel comprises a funnel body and a funnel support to support the funnel body in the outwardly extended configuration. 
         [0040]    In one embodiment, the funnel body comprises a membrane. 
         [0041]    In a further embodiment, the funnel support comprises a plurality of pivotable fingers. 
         [0042]    Preferably the receiver comprises an approach channel. 
         [0043]    In one embodiment, the channel is provided by a lumen in a catheter. 
         [0044]    In another embodiment, the receiver is mounted to the filter. 
         [0045]    In one embodiment, the receiver is detachably mounted to the filter. 
         [0046]    In another embodiment, the receiver is separate from the filter. 
         [0047]    In a further embodiment, the receiver has means to space the receiver from the wall of a vasculature. 
         [0048]    Preferably the spacing means comprises an inflatable member to engage the wall of a vasculature. 
         [0049]    In one embodiment, the receiver is at least partially provided by a wall of the filter. 
         [0050]    In another embodiment, the receiver is at least partially provided by a wall of the filter at the inlet end of the filter. 
         [0051]    In a further embodiment, the receiver is at least partially provided by a wall of the filter at the outlet end of the filter. 
         [0052]    In one embodiment, the receiver extends proximally of the inlet end of the filter. 
         [0053]    In another embodiment, the receiver is located distally of the inlet end of the filter. 
         [0054]    In a further embodiment, the receiver is radially offset from the longitudinal axis of the filter. 
         [0055]    According to another aspect of the invention there is provided, an embolic protection system comprising:—
       an embolic protection filter assembly as claimed in any of claims  21  to  43 ; and   a docking device which may be guided by the receiver into association with the filter.       
 
         [0058]    In one embodiment, the docking device comprises a guidewire. 
         [0059]    In one embodiment, the docking device comprises a coupling member. 
         [0060]    According to another aspect of the invention, there is provided an embolic protection filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter;
       the filter having a guidewire aperture for passing the filter over a guidewire; and   the filter comprising a seal to seal the guidewire aperture.       
 
         [0063]    Preferably the seal is self-closing. 
         [0064]    In one embodiment, the seal is located at a proximal end of the filter, and/or at a distal end of the filter. 
         [0065]    In one embodiment, the filter has a tubular member extending from the guidewire aperture to define a guidewire lumen through the tubular member. 
         [0066]    In another embodiment, the tubular member extends through at least part of the filter. 
         [0067]    In one embodiment, the tubular member is radially offset from the longitudinal axis of the filter. 
         [0068]    In one embodiment, the seal is an annular member around the guidewire aperture, the annular member being closable down to seal the guidewire aperture. 
         [0069]    Preferably the annular member is a tube. 
         [0070]    In one embodiment, the annular member comprises a soft membrane. 
         [0071]    In one embodiment, the annular member comprises two or more circumferentially overlapping flaps. 
         [0072]    According to a further aspect of the invention, there is provided a retrieval catheter for retrieving a medical device deployed in a vasculature, the catheter comprising:—
       an outer catheter body; and   an inner coupling member having means for coupling to a medical device deployed in a vasculature;   the catheter body being movable distally relative to the coupling member to retrieve a coupled medical device into the catheter body.       
 
         [0076]    In one embodiment, the coupling means comprises a male or female member on the coupling member for engagement with a corresponding female or male member on the medical device. 
         [0077]    In one embodiment, the male member is movable between a low-profile configuration and an outwardly protruding configuration. 
         [0078]    In one embodiment, the male member is biased towards the outwardly protruding configuration. 
         [0079]    In another embodiment the male member is of a resilient material. 
         [0080]    Preferably the coupling means is substantially arrow-head shaped. 
         [0081]    In one embodiment, the male member is in the form of a hook for hooking around a female member on the medical device. 
         [0082]    In one embodiment, the male member is in the form of a hook for hooking around a tether arm on the medical device. 
         [0083]    In one embodiment, the tether arm is at a proximal end of the medical device. 
         [0084]    In another embodiment, the tether arm is located within the medical device. 
         [0085]    In one embodiment, the coupling means comprises at least one female member on the coupling member for engagement with at least one male member on the medical device. 
         [0086]    In one embodiment, the female member is in the form of a loop for looping around a protruding male member on the medical device. 
         [0087]    In one embodiment, the coupling means comprises a pair of jaws on the coupling member, the jaws being movable between an outwardly protruding configuration and a low-profile configuration to grasp the medical device. 
         [0088]    In one embodiment, the retrieval catheter comprises an actuator to move the jaws to the outwardly protruding configuration. 
         [0089]    In another embodiment, the actuator is movable longitudinally relative to the jaws to move the jaws in a camming arrangement to the outwardly protruding configuration. 
         [0090]    In a further embodiment, the jaws are biased towards the low-profile configuration. 
         [0091]    In one embodiment, the catheter body is engageable with the jaws to move the jaws to the low-profile configuration. 
         [0092]    In another embodiment, the jaws are biased towards the outwardly protruding configuration. 
         [0093]    In a further embodiment, the coupling member is at least partially of a magnetic material for magnetic coupling to an oppositely charged magnetic portion of the medical device. 
         [0094]    In one embodiment, the retrieval catheter comprises means to axially elongate a deployed medical device to collapse the medical device to a low-profile configuration for retrieval into the catheter body. 
         [0095]    In one embodiment, the elongation means comprises a second coupling member movable relative to the first coupling member to collapse the medical device. 
         [0096]    In another embodiment, the second coupling member comprises a pusher member movable distally relative to first coupling member to engage a deployed medical device distally of the first coupling means and thereby collapse the medical device. 
         [0097]    In a further embodiment, the catheter body has a guidewire lumen extending partially therethrough for passing the catheter body over a guidewire in a rapid exchange manner. 
         [0098]    In one embodiment, the guidewire lumen is offset radially from the coupling member. 
         [0099]    According to one embodiment, there is provided a retrieval catheter for retrieving an embolic protection filter deployed in a vasculature. 
         [0100]    In another aspect of the invention there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter;
       the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature;   the filter at least in the collapsed configuration having a guidewire lumen defined at least partially therethrough for passing the filter over a guidewire;   wherein the guidewire lumen is defined by a lumen-defining member which is spaced proximally of the distal end of the filter.       
 
         [0104]    In one embodiment, the guidewire lumen is defined by a tubular member. 
         [0105]    In another embodiment, the tubular member is mounted to the filter. 
         [0106]    Preferably the filter comprises a snare engaging feature. 
         [0107]    Preferably the snare engaging feature is radiopaque. 
         [0108]    In another aspect the invention provides a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       providing a collapsible embolic protection filter having a collapsed configuration for delivery of the filter, and a deployed configuration;   advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   deploying the filter distal to the treatment location;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval device;   engaging the filter with the retrieval device independent of the guidewire; and   withdrawing the retrieval device and the filter from the vasculature.       
 
         [0117]    In one case, after crossing a treatment location with the guidewire the embolic protection device is introduced over the guidewire. 
         [0118]    In one case, the deployed filter is retained independent of the guidewire against substantial longitudinal movement. 
         [0119]    In another case, the filter applies a radial force to the vasculature to substantially prevent movement of the filter relative to the vasculature in the deployed configuration. 
         [0120]    In one case, the filter in the deployed configuration is anchored to the vasculature. 
         [0121]    In one case, the method comprises the step of releasing the filter from the vasculature before retrieving the filter. 
         [0122]    In another case, the filter is simultaneously released and retrieved by moving a retrieval catheter distally relative to the filter. 
         [0123]    In one case the filter is released prior to retrieving the filter. 
         [0124]    In one case, the method comprises the step of axially elongating the filter to release the filter. 
         [0125]    According to another aspect the method comprises the steps of:— 
         [0126]    withdrawing the guidewire from the filter and/or the desired treatment location; and 
         [0127]    subsequently placing a guidewire in the filter. 
         [0128]    In one case, the same guidewire is placed in the filter. 
         [0129]    In another case, another guidewire is placed in the filter. 
         [0130]    In one case, the interventional device is introduced over the guidewire for carrying out the interventional procedure. 
         [0131]    In one case, the interventional procedure comprises a stenting of the treatment location. 
         [0132]    In another case, the interventional procedure comprises a balloon angioplasty procedure at the treatment location. 
         [0133]    According to another aspect the invention provides a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   introducing over the guidewire a collapsible embolic protection filter having a collapsed configuration for delivery of the filter, and a deployed configuration;   deploying the filter distal to the treatment location;   the filter in the deployed configuration being retained in apposition with the vasculature independent of the guidewire against substantial longitudinal movement;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval device;   engaging the filter with the retrieval device; and   withdrawing the retrieval device and the filter from the vasculature.       
 
         [0143]    In one case, on the filter applies a radial force to the vasculature to substantially prevent movement of the filter relative to the vasculature in the deployed configuration. 
         [0144]    Preferably the filter in the deployed configuration is anchored to the vasculature. 
         [0145]    In one case, the filter is engaged with the retrieval device independent of the guidewire. 
         [0146]    According to another aspect the method comprises the step of releasing the filter from the vasculature before retrieving the filter. 
         [0147]    According to a further aspect, the retrieval device is a retrieval catheter and the filter is simultaneously released and retrieved by moving the retrieval catheter distally relative to the filter. 
         [0148]    In one case, the filter is released prior to retrieving the filter. 
         [0149]    According to one aspect, the method comprises the step of axially elongating the filter to release of the filter. 
         [0150]    Preferably the method comprises the steps of:—
       withdrawing the guidewire from the filter and the desired treatment location; and   subsequently placing a guidewire in the filter.       
 
         [0153]    According to a one aspect, the same guidewire is placed in the filter. 
         [0154]    According to a another aspect, another guidewire is placed in the filter. 
         [0155]    In one case, the interventional device is introduced over the guidewire for carrying out the interventional procedure. 
         [0156]    Preferably the interventional procedure comprises a stenting of the treatment location. 
         [0157]    According to one aspect, the interventional procedure comprises a balloon angioplasty procedure at the treatment location. 
         [0158]    According to a further aspect a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       providing a collapsible embolic protection filter having a collapsed configuration for delivery of the filter, and a deployed configuration;   advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   deploying the filter distal to the treatment location;   withdrawing the guidewire from the filter and/or the desired treatment location; and   subsequently placing a guidewire in the filter;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval device;   engaging the filter with the retrieval device; and   withdrawing the retrieval device and the filter from the vasculature.       
 
         [0169]    In one case, the same guidewire is placed in the filter. 
         [0170]    In another case, another guidewire is placed in the filter. 
         [0171]    In one case the interventional device is introduced over the guidewire for carrying out the interventional procedure. 
         [0172]    In another case, the interventional procedure comprises a stenting of the treatment location. 
         [0173]    In one case, the interventional procedure comprises a balloon angioplasty procedure at the treatment location. 
         [0174]    In one case, the filter is engaged with the retrieval device independent of the guidewire. 
         [0175]    In another case, after crossing a treatment location with the guidewire the embolic protection device is introduced over the guidewire. 
         [0176]    Preferably the deployed filter is retained independent of the guidewire against substantial longitudinal movement. 
         [0177]    In one case, on deployment, the filter applies a radial force to the vasculature to substantially prevent movement of the filter relative to the vasculature in the deployed configuration. 
         [0178]    In one case, the filter in the deployed configuration is anchored to the vasculature. 
         [0179]    In one case, the method comprises the step of releasing the filter from the vasculature before retrieving the filter. 
         [0180]    In another case, the filter is simultaneously released and retrieved by moving a retrieval catheter distally relative to the filter. 
         [0181]    In another case, the filter is released prior to retrieving the filter. 
         [0182]    According to one aspect, the method comprises the step of axially elongating the filter to release the filter. 
         [0183]    According to a further aspect the invention provides a method of retrieving a medical device from a vasculature, the method comprising the steps of:—
       advancing a retrieval catheter through a vasculature until a distal end of the retrieval catheter is proximally of the deployed medical device;   axially elongating an element of the medical device to collapse the medical device; and   moving the retrieval catheter distally relative to the collapsed medical device to retrieve the medical device into the retrieval catheter.       
 
         [0187]    In one case, the method comprises the steps of:— 
         [0188]    engaging a first coupling member with the element of the deployed medical device; 
         [0189]    engaging a second coupling member with the element of the deployed medical device; and 
         [0190]    moving the coupling members relative to one another to axially elongate the element of the medical device. 
         [0191]    According to another aspect of the invention, there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter;
       the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature;   the filter at least in the collapsed configuration having a guidewire lumen defined at least partially therethrough for passing the filter over a guidewire;   wherein the tubular member is shortenable upon movement of the filter from the collapsed configuration to the extended configuration.       
 
         [0195]    In one embodiment, the tubular member comprises at least two telescopable tubes. 
         [0196]    According to another aspect of the invention, there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter;
       the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature;   the filter at least in the collapsed configuration having a guidewire lumen defined at least partially therethrough for passing the filter over a guidewire; wherein the filter comprises a support structure, in the collapsed configuration the support structure forming a tubular member to define the guidewire lumen.       
 
         [0199]    According to another aspect the invention provides a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   introducing over the guidewire a collapsible embolic protection filter having a collapsed configuration for delivery and withdrawal of the filter, and a deployed configuration;   deploying the filter distal to the treatment location;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval catheter;   fixing an abutment to the guidewire;   engaging the guidewire abutment with the filter to prevent movement of the filter distally of the guidewire abutment;   collapsing the filter and retrieving the filter into the retrieval catheter and with it the captured embolic material; and   withdrawing the retrieval catheter and the collapsed filter from the vasculature.       
 
         [0210]    In one case, the abutment is fixed to the guidewire during deployment of the filter. 
         [0211]    In another case, the abutment is fixed to the guidewire before advancing the guidewire through the vasculature. 
         [0212]    According to another aspect of the invention there is provided a retrieval catheter for retrieving a medical device deployed in a vasculature, the catheter comprising:—
       a first coupling member having means for coupling to a medical device deployed in a vasculature; and   a second coupling member having means for coupling to the deployed medical device;   the coupling members being relatively movable to axially elongate the medical device and collapse the medical device.       
 
         [0216]    In one embodiment, the catheter comprises an outer catheter body movable distally relative to the coupling members to retrieve a collapsed medical device into the catheter body. 
         [0217]    According to another aspect of the invention, there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; and
       the filter comprising an inflatable member to exert an outward radial force on a vasculature wall sufficient to retain the filter in position against substantial longitudinal movement.       
 
         [0219]    According to a further aspect of the invention there is provided an embolic protection filter system comprising:— 
         [0220]    a collapsible embolic protection filter having a collapsed configuration for delivery of the filter, and a deployed configuration; and 
         [0221]    a snare for engaging the filter. 
         [0222]    In one embodiment, the filter has a snare engaging feature for engagement by the snare. 
         [0223]    In one embodiment, the filter comprises a support frame and the snare engaging feature is provided by or on the support frame. 
         [0224]    Preferably the snare is radiopaque at least in a region of engagement with a filter. 
         [0225]    In one embodiment, the snare engaging feature is radiopaque. 
         [0226]    In another embodiment, the snare comprises a snaring hoop. 
         [0227]    According to a further aspect the invention provides a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       providing a collapsible embolic protection filter having a collapsed configuration for delivery of the filter, and a deployed configuration;   advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   deploying the filter distal to the treatment location;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a snare;   engaging the snare with the filter; and   withdrawing the snare and the filter.       
 
         [0236]    In one case, the filter has a snare engaging feature and the snare is engaged with the snare engaging feature. 
         [0237]    In another case, the snare engaging feature is provided on or by a support frame of the filter. 
         [0238]    In one case, the method comprises the steps of leading the snare into engagement with the snare engaging feature of the filter and monitoring the engagement of the filter with the snare. 
         [0239]    In one case, the snare and/or snare engaging features are radiopaque for external monitoring of the engagement. 
         [0240]    In one case, the snare is engaged with the filter independent of the guidewire. 
         [0241]    In another case, after crossing a treatment location with the guidewire the embolic protection device is introduced over the guidewire. 
         [0242]    According to the invention, there is provided a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   introducing over the guidewire a collapsible embolic protection filter having a collapsed configuration for delivery and withdrawal of the filter, and a deployed configuration;   deploying the filter distal to the treatment location;   the filter in the deployed configuration being in apposition with the vasculature so that the filter is retained in position against substantial longitudinal movement, on deployment in the vasculature;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval catheter;   collapsing the filter and retrieving the filter at least partially into the retrieval catheter and with it the captured embolic material; and   withdrawing the retrieval catheter and the collapsed filter from the vasculature.       
 
         [0252]    In one embodiment of the invention the method comprises the step of releasing the apposition of the filter with the vasculature before collapsing the filter. 
         [0253]    The filter may be simultaneously collapsed and retrieved into the retrieval catheter by moving the retrieval catheter distally relative to the filter. 
         [0254]    Alternatively the filter may be collapsed prior to retrieving the filter into the retrieval catheter. Preferably the method comprises the step of axially elongating the filter to collapse the filter. 
         [0255]    Desirably the method comprises the step of engaging a part of the retrieval catheter with the filter to aid collapsing of the filter. 
         [0256]    In one case the method comprises the steps of:—
       withdrawing the guidewire from the filter and the desired treatment location; and   crossing the desired treatment location with another guidewire.       
 
         [0259]    The interventional device may be introduced over the other guidewire for carrying out the interventional procedure. 
         [0260]    In one case the interventional procedure comprises a stenting of the treatment location. In another case the interventional procedure comprises a balloon angioplasty procedure at the treatment location. 
         [0261]    In another aspect the invention provides a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       advancing a guidewire through a vasculature;   crossing a desired treatment location with the guidewire;   introducing over the guidewire a collapsible embolic protection filter having a collapsed configuration for delivery and withdrawal of the filter, and a deployed configuration;   deploying the filter distal to the treatment location;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval catheter;   fixing an abutment to the guidewire;   engaging the guidewire abutment with the filter to prevent movement of the filter distally of the guidewire abutment;   collapsing the filter and retrieving the filter into the retrieval catheter and with it the captured embolic material; and   withdrawing the retrieval catheter and the collapsed filter from the vasculature.       
 
         [0272]    The abutment may be fixed to the guidewire during deployment of the filter. Alternatively the abutment may be fixed to the guidewire before advancing the guidewire through the vasculature. 
         [0273]    In a further aspect of the invention, there is provided a retrieval catheter for retrieving a medical device deployed in a vasculature, the catheter comprising:—
       an outer catheter body; and   an inner coupling member having means for coupling to a medical device deployed in a vasculature;   the catheter body being movable distally relative to the coupling member to retrieve a coupled medical device into the catheter body.       
 
         [0277]    In one embodiment of the invention the coupling means comprises a male or female member on the coupling member for engagement with a corresponding female or male member on the medical device. 
         [0278]    In a preferred case the male member is movable between a low-profile configuration and an outwardly protruding configuration. Ideally the male member is biased towards the outwardly protruding configuration. Most preferably the male member is of a resilient material. 
         [0279]    In one case the coupling means is substantially arrow-head shaped. 
         [0280]    In another case the male member is in the form of a hook for hooking around a female member on the medical device. Alternatively the male member may be in the form of a hook for hooking around a tether arm on the medical device. Ideally the tether arm is at a proximal end of the medical device. The tether arm may be located within the medical device. 
         [0281]    In another embodiment of the invention the coupling means comprises at least one female member on the coupling member for engagement with at least one male member on the medical device. The female member may be in the form of a loop for looping around a protruding male member on the medical device. 
         [0282]    In a preferred embodiment the coupling means comprises a pair of jaws on the coupling member, the jaws being movable between an outwardly protruding configuration and a low-profile configuration to grasp the medical device. The retrieval catheter may comprise an actuator to move the jaws to the outwardly protruding configuration. Ideally the actuator is movable longitudinally relative to the jaws to move the jaws in a camming arrangement to the outwardly protruding configuration. Most preferably the jaws are biased towards the low-profile configuration. 
         [0283]    In another embodiment the catheter body is engageable with the jaws to move the jaws to the low-profile configuration. The jaws may be biased towards the outwardly protruding configuration. 
         [0284]    In another embodiment of the invention the coupling means comprises an inflatable member on the coupling member for engagement with the medical device. Preferably the inflatable member is movable inwardly upon inflation to engage the medical device. The coupling means may comprise an engagement surface on the coupling member for engagement with an inflatable member on the medical device. 
         [0285]    In a further embodiment the coupling member is at least partially of a magnetic material for magnetic coupling to an oppositely charged magnetic portion of the medical device. 
         [0286]    The retrieval catheter may comprise means to axially elongate a deployed medical device to collapse the medical device to a low-profile configuration for retrieval into the catheter body. Preferably the elongation means comprises a second coupling member movable relative to the first coupling member to collapse the medical device. Ideally the second coupling member comprises a pusher member movable distally relative to first coupling member to engage a deployed medical device distally of the first coupling means and thereby collapse the medical device. 
         [0287]    In one case the catheter body has a guidewire lumen extending partially therethrough for passing the catheter body over a guidewire in a rapid exchange manner. The guidewire lumen may be offset radially from the coupling member. 
         [0288]    The retrieval catheter of the invention may be for retrieving an embolic protection filter deployed in a vasculature. 
         [0289]    According to another aspect of the invention, there is provided a retrieval catheter for retrieving a medical device deployed in a vasculature, the catheter comprising:—
       a first coupling member having means for coupling to a medical device deployed in a vasculature; and   a second coupling member having means for coupling to the deployed medical device;   the coupling members being relatively movable to axially elongate the medical device and collapse the medical device.       
 
         [0293]    In one embodiment the catheter comprises an outer catheter body movable distally relative to the coupling members to retrieve a collapsed medical device into the catheter body. 
         [0294]    In another aspect, the invention provides a method of retrieving a medical device from a vasculature, the method comprising the steps of:—
       advancing a retrieval catheter through a vasculature until a distal end of the retrieval catheter is proximally of the deployed medical device;   axially elongating an element of the medical device to collapse the medical device; and   moving the retrieval catheter distally relative to the collapsed medical device to retrieve the medical device into the retrieval catheter.       
 
         [0298]    In one embodiment the method comprises the steps of:—
       engaging a first coupling member with the element of the deployed medical device;   engaging a second coupling member with the element of the deployed medical device; and   moving the coupling members relative to one another to axially elongate the element of the medical device.       
 
         [0302]    The invention also provides in another aspect an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; 
         [0303]    the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature in apposition with a vasculature wall; 
         [0304]    in the outwardly extended configuration the filter exerting an outward radial force on a vasculature wall sufficient to retain the filter in position against substantial longitudinal movement. 
         [0305]    In one embodiment of the invention the filter comprises a filter body and a filter support frame to support the filter body in the outwardly extended configuration in apposition with a vasculature wall, the filter support frame providing the outward radial force. 
         [0306]    The filter may comprise a low-friction outer layer. Preferably the outer layer is of a hydrophilic material. 
         [0307]    In one case the filter comprises an inflatable member to enhance the outward radial force. 
         [0308]    Ideally the filter defines a guidewire lumen for passing the filter over a guidewire. 
         [0309]    According to another aspect of the invention, there is provided an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; and 
         [0310]    the filter comprising a central tether extending proximally of the filter. 
         [0311]    Ideally the tether is a generally central tether. 
         [0312]    The tether may comprise a wire, preferably the wire is configured to facilitate passage of a medical device over the wire. 
         [0313]    The invention also provides in a further aspect, an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; and 
         [0314]    the filter comprising an inflatable member to exert an outward radial force on a vasculature wall sufficient to retain the filter in position against substantial longitudinal movement. 
         [0315]    In another aspect, the invention provides a method for the capture and removal of embolic material from a vasculature during an interventional procedure comprising the steps of:—
       advancing a first guidewire through a vasculature;   crossing a desired treatment location with the first guidewire;   introducing over the first guidewire a collapsible embolic protection filter having a collapsed configuration for delivery and withdrawal of the filter, and a deployed configuration;   deploying the filter distal to the treatment location;   withdrawing the first guidewire from the filter and the desired treatment location;   crossing the desired treatment location with a second guidewire;   introducing over the second guidewire an interventional device;   carrying out an interventional procedure at the treatment location, embolic material generated during the treatment procedure being captured by the deployed filter;   advancing a retrieval catheter;   collapsing the filter and retrieving the filter into the retrieval catheter and with it the captured embolic material; and   withdrawing the retrieval catheter and the collapsed filter from the vasculature.       
 
         [0327]    In one embodiment of the invention the method comprises the step of leading the second guidewire through the filter prior to carrying out the interventional procedure. The method may comprise the step of guiding the second guidewire through the filter. Ideally the second guidewire remains proximal of the deployed filter. 
         [0328]    In another embodiment the method comprises the steps of:—
       withdrawing the second guidewire from the filter and the desired treatment location;   advancing a third guidewire to the filter; and   advancing the retrieval catheter over the third guidewire.       
 
         [0332]    In one case collapsing the filter into the retrieval catheter comprises the step of releasing the filter from apposition with the vasculature wall. 
         [0333]    The diameters of the guidewires may differ. The material properties of the guidewires may differ. 
         [0334]    The invention provides in a further aspect an embolic protection filter assembly for deployment in a vasculature, the assembly comprising:—
       a filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; and   a receiver to guide a docking device into association with the filter.       
 
         [0337]    In one embodiment the filter has a guidewire lumen for passing the filter over a guidewire, and the receiver is configured to guide a guidewire into the guidewire lumen. The guidewire lumen may extend only partially through the filter. 
         [0338]    Preferably the receiver is configured to guide a coupling member towards the filter for coupling to the filter. 
         [0339]    In one case the receiver comprises a funnel. Preferably the funnel is movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for guiding a docking device. Ideally the funnel is biased towards the outwardly extended configuration. 
         [0340]    In one embodiment the funnel comprises a funnel body and a funnel support to support the funnel body in the outwardly extended configuration. Preferably the funnel body comprises a membrane. Ideally the funnel support comprises a plurality of pivotable fingers. 
         [0341]    In another embodiment the receiver comprises an approach channel. Preferably the channel is provided by a lumen in a catheter. 
         [0342]    The receiver may be mounted to the filter. Preferably the receiver is detachably mounted to the filter. 
         [0343]    Alternatively the receiver may be separate from the filter. 
         [0344]    In a preferred embodiment the receiver has means to space the receiver from the wall of a vasculature. Ideally the spacing means comprises an inflatable member to engage the wall of a vasculature. 
         [0345]    In one embodiment the receiver is at least partially provided by a wall of the filter. Preferably the receiver is at least partially provided by a wall of the filter at the inlet end of the filter. Alternatively the receiver may be at least partially provided by a wall of the filter at the outlet end of the filter. 
         [0346]    In one case the receiver extends proximally of the inlet end of the filter. In another case the receiver is located distally of the inlet end of the filter. 
         [0347]    In a further embodiment the receiver is radially offset from the longitudinal axis of the filter. 
         [0348]    According to a further aspect of the invention, there is provided an embolic protection system comprising:—
       an embolic protection filter assembly of the invention; and   a docking device which may be guided by the receiver into association with the filter.       
 
