CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/428,653, filed Dec. 30, 2010; U.S. Provisional Application No. 61/493,447, filed Jun. 4, 2011; U.S. Provisional Application No. 61/550,889, filed Oct. 24, 2011; and U.S. Provisional Application No. 61/556,142, filed Nov. 4, 2011, the entire contents of which are hereby incorporated by reference and should be considered a part of this specification. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    In general, the disclosure relates to methods and apparatuses for filtering blood. The filtration systems can be catheter-based for insertion into a patient&#39;s vascular system. 
         [0004]    2. Description of the Related Art 
         [0005]    Thromboembolic disorders, such as stroke, pulmonary embolism, peripheral thrombosis, atherosclerosis, and the like, affect many people. These disorders are a major cause of morbidity and mortality in the United States and throughout the world. Thromboembolic events are characterized by an occlusion of a blood vessel. The occlusion can be caused by a clot which is viscoelastic (jelly-like) and is comprised of platelets, fibrinogen, and other clotting proteins. 
         [0006]    Percutaneous aortic valve replacement has been in development for some time now and stroke rates related to this procedure are between four and twenty percent. During catheter delivery and valve implantation plaque or other material may be dislodged from the vasculature and may travel through the carotid circulation and into the brain. When an artery is occluded by a clot or other embolic material, tissue ischemia (lack of oxygen and nutrients) develops. The ischemia will progress to tissue infarction (cell death) if the occlusion persists. Infarction does not develop or is greatly limited if the flow of blood is reestablished rapidly. Failure to reestablish blood-flow can lead to the loss of limb, angina pectoris, myocardial infarction, stroke, or even death. 
         [0007]    Occlusion of the venous circulation by thrombi leads to blood stasis which can cause numerous problems. The majority of pulmonary embolisms are caused by emboli that originate in the peripheral venous system. Reestablishing blood flow and removal of the thrombus is highly desirable. 
         [0008]    Techniques exist to reestablish blood flow in an occluded vessel. One common surgical technique, an embolectomy, involves incising a blood vessel and introducing a balloon-tipped device (such as a Fogarty catheter) to the location of the occlusion. The balloon is then inflated at a point beyond the clot and used to translate the obstructing material back to the point of incision. The obstructing material is then removed by the surgeon. While such surgical techniques have been useful, exposing a patient to surgery may be traumatic and is best avoided when possible. Additionally, the use of a Fogarty catheter may be problematic due to the possible risk of damaging the interior lining of the vessel as the catheter is being withdrawn. 
         [0009]    A common percutaneous technique is referred to as balloon angioplasty where a balloon-tipped catheter is introduced into a blood vessel, typically through an introducing catheter. The balloon-tipped catheter is then advanced to the point of the occlusion and inflated in order to dilate the stenosis. Balloon angioplasty is appropriate for treating vessel stenosis but is generally not effective for treating acute thromboembolisms. 
         [0010]    Another percutaneous technique is to place a microcatheter near the clot and infuse Streptokinase, Urokinase, or other thrombolytic agents to dissolve the clot. Unfortunately, thrombolysis typically takes hours or days to be successful. Additionally, thrombolytic agents can cause hemorrhage and in many patients the agents cannot be used at all. 
         [0011]    Another problematic area is the removal of foreign bodies. Foreign bodies introduced into the circulation can be fragments of catheters, pace-maker electrodes, guide wires, and erroneously placed embolic material such as thrombogenic coils. Retrieval devices exist for the removal of foreign bodies, some of which form a loop that can ensnare the foreign material by decreasing the size of the diameter of the loop around the foreign body. The use of such removal devices can be difficult and sometimes unsuccessful. 
         [0012]    Moreover, systems heretofore disclosed in the art are generally limited by size compatibility and the increase in vessel size as the emboli is drawn out from the distal vascular occlusion location to a more proximal location near the heart. If the embolectomy device is too large for the vessel it will not deploy correctly to capture the clot or foreign body, and if too small in diameter it cannot capture clots or foreign bodies across the entire cross section of the blood vessel. Additionally, if the embolectomy device is too small in retaining volume then as the device is retracted the excess material being removed can spill out and be carried by flow back to occlude another vessel downstream. 
         [0013]    Various thrombectomy and foreign matter removal devices have been disclosed in the art. Such devices, however, have been found to have structures which are either highly complex or lacking in sufficient retaining structure. Disadvantages associated with the devices having highly complex structure include difficulty in manufacturability as well as difficulty in use in conjunction with microcatheters. Recent developments in the removal device art features umbrella filter devices having self folding capabilities. Typically, these filters fold into a pleated condition, where the pleats extend radially and can obstruct retraction of the device into the microcatheter sheathing. 
         [0014]    Extraction systems are needed that can be easily and controllably deployed into and retracted from the circulatory system for the effective removal of clots and foreign bodies. There is also a need for systems that can be used as temporary arterial or venous filters to capture and remove thromboemboli generated during endovascular procedures. The systems should also be able to be properly positioned in the desired location. Additionally, due to difficult-to-access anatomy such as the cerebral vasculature and the neurovasculature, the systems should have a small collapsed profile. 
         [0015]    The risk of dislodging foreign bodies is also prevalent in certain surgical procedures. It is therefore further desirable that such emboli capture and removal apparatuses are similarly useful with surgical procedures such as, without limitation, cardiac valve replacement, cardiac bypass grafting, cardiac reduction, or aortic replacement. 
       SUMMARY OF THE INVENTION 
       [0016]    One aspect of the disclosure is a catheter-based endovascular system and method of use for filtering blood that captures and removes particles caused as a result of a surgical or endovascular procedures. The method and system include a first filter placed in a first vessel within the patient&#39;s vascular system and a second filter placed in a second vessel within the patient&#39;s vascular system. In this manner, the level of particulate protection is thereby increased. 
         [0017]    One aspect of the disclosure is an endovascular filtration system and method of filtering blood that protects the cerebral vasculature from embolisms instigated or foreign bodies dislodged during a surgical procedure. In this aspect, the catheter-based filtration system is disposed at a location in the patient&#39;s arterial system between the site of the surgical procedure and the cerebral vasculature. The catheter-based filtration system is inserted and deployed at the site to capture embolisms and other foreign bodies and prevent their travel to the patient&#39;s cerebral vasculature so as to avoid or minimize thromboembolic disorders such as a stroke. 
         [0018]    One aspect of the disclosure is an endovascular filtration system and method of filtering blood that provides embolic protection to the cerebral vasculature during a cardiac or cardiothoracic surgical procedure. According to this aspect, the filtration system is a catheter-based system provided with at least a first filter and a second filter. The first filter is positioned within the brachiocephalic artery, between the aorta and the right common carotid artery, with the second filter being positioned within the left common carotid artery. 
         [0019]    One aspect of the disclosure is a catheter-based endovascular filtration system including a first filter and a second filter, wherein the system is inserted into the patient&#39;s right brachial or right radial artery. The system is then advanced through the patient&#39;s right subclavian artery and into the brachiocephalic artery. Alternately, the system may be inserted directly into the right subclavian artery. At a position within the brachiocephalic trunk between the aorta and the right common carotid artery, the catheter-based system is manipulated to deploy the first filter. The second filter is then advanced through or adjacent to the deployed first filter into the aorta and then into the left common carotid artery. Once in position within the left common carotid artery the catheter-based system is further actuated to deploy the second filter. After the surgical procedure is completed, the second filter and the first filter are, respectively, collapsed and withdrawn from the arteries and the catheter-based filtration system is removed from the patient&#39;s vasculature. In an alternate embodiment, either or both the first and second filters may be detached from the filtration system and left inside the patient for a therapeutic period of time. 
         [0020]    One aspect of the disclosure is a catheter-based filtration system comprising a handle, a first sheath, a first filter, a second sheath and a second filter. The first and second sheaths are independently actuatable. The handle can be a single or multiple section handle. The first sheath is translatable relative to the first filter to enact deployment of the first filter in a first vessel. The second sheath is articulatable from a first configuration to one or more other configurations. The extent of articulation applied to the second sheath is determined by the anatomy of a second vessel to which access is to be gained. The second filter is advanced through the articulated second sheath and into the vessel accessed by the second sheath and, thereafter, deployed in the second vessel. Actuation of the first sheath relative to the first filter and articulation of the second filter is provided via the handle. In some embodiments, the handle includes a locking mechanism configured to lock the first sheath relative to the second sheath. In certain embodiments, the handle also includes a distal flush port. 
         [0021]    In some aspects of the disclosure, the second filter is carried on a guiding member having a guidewire lumen extending therethrough. In certain aspects, the guiding member is a catheter shaft. A guiding member having a guidewire lumen allows the user to precisely deliver the second filter by advancing the filter system over the guidewire. The guiding member can be configured to have increased column strength to aid advancement of the second filter. In some aspects, the guiding member includes a flexible portion to better position the second filter within the vessel. 
         [0022]    In some aspects the first sheath is a proximal sheath, the first filter is a proximal filter, the second sheath is a distal sheath, and the second filter is a distal filter. The proximal sheath is provided with a proximal hub housed within and in sliding engagement with the handle. Movement of the proximal hub causes translation of the proximal sheath relative to the proximal filter. The distal sheath includes a distal shaft section and a distal articulatable sheath section. A wire is provided from the handle to the distal articulatable sheath section. Manipulation of the handle places tension on the wire causing the distal articulatable sheath section to articulate from a first configuration to one or more other configurations. The articulatable distal sheath is capable of rotation, translation, and deflection (both in a single plane and both partially in a first plane and partially in a second, different plane). In some embodiments, the handle includes a locking mechanism to prevent the articulatable distal sheath from deviating from a desired configuration. In certain embodiments, the locking mechanism may lock automatically when the operator actuates a control or releases the handle. 
         [0023]    In some aspects the proximal filter and the distal filter are both self-expanding. The proximal filter and the distal filter both may comprise an oblique truncated cone shape. Movement of the proximal sheath relative to the proximal filter causes the proximal filter to expand and deploy against the inside wall of a first vessel. The distal filter is then advanced through or adjacent to the distal shaft and distal articulatable sheath into expanding engagement against the inner wall of a second vessel. In some embodiments, a tethering member extends from the proximal sheath to the proximal filter to help draw the proximal filter opening toward the first vessel wall. 
         [0024]    Another aspect of the disclosure is a single filter embolic protection device comprising a single filter device comprising a sheath, a filter shaft, and a filter assembly. In some aspects, the filter assembly is designed to accommodate a catheter-based device passing between the filter and the vessel wall. In certain embodiments, the filter assembly may include a channel, a gap, or an inflatable annulus. The filter assembly may also include one or more filter lobes. In another embodiment, the filter assembly may resemble an umbrella having a plurality of tines and a filter element connecting each tine. The filter assembly may alternatively include a plurality of overlapping filter portions, wherein a catheter may pass between a first filter portion and a second filter portion of the filter assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  illustrates an exemplary prior art catheter being advanced through a portion of a subject&#39;s vasculature. 
           [0026]      FIGS. 1A-1D  illustrate an exemplary dual filter system. 
           [0027]      FIGS. 1E and 1F  illustrate exemplary proximal filters. 
           [0028]      FIGS. 2A-2D  illustrate an exemplary method of delivering and deploying a dual filter system 
           [0029]      FIGS. 3-5  illustrate a portion of an exemplary delivery procedure for positioning a blood filter. 
           [0030]      FIGS. 6A and 6B  illustrate an exemplary embodiment of an articulating distal sheath. 
           [0031]      FIGS. 7A-7C  illustrate a portion of an exemplary filter system. 
           [0032]      FIGS. 8A-8C  illustrate an exemplary pull wire. 
           [0033]      FIGS. 9A-9C  show an exemplary embodiment of a distal sheath with slots formed therein. 
           [0034]      FIGS. 9D-9E  show an exemplary embodiment of a distal sheath capable of deflecting in multiple directions. 
           [0035]      FIGS. 9F and 9G  illustrate exemplary guidewire lumen locations in the distal sheath. 
           [0036]      FIGS. 10A and 10B  illustrate a portion of exemplary distal sheath adapted to be multi-directional. 
           [0037]      FIGS. 11A-11E  illustrate merely exemplary anatomical variations that can exist. 
           [0038]      FIGS. 12A and 12B  illustrate an exemplary curvature of a distal sheath to help position the distal filter properly in the left common carotid artery. 
           [0039]      FIGS. 13A and 13B  illustrate alternative distal sheath and distal shaft portions of an exemplary filter system. 
           [0040]      FIG. 14  illustrates a portion of an exemplary system including a distal shaft and a distal sheath. 
           [0041]      FIGS. 15A-15D  illustrate alternative embodiments of the coupling of the distal shaft and distal sheath. 
           [0042]      FIG. 16  illustrates an exemplary embodiment of a filter system in which the distal sheath is biased to a curved configuration. 
           [0043]      FIG. 17  illustrates a portion of an alternative filter system. 
           [0044]      FIGS. 18A and 18B  illustrate an exemplary proximal filter. 
           [0045]      FIGS. 19A-19C ,  20 A- 20 B,  21 ,  22 A-B illustrate exemplary proximal filters. 
           [0046]      FIGS. 23A-23F  illustrate exemplary distal filters. 
           [0047]      FIGS. 24A-24C  illustrate exemplary embodiments in which the system includes at least one distal filter positioning, or stabilizing, anchor. 
           [0048]      FIGS. 25A-25D  illustrate an exemplary embodiment of coupling a distal filter to a docking wire inside of the subject. 
           [0049]      FIGS. 26A-26G  illustrate an exemplary method of preparing an exemplary distal filter assembly for use. 
           [0050]      FIGS. 27A and 27B  illustrate an exemplary embodiment in which a guiding member, secured to a distal filter before introduction into the subject is loaded into an articulatable distal sheath. 
           [0051]      FIGS. 28A-28E  illustrate an exemplary distal filter assembly in collapsed and expanded configurations. 
           [0052]      FIGS. 29A-29E  illustrate a portion of an exemplary filter system with a lower delivery and insertion profile. 
           [0053]      FIGS. 30A and 30B  illustrate a portion of an exemplary filter system. 
           [0054]      FIGS. 31A-31C  illustrate an exemplary over-the-wire routing system that includes a separate distal port for a dedicated guidewire. 
           [0055]      FIGS. 32A-32E  illustrate an exemplary routing system which includes a rapid-exchange guidewire delivery. 
           [0056]      FIGS. 33A-D  illustrates a filter system which includes a tubular core member. 
           [0057]      FIGS. 34A-C  illustrate a filter system with a flexible coupler. 
           [0058]      FIGS. 35A-E  illustrate alternate designs for a flexible coupler. 
           [0059]      FIGS. 36A-C  illustrate a method of using a tethering member. 
           [0060]      FIGS. 36D-E  illustrate attachment points for a tethering member. 
           [0061]      FIGS. 37A-D  illustrate multiple embodiments for a tethering member. 
           [0062]      FIGS. 38A-D  illustrate multiple embodiments for an aortic filter designed to form a seal around a catheter. 
           [0063]      FIGS. 39A-C  illustrate an aortic filter system having multiple aortic filters. 
           [0064]      FIGS. 40A-B  exemplify multiple embodiments for an aortic filter. 
           [0065]      FIGS. 41A-B  illustrate an aortic filter having an inflatable annulus. 
           [0066]      FIG. 42  illustrates a distal portion of an exemplary filter system. 
           [0067]      FIGS. 43-46  illustrate exemplary control handles of the blood filter systems. 
           [0068]      FIGS. 47A-H  illustrate cross-sectional portions of an exemplary control handle. 
           [0069]      FIG. 48  depicts an alternative control handle with a rotary tip deflection control. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0070]    Although certain preferred embodiments and examples are disclosed below, inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses, and to modifications and equivalents thereof. Thus, the scope of the claims appended hereto is not limited by any of the particular embodiments described below. For example, in any method or process disclosed herein, the acts or operations of the method or process can be performed in any suitable sequence and are not necessarily limited to any particular disclosed sequence. Various operations can be described as multiple discrete operations in turn, in a manner that can be helpful in understanding certain embodiments; however, the order of description should not be construed to imply that these operations are order dependent. Additionally, the structures described herein can be embodied as integrated components or as separate components. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not necessarily all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments can be carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as can also be taught or suggested herein. 
         [0071]    The disclosure relates generally to intravascular blood filters used to capture foreign particles. In some embodiments the blood filter is a dual-filter system to trap foreign bodies to prevent them from traveling into the subject&#39;s right and left common carotid arteries, while in other embodiments, the blood filter is a single filter system. The filter systems described herein can, however, be used to trap particles in other blood vessels within a subject, and they can also be used outside of the vasculature. The systems described herein are generally adapted to be delivered percutaneously to a target location within a subject, but they can be delivered in any suitable way, and need not be limited to minimally-invasive procedures. 
         [0072]    Filter systems in accordance with the present invention can be utilized to reduce the occurrence of emboli entering the cerebral circulation as a consequence of any of a variety of intravascular interventions, including, but not limited to, transcatheter aortic-valve implantation (TAVI), surgical valve repair or replacement, atrial fibrillation ablation, cardiac bypass surgery, or transthoracic graft placement around the aortic arch. For example, the present filter or filters may be placed as described elsewhere herein prior to a minimally invasive or open surgical repair or replacement of a heart valve, such as the mitral or aortic valve. The filter system may alternatively be placed prior to cardiac ablation such as ablation of the pulmonary vein to treat atrial fibrillation. Ablation may be accomplished using any of a variety of energy modalities, such as RF energy, cryo, microwave or ultrasound, delivered via a catheter having a distal end positioned within the heart. The present filter systems may alternatively be placed prior to cardiac bypass surgery, or prior to transthoracic graft placement around the aortic arch, or any of a variety of other surgeries or interventions that are accompanied by a risk of cerebral embolization. 
         [0073]    In one application, the filter systems described herein are used to protect the cerebral vasculature against embolisms and other foreign bodies entering the bloodstream during a cardiac valve replacement or repair procedure. To protect both the right common carotid artery and the left common carotid artery during such procedures, the system described herein enters the aorta from the brachiocephalic artery. Once in the aortic space, there is a need to immediately navigate a 180 degree turn into the left common carotid artery. In gaining entry into the aorta from the brachiocephalic artery, use of prior art catheter devices  1  will tend to hug the outer edge of the vessel  2 , as shown in  FIG. 1 . To then gain access to the left common carotid artery  3  with such prior art devices can be a difficult maneuver due to the close proximity of the two vessels which may parallel one another, often within 1 cm of separation, as shown in, for example,  FIGS. 1-5 . This sharp turn requires a very small radius and may tend to kink the catheter reducing or eliminating a through lumen to advance accessories such as guidewires, filters, stents, and other interventional tools. The catheter-based filter systems described herein can traverse this rather abrupt essentially 180 degree turn to thereby deploy filters to protect both the right and left common carotid arteries. 
         [0074]      FIGS. 1A-1C  illustrate an exemplary filter system having control handle portion  5  and filter system  10 . In some embodiments, control handle portion  5  may include a distal flush port  4 . Filter system  10  includes proximal sheath  12 , proximal shaft  14  coupled to expandable proximal filter  16 , distal shaft  18  coupled to distal articulatable sheath  20 , distal filter  22 , and guiding member  24 .  FIG. 1B  illustrates proximal filter  16  and distal filter  22  in expanded configurations.  FIG. 1C  illustrates the system in a delivery configuration, in which proximal filter  16  (not seen in  FIG. 1C ) is in a collapsed configuration constrained within proximal sheath  12 , while distal filter  22  is in a collapsed configuration constrained within distal articulatable sheath  20 . 
         [0075]      FIG. 1D  is a sectional view of partial system  10  from  FIG. 1C . Proximal shaft  14  is co-axial with proximal sheath  12 , and proximal region  26  of proximal filter  16  is secured to proximal shaft  14 . In its collapsed configuration, proximal filter  16  is disposed within proximal sheath  12  and is disposed distally relative to proximal shaft  14 . Proximal sheath  12  is axially (distally and proximally) movable relative to proximal shaft  14  and proximal filter  16 . System  10  also includes distal sheath  20  secured to a distal region of distal shaft  18 . Distal shaft  18  is co-axial with proximal shaft  14  and proximal sheath  12 . Distal sheath  20  and distal shaft  18 , secured to one another, are axially movable relative to proximal sheath  12 , proximal shaft  14  and proximal filter  16 . System  10  also includes distal filter  22  carried by guiding member  24 . In  FIG. 1D  distal filter  22  is in a collapsed configuration within distal sheath  22 . Guiding member  24  is coaxial with distal sheath  20  and distal shaft  18  as well as proximal sheath  12  and proximal shaft  14 . Guiding member  24  is axially movable relative to distal sheath  20  and distal shaft  18  as well as proximal sheath  12  and proximal shaft  14 . Proximal sheath  12 , distal sheath  20 , and guiding member  24  are each adapted to be independently moved axially relative to one other. That is, proximal sheath  12 , distal sheath  20 , and guiding member  24  are adapted for independent axial translation relative to each of the other two components. 
         [0076]    In the embodiments in  FIGS. 1A-1F , proximal filter  16  includes support element or frame  15  and filter element  17 , while distal filter  22  includes support element  21  and filter element  23 . The support elements generally provide expansion support to the filter elements in their respective expanded configurations, while the filter elements are adapted to filter fluid, such as blood, and trap particles flowing therethrough. The expansion supports are adapted to engage the wall of the lumen in which they are expanded. The filter elements have pores therein that are sized to allow the blood to flow therethrough, but are small enough to prevent unwanted foreign particles from passing therethrough. The foreign particles are therefore trapped by and within the filter elements. 
         [0077]    In one embodiment, filter element  17  is formed of a polyurethane film mounted to frame  15 , as shown in  FIGS. 1E and 1F . Film element  17  can measure about 0.0001 inches to about 0.1 inches in thickness. In some embodiments, the film thickness measures between 0.005 and 0.05, or between 0.015 and 0.025. In some situations, it may be desirable to have a filter with a thickness less than 0.0001 or greater than 0.1 inches. Other polymers may also be used to form the filter element, in the form of a perforated sheet or woven or braided membranes. Thin membranes or woven filament filter elements may alternatively comprise metal or metal alloys, such as nitinol, stainless steel, etc. 
         [0078]    Filter element  17  has through holes  27  to allow fluid to pass and will resist the passage of the embolic material within the fluid. These holes can be circular, square, triangular or other geometric shapes. In the embodiment as shown in  FIG. 1E , an equilateral triangular shape would restrict a part larger than an inscribed circle but have an area for fluid flow nearly twice as large making the shape more efficient in filtration verses fluid volume. It is understood that similar shapes such as squares and slots would provide a similar geometric advantage. In certain embodiments, the filter holes are laser drilled into the filter membrane, but other methods can be used to achieve a similar result. In some embodiments filter holes  27  are between about 1 micron and 1000 microns (1 mm). In certain embodiments, the hole size is between 1 micron and 500 microns. In other embodiments, the hole size is between 50 microns and 150 microns. However, the hole size can be larger, depending on the location of the filter within the subject and the type of particulate sought to be trapped in the filter. 
         [0079]    In several embodiments, frame element  15  can be constructed of a shape memory material such as Nitinol, or other materials such as stainless steel or cobalt super alloy (MP35N for example) that have suitable material properties. Frame element  15  could take the form of a round wire or could also be of a rectangular or elliptical shape to preserve a smaller delivery profile. In one such embodiment, frame element  15  comprises Nitinol wire where the hoop is created from a straight piece of wire and shape set into a frame where two straight legs run longitudinally along the delivery system and create a circular distal portion onto which the filter film will be mounted. The circular or loop portion may include a radiopaque marker such as a small coil of gold, platinum iridium, or other radiopaque marker for visualization under fluoroscopy. In other embodiments, the frame element may not comprise a hoop, but include a spinal element disposed across a longitudinal length of the filter element. In still other embodiments, the filter element may not include a frame element. 
         [0080]    The shape of the filter opening or frame elements  15 ,  17  may take a circular shape when viewed axially or other shape that apposes the vessel wall. In some embodiments, such as those illustrated in  FIGS. 1E ,  1 F and  25 D, the shape of frame element  15  and filter element  17  are of an oblique truncated cone having a non-uniform or unequal length around and along the length of the conical filter  16 . In such a configuration, much like a windsock, the filter  16  would have a larger opening (upstream) diameter and a reduced ending (downstream) diameter. The unconstrained, fully expanded filter diameter can measure between 3 mm and 30 mm, but in some embodiments, the diameter may be less than 3 mm or greater than 30 mm. In some embodiments, the diameter may range between 10-25 mm or between 15-20 mm. The length of the filter may range between 10 mm and 50 mm, but the length of the filter may be less than 10 mm or greater than 50 mm. In some embodiments, the length may range between 10 mm and 30 mm or between 30 mm and 50 mm. In one embodiment, the diameter of the filter opening could measure about 15-20 mm in diameter and have a length of about 30-50 mm. A selection of different filter sizes would allow treatment of a selection of patients having different vessel sizes. 
         [0081]    In some embodiments the material of the filter element is a smooth and/or textured surface that is folded or contracted into a small delivery catheter by means of tension or compression into a lumen. A reinforcement fabric  29 , as shown in  FIG. 1F , may be added to or embedded in the filter to accommodate stresses placed on the filter material by means of the tension or compression applied. This will also reduce the stretching that may occur during delivery and retraction of filter element  17 . This reinforcement material  29  could be a polymer or metallic weave to add additional localized strength. This material could be imbedded into the polyurethane film to reduce its thickness. In one particular embodiment, this imbedded material could be a polyester weave mounted to a portion of the filter near the longitudinal frame elements where the tensile forces act upon the frame and filter material to expose and retract the filter from its delivery system. In some embodiments, the film measures between 0.0005 and 0.05, between 0.0025 and 0.025, or between 0.0015 and 0.0025 inches thick. In certain embodiments, the thickness is between 0.015 and 0.025 inches. In some situations, it may be desirable to have a filter with a thickness less than 0.0001 or greater than 0.1 inches. In some embodiments, the reinforcement fabric has a pore size between about 1 micron and about 1000 microns. In certain embodiments, the pore size is between about 50 microns and about 150 microns. While such an embodiment of the filter elements has been described for convenience with reference to proximal filter element  17 , it is understood that distal filter element  23  could similarly take such form or forms. 
         [0082]    As shown in  FIG. 1B , proximal filter  16  has a generally distally-facing opening  13 , and distal filter  22  has a generally proximally-facing opening  19 . The filters can be thought of as facing opposite directions. As described in more detail below, the distal sheath is adapted to be steered, or bent, relative to the proximal sheath and the proximal filter. As the distal sheath is steered, the relative directions in which the openings face will be adjusted. Regardless of the degree to which the distal sheath is steered, the filters are still considered to having openings facing opposite directions. For example, the distal sheath could be steered to have a 180 degree bend, in which case the filters would have openings facing in substantially the same direction. The directions of the filter openings are therefore described if the system were to assume a substantially straightened configuration, an example of which is shown in  FIG. 1B . Proximal filter element  17  tapers down in the proximal direction from support element  15 , while distal filter element  23  tapers down in the distal direction from support element  21 . A fluid, such as blood, flows through the opening and passes through the pores in the filter elements, while the filter elements are adapted to trap foreign particles therein and prevent their passage to a location downstream to the filters. 
         [0083]    In several embodiments, the filters are secured to separate system components. In the embodiment in  FIGS. 1A-1D , for example, proximal filter  16  is secured to proximal shaft  14 , while distal filter  22  is secured to guiding member  24 . In  FIGS. 1A-1D , the filters are secured to independently-actuatable components. This allows the filters to be independently positioned and controlled. Additionally, the filters are collapsed within two different tubular members in their collapsed configurations. In the embodiment in  FIGS. 1A-1D , for example, proximal filter  16  is collapsed within proximal sheath  12 , while distal filter  22  is collapsed within distal sheath  20 . In the system&#39;s delivery configuration, the filters are axially-spaced from one another; however, in an alternative embodiment, the filters may be positioned such that a first filter is located within a second filter. For example, in  FIG. 1D , distal filter  22  is distally-spaced relative to proximal filter  16 . 
         [0084]    In some embodiments the distal sheath and the proximal sheath have substantially the same outer diameter (see, e.g.,  FIGS. 1C and 1D ). When the filters are collapsed within the sheaths, the sheath portion of the system therefore has a substantially constant outer diameter, which can ease the delivery of the system through the patient&#39;s body and increase the safety of the delivery. In  FIG. 1D , distal and proximal sheaths  20  and  12  have substantially the same outer diameter, both of which have larger outer diameters than the proximal shaft  14 . Proximal shaft  14  has a larger outer diameter than distal shaft  18 , wherein distal shaft  18  is disposed within proximal shaft  14 . Guiding member  24  has a smaller diameter than distal shaft  18 . In some embodiments the proximal and distal sheaths have an outer diameter between 3 French (F) and 14 F. In certain embodiments, the outer diameter is between 4 F and 8 F. In still other embodiments, the outer diameter is between 4 F and 6 F. In some embodiments the sheaths have different outer diameters. For example, the proximal sheath can have a size of 6 F, while the distal sheath has a size of 5 F. In an alternate embodiment the proximal sheath is 5 F and the distal sheath is 4 F. A distal sheath with a smaller outer diameter than the proximal sheath reduces the delivery profile of the system and can ease delivery. In some methods of use, the filter system is advanced into the subject through an incision made in the subject&#39;s right radial artery. In a variety of medical procedures a medical instrument is advanced through a subject&#39;s femoral artery, which is larger than the right radial artery. A delivery catheter used in femoral artery access procedures has a larger outer diameter than would be allowed in a filter system advanced through a radial artery. Additionally, in some uses the filter system is advanced from the right radial artery into the aorta via the brachiocephalic trunk. The radial artery has the smallest diameter of the vessels through which the system is advanced. The radial artery therefore limits the size of the system that can be advanced into the subject when the radial artery is the access point. The outer diameters of the systems described herein, when advanced into the subject via a radial artery, are therefore smaller than the outer diameters of the guiding catheters (or sheaths) typically used when access is gained via a femoral artery. 
         [0085]      FIG. 6A  illustrates a portion of a filter delivery system in a delivery configuration. The system&#39;s delivery configuration generally refers to the configuration when both filters are in collapsed configurations within the system.  FIG. 6B  illustrates that the distal articulating sheath is independently movable with 3 degrees of freedom relative to the proximal sheath and proximal filter. In  FIG. 6A , proximal sheath  60  and distal sheath  62  are coupled together at coupling  61 . Coupling  61  can be a variety of mechanisms to couple proximal sheath  60  to distal sheath  62 . For example, coupling  61  can be an interference fit, a friction fit, a spline fitting, end to end butt fit or any other type of suitable coupling between the two sheaths. When coupled together, as shown in  FIG. 6A , the components shown in  FIG. 6B  move as a unit. For example, proximal sheath  60 , proximal shaft  64 , proximal filter  66 , distal shaft  68 , and the distal filter (not shown but within distal sheath  62 ) will rotate and translate axially (in the proximal or distal direction) as a unit. When proximal sheath  60  is retracted to allow proximal filter  66  to expand, as shown in  FIG. 6B , distal sheath  62  can be independently rotated (“R”), steered (“S”), or translated axially (“T”) (either in the proximal “P” direction or distal “D” direction). The distal sheath therefore has 3 independent degrees of freedom: axial translation, rotation, and steering. The adaptation to have 3 independent degrees of freedom is advantageous when positioning the distal sheath in a target location, details of which are described below. 
         [0086]      FIGS. 2A-2D  illustrate a merely exemplary embodiment of a method of using any of the filter systems described herein. System  10  from  FIGS. 1A-1D  is shown in the embodiment in  FIGS. 2A-2D . System  10  is advanced into the subject&#39;s right radial artery through an incision in the right arm. The system is advanced through the right subclavian artery and into the brachiocephalic trunk  11 , and a portion of the system is positioned within aorta  9  as can be seen in  FIG. 2A  (although that which is shown in  FIG. 2A  is not intended to be limiting). 
