Abstract:
A filter device for temporary placement of a filter in an artery or vein is disclosed. The devices include (1) an elongate tubular member having a single or double side-wire loop, (2) an elongate member having a filter bonded to a circular rim joined by a plurality of tethers and an independently moveable tether, and (3) an elongate member having a parachute filter joined by a plurality of flexible struts. The filter conforms to the interior of a vessel wall when expanded and contracts to a consistent diameter without bunching when stowed. The filter devices may act as guidewires for guiding a therapeutic catheter to a region of interest within a vessel. Methods of using the filter device to entrap and remove embolic material from a vessel during endovascular procedures are also disclosed.

Description:
This application is a continuation application of U.S. application Ser. No. 10/039,102, filed on Jan. 4, 2002 , now U.S. Pat. No. 6,936,059 which claims priority to U.S. Provisional Application No. 60/262,135, filed on Jan. 16, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to devices and methods for providing temporary placement of a filter in a blood vessel. More particularly, the invention provides a filter structure that conforms to the interior vessel wall with minimum gap and can be collapsed to facilitate its passage across large vascular lesions. 
     BACKGROUND OF THE INVENTION 
     Treatment of thrombotic or atherosclerotic lesions in blood vessels using an endovascular approach has recently proven to be an effective and reliable alternative to surgical intervention in selected patients. For example, directional atherectomy and percutaneous translumenal coronary angioplasty (PTCA) with or without stent deployment are useful in treating patients with coronary occlusion. Atherectomy physically removes plaque by cutting, pulverizing, or shaving in atherosclerotic arteries using a catheter-deliverable endarterectomy device. Angioplasty enlarges the lumenal diameter of a stenotic vessel by exerting mechanical force on the vascular walls. In addition to using angioplasty, stenting, and/or atherectomy on the coronary vasculature, these endovascular techniques have also proven useful in treating other vascular lesions in, for example, carotid artery stenosis, peripheral arterial occlusive disease (especially the aorta, the iliac artery, and the femoral artery), renal artery stenosis caused by atherosclerosis or fibromuscular disease, superior vena cava syndrome, and occlusive iliac vein thrombosis resistant to thrombolysis. 
     It is well recognized that one of the complications associated with endovascular techniques is the dislodgment of embolic materials generated during manipulation of the vessel, thereby causing occlusion of the narrower vessels downstream and ischemia or infarct of the organ which the vessel supplies. In 1995, Waksman et al. disclosed that distal embolization is common after directional atherectomy in coronary arteries and saphenous vein grafts. See Waksman et al., American Heart Journal 129(3):430-5 (1995), incorporated herein by reference in its entirety. This study found that distal embolization occurs in 28% (31 out of 111) of the patients undergoing atherectomy. In January 1999, Jordan, Jr. et al. disclosed that treatment of carotid stenosis using percutaneous angioplasty with stenting is associated with more than eight times the rate of microemboli seen using carotid endarterectomy. See Jordan, Jr. et al., Cardiovascular surgery 7(1): 33-8 (1999), incorporated herein by reference in its entirety. Microemboli, as detected by transcranial Doppler monitoring in this study, have been shown to be a potential cause of stroke. The embolic materials include calcium, intimal debris, atheromatous plaque, thrombi, and/or air. 
     Filters mounted to the distal end of guidewires have been proposed for entrapment of vascular emboli. A majority of these devices includes a filter which is attached to a guidewire and is mechanically actuated via struts or a pre-shaped basket which deploys in the vessel. These filters are typically mesh “parachutes” which are attached to the shaft of the wire at the distal end, and to wire struts which extend outward in a radial direction at their proximal end. The radial struts open the proximal end of the filter to the wall of the vessel. Blood flowing through the vessel is forced through the mesh thereby capturing embolic material in the filter. These devices are self-directing and can be placed intravascularly. 
     However, there are several disadvantages associated with guidewire-filtration. First, the steerability of the guidewire may be altered as compared to conventional guidewires due to the size of the filter, and the guidewire may bend, kink, and/or loop around in the vessel, making insertion of the filter through a complex vascular lesion difficult. Secondly, the current filter designs, e.g., a basket or net, often fail to conform to the internal perimeter of the vessel, and distal embolization can still occur despite the filter placement. Thirdly, as the filter is stowed, the filter material is gathered together with “bunching” of the material at the perimeter, causing uncontrolled gathering and creating relatively large and poorly defined crossing profiles. As a result, the current filter designs require large capture sheaths to deploy and stow the filter. 
     What is needed are simple and safe blood filtering devices that conform to a patient&#39;s vessel wall to prevent distal embolization during endovascular procedures, and provide easy steerability and a controlled closure profile when contracted. Existing devices are inadequate for this purpose. 
     SUMMARY OF THE INVENTION 
     The present invention provides devices and methods that protect a patient from distal embolization during endovascular procedures, e.g., atherectomy, angioplasty, or stent-deployment. More specifically, endovascular filters that conform to the interior vessel wall with minimum gap are disclosed for capturing embolic material generated during a procedure in an artery or vein. 
     In one embodiment, the filter device includes a first elongate member having a proximal end and a distal end. The first elongate member is typically a tubular member having first and second proximal ports locate a short distance proximal (1-3 cm, preferably 1 cm) from the distal end. The first port will generally be located approximately 180° circumferentially from the second port. One or two flexible members, e.g., wires made of stainless steel or plastic, each of which has a proximal end that extends through one of the first or second proximal ports on the first elongate member, and a distal end that is attached to the first elongate member at a position distal of the port. 
     In certain embodiments the distal end of one or both flexible members passes through first and second distal ports. Thus, the distal end of each flexible member is attached to the first elongate member within a lumenal wall of the first elongate member after passing through the distal port. The first proximal port on the tubular member is located at a circumferential position approximately 180° from the second proximal port, and the first distal port on the tubular member is located at a circumferential position approximately 180° from the second distal port. The first flexible member passes through one proximal port, and then through the distal port that is 180° from the proximal port through which the flexible member passes, and the same for the second flexible member. A filter is disposed about the first and second flexible members, which are operable between an expanded condition and a contracted condition from the proximal end of the tubular member. In certain embodiments, the filter is bonded at an edge to the first and the second flexible members. 
     In some embodiments, the filter comprises a mesh as described in Tsugita et al., U.S. Pat. No. 5,911,734, incorporated herein by reference in its entirety. In other embodiments, the filter is made of a biocompatible material, such as plastic (e.g., kynar, polyethylene tetrachloride, polyethylene, or mylar), having pores that are precision machined by laser, etching, and/or chemical milling to provide less traumatic pathways for blood flow. Anticoagulants, such as heparin and heparinoids, may be applied to the filter to reduce thrombi formation. 
     In another embodiment, the device comprises first and second elongate members. The second elongate member is slideably disposed within a lumen of the first elongate member. The proximal ends of the first and second flexible members are fixed to the second elongate member, and the distal ends of the flexible members are fixed to the first elongate member. The flexible members are operated by sliding the second elongate member distally within the first elongate member, thereby advancing the flexible members through the proximal ports and placing the filter in an expanded state. 
     In another embodiment, the filter device includes a flexible loop having a first end, a second end, and an intermediate section positioned near a distal port of the elongate tubular member. A filter is disposed about the intermediate section. The first end is operated to advance the flexible loop distally. The intermediate section of the loop extends through the distal port and into a lumen of a vessel for deployment of the filter. In some embodiments, a tether, which is attached at one end to the intermediate section of the loop, restrains the intermediate section and changes the orientation of a plane described by the loop, preferably orienting the plane perpendicular to the axis of the vessel. 
     In another embodiment, a plurality of tethers are coupled at a first end to the distal end of the elongate member, and the second end of each of the tethers is coupled to the edge of a parachute filter. In certain embodiments the edge of the filter is mounted about a circular rim. An independently moveable tether is also coupled to the filter edge or the circular rim and is operable at a proximal end. A capture sheath, slideably disposed over the filter and the circular rim, assists in stowing the filter and prevents accidental dislodgment of embolic material during filter closure. The circular rim or filter edge can be rotated into alignment substantially parallel with the elongate member and capture sheath by withdrawing proximally the independently moveable tether. In some embodiments, the circular rim is constructed of a superelastic material, e.g., nitinol. This alignment enables the capture sheath to cover the filter and circular rim to assist with removal of the filter from the vessel. 
     In another embodiment, the filter is attached to the elongate member by a plurality of flexible struts. Each of the flexible struts is coupled at a first end to the distal end of the elongate member and coupled at a second end to the filter. The filter is contracted by rotating the elongate member, which in turn winds the flexible struts. A capture sheath is disposed about the elongate member and the filter for stowage of the filter. As the flexible struts wind, the filter is closed, and the capture sheath is able to cover the flexible struts and filter to assist in removal from the vessel. 
     The filter devices of the present invention are most useful in capturing embolic debris generated during endovascular procedures within a coronary artery, aorta, common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, basilar artery, vertebral artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery, and all other arteries carrying oxygenated blood. The filter devices are also useful in preventing distal embolization in the venous circulation, including the superior vena cava, inferior vena cava, external and internal jugular veins, brachiocephalic vein, pulmonary artery, subclavian vein, brachial vein, axillary vein, iliac vein, renal vein, femoral vein, profunda femoris vein, great saphenous vein, portal vein, splenic vein, hepatic vein, and azygous vein. 
     In a first method of using the filter device having first and second flexible members, the filter is placed in a contracted state. The distal end of the tubular member is inserted percutaneously through an artery or vein and advanced into or beyond a region of interest, typically a stenotic lesion caused by buildup of atherosclerotic plaque and/or thrombi. The filter is then expanded downstream of the vascular occlusion by operating the first and second flexible members. In this way, the filter structure conforms to the interior vessel wall with minimum gap, as the elongate tubular member lies against the luminal wall of the vessel. The elongate tubular member then acts as a platform, or guidewire, to guide therapeutic instruments to operate on the stenosis within the region of interest. After the stenotic lesion is removed by endovascular procedure(s), e.g., angioplasty, atherectomy, or stent deployment, the filter is collapsed and removed from the vessel, together with the captured embolic debris. When the filter is stowed, the flexible members are tightened against the tubular member and constricted by a capture sheath advanced distally over the filter during closure, creating a controlled closure of the filter. In this way, bunching of the filter and undesired release of the captured embolic debris are avoided. 
     In another method, using the filter device having a flexible loop, the distal end of the elongate tubular member is positioned at a region of interest within a patient&#39;s vessel. The first end of the loop is advanced distally, advancing the intermediate section through the distal port until the filter covers the lumen of the vessel. The elongate tubular member is then used to guide therapeutic catheters to operate on the stenosis at the region of interest. 
     In another method, using the parachute filter device with or without a circular rim coupled to the elongate member by a plurality of tethers, the distal end of the elongate member is first positioned within a region of interest. The capture sheath is withdrawn to release the circular rim and filter within the region of interest. Therapeutic catheters are then deployed upstream the filter. To stow the filter, the independently moveable tether is withdrawn to rotate the circular rim so that a plane defined by the circular rim or mouth of the filter is parallel to a line defined by the elongate member, thereby bringing the rim into alignment with the elongate member and capture sheath. The capture sheath is then advanced over the circular rim and filter, wherein the mouth of the filter and/or the circular rim collapses to a substantially oval shape. 
     In another method, using the filter device having a filter coupled to the elongate member by a plurality of flexible struts, the distal end of the elongate member is advanced to a region of interest within a patient&#39;s vessel. The capture sheath is withdrawn to release the filter, thereby expanding the filter within the region of interest. After completion of endovascular procedures, the elongate member is rotated, thereby winding the plurality of flexible struts to contract the filter. The capture sheath is advanced distally to cover the wound flexible struts and the filter, thereby providing tight stowage of the filter and preventing accidental release of captured emboli. 
     It will be understood that there are several advantages to using the filter devices and methods disclosed herein for capturing and removing embolic debris during endovascular procedures. For example, the filter devices (1) are particularly well suited for temporary filtration of blood in any vessel to entrap embolic debris, thereby minimizing neurologic, cognitive, and cardiac complications associated with distal embolization, (2) conform to the interior vessel wall with minimum gap, (3) can be collapsed to a uniform and predictable size, (4) can be delivered over a guidewire as a rapid exchange device, (5) can be delivered through a lumen of an angioplasty or stent deployment device, (6) may include an atraumatic distal tip to minimize vessel wall injury, (7) enable an operator to steer and deploy the filter without kinking, bending, and/or looping of the catheter because of the small size ratio of filter to catheter, (8) can pass a large occluding lesion due to their small diameter when collapsed, (9) can be used as a guidewire over which a therapeutic catheter may be advanced, and (10) can be used in adult and pediatric patients. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  depicts an embodiment of a filter device having a double side-wire loop. 
         FIG. 1B  depicts the filter device of  FIG. 1A  partially expanded. 
         FIG. 1C  depicts the filter device of  FIG. 1B  further expanded. 
         FIG. 1D  depicts the filter device of  FIG. 1C  fully expanded. 
         FIG. 1E  depicts an end view of the filter device of  FIG. 1D . 
         FIG. 1F  depicts an top view of the filter device of  FIG. 1D . 
         FIG. 1G  depicts a collapsed filter mounted on the filter device of  FIG. 1A . 
         FIG. 1H  depicts the filter of  FIG. 1G  expanded by operation of first and second side-wire loops. 
         FIG. 2  depicts the filter device of  FIG. 1H  deployed in the left common carotid artery. 
         FIG. 3A  depicts an embodiment of a filter device having an expandable flexible loop. 
         FIG. 3B  depicts the filter device of  FIG. 3A  partially expanded. 
         FIG. 3C  depicts the filter device of  FIG. 3B  fully expanded. 
         FIG. 3D  depicts the filter device of  FIG. 3C  expanded with adjusted orientation. 
         FIG. 3E  depicts the filter device of  FIG. 3D  disposed within a vessel. 