         [0351]    In one embodiment the docking device comprises a guidewire. 
         [0352]    In another case the docking device comprises a coupling member. 
         [0353]    In another aspect, the invention provides an embolic protection filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; 
         [0354]    the filter having a guidewire aperture for passing the filter over a guidewire; and 
         [0355]    the filter comprising a seal to seal the guidewire aperture. 
         [0356]    The seal may be self-closing. 
         [0357]    Ideally the seal is located at a proximal end of the filter, and/or at a distal end of the filter. 
         [0358]    The filter may have a tubular member extending from the guidewire aperture to define a guidewire lumen through the tubular member. In one case the tubular member extends through at least part of the filter. Preferably the tubular member is radially offset from the longitudinal axis of the filter. 
         [0359]    In one embodiment the seal is an annular member around the guidewire aperture, the annular member being closable down to seal the guidewire aperture. In one case the annular member is a tube. In another case the annular member comprises a soft membrane. The annular member may comprise two or more circumferentially overlapping flaps. 
         [0360]    The invention provides in another aspect an embolic protection filter for deployment in a vasculature, the filter having an inlet end and an outlet end, the inlet end having one or more inlet openings sized to allow blood and embolic material enter the filter, and the outlet end of the filter having a plurality of outlet openings sized to allow through passage of blood but to retain undesired embolic material within the filter; 
         [0361]    the filter being movable between a collapsed configuration for movement through a vasculature, and an outwardly extended configuration for deployment in a vasculature; 
         [0362]    the filter at least in the collapsed configuration having a guidewire lumen defined at least partially therethrough for passing the filter over a guidewire. 
         [0363]    The guidewire lumen may be defined by a tubular member extending at least partially through the filter. 
         [0364]    In one case the tubular member is mounted to the filter. In another case the tubular member is spaced proximally of a distal end of the filter. 
         [0365]    Preferably the tubular member is shortenable upon movement of the filter from the collapsed configuration to the extended configuration. Ideally the tubular member comprises at least two telescopable tubes. 
         [0366]    In one embodiment the tubular member is provided by a catheter. 
         [0367]    The catheter may be a retrieval catheter, or a delivery catheter. 
         [0368]    In another embodiment of the invention the filter comprises a support structure, in the collapsed configuration the support structure forming a tubular member to define the guidewire lumen. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0369]    The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:— 
           [0370]      FIG. 1  is a perspective of an embolic protection filter according to the invention; 
           [0371]      FIGS. 2 to 16  are partially cross-sectional, side views illustrating the use of an embolic protection filter; 
           [0372]      FIG. 17  is a perspective view of another filter of the invention; 
           [0373]      FIG. 18  is a side view of a further filter of the invention; 
           [0374]      FIG. 19  is an end view of the filter of  FIG. 18 ; 
           [0375]      FIG. 20  is a side view of another filter of the invention; 
           [0376]      FIGS. 21 and 22  are side views of another filter, in use; 
           [0377]      FIGS. 23 to 26  are diagrams illustrating a filter of the invention, in use; 
           [0378]      FIGS. 27 to 31A  are perspective views of various alternative constructions of filters; 
           [0379]      FIGS. 32 to 39  are various views of a delivery catheter which may be used in the invention; 
           [0380]      FIGS. 40 to 54  are side, partially cross sectional views illustrating various steps in the method of the invention; 
           [0381]      FIGS. 55 to 57  are various views of another delivery catheter which may be used in the invention; 
           [0382]      FIGS. 58 to 61  are views illustrating the use of a temporary lumen-defining member for filter delivery; 
           [0383]      FIGS. 62 to 68  are views illustrating the use of a part of the delivery system to provide a temporary lumen-defining member; 
           [0384]      FIGS. 69 and 70  are perspective views of such a lumen-defining member extending to a side of a filter; 
           [0385]      FIGS. 71 and 72  are perspective views of such a lumen-defining member extending through a filter; 
           [0386]      FIG. 73  is a schematic view of another embolic protection filter according to the invention in a deployed configuration; 
           [0387]      FIG. 74  is a schematic view of the filter of  FIG. 73  collapsed in a delivery catheter; 
           [0388]      FIG. 75  is a perspective view of another embolic protection filter according to the invention; 
           [0389]      FIG. 76  is a cross-sectional, side view of a delivery catheter according to the invention in a delivery configuration; 
           [0390]      FIG. 77  is a cross-sectional, side view of the filter of  FIG. 75  collapsed in the delivery catheter of  FIG. 87 ; 
           [0391]      FIG. 78  is a cross-sectional, side view of the delivery catheter of  FIG. 76  in a deployment configuration; 
           [0392]      FIGS. 79 and 80  are views of a filter with a guidewire passageway at the side thereof; 
           [0393]      FIG. 81  is an enlarged view of a detail of  FIG. 80 ; 
           [0394]      FIGS. 82 to 84  are perspective views illustrating different guidewire paths; 
           [0395]      FIG. 85  is a perspective view of another embolic protection filter according to the invention; 
           [0396]      FIG. 86  is an enlarged, perspective view of a receiver of the embolic protection filter of  FIG. 85 ; 
           [0397]      FIGS. 87 to 89  are partially cross-sectional, side views illustrating guiding of a guidewire through the embolic protection filter of  FIG. 85 ; 
           [0398]      FIG. 90  is a partially cross-sectional, side view of the embolic protection filter of  FIG. 85  deployed in a vasculature; 
           [0399]      FIGS. 91 and 92  are enlarged, perspective views of seals of the embolic protection filter of  FIG. 90 ; 
           [0400]      FIGS. 93 to 110  are partially cross-sectional, side views of the embolic protection filter of  FIG. 85  in use; 
           [0401]      FIG. 111  is a side view of another retrieval catheter according to the invention passing over a guidewire; 
           [0402]      FIG. 112  is a view along line B-B in  FIG. 111 ; 
           [0403]      FIGS. 113 and 114  are partially cross-sectional, side views illustrating retrieval of a filter of  FIG. 1  using a retrieval catheter; 
           [0404]      FIG. 115  is a perspective view of another embolic protection filter according to the invention; 
           [0405]      FIGS. 116 and 117  are perspective and cross-sectional, side views respectively of another embolic protection filter according to the invention; 
           [0406]      FIG. 118  is a perspective view of a further embolic protection filter according to the invention guiding a guidewire through the embolic protection filter; 
           [0407]      FIGS. 119 and 120  are partially cross-sectional, side views of the embolic protection filter of  FIG. 118  guiding a guidewire through the embolic protection filter; 
           [0408]      FIG. 121  is an end view of the embolic protection filter of  FIG. 118 ; 
           [0409]      FIG. 122  is a side view of a distal end of a filter; 
           [0410]      FIGS. 123 to 126  are end views in the direction of the arrow X of  FIG. 122  of various outlet seals; 
           [0411]      FIG. 127  is a perspective view of a distal end of the filter of  FIGS. 122 to 126 , in use; 
           [0412]      FIGS. 128 to 132  are various views of a filter with an alternative outlet seal; 
           [0413]      FIG. 133  is a perspective view of an alternative outlet seal; 
           [0414]      FIGS. 134 and 135  are cross-sectional views of the seal of  FIG. 133 , in use; 
           [0415]      FIGS. 136 and 137  are perspective views of further outlet seals; 
           [0416]      FIG. 138  is a perspective view of a further outlet seal; 
           [0417]      FIGS. 139 and 140  are cross-sectional views on the line A-A of  FIG. 138  in different configurations of use; 
           [0418]      FIGS. 141 to 143  are views of a further outlet seal arrangement; 
           [0419]      FIGS. 144 to 149  are partially cross-sectional side views illustrating retrieval of an embolic protection device; 
           [0420]      FIGS. 150 to 163  are partially cross-sectional, side views of an embolic protection filter and a retrieval catheter in use; 
           [0421]      FIGS. 164 to 165  are partially cross-sectional, side views illustrating retrieval of another embolic protection filter according to the invention; 
           [0422]      FIGS. 166 and 167  are schematic side views illustrating retrieval of an embolic protection filter using other retrieval catheters according to the invention; 
           [0423]      FIG. 168  is a perspective view of another embolic protection filter according to the invention; 
           [0424]      FIG. 169  is a perspective view illustrating retrieval of the filter of  FIG. 168 ; 
           [0425]      FIG. 170  is a perspective view of another embolic protection filter according to the invention; 
           [0426]      FIG. 171  is a perspective view illustrating retrieval of the filter of  FIG. 170 ; 
           [0427]      FIGS. 172 and 173  are perspective views of further embolic protection filters according to the invention; 
           [0428]      FIGS. 174 to 178  are schematic views illustrating retrieval of the embolic protection filter of  FIG. 168 ; 
           [0429]      FIGS. 179 and 180  are perspective views of further embolic protection filters according to the invention; 
           [0430]      FIGS. 181 and 182  are perspective views illustrating retrieval of another embolic protection filter according to the invention; 
           [0431]      FIG. 183  is a perspective view of another embolic protection filter deployed in a vasculature; 
           [0432]      FIG. 184  is a side view of part of another retrieval catheter according to the invention; 
           [0433]      FIG. 185  is a cross-sectional, side view of the retrieval catheter of  FIG. 184 ; 
           [0434]      FIGS. 186 to 188  are schematic side views illustrating retrieval of an embolic protection filter using the retrieval catheter of  FIG. 184 ; 
           [0435]      FIG. 189  is a side view along line A-A in  FIG. 188 ; 
           [0436]      FIGS. 190 to 192  are cross-sectional side views illustrating retrieval of an embolic protection filter using another retrieval catheter of the invention; 
           [0437]      FIG. 193  is a cross-sectional, side view of part of another retrieval catheter according to the invention; 
           [0438]      FIG. 194  is a partially cross-sectional, side view illustrating collapse of an embolic protection filter using the retrieval catheter of  FIG. 193 ; 
           [0439]      FIGS. 195 to 201  are various views illustrating the snaring of an embolic protection device of the invention; 
           [0440]      FIGS. 201 to 206  are various views illustrating snaring of another filter; 
           [0441]      FIGS. 207 to 212  are various views illustrating snaring of a further filter; 
           [0442]      FIGS. 213 to 218  are views illustrating another retrieval system; 
           [0443]      FIGS. 219 to 234  are views of the snaring of a filter of the invention; 
           [0444]      FIGS. 225 and 226  are views of another filter of the invention; 
           [0445]      FIGS. 227 to 230  illustrate retrieval of filters; 
           [0446]      FIG. 229A  is a cross-sectional view illustrating the retrieval of the filter of  FIG. 230  using the retrieval catheter of  FIG. 229 ; 
           [0447]      FIGS. 231 and 232  illustrate snaring of another filter; 
           [0448]      FIGS. 233 to 237  are side, partially cross-sectional views of the snaring of any filter; 
           [0449]      FIGS. 238 and 239  illustrate the snaring of another filter; 
           [0450]      FIG. 240  is a partially cross-sectional, side view of an embolic protection filter according to the invention in an expanded configuration; 
           [0451]      FIG. 241  is a partially cross-sectional, side view of the filter of  FIG. 240  in a collapsed configuration; 
           [0452]      FIGS. 242 and 243  are partially cross-sectional, side views illustrating retrieval of the filter of  FIG. 240 ; 
           [0453]      FIG. 244  is a partially cross-sectional, side view of the filter of  FIG. 240  after being recrossed with a guidewire; 
           [0454]      FIGS. 245 and 246  are partially cross-sectional, side views illustrating retrieval of the filter of  FIG. 244 . 
           [0455]      FIGS. 247 to 251  are views similar to  FIGS. 240 ,  241 , and  244  to  246  respectively of another embolic protection filter according to the invention; 
           [0456]      FIG. 252  is a schematic view illustrating fixing of an abutment to a guidewire; 
           [0457]    [ 253  to  255  are not used] 
           [0458]      FIG. 256  is a schematic view of the guidewire and the abutment; 
           [0459]      FIG. 257  is a perspective view of another embolic protection filter according to the invention passing over a guidewire; 
           [0460]      FIGS. 258 to 260  are partially cross-sectional side views illustrating guiding of a guidewire through an embolic protection filter; 
           [0461]      FIG. 261  is a cross-sectional, end view of a catheter according to the invention; 
           [0462]      FIG. 262  is a cross-sectional, end view of a catheter according to the invention; 
           [0463]      FIG. 263  is a cross-sectional, side view of another retrieval catheter according to the invention; and 
           [0464]      FIG. 264  is a partially cross-sectional, side view illustrating retrieval of an embolic protection filter using the retrieval catheter of  FIG. 263 . 
       
    
    
     DETAILED DESCRIPTION 
       [0465]    The invention provides an embolic protection system which has a number of features which allows the system to be used in placing a guide catheter proximal to lesion as per standard practice and advance any suitable guidewire across the lesion. A load filter is loaded into the delivery catheter in such a way as to provide a lumen through the loaded device through which the guidewire will pass. The loaded device is advanced over the guidewire and across the lesion. The filter is deployed from the delivery catheter and the delivery catheter is removed. The filter remains stable in the vessel without any user control. Standard interventional procedures (angioplasty, stent etc. . . . ) can be performed. The guidewire may be replaced by simply removing the initial wire and advancing a replacement wire through the guide catheter, across the lesion and through the filter. The filter may be retrieved by advancing a retrieval catheter over the guidewire and up to the filter. An inner member of the retrieval catheter may be engaged with the filter. Then outer retrieval sheath is advanced to collapse the filter and retrieve. The guidewire may be left in place if desired. 
         [0466]    Referring to the drawings and initially to  FIG. 1  there is illustrated an embolic protection filter  1  according to the invention, the filter  1  being suitable for deployment in a vasculature to filter undesired embolic material from the blood stream flowing through the vasculature. 
         [0467]    The filter  1  comprises a collapsible filter body  2  which in this case is supported by a collapsible filter support frame  3 . In this case the filter support is mounted on an inner tube  8 . 
         [0468]    The filter body  2  has an inlet end  4  and an outlet end  5 . The inlet end  4  has one or more, and in this a single, large inlet opening  6  which are sized to allow blood and embolic material enter the filter body  2 . The outlet end  5  has a plurality of small outlet openings  7  which are sized to allow through passage of blood but to retain undesired embolic material within the filter body  2 . In this way, the filter  1  captures and safely retains any undesired embolic material in the blood stream within the filter body  2  while facilitating continued flow of blood through the vascular system. Emboli are thus prevented from flowing further downstream through the vascular system, which could otherwise have potentially catastrophic results. 
         [0469]    The relatively large inlet opening  6  provide for the possibility of aspirating embolic material from within the filter body  2 . This may be particularly advantageous if it is desired to leave the filter  1  in place in a vasculature for a long period of time, for example overnight, to assist in vascular recovery. 
         [0470]    The filter body  2  may have a low-friction outer layer, for example a hydrophilic coating, to minimise frictional resistance during deployment and retrieval of the filter  1 , and the filter body  2  may be of an oriented polymeric material, as described in International patent application No. PCT/IE01/00087, the relevant contents of which are incorporated herein by reference. 
         [0471]    The inner tube  8  has a guidewire lumen  12  therethrough for passing the filter  1  over a guidewire  10 . A guidewire  10  can pass through the filter, however, in the deployed configuration the filter is independent of the guidewire. Thus, the guidewire can be moved independently of the filter without any associated movement of the filter. The arrangement allows relatively large radial forces to be exerted on the vascular wall without the risk of abrasion causes by movement of the deployed filter. In this way damage to the endothelium can be avoided. 
         [0472]    The filter  1  is movable between a low-profile, collapsed configuration for movement through the vasculature, and an outwardly extended configuration for deployment in the vasculature in apposition with the vasculature wall. 
         [0473]    In the outwardly extended configuration, the filter body  2  is supported in an expanded position by the filter support  3  so as to maximise the internal volume of the filter body  2  to capture and safely retain as much embolic material as possible. 
         [0474]    The filter support  3  supports the filter body  2  in the outwardly extended configuration in apposition with the vasculature wall to prevent blood flow bypassing the filter  1  between the filter body  2  and the vasculature wall. 
         [0475]    The support frame in this case defines a proximal support hoop  15  which is connected to the tubular member  8  by a support arm  16 . The support  3  in this case also comprises a number of axially extending portions  17  which assist in providing body support to the filter in a vessel and assist in preventing rotation of the filter when deployed in the deployed configuration. The support may be of wire and may also comprise one or more stabilising hoops(s)  18 . 
         [0476]    In this case the tubular member  8  terminates proximally of the distal end  5  of the filter. This has a number of advantages. It facilitates recrossing of the filter  1  with a guidewire and the distal free end of the tubular member  8  may be readily snared for snaring and/or retrieval of the filter when it is desired to remove the filter from the vasculature. 
         [0477]    In the outwardly extended configuration, the filter support  3  exerts an outward radial force on the filter body  2  and the vasculature wall which results in a frictional force between the filter body  2  and the vasculature wall sufficient to retain the filter  1  in position against substantial longitudinal movement. 
         [0478]    In the invention the filter will not rotate or collapse in the absence of guidewire support. Conventional filters are coupled (directly or indirectly) to a wire—this wire enhances the stability of the filter. This invention describes a filter which will remain fully open and opposed to the vessel wall in the absence of any support from a guidewire. This is achieved by using a support frame which does not allow rotation in the vessel lumen. In general, a frame which lies in only one plane cannot remain apposed to the vessel wall without support from the guidewire. The design of the system is such that the filter must do considerable work to move longitudinally. 
         [0479]    In order to ensure that the filter is retained in position the filter apposition force generates a frictional force between the filter and the vessel. The frictional force generated by the filter is dependent on the contact area, the apposition force generated by the filter and the coefficient of static friction between the filter and the vessel. Locating the filter using frictional forces alone is a worst-case analysis as it does not include the effect of tapered vessels. These will increase the apposition force generated by the filter as it moves distally into a lumen of decreasing diameter. 
         [0480]    The radial apposition force of the filter support  3  is sufficient to retain the deployed filter  1  in position in the vasculature against substantial longitudinal movement, even if the guidewire, over which the filter  1  is delivered, is moved. No step, abutment or other stop means is required on the guidewire to prevent the filter  1  from migrating downstream in the vasculature. In this manner, the invention enables an interventional procedure to be performed using a standard guidewire. This enhances clinician freedom by enabling a clinician to choose the most appropriate medical guidewire for a particular interventional procedure, and/or a particular patient anatomy. 
         [0481]    In the case of a filter which has an integral tubular member the tubular member defines a lumen through which a guidewire can pass. In the invention such a guidewire passageway may be provided by a component of the delivery system such as a portion of a deployment pusher. Alternatively, the tubular member may be a separate component which is removed after the guidewire has passed through the filter. Thus, the member defining a guidewire pathway through the filter may be a movable or removable component. 
         [0482]    Referring to  FIGS. 2 to 16  there are illustrated various steps in the use of an embolic protection device during an interventional procedure. Various steps in the method will be described and it will be appreciated that the various steps and the features of the various apparatus used in the method may be used independently of one another, for example in the methods and apparatus of other aspects of the invention. 
         [0483]    The filter does not necessarily itself have a predetermined lumen for passage of a guidewire. At various stages a lumen is defined when such a lumen is required. On loading of a filter  20  into a delivery catheter  21  a guidewire lumen is defined ( FIG. 2 ) which is used for delivery of the filter  20  over a pre-positioned guidewire  10  ( FIG. 3 ). The lumen-defining member  22  may be removed ( FIG. 3 ) and the filter is advanced to and deployed distal to a treatment location in the vasculature ( FIGS. 4 and 5 ). Various procedures may be carried out such as balloon angioplasty and stenting ( FIGS. 6 and 7 ). The filter may be retrieved into a retrieval catheter  25  ( FIGS. 11 to 15 ) and the filter removed. 
         [0484]    In this case the filter  20  comprises a filter body supported in the deployed configuration by a support frame  3  defining a large proximal opening  6  and having a snaring engaging element in the form of a hook  26 . In use, the filter is loaded into a delivery catheter L 6  by inserting a tubular element  22  through the filter. The delivery catheter may be threaded onto a pre-deployed bare guidewire  10 , the tubular element  22  guiding the guidewire  10  through the filter  20  at the distal end of the delivery catheter  21 . Once the guidewire  10  has entered the delivery catheter  21  proximal to the filter  20  the tubular element  22  may be removed. To facilitate this, the tubular element may be of C-shape in transverse cross section. The delivery catheter  21  is then advanced over the guidewire  10  to a location which is distal of a treatment site. The filter  20  is deployed by pushing it out from the distal end of the delivery catheter, for example by using a pusher. The filter is then in the deployed open configuration distal to a treatment location ( FIG. 5 ). Various procedures may be carried out at the treatment location, and embolic material released during the treatment procedures being captured in the filter. The treatment procedures may include deployment of a stent  29  from a stent delivery catheter threaded over the guidewire  10 . When it is desired to retrieve the filter a retrieval catheter  25  is delivered over the guidewire  10 . The retrieval catheter  25  may be a snare catheter or a separate snare catheter may be delivered through the retrieval catheter. The snare may comprise a lasso  30  or the like which engages the snaring hook  26  of the filter support frame. The guidewire  10  may then be withdrawn or left in place. 
         [0485]    In certain circumstances the guidewire  10  could be retracted, or even removed completely ( FIG. 8 ), without disturbing the position of the deployed filter in the vasculature. Another guidewire  10 A may be advanced through the filter ( FIGS. 9 and 10 ). This may be particularly advantageous in the case of certain interventional procedures, for example in coronary applications as will be described in more detail below. 
         [0486]    The support  3  may be configured to distribute the outward radial force over a relatively large area of the vasculature wall to minimise local stress distributions. Many different designs of filter may be used such that on deployment, the filter applies a local radial force to the vasculature to substantially prevent movement of the filter relative to the vasculature in the deployed configuration. In the deployed configuration the filter is anchored to the vasculature. In some cases the filter comprises a filter body and a filter support frame to support the filter in the deployed configuration. The support frame and/or the filter body may comprise the anchor. The anchor may comprise a plurality of anchor elements which may be spaced-apart circumferentially around the filter when the filter is in the deployed configuration. 
         [0487]    Referring to  FIG. 17  the filter frame includes a proximal support hoop  31  with radially projecting vessel indentors or stabilisers  32  to prevent longitudinal movement of the filter in the vessel. The frame may include a snaring feature  33  which may have a radiopaque marker  34 . 
         [0488]    Referring to  FIGS. 18 and 19  the vessel indentors or stabilisers  32  may also provide convenient attachment locations for attachment of tethers  35 . The tethers  35  may be interconnected at the proximal end by a connector  36  which may be radiopaque for ease of location to snare the filter for retrieval. 
         [0489]    Referring to  FIG. 20  the filter may have an enlarged lip  37  at the proximal end for engagement in a vessel to anchor the filter in a desired position. 
         [0490]    Referring to  FIGS. 21 and 22  there is illustrated another filter which is apposed in a vessel. The filter has a retrieval mechanism somewhat like a closed drawstring arrangement with a mesh-like structure  38 , when deployed, which may be engaged by the distal tip  39  of a centering catheter (or any suitable snare) for collapsing the filter and drawing it into a retrieval catheter  40 . 
         [0491]    Another filter frame is illustrated in  FIGS. 23 to 26 . The frame has a proximal hoop  41  and distally projecting arm  42 . X denotes terminations of the bifilar type to facilitate wrap-down of the filter as illustrated in  FIGS. 24 and 25 . Thus, the parking space occupied by the filter is optimised. In the deployed configuration in a vessel as schematically illustrated in  FIG. 26  the filter apposes the vessel wall and rotation and translation of the filter in relation to the vasculature is prevented. 
         [0492]    In general, the filter applies sufficient radial force to remain stable in a vessel when in the deployed configuration. In addition, the filter remains correctly orientated even without a guidewire in place. Some filters of this type are illustrated in  FIGS. 27 to 31 . In  FIG. 27  the filter  43  has body support. In  FIG. 28  the filter  44  has stabilising arms  45 . The filter of  FIG. 29  is in the form of a hoop  46  with a number of inflection points  47 . There may be four or more such inflection points as illustrated. 
         [0493]    In  FIG. 30  the filter has two axially spaced-apart support hoops  48  which are interconnected by connecting arms  49 . The filter of  FIG. 31  has two offset hoops  50 . Any of these filters may be connected to a central tubular member by a rigid member(s) and/or by a tether(s). Many more arrangements with support in more than one place are envisaged. 
         [0494]    The filter  51  of  FIG. 32  has body support provided by a nitinol tube or wire. 
         [0495]    To retrieve the filter  710 , any suitable means, such as the hooked retrieval catheter ( FIG. 250 ), or the looped retrieval catheter ( FIG. 251 ) may be used, in a manner similar to that described previously with reference to  FIGS. 242 and 243 . 
         [0496]    Referring to  FIGS. 32 to 39  there is illustrated a delivery catheter  200  which may be used with a filter of the invention. This catheter is described in detail in our co-pending U.S. Ser. No. 10/180,980, the relevant contents of which are incorporated herein by reference. The delivery catheter  200  comprises a catheter body  202  which extends between a proximal end  203  and a distal end  204 , a restraining sheath  210  at the distal end  204  of the catheter body  202 , and an elongate actuator, which is provided in this case in the form of a stainless steel wire  209 . 
         [0497]    The catheter body  202  comprises a proximal hypotube portion  205  and a radially offset distal spring pusher  206 . As illustrated in  FIGS. 34 and 35 , the pusher  106  is fixedly attached to the hypotube  205  in a side-by-side overlapping arrangement with the proximal end of the pusher  206  located proximally of the distal end of the hypotube  205 . 
         [0498]    The pusher  206  has a guidewire lumen  16  extending through the pusher  206  with an opening  217  at the proximal end of the lumen  216  for passage of a guidewire  222  through the lumen  216  and out through the proximal guidewire opening  217  ( FIG. 35 ). The delivery catheter  200  is thus configured to be passed over the guidewire  22  in a rapid-exchange manner. 
         [0499]    The pusher  206  tapers proximally inwardly at the opening  217  for a smooth crossing profile. 
         [0500]    When assembled, the hypotube  205  and the pusher  206  are located substantially side-by-side. This side-by-side assembly of the hypotube  205  relative to the pusher  206  enables the guidewire  222  to exit through the proximal guidewire opening  217  smoothly and substantially parallel to the longitudinal axis of the catheter  200 . In particular, the passage of the guidewire  222  through the proximal guidewire opening  217  does not increase the overall profile of the catheter  200 . 
         [0501]    A connector shaft  212  is fixed to the sheath  210  with the shaft  212  extending proximally over the pusher  206  towards the distal end of the hypotube  205 . The proximal end of the sheath  210  overlaps the distal end of the shaft  212 , and a marker band  213  is located at the distal end of the shaft  212  between the shaft  212  and the sheath  210 . 
         [0502]    The actuator wire  209  extends distally through an actuator lumen  232  in the hypotube  205 , out of the actuator lumen  232  at the distal end of the hypotube  205 , externally along the pusher  6  to the proximal end of the shaft  212 . The wire  209  is attached to the exterior surface of the shaft  212 , for example by bonding. By attaching the wire  209  to the exterior of the shaft  212 , this arrangement provides for more space within the pusher lumen  216  for guidewire passage. In addition, attachment of the actuator wire  209  to the exterior of the shaft  212  is an easier step to achieve from a manufacturing viewpoint than attachment to the interior of the relatively long shaft  12 . 
         [0503]    The restraining sheath  210  and the connector shaft  212  are movable in a sliding manner relative to the catheter body  202 . When the sheath  210  extends distally of a distal end of the spring pusher  206 , the sheath  210  defines an internal reception space  211 , as illustrated in  FIGS. 36 to 38 . A collapsed embolic protection filter  301  may be received within the reception space  211 , where the filter  231  will be restrained by the sheath  210  in a low-profile configuration during delivery to a desired site in a vasculature. A suitable material for the sheath  210  is polyethyleneterephthalate (PET). 
         [0504]    The distal end of the shaft  212  is flared outwardly ( FIG. 38 ). During delivery of the filter  231 , the distal end of the pusher  206  is spaced proximally of the distal end of the shaft  212 , and the proximal end of an inner tubular member  236  of the filter is partially inserted into the flared shaft  212 . This arrangement provides a bridge in stiffness between the relatively stiff shaft  212  and the relatively stiff inner tubular member  236  of the filter  231 . Thus the possibility of buckling of the relatively flexible sheath  10  is minimised. The distal end of the pusher  206  is engagable with the inner tubular member  236  of the filter  231  upon retraction of the sheath  210  to deploy the filter  231  out of the reception space  211 . 
         [0505]    As illustrated in  FIG. 39 , at the proximal end  203  of the catheter  200  a distal handle  208  is provided for gripping the catheter body  202  and a proximal handle  214  is provided for gripping the actuator wire  209 . The distal handle  208  is injection moulded over the hypotube  205  and the proximal handle  214  is crimped to the proximal end of the wire  209 . 
         [0506]    The handles  208 ,  214  are movable relative to one another in a telescoping manner with the proximal handle  214  sliding within the distal handle  208 . Movement of the handles  208 ,  214  is limited by means of stop means. Abutment of an outward annular protrusion  233  on the proximal handle  214  against the proximal end of the distal handle  208  prevents further movement of the proximal handle  214  distally relative to the distal handle  208 . Engagement of a shoulder  234  on the proximal handle  214  with an inward annular protrusion  235  on the distal handle  208  prevents further movement of the proximal handle  214  proximally relative to the distal handle  208 . A releasable safety clip  237  is provided to maintain the handles  208 ,  214  fixed relative to one another. 
         [0507]    When the catheter  200  is assembled the sheath  10  is directly connected to the proximal handle  214 , and the pusher  206  is directly connected to the distal handle  208 . Movement of the proximal handle  214  proximally relative to the distal handle  208  moves the wire  209 , the connector shaft  212  and the sheath  210  proximally relative to the pusher  206  to facilitate deployment of the filter  231  from within the reception space  211 . 
         [0508]    The delivery catheter  200  may be used to deliver the embolic protection filter  231  through a vasculature and to deploy the embolic protection filter  231  downstream of a stenosed region in the vasculature to prevent potentially harmful emboli, which may be released into the blood stream during treatment of the stenosis, such as by a stenting procedure, from migrating further through the vascular system. 
         [0509]    Referring to  FIGS. 40 to 54  the use of the delivery catheter  200  will now be described in relation to a filter  301  of the invention which has tubular member  306  with a distal end that is spaced proximally from the distal end of the filter. Such as arrangement facilitates removal replacement of a guidewire and can also be readily snared and retrieved as described herein. 
         [0510]    In use, a loading device  310  is partially inserted into the reception space  211  of the sheath  210 . A pushing device  311  is then threaded through the tubular member  306  of the filter  301  and extended into the reception space  211 , as illustrated in  FIG. 40 . 
         [0511]    By moving the pushing device  311  proximally, an engagement stop  312  on the pushing device  311  engages the distal end of the tubular member  306  and the filter  301  is moved towards the loading device  310  ( FIG. 10 ). Continued proximal movement of the pushing device  311  pushes the filter  301  through the loading device  310 , thereby collapsing the filter  301 , and into the reception space  11  ( FIG. 41 ). 
         [0512]    The catheter  200  with the collapsed filter  301  received within the reception space  11  are then moved together proximally away from the loading device  310  ( FIG. 42 ). 
         [0513]    The method of collapsing the filter  301  and loading the filter  301  into the reception space  211  is similar to that described in International patent application number PCT/IE01/00052, the relevant contents of which are incorporated herein by reference. 
         [0514]    Next the guidewire  222  is inserted into a vasculature  315  and advanced through the vasculature  315  until the guidewire  222  has crossed a site of interest in the vasculature  315  ( FIG. 44 ). A typical site of interest is a stenosed or diseased region  316  of the vasculature  315 . The delivery catheter  200  is then threaded over the guidewire  222  by inserting the proximal end of the guidewire  222  into the guidewire lumen  216  at the distal end of the pusher  206 , through the lumen  216 , and out of the lumen  216  through the proximal guidewire opening  217 . The catheter  200  is advanced over the guidewire  222  in a rapid-exchange manner until the reception space  211  is located downstream of the stenosis  316  ( FIG. 45 ). 
         [0515]    To deploy the filter  301  at the desired site in the vasculature  315  downstream of the stenosis  316 , the proximal handle  14  is moved proximally while holding the distal handle  208  fixed, thereby causing the pull wire  209  and the connector shaft  212  to be pulled proximally. Because the connector shaft  212  is attached to the sheath  210 , the sheath  210  also moves proximally while the pusher  206  does not move. In this way, the collapsed filter  301  is uncovered by the sheath  10  while the distal end of the pusher  206  abuts the proximal end of the tubular member  306  of the filter  301 . The delivery catheter  200  thus enables the self-expanding filter  301  to expand outwardly to a deployed configuration. The distal end of the pusher  6  acts as an abutment for a controlled, accurate deployment of the filter  301  at the desired site in the vasculature  315 . 
         [0516]    When the filter  230  has been fully deployed at the desired site in the vasculature  315 , the delivery catheter  200  is withdrawn from the vasculature  315  over the guidewire  222  in a rapid-exchange manner to leave the deployed filter  301  in place in the vasculature  315  ( FIG. 48 ). 
         [0517]    Various procedures can be carried out using the guidewire such as an angioplasty using a balloon  320  ( FIG. 49 ) or a stenting procedure with a stent  321  ( FIG. 50 ). On completion of the procedures a retrieval device such as a retrieval catheter  325  or snare may be used to retrieve the filter ( FIGS. 51 to 53 ). The guidewire  222  may be left in place or removed. 
         [0518]    In  FIGS. 55 to 57  there is illustrated another delivery catheter  600  according to the invention, which is similar to the delivery catheter  200  and similar elements are assigned the same reference numerals. In this case the distal end of the shaft  212  is not flared outwardly, and the proximal end of the inner tubular member  306  is not inserted into the shaft  212 , during delivery of the embolic protection filter  610 . 
         [0519]    Instead a bridging sleeve  601  is provided mounted around the shaft  212  distally of the marker band  213 , as illustrated in  FIG. 57 . The sleeve  601  extends distally of the distal end of the shaft  212 , such that the proximal end of the inner tubular member  306  of the filter  610  may be partially inserted into the sleeve  601  during delivery of the filter  610  ( FIG. 57 ). This arrangement provides a bridge in stiffness between the relatively stiff shaft  212  and the relatively stiff inner tubular member  306  of the filter  610 . Thus the possibility of buckling of the relatively flexible sheath  210  is minimised. 
         [0520]    It is noted that the filter  610  of  FIGS. 57(   a ) to  57 ( c ) is of a different configuration to the filter described previously. In particular the inner tubular member  306  of the filter  610  does not have any step formations or protrusions at the proximal end of the inner tubular member  306 . 
         [0521]    The delivery catheter of the invention is also suitable for over-the-wire exchange over a guidewire. The rapid exchange configuration is not essential. 
         [0522]    Referring to  FIGS. 58 to 61  there is illustrated one means of temporarily providing a tubular lumen in a filter to facilitate delivery of the filter to a desired location. In this case an introducer tool is in the form of a C-shaped tubular member  60  with a distal peel-back feature  61 . The tool is inserted into the distal end of the filter  62  as illustrated in  FIG. 58 . The filter is loaded into a distal pod  63  of a delivery catheter  64  ( FIG. 58 ) and the distal end of the delivery catheter  64  is threaded over the proximal end of a deployed guidewire  65 . When the guidewire has passed through the filter the introducer may be pulled away and removed as illustrated in  FIG. 61 . 
         [0523]    In another arrangement illustrated in  FIGS. 62 to 65  the delivery catheter  70  may itself be provided with a member  71  defining a temporary tubular member for a guidewire. The tubular member may also function as a pusher. In one case once the guidewire has traversed the filter  62  the tubular member  71  may be positioned proximal of the filter during delivery and deployment ( FIGS. 63 to 65 ). In another case ( FIGS. 66 to 68 ) the tubular member  71  may extend through the filter up to the stage when the delivery catheter is being withdrawn. 
         [0524]    The pusher  71  may pass through the centre ( FIGS. 71 and 72 ) of the filter or may run beside the filter ( FIGS. 69 and 70 ). 
         [0525]    In  FIGS. 73 and 74 , there is illustrated another embolic protection filter  520  according to the invention. In the case of filter  520 , the guidewire lumen  521  through the filter  520  is defined by two telescoping tubes  522 ,  523 . The proximal tube  522  is fixed to the filter  520  at the proximal end of the filter  520 , and the distal tube  523  is fixed to the filter  520  at the distal end of the filter  520 . 
         [0526]    In the deployed configuration of  FIG. 73 , the distal tube  523  telescopes proximally over the proximal tube  522  so that the overall parking space of the filter  520  in a vasculature is minimised. In addition the distal tube  523  is spaced distally of the guidewire aperture  112  to facilitate crossing of the filter  520  with a guidewire without requiring the guidewire to be threaded through the tubes  522 ,  523 . 
         [0527]    In the collapsed configuration of  FIG. 74 , the distal tube  523  telescopes distally over the proximal tube  522  so that the guidewire lumen  521  is defined through the entire length of the filter  520  when collapsed, for example in a pod  524  of a delivery catheter  525 . 
         [0528]    The invention also envisages the use of a delivery catheter  650 , as illustrated in  FIGS. 75 to 89 , which is particularly suitable for delivering an embolic protection filter  651 , as illustrated in  FIG. 77 , the filter  651  not having an inner tubular member to define a guidewire lumen through the filter  651 . 
         [0529]    The delivery catheter  650  comprises an outer tubular member  652 , and an inner tubular member  653 , the inner tubular member  653  being movable distally relative to the outer tubular member  652  from a delivery configuration ( FIG. 76 ) to a deployment configuration ( FIG. 78 ). 
         [0530]    In the delivery configuration, the catheter  650  defines a reception space  654  for receiving the filter  651  in a collapsed configuration, as illustrated in  FIG. 77 . When the inner tubular member  653  is moved distally relative to the outer tubular member  652 , the filter  651  is pushed distally out of the reception space  654  by means of an engagement between a shoulder  655  of the inner tubular member  653  and the collapsed filter  651 . 
         [0531]    The invention provides features to enable a guidewire to be repositioned across the filter. It may be necessary to be able to replace the guidewire if the wire became accidentally withdrawn by the user during the procedure. It may then be necessary to replace the wire in order to access the lesion with other devices such as a balloon or stent catheter or even the filter retrieval catheter. Merely advancing a wire up to the filter is unlikely to provide sufficient support in all cases. Guidewire replacement may also be needed if the user desires to use a wire with different properties during the procedure. For example a very torqueable wire may be ideal for initially accessing and crossing the lesion, and may have adequate support to enable the filter to be delivered and deployed, but may not have sufficient support to enable a stiffer stent delivery system to reach the lesion. The invention facilitates removal of the first wire and replacement with a more supportive guidewire to facilitate use of the stent delivery system. This may be achieved without having to use an additional exchange catheter. 
         [0532]    This invention describes a filter which comprises a guidewire recrossing feature, wherein this feature may comprise some or all of a guiding funnel, a pathway and a blood restrictor. A guiding funnel is used as this operation will be performed “blind”. In general, it would be difficult to replace a guidewire through a tubular lumen while the filter is in the patient. In the invention the guidewire may be passed through the distal filter neck. The distal cone of the filter will act as a guiding channel. However the guidewire tip is very flexible—if it is to open a “valve” or blood restrictor it will need to have good push. In order to provide this push it is necessary to restrain the guidewire tip within a relatively narrow channel—this channel is provided by the filter neck. A restrictor may be provided to prevent any loss of embolic material while the first guidewire was absent—during which period the neck of the filter would be an open hole if no restrictor were present. This restrictor is intended simply to close and prevent blood flow in the absence of a guidewire. Once there is no blood flow through the filter neck embolic material will not collect there and will not restrict the passage of the second guidewire. 
         [0533]    Various guideways may be provided for a guidewire to assist crossing of a filter. Referring to  FIGS. 79 to 81  the pathway may be provided around the filter, for example in a side channel  80 . A radiopaque feature  81  may be provided on the filter to guide a user to the passageway. Alternatively the pathway may be through the filter to a single exit  82  ( FIG. 82 ), a separate exit  83  ( FIG. 83 ) or through the same exit  84  using a shortened tubular member  85  illustrated in  FIG. 84  and described in more detail herein. In these cases the guidewire passage/hole may be sealed to prevent passage of embolic therethrough as will be described in more detail below. 
         [0534]    Referring now to  FIGS. 85 to 92 , there is illustrated another embolic protection filter  50  according to the invention. The filter  150  comprises a receiver to guide a docking device into association with the filter  150 . In this case, the receiver is configured to guide a guidewire, such as the guidewire  130 , into the guidewire lumen  112 . The receiver is provided by a funnel  151  which diverges outwardly proximally, the funnel  151  being mounted to the filter  150  to extend proximally of the inlet end of the filter  150 . 
         [0535]    In this specification, the term funnel will be understood to mean any orifice with a cross-sectional area that decreases with distance. 
         [0536]    The funnel  151  may comprise a collapsible funnel body in the form of a membrane  152 , which in this case is supported by a collapsible funnel support, in the form of a plurality of support fingers  153 . The fingers  153  are pivotally mounted to the filter  50  and are biased to move the filter membrane  152  from a collapsed configuration for movement through the vasculature, to an outwardly extended configuration for guiding the guidewire  130 , as illustrated in  FIG. 86 . The funnel  151  may be of a radiopaque material. 
         [0537]    The funnel  151  may be used to guide the guidewire  130  along a pathway that enables the guidewire  130  to cross the filter  150 . The funnel  151  allows the procedure of leading the small diameter guidewire  130  through the small diameter guidewire lumen of the filter  150  to be performed more easily by guiding the tip of the guidewire  130  towards the proximal end of the guidewire lumen  158 . 
         [0538]    Use of the funnel  151  is particularly beneficial in the case where it is desired to lead the guidewire  130  through the guidewire lumen while the filter  150  is deployed in the vasculature, as illustrated in  FIGS. 87 to 89 . The funnel  151  enables a clinician to accurately and quickly thread the guidewire  130  through the guidewire lumen without risk of puncturing the filter body or of disturbing the filter  50  from its deployed position in the vasculature in apposition with the wall of the vasculature. 
         [0539]    The filter  150  further comprises at least one, and in this case two, seals  160 ,  161  to seal the guidewire lumen  158  to prevent embolic material from passing through the guidewire lumen  158 , when the filter  150  is in use in the vasculature. 
         [0540]    The seals  160 ,  161  are self-closing. In this case one seal  160  located at the proximal end of the filter  150 , and the other seal  161  located at the distal end of the filter  150 . 
         [0541]    The proximal seal  160  may be in the form of a tubular member of a soft membrane material. The guidewire lumen  158  extends through the tubular seal  160  and the seal  160  is closable down to seal the guidewire lumen  158 . 
         [0542]    The distal seal  61  is in the form of a tubular member with two or more, and in this case seven, circumferentially overlapping flaps, as illustrated in  FIG. 92 . This seal  161  is also closable down to seal the guidewire lumen  158 . 
         [0543]    It will be appreciated that the guidewire lumen  158  can be provided as any suitable passageway through the filter  150 . The guidewire lumen  158  does not have to be located along the central axis of the filter  150 . The guidewire lumen  158  may be radially offset from the longitudinal axis of the filter  150 . 
         [0544]    When the guidewire  30  is extended through the guidewire lumen  158 , the seals  160 ,  161  self-close around the guidewire  130  to prevent emboli flowing through the guidewire lumen  158 . Upon removal of the guidewire  130  from the guidewire lumen  158  while the filter  150  is deployed in the vasculature, the seals  160 ,  161  self-close down to completely close off the guidewire lumen  158 . 
         [0545]    In this manner, the seals  160 ,  161  ensure that no blood flow potentially carrying harmful embolic material can pass through the guidewire lumen  158 . All blood flows into the filter body through the inlet openings and out of the filter body through the small outlet openings, thereby trapping and safely retaining the undesired embolic material within the filter  150 . 
         [0546]    After an embolic protection filter has been delivered over a guidewire and deployed in a vasculature, it is not always possible to withdraw the guidewire from the vasculature before collapsing and withdrawing the filter from the vasculature. 
         [0547]    However in some cases it may be necessary to withdraw the guidewire over which the filter was delivered while leaving the filter deployed in the vasculature. 
         [0548]    Examples of when this need may arise are:
       when a high torque guidewire is used to facilitate filter delivery and deployment, and a stiffer guidewire is subsequently used to provide additional support during delivery and deployment of a stent;   when a guide catheter has prolapsed;   when a guidewire is withdrawn into a guide catheter to accelerate rate of resolution of a spasm.       
 