         [0087]    Proximal sheath  12  is retracted proximally to allow proximal filter support element  15  to expand to an expanded configuration against the wall of the brachiocephalic trunk  11 , as is shown in  FIG. 2B . Proximal filter element  17  is secured either directly or indirectly to support element  15 , and is therefore reconfigured to the configuration shown in  FIG. 2B . The position of distal sheath  20  can be substantially maintained while proximal sheath  12  is retracted proximally. Once expanded, the proximal filter filters blood traveling through the brachiocephalic artery  11 , and therefore filters blood traveling into the right common carotid artery  7 . The expanded proximal filter is therefore in position to prevent foreign particles from traveling into the right common carotid artery  7  and into the cerebral vasculature. 
         [0088]    Distal sheath  20  is then steered, or bent, and distal end  26  of distal sheath  20  is advanced into the left common carotid artery  13 , as shown in  FIG. 2C . Guiding member  24  is thereafter advanced distally relative to distal sheath  20 , allowing the distal support element to expand from a collapsed configuration to a deployed configuration against the wall of the left common carotid artery  13  as shown in  FIG. 2D . The distal filter element is also reconfigured into the configuration shown in  FIG. 2D . Once expanded, the distal filter filters blood traveling through the left common carotid artery  13 . The distal filter is therefore in position to trap foreign particles and prevent them from traveling into the cerebral vasculature. 
         [0089]    In several embodiments, the proximal and distal filter elements or frame elements comprise elastic or shape memory material causing the filters to expand as they exit their respective sheaths. In other embodiments, mechanical or hydraulic mechanisms may be used to expand each filter element. Once the filters are in place and expanded, an optional medical procedure can then take place, such as a valvuloplasty and/or replacement heart valve procedure. Any plaque or thrombus dislodged during the heart valve procedure that enters into the brachiocephalic trunk or the left common carotid artery will be trapped in the filters. 
         [0090]    The filter system can thereafter be removed from the subject (or at any point in the procedure). In an exemplary embodiment, distal filter  22  is first retrieved back within distal sheath  20  to the collapsed configuration. To do this, guiding member  24  is retracted proximally relative to distal sheath  20 . This relative axial movement causes distal sheath  20  to engage strut  28  and begin to move strut  28  towards guiding member  24 . Support element  21 , which is coupled to strut  28 , begins to collapse upon the collapse of strut  28 . Filter element  23  therefore begins to collapse as well. Continued relative axial movement between guiding member  24  and distal sheath  20  continues to collapse strut  28 , support element  21 , and filter element  23  until distal filter  22  is retrieved and re-collapsed back within distal sheath  20  (as shown in  FIG. 2C ). Any foreign particles trapped within distal filter element  23  are contained therein as the distal filter is re-sheathed. Distal sheath  20  is then steered into the configuration shown in  FIG. 2B , and proximal sheath is then advanced distally relative to proximal filter  16 . This causes proximal filter  16  to collapse around distal shaft  18 , trapping any particles within the collapsed proximal filter. Proximal sheath  12  continues to be moved distally towards distal sheath  20  until in the position shown in  FIG. 2A . The entire system  10  can then be removed from the subject. 
         [0091]    In any of the embodiments mentioned herein, the filter or filters may alternatively be detached from the delivery catheter, and the delivery catheter removed leaving the filter behind. The filter or filters can be left in place permanently, or retrieved by snaring it with a retrieval catheter following a post procedure treatment period of time. Alternatively, the filters may remain attached to the catheter, and the catheter may be left in place post procedure for the treatment period of time. That treatment period may be at least one day, one week, three weeks, five weeks or more, depending upon the clinical circumstances. Patients with an indwelling filter or filters may be administered any of a variety of thrombolytic or anticoagulant therapies, including tissue plasminogen activator, streptokinase, coumadin, heparin and others known in the art. 
         [0092]    An exemplary advantage of the systems described herein is that the delivery and retrieval system are integrated into the same catheter that stays in place during the procedure. Unloading and loading of different catheters, sheaths, or other components is therefore unnecessary. Having a system that performs both delivery and retrieval functions also reduces procedural complexity, time, and fluoroscopy exposure time. In addition, only a minimal portion of the catheter is in the aortic arch, thus greatly reducing the change of interference with other catheters. 
         [0093]      FIGS. 7A-7B  illustrate a perspective view and sectional view, respectively, of a portion of an exemplary filter system. The system includes distal shaft  30  and distal articulatable sheath  34 , coupled via coupler  32 .  FIG. 7B  shows the sectional view of plane A. Distal sheath  34  includes steering element  38  extending down the length of the sheath and within the sheath, which is shown as a pull wire. The pull wire can be, for example without limitation, stainless steel, tungsten, alloys of cobalt such as MP35N®, or any type of cable, either comprised of a single strand or two or more strands. Distal sheath  34  also includes spine element  36 , which is shown extending down the length of the sheath on substantially the opposite side of the sheath from steering element  38 . Spine element  36  can be, for example without limitation, a ribbon or round wire. Spine element  36  can be made from, for example, stainless steel or Nitinol. Spine element  36  resists axial expansion or compression of articulatable sheath  34  upon the application of an actuating axial pull or push force applied to steering element  38 , allowing sheath  34  to be deflected toward configuration  40 , as shown in phantom in  FIG. 7A .  FIG. 7C  shows an alternative embodiment in which distal sheath  33  has a non-circular cross section. Also shown are spine element  35  and steering element  37 . 
         [0094]      FIGS. 8A-8C  illustrate views of exemplary pull wire  42  that can be incorporated into any distal sheaths described herein. Plane B in  FIG. 8B  shows a substantially circular cross-sectional shape of pull wire  42  in a proximal portion  44  of the pull wire, while plane C in  FIG. 8C  shows a flattened cross-sectional shape of distal portion  46 . Distal portion  46  has a greater width than height. The flattened cross-sectional shape of distal portion  46  provides for an improved profile, flexibility, and resistance to plastic deformation, which provides for improved straightening. 
         [0095]      FIGS. 9A-C  show an alternative embodiment of distal sheath  48  that includes slots  50  formed therein. The slots can be formed by, for example, grinding, laser cutting or other suitable material removal from distal sheath  48 . Alternatively, the slots can be the openings between spaced apart coils or filars of a spring. The characteristics of the slots can be varied to control the properties of the distal sheath. For example, the pitch, width, depth, etc., of the slots can be modified to control the flexibility, compressibility, torsional responsiveness, etc., of distal sheath  48 . More specifically, the distal sheath  48  can be formed from a length of stainless steel hypotubing. Transverse slots  50  are preferably formed on one side of the hypotubing, leaving an opposing spine which provides column strength to avoid axial compression or expansion upon application of an axial force to the pull wire and also limits deflection to a desired single plane or predetermined planes. 
         [0096]      FIG. 9B  shows a further embodiment of the distal sheath in greater detail. In this embodiment distal sheath  48  includes a first proximal articulatable hypotube section  49 . Articulatable hypotube section  49  is fixed to distal shaft  30  (not shown in  FIG. 9A ). A second distal articulatable section  51  is secured to first proximal section  49 . Pull wire  38  extends from the handle through distal shaft section  49  and is affixed to a distal portion of distal shaft portion  51 . This embodiment allows for initial curvature of distal sheath proximal section  49  in a first direction such as away from the outer vessel wall in response to proximal retraction of the pull wire  38 . Distal sheath distal section  51  is then articulated to a second curvature in a second, opposite direction. This second curvature of distal shaft section  51  is adjustable based upon tension or compression loading of the sheath section by pull wire  38 . Alternatively, a first pull wire can be attached at a distal portion of section  49  and a second pull wire can be attached at a distal portion of section  51  to allow independent deflection of the two deflection sections. 
         [0097]    As shown in  FIG. 9B , pull wire  38  in a single pull wire embodiment crosses to an opposite side of the inner lumen defined by sections  49  and  51  from the slots  50  as it transitions from the first distal sheath proximal section  49  to second distal sheath distal section  51 . As best shown in  FIG. 9C , distal sheath proximal section  49  would articulate first to initialize a first curve, concave in a first direction as the slots  50  compress in response to proximal retraction of the pull wire  38 . As the tension on pull wire  38  is increased and the slots bottom out, distal sheath distal section  51  begins to form a second curve concave in a second direction opposite to the direction of the first curve, due to pull wire  38  crossing the inner diameter of the lumen through distal sheath sections  49  and  51 . As can be seen in  FIG. 9C , as it nears and comes to the maximum extent of its articulation, distal sheath distal section  51  can take the form of a shepherd&#39;s staff or crook. 
         [0098]    Distal sheath proximal section  49  could take the form of a tubular slotted element or a pre-shaped curve that utilizes a memory material such as Nitinol or any other material exhibiting suitable properties. In some embodiments outer diameter of distal sheath proximal section  49  is between 0.02 inches and 0.2 inches. In certain embodiments, the outer diameter is between 0.05 inches and 0.1 inches, or between 0.06 inches and 0.075 inches. In some embodiments, the inner diameter of distal sheath proximal section  49  is between 0.02 inches and 0.2 inches. In certain embodiments, the inner diameter is between 0.03 inches and 0.08 inches or between 0.05 inches and 0.07 inches. In several embodiments, the length of distal sheath proximal section  49  may measures between 0.1 inches and 2.5 inches. In some embodiments, the length of distal sheath proximal section  49  may measure between about 0.50 inches and 1 inch or between 0.6 inches and 0.8 inches. In certain embodiments, the length of distal sheath proximal section  49  may be longer than 2.5 inches. It is understood that these sizes and proportions will vary depending on the specific application and those listed herein are not intended to be limiting. Transverse slots  50  can measure from about 0.002 inches to about 0.020 inches in width (measured in the axial direction) depending on the specific application and the degree of curvature desired. In some embodiments the slots can measure less than 0.002 inches or greater than 0.02 inches. In certain embodiments, the slots  50  can measure about 0.002 inches to 0.01 inches or between 0.006 and 0.01 inches. 
         [0099]    The curvature of proximal section  49  may be varied from about 0 degrees to 90 degrees or more depending on the width and number of the slots  50 . In several embodiments, the maximum degree of deflection ranges from about 15 degrees to about 75 degrees, from about 45 degrees to about 60 degrees. Commencement of deflection of distal section  51  can occur prior to, simultaneously with or following commencement of deflection of proximal section  49  based upon the relative stiffness of the sections or configuration of the pull wire as will be apparent to those of skill in the art. 
         [0100]    The distal sheath is configured such that the maximum net curvature between the primary axis of the catheter prior to any deflection and the distal tip axis is between about 90 and about 220 degrees. In other embodiments, the maximum deflection is between about 120 degrees and about 200 degrees, or between about 150 degrees and about 180 degrees. When the distal sheath is in its curved configuration, with a net deflection from the primary axis of at least about 150 degrees, the lateral distance between the primary axis and the distal tip ranges from about 5 mm to about 15 mm. 
         [0101]    The position of at least a second group of slots  50  may also be rotationally displaced about the axis of the tube with respect to a first group of slots to allow a first portion of the distal sheath to bend in a first plane and a second portion of the distal sheath to bend out-of-plane to access more complex anatomy as shown in  FIGS. 9D and 9E . The second set of slots  50  may be displaced circumferentially from the first set of slots by about 5 degrees to about 90 degrees. In certain embodiments, the slots are displaced from about 15 to 60 degrees or from about 20 to about 40 degrees. The curvature of the out of plane curve may vary from about 20 degrees to about 75 degrees, but in some embodiments, the out of plane curvature may be less than 20 degrees or greater than 75 degrees. In several embodiments, the curvature of the out of plane curve is from about 20 degrees to 40 degrees, from about 30 degrees to about 50 degrees, from about 40 degrees to about 60 degrees, or from about 50 degrees to 75 degrees. Alternatively, this out-of-plane bend could be achieved by prebending the tube after laser cutting the slots to create a bias or by any other method which would create a bias. The shape could also be multi-plane or bidirectional where the tube would bend in multiple directions within the same section of laser cut tube. 
         [0102]    In several embodiments, distal sheath distal section  51  is a selectable curve based upon the anatomy and vessel location relative to one another. This section  51  could also be a portion of the laser cut element or a separate construction where a flat ribbon braid could be utilized. It may also include a stiffening element or bias ribbon to resist permanent deformation. In one embodiment it would have a multitude of flat ribbons staggered in length to create a constant radius of curvature under increased loading. 
         [0103]    In some embodiments, distal sheath  34  incorporates a guidewire lumen  58  through which a guidewire may pass as shown in  FIG. 9F . Alternatively, in  FIG. 9G , the guidewire lumen is coaxial with guiding member lumen  59 . Removing the guidewire lumen from the wall of distal sheath  34  has the added benefit of increasing the distal sheath luminal cross sectional area, reducing deployment and retrieval forces, and increasing the capacity for debris within the distal sheath. 
         [0104]      FIGS. 10A and 10B  illustrate a portion of exemplary distal sheath  52  that is adapted to be multi-directional, and is specifically shown to be bi-directional. Distal sheath  52  is adapted to be steered towards the configurations  53  and  54  shown in phantom in  FIG. 10A .  FIG. 10B  is a sectional view in plane D, showing spinal element  55  and first and second steering elements  56  disposed on either side of spinal element  55 . Steering elements  56  can be similar to steering element  38  shown in  FIG. 7B . The steering elements can be disposed around the periphery of distal sheath at almost any location. 
         [0105]    Incorporating steerable functionality into tubular devices is known in the area of medical devices. Any such features can be incorporated into the systems herein, and specifically into the articulatable distal sheaths. 
         [0106]    In some embodiments the distal sheath includes radiopaque markers to visualize the distal sheath under fluoroscopy. In some embodiments the distal sheath has radiopaque markers at proximal and distal ends of the sheath to be able to visualize the ends of the sheath. 
         [0107]    An exemplary advantage of the filter systems described herein is the ability to safely and effectively position the distal sheath. In some uses, the proximal filter is deployed in a first bodily lumen, and the distal filter is deployed in a second bodily lumen different than the first. For example, as shown in  FIG. 2D , the proximal filter is deployed in the brachiocephalic trunk and the distal filter is deployed in a left common carotid artery. While both vessels extend from the aortic arch, the position of the vessel openings along the aortic arch varies from patient-to-patient. That is, the distance between the vessel openings can vary from patient to patient. Additionally, the angle at which the vessels are disposed relative to the aorta can vary from patient to patient. Additionally, the vessels do not necessarily lie within a common plane, although in many anatomical illustrations the vessels are typically shown this way. For example,  FIGS. 11A-11C  illustrate merely exemplary anatomical variations that can exist.  FIG. 11A  is a top view (i.e., in the superior-to-inferior direction) of aorta  70 , showing relative positions of brachiocephalic trunk opening  72 , left common carotid artery opening  74 , and left subclavian opening  76 .  FIG. 11B  is a side sectional view of aortic  78  illustrating the relative angles at which brachiocephalic trunk  80 , left common carotid artery  82 , and left subclavian artery  84  can extend from aorta  78 .  FIG. 11C  is a side sectional view of aorta  86 , showing vessel  88  extending from aorta  86  at an angle. Any or all of the vessels extending from aorta  86  could be oriented in this manner relative to the aorta.  FIGS. 11D and 11E  illustrate that the angle of the turn required upon exiting the brachiocephalic trunk  92 / 100  and entering the left common carotid artery  94 / 102  can vary from patient to patient. Due to the patient-to-patient variability between the position of the vessels and their relative orientations, a greater amount of control of the distal sheath increases the likelihood that the distal filter will be positioned safely and effectively. For example, a sheath that only has the ability to independently perform one or two of rotation, steering, and axial translation may not be adequately adapted to properly and safely position the distal filter in the left common carotid artery. All three degrees of independent motion as provided to the distal sheaths described herein provide important clinical advantages. Typically, but without intending to be limiting, a subject&#39;s brachiocephalic trunk and left carotid artery are spaced relatively close together and are either substantially parallel or tightly acute (see, e.g.,  FIG. 11E ). 
         [0108]      FIGS. 12A and 12B  illustrates an exemplary curvature of a distal sheath to help position the distal filter properly in the left common carotid artery. In  FIGS. 12A and 12B , only a portion of the system is shown for clarity, but it can be assumed that a proximal filter is included, and in this example has been expanded in brachiocephalic trunk  111 . Distal shaft  110  is coupled to steerable distal sheath  112 . Distal sheath  112  is steered into the configuration shown in  FIG. 12B . The bend created in distal sheath  112 , and therefore the relative orientations of distal sheath  112  and left common carotid artery  113 , allow for the distal filter to be advanced from distal sheath  112  into a proper position in left common carotid  113 . In contrast, the configuration of distal sheath  114  shown in phantom in  FIG. 12A  illustrates how a certain bend created in the distal sheath can orient the distal sheath in such a way that the distal filter will be advanced directly into the wall of the left common carotid (depending on the subject&#39;s anatomy), which can injure the wall and prevent the distal filter from being properly deployed. Depending on the angulation, approach angle, spacing of the openings, etc., a general U-shaped curve (shown in phantom in  FIG. 12A ) may not be optimal for steering and accessing the left common carotid artery from the brachiocephalic trunk. 
         [0109]    In some embodiments the distal sheath is adapted to have a preset curved configuration. The preset configuration can have, for example, a preset radius of curvature (or preset radii of curvature at different points along the distal sheath). When the distal sheath is articulated to be steered to the preset configuration, continued articulation of the steering element can change the configuration of the distal sheath until is assumes the preset configuration. For example, the distal sheath can comprise a slotted tube with a spine extending along the length of the distal sheath. Upon actuation of the steering component, the distal sheath will bend until the portions of the distal sheath that define the slots engage, thus limiting the degree of the bend of the distal sheath. The curve can be preset into a configuration that increases the likelihood that the distal filter will, when advanced from the distal sheath, be properly positioned within the left common carotid artery. 
         [0110]      FIGS. 13A and 13B  illustrate alternative distal sheath and distal shaft portions of an exemplary filter system.  FIGS. 13A and 13B  only show distal shaft  120  and distal sheath  122  for clarity, but the system may also includes a proximal filter (not shown but has been deployed in brachiocephalic trunk). The distal shaft/distal sheath combination has a general S-bend configuration, with distal shaft  120  including a first bend  124  in a first direction, and distal sheath  122  configured to assume bend  126  in a second direction, wherein the first and second bends form the general S-bend configuration.  FIG. 13B  shows distal sheath  122  pulled back in the proximal direction relative to the proximal filter to seat the curved distal sheath against the bend. This both helps secure the distal sheath in place as well as reduces the cross sectional volume of the filter system that is disposed with the aorta. The distal shaft and distal sheath combination shown in  FIGS. 13A and 13B  can be incorporated into any of the filter systems described herein. 
         [0111]    Exemplary embodiments of the delivery and deployment of a multi-filter embolic protection apparatus will now be described with reference to  FIGS. 2A-2D ,  13 A,  13 B,  14 ,  1 ,  3 ,  4  and  5 . More particularly, the delivery and deployment will be described with reference to placement of the filter system in the brachiocephalic and left common carotid arteries. The preferred access for the delivery of the multi-filter system  10  is from the right radial or right brachial artery, however other access locations such as the right subclavian artery are possible. The system is then advanced through the right subclavian artery to a position within the brachiocephalic artery  11 . At this point, proximal filter  16  may be deployed within into expanding engagement with the inner lining of brachiocephalic artery  11 . Alternatively, access to the left common carotid could be gained prior to deployment of proximal filter  16 . Deployment of proximal filter  16  protects both the brachiocephalic artery  11  and the right common carotid artery  7  against emboli and other foreign bodies in the bloodstream. 
         [0112]    Entry into the aortic space, as illustrated in  FIG. 3 , is then accomplished by further advancement of the system from the brachiocephalic trunk. During this step, the filter system will tend to hug the outer portion of the brachiocephalic trunk as shown in  FIG. 4 . Initial tensioning of pull wire  38  causes distal sheath  48  to move the catheter-based filter system off the wall of the brachiocephalic artery just before the ostium or entrance into the aorta, as shown in  FIG. 4 . As the catheter path will hug the outer wall of the brachial cephalic artery, a curve directed away from this outer wall will allow additional space for the distal portion of the distal sheath to curve into the left common carotid artery, as shown in  FIG. 5 . 
         [0113]    The width of slots  50  will determine the amount of bending allowed by the tube when tension is applied via pull wire  38 . For example, a narrow width slot would allow for limited bending where a wider slot would allow for additional bending due to the gap or space removed from the tube. As the bending is limited by the slot width, a fixed shape or curve may be obtained when all slots are compressed and touching one another. Additional features such as chevrons may be cut into the tube to increase the strength of the tube when compressed. Other means of forming slots could be obtained with conventional techniques such as chemical etching, welding of individual elements, mechanical forming, metal injection molding or other conventional methods. 
         [0114]    Once in the aortic space, the distal sheath is further tensioned to adjust the curvature of the distal shaft distal section  51 , as shown in  FIG. 9B . The amount of deflection is determined by the operator of the system based on the particular patient anatomy. 
         [0115]    Other techniques to bias a catheter could be external force applications to the catheter and the vessel wall such as a protruding ribbon or wire from the catheter wall to force the catheter shaft to a preferred position within the vessel. Flaring a radial element from the catheter central axis could also position the catheter shaft to one side of the vessel wall. Yet another means would be to have a pull wire external to the catheter shaft exiting at one portion and reattaching at a more distal portion where a tension in the wire would bend or curve the catheter at a variable rate in relation to the tension applied. 
         [0116]    This multi-direction and variable curvature of the distal sheath allows the operator to easily direct the filter system, or more particularly, the distal sheath section thereof, into a select vessel such as the left common carotid artery or the left innominate artery. Furthermore, the filter system allows the operator to access the left common carotid artery without the need to separately place a guidewire in the left common carotid artery. The clinical variations of these vessels are an important reason for the operator to have a system that can access differing locations and angulations between the vessels. The filter systems described herein will provide the physician complete control when attempting to access these vessels. 
         [0117]    Once the distal sheath is oriented in the left common carotid, the handle can be manipulated by pulling it and the filter system into the bifurcation leaving the aortic vessel clear of obstruction for additional catheterizations, an example of which is shown in  FIG. 12B . At this time, distal filter  22  can be advanced through proximal shaft  14  and distal shaft  18  into expanding engagement with left common carotid artery  13 . 
         [0118]      FIG. 14  illustrates a portion of an exemplary system including distal shaft  130  and distal sheath  132 . Distal sheath is adapted to be able to be steered into what can be generally considered an S-bend configuration, a shepherd&#39;s staff configuration, or a crook configuration, comprised of first bend  131  and second bend  133  in opposite directions. Also shown is rotational orb  134 , defined by the outer surface of the distal sheath as distal shaft  130  is rotated at least 360 degrees in the direction of the arrows shown in  FIG. 14 . If a typical aorta is generally in the range from about 24 mm to about 30 mm in diameter, the radius of curvature and the first bend in the S-bend can be specified to create a rotational orb that can reside within the aorta (as shown in  FIG. 14 ), resulting in minimal interference with the vessel wall and at the same time potentially optimize access into the left common carotid artery. In other distal sheath and/or distal shaft designs, such as the one shown in  FIG. 12A , the rotational orb created by the rotation of distal shaft  110  is significantly larger, increasing the risk of interference with the vessel wall and potentially decreasing the access into the left common carotid artery. In some embodiments, the diameter of the rotation orb for a distal sheath is less than about 25 mm. 
         [0119]    Referring back to  FIG. 12A , distal sheath  112 , in some embodiments, includes a non-steerable distal section  121 , an intermediate steerable section  119 , and a proximal non-steerable section  117 . When the distal sheath is actuated to be steered, only steerable portion  119  bends into a different configuration. That is, the non-steerable portions retain substantially straight configurations. The distal non-steerable portion remains straight, which can allow the distal filter to be advanced into a proper position in the left common carotid artery. 
         [0120]    While  FIG. 12A  shows distal sheath  112  in a bent configuration, the distal sheath is also positioned within the lumen of the aorta. In this position, the distal sheath can interfere with any other medical device or instrument that is being advanced through the aorta. For example, in aortic valve replacement procedures, delivery device  116 , with a replacement aortic valve disposed therein, is delivered through the aorta as shown in  FIG. 12B . If components of the filter system are disposed within the aorta during this time, delivery device  116  and the filter system can hit each other, potentially damaging either or both systems. The delivery device  116  can also dislodge one or both filters if they are in the expanded configurations. The filter system can additionally prevent the delivery device  116  from being advanced through the aorta. To reduce the risk of contact between delivery device  116  and distal sheath  112 , distal sheath  112  (and distal shaft  110 ) is translated in the proximal direction relative to the proximal filter (which in this embodiment has already been expanded but is not shown), as is shown in  FIG. 12B . Distal sheath  112  is pulled back until the inner curvature of distal sheath  112  is seated snugly with the vasculature  115  disposed between the brachiocephalic trunk  111  and the left common carotid artery  113 . This additional seating step helps secure the distal sheath in place within the subject, as well as minimize the amount of the filter system present in the aortic arch. This additional seating step can be incorporated into any of the methods described herein, and is an exemplary advantage of having a distal sheath that has three degrees of independent motion relative to the proximal filter. The combination of independent rotation, steering, and axial translation can be clinically significant to ensure the distal filter is properly positioned in the lumen, as well as making sure the filter system does not interfere with any other medical devices being delivered to the general area inside the subject. 
         [0121]    An additional advantage of the filter systems herein is that the distal sheath, when in the position shown in  FIG. 12B , will act as a protection element against any other medical instruments being delivered through the aorta (e.g., delivery device  116 ). Even if delivery device  116  were advanced such that it did engage distal sheath  112 , distal sheath  112  is seated securely against tissue  115 , thus preventing distal sheath  112  from being dislodged. Additionally, distal sheath  112  is stronger than, for example, a wire positioned within the aorta, which can easily be dislodged when hit by delivery device  116 . 
         [0122]      FIGS. 15A-15D  illustrate alternative embodiments of the coupling of the distal shaft and distal sheath. In  FIG. 15A  distal shaft  140  is secured to distal sheath  142  by coupler  144 . Shaft  140  has a low profile to allow for the collapse of the proximal filter (see  FIG. 1C ). Shaft  140  also has column strength to allow for axial translation, has sufficient torque transmission properties, and is flexible. The shaft can have a support structure therein, such as braided stainless steel. For example, the shaft can comprise polyimide, Polyether ether ketone (PEEK), Nylon, Pebax, etc.  FIG. 15B  illustrates an alternative embodiment showing tubular element  146 , distal shaft  148 , and distal sheath  150 . Tubular element  146  can be a hypotube made from stainless steel, Nitinol, etc.  FIG. 15C  illustrates an exemplary embodiment that includes distal shaft  152 , traction member  154 , and distal sheath  156 . Traction member  154  is coupled to shaft  152  and shaft  152  is disposed therein. Traction member  154  couples to shaft  152  for torquebility, deliverability, and deployment. Traction member  154  can be, for example without limitation, a soft silicone material, polyurethane, polyimide, or other material having suitable properties.  FIG. 15D  shows an alternative embodiment in which the system includes bushing  162  disposed over distal shaft  158 , wherein distal shaft  158  is adapted to rotate within bushing  162 . The system also includes stop  160  secured to distal shaft  158  to substantially maintain the axial position of bushing  162 . When the system includes bushing  162 , distal sheath  164  can be rotated relative to the proximal sheath and the proximal filter when the distal sheath and proximal sheath are in the delivery configuration (see  FIG. 1B ). 
         [0123]      FIG. 16  illustrates an exemplary embodiment of filter system  170  in which distal sheath  172  is biased to a curved configuration  174 . The biased curved configuration is adapted to facilitate placement, delivery, and securing at least the distal filter. As shown, the distal sheath is biased to a configuration that positions the distal end of the distal sheath towards the left common carotid artery. 
         [0124]      FIG. 17  illustrates a portion of an exemplary filter system and its method of use.  FIG. 17  shows a system and portion of deployment similar to that shown in  FIG. 2D , but distal sheath  182  has been retracted proximally relative to guiding member  190  and distal filter  186 . Distal sheath  182  has been retracted substantially from the aortic arch and is substantially disposed with the brachiocephalic trunk. Guiding member  190  can have preset curve  188  adapted to closely mimic the anatomical curve between the brachiocephalic trunk and the left common carotid artery, thus minimizing the amount of the system that is disposed within the aorta. As shown, distal sheath  182  has been retracted proximally relative to proximal filter  180 . 
         [0125]      FIG. 18A  is a perspective view of a portion of an exemplary embodiment of a filter system, while  FIG. 18B  is a close-up view of a portion of the system shown in  FIG. 18A . The distal sheath and the distal filter are not shown in  FIGS. 18A and 18B  for clarity. The system includes proximal filter  200  coupled to proximal shaft  202 , and push rod  206  coupled to proximal shaft  202 . A portion of proximal sheath  204  is shown in  FIG. 18A  in a retracted position, allowing proximal filter  200  to expand to an expanded configuration. Only a portion of proximal sheath  204  is shown, but it generally extends proximally similar to push rod  206 . The proximal end of proximal shaft  202  is beveled and defines an aspiration lumen  216 , which is adapted to receive an aspirator (not shown) to apply a vacuum to aspirate debris captured within distally facing proximal filter  200 . Push rod  206  extends proximally within proximal sheath  204  and is coupled to an actuation system outside of the subject, examples of which are described below. Push rod  206  takes up less space inside proximal sheath  204  than proximal shaft  202 , providing a lower profile. 
         [0126]    The system also includes proximal seal  214  disposed on the outer surface of proximal shaft  202  and adapted to engage the inner surface of the proximal sheath. Proximal seal  214  prevents bodily fluids, such as blood, from entering the space between proximal sheath  204  and proximal shaft  202 , thus preventing bodily fluids from passing proximally into the filter system. The proximal seal can be, for example without limitation, a molded polymer. The proximal seal can also be machined as part of the proximal shaft, such that they are not considered two separate components. 
         [0127]    In some specific embodiments the push rod is between 0.001 inches and 0.05 inches in diameter. In some embodiments, the diameter is between 0.01 inches and 0.025 inches in diameter. The pushrod can be constructed from any number of polymeric or metal materials, such as stainless steel. The proximal shaft can be, for example without limitation, an extruded or molded plastic, a hypotube (e.g., stainless steel), machined plastic, metal, etc. 
         [0128]    Proximal filter  200  includes filter material  208 , which comprises pores adapted to allow blood to pass therethrough, while debris does not pass through the pores and is captured within the filter material. Proximal filter  200  also includes strut  210  that extends from proximal shaft  202  to expansion support  212 . Expansion support  212  has a generally annular shape but that is not intended to be limiting. Proximal filter  200  also has a leading portion  220  and a trailing portion  222 . Leading portion  220  generally extends further distally than trailing portion  222  to give filter  200  a generally canted configuration relative to the proximal shaft. The canted design provides for decreased radial stiffness and a better collapsed profile. Strut  210  and expansion support  212  generally provide support for filter  200  when in the expanded configuration, as shown in  FIG. 18A . 
         [0129]      FIGS. 19A-19C  illustrate exemplary embodiments of proximal filters and proximal shafts that can be incorporated into any of the systems herein. In  FIG. 19A , filter  230  has flared end  232  for improved filter-wall opposition.  FIG. 19B  shows proximal shaft  244  substantially co-axial with vessel  246  in which filter  240  is expanded. Vessel  246  and shaft  244  have common axis  242 .  FIG. 19C  illustrates longitudinal axis  254  of shaft  256  not co-axial with axis  252  of lumen  258  in which filter  250  is expanded. 
         [0130]      FIGS. 20A and 20B  illustrate an exemplary embodiment including proximal filter  260  coupled to proximal shaft  262 . Filter  260  includes filter material  264 , including slack material region  268  adapted to allow the filter to collapse easier. Filter  260  is also shown with at least one strut  270  secured to shaft  262 , and expansion support  266 . As shown in the highlighted view in  FIG. 20B , filter  260  includes seal  274 , radiopaque coil  276  (e.g., platinum), support wire  278  (e.g., Nitinol wire), and filter material  264 . Any of the features in this embodiment can be included in any of the filter systems described herein. 