         FIG. 3F  depicts a filter device disposed about the flexible loop of  FIG. 3E . 
         FIG. 4A  depicts an embodiment of a filter device having an independently moveable tether. 
         FIG. 4B  depicts a capture sheath. 
         FIG. 4C  depicts the capture sheath of  FIG. 4B  covering the filter of  FIG. 4A . 
         FIG. 4D  depicts partial removal of the capture sheath of  FIG. 4C . 
         FIG. 4E  depicts further removal of the capture sheath of  FIG. 4D . 
         FIG. 4F  depicts complete removal of the capture sheath of  FIG. 4E . 
         FIG. 4G  depicts operation of the independently moveable tether to reorient the circular rim. 
         FIG. 4H  depicts advancement of the capture sheath over the elongate member of  FIG. 4G . 
         FIG. 4I  depicts further advancement of the capture sheath to partially cover the circular rim of  FIG. 4H . 
         FIG. 4J  depicts complete coverage of the circular rim by the capture sheath of  FIG. 4I . 
         FIG. 5A  depicts the filter device of  FIG. 4C  inserted within a stenotic region of a vessel. 
         FIG. 5B  depicts the filter device of  FIG. 5A  deployed downstream of the stenotic region. 
         FIG. 5C  depicts an angioplasty catheter advanced over the filter device of  FIG. 5B . 
         FIG. 5D  depicts retrieval of the filter device of  FIG. 5C  using a capture sheath. 
         FIG. 6A  depicts an embodiment of a filter device having a parachute filter coupled by flexible struts to an elongate member. 
         FIG. 6B  depicts a capture sheath. 
         FIG. 6C  depicts the capture sheath of  FIG. 6B  covering the filter of  FIG. 6A . 
         FIG. 6D  depicts partial removal of the capture sheath of  FIG. 6C . 
         FIG. 6E  depicts further removal of the capture sheath of  FIG. 6D . 
         FIG. 6F  depicts full expansion of the parachute filter of  FIG. 6E . 
         FIG. 6G  depicts advancement of the capture sheath over the flexible struts of  FIG. 6F . 
         FIG. 6H  depicts rotation of the elongate member and winding of the flexible struts of  FIG. 6G . 
         FIG. 6I  depicts complete coverage of the wound flexible struts and filter of  FIG. 6H . 
         FIG. 7A  depicts the filter device of  FIG. 6C  inserted through a lumen of a therapeutic catheter deployed within a stenotic lesion of a vessel. 
         FIG. 7B  depicts the filter device of  FIG. 7A  deployed downstream of the stenotic region. 
         FIG. 7C  depicts closure of the flexible struts and filter by winding of the struts and advancement of the capture sheath. 
         FIG. 8  depicts various percutaneous insertion sites for the filter devices described herein. 
     
    
    
     DETAILED DESCRIPTION 
     A filter device for temporary placement in a vessel, either an artery or vein, is provided as depicted in  FIGS. 1A through 1H .  FIG. 1A  shows elongate tubular member  10  having proximal ports  25  and distal ports  26  located at a distal region. Proximal ports  25  are located circumferentially approximately 180° from each other. Distal ports  25  are also located circumferentially approximately 180° from each other. The circumferential positioning, however, may vary between 90° and 270°, more preferably 100° to 260°, more preferably 110° to 250°, more preferably 120° to 240°, more preferably 130° to 230°, more preferably 140° to 220°, more preferably 150° to 210°, more preferably 160° to 200°, more preferably 170° to 190°, most preferably approximately 180°. 
     A first flexible member  20  passes through port  25  at a proximal end, crosses 180° over elongate member  10  at point  21 , and either is coupled externally at the distal end of elongate member  10  (not shown), or passes through distal port  26  and is coupled to the luminal wall at the interior of elongate member  10 . It will be understood that first flexible member  20  passes through proximal port  25  on one side of elongate member  10 , and passes through distal port  26  on the opposite side of the elongate member. 
     One flexible member or two flexible members may be used.  FIGS. 1A to 1H  depict the use of two flexible members  20  and  22 . As shown in  FIG. 1F , the second flexible member  22  passes through a second port  25  at a proximal end, crosses 180° over elongate member  10  in a direction opposite to that of first flexible member  20 , and either is coupled externally at the distal end of elongate member  10  (not shown), or passes through a second distal port  26  and is coupled to the luminal wall at the interior of elongate member  10 . It will be understood that second flexible member  22  passes through a second proximal port  25  on one side of elongate member  10 , and passes through a second distal port  26  on the opposite side of the elongate member. 
     First and second flexible members  20  and  22  may extend to the proximal end of elongate tubular member  10 , or may be attached to the distal end of elongate member  15  which is slideably disposed within the lumen of tubular member  10 , as depicted in  FIG. 1A . When elongate member  15  is advanced distally as shown in  FIGS. 1B ,  1 C, and  1 D, flexible members  20  and  22  advance through proximal ports  25  to progressively enlarge loops extending radially about tubular member  10 .  FIG. 1E  shows an end view of tubular member  10  and flexible member  20  extending from a proximal port  25  and through a distal port  26 , and defining a circle that includes tubular member  10 . 
       FIG. 1F  shows a top view of elongate tubular member  10 , elongate member  15 , and the double side-wire loop structure defined by first and second flexible member  20  and  22 .  FIG. 1G  depicts filter structure  30  disposed about the side-wire loop structure before expansion.  FIG. 1H  shows an expanded side-wire loop structure having filter  30  disposed thereon, the filter having opening  31  that receives blood flow and emboli, and allows passage of blood but retains emboli in the filter. The filter may comprise a mesh material or a thin film with laser cut holes. The construction and use of a filter mesh have been thoroughly discussed in earlier applications including Barbut et al., U.S. application Ser. No. 08/533,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al., U.S. Pat. No. 5,769,816, Barbut et al., U.S. application Ser. No. 08/645,762, filed May 14, 1996, and, Barbut et al., U.S. Pat. No. 5,662,671, and the contents of each of these prior disclosures are expressly incorporated herein by reference in their entirety. 
     Where a thin film with laser cut holes is used, the thin film will include any biocompatible material, such as plastic (e.g., kynar, polyethylene tetrachloride, polyethylene, or mylar). The processing used to create pores in the thin film can be either laser or chemical etching, stamping, or cutting by hand. The pores are precision machined into the filter material, thereby providing less traumatic pathways for blood flow and minimizing activation of the intravascular clotting process. Anticoagulants, such as heparin and heparinoids, may be applied to the thin film to reduce thrombi formation. In the embodiments of the filter devices that are to be used in the aorta, pore size is 500 μm or less, more preferably 400 μm or less, more preferably 300 μm or less, more preferably 200 μm or less, more preferably 100 μm or less, more preferably 50 μm or less and usually larger than at least a red blood cell. Typical dimensions include pore size of 20-500 μm, and a petal thickness of 0.0005-0.003 inches. 
       FIG. 2  shows the double side-wire loop filter of  FIGS. 1A through 1H  deployed within left common carotid artery  102 . Elongate tubular member  10  is advanced to position through left subclavian artery  106 . Tubular member  10  includes atraumatic tip  29  at a distal end to reduce vessel trauma and better navigate tight stenotic lesion  100 . Filter  30  expands about flexible members  20  and  22  within the lumen of left common carotid artery  102  to capture dislodged embolic material, e.g., calcium, atheromatous plaque, thrombi, air, and vascular debris. 
       FIGS. 3A through 3F  depict another embodiment of a filter device. Elongate tubular member  40  contains a loop of wire or other flexible material  45  within its lumen. Wire  45  has a first end, a second end, and intermediate region  47  shown in  FIG. 3A . Optional tether  50  is joined to intermediate section  47  at position  46 . A filter (not shown for clarity) is attached to the intermediate section of the wire loop and contained within the lumen of tubular member  40  before deployment. The first and/or second end of flexible loop  45  is advanced distally, causing intermediate section  47  to extend through the distal port on tubular member  40  into the lumen of the vessel, as shown in  FIGS. 3B and 3C . 
     As loop  45  is advanced distally out of its containment lumen, it grows in diameter. The flexible loop (along with attached filter) continues to grow until it nears the diameter of the vessel in which the filter is being deployed. At this point, tether  50  restrains wire loop  45 , and is operated independently as shown in  FIG. 3D  to change the orientation of the plane described by the loop. The plane of loop  45  is substantially parallel to the axis of tubular member  40  shown in  FIG. 3C , but with operation of tether  50  as shown in  FIG. 3E , the plane described by the loop is substantially perpendicular to the longitudinal axis of tubular member  40  and vessel  101 .  FIG. 3F  shows final deployment of wire loop  45  and filter  30  within vessel  101 . Loop  45  describes a plane that is substantially perpendicular to the longitudinal axis of the vessel, and the loop has reached a diameter such that the loop is in complete or nearly complete contact with the luminal wall of the vessel, thus forcing all or nearly all blood to flow through the filter material. 