         [0552]    When this need does arise, the filter  50  of the invention may be used to filter potentially harmful emboli from a vasculature when the guidewire is withdrawn, while the filter remains deployed in the vasculature, as illustrated in  FIGS. 93 to 110 . 
         [0553]    A first guidewire  130  is introduced into and advanced through the vasculature  121  to cross the treatment location  122  ( FIG. 93 ), and the filter  150  is delivered through the vasculature  121  and deployed distally of the treatment location  122  ( FIGS. 94 to 97 ), in a manner similar to that described previously. 
         [0554]    In the outwardly extended configuration, the deployed filter  150  is retained in position in the vasculature  121  against substantial longitudinal movement by the radial apposition force of the filter body against the wall of the vasculature  121 . The first guidewire  130  can thus be withdrawn from the guidewire lumen of the filter  150 , and completely withdrawn from the vasculature  121  without disturbing the outwardly extended configuration of the filter  150  in the vasculature  121 . 
         [0555]    The deployed filter  150  is retained in position in the vasculature  121  against substantial longitudinal movement by means of the radial apposition force exerted by the filter support on the filter body and the vasculature wall, as described previously. 
         [0556]    A second guidewire  140  is then introduced into the vasculature  121  and advanced through the vasculature  121  until the second guidewire  140  crosses the desired treatment location  122 . The tip of the second guidewire  140  is guided towards the proximal end of the guidewire lumen by engagement of the guidewire tip with the funnel  151 , and the second guidewire  140  is then lead through the guidewire lumen. 
         [0557]    A stent  136  may then be delivered through the vasculature  121 , and deployed at the treatment location  122  using the stent delivery catheter  135 . In this case, the stent delivery catheter  135  passes over the second guidewire  140 . After completion of the interventional procedure, the retrieval catheter  120  is advanced to cross the stent  136  and the treatment location  122 , and the tip  125  is engaged with the filter  150 . As the tip  125  passes through the funnel  151 , the funnel  151  is caused to collapse down to the collapsed configuration. The filter  150  is then collapsed and retrieved into the retrieval catheter  120  and withdrawn from the vasculature  121 . Upon collapse of the filter  1 , the apposition of the filter with the vasculature  121  is released. 
         [0558]    The filter  150  ensures any embolic material generated during the interventional procedure is captured and safely removed from the vasculature  121 . 
         [0559]    The second guidewire  140  may be of a different diameter, or have different material properties to the first guidewire  130 . It may thus be easier or more suitable for the clinician to advance the stent delivery catheter  35  over the second guidewire  140  rather than over the first guidewire  130 . For example, it is sometimes the case that a high torque guidewire  130  is used to facilitate filter delivery and deployment, and a stiffer guidewire  140  is used subsequently to provide additional support during delivery and deployment of a stent. 
         [0560]    In some cases, it may be necessary or desirable to withdraw the second guidewire  140  from the filter  150  and the treatment location  122  after deployment of the stent  136 , and then to advance a third guidewire through the vasculature  121  to the filter, the retrieval catheter  120  then being advanced over the third guidewire to retrieve the filter  150 . This invention enables such a procedure to be carried out. 
         [0561]    Furthermore withdrawing a guidewire into a guide catheter may accelerate the resolution of spasm and reduce the risk of ischaemia. 
         [0562]    Referring to  FIGS. 111 to 114 , there is illustrated another retrieval catheter according to the invention, which is similar to the retrieval catheter of  FIGS. 190 to 192 . In this case, the catheter body  23  defines a guidewire lumen  151  radially offset from the coupling member  24 . The guidewire lumen  151  extends through only part of the catheter body  23  to facilitate passage of the catheter body  23  over a guidewire, such as the guidewire  140 , in a rapid exchange manner. 
         [0563]    In use, the retrieval catheter  150  may be used to retrieve the filter  1  deployed in the vasculature  21 . 
         [0564]    In one possible procedure, the second guidewire  140  is not led through the guidewire lumen  12  of the filter  1 . Instead the second guidewire  140  is advanced until the guidewire  140  has crossed the treatment location and the guidewire tip is proximally of the filter  1  ( FIG. 113 ). The filter  1  is then retrieved into the catheter body  23 . During this procedure the retrieval catheter  150  may be advanced distally off the end of the guidewire  140 . 
         [0565]      FIG. 115  illustrates another filter  170  according to the invention. In this case, the funnel  151  is mounted to the filter  170  distally of the inlet end of the filter  170 , so that the funnel  151  is located at least partially within the filter  170 . 
         [0566]    It will be appreciated that the receiver may be detachably mounted to the filter. For example, the receiver may be mounted to the filter after deployment in a vasculature, and/or may be detached from the filter before retrieval of the filter from a vasculature. 
         [0567]    In addition, the receiver may be radially offset from the longitudinal axis of the filter. 
         [0568]    Referring to  FIGS. 116 and 117 , there is illustrated another filter  180  according to the invention. The funnel is provided, in the case of filter  180 , by sloping walls  181  of the filter body at the inlet end. As the guidewire  130  is advanced to the filter  180 , the tip of the guidewire  130  meets the sloping walls  181  of the filter body and is guided distally inwardly towards the proximal end of the guidewire lumen. In this manner, the sloping walls  181  enable the guidewire  130  to be easily and quickly threaded into the guidewire lumen. 
         [0569]    The angle of inclination α of these sloping walls  181  can be altered, as indicated in  FIG. 117 , to suit the characteristics of the interventional procedure, and/or the vasculature, and/or the guidewire. 
         [0570]    The large inlet openings enable substantially unrestricted flow into the filter body, and the sloping walls  81  may be radiopaque material to aid guidewire passage. 
         [0571]      FIG. 118  illustrates a further filter  190  according to the invention. In this case, the filter  190  has a guidewire aperture  192  for passing the filter  190  over the guidewire  130 , and the filter  190  has a single, large inlet opening  191  at the inlet end of the filter  190 . The single, large inlet opening  191  provides no resistance to blood flow into the filter body. 
         [0572]    The sloping walls  192  at the outlet end of the filter  190  provides the funnel, in this case, to guide the guidewire  130  towards the guidewire aperture  192 . 
         [0573]    It will be appreciated that the outlet openings are smaller, in this case, than the guidewire diameter, thus the guidewire  130  does not snag or pass through the outlet openings but instead the guidewire  130  is guided distally inwardly to the guidewire aperture  192 . 
         [0574]    The filter  90  may have a guidewire aperture  112  for passing the filter  90  over the guidewire  30 , and the filter  90  has a single, large inlet opening  91  at the inlet end  4  of the filter  90 . The single, large inlet opening  91  provides no resistance to blood flow into the filter body  2 . 
         [0575]    The sloping walls  190  at the outlet end of the filter  190  provides the funnel, in this case, to guide the guidewire  130  towards the guidewire aperture  192 , as illustrated in  FIGS. 119 and 120 . 
         [0576]    It will be appreciated that the outlet openings are smaller, in this case, than the guidewire diameter, thus the guidewire  130  does not snag or pass through the outlet openings but instead the guidewire  30  is guided distally inwardly to the guidewire aperture  192 . 
         [0577]    As illustrated in  FIGS. 119 to 121  the filter  190  further comprises a distal seal at the guidewire aperture  192  in the form of an elastomeric self-sealing valve  400 . The valve  400  has co-operating flaps which meet centrally to close off the guidewire aperture  192  when the guidewire is not extended through the aperture  192 , as illustrated in  FIGS. 119 and 121 . As the guidewire is pushed through the guidewire aperture  192 , the flaps of the valve  400  are forced apart to permit passage of the guidewire  130 , as illustrated in  FIG. 120 . 
         [0578]    It will be appreciated that the valve  400  could alternatively be provided in the form of four, two, or any other number of co-operating flaps. 
         [0579]    Referring to  FIGS. 122 to 127  the guidewire exit hole may be sealed with a thin flexible membrane  401  which can withstand any pressure differential across the filter but can be deformed by the guidewire tip to open the seal/membrane. Various options are possible such as those illustrated in  FIGS. 123 to 126 . 
         [0580]    Another option is to provide a seal in the form of an invertible flexible tube  402 . The tube may have slits  403  for additional flexibility.  FIG. 128  shows an initial guidewire in position,  FIG. 129  shows the wire removed and the tube collapsed, sealing the hole. In  FIG. 130  a new wire is shown being advanced through the filter, the advancing of the wire pushing the tube out of the filter neck and forming a seal with the new wire as illustrated in  FIG. 131 . The tube may be slits or slots for added flexibility as illustrated in  FIG. 132 . 
         [0581]    The guidewire exit hole may also be sealed by a flap valve or the like. Referring to  FIGS. 133 to 135  a closure flap  410  is hingedly connected to the filter  411  by a curved lever  412 . The hinge point  413  is stepped back proximally from the flap  410  so that the pressure drop across the flap  410  does not cause the flap  410  to open. The flap  410  is opened against the biasing of the lever  412  on insertion of a guidewire  415  as illustrated in  FIGS. 134 and 135 . 
         [0582]    It will be appreciated that the hinge may have a range of different constructions. For example, as illustrated in  FIG. 136  a hinge  416  may be provided by a flattened wire or a hinge  417  may be formed by a narrowing of the lever as illustrated in  FIG. 137 . 
         [0583]    In another embodiment illustrated in  FIGS. 138 to 140  a distal end  420  of a filter may have a flattened neck section  421  which normally seals a guidewire aperture  422  but which can be opened to facilitate passage of a wire  423 . 
         [0584]    A further embodiment is illustrated in  FIGS. 141 to 143  in which the filter distal guidewire aperture has a foam-like insert  425  with slits to facilitate deformation of the foam as a guidewire  426  is inserted whilst still maintaining a sealing engagement with the guidewire  426 . 
         [0585]    In the invention the retrieval device grips and retrieves the filter. Conventional filters are retrieved by using the guidewire to engage with the filter. This invention describes a retrieval device with one member which engages with and restrains the filter while a second member may envelop the filter. The retrieval device may function in the absence of a guidewire so that the filter can be retrieved even if the user has removed the guidewire and failed to replace it. This retrieval process may involve three stages: 1) Engage with the filter, 2) Decouple filter from vessel, 3) Retrieve the filter. Alternatively the retrieval may involve two stages: 1) Engage with the filter, 2) Retrieve the filter. 
         [0586]    The retrieval process is simple and reliable. The snare (or loop or lasso) designs described provide one of the most reliable and versatile methods. There is preferably a feature on the filter with which this snare will engage easily. This feature and the snare loop are preferably radiopaque for ease of visibility and positioning. For example a large radiopaque ball (or shepherds crook) inside the filter may be pulled proximal to the filter when snared and wrapped down. 
         [0587]    Referring in particular to  FIGS. 144 to 146 , there is illustrated a retrieval catheter  620  according to the invention. The retrieval catheter  620  is suitable for retrieving a filter, deployed in a vasculature  621  distally of a treatment location  622 , such as a region of stenosis. 
         [0588]    The catheter  620  comprises an outer catheter body  623  and a coaxial inner coupling member  624 , the coupling member  624  having means for coupling to the filter especially a filter deployed in the vasculature  621  to be retrieved. 
         [0589]    The coupling means is provided, in this case, by an arrow-head shaped tip  625  on the coupling member  624 . The tip  625  has two male fingers  626  for engagement with two corresponding female recesses  627  on the filter  1 . 
         [0590]    The male fingers  626  are moveable between a low-profile configuration and an outwardly protruding configuration for engagement with the filter. In this case, the fingers  626  are of a resilient material, and are biased towards the outwardly protruding configuration. 
         [0591]    During introduction of the retrieval catheter  620  through the vasculature  621 , the tip  625  protrudes only partially distally of the distal end of the catheter body  623 , so that the resilient fingers  626  are maintained in the low-profile configuration. The protruding tip  625  prevents snagging of the open mouth of the catheter body  623  against any protruding parts of the vasculature wall. In addition the tip  625  tapers distally inwardly for a smooth crossing profile. 
         [0592]    When the retrieval catheter  620  has crossed the treatment location  622 , the coupling member  624  is moved distally relative to the catheter body  623 , to release the resilient fingers  626  to move to the outwardly protruding configuration. The coupling member  624  is then moved further distally into the filter until the fingers  626  engage with the recesses  627  of the filter. 
         [0593]    The recesses  627  may be defined in a more pronounced manner by providing inwardly protruding steps or abutments on the proximal end of the filter support against which the fingers  626  may engage. 