         [0131]      FIG. 21  illustrates an exemplary embodiment of a proximal filter. Proximal filter  280  is coupled to proximal shaft  282 . Proximal filter  280  includes struts  286  extending from proximal shaft  282  to strut restraint  288 , which is adapted to slide axially over distal shaft  284 . Proximal filter  280  also includes filter material  290 , with pores therein, that extends from proximal shaft  282  to a location axially between proximal shaft  282  and strut restraint  288 . Debris can pass through struts  286  and become trapped within filter material  290 . When proximal filter  280  is collapsed within a proximal sheath (not shown), struts  286  elongate and move radially inward (towards distal shaft  284 ). Strut restraint  288  is adapted to move distally over distal shaft  284  to allow the struts to move radially inward and extend a greater length along distal shaft  284 . 
         [0132]      FIGS. 22A and 22B  illustrate an exemplary embodiment of a proximal filter that can be incorporated into any filter system described herein. The system includes proximal filter  300  and proximal sheath  302 , shown in a retracted position in  FIG. 22A . Proximal filter  300  includes valve elements  304  in an open configuration in  FIG. 22A . When valve elements  304  are in the open configuration, foreign particles  306  can pass through opening  308  and through the valve and become trapped in proximal filter  300 , as is shown in  FIG. 22A . To collapse proximal filter  300 , proximal sheath  302  is advanced distally relative to proximal filter  300 . As the filter begins to collapse, the valve elements are brought closer towards one another and into a closed configuration, as shown in  FIG. 22B . The closed valve prevents extrusion of debris during the recapture process. 
         [0133]    The distal filters shown are merely exemplary and other filters may be incorporated into any of the systems herein.  FIG. 23A  illustrates a portion of an exemplary filter system. The system includes guiding member  340  (distal sheath not shown), strut  342 , expansion support  344 , and filter element  346 . Strut  342  is secured directly to guiding member  340  and strut  342  is secured either directly or indirectly to expansion support  344 . Filter material  346  is secured to expansion support  344 . Distal end  348  of filter material  346  is secured to guiding member  340 . 
         [0134]      FIG. 23B  illustrates a portion of an exemplary filter system. The system includes guiding element  350 , strut support  352  secured to guiding element  350 , strut  354 , expansion support  356 , and filter material  358 . Strut support  352  can be secured to guiding element  350  in any suitable manner (e.g., bonding), and strut  354  can be secured to strut support  352  in any suitable manner. 
         [0135]      FIG. 23C  illustrates a portion of an exemplary filter system. The system includes guiding element  360 , strut support  362  secured to guiding element  360 , strut  364 , expansion support  366 , and filter material  368 . Expansion support  366  is adapted to be disposed at an angle relative to the longitudinal axis of guiding member  360  when the distal filter is in the expanded configuration. Expansion support  366  includes trailing portion  362  and leading portion  361 . Strut  364  is secured to expansion support  366  at or near leading portion  361 .  FIG. 23D  illustrates an exemplary embodiment that includes guiding member  370 , strut support  372 , strut  374 , expansion support  376 , and filter material  378 . Expansion support  376  includes leading portion  373 , and trailing portion  371 , wherein strut  374  is secured to expansion element  376  at or near trailing portion  371 . Expansion support  376  is disposed at an angle relative to the longitudinal axis of guiding member  370  when the distal filter is in the expanded configuration. 
         [0136]      FIG. 23E  illustrates an exemplary embodiment of a distal filter in an expanded configuration. Guiding member  380  is secured to strut support  382 , and the filter includes a plurality of struts  384  secured to strut support  382  and to expansion support  386 . Filter material  388  is secured to expansion support  386 . While four struts are shown, the distal filter may include any number of struts. 
         [0137]      FIG. 23F  illustrates an exemplary embodiment of a distal filter in an expanded configuration. Proximal stop  392  and distal stop  394  are secured to guiding member  390 . The distal filter includes tubular member  396  that is axially slidable over guiding member  390 , but is restricted in both directions by stops  392  and  394 . Strut  398  is secured to slidable member  396  and to expansion support  393 . Filter material  395  is secured to slidable member  396 . If member  396  slides axially relative to guiding member  390 , filter material  395  moves as well. Member  396  is also adapted to rotate in the direction “R” relative to guiding member  390 . The distal filter is therefore adapted to independently move axially and rotationally, limited in axial translation by stops  392  and  394 . The distal filter is therefore adapted such that bumping of the guiding member or the distal sheath will not disrupt the distal filter opposition, positioning, or effectiveness. 
         [0138]    As shown in  FIGS. 23A-23B , in some embodiments, the strut  342 ,  354  has a straight configuration. A straight configuration may allow for a shorter attachment between the filter and the guiding member. In other embodiments, as shown in  FIGS. 23C-23D , the strut  364 ,  374 , takes a curved configuration. In still other embodiments, the strut has two or more curves. For example, the strut may take a sinusoidal configuration and transition from a first curve to the opposite curve to aid in transition to the filter frame. In some embodiments, the first curve may have a larger radius than the opposite curve. In still other embodiments, the first curve may have a smaller radius than the opposite curve. 
         [0139]      FIGS. 24A-24C  illustrate exemplary embodiments in which the system includes at least one distal filter positioning, or stabilizing, anchor. The positioning anchor(s) can help position the distal anchor in a proper position and/or orientation within a bodily lumen. In  FIG. 24A  the system includes distal filter  400  and positioning anchor  402 . Anchor  402  includes expandable stent  404  and expandable supports  406 . Supports  406  and filter  400  are both secured to the guiding member. Anchor  402  can be any suitable type of expandable anchor, such as, for example without limitation, stent  404 . Anchor  402  can be self-expandable, expandable by an expansion mechanism, or a combination thereof. In  FIG. 24A , stent  404  can alternatively be expanded by an expansion balloon. Anchor  402  is disposed proximal to filter  400 .  FIG. 24B  illustrates an embodiment in which the system includes first and second anchors  412  and  414 , one of which is proximal to filter  410 , while the other is distal to filter  410 .  FIG. 24C  illustrates an embodiment in which anchor  422  is distal relative to filter  420 . 
         [0140]    In some embodiments the distal filter is coupled, or secured, to a guiding member that has already been advanced to a location within the subject. The distal filter is therefore coupled to the guiding member after the distal filter has been advanced into the subject, rather than when the filter is outside of the subject. Once coupled together inside the subject, the guiding member can be moved (e.g., axially translated) to control the movement of the distal filter. In some embodiments the guiding member has a first locking element adapted to engage a second locking element on the distal filter assembly such that movement of the guiding member moves the distal filter in a first direction. In some embodiments the distal filter assembly has a third locking element that is adapted to engage the first locking element of the guiding member such that movement of the guiding member in a second direction causes the distal filter to move with the guiding member in the second direction. The guiding member can therefore be locked to the distal filter such that movement of the guiding member in a first and a second direction will move the distal filter in the first and second directions. 
         [0141]    By way of example,  FIGS. 25A-25D  illustrate an exemplary embodiment of coupling the distal filter to a docking wire inside of the subject, wherein the docking wire is subsequently used to control the movement of the distal filter relative to the distal sheath. In  FIG. 25A , guide catheter  440  has been advanced through the subject until the distal end is in or near the brachiocephalic trunk  441 . A docking wire, comprising a wire  445 , locking element  442 , and tip  444 , has been advanced through guide catheter  440 , either alone, or optionally after guiding wire  446  has been advanced into position. Guiding wire  446  can be used to assist in advancing the docking wire through guide catheter  440 . As shown, the docking wire has been advanced from the distal end of guide catheter  440 . After the docking wire is advanced to the desired position, guide catheter  440 , and if guiding wire  446  is used, are removed from the subject, leaving the docking wire in place within the subject, as shown in  FIG. 25B . Next, as shown in  FIG. 25C , the filter system, including proximal sheath  448  with a proximal filter in a collapsed configuration therein (not shown), distal sheath  450 , with a distal filter assembly (not shown) partially disposed therein, is advanced over wire  445  until a locking portion of the distal filter (not shown but described in detail below) engages locking element  442 . The distal filter assembly will thereafter move (e.g., axially) with the docking wire. Proximal sheath  448  is retracted to allow proximal filter  454  to expand (see  FIG. 25D ). Distal sheath  450  is then actuated (e.g., bent, rotated, and/or translated axially) until it is in the position shown in  FIG. 25D . A straightened configuration of the distal sheath is shown in phantom in  FIG. 25D , prior to bending, proximal movement, and/or bending. The docking wire is then advanced distally relative to distal sheath  450 , which advances distal filter  456  from distal sheath  450 , allowing distal filter  456  to expand inside the left common carotid artery, as shown in  FIG. 25D . 
         [0142]      FIGS. 26A-26D  illustrate an exemplary method of preparing an exemplary distal filter assembly for use.  FIG. 26A  illustrates a portion of the filter system including proximal sheath  470 , proximal filter  472  is an expanded configuration, distal shaft  474 , and articulatable distal sheath  476 . Distal filter assembly  478  includes an elongate member  480  defining a lumen therein. Elongate member  480  is coupled to distal tip  490 . Strut  484  is secured both to strut support  482 , which is secured to elongate member  480 , and expansion support  486 . Filter element  488  has pores therein and is secured to expansion support  486  and elongate member  480 . To load distal filter assembly  478  into distal sheath  476 , loading mandrel  492  is advanced through distal tip  490  and elongate member  480  and pushed against distal tip  490  until distal filter assembly  478  is disposed within distal sheath  476 , as shown in  FIG. 26C . Distal tip  490  of the filter assembly remains substantially distal to distal sheath  476 , and is secured to the distal end of distal sheath  476 . Distal tip  490  and distal sheath  476  can be secured together by a frictional fit or other type of suitable fit that disengages as described below. Loading mandrel  492  is then removed from the distal filter and distal sheath assembly, as shown in  FIG. 26D . 
         [0143]      FIG. 26E  illustrates docking wire  500  including wire  502 , lock element  504 , and distal tip  506 . Docking wire  500  is first advanced to a desired position within the subject, such as is shown in  FIG. 25B . The assembly from  FIG. 26D  is then advanced over docking wire, wherein distal tip  490  is first advanced over the docking wire. As shown in the highlighted view in  FIG. 26F , distal tip  490  of the distal filter assembly includes first locking elements  510 , shown as barbs. As the filter/sheath assembly continues to be distally advanced relative to the docking wire, the docking wire locking element  504  pushes locks  510  outward in the direction of the arrows in  FIG. 26F . After lock  504  passes locks  510 , locks  510  spring back inwards in the direction of the arrows shown in  FIG. 26G . In this position, when docking wire  500  is advanced distally (shown in  FIG. 26F ), lock element  504  engages with lock elements  510 , and the lock element  504  pushes the distal filter assembly in the distal direction. In this manner the distal filter can be distally advanced relative to the distal sheath to expand the distal filter. Additionally, when the docking wire is retracted proximally, locking element  504  engages the distal end  512  of elongate member  480  and pulls the distal filter in the proximal direction. This is done to retrieve and/or recollapse the distal filter back into the distal sheath after it has been expanded. 
         [0144]      FIGS. 27A and 27B  illustrate an exemplary embodiment in which guiding member  540 , secured to distal filter  530  before introduction into the subject is loaded into articulatable distal sheath  524 . The system also includes proximal filter  520 , proximal sheath  522 , and distal shaft  526 .  FIG. 27B  shows the system in a delivery configuration in which both filters are collapsed. 
         [0145]      FIGS. 28A-28E  illustrate an exemplary distal filter assembly in collapsed and expanded configurations. In  FIG. 28A , distal filter assembly  550  includes a distal frame, which includes strut  554  and expansion support  555 . The distal frame is secured to floating anchor  558 , which is adapted to slide axially on elongate member  564  between distal stop  560  and proximal stop  562 , as illustrated by the arrows in  FIG. 28A . The distal filter assembly also includes membrane  552 , which has pores therein and is secured at its distal end to elongate member  564 . The distal filter assembly is secured to a guiding member, which includes wire  566  and soft distal tip  568 . The guiding member can be, for example, similar to the docking wire shown in  FIGS. 26A-26E  above, and can be secured to the distal filter assembly as described in that embodiment. 
         [0146]    The floating anchor  558  allows filter membrane  552  to return to a neutral, or at-rest, state when expanded, as shown in  FIG. 28A . In its neutral state, there is substantially no tension applied to the filter membrane. The neutral deployed state allows for optimal filter frame orientation and vessel apposition. In the neutral state shown in  FIG. 28A , floating anchor  558  is roughly mid-way between distal stop  560  and proximal stop  562 , but this is not intended to be a limiting position when the distal filter is in a neutral state. 
         [0147]      FIG. 28B  illustrates the distal filter being sheathed into distal sheath  572 . During the sheathing process, the distal filter is collapsed from an expanded configuration (see  FIG. 28A ) towards a collapsed configuration (see  FIG. 28C ). In  FIG. 28B , distal sheath  572  is moving distally relative to the distal filter. The distal end of the distal sheath  572  engages with strut  554  as it is advanced distally, causing the distal end of strut  554  to moves towards elongate member  564 . Strut  554  can be thought of as collapsing towards elongate member  564  from the configuration shown in  FIG. 28A . The force applied from distal sheath  572  to strut  554  collapses the strut, and at the same time causes floating anchor  558  to move distally on tubular member  564  towards distal stop  560 . In  FIG. 28B , floating anchor  558  has been moved distally and is engaging distal stop  560 , preventing any further distal movement of floating anchor  558 . As strut  554  is collapsed by distal sheath  572 , strut  554  will force the attachment point between strut  554  and expansion support  555  towards tubular member  564 , beginning the collapse of expansion support  555 . Distal sheath  572  continues to be advanced distally relative to the distal filter (or the distal filter is pulled proximally relative to the distal sheath, or a combination of both) until the distal filter is collapsed within distal sheath  572 , as is shown in  FIG. 28C . Filter membrane  552  is bunched to some degree when the filter is in the configuration shown in  FIG. 28C . To deploy the distal filter from the sheath, guiding member  566  is advanced distally relative to the distal sheath (or the distal sheath is moved proximally relative to the filter). The distal portions of filter membrane  552  and expansion support  555  are deployed first, as is shown in  FIG. 28D . Tension in the filter membrane prevents wadding and binding during the deployment. When strut  554  is deployed from the distal sheath, expansion support  555  and strut  554  are able to self-expand to an at-rest configuration, as shown in  FIG. 28E . Floating anchor  558  is pulled in the distal direction from the position shown in  FIG. 28D  to the position shown in  FIG. 28E  due to the expansion of strut  554 . 
         [0148]      FIGS. 29A-29E  illustrate a portion of an exemplary filter system with a lower delivery and insertion profile. In  FIG. 29A , the system includes proximal sheath  604  with a larger outer diameter than distal sheath  602 . In some embodiments proximal sheath  604  has a 6 F outer diameter, while distal sheath  602  has a 5 F outer diameter. A guiding member including distal tip  606  is disposed within the distal sheath and the proximal sheath.  FIG. 29B  illustrates tear-away introducer  608 , with receiving opening  610  and distal end  612 . Introducer is first positioned within a subject with receiving opening  610  remaining outside the patient. As shown in  FIG. 29C , the smaller diameter distal sheath is first advanced through the receiving opening of introducer  608  until the distal end of the distal sheath is disposed distal relative to the distal end of the introducer. The introducer is then split apart and removed from the subject, as shown in  FIG. 29D . The filter system can then be advanced distally through the subject. The introducer can be a 5 F introducer, which reduces the insertion and delivery profile of the system. 
         [0149]    The embodiments in  FIGS. 25A-25B  above illustrated some exemplary systems and methods for routing filter systems to a desired location within a subject, and additional exemplary embodiments will now be described.  FIGS. 30A and 30B  illustrate an exemplary embodiment similar to that which is shown in  FIGS. 27A and 27B . The filter system shows distal filter  650  and proximal filter  644  in expanded configurations. Proximal sheath  642  has been retracted to allow proximal filter  644  to expand. Distal filter, which is secured to guiding member  648 , are both advanced distally relative to distal articulating sheath  640 . The filter system does not have a dedicated guidewire that is part of the system, but distal sheath  640  is adapted to be rotated and steered to guide the system to a target location within the subject. 
         [0150]      FIGS. 31A-31C  illustrate an exemplary over-the-wire routing system that includes a separate distal port for a dedicated guidewire. A portion of the system is shown in  FIG. 31B , including distal articulating sheath  662  and proximal sheath  660  (the filters are collapsed therein).  FIG. 31B  is a highlighted view of a distal region of  FIG. 31A , showing guidewire entry port  666  near the distal end  664  of distal sheath  662 .  FIG. 31C  is a sectional view through plane A of distal sheath  662 , showing guidewire lumen  672 , spine element  678 , distal filter lumen  674 , and steering element  676  (shown as a pull wire). Guidewire lumen  672  and distal filter lumen  674  are bi-axial along a portion of distal sheath, but in region  670  guidewire lumen  672  transitions from within the wall of distal sheath  662  to being co-axial with proximal sheath  660 . 
         [0151]    To deliver the system partially shown in  FIGS. 31A-31C , a guidewire is first delivered to a target location within the subject. The guidewire can be any type of guidewire. With the guidewire in position, the proximal end of the guidewire is loaded into guidewire entry port  666 . The filter system is then tracked over the guidewire to a desired position within the subject. Once the system is in place, the guidewire is withdrawn from the subject, or it can be left in place. The proximal and distal filters can then be deployed as described in any of the embodiments herein. 
         [0152]      FIGS. 32A-32E  illustrate an exemplary routing system which includes a rapid-exchange guidewire delivery. The system includes distal articulating sheath  680  with guidewire entry port  684  and guidewire exit port  686 . The system also includes proximal sheath  682 , a distal filter secured to a guiding member (collapsed within distal sheath  680 ), and a proximal filter (collapsed within proximal sheath  682 ). After guidewire  688  is advanced into position within the patient, the proximal end of guidewire  688  is advanced into guidewire entry port  684 . Distal sheath (along with the proximal sheath) is tracked over guidewire  688  until guidewire  688  exits distal sheath  680  at guidewire exit port  686 . Including a guidewire exit port near the entry port allows for only a portion of the guidewire to be within the sheath(s), eliminating the need to have a long segment of guidewire extending proximally from the subject&#39;s entry point. As soon as the guidewire exits the exit port, the proximal end of the guidewire and the proximal sheath can both be handled. 
         [0153]      FIG. 32B  shows guidewire  688  extending through the guidewire lumen in the distal sheath and extending proximally from exit port  686 . Guidewire  688  extends adjacent proximal sheath  682  proximal to exit port  686 . In  FIG. 32B , portion  690  of proximal sheath  682  has a diameter larger than portion  692  to accommodate the proximal filter therein. Portion  692  has a smaller diameter for easier passage of the proximal sheath and guidewire.  FIG. 32C  shows a sectional view through plane  32 C- 32 C of  FIG. 32B , with guidewire  688  exterior and adjacent to proximal sheath  682 . Proximal filter  694  is in a collapsed configuration within proximal sheath  682 , and guiding member  696  is secured to a distal filter, both of which are disposed within distal shaft  698 . 
         [0154]      FIG. 32D  shows relative cross-sections of exemplary introducer  700 , and distal sheath  680  through plane  32 D- 32 D. Distal sheath  680  includes guidewire lumen  702  and distal filter lumen  704 . In some embodiments, introducer  700  is 6 F, with an inner diameter of about 0.082 inches. In comparison, the distal sheath can have a guidewire lumen of about 0.014 inches and distal filter lumen diameter of about 0.077 inches. 
         [0155]      FIG. 32E  shows a sectional view through plane  32 E- 32 E, and also illustrates the insertion through introducer  700 . Due to the smaller diameter of portion  692  of proximal sheath  682 , guidewire  688  and proximal sheath  682  more easily fit through introducer  700  than the distal sheath and portion of the proximal sheath distal to portion  692 . The size of the introducer may vary depending on the diameter of the filter system. The introducer may range in size from 4 F to 15 F. In certain embodiments, the size of the introducer is between 4 F and 8 F. Guidewire  688  may vary in diameter between 0.005 and 0.02 inches or between 0.01 and 0.015 inches. In some situations, it may be desirable to have a guidewire smaller than 0.005 inches or larger than 0.02 inches in diameter. The smaller diameter proximal portion  692  of proximal sheath  682  allows for optimal sheath and guidewire movement with the introducer sheath. In certain aspects, it may be desirable for the cross-section of proximal filter deployment member  697  to take a non-circular shape to reduce the profile of proximal sheath  682 . Guiding member  696  and distal sheath pull wire  676  are both disposed through distal shaft  698 . 
         [0156]    In certain embodiments, the guiding member is a core wire. Use of a core wire may be desirable to decrease the diameter of the filter system. A core wire is also flexible and able to access tortuous anatomies. The material and diameter of the guiding member may vary depending on the desired level of column strength or flexibility. In certain embodiments, the core wire may be tapered such that a distal section of the core wire has a smaller diameter than a proximal section of the core wire to increase flexibility at the distal section. 
         [0157]    In certain clinical scenarios, it may be desirable for the guiding member to take the form of a tubular core member having a guidewire lumen running therethrough. In several embodiments, the tubular core member is a catheter shaft. The presence of the guidewire lumen allows the user to deliver the filter system to the correct position by advancing the filter system over the guidewire. A tubular core member allows the user to select an appropriate guidewire for the procedure rather than restricting the user to the wire core shaft. A guiding member having a guidewire lumen can potentially reduce the delivery profile of the filter system by not requiring separate lumens for the guiding member and the guidewire. 
         [0158]      FIG. 33A  illustrates filter system  700  having tubular core member  720  extending along an elongate axis of filter system  700  and slidably disposed through distal shaft  716 . The distal end of tubular core member  720  is positioned in a distal, atraumatic tip  740  of filter system  700 , while the proximal end of tubular core member  720  is positioned in the control handle. The proximal end of tubular core member  720  is connected to an actuation mechanism capable of advancing tubular core member  720  distally or retracting tubular core member  720  proximally with respect to distal shaft  716 . Distal filter assembly  726  may be mounted on a distal section of tubular core member  720 . Proximal filter  704  and distal filter  726  are illustrated as formed from a plurality of struts such as a woven wire or laser cut basket, however any of the polymeric membrane filters disclosed elsewhere herein may be used in filter system  700 . 
         [0159]    In certain embodiments, tubular core member  720  defines a guidewire lumen  745 . Tubular core member  720  may have a distal guidewire entry port at the distal end of tubular core member  720  and a proximal guidewire exit port at the proximal end of tubular core member  720 . In other embodiments, the proximal guidewire port may be positioned at any position along the length of the tubular core member. 
         [0160]    The length of tubular core member  720  may range from about 50 cm to about 300 cm. In some embodiments, the length may be less than 50 cm; while in other embodiments, the length may be greater than 300 cm. In several embodiments, the length of tubular core member  720  is between about 50 and about 150 cm, between about 75 and about 125 cm, or between about 100 cm and about 150 cm. The inner diameter of tubular core member  720  may range from about 0.01 to about 0.075 cm. In other embodiments, the inner diameter of tubular core member  720  is less than 0.01 cm; while in still other embodiments, the inner diameter is greater than 0.075 cm. The outer diameter of tubular core member  720  may range from about 0.025 to about 0.1 cm. In certain embodiments, the outer diameter of tubular core member  720  is less than 0.025 cm; while in other embodiments, the inner diameter is greater than 0.1 cm. 
         [0161]    In certain clinical scenarios, it may be desirable to increase the column strength of tubular core member  720 , thus improving support and pushability to aid advancement of distal filter assembly  726  out of distal sheath  718 . In certain scenarios, tubular core member  720  may be constructed from a material stiffer than the material from which distal shaft  716  is constructed. A stiffer tubular core member  720  can help improve the column strength of filter system  700 . The tubular core member  720  may be constructed from metallic materials such as stainless steel, Nitinol, cobalt chromium (MP35N), or other alloys used in medical devices. Alternatively, tubular core member  720  may be constructed from a polymer construction such as nylon, polyester, polypropylene, polyimide, or other polymers exhibiting similar properties. In some embodiments, tubular core member  720  may be constructed from a combination of metallic materials and polymeric materials. In some embodiments, the inner diameter of tubular core member  720  is either coated with or constructed of a lubricious polymer (e.g. HDPE, PTFE, FEP, etc.). In still other embodiments, tubular core member may include reinforcements. For example, a ribbon or other stiffening member may extend along a section of tubular core member  720 . Alternatively, tubular core member  720  may have a multi-lumen profile, a first lumen for a guidewire and a second lumen for a stiffening mandrel. Tubular core member  720  may also transition from a multi-lumen profile to a single lumen profile to increase flexibility along the single lumen section of the tubular core member. In still other embodiments, tubular core member  720  may include one or more longitudinal strands dispersed within the tubular core member shaft to improve tensile strength. In some embodiments, tubular core member  720  may have a braided or coiled shaft to increase column strength. In certain embodiments, the braid consists of both metallic and polymer materials. In other embodiments, the braid consists of only metal; while in still other embodiments, the braid consists of only polymer materials. 
         [0162]    In other clinical scenarios, it may be desirable to provide more flexibility in certain sections or along the entire length of tubular core member  720 . When filter system  700  is deployed in a curved lumen, a rigid tubular core member  720  or other guiding member may pull the leading portion  732  of distal filter  736  away from the vessel wall if the distal region of tubular core member  720  or other guiding member lacks sufficient flexibility to deflect relative to filter system  700  in a tortuous anatomy. 
         [0163]    In certain embodiments, tubular core member  720  may be constructed from a more flexible material. In other embodiments, a first portion of tubular core member  720  may be constructed from a flexible material, while a second portion of tubular core member  720  is constructed from a stiffer material. Alternatively, removal of portions of tubular core member  720  may provide greater flexibility along certain sections of tubular core member  720 . For example, a series of slots, cuts, or a spiral pattern may be cut into a section of tubular core member  720  to provide a flex zone having a greater flexibility than proximal and distal adjacent portions of tubular core member  720 . The pattern of cuts may vary along the tubular core member shaft to vary flexibility along tubular core member  720 . The flexible portion may alternatively comprise a coil, helix, or interrupted helix. In other embodiments, a first portion of the tubular core member may also have a thinner wall than a second portion of the tubular core member. In still other embodiments, tubular core member  720  may be tapered to increase stiffness along a first section of the tubular core member and increase flexibility along a second section of the tubular core member. 
         [0164]    In certain embodiments, a distal section of tubular core member  720  may be more flexible than a proximal section of the tubular core member  720  using any of the methods discussed above. The length of the flexible distal section may measure from about 5 cm to about 50 cm, from about 10 to about 40 cm, or from about 15 to about 25 cm. In other embodiments, the flexible distal section may be less than 5 cm or greater than 50 cm. 
         [0165]    Several embodiments may include a flexible coupler  722  to allow distal filter assembly  726  to deflect relative to the rest of filter system  700 . In several embodiments, tubular core member  720  includes a flexible coupler  722  positioned proximal to distal filter assembly  726 . In several embodiments, flexible coupler  722  defines a lumen through which a guidewire may pass. In some embodiments, flexible coupler  722  is spliced into a gap along tubular core member  720 . In some embodiments, tubular core member  720  may comprise a distal tubular core member and a proximal tubular core member. The distal end of the proximal tubular core member may be joined to the proximal end of flexible coupler  722 , while the proximal end of the distal tubular core member is joined to the distal end of flexible coupler  722 . In still other embodiments, tubular core member  720  and flexible coupler  722  are integrally formed such as by providing core member  720  with a plurality of transverse slots as is described elsewhere herein. 
         [0166]    In some clinical scenarios, it may be desirable for flexible coupler  722  to be more flexible than tubular core member  720 , while still demonstrating properties strong enough to resist deformation under tensile loads. Flexible coupler  722  may be constructed from materials, such as polymers, multiple polymers, Nitinol, stainless steel, etc. In certain embodiments, flexible coupler  722  may be created by piercing, slotting, grooving, scoring, cutting, laser cutting or otherwise removing material from a tubular body to increase flexibility. Alternatively, a flexible coupler  722  may be integrally formed with tubular core member  720  using any of the above mentioned patterns. In another embodiment, flexible coupler  722  is created by thinning a portion of tubular core member  720  to create a more flexible region. Flexible coupler  722  may also be deformed into a serrated or bellows shape without removing any material from the tubular body. Any of the other methods discussed above to increase the flexibility of tubular core member  720  may also be applied. 
         [0167]    In some embodiments, a flexible section  738  of tubular core member  722  may be configured to be more flexible than a proximal section of tubular core member  722 . In some aspects, flexible section  738  is positioned distal to flexible coupler  722 . The length of flexible section  738  may measure from about 5 mm to about 50 mm, from about 10 to about 30 mm, or from about 20 to about 40 mm. In other embodiments, the flexible distal section may be less than 5 mm or greater than 50 mm. 
         [0168]      FIGS. 33B-D  illustrate cross sections at various positions along the dual filter system depicted in  FIG. 33A .  FIG. 33B  illustrates a cross section of filter system  700 , proximal to proximal filter assembly  704 . Guidewire  721  is disposed through a lumen defined by tubular core member  720 , and tubular core member  720  is disposed through a lumen defined by distal shaft  716 . In certain embodiments, at least a portion of distal sheath  718  may be articulated via pull wire  737 .  FIG. 33B  shows that at least a portion of pull wire  737  may be disposed through distal shaft  716 , but external to tubular core member  720 . In some embodiments, at least a portion of pull wire  737  may pass through a lumen embedded in at least a portion of the distal shaft wall or distal sheath wall. In  FIG. 33B , a portion of distal shaft  716  may be disposed through a lumen defined by proximal shaft  701 . Proximal filter frame  714  may extend through a lumen embedded in at least a portion of the proximal filter shaft wall  701 . Proximal filter shaft  701  is disposed through a lumen defined by proximal sheath  702 . 
         [0169]      FIG. 33C  depicts a cross section distal to the cross section depicted in  FIG. 33B  through distal sheath  718 . Distal sheath is illustrated in a simplified form, but typically will include all of the deflection mechanisms of  FIGS. 9A-9E , discussed above.  FIG. 33C  shows guidewire  721  disposed through a lumen defined by tubular core member  720 . At least a portion of tubular core member  720  is disposed through a lumen defined by distal sheath  718 . As depicted in  33 C, at least a portion of distal sheath  718  may be provided with a reinforcement such as an embedded coil or braid  719  to improve torqueing capabilities. In some embodiments, the entire length of distal sheath  718  may comprise a reinforcing element such as a braid. Pull wire  737  may extend through a lumen extending through at least a portion of the distal sheath  718 , and distal sheath spinal element  741  may extend through at least a portion of distal sheath  718 . In some embodiments, the outer diameter of distal sheath  718  is substantially similar to the outer diameter of proximal sheath  702 . In other embodiments, distal sheath  718  extends through a lumen defined by proximal sheath  702 . 
         [0170]      FIG. 33D  depicts a cross section distal to the cross-section depicted in  FIG. 33C .  FIG. 33D  shows guidewire  721  disposed through a lumen defined by tubular core member  720 . Tubular core member  720  is coaxial with flexible coupler  722 . In certain embodiments, the diameter of flexible coupler  722  may be larger than the diameter of tubular core member  720 . In other embodiments, flexible coupler  722  may have the same diameter as tubular core member  720 . In still other embodiments, the diameter of flexible coupler  722  may be smaller than the diameter of tubular core member  720 . In certain embodiments, the flexible coupler may not be a separate component. 
         [0171]    As shown in  FIGS. 34A-C , a tubular core member  720  coupled with a flexible coupler  722  has the advantage of providing improved column strength along a substantial length of the filter system  700 , but providing the flexibility necessary for distal filter assembly  726  to position itself independent of the position of distal shaft  716 . Flexible coupler  722  allows distal filter frame element  728  to create a better seal against the vessel wall to help prevent embolic debris from flowing between distal filter  736  and the vessel wall. 