     According to this embodiment, tubular member  40  may be constructed of a diameter of 0.04 inches, including the filter contained within the lumen, so that it can be delivered through a guidewire lumen of a percutaneous transluminal angioplasty balloon or stent delivery catheter. This device may also be configured so that the distal tip of tubular member  40  has a diameter of approximately 0.035 inches (or larger) to allow for ease of packaging of the filter and its wire loop within the containment lumen. The entire device would include a distal filter containment tip of tubular member  40  having a 0.035 inch outer diameter (OD) with an attached 0.014 inch diameter wire extending proximally from the tip. In use, the 0.014 inch diameter segment would be covered by a removable sheath having 0.035 inch OD. After delivery and deployment of the filter, the sheath is removed, leaving the 0.014 inch diameter wire in place, and holding the filter the 0.014 inch diameter wire is then used to facilitate treatment of the vessel by advancing over the wire standard therapeutic over the wire catheter devices. 
     The wire loop can be made (preformed) of shape memory alloys, such as nitinol, and may be designed so that the tether is not needed to achieve proper orientation for filter deployment. The loop may alternatively be made of plastic or any other material that would facilitate deployment of the filter, so that the lumen of the vessel is completely covered by the filter and all blood flows through the filter. 
     Retraction and removal of the filter may be accomplished by reversing the process of deployment, or by use of a separate, and typically a larger diameter capture sheath the capture sheath is advanced over the 0.014 inch diameter segment of the filter device, the filter withdrawn proximally into the distal end of the capture sheath, and both devices are removed together. 
       FIGS. 4A through 4J  depict the design, deployment, use, and retrieval of an alternative filter device for capturing debris that flow downstream from an interventional site in a patient&#39;s vessel.  FIG. 4A  shows filter  30  which takes on a substantially conical shape and is designed so that its opening, or mouth  74 , can expand to completely or nearly completely fills the lumen of a vessel. The filter extends distally from mouth  74  of the filter and provides an area where debris is trapped. The mouth of filter  30  may, in certain embodiment, include circular rim  77  which is a frame comprised of a bendable material, preferably a plastic or superelastic material, e.g., nitinol. Filter  30  is held in position within a vessel by means of a plurality of tethers  76 , wherein the number of tethers are two or more, more preferably three or more. An independently operable tether  75  is also attached to rim  77 . The tethers are attached at equidistant points around the mouth of the filter. Tethers  76  extend proximally and are attached to elongate tubular member  60 . The tethers are of substantially equal lengths, such that the plane described by the mouth of the filter is maintained in a position substantially perpendicular to the longitudinal axis of the vessel. Second elongate member  65  is slideably disposed within elongate tubular member  60 , and is attached to independently moveable tether  75  at a distal end of member  65 . Tubular member  60  is sized to permit typically therapeutic and diagnostic devices to be delivered over the filter guidewire while the filter is deployed at a distal end. 
     As shown in  FIG. 4B , during delivery and removal of the filter to and from its deployment site, capture sheath  70  is used to contain filter  30  to prevent it from catching and injuring the vessel wall during movement, and to retain and remove from the patient debris captured by the filter. Once the filter is at the region of interest, it is pushed from the distal end of capture sheath  70 . To retrieve the filter, it is pulled back into capture sheath  70  and removed from the patient. Alternatively, separate delivery and retrieval sheaths may be used. For example, where a large amount of debris is collected by the filter, a larger diameter retrieval sheath may be required. 
       FIG. 4B  shows filter  30  and tethers  76  folded and packaged within the containment area at the distal end of delivery sheath  70  and ready for deployment within a region of interest a patient&#39;s vessel. In certain embodiments, the distal end  66  of tubular member  60  is larger in diameter than the body of tubular member  60  and acts as a plunger that is used to push the filter out of the containment area at the distal end of sheath  70 .  FIG. 4D  shows sheath  70  being pulled proximally relative to tubular member  60 , thereby causing the filter to be ejected from the distal end of sheath  70 . The filter begins to expand as it leaves the sheath. Alternatively, tubular member  60  may be pushed distally relative to sheath  70  to cause ejection of filter  30 . 
       FIG. 4E  shows the filter fully ejected from sheath  70  and deployed. Filter mouth  74  completely or nearly completely fills the lumen of the vessel in which it is deployed. Circular rim  77 , when use, aids in full expansion of the filter.  FIG. 4F  shows complete removal of sheath  70  from tubular member  60  so that member  60  can act as a guidewire and is ready to receive and provide support and guidance for other therapeutic devices that are to be delivered to the area of interest within the vessel. 
       FIG. 4G  shows the beginning of filter retrieval process. Elongate member  65  is retracted proximally relatively to tubular member  60 . Independently moveable tether  75  attached to elongate member  65  is thereby pulled proximally, and this action tilts the mouth of the filter from its fully deployed position and readies it to be pulled into capture sheath  70 . Just prior to retrieval, the plane described by the mouth of the filter is positioned substantially parallel to the longitudinal axis of the vessel.  FIG. 4H  shows capture sheath  70  delivered over tubular member  60  and ready to be further advanced to cover filter  30  and the debris it contains.  FIG. 4I  shows capture sheath  70  advancing and capturing filter  30 . As filter  30  enters sheath  70 , the filter mouth folds upon itself in much the same manner as it was loaded into sheath  70  before deployment. Alternatively, once the distal end of sheath  70  has advanced to the filter, tubular member  60  and elongate member  65  may be pulled proximally relative to sheath  70 , thus pulling the filter inside the distal end of sheath  70 .  FIG. 4J  shows filter  30  fully retracted inside the distal end of capture sheath  70 . The entire filter system can then be removed from the patient. 
       FIG. 5A  depicts the filter device of  FIG. 4C  inserted within stenotic lesion  100  of vessel  101 .  FIG. 5B  shows the filter device of  FIG. 5A  after deployment of filter  30  downstream stenotic lesion  100 . After removal of capture sheath  70 , tubular member  60  serves as a guidewire for delivering a therapeutic catheter, such as angioplasty catheter  200 , as shown in  FIG. 5C . Angioplasty catheter  200  includes balloon  205  in a distal region thereof, and carries tubular member  60  within guidewire lumen  210 . Atherectomy and stent deployment catheters may alternatively be used in place of or in addition of the angioplasty catheter depicted in  FIG. 5C . After inflation of angioplasty balloon  205  to compress stenotic lesion  100 , the balloon is deflated and the angioplasty catheter  200  is removed from the patient&#39;s vessel. Capture sheath  70  is then advanced along tubular member  60  to retrieve filter  30  as shown in  FIG. 5D . 
       FIGS. 6A through 61  depict the design, deployment, use, and retrieval of another filter device for capturing debris that flow downstream from an interventional site in a patient&#39;s vessel.  FIG. 6A  shows the main components of the filter and delivery system, while  FIG. 6B  shows the capture sheath. Filter  30  in  FIG. 6A  is substantially conical and designed so that its opening, or mouth  91 , expands to completely or nearly completely fill the lumen of a vessel. The filter material then extends distally (downstream) from the mouth of the filter and provides an area where debris is captured. Filter  30  is held in position in a vessel by flexible struts  90  attached at equidistant point around the mouth of the filter. The flexible struts extend proximally to elongate member  80  to which the struts are attached. A minimum of three flexible struts is needed, while five flexible struts are shown in  FIG. 6A . 
     Struts  90  may be constructed of a superelastic material, preferably a shape memory material, such as nitinol. Struts  90  are preformed and attached to elongate member  80  so that when the struts are advanced distally and freed from containment sheath  85 . The struts then expand outward to open mouth  91  of filter  30 , so that the filter substantially fills the vessel in which it is deployed. The struts are of substantially equal lengths so that the plane described by the mouth of filter  30  is maintained in a position substantially perpendicular to the longitudinal axis of the vessel. Struts  90  may also be taper ground in any number of ways so that struts  90  are smaller at their distal ends and can more easily conform to the vessel wall. 
     Surrounding elongate member  80  is capture sheath  85 . The majority of the length of sheath  85 , from its proximal end to near its distal end, has a diameter adapted to pass other interventional devices after the filter has been deployed. As such, sheath  85  may also serve as a guide wire. During delivery and removal of filter to and from its deployment site, sheath  85  contains filter  30  to prevent it from catching or injuring the vessel wall, and to retain and remove from the patient debris captured within the filter. When filter  30  reaches a region of interest, filter  30  is pushed distally from the distal end of capture sheath  85 . To retrieve filter  30 , the filter is pulled proximally into sheath  85 , or sheath  85  is advanced over filter  30 , and the combination is removed from the patient. 
       FIG. 6C  shows filter  30  and struts  90  packaged within the containment area at the distal end of capture sheath  85 . As shown, filter  30  is ready for deployment. The distal end of sheath  85  has a larger diameter than elongate member  80  to provide adequate space for storage of struts  90 , filter  30 , and debris captured within filter  30 . 
       FIG. 6D  shows elongate member  80  being pushed distally relative to sheath  85 , which causes filter  30  to be ejected from the distal end of sheath  85 . Slight rotation of elongate member  80  during deployment may assist with deployment. Filter  30  begins to expand as it leaves sheath  85 . Alternatively, sheath  85  may be pulled proximally relatively to elongate member  80  to release filter  30 . 
       FIG. 6E  shows filter  30  fully ejected from sheath  85 . Preformed struts  90  are beginning to leave sheath  85  and are expanding outward to open mouth  91  of filter  30 .  FIG. 6F  shows struts  90  completely free of sheath  85  and fully expanding filter  30 . Sheath  85  is now ready to function as a guidewire to receive and provide support for any other device, including therapeutic catheters, which are to be delivered to the region of interest. 
       FIG. 6G  shows the beginning of the filter retrieval process. Elongate member  80  is pulled proximally relative to sheath  85 , and this action causes struts  90  to begin collapsing as they enter the containment area at the distal end of sheath  85 . The filter mouth begins to close, trapping debris inside filter  30 .  FIG. 6H  shows struts  90  completely withdrawn sheath  85 . As filter  30  begins to enter sheath  85 , elongate member  80  is rotated as it is pulled proximally. This twisting action winds filter  30  and compacts the filter, which assists re-entering sheath  85 .  FIG. 6I  shows filter  30  retracted inside the distal end of sheath  85 . Filter  30  has been twisted and compacted into its containment area. The entire filter system can now be removed from the patient&#39;s vessel. 
     The filtration devices described herein can be used not only as guidewires to receive and provide support for any other device, but may also be advanced through the guidewire lumen of a therapeutic catheter once in place. For example, a conventional guidewire may be positioned within a vessel crossing a region of interest. A therapeutic catheter is then advanced over the conventional guidewire so that the therapeutic instrument lies within the region of interest. The conventional guidewire is then withdrawn, and a guidewire filter as described herein is advanced through the guidewire lumen of the therapeutic catheter.  FIG. 7A , for example, shows stent deployment catheter  250  having stent  255  disposed on a distal region, and positioned across stenotic lesion  100  of vessel  101 . The stent can be either self expanding or deployed by the action of a dilatation balloon. A filter guidewire as shown in  FIG. 6C  is advanced through guidewire lumen  260  of catheter  250  until filter  30  passes distally beyond catheter  250  and downstream of lesion  100 . Sheath  85  is withdrawn and filter  30  is deployed within vessel  101  as shown in  FIG. 7B . Stent  255  is then expanded to increase the luminal diameter across lesion  100 , and catheter  250  is withdrawn from the vessel as shown in  FIG. 7C . The filter is then captured by sheath  85  as described in  FIG. 6H , and the filter guidewire is removed from the patient&#39;s vessel. Alternatively, therapeutic catheter  250 , sheath  85 , and filter  30  may be simultaneously removed after stent deployment. 
     Various percutaneous insertion sites for the filter devices disclosed herein are depicted in  FIG. 8 . The filter device can be inserted through an incision on right subclavian artery  111 , left subclavian artery  106 , right brachial artery  118 , left brachial artery  115 , right femoral artery  125 , or left femoral artery  120  to enter a patient&#39;s arterial circulation. The double side-wire loop filter of  FIG. 1H  having elongate tubular member  10  is shown inserted through left subclavian artery  106  or left femoral artery  120  and deployed within left common carotid artery  102 . The filter device can also be inserted through an incision on right subclavian vein  110 , left subclavian vein  107 , right cubital vein  119 , left cubital vein  116 , right femoral vein  126 , or left femoral vein  121  to enter a patient&#39;s venous circulation. The double side-wire loop filter of  FIG. 1H  is shown inserted through right subclavian vein  110  and deployed within the superior vena cava. The double side-wire loop filter of  FIG. 1H  is also shown inserted through right femoral vein  126  and deployed within the inferior vena cava. 
     The length of the elongate member which typically will serve as a guidewire is generally between 30 and 300 centimeters, preferably approximately between 50 and 180 centimeters. The outer diameter of the guidewire will generally be between 0.01 and 0.05 inches, preferably approximately between 0.014 and 0.035 inches. The filter will be capable of expanding to an outer diameter of at least 0.2 centimeters, more preferably at least 0.5 centimeters, more preferably at least 1.0 centimeters, more preferably at least 1.5 centimeters, more preferably at least 2.0 centimeters, more preferably at least 2.5 centimeters, more preferably at least 3.0 centimeters, more preferably at least 3.5 centimeters, more preferably at least 4.0 centimeters, more preferably at least 4.5 centimeters, more preferably at least 5.0 centimeters. The filter will be capable of contracting to an outer diameter of between 0.05 and 2.0 millimeters, preferably approximately between 0.8 and 1.2 millimeters. The outer diameter of the capture sheath will generally be between 0.5 and 2.2 millimeters, preferably approximately between 0.9 and 1.9 millimeters. These ranges cover suitable diameters for both pediatric and adult use. The foregoing ranges are set forth solely for the purpose of illustrating typical device dimensions. The actual dimensions of a device constructed according to the principles of the present invention may obviously vary outside of the listed ranges without departing from those basic principles. 
     Although the foregoing invention has, for the purposes of clarity and understanding, been described in some detail by way of illustration and example, it will be obvious that certain changes and modifications may be practiced which will still fall within the scope of the appended claims. Moreover, it will be understood that each and every feature described for any given embodiment or in any reference incorporated herein, can be combined with any of the other embodiments described herein.