         [0594]    The catheter body  623  is next moved distally relative to the engaged filter  1  by maintaining the position of the coupling member  624 , the distal end of the catheter body  623  is engaged with the proximal end of the filter body, the catheter body  623  is further advanced and thus the coupled filter  1  is collapsed down releasing the apposition force and is retrieved into the catheter body  623 . When the collapsed filter  1  has been fully retrieved into the catheter body  623 , the retrieval catheter  620  is withdrawn with the filter  1  from the vasculature  621 . 
         [0595]    The coupling member  624  of the retrieval catheter  620  enables a deployed medical device, such as the filter  1 , to be retrieved into the retrieval catheter  620  with any retained embolic material within the filter  1  without requiring a step, or a clamp or any special stop features on the guidewire. Thus the retrieval catheter  620  enables the filter  1  to be used in combination with any standard guidewire. 
         [0596]    In addition, it is not necessary to retract the guidewire to facilitate retrieval of the filter  1 . 
         [0597]    In certain circumstances if the guidewire was withdrawn from the deployed filter  1  it would still be possible to retrieve the filter  1  using the retrieval catheter of the invention. This could speed up the overall procedure. Also in some cases it may be difficult to recross the filter  1  with a guidewire. Furthermore by obviating the need to recross the filter  1  with a guidewire, the possibility of a spasm being caused is minimised. 
         [0598]      FIGS. 152 to 165  illustrate the embolic protection filter  1  and the retrieval catheter  620  according to the invention, in use. 
         [0599]    A guidewire  630  is introduced into and advanced through the vasculature  621  until the guidewire  630  crosses the desired treatment location  622 . A delivery catheter  631  is then used to deliver the embolic protection filter  1  through the vasculature  621  over the guidewire  630 , the filter  1  being housed within a distal pod  632  of the delivery catheter  631  in the collapsed configuration. 
         [0600]    The filter  1  may in one case be loaded into a delivery catheter  631  as described in International patent applications Nos. PCT/IE01/00052 and PCT/IE01/00053, the relevant contents of which are incorporated herein by reference. It will be appreciated that other loading alternatives are also possible. 
         [0601]    When the distal pod  632  has been advanced to a desired site distal to the treatment location  622 , the pod  632  is moved proximally relative to an inner pusher to deploy the filter  1  out of the pod  632  into the outwardly extended configuration, as described in further detail in International patent applications Nos. PCT/IE01/00052 and PCT/IE01/00053. After complete deployment of the filer  1 , the delivery catheter  631  is withdrawn from the vasculature  621  ( FIG. 11 ). 
         [0602]    In the outwardly extended configuration the filter  1  is in apposition with the vasculature  621 , thereby preventing blood flow from bypassing the filter  1  between the filter  1  and the vasculature  621 . The radial apposition force of the filter support against the filter body and the wall of the vasculature  621  retains the filter  1  in position against substantial longitudinal movement, even if the guidewire  630  is moved or indeed removed. In this way the filter  1  is prevented from migrating downstream in the vasculature  621 . 
         [0603]    An interventional procedure is then carried out at the treatment location  622 . In the case illustrated, the interventional procedure is a stenting procedure using a self-expanding stent. However, a range of procedures are possible as alternatives to, or in addition to stenting, for example a balloon angioplasty procedure, a balloon-expandable stenting procedure, an atherectomy procedure, a lysis. 
         [0604]    A stent delivery catheter  635  is used to deliver a stent, such as a self expanding stent  636 , through the vasculature  621 , the stent  636  being held in a collapsed configuration by a restraining sheath  637  of the stent delivery catheter  635 . 
         [0605]    When the stent delivery catheter  635  has been advanced to the treatment location  622 , the sheath  637  is moved proximally relative to an inner body  638  of the catheter  635  to facilitate deployment of the stent  636  at the treatment location  622 . 
         [0606]    After complete deployment of the stent  636 , the stent delivery catheter  635  is withdrawn from the vasculature  621 , leaving the deployed filter  1  and the deployed stent  636  in the vasculature  621 . 
         [0607]    Any embolic material generated during delivery or deployment of the stent  636 , or during withdrawal of the stent delivery catheter  639  is captured and safely retained in the deployed filter  1 . 
         [0608]    After completion of the interventional procedure, the retrieval catheter  620  is introduced into the vasculature  621 , and advanced through the vasculature  621  until the stent  636  and the treatment location  622  have been crossed. 
         [0609]    The filter  1  is simultaneously collapsed and retrieved into the catheter body  623  of the retrieval catheter  620  and with it the captured embolic material, by engaging the tip  625  with the filter  1 , and then advancing the catheter body  623  distally over the coupling member  624  and the engaged filter  1 . 
         [0610]    Upon collapse of the filter  1 , the apposition of the filter  1  with the vasculature  621  is released. 
         [0611]    When the filter  1  has been fully collapsed and retrieved into the retrieval catheter  620 , the retrieval catheter  620  with the collapsed filter  1  and retained emboli therein are withdrawn from the vasculature  621 , leaving the deployed stent  636  in place at the treatment location  622  in the vasculature  621 . 
         [0612]    In this way, the filter  1  may be used to capture and safely remove any embolic material which has been generated during the interventional procedure. 
         [0613]    An expandable balloon may be provided on the filter to enhance the outward radial force on the vasculature wall to retain the filter in position against substantial longitudinal movement. In use, the balloon may be inflated after deployment at the desired site in the vasculature to effectively anchor the filter in position. The balloon may be subsequently deflated before retrieval of the filter. 
         [0614]      FIGS. 164 and 165  illustrate another embolic protection filter  300  according to the invention. The filter  300  comprises a capture tether  301  which extends externally of the filter body  2  from a proximal ring  302 , to which the tether  301  is fixed, to a distal capture hoop  303 . The capture hoop  303  is located around the distal core at the outlet end  5  of the filter  300  when the filter  300  is in the outwardly extended configuration, as illustrated in  FIG. 164 . The capture hoop  303  is slidable over the filter body. To collapse and retrieve the filter  300  into the retrieval catheter  20 , the coupling member  24  engages the capture tether  301  and causes the capture hoop  303  to move proximally. The coupling member  24  may be engaged with the capture tether  301  using a hook, or loop, or any other suitable coupling means, as described previously. In this manner the filter  300  is compressed for retrieval into the catheter body  23 , as illustrated in  FIG. 165 . 
         [0615]    The coupling means may alternatively be provided by a male member in the form of a hook  700 , as illustrated in  FIG. 166  for hooking around a receiver on the filter  1 . The hook  700  may be used to couple the coupling member  24  to any suitably configured embolic protection filter. 
         [0616]    For example, an embolic protection filter  710 , illustrated in  FIGS. 168 and 169 , has a tether arm  711  at a proximal end of the filter  710  around which the hook  700  may be extended to couple the deployed filter  710  with the coupling member  24  and thereby facilitate retrieval of the filter  710  into the catheter body  23 . 
         [0617]      FIGS. 170 to 173  illustrate further embolic protection devices  720 ,  725 ,  730  according to the invention. 
         [0618]    The filter  720  of  FIG. 170  has three tether arms  721  which extend radially inwardly from the filter body  2  to meet at a central point  722 . The hook  700  may be extended around any one of the tether arms  721  to couple the coupling member  24  to the filter  720 . This tether arrangement enables the filter  720  to be retrieved with a central, axial pull force. 
         [0619]    In the filter  725  of  FIG. 172 , the three tether arms  726  extend radially inwardly and distally to the central point  727 . In this manner the central point  727  is stepped back distally from the single, large inlet opening  6  to minimise the possibility of embolic material becoming caught or hung up on the tether arms  726 . 
         [0620]    The filter  730  of  FIG. 173  has a central ring  332  to which the tether arms  331  are fixed. 
         [0621]      FIGS. 174 to 178  illustrate the embolic protection filter  710 , being retrieved into the catheter body  24  using grasping jaws  906 . In this case, the jaws  906  comprise serrated edges  750  to achieve a secure grasping of the tether arm  711 . In this manner, the filter  710  may be coupled to the coupling member  24  and retrieved into the catheter body  23 . The retrieval catheter  905  is withdrawn from the vasculature after retrieving the filter  710  leaving the guidewire  30  remaining in the vasculature. 
         [0622]    The tether arms of any of the above described embodiments may be mechanically attached at the central point, and/or at the central ring, and/or to the filter body  2 , for example by bonding, or welding, or brazing. Alternatively the tether arms may be provided integral with the mesh/membrane of the filter body  2 . The tether arms could also be provided as a fibre from such a mesh. 
         [0623]    In the embolic protection filter  410  of  FIG. 179  the tether arm  411  is located within the filter  410 . To couple the coupling member  24  to the filter  410 , the hook  100  is extended into the filter  410  and hooked around the tether arm  411 . 
         [0624]    In the filter  413  of  FIG. 180 , two tether arms  412  are provided. It will be appreciated that any suitable number of tether arms may be provided at either end of an embolic protection filter, and/or within the filter. 
         [0625]    Referring to  FIGS. 181 and 182 , there is illustrated another embolic protection filter  500  according to the invention, which is similar to the filter  720 . 
         [0626]    In this case, the filter  500  comprises an inner tubular member  502  to which the three tether arms  501  are fixed. The tubular member  502  defines a guidewire lumen  503  therethrough for passing a guidewire  530  through the tubular member  502  ( FIG. 181 ). 
         [0627]    The tubular member  502  extends through only part of the filter  500 . As illustrated in  FIG. 182 , this enables the guidewire  530  to cross the filter  500  without having to thread the guidewire  530  through the relatively small diameter guidewire lumen  503 . 
         [0628]    This configuration may be particularly advantageous when it is desired to cross the filter  500  with a guidewire while the filter  500  remains deployed in a vasculature. In this circumstance, the distal end cone of the filter body may act as a guide to guide the guidewire  530  through the guidewire aperture  112 . 
         [0629]    The tubular member  502  of the embolic protection filter  510  illustrated in  FIG. 183  also extends only partially through the filter  510  to facilitate crossing of the filter  510  with the guidewire  530  without requiring threading of the guidewire  530  through the tubular member  502 . 
         [0630]    It will be appreciated that any other suitable means for coupling the deployed filter  1  with the coupling member  24  of the retrieval catheter  20  may be employed to facilitate retrieval of the filter  1  into the catheter body  23 , for example the coupling member  24  may be provided with one or more female recesses for engagement with one or more corresponding male protrusions on the filter  1 . 
         [0631]    Alternatively a female member on the coupling member  24  may be provided in the form of a loop  701 , as illustrated in  FIG. 167 , for looping around a male stub  702  protruding from the filter  1 . 
         [0632]    Referring to  FIGS. 184 to 189  there is illustrated another retrieval catheter  905  according to the invention. In this case, the coupling member  24  comprises a pair of jaws  906  at the distal end of the coupling member  24 . The jaws  906  are movable between an outwardly protruding configuration ( FIG. 186 ) and a low-profile configuration ( FIG. 187 ) to grasp the filter  1 . 
         [0633]    The jaws  906  are biased towards the low-profile configuration and may be moved outwardly by moving an inner elongate actuator  907  longitudinally distally relative to the jaws  906  to engage elbows  908  on the jaws  906  and thereby move the jaws  906  outwardly in a camming arrangement ( FIG. 186 ). 
         [0634]    The jaws  906  define a recessed portion  909   a  for co-operation with a protruding neck  909   b  on the proximal end of the filter  1  during grasping of the filter  1 , as illustrated in  FIG. 187 . 
         [0635]    In use, the retrieval catheter  905  is advanced through the vasculature  21  in the low-profile configuration until the jaws  906  are proximally adjacent to the deployed filter  1 . The actuator  907  is then moved distally relative to the jaws  906  to cam the jaws  906  open, and the opened jaws  906  are advanced until the recessed portion  909   a  of the jaws  906  are around the protruding neck  909   b  of the filter  1 . By moving the actuator  907  proximally relative to the coupling member  24  the jaws  906  are released to move inwardly to grasp the filter  1  around the neck  909   b . The grasped filter  1  may then be retrieved into the catheter body  23  by moving the catheter body  23  distally relative to the coupling member  24 . 
         [0636]    It will be appreciated that the jaws  906  may grasp any suitable part of the filter  1  to facilitate retrieval. For example, the jaws  906  may grasp the filter  1  at the inlet openings  6 , as illustrated in  FIGS. 188 and 189 . 
         [0637]    As illustrated in  FIGS. 190 to 191 , the jaws  906  may alternatively be biased outwardly. During advancement of the retrieval catheter  905  through the vasculature  21 , the jaws  906  are restrained in the low-profile configuration by the catheter body  23  ( FIG. 190 ). To move the jaws  906  outwardly, the coupling member  24  is moved distally relative to the catheter body  23  to release the jaws  906  to spring outwardly ( FIG. 191 ). 
         [0638]    To subsequently move the jaws  906  inwardly when the recessed portion  909   a  of the jaws  906  are around the protruding neck  909   b  of the filter  1 , the catheter body  23  is moved distally relative to the coupling member  24  to engage the jaws  906  and move the jaws  906  inwardly to grasp the filter  1  around the neck  909   b . The filter  1  is then retrieved into the catheter body  23  by advancing the catheter body  23  further distally relative to the coupling member  24  and the grasped filter  1  ( FIG. 192 ). 
         [0639]    Alternatively, the coupling member  24  may have a magnetic tip  25  for magnetic coupling to an oppositely charged magnetic portion of the filter  1 . 
         [0640]      FIGS. 193 and 194  illustrate another retrieval catheter  940  according to the invention. In this case, the retrieval catheter  940  comprises a second coupling member  941 , which is movable relative to the first coupling member  24 . In this way, the second coupling member  941  may be used to axially elongate an element of the deployed filter  1 , such as the filter support frame  3 , to collapse the filter  1  to the low-profile configuration for retrieval into the catheter body  23 . In this case, the second coupling member  941  acts as a pusher and is movable distally relative to the tip  25 . By engaging the tip  25  with the filter support  3  and then moving the second coupling member  41  distally to engage a distal end  42  of the filter support  3 , the filter support  3  is axially elongated and the filter  1  is collapsed from the outwardly extended configuration of  FIG. 194  to the collapsed configuration. 
         [0641]    The collapsed filter  1  may then be retrieved by moving the catheter body  23  distally relative to the tip  25  and the engaged filter  1 . 
         [0642]    Referring to  FIGS. 195 to 201  there is illustrated another filter retrieval system of the invention. In this case a snare type retrieval is used for a filter  850  with a guidewire  851  extending through a tubular member  852 . The tubular member  852  has a projecting head portion  853  with an associated marker band  854  for engagement by a lasso or loop  855  delivered through a retrieval catheter  856  into which the filter is retrieved as illustrated. 
         [0643]    Another embodiment is illustrated in  FIGS. 202 to 206  which is used for retrieval of a filter  860  which does not have a tubular member. In this case the filter frame has a snare receiving projection  861  which is engaged by a snare lasso/loop  862  and the filter  860  is retrieved into a retrieval catheter  863 , as illustrated. 
         [0644]      FIGS. 207 to 212  illustrate an embodiment in which a filter  870  is used which has a partial tubular member  871  but the guidewire does not extend through the tubular member. This arrangement is similar to that of  FIGS. 195 to 201  above and like parts are assigned the same reference numerals. The snare loop is in this case free of the guidewire and may be more easily manipulated. In both cases the snare loop may be rendered radiopaque to facilitate snaring with the filter for retrieval. 
         [0645]    Further retrieval devices are illustrated in  FIGS. 213 to 218  in which the retrieval devices have arms  950  which open out when an outer sheath  951  is retracted and thus create a large inlet mouth which can readily trap the filter frame, particularly if radiopaque features such as marker bonds are used. When the arms  950  are in position distal to the snare feature of the frame/filter the arms are closed again, for example by re-advancing a sheath  951  which collapses the arms  950  and traps tether feature  952  of the filter, for example behind a step or tooth on the arm(s). 
         [0646]    Referring to  FIGS. 219 to 224  the filter frame may have a retrieval feature such as a nodule  960  which may be engaged by a suitable snare such as a snare loop or lasso  961  which is then tightened or simply pulled back to collapse the frame and retrieve the filter. The centering tip  962  may be used to assist guiding of the snare loop. 
         [0647]    Various alternative filter designs with an integral snare feature are possible. For example, in  FIGS. 225 and 226  the filter frame has a projecting arm  970  which may be engaged by a snare. 
         [0648]    An expandable engagement member  971  may be used to catch a drawstring type arrangement  972  ( FIGS. 227 ,  228 ) or to catch internal wires/tethers/fibers/strings of the filter ( FIGS. 229 ,  230 ). 
         [0649]    Referring to  FIGS. 231 and 232  there is illustrated the size of a snare  990  to snare a filter  991 . The snare engagable features of the filter in this case are provided by indents  992  in the support arms over which the snare loop  990  is engaged. 
         [0650]    The snaring of a filter of any type is illustrated in  FIGS. 233 to 237 . In this case the filter  995  is positioned distal to a stent  996  and a snare loop  997  is advanced through the stent to engage the filter as illustrated, allowing the filter to be at least partially collapsed for retrieval. 
         [0651]    In  FIGS. 238 and 239  there is illustrated the snaring of a filter  1  as illustrated in  FIG. 1  using a snare loop  998 . 
         [0652]    A further embolic protection filter  700  according to the invention is illustrated in  FIGS. 240 and 241 . The filter  700  comprises a collapsible filter support structure  701  and a collapsible filter body  702 . 
         [0653]    In the expanded, deployed configuration of  FIG. 240 , the support structure  701  does not have an inner tubular member to define a guidewire lumen for passing a guidewire  703  through. When the filter  700  is collapsed, the support structure collapses down into a smaller diameter tubular structure, as illustrated in  FIG. 241 . In this collapsed configuration, the support structure  701  defines the guidewire lumen for the guidewire  703 . In this manner the support structure  701  isolates the filter body  702  from the guidewire  703 , and thus prevents the filter body  702  from becoming fixed to the guidewire  703  during delivery or retrieval of the filter  700 . 
         [0654]    The filter  700  may be retrieved using any suitable means, such as the hooked retrieval catheter ( FIG. 242 ), in a manner similar to that described previously or the hooped retrieval catheter ( FIG. 243 ), in a manner similar to that described previously. 
         [0655]    If it is desired to remove the guidewire  703  from the filter  700  and recross the filter  700  with a second guidewire  704 , the guidewire  704  may be threaded through one of the relatively large inlet openings  705  instead of through the relatively small proximal collar  706  of the support structure  701 , as illustrated in  FIG. 244 . This enables a faster and more convenient means of recrossing the filter  700 . 
         [0656]    In addition, the distal collar  707  of the filter support structure  701  is spaced proximally of the distal end of the filter  700  to facilitate crossing of the filter  700  with the second guidewire  704  without requiring the guidewire  704  to be threaded through the distal collar  707  ( FIG. 244 ). 
         [0657]    The filter  700  can be retrieved after crossing the filter  700  with the second guidewire  704  using any suitable means ( FIGS. 245 and 246 ). 
         [0658]    Referring to  FIGS. 247 and 248 , there is illustrated another embolic protection filter  710  according to the invention, which is similar to the embolic protection filter  700  of  FIGS. 240 and 241 , and similar elements in  FIGS. 247 and 248  are assigned the same reference numerals. 
         [0659]    The filter  710  is longitudinally shorter than the filter  700 . In addition the filter support structure  701  ends in an open distal mouth  711  in the filter  710  and no distal collar is provided in the filter  710 , as illustrated in  FIG. 247 . 
         [0660]    In the filter  710 , the filter body  702  is isolated from the guidewire  703  by the collapsed filter support structure  701  ( FIG. 248 ), in a manner similar to that described previously with reference to  FIG. 241 . 
         [0661]    The filter  710  may be recrossed by the second guidewire  704  by threading the guidewire  704  through one of the relatively large inlet openings  705  ( FIG. 249 ), in a manner similar to that described previously with reference to  FIG. 244 . 
         [0662]    Referring to  FIGS. 252 to 256  the position of the filter  1  in the vasculature  21  may be controlled by an abutment  200  on a guidewire  201 . By engaging the abutment  200  with an abutment surface on the filter  1 , the filter  1  is prevented from moving distally of the guidewire abutment  200 . In this manner, the position of the filter  1  in the vasculature  21  may be controlled, if necessary. 
         [0663]    The abutment  200  may be fixedly attached to the guidewire  201  by a suitable means, such as by crimping, before introducing the guidewire  201  into the vasculature  21 . Alternatively the abutment  200  may be fixed to the guidewire  201  during deployment of the filter  1 . 
         [0664]    As illustrated in  FIG. 257  the filter  205  according to the invention may have a tether  206  fixed to the filter  205 , extending proximally of the filter  205 . The tether  206  may be used by a clinician to control the position of the filter  205  in the vasculature  21  from a location externally of the vasculature  21 . The tether  206  may be in the form of a wire, and may be of any suitable material. 
         [0665]    In use, the filter  205  may be deployed over a guidewire  207 . If appropriate or necessary, the guidewire  207  may then be withdrawn from the filter  205  and the vasculature  21 . The tether wire  206  may then be used as a platform for advancing further devices through the vasculature  21 , for example the retrieval catheter  20 . 
         [0666]    Referring to  FIGS. 258 to 260 , there is illustrated another embolic protection filter assembly  115  according to the invention. The assembly  115  comprises a filter and a receiver to guide the guidewire  30  into the guidewire lumen  12 . The receiver is provided, in this case, by an approach channel  116  for the guidewire  30  in the form of a lumen in a separate catheter  117 . The catheter  117  has one or more inflatable balloons  118  at the distal end of the catheter  117 . The shape and/or position of the balloons  118  is configured to ensure that the blood flow through the vasculature  21  will not be occluded upon inflation of the balloon(s)  118 . In one case, the catheter  117  has three balloons  118  spaced circumferentially around the catheter  117 , as illustrated in  FIG. 261 . In another case, the catheter  117  has four circumferentially spaced balloons  118  ( FIG. 262 ). 
         [0667]    In use, the catheter  117  is introduced into the vasculature  21  and advanced through the vasculature  21  until the catheter distal end is proximally adjacent the filter  1  ( FIG. 56 ). The balloon  118  is then inflated until the balloon  118  engages the wall of the vasculature  21 . By engaging the balloon  118  with the wall of the vasculature  21 , the catheter  117  is spaced from the wall of the vasculature  21  to assist in locating the catheter approach channel  116  centrally in the vasculature  21 . The guidewire  30  may then be introduced into the channel  116  and advanced through the catheter  117 . Because the channel  116  is located centrally in the vasculature  21 , the guidewire  30  is guided into the guidewire lumen  12  of the filter  1  as it passes out of the distal end of the channel  116 . The balloon  118  may be deflated to a low profile configuration during introduction and withdrawal of the catheter  117  from the vasculature  21 . 
         [0668]    It will be appreciated that any number of seals may be provided to prevent embolic material passing through the guidewire lumen or the guidewire aperture, and the seals may be positioned at any suitable point along the guidewire lumen or the guidewire aperture. 
         [0669]    It will further be appreciated that the receiver may be configured to guide a docking device in the form of a coupling member, such as those described previously, towards the filter for coupling to the filter. In such a manner, the receiver may be used to assist retrieval of the filter. The coupling means may be achieved by numerous alternatives, for example male-female inter-engagement, or magnetic coupling, or hook and eyelet means. 
         [0670]      FIG. 263  illustrates another retrieval catheter  600  according to the invention. The coupling member  24 , in this case, has a tubular extension part  601  which extends distally of the hooks  100 . In use, the tubular extension  601  may be extended through an embolic protection filter  602  to be retrieved, as illustrated in  FIG. 264 . The tubular extension  601  in this way defines the guidewire lumen  603  through the filter  602  through which a guidewire  604  may be passed. 
         [0671]    The retrieval catheter  600  is particularly suitable for retrieving filters, such as the filter  602  which do not have an inner tubular member to define a guidewire lumen through the filter  602 . Filters which do not have an inner tubular member are liable to becoming fixed against the guidewire  604  when the filter is collapsed down. When this occurs it is no longer possible to retrieve the filter while the guidewire remains in situ in the vasculature. 
         [0672]    By defining the guidewire lumen  603  using the tubular extension  601  of the retrieval catheter  600 , this serves to isolate the collapsing filter  602  from the guidewire  604 , and thus prevents the filter  602  from becoming fixed to the guidewire  604 . 
         [0673]    The tubular extension  601  may be advanced to the distal end of the filter  602  before retrieving the filter  602  into the catheter body  23 , as illustrated in  FIG. 85 . 
         [0674]    Alternatively the tubular extension  601  may be advanced until the tubular extension  601  is distally of the distal end of the filter  602  before retrieving the filter  602  into the catheter body  23 . 
         [0675]    The invention is not limited to the embodiments hereinbefore described, with reference to the accompanying drawings, which may be varied in construction and detail.