         [0172]    A filter system having a flexible coupler  722  is deployed similarly to the method described in  FIGS. 2A-2D . In one embodiment, as distal sheath  718  is advanced into the left common carotid artery, tubular core member  720  is advanced distally relative to distal sheath  718 .  FIG. 34B  illustrates filter system  700  after tubular core member  720  is advanced into the left common carotid artery. Distal filter  736  expands and flexible coupler  722  deflects relative to filter system  700  such that distal filter frame element  728  is circumferentially apposed to the vessel wall. Strut  724  may be proximally retracted as desired to tilt the frame element  728  to improve the fit of the distal filter  736  within the vessel. 
         [0173]    In certain embodiments, the stiffness of tubular core member  720  may be further reduced during use by the operator by withdrawing the guidewire until the distal end of the guidewire is proximal to flexible coupler  722  such that the guidewire is no longer disposed within flexible coupler  722 , thus reducing stiffness. 
         [0174]      FIGS. 35A-B  illustrate a tubular body  750  suitable for use as a flexible coupler  722 . A tubular body  750  having a proximal end  754  and a distal end  756  may be formed by wrapping a ribbon or wire around a mandrel or by laser cutting a tube with a spiral pattern to form a coil. The width of spaced regions  752   a,b  between each adjacent coil loop  751  may be different in an unstressed orientation depending on the desired properties. In some embodiments, it may be desirable to provide greater flexibility, in which case, spaced region  752   b  should be wider to allow for a greater range of movement. In certain clinical scenarios, it may be desirable to provide smaller spaced regions  752   a  between each coil portion  751  to help prevent a first edge  753   a  and a second edge  753   b  of each coil portion  751  from dislodging plaque from the vessel wall or damaging the vessel wall. In an alternate embodiment, a flexible coupler  722  having wider spaced regions  752   a  between each coil portion  751  may be covered by a thin sheath such as shrink wrap tubing to provide flexibility and protect the vessel wall from flexible coupler  722 . 
         [0175]    In  FIG. 35C , a tubular body  760  having a proximal end  764  and a distal end  766  is laser cut with a plurality of slots  762 , each slot  762  having a first end  768   a  and a second end  768   b . In some embodiments, two or more slots  762  form a circumferential ring  771  around flexible coupler  722 . In several embodiments, a plurality of circumferential rings  771  is laser cut into a tubular body  760 . The plurality of circumferential rings  771  may be staggered such that a first slot of a first circumferential ring is misaligned from a first slot of a second circumferential ring. The plurality of slots  762  are configured such that flexible coupler  722  flexes angularly while retaining good torque resistance and tensile displacement resistance. 
         [0176]      FIG. 35D  depicts a flexible coupler  722  constructed from a tubular body  770  having a proximal end  774  and a distal end  776 . Tubular body  770  is laser cut with a spiral pattern, the spiral pattern having a plurality of interlocking ring portions, wherein a first interlocking ring portion  778   a  interlocks with a complementary second interlocking ring portion  778   b . Flexible coupler  722  has an interlocking pattern designed to resist axial deformation (stretching) when placed in tension.  FIG. 35E  illustrates flexible coupler  722  also having interlocking ring portions  778 . In this embodiment, an axial element  784  is positioned across an interlocking feature  782  to improve the axial stiffness of flexible coupler  722  when subject to tensile loading. 
         [0177]    Although the above mentioned embodiments were discussed in connection with a tubular core member, the same properties may be applied to any other guiding member. The guiding member may incorporate any of the above mentioned properties alone, or in combination, to manipulate flexibility and column strength along the guiding member shaft. The embodiments may also be used in connection with the proximal filter or any other catheter-based system. 
         [0178]    In certain clinical scenarios, it may be desirable for the filter opening to circumferentially appose the vessel wall. This helps prevent debris from flowing past the filter. In a straight lumen, a filter can achieve good apposition with the vessel wall, thus preventing plaque or blood clots from flowing past the filter when it is deployed in a vessel. In contrast, when a filter is deployed in a curved lumen, the filter frame element can settle into a number of different rotational orientations in the lumen. In some clinical scenarios, when the filter is deployed in a curved lumen, it is possible for the filter frame element to pull away from the vessel wall particularly on the inner radius thus leading to poor apposition and blood leakage past the filter. 
         [0179]    In current settings, practitioners may seek to overcome this poor positioning by using contrast injections and fluoroscopic imaging in one or more views. The filter is then either re-sheathed and redeployed or rotated or repositioned without re-sheathing, a process that can dislodge plaque from the vessel wall or otherwise damage the vessel. Neither of these solutions is satisfactory due to the extended procedure time and the increased possibility of vessel damage due to increased device manipulation. 
         [0180]    In certain scenarios, it may be advantageous to add a tethering member to a filter assembly.  FIGS. 36A-E  illustrate tethering member  842  attached to proximal filter assembly  804 . Tethering member  842  is configured to draw proximal filter frame element  814  closer to the vessel wall in order to form a seal with the inner surface of the vessel. Proper apposition of proximal filter assembly  804  relative to the vessel wall prevents debris from flowing past proximal filter assembly  804 . This can be achieved with a flexible tethering member (e.g. monofilament polymer, braided polymer, suture, wire, etc.) or with a rigid or semi-rigid member such as nitinol, thermoplastic, stainless steel, etc. 
         [0181]    Tethering member  842  has a first end  844  and a second end  846 . In  FIG. 36A , the first end  844  of tethering member  842  is affixed to proximal sheath  802 , while the second end  846  of tethering member  842  is affixed to proximal filter assembly  804 . In some embodiments, tethering member  842  is affixed to filter frame element  814 ; while in other embodiments, tethering member  842  is affixed to proximal filter  806 .  FIGS. 36B-C  illustrate how tethering member  842  laterally deflects the frame  814  and pulls filter frame element  814  toward the vessel wall when the operator retracts proximal sheath  802 . Proximally retracting tethering member  842  allows the operator to control the deflection and angle of proximal filter frame element  814 . In other embodiments, tethering member  842  can be actuated passively rather than actively (i.e. by the operator) by forming tethering member  842  from an elastic material or spring in order to elastically pull the edge of proximal filter frame element  814  toward the vessel wall. 
         [0182]    In still other embodiments, the second end  846  of tethering member  842  may be attached to a feature disposed along proximal filter  806 . For example, in  FIG. 36E , the second end  846  of tethering member  842  is connected to a rib  848  formed on proximal filter  806 . In still other embodiments, the first end  844  of tethering member  842  may be attached to an elongate member such as a pull wire slidably disposed along the length of the catheter system to a control actuator in the control handle. This allows the operator to control the deflection of proximal filter frame element  814  independently from proximal sheath  802 . 
         [0183]    In certain embodiments, it may be preferable to attach a distal end of tethering member  842  to a single location on proximal filter assembly  804 . Alternatively, as shown in  FIG. 36D , it may be preferable to attach the distal end of tethering member  842  to two or more positions on proximal filter assembly  804 . 
         [0184]    In order to facilitate sheathing and to minimize tangling when proximal filter assembly  804  is collapsed into proximal sheath  802 , tethering member  842  may be twisted to form a coil  849 , as shown in  FIG. 37A . Twisted portion  849  retracts and stays out of the way when proximal filter assembly  804  is sheathed, and twisted portion  849  will untwist and straighten as the operator deploys proximal filter assembly  804 . The design is also helpful for controlling the slack in tethering member  842  during sheathing and unsheathing. Tethering member  842  may be formed from a heat deformable polymer and applying heat to deform the polymer into a twisted configuration. Tethering member may alternatively be formed from nitinol or any other material having suitable properties. In other embodiments, it may be preferable for tethering member  842  to form a coil ( FIG. 37B ), pre-formed to particular shapes ( FIG. 37C ), or have two or more tethering members ( FIG. 37D ). One or more tethering members may be formed into any other design that may decrease the likelihood that tethering member  842  will become tangled with other catheters or devices. 
         [0185]    Although the previously discussed tethering members have been discussed in connection with proximal filter assemblies, a tethering member may be used in connection with a distal filter, other filter devices, or any intraluminal device that may desirably be laterally displaced, tilted or otherwise manipulated into a desired orientation, such as to improve alignment including improving apposition with a vessel wall. 
         [0186]    In some clinical scenarios, it may be desirable to place a single filter in a blood vessel. Any of the above mentioned features of the dual filter embodiments may be applied to the single filter embodiments described below, including, but not limited to, filter design, sheath articulation, or guiding member flexibility or column strength. In addition, filter systems described herein can be utilized in connection with a variety of intravascular interventions. The embodiments described below will be discussed in connection with a TAVI procedure, but the filter systems may be used with other intravascular or surgical interventions such as balloon valvuloplasty, coronary artery bypass grafting, surgical valve replacement, etc. and should not be construed as limited to the TAVI procedure. 
         [0187]    In certain situations, it may be desirable to position the filter in the aorta, distal to the aortic valve but proximal to the brachiocephalic artery ostium, such that the entire arterial blood supply can be filtered. The aortic filter may also be positioned in the aorta, between the right brachiocephalic artery ostium and the left carotid artery ostium. In other scenarios, the aortic filter may be positioned between the left carotid artery ostium and the left subclavian artery ostium, while in still other clinical situations may make it preferable to position the aortic filter in the descending aorta, distal to the left subclavian artery ostium. In some cases, an aortic filter can be positioned in the aorta in combination with brachiocephalic and left carotid artery filters in order to capture all embolic debris. 
         [0188]    An aortic filter can be positioned at various locations along a catheter system. In one embodiment, the aortic filter can be positioned on a catheter separate from the TAVI or pigtail catheter and inserted through the left or right brachial artery or the right or left femoral artery. Using a separate aortic filter catheter decreases the overall diameter of the TAVI catheter and allows the operator to position the aortic filter independently from aortic valve. Further, the aortic filter will not dislodge plaque along the vessel wall when the TAVI catheter is repositioned or rotated. 
         [0189]    In another embodiment, the aortic filter can be positioned on the TAVI catheter shaft, proximal to the valve prosthesis. To decrease the size of the overall catheter system, the diameter of the TAVI catheter system proximal to the valve prosthesis may be reduced in size. This embodiment decreases the number of total devices in the operating environment, thus decreasing the likelihood that devices will get tangled. 
         [0190]    In yet another embodiment, the aortic filter may be positioned on the TAVI introducer. This embodiment enables the operator to position the aortic filter independently from the position of the TAVI catheter. The filter is also less likely to dislodge plaque along the vessel wall when the TAVI catheter is repositioned or rotated. Introducing the aortic filter on the TAVI introducer also decreases the total number of catheters into the operating environment. 
         [0191]    In still another embodiment, the aortic filter is positioned on a pigtail catheter shaft, proximal to the pigtail. Affixing the aortic filter to the pigtail catheter does not increase the overall diameter of the TAVI system or add any additional catheters into the operating environment. 
         [0192]    In one embodiment, the aortic filter is positioned on an extended pigtail introducer sheath. This embodiment enables the operator to position the aortic filter separately from the location of the pigtail without adding any additional catheters into the operating environment. Positioning the aortic filter on the pigtail introducer sheath also does not increase the overall diameter of the TAVI system. Further, the aortic filter will not dislodge plaque along the vessel while when the pigtail and/or TAVI catheter is repositioned or rotated. 
         [0193]    Various methods can be used to perform a TAVI procedure in connection with an aortic filter. In one method, the aortic filter is positioned as early as possible in the procedure at any location in the aorta previously described, and the aortic filter may be deployed using any of the above mentioned devices. The TAVI catheter may then be inserted through the filter and the TAVI implantation is performed. Afterward, the TAVI catheter and aortic filter are removed. 
         [0194]    In an alternative method, a guidewire is positioned through the aorta and the pigtail catheter is inserted into the aorta. A TAVI catheter can then be advanced to a position just proximal of where the aortic filter will be deployed. The aortic filter may be deployed at any position described above. Using any of the previously discussed embodiments, a catheter carrying an aortic filter deploys an aortic filter in the aorta. The aortic filter also forms a seal against both the TAVI catheter and the vessel wall such that debris cannot flow past the filter. After the aortic filter is deployed, the TAVI catheter is advanced to the implant location and the implant procedure is performed. When the procedure is over, the TAVI catheter is withdrawn just proximal to the filter such that the operator can retrieve the aortic filter. The aortic filter, TAVI, and pigtail catheters are then all withdrawn from the operating environment. These steps are not limited to the order in which they were disclosed. For example, the TAVI catheter may be advanced to the implant location before the aortic filter is deployed. 
         [0195]      FIG. 38A  depicts a TAVI catheter  933  that is deployed across an aortic filter assembly  904  in the aorta  999 . In some scenarios, aortic filter assembly  904  may not fully appose the TAVI catheter shaft, thus leaving room for debris to flow between the TAVI catheter  933  and the vessel wall. In these scenarios, it may be preferential to configure aortic filter assembly  904  to appose TAVI catheter  933  and prevent substantially all debris from flowing past aortic filter assembly  904  without significantly degrading filter capture performance. It may also be preferential to modify aortic filter assembly  904  in scenarios where TAVI catheter  933  passes through aortic filter assembly  904 . 
         [0196]      FIG. 38B  illustrates an aortic filter assembly  904  designed to pass over a guidewire  907  or other guiding member. Aortic filter assembly  904  may have a channel  909  on the exterior surface of aortic filter assembly  904 . Channel  909  is constructed such that a TAVI deployment catheter or other catheter may pass through channel  909 . The operator may also rotate aortic filter assembly  904  such that the TAVI catheter properly passes through channel  909 . The control handle may indicate the rotational location of channel  909  help the operator correctly orient aortic filter  904 . Alternatively, channel  909  may have at least one or two radiopaque markers to enable identification of channel  909  using fluoroscopy. 
         [0197]      FIG. 38C  depicts aortic filter assembly  904  having a leading edge  911  and a trailing edge  913 . Aortic filter assembly  904  passes over a guidewire  907  or other guiding member. Leading edge  911  overlaps trailing edge  913  to form an overlapping portion  935 . The control handle may indicate the location of overlapping portion  935  so the operator can torque aortic filter assembly  904  to position overlapping portion  935  over the TAVI or other catheter shaft. Overlapping portion  935  may have a radiopaque marker to allow the operator to monitor aortic filter placement under fluoroscopy. 
         [0198]      FIG. 38D  depicts an aortic filter assembly  904  designed to pass over a guidewire  907  or other guiding member. Aortic filter  904  has a first filter portion  915  and a second filter portion  917 , second filter portion  917  having a first edge  917   a , and a second edge  917   b . The first edge  917   a  and the second edge  917   b  of second filter portion  917  overlap first filter portion  915  to form a joint  914 . The control handle may indicate the location of joint  914  so the operator can torque aortic filter assembly  904  to position joint  914  against the shaft of the TAVI catheter. As the operator advances a catheter-based device across aortic filter  904 , second filter portion  917  caves inward such that joint  914  forms a seal around the catheter shaft. Aortic filter assembly  904  may include a radiopaque marker to allow the operator to identify joint  914  under fluoroscopy. 
         [0199]      FIGS. 39  A-C depict an aortic filter device having two or three or four or more aortic lobes or filters. Each aortic filter lobe  904   a,b,c  is joined together along a first side  919  of each aortic filter lobe  904   a,b,c . Aortic filter lobes  904   a,b,c  join together about a longitudinal axis of the aortic filter system. The aortic filter system is configured such that a TAVI catheter  933  or other catheter-based device may pass between a first aortic filter assembly  904   b  and a second aortic filter assembly  904   c . The first and second aortic filters  904   b,c  forming a seal around the TAVI catheter  933 , thus preventing debris from flowing past the aortic filter system. 
         [0200]      FIG. 40A  depicts generally conical aortic filter assembly  904  resembling an umbrella. Aortic filter  904  may pass over a guidewire  907  or other guiding member. Aortic filter assembly  904  has a plurality of self-expanding tines  923 , each tine having a proximal end and a distal end. Each tine joins together at a first end  903  of aortic filter assembly  904 . In addition, a filter portion  925  is suspended between tines  923 . Filter portion  925  may be fairly inflexible or flexible to stretch over the TAVI catheter  933  or other catheter-based device. When an operator advances TAVI catheter  933  past aortic filter assembly  904 , TAVI catheter  933  passes between a first tine  923  and a second tine  923  such that a filter portion  925  stretches over TAVI catheter  933  to form a seal between filter portion  925  and TAVI catheter  933 . 
         [0201]    Alternatively,  FIG. 40B  depicts an aortic filter assembly  904  resembling a flower. In one embodiment, aortic filter assembly  904  has two or more petals  943  arranged in a circular array that allow TAVI catheter  933  or other catheter-based device to pass between petals  943 . Petals  943  may overlap one another to create a seal between adjacent petals  943 . Petals  943  also create a seal around TAVI catheter  933  as the catheter passes between petals  943 . The shape of each petal  943  may include an arch to better accommodate the circular shape of the aorta. Each petal  943  may have a length between two to six centimeters. Although in some embodiments, the length may be less than in two centimeters; while in still other embodiments, the length may be greater than six centimeters. In one embodiment, the individual petals are comprised of a frame  944  that is covered with a filter element  945 . The frame  944  may be constructed of a shape memory material such as Nitinol, or other material such as stainless steel, cobalt supper alloy (MP35N for example) that has suitable material properties. The filter element  945  may be constructed of a polyurethane sheet that has been pierced or laser drilled with holes of a suitable size. Other polymers may also be used to form the filter element, in the form of a perforated sheet or woven or braided membranes. Thin membranes or woven filament filter elements may alternatively comprise metal or metal alloys, such as nitinol, stainless steel, etc. 
         [0202]    Any of the aortic filter assemblies described above may also include frame element  914  formed from a material suitable to form a tight seal between aortic filter assembly  904  and TAVI catheter  933  or other catheter-based device as the filters fill under systolic blood pressure. 
         [0203]      FIGS. 41A-B  depicts an aortic filter assembly  904  having an inflatable portion  927  defining a distal opening  912  of aortic filter  906 . In some embodiments, inflatable portion  927  forms a continuous ring. Inflatable portion  927  forms a seal against the vessel wall such that debris cannot pass between aortic filter assembly  904  and the vessel wall. Inflatable portion  927  may also form a seal against a TAVI catheter passed between aortic filter assembly  904  and the vessel wall. 
         [0204]    As depicted in  FIG. 41A , inflatable portion  927  and filter element  906  may form a channel  929  on an exterior surface of aortic filter assembly  904  through which a catheter-based device may pass. Channel  929  forms a seal against the catheter such that debris may not flow between the aortic filter assembly  904  and the catheter. 
         [0205]      FIG. 41B  illustrates an inflatable portion  927  having a gap  931  through which a catheter-based device may pass. Filter element  906  may also form a channel on the exterior surface of the aortic filter assembly  904  through which the catheter may pass. 
         [0206]    In an embodiment which includes an inflatable annulus or other support, the inflatable support is placed in fluid communication with a source of inflation media by way of an inflation lumen extending throughout the longitudinal length of the catheter shaft. Once the filter has been positioned at a desired site, the annulus can be inflated by injection of any of a variety of inflation media, such as saline. The inflation media may thereafter be aspirated from the filter support, to enable collapse and withdraw of the filter. The inflation media may include a radiopaque dye to help the operator locate the inflatable annulus under fluoroscopy. 
         [0207]    Although the filter systems described above were discussed in connection with a single filter system, the filter designs may also be used in connection with a dual filter system. 
         [0208]      FIG. 42  depicts one embodiment of a filter assembly that may be used in connection with any filter-based device, including the dual filter and single filter systems described above. Filter assembly  926  may comprise a filter membrane  936 , a filter frame element  928 , and at least one radiopaque marker. Filter membrane may  936  may be constructed from a polyurethane film or any other polymer or material exhibiting suitable properties. In some embodiments, a laser or other mechanism may be used to create at least one filter hole in the filter membrane through which blood may flow. The at least one filter hole is small enough such that a blood clot or piece of embolic debris exceeding a predetermined dimension cannot pass through. The filter membrane may be formed into a conical or other shape by heat sealing a first edge of the filter membrane to a second edge of the filter membrane, although other methods may be used to join a first edge of the filter membrane to a second edge of the filter membrane. In several embodiments, filter assembly  926  may also include flexible coupler  922 . 
         [0209]    A frame element  928  may be shaped from a Nitinol wire, but, as discussed in earlier paragraphs, the frame element may be shaped from any other suitable material or textured to exhibit desired properties. In some embodiments, at least one radiopaque marker is incorporated into filter assembly  926 . In one embodiment, a 90/10 platinum/iridium coil marker is positioned around frame element  928  and bonded with an adhesive. Alternatively, other types of radiopaque markers may be integrated into or affixed to frame element  928 . Other methods of affixing the radiopaque marker may also be used. 
         [0210]    In several embodiments, filter assembly  926  includes a strut tubing  924 . Strut tubing  924  may be constructed from PET heat shrink tube, polyimide tube, or any other material exhibiting suitable properties. In one embodiment, strut tubing  924  is affixed to one or more legs of frame element  928  with an adhesive, although other means for affixation may also be used. Additional mechanisms may also be used to reinforce the adhesive or other means of affixation. Alternatively, strut tube  924  may be slipped over one or more portions of the frame element  928  and may additionally be bonded in place. 
         [0211]    In some embodiments, filter membrane  936  may be attached to frame element  928  by heat-sealing a first portion of filter membrane  936  to a second portion of filter membrane  936  to form a sleeve through which frame element  928  may pass. An adhesive may be used to reinforce the bond between the frame element and the filter membrane. Other mechanisms may also be used to affix frame element  928  to filter membrane  936 . Additional mechanisms may also be used to reinforce the adhesive or other affixation mechanism. 
         [0212]    In some embodiments, frame element  928  is attached to a filter shaft  920  via a stainless steel crimp  998 , although other mechanisms may be used to affix frame element  928  to a filter shaft  920 . Additional affixation methods may also be used to reinforce the stainless steel crimp  998  or other mechanism. 
         [0213]    In several embodiments, a cannulated distal tip  940  having an atraumatic distal end with a guidewire exit port is joined to the distal end of filter shaft  920 . 
         [0214]      FIG. 43  illustrates a proximal portion of an exemplary filter system. The portion shown in  FIG. 43  is generally the portion of the system that remains external to the subject and is used to control the delivery and actuation of system components. Proximal sheath  1010  is fixedly coupled to proximal sheath hub  1012 , which when advanced distally will sheath the proximal filter (as described herein), and when retracted proximally will allow the proximal filter to expand. The actuation, or control, portion also includes handle  1016 , which is secured to proximal shaft  1014 . When handle  1016  is maintained axially in position, the position of the proximal filter is axially maintained. The actuation portion also includes distal sheath actuator  1022 , which includes handle  1023  and deflection control  1020 . Distal sheath actuator  1022  is secured to distal shaft  1018 . As described herein, the distal articulating sheath is adapted to have three independent degrees of motion relative to the proximal sheath and proximal filter: rotation, axially translation (i.e., proximal and distal), and deflection, and distal sheath actuator  1022  is adapted to move distal sheath  1018  in the three degrees of motion. Distal sheath  1018  is rotated in the direction shown in  FIG. 43  by rotating distal sheath actuator  1022 . Axial translation of distal sheath occurs by advancing actuator  1022  distally (pushing) or by retracting actuator  1022  proximally (pulling). Distal sheath  218  is deflected by axial movement of deflection control  1020 . Movement of deflection control  1020  actuates the pull wire(s) within distal sheath  1018  to control the bending of distal sheath  1018 . Also shown is guiding member  1024 , which is secured to the distal filter and is axially movable relative to the distal sheath to deploy and collapse the distal filter as described herein. The control portion also includes hemostasis valves  1026 , which in this embodiment are rotating. 
         [0215]      FIG. 44  illustrates an exemplary 2-piece handle design that can be used with any of the filter systems described herein. This 2-piece handle design includes distal sheath actuator  1046 , which includes handle section  1048  and deflection control knob  1050 . Deflection control knob  1050  of distal sheath actuator  1046  is secured to distal shaft  1054 . Axial movement of distal sheath actuator  1046  will translate distal shaft  1054  either distally or proximally relative to the proximal filter and proximal sheath. A pull wire (not shown in  FIG. 44 ) is secured to handle section  1048  and to the distal articulatable sheath (not shown in  FIG. 44 ). Axial movement of deflection control knob  1050  applies tension, or relieves tension depending on the direction of axial movement of deflection control knob  1050 , to control the deflection of the distal articulatable sheath relative to the proximal filter and proximal sheath  1044 , which has been described herein. Rotation of distal sheath actuator  1046  will rotate the distal sheath relative to the proximal filter and proximal sheath. The handle also includes housing  1040 , in which proximal sheath hub  1042  is disposed. Proximal sheath hub  1042  is secured to proximal sheath  1044  and is adapted to be moved axially to control the axial movement of proximal sheath  1044 . 
         [0216]      FIG. 45  illustrates another exemplary embodiment of a handle that can be used with any of the filter systems described herein. In this alternate embodiment the handle is of a 3-piece design. This 3-piece handle design comprises a first proximal piece which includes distal sheath actuator  1061 , which includes handle section  1063  and deflection control knob  1065 . Deflection control knob  1065  of distal sheath actuator  1061  is secured to distal shaft  1067 . Axial movement of distal sheath actuator  1061  will translate distal shaft  1067  either distally or proximally relative to the proximal filter and proximal sheath. A pull wire (not shown in  FIG. 45 ) is secured to handle section  1063  and to the distal articulatable sheath (not shown in  FIG. 45 ). Axial movement of deflection control knob  1065  applies tension, or relieves tension depending on the direction of axial movement of deflection control knob  1065 , to control the deflection of the distal articulatable sheath relative to the proximal filter and proximal sheath  1069 . Rotation of distal sheath actuator  1061  will rotate the distal sheath relative to the proximal filter and proximal sheath  1069 . The handle design further includes a second piece comprising central section  1060  which is secured to proximal shaft  1071 . A third distal piece of this handle design includes housing  1062 . Housing  1062  is secured to proximal sheath  1069 . Housing  1062  is adapted to move axially with respect to central section  1060 . With central section  1060  held fixed in position, axial movement of housing  1062  translates to axial movement of proximal sheath  1069  relative to proximal shaft  1071 . In this manner, proximal filter  1073  is either released from the confines of proximal sheath  1069  into expandable engagement within the vessel or, depending on direction of movement of housing  1062 , is collapsed back into proximal sheath  1069 . 
         [0217]      FIG. 46  depicts another embodiment of a control handle. The control handle has a proximal filter control  1100  and a distal filter control  1102 . To deploy the device, the distal shaft of the catheter is fed over a guidewire and manipulated into position in the patient&#39;s anatomy. To deploy the proximal filter, the proximal filter sheath control  1120  is withdrawn proximally while holding the proximal filter handle  1118  stationary. The proximal filter sheath control  1120  is a sliding control; however, any other control such as a rotating knob, a pivoting lever, etc. may be used to withdraw the sheath. 
         [0218]    When the proximal filter is properly deployed, the distal filter contained in the distal sheath is advanced distally and positioned in the target location by advancing the distal filter control  1102  while holding the proximal filter control  1100  stationary. During this positioning process, the distal filter control  1102  can be advanced, retracted or rotated relative to the proximal filter control  1100 , and as needed, the deflection of the distal sheath may be controlled by actuating the distal sheath deflection control  1112  relative to the distal filter sheath handle  1110 . The distal sheath deflection control  1112  is a pivoting control; however, any other control such as a rotating knob, a sliding knob, etc. may be used to deflect the sheath. Once the sheath containing the collapsed distal filter is positioned correctly, the position of the distal filter control  1102  is locked relative to the proximal filter control  1100  by tightening the proximal handle hemostasis valve  1116 . Next, the distal filter may be deployed by advancing the guiding member  1108  by grasping the distal filter Luer fitting  1104  until the filter is deployed. The position and orientation of the distal filter may be adjusted by advancing, retracting or rotating the distal filter Luer fitting  1104  relative to the distal filter sheath handle  1110 . Finally, the position of the distal filter may be fixed relative to the distal filter sheath handle  1110  by tightening the distal handle hemostasis valve  1106 . To remove the device upon completion of the procedure, the aforementioned procedure is reversed. 
         [0219]      FIGS. 47A through 47I  illustrate cross-sections through the control handle illustrated in  FIG. 46 , taken along the section lines indicated in  FIG. 46 . 
         [0220]      FIGS. 47A-B  depict cross-sectional areas of proximal filter control  1100 . The distal shaft  1108  is disposed through a lumen defined by the articulating distal sheath  1114 . In these figures, the articulating distal sheath  1114  is disposed through a lumen defined by the proximal filter shaft  1124 , and the proximal filter shaft is disposed through a lumen defined by the front handle  1118 . 
         [0221]      FIG. 47C  depicts a cross-sectional area of a distal section of distal filter control  1102 . In  FIG. 47C , articulating distal sheath  1114  is disposed through a lumen defined by the rear handle  1110  as shown in  FIG. 47C .  FIG. 47D  shows a cross-sectional view proximal to the cross-section shown in  FIG. 47C . In  FIG. 47D , guiding member  1108  is disposed through a lumen defined by the rear handle  1110 . Guiding member  1108  defines a lumen  1128  through which a guidewire may pass.  FIG. 47E  shows a cross-sectional view proximal to the cross-section shown in  FIG. 47D . The guiding member  1108  is coaxial with a stainless steel hypotube  1130 . Hypotube  1130  reinforces the guiding member  1108 . 
         [0222]      FIG. 47F  depicts a longitudinal cross-section of proximal filter control  1100 . At the distal end of proximal filter control  1100 , there is a nose piece  1132  holding the front handle  1118  together. Proximal to nose piece  1132  there is a proximal filter sheath control  1120  to actuate the proximal filter sheath and deploy the proximal filter. The proximal filter sheath control is associated with a locking mechanism  1126  to prevent unintentional filter deployment and to actuate a sealing mechanism to prevent blood leakage. The locking mechanism  1126  comprises a locking element  1134 , an elastomeric seal  1138 , a spring  1136 , and a nut  1140  for holding locking mechanism  1126  together. In certain embodiments, squeezing the proximal filter sheath control  1120  will release the locking element  1134  between the proximal sheath  1122  and proximal filter shaft  1124 . 
         [0223]      FIGS. 47G-H  depicts a longitudinal cross section of distal filter control  1102 . At a distal section of the distal filter control  1102 , there is a mechanism to actuate articulating distal sheath  1114 . The actuation mechanism includes an axially movable deflection lever  1112  pivoting on distal sheath pivot  1146 . The distal sheath deflection lever  1112  is connected to the distal sheath pull wire at attachment point  1150 . The pull wire is disposed through channel  1148 . Proximal to rear handle  1110  there is a distal handle hemostasis valve  1106 . Distal handle hemostasis valve  1106  comprises elastomeric seal  1152  and HV nut  1154 . Distal filter shaft  1108  and hypotube  1130  extend proximally from distal filter control  1102  and terminate at distal filter luer lock fitting  1104 . 
         [0224]    An alternative control handle uses a rotating screw drive mechanism to deflect a distal end of a distal articulating sheath is shown in  FIG. 48 . In certain clinical scenarios, it may be desirable to include a mechanism that prevents the articulating sheath from unintentionally deflecting when the operator releases the handle. The mechanism incorporates a lead screw  1214  which is inherently self-locking in that tip deflection will be locked wherever the handle control is released by the operator. A rotating screw drive mechanism provides an easy to manufacture design to control the pivot of the articulating sheath. The rate of deflection of the tip is controlled by the pitch of the screw threads  1218 , thus rapid deflection of the tip, which can lead to unintentional vessel damage, can be prevented. 
         [0225]    While specific embodiments have been described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from that which is disclosed. It should be understood that various alternatives to the embodiments described herein may be employed in practicing the disclosure.
Single filter and multi-filter endolumenal methods and systems for filtering fluids within the body. In some embodiments a blood filtering system captures and removes particulates dislodged or generated during a surgical procedure and circulating in a patient&#39;s vasculature. In some embodiments a filter system protects the cerebral vasculature during a cardiac valve repair or replacement procedure.