Patent Publication Number: US-2022218459-A1

Title: Self-cleaning aortic blood filter

Description:
RELATED APPLICATIONS 
     This patent application claims the benefit of U.S. Provisional Application No. 62/849,241, filed May 17, 2019, the disclosure of which is incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure is directed generally to implantable blood filter devices and more specifically to filter devices to protect the brain and other organs from emboli. 
     BACKGROUND OF THE DISCLOSURE 
     Various conventional devices exist to contain or control the flow of thrombic material and atheroma debris. Examples of such devices include U.S. Pat. Nos. 6,712,834 and 6,866,680 to Yassour, et al., and U.S. Pat. No. 7,670,356 to Mazzocchi et al., which disclose blood filter devices designed to capture the debris material. A concern with capture filters is that they can foul to the extent that blockage of blood flow develops, with obvious consequences. Accordingly, these devices are typically unsuitable for long term or permanent implantation. 
     In another approach, U.S. Pat. No. 6,258,120 to McKenzie et al., U.S. Pat. No. 8,430,904 to Belson, U.S. Pat. No. 8,062,324 to Shimon et al., and U.S. Patent Application Publication No. 2009/0254172 to Grewe are directed to aortic diverters that divert emboli away from arteries. Diverter-type devices are limited to certain artery junction structures where flow diversion is a suitable substitute for filtering, and, in many instances, do not provide a positive barrier to emboli, either by design or because of the way they are mounted within the aorta. Furthermore, these devices can foul with debris build up over time, leaving no recourse for remedying the fouling, and so are not suitable for long term or permanent implantation. Also, diverter devices that are based on anchoring in the aorta require large diameter catheters for delivery. Other diverter-type devices include U.S. Pat. No. 8,460,335 to Carpenter, are held in place by the attendant deployment means, and thus suitable only for temporary service. 
     More recently, “self-cleaning” blood filters have been introduced, such as International Application No. WO 2015/173646 to Verin, et al., owned by the owner of the present application, and contents of which are hereby incorporated by reference herein in its entirety. Such self-cleaning blood filters can operate to provide a positive barrier that prevents emboli from entering the arteries from the aortic arch while enabling blood to flow through the structure, effectively keeping the structures clear of debris. 
     While the work of Verin et al. provides sound concepts for both temporary and permanent blood filters, putting these concepts into practice has raised special challenges. Self-cleaning blood filters that facilitate fabrication and deployment aspects would be welcomed. 
     SUMMARY OF THE DISCLOSURE 
     Various embodiments of the disclosure disclose a blood filter having a support structure and a filter structure. These structures may have different porosities. For example, the support structure, which serves as an anchor for the blood filter may define a larger porosity, the larger pores of which promotes ample tissue growth therethrough that secures the device in place for permanent implant applications. The filter structure may define a smaller porosity, the smaller pores of which prevent emboli from passing therethrough. For fabrication and delivery purposes, the support and filter structures may be made separately and assembled. In some embodiments, the support structure presents a coarser mesh. In some embodiments, the support structure is an expanded metal structure, akin to a stent. In some embodiments, the filter structure presents a finer braided mesh that is overlaid on or otherwise attached to the support structure. In some embodiments, a polymer film is selectively applied to the filter structure and cooperates with the filter structure to provide a more uniform porosity over the filter structure. 
     Filtration of the blood includes deflection of emboli by the filter structure back into the aortic arch, as well as capture of emboli within the pores of the filter structure. In some embodiments, the filter structure is suspended away from the artery inlets. As such, the filter structure may be subject to cross flows during the cardiac cycle that may dislodge emboli from the filter structure, with the emboli being returned to the aortic arch and away from the inlets of the arteries. Accordingly, accumulation of emboli the filter structure is thereby reduced, such that the filter assembly is characterized as being “self-cleaning.” 
     Various embodiments of the filtering assemblies may be utilized as a temporary implant or a permanent implant. The elastic properties of the filtering assemblies enable minimally invasive delivery through blood vessels, and further enable collapsing the device for retrieval of temporary implantations. 
     Structurally, various embodiments of the disclosure disclose a filter assembly for filtering blood entering an artery from an aortic arch, comprising a filter structure and a support structure that cooperate to define an anchor leg and a filter leg. The anchor leg defines a distal opening and extends along a first central axis. The first central axis extends in an inferior direction from the distal opening toward an elbow portion of the filter leg, the filter leg being proximal to the anchor leg and defining and extending along a second central axis. The filter leg includes the elbow portion and an extension portion, the elbow portion extending from the anchor leg and separating the anchor leg from the extension portion. The support structure extends from the elbow portion into the extension portion. 
     In some embodiments, the filter structure is configured to slide on the support structure. The support structure may include at least one rail that extends into the extension portion, the filter structure being slidable on the rail. In some embodiments, the at least one rail may form a loop proximal to the filter structure. The loop may be configured as a snare portion for retrievability of the filter assembly, and may include a crimp attached to a proximal end of the loop, which may include a radiopaque material. 
     In some embodiments, the filter assembly defines an assembled length that extends from the first central axis at a distal opening of the anchor leg to an inside surface of the loop at the second central axis when the filter assembly is in a pre-implant configuration. The loop defines an inside length along the second central axis that extends from a proximal end of the filter structure to the inside surface of the loop when the filter assembly is in a pre-implant configuration. In some embodiments, a ratio of the assembled length to the inside length is in a range of 5 to 1 inclusive. 
     In some embodiments of the disclosure, the anchor leg includes a tail portion that extends distally beyond the assembled length, the tail portion being configured as a snare portion for retrievability of the filter assembly. The snare portion may include a hook structure. The tail portion may include a crimp attached to a distal end of the tail portion, the crimp including a radiopaque material. 
     In some embodiments of the disclosure, the filter structure and the support structure are interlaced. The filter structure may be one of a braided structure and a woven structure. In some embodiments, the filter structure and the support structure are tightly interlaced at the elbow portion to secure the filter structure to the support structure, while the filter structure and the support structure are loosely interlaced at the extension portion to enable the filter structure to slide over the support structure. 
     In some embodiments, the filter structure may include opposed lateral edges that are lateral to the second central axis, each of the opposed lateral edges including a hem structure that enables the filter structure to slide over the support structure. The extension portion of the filter structure defines an arcuate cross-section orthogonal to the second central axis that partially surrounds the second central axis, the arcuate cross section extending away from the central axis in the inferior direction. The arcuate cross-section may define one of a U-shape and a V-shape. 
     In some embodiments, a distal end of the filter structure is fastened to the anchor leg. 
     In some embodiments, a distal end of the filter structure defines closed neck. The distal end of the filter structure may be fastened to the anchor leg with crimps, and the crimps may include a radiopaque material suitable for visualization with an imaging system. In some embodiments, the closed neck wraps around anchor leg. In other embodiments, the distal end of the filter structure abuts against the anchor leg to define a diameter that is substantially the same as a diameter of the anchor leg. In some embodiments, the anchor support structure defines a first area porosity that is within a range of 60% to 98% inclusive. A mesh used to fabricate the filter structure may define a second area porosity that is within a range of 50% to 98% inclusive. A nominal pore size of the support structure may be greater than a nominal pore size of the filter leg. In some embodiments, the nominal pore size of the support structure is within a range of 0.5 to 8 millimeters inclusive; in some embodiments, within a range of 0.5 to 5 millimeters inclusive; in some embodiments, within a range of 0.5 to 3 millimeters inclusive. In some embodiments, the nominal pore size of the filter mesh of filter structure is within a range of 0.2 to 0.8 millimeter inclusive. In some embodiments, a ratio of the nominal pore size of the support structure to the nominal size of the filter mesh of filter structure is within a range of 2.5 to 55 inclusive; in some embodiments, within a range of 2.5 to 40 inclusive; in some embodiments, within a range of 2.5 to 25 inclusive. 
     When the filter assembly is in an implant configuration, a lateral projection of the first central axis and the second lateral axis may define a minimum projected angle, the minimum projected angle being within a range of 40 degrees to 80 degrees inclusive. In some embodiments, the minimum projected angle is within a range of 50 degrees to 70 degrees inclusive. 
     In various embodiments of the disclosure, a filter assembly for filtering blood entering an artery from an aortic arch is disclosed, comprising an anchor leg and a filter leg that extends from the anchor leg, the filter leg including an elbow portion, the anchor leg defining a first central axis that extends in a first direction from the anchor leg away from the elbow portion, and a support structure extending from the anchor leg along the filter leg, the support structure including a pair of support rails that extend beyond the elbow portion along the filter leg. A first support rail of the pair of support rails may define a first shape beyond the elbow portion, and a second support rail of the pair of support rails may define a second shape beyond the elbow portion. In some embodiments, the second shape extends further in the first direction than the first shape. 
     The first shape and the second shape may each arc toward a second direction, the second direction being opposite the first direction. The first shape and the second shape may each arc toward a first lateral direction, the first lateral direction being perpendicular to the first direction. In some embodiments, the anchor leg is configured to anchor the filter assembly in a brachiocephalic artery. The first shape and the second shape may each configured for continuous contact along a roof of an aortic arch, the continuous contact of the first shape being anterior to the continuous contact of the second shape In some embodiments, a filter structure is coupled to the pair of rails, the filter structure including a web portion that extends between the pair of rails. The filter structure may define an arcuate cross-section orthogonal to the second central axis, the arcuate cross section extending in a second direction that is opposite the first direction. In some embodiments, the cross-section defines one of a U-shape and a V-shape. 
     In various embodiments of the disclosure, filter assembly for filtering blood entering an artery from an aortic arch is disclosed, comprising a filter structure and a support structure that cooperate to define an anchor leg and a filter leg, the anchor leg defining a distal opening and extending along a first central axis, the first central axis extending in an inferior direction from the distal opening toward an elbow portion of the filter leg, the filter leg being proximal to the anchor leg and defining and extending along a second central axis, the filter leg including the elbow portion and an extension portion, the elbow portion extending from the anchor leg and separating the anchor leg from the extension portion, A perforated polymer coating may cover an outer contour of the elbow portion, and defines a plurality of perforations that pass through the perforated polymer coating. In some embodiments, the perforations of the plurality are sized within a range of 0.2 to 0.8 millimeter diameter inclusive. In some embodiments, the perforated polymer coating defines an area porosity that is within a range of 60% to 98% inclusive. 
     In various embodiments of the disclosure, a method of making this filter assembly comprises: coating the outer contour of the elbow portion with a polymer; and forming the plurality of perforations through the polymer. The polymer may be applied as a liquid and allowed to harden before the step of forming. The plurality of perforations may be formed by a laser cutting process. In some embodiments, the filter assembly is formed to shape over a mandrel and heat set to form the elbow portion prior to the step of coating. 
     In various embodiments of the disclosure, a method of collapsing a filter assembly for vascular delivery is disclosed, comprising: bending a filter assembly from an implant configuration to a pre-implant configuration; collapsing the filter assembly toward a central axis of the pre-implant configuration; and sliding at least a portion of a filter structure of the filter assembly along a support structure of the filter assembly during the step of collapsing to elongate the filter structure along the central axis of the pre-implant configuration. The filter structure may slide along a rail of the support structure during the step of sliding. The filter structure may include a hem that slides along the rail of the support structure during the step of sliding. The 
     filter assembly in the steps of bending and collapsing may be made of super-elastic material, such as a nickel titanium alloy and a cobalt-chromium-nickel-molybdenum-iron alloy. 
     In various embodiments of the disclosure, a method of forming rails on a support structure of a filter assembly is disclosed, comprising: forming a plurality of pre-expansion pores at a first end portion of a tube to define a pre-expansion anchor portion; cutting at least one segment proximal to the pre-expansion anchor portion to form at least one rail extending proximal to the pre-expansion anchor portion; and expanding the tube to define an expanded anchor portion. In some embodiments, a ratio of a length that the rail extends from the expanded anchor portion to a length of the expanded anchor portion is in range of 0.2 to 1.5 inclusive. A taper may be formed at a distal end of the pre-expansion anchor portion. In some embodiments, the method includes coupling a filter structure to the at least one rail portion, the filter structure including a proximal end, and closing the at least one rail portion to form a loop with the proximal end of the filter portion to support the filter structure. During the step of coupling, the filter structure may include capturing the at least one rail portion within a hem structure of the filter structure. In some embodiments, the at least one rail portion in the step of cutting at least one segment is two rail portions, wherein the step of closing may include joining proximal ends of the two rail portions together. The tube in the step of forming the plurality of pre-expansion pores may be a circular tube. In some embodiments, the steps of cutting are performed with a laser. 
     In various embodiments of the disclosure, a method of forming a filter assembly for a blood filter is disclosed, comprising: forming a tubular sleeve structure defining a substantially linear central axis, the tubular sleeve structure defining a wall porosity; partially severing the tubular sleeve structure to form severed edges that are bridged by a hinge portion, the hinge portion extending along one side of the tubular sleeve structure; rolling or folding the severed edges back along an inside of the tubular sleeve structure to define opposed mitered edges, the opposed mitered edges defining a miter angle when the tubular sleeve defines the substantially linear central axis; and closing the miter angle about the hinge portion to define an elbow shape. In some embodiments, the tubular sleeve is mounted on a mandrel to close the miter angle, and may be heat setting the tubular sleeve on the mandrel. The method may include the step of sliding the sleeve structure over a support structure to close the miter angle. 
     In various embodiments of the disclosure, a filter assembly for filtering blood flowing into an artery is disclosed, comprising a tubular support structure that defines a first open end and a second open end that is opposed to the first open end, the tubular support structure having a tubular wall that defines a wall area porosity, the tubular support structure being curved to define a first leg portion and a second leg portion, the second leg portion including an elbow portion that extends from the first leg portion, the first leg portion defining the first open end and a first central axis, the second leg portion defining the second open end and a second central axis, the first central axis and the second central axis defining a minimum projected angle of the first central axis and the second central axis that is less than 180 degrees. A filter structure may define a filter area porosity and may be coupled to the second leg portion of the tubular support structure, In some embodiments, the filter assembly defines an inside portion that faces inward and an opposed outside portion that faces outward. The filter structure and the tubular support structure may define a combined area porosity that is less than the wall area porosity. In some embodiments, the filter structure is arranged so that at least part of the outside portion of the filter assembly defines the combined area porosity at the elbow portion and the second leg portion, and at least part of the inside portion defines the wall area porosity at the second leg portion. In some embodiments, the minimum projected angle is an obtuse angle; in others, the minimum projected angle is an acute angle. In some embodiments, the minimum projected angle is in a range of 40 degrees to 80 degrees inclusive; in some embodiments, the minimum projected angle is in a range of 50 degrees to 70 degrees inclusive. 
     In some embodiments, the filter structure is disposed on an interior of the tubular support structure; in others, the filter structure is disposed on an exterior of the tubular support structure. The filter structure may be attached to the tubular support structure with at least one of a threaded wire, a plurality of stitches, and a plurality of point-wise tack welds. In some embodiments, the tubular support structure includes one of a braided structure and a woven structure, the tubular support structure including a plurality of pores defined therethrough. 
     The tubular support structure may be of a coarse wire mesh, wherein the coarse wire mesh includes wire having a diameter in a range of 100 micrometers to 300 micrometers inclusive and defining pore sizes in a range of three millimeters to five millimeters inclusive, the coarse wire mesh being one of a braided structure and a woven structure. The coarse wire mesh may be formed from a single continuous wire. In some embodiments, wire is composed of a material that includes one of a cobalt-chromium-nickel-molybdenum-iron alloy and a nickel-titanium alloy. The material may be one of NITINOL and an alloy specified by ASTM F 1058 or ISO 5832-7. 
     In some embodiments, the filter structure is a two-dimensional structure that conforms to a shape of the tubular support structure when coupled to the tubular support structure. The filter structure may be one of a braided structure and a woven structure that is integrated with the elbow portion and the second leg portion. In some embodiments, the filter structure is a fine wire mesh, wherein the fine wire mesh is braided or woven with wire having a diameter in a range of 30 micrometers to 100 micrometers inclusive. The fine wire mesh may define a plurality of non-circular pores, each having a nominal major dimension in a range of 200 micrometers to 800 micrometers inclusive and may be woven or braided from a single wire. 
     In some embodiments, the wire is of a super elastic material, such as NITINOL. 
     In various embodiments of the disclosure, a method of manufacturing a filter assembly is disclosed, comprising: forming the tubular support structure about a substantially linear axis; fitting the tubular support structure over a curved mandrel to define the minimum projected angle; heat treating the tubular support structure on the mandrel; and coupling the filter structure to the elbow portion and the leg portion. The filter structure may be a tubular sleeve structure defining a plurality of apertures formed on a first side thereof, the plurality of apertures being arranged so that the inside portion of the filter assembly defines the wall area porosity of the tubular support structure through the plurality of apertures. In some embodiments, one or more of the plurality of apertures is arranged on the first side for substantial alignment with ostia of arteries that branch from an aortic arch when the filter assembly is implanted in the aortic arch. 
     In various embodiments of the disclosure, a method of manufacturing a filter assembly, includes: forming the tubular sleeve structure of the filter structure about a substantially linear axis; fitting the tubular sleeve structure over a mandrel, the mandrel including a plurality of apertures on one side that pass through a wall of the mandrel into a hollow defined by the mandrel; heat treating the tubular support structure on the mandrel; forming a plurality apertures in the tubular sleeve structure that pass through the plurality of apertures of the mandrel; and coupling the filter structure to the elbow portion and the leg portion of the tubular support structure. The step of coupling the filter structure to the elbow portion and the second leg portion of the tubular support structure may include arranging the filter structure on an exterior of the tubular support structure, and the step of forming the tubular support structure may include one of a weaving or a braiding process. 
     In various embodiments of the disclosure, a filter assembly is disclosed, comprising a tubular support structure that defines a first open end and a second open end that is opposed to the first open end, the tubular support structure having a tubular wall that defines a wall area porosity, the tubular support structure being curved to define a first leg portion and a second leg portion separated by an elbow portion, the first leg portion defining the first open end and a first central axis, the second leg portion defining the second open end and a second central axis, the first central axis and the second central axis intersecting to define an apex angle that is less than 180 degrees, the apex angle defining a central plane of the tubular support structure. A filter structure may define a filter area porosity and being coupled to the elbow portion and the second leg portion of the tubular support structure. In some embodiments: the filter assembly defines an inside portion that faces toward the apex angle and an opposed outside portion that faces away from the apex angle; the filter structure and the tubular support structure define a combined area porosity that is less than the wall area porosity; and the filter structure is arranged so that at least part of the outside portion of the filter assembly defines the combined area porosity at the elbow portion and the second leg portion, and at least part of the inside portion defines the wall area porosity at the second leg portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a frontal cutaway view of a human heart with a filter device implanted in an embodiment of the disclosure; 
         FIG. 2  is an exploded perspective view of a filter assembly having a support structure and a filter structure according to an embodiment of the disclosure; 
         FIG. 3  is an assembled perspective view of the filter device of  FIG. 2  according to an embodiment of the disclosure; 
         FIG. 4  is a partial plan view of a porous construction for the filter structure of  FIGS. 2 and 3  according to an embodiment of the disclosure; 
         FIG. 5  is a perspective view of a support structure according to an embodiment of the disclosure; 
         FIG. 6  is a plan view of a flat filter portion mounted on a loom frame according to an embodiment of the disclosure; 
         FIG. 7  is a schematic view of a filter mesh according to an embodiment of the disclosure; 
         FIG. 8  is an enlarged, partial view of the schematic view of the filter mesh of  FIG. 7  according to an embodiment of the disclosure; 
         FIGS. 9 and 10  are perspective views of a filter structure and a corresponding mandrel for formation thereof according to an embodiment of the disclosure; 
         FIG. 11  is a tubular filter structure prior to shaping according to an embodiment of the disclosure; 
         FIG. 12  is the tubular filter structure of  FIG. 11  after shaping with a perforated polymer overcoat according to an embodiment of the disclosure; 
         FIG. 13  is a partial, enlarged sectional view of an elbow portion of the tubular filter structure of claim  12  prior to overcoating according to an embodiment of the disclosure; 
         FIG. 14  is the sectional view of  FIG. 13  after application of a liquid polymer coating according to an embodiment of the disclosure; 
         FIG. 15  is the sectional view of  FIG. 14  after perforation of the polymer overcoat according to an embodiment of the disclosure; 
         FIG. 16  is a perspective view of a mitered tubular filter structure prior to shaping according to an embodiment of the disclosure; 
         FIG. 17  is a perspective view of the mitered tubular filter structure of  FIG. 16  after shaping according to an embodiment of the disclosure; 
         FIG. 18  is a perspective view of a filter assembly with a filter structure interlaced with a support structure in a pre-implant configuration according to an embodiment of the disclosure; 
         FIG. 19  is a perspective view of the filter assembly of  FIG. 18  in an implant configuration according to an embodiment of the disclosure; 
         FIG. 20  is a perspective view of a filter assembly in an implant configuration and having a filter structure with hemmed lateral edges for sliding on a support structure according to an embodiment of the disclosure; 
         FIG. 21  is a planar projection of a pre-expanded tube of the support structure of the filter assembly of  FIG. 20  according to an embodiment of the disclosure; 
         FIG. 22  is an enlarged, partial view of the planar projection of  FIG. 21  according to an embodiment of the disclosure; 
         FIG. 23  is a planar projection of the tube of  FIG. 21  in an expanded configuration according to an embodiment of the disclosure; 
         FIG. 24  is an enlarged, partial view of the support structure of  FIG. 23  according to an embodiment of the disclosure; 
         FIG. 25  is a partial perspective view the support structure of the filter assembly of  FIG. 20  according to an embodiment of the disclosure; 
         FIG. 26  is a partial elevational view of the support structure of  FIG. 25  according to an embodiment of the disclosure; 
         FIGS. 27 through 29  are perspective views of a filter structure of the filter assembly of  FIG. 20  according to an embodiment of the disclosure; 
         FIG. 30  is a cutaway perspective view of a filter assembly implanted in an aortic arch according to an embodiment of the disclosure; and 
         FIGS. 31 through 33  is a three-way orthographic projection of a shape of the filter assembly of  FIG. 30  according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an implantable filter device or assembly  30  is depicted in an implanted configuration  22  in an artery  26  of an aortic arch  31  of a heart. The filter assembly  30  is depicted as being implanted in the ostium (take-off) of an artery  26 , and more specifically into a branch  28  of the aortic arch  31  to filter the blood flowing into the artery  26  from the aortic arch  31 . The  FIG. 1  depiction also presents, without limitation, various candidate arteries for implantation of the filter assembly  30 , including the innominate artery (and attendant right carotid and right subclavian arteries), the left carotid artery, and the left subclavian artery. The  FIG. 1  depiction also identifies a superior direction  33  and an inferior direction  35  of the anatomy. Herein, “superior” and “inferior” refer to standard anatomical terms for the orientation of the filter assembly  30  when implanted in the artery  26  of the aortic arch  31 . 
     Referring to  FIGS. 2 through 4 , the filter assembly  30  is depicted for filtering blood flow into an artery according to embodiments of the disclosure. The filter assembly  30  includes a support structure  32  and a filter portion or structure  34 . The filter assembly  30  includes an anchor leg portion  46  and a filter leg portion  48 , the filter leg portion  48  including an elbow portion  52  that depends from the anchor leg portion  46  and an extension portion  53  that extends from said elbow portion  52 . The anchor leg portion  46  defines and extends along a first central axis  47 , and the filter leg portion  48  defines and extends along a second central axis  49 . The elbow portion  52  is arcuate about a lateral axis  54  to define an inner contour  56  and an outer contour  58 . 
     The anchor leg portion  46  defines a first opening  36 , the first central axis  47  being concentric with a center of the first opening  36 . The filter leg portion  48  defines a superior side  61  and an inferior side  63  of the filter assembly  30 . The first central axis  47  and the second central axis  49  project a minimum projected angle θ onto a lateral projection plane  66 , the minimum projected angle θ being defined about the lateral axis  54  and being less than 180 degrees. 
     For filter leg portions  48  having components with cross-sections normal to and surrounding the second central axis  49  along the extension portion  53 , the second central axis  49  is defined as concentric with the filter leg portion  48 . Examples of such components include the support structures  32   a  and  32   b  of  FIGS. 3 and 5 , respectively, and the filter elements  34   c ,  34   d , and  34   e  of  FIGS. 9, 12, and 17 , respectively. For filter leg portions  48  that do not surround the second central axis  49  along the extension portion  53  but instead have components with cross-sections normal to the second central axis  49  that only partially surround the second central axis  49 , the central axis  49  is defined as being centered between opposed lateral edges of the filter leg portion  48 . Examples include filter structures  34   f  and  34   g  of  FIGS. 19 and 20 , respectively, each of which define opposed lateral edge portions  248 . 
     The elbow portion  52  constitutes a segment of the filter assembly  30  that is bounded distally by boundary plane  62  and proximally by boundary plane  64 . Boundary plane  62  is normal to the first central axis  47  and intersects the first central axis  47  where the filter assembly  30  exits the ostium of the anchoring artery when properly implanted. Boundary plane  64  intersects the second central axis  49 , is orthogonal to the lateral projection plane  66 , and is tangent to an edge of the anchor leg portion  46 . The depiction of  FIG. 2  presents boundary planes  62  and  64  for a filter assembly  30  having a tubular filter leg portion  48 . Boundary planes  62  and  64  are also depicted at  FIG. 32  for a filter assembly  30  having a channel-shaped extension portion  53  of the filter leg portion  48 . 
     In some embodiments, the anchor leg portion  46  of the filter assembly  30  is dimensioned for anchoring within an innominate (brachiocephalic) artery. The filter leg portion  48  may extend proximally to a length long enough to cover the ostium of the left common carotid artery when implanted in an innominate artery of the aortic arch  31  of the heart. In some embodiments, the filter leg portion  48  is long enough to cover the ostia of both the left common carotid artery and the left subclavian artery when implanted in the innominate artery. 
     Functionally, the support structure  32  supports the filter structure  34  in a preferred orientation that filters blood entering one, some, or all of the inlets of the innominate artery, the left common carotid artery, and the left subclavian arteries at the aortic arch. During implantation, the anchor leg portion  46  of the support structure  32  is implanted within an anchoring artery (e.g., the brachiocephalic artery). The filter leg portion  48  may be oriented to extend over the inlets of arteries proximate the anchoring artery (e.g., the left common carotid artery and the left subclavian arteries). The anchor leg portion  46  is inserted into the anchoring artery  26 , contacting the walls of the anchoring artery  26  and bringing the filter leg portion  48  into contact with a superior surface of the aortic arch  31 . 
     This disclosure presents several embodiments of filter assemblies  30 , all of which have in common the support structure  32  and the filter structure  34 , albeit in configurations that differ from those presented in  FIGS. 2 and 3 . To distinguish the various embodiments, the filter assemblies, support structures, and filter structures are herein referred to generically or collectively by the reference characters  30 ,  32 , and  34 , respectively, and specifically or individually by these reference characters followed by a letter suffix (e.g., filter assembly  30   a  having the support structure  32   a  and filter structure  34   a  of  FIGS. 2 and 3 ). 
     For the filter assembly  30   a , the support structure  32   a  includes a tubular wall  42  that defines an area porosity  44 . The filter assembly  30   a  also defines a second opening  38 . For the filter assembly  30   a , the second opening  38  is defined by the filter leg portion  48 , and both of the openings  36  and  38  are be defined by the support structure  34   a . In some embodiments, the second opening  38  is defined by the anchor leg portion  46  ( FIG. 25 ) or within the elbow portion  52 , and one or both of the openings  36  and  38  may be defined by the filter structure  34  ( FIG. 18 ). 
     The filter assembly  30   a  defines an inside portion  102  that faces inward and an opposed outside portion  104  that faces outward. The filter structure  34   a  and the support structure  32   a  define a combined area porosity  106  that is less than the area porosity  44  of the support structure  32   a . In some embodiments, the filter structure  34   a  is arranged so that at least part of the outside portion  104  of the filter assembly  30   a  defines the combined area porosity  106  at the filter leg portion  48 , and at least part of the inside portion  102  defines the area porosity  44  at the filter leg portion  48 . Herein, an “area porosity” is defined by a ratio of the normal projected area of the voids of a porous material to the total normal area of the porous material. 
     In some embodiments, the mesh  84  from which the filter structure  34  is fabricated defines a porosity in the range of 50% to 98% inclusive; in some embodiments, in a range from 60% and 95% inclusive; in some embodiments, in a range from 70% and 95% inclusive; in some embodiments, in a range from 75% and 90% inclusive. In some embodiments, the support structure defines a porosity in the range of 60% to 98% inclusive; in some embodiments, in a range from 70% and 95% inclusive; in some embodiments, in a range from 75% and 95% inclusive; in some embodiments, in a range from 80% and 95% inclusive. 
     In some embodiments, a coarse wire mesh  82  is exposed on the inside portion  102  of the filter assembly  30   a  that contacts the superior surface of the aortic arch surrounding the inlets of the arteries. The pores of the coarse wire mesh  82 , being larger than the pores of the filter structure  34 , enables filtered blood to flow into artery inlets without further obstruction. 
     For permanent implants, the larger pores  76  of the coarse wire mesh  82  of the support structure  32  also facilitates securing the filter assembly  30 . Typically, after about 4 weeks&#39; time, tissue on the anchoring artery grow into the larger pores  76  of the coarse wire mesh  82  of the anchor leg portion  46 , and also enables the contacted tissue on the aortic arch to grow into the pores of the filter leg portion  48 . The growth of the tissue into the larger pores  76  of the support structure  32  secures the filter assembly  30  in the preferred orientation. 
     In some embodiments, the filter structure  34   a  is fabricated from an expanded sheet  70  (e.g., expanded metal;  FIG. 4 ) that defines a filter area porosity  68  and is coupled to filter leg portion  48 . For the filter assembly  30   a , the filter leg portion  48  includes the support structure  32   a  and the filter structure  34   a , with the filter structure  34   a  disposed on an exterior  72  of the support structure  32   a . Alternatively, the filter structure  34   a  may be disposed on an interior  74  of the support structure  32   a . One or both of the support structure  32 ,  32   a  and the filter structure  34 ,  34   a  defines a plurality of pores  76 . 
     In some embodiments, a method of manufacturing the filter assembly  30   a  includes weaving or braiding the support structure  32   a  about a substantially linear axis. Herein, “weaving” is a process that creates fixed cross-over points between crossing wires or filaments, whereas “braiding” is a process where the crossing wires or filaments are not fixed (i.e., crossing wires or filaments can slide with respect to each other). The support structure  32   a  is fitted over a curved mandrel (not depicted) to define the projected angle θ, and may be heat set on the mandrel to thermally set the curved shape of the support structure  32   a . The filter structure  34   a  is then coupled to the filter leg portion  48  of the support structure  32   a . The filter structure  34   a  may be attached to the support structure  32   a  with a threaded wire, a plurality of stitches, a plurality of point-wise tack welds, or a combination of such techniques. In some embodiments, the filter structure  34   a  is braided directly onto the filter leg filter leg portion  48  of the support structure  32   a.    
     Referring to  FIGS. 5 through 8 , a support structure  32   b  and a filter structure  34   b  are depicted according to an embodiment of the disclosure. The support structure  32   b  may be formed to shape as described for the support structure  32   a . The support structure  32   b  defines a coarse mesh  82 , and the filter structure  34   a  defines a fine mesh  84 . Herein, “coarse” and “fine” in relation to the meshes  82  and  84  are terms that are relative to each other. That is, the coarse wire mesh  82  is characterized as defining nominally larger pore sizes than the fine mesh  84 , for example with a braiding from larger diameter wire. For the filter structure  34   b , the mesh  84  is braided or woven, the filter structure  34   b  being depicted on a fabrication fixture  80 . 
     In some embodiments, the coarse mesh  82  is braided or woven with wire having a diameter in a range of 100 micrometers to 300 micrometers inclusive, with nominal pore sizes in a range of 0.5 millimeters to five millimeters inclusive. In some embodiments, the nominal pore sizes are in a range of two millimeters to seven millimeters inclusive. (Herein, a range that is said to be “inclusive” includes the endpoint values of the range as well as all values therebetween.) In some embodiments, a ratio of the nominal pore size of the support structure  32  to the nominal size of the filter mesh  84  of filter structure  34  is within a range of 2.5 to 55 inclusive; in some embodiments, the ratio is within a range of 2.5 to 40 inclusive; in some embodiments, the ratio is within a range of 2.5 to 25. In some embodiments, the coarse mesh  82  is a woven mesh and may be braided from a single wire. Likewise, in some embodiments, the fine mesh  84  is a woven mesh that may be braided from a single wire. 
     Herein, a “pore” is a void bounded by a structural component or components, for example the wires of a woven mesh (e.g., pores  76  of meshes  82  and  84  of  FIGS. 2 and 8 ). In some embodiments, the pores  76  result from a process of braiding or weaving metal wires or a polymer filaments (e.g., meshes  82 ,  84 ), for example by weaving or knitting. In some embodiments, the pores  76  result from an expanded metal process. In some embodiments, the pores  76  are formed on a structure, for example, a metal or polymer (e.g., the expanded sheet  70  of  FIG. 4 ). Formation may be performed with laser cutting or other manufacturing techniques available to the artisan. 
     “Pore size” is defined as the diameter of a largest circle  110  that will fit within the inner dimensions of the pore  76 . An illustration is depicted at  FIG. 24 . In some embodiments, the nominal pore sizes of a coarse mesh  82  are in a range of three millimeters to five millimeters inclusive. The fine mesh  84  may be braided with wire having a diameter in a range of 30 micrometers to 150 micrometers inclusive, with nominal pore sizes in a range 200 micrometers to 800 micrometers inclusive. In some embodiments, the filter structure  34  is a two-dimensional structure (e.g.,  FIG. 7 ) that conforms to a shape of the support structure  32  when coupled to support structure  32 . In some embodiments, the pores  76  are elongate (e.g., neither circular nor square), defining a major dimension  86  ( FIG. 8 ). 
     Examples of suitable metallic materials for the various filter assemblies  30  include so-called “super elastic” alloys such as certain nickel-titanium alloys (e.g., NITINOL), which allows up to 8% elastic deformation. Other examples of sufficiently elastic alloys include cobalt-chromium-nickel-molybdenum-iron (CoCrNi) alloys specified by ASTM F 1058 and ISO 5832-7, such as ELGILOY®, PHYNOX®, CONICHROME®, and FWM® 1058. Such CoCrNi alloys, though not “super elastic”, possesses sufficient elasticity by virtue of a high yield stress. 
     Referring to  FIG. 9 , a filter structure  34   c  having a plurality of apertures  114  on a superior side  116  is depicted according to an embodiment of the disclosure. The filter structure  34   c  may include various components and attributes as the filter assembly  30   a  and filter structures  34   a  and  34   b , which are indicated with same-numbered reference characters. For the filter structure  34   c , a tubular sleeve structure  112  is formed to shape and heat set. The plurality of apertures  114  are formed on the superior side  116  and may be sized greater than the pores  76  of the support structure  32  so that the wall area porosity  44  of the support structure  32  ( FIG. 3 ) defines the porosity of the filter assembly  30  through the plurality of apertures  114 . In some embodiments, one or more of the plurality of apertures  114  on the superior side  116  of the extension portion  35  of the filter structure  34   c  is arranged for substantial alignment with ostia of arteries that branch from the aortic arch  31 . 
     Herein, an “aperture” is a hole formed through a material, for example by cutting, punching, flaring, or by braiding about a mandrel. Accordingly, the apertures  114  are distinguishable from the pores  76  of the meshes  82  or  84 . That is, when formed on the mesh  82  or  84 , an aperture  114  refers to a through-hole defined by or through the mesh  82 ,  84  that is larger than the pores of the mesh  82 ,  84 . 
     Referring to  FIG. 10 , a mandrel  130  for shaping the filter structure  34   c  and forming the plurality of apertures  114  therein is depicted according to an embodiment of the disclosure. In some embodiments, fabrication of the filter structure  34   c  includes braiding the tubular sleeve structure  112  of the filter structure  34   c  about a substantially linear axis and fitting the tubular sleeve structure  112  over a mandrel  130 , the mandrel  130  including a plurality of apertures  132  that pass through a wall superior  134  of the mandrel  130  into a hollow  136  defined the mandrel  130 . The tubular support structure  112  may be heat treated on the mandrel  130  to thermally set the shape of the tubular support structure  112 . 
     In some embodiments, the plurality of apertures  114  of the tubular sleeve structure  112  are formed using the plurality of apertures  132  of the mandrel  130  as a guide, for example by passing a punch or a flare tool through the tubular sleeve structure  112  and into the apertures  132  of the mandrel  130 . In some embodiments, excess mesh material from the formation of the apertures  132  is rolled or folded back into the tubular sleeve structure  112  to form rims  138  about the apertures  132 . In some embodiments, the apertures  132  define an aperture diameter  140  that is within a range of three millimeters to eight millimeters inclusive. 
     The filter structure  34  is then coupled to the support structure  32 , for example the support structures  32   a  or  32   b . Other support structures  32  disclosed throughout this disclosure may also be utilized. In some embodiments, the step of coupling the filter structure  34  to the support structure  32  includes arranging the filter structure  34   c  on the exterior  72  ( FIG. 2 ). 
     Functionally, the plurality of apertures  114  can facilitate tissue growth into the filter leg portion  48 , which is desirable for permanent implants. Those apertures  114  which align with the ostia prevent reduction of blood flow into the arteries that would otherwise be caused by the presence of the mesh  35  over the ostia. 
     Referring to  FIGS. 11 through 15  a filter structure  34   d  with a perforated polymer overcoat  162  is depicted according to an embodiment of the disclosure. The filter structure  34   d  is depicted in a pre-implant configuration  164  ( FIG. 11 ) and the implanted configuration  22  ( FIG. 12 ). The filter structure  34   d  may include some components and attributes as the filter structure  34   c , some of which are indicated with same-numbered reference characters. The perforated polymer overcoat  162  defines a plurality of perforations  166 . In some embodiments, the perforated polymer overcoat  162  covers the outer contour  58  and a portion of the elbow portion  52  that is proximate thereto. The filter structure  34   d  may also include a tail structure  168  that is made from a plurality of strands of the mesh  84  and extends from either end (or both ends) of the tubular sleeve  112 . In some embodiments, the tail structure is held together with a crimp  170 . The crimp  170  may be made with a radiopaque material. 
     An artifact of some filter assemblies  30  when in the implanted configuration  22  is a distortion of the sizes of the pores  76  at the elbow portion  52 . Particularly, filter structures  34  that are arcuate about the second central axis  49  and define the outer contour  58  as arcuate about the lateral axis  54  are stretched or put in tension about the outer contour  58  of the elbow portion  52 . The stretching causes the pores  76  on the outer contour  58  to increase in size, in some cases by as much as 70% or more. Accordingly, the porosity of the filter structure  34   d  sans the perforated polymer overcoat  162  is increased in the vicinity of the outer contour  58 . The increased sizes of the pores  76  may diminish the filtering capability of the filter assembly  30 . The elbow portion  52 , being disposed upstream in the blood flow when deployed, is a particularly active filtering region of the filter assembly  30 . In some embodiments, the perforated polymer overcoat  162  is loaded with or coated with an anti-thrombic compound. 
     Functionally, the perforations  166  enable the porosity of the filter structure  34   d  to be controlled so that the porosity in the region of the outer contour  58  is in substantial uniformity with the remainder of the filter structure  34   d . In some embodiments, the perforations of the plurality of perforations are sized within a range of 0.2 to 0.8 millimeter diameter inclusive. Furthermore, the perforated polymer overcoat  162  may be of suitable flexibility to enable the filter assembly  30  to be straightened and collapsed for delivery. The tail structure  168  provides a snag for purposes of retrieving the filter assembly  30 . The crimp  170 , particularly when made of a radiopaque material, provides a location marker of the tail structure  168  for various imaging systems (e.g., x-rays). Loading the perforated polymer overcoat  162  polymer with the anti-thrombic compound can cause the overcoat  162  to elute the anti-thrombic compound over time, thereby reducing fibrin formation and preventing clots from forming and growing or otherwise preventing platelets from clumping and preventing clots from forming and growing on the perforated polymer overcoat  162 . 
     In fabrication, the tubular sleeve  112  the filter structure  34   c  may be braided about a substantially linear axis ( FIG. 11 ) and fitted over a mandrel (not depicted) for shaping and heat setting, thereby defining the outer contour  58  of the elbow portion  52  ( FIGS. 12 and 13 ). In some embodiments, a liquid polymer  172  may is applied over and in the region of the outer contour  58  of the elbow portion  52 . The liquid polymer  172  may fill the pores  76  ( FIG. 14 ) or at least partially fill the pores  76  of the mesh  84 . The liquid polymer  172  sets to define a polymer coating  174 , and the perforations  166  formed that pass through the thickness of the polymer coating  174  ( FIG. 15 ). 
     The perforations  166  may be formed, for example, using a laser cutting process or a mechanical puncturing process. Various perforation techniques can be adapted to form the perforations  166  while not substantially compromising the structural integrity of the mesh  84 . For example, laser cutting may utilize a laser intensity that is suitable for cutting the polymer coating  174  but that does not damage a mesh  84  that is metallic. In another example, a mechanical puncturing process may incorporate needles that come to a sharp point that deflects either the (metallic) mesh  84  or the needle punch upon incidence with the mesh  84 . 
     The technique of applying the perforated polymer overcoat  162  is not limited to filter structures  34 . Certain embodiments include support structures  32  that may perform a filtering function (e.g., the support structure  32   f  of  FIG. 19 ), which may also be subject to distortion of the pores  76  in the implanted configuration  22 . Accordingly, the perforated polymer overcoat  162  may find remedial application on support structures  32  as well. 
     While the embodiment of  FIGS. 11 through 15  depict a wire braid or weave for the mesh  84 , those of ordinary skill in the art, in view of this disclosure, will recognize that the same pore expansion phenomenon can occur with other mesh forms (e.g., expansion meshes) and can apply the same technique thereto. 
     Referring to  FIGS. 16 and 17 , a filter structure  34   e  is depicted in the pre-implant configuration  164  and the implanted configuration  22 , respectively, according to an embodiment of the disclosure. The filter structure  34   e  may include some components and attributes as the filter structure  34   d , some of which are indicated with same-numbered reference characters. 
     In the pre-implant configuration  164 , the filter structure  34   e  is characterized by a partial discontinuity  186  at the elbow portion  52  that forms mitered edges  188 . The mitered edges  188  define a miter angle ϕ when the tubular sleeve structure  112  is substantially concentric with a linear axis  192 . A hinge portion  194  bridges one side of the discontinuity  186 . In the implanted configuration  22 , the discontinuity  186  is closed to form a miter  196 , with the hinge portion  194  aligned along the outer contour  58  of the implanted configuration  22 . The miter angle ϕ may be sized so that a resulting angle α about the miter  196  of the implanted configuration  22  is congruent with the desired minimum projected angle θ. In some embodiments, the form of the implanted configuration  22  of the filter structure  34   e  is maintained by the support structure  32 , for example support structures  32   a  or  32   b . Other support structures  32  disclosed throughout this disclosure may also be utilized with the filter structure  34   e.    
     Fabrication of the filter structure  34   e  may include braiding or weaving the tubular sleeve structure  112  of the filter structure  34   e  about a substantially linear axis and partially severing the tubular sleeve structure  112 , leaving the hinge portion  194  in place. Folds or rolls  198  may be formed at the edges of the partial sever by folding or rolling the severed edges back along the inside of the tubular sleeve structure  112  to define the mitered edges  188 . The degree to which the severed edges are folded or rolled back defines the miter angle ϕ of the filter structure  34   e  when in the implanted configuration  22 . The filter structure  34   e  may be formed to the shape of the implanted configuration  22  using a mandrel (not depicted) and heat setting the shape. 
     Functionally, the pores  76  of the filter structure  34   e  experience less distortion in the implanted configuration  22  than do the pores  76  of certain filter structures  32 , such as filter structure  32   d . As a result, in some embodiments, the porosity along the outer contour  58  of the filter structure  34   e  in the implanted configuration  22  is not substantially increased, and may not require remedial attention, such as the perforated polymer overcoat  162  ( FIG. 12 ). 
     Referring to  FIGS. 18 and 19 , a filter assembly  30   f  including a support structure  32   f  and a filter structure  34   f  is depicted according to an embodiment of the disclosure. For this embodiment, the mesh  84  of the filter structure  34   f  is a woven wire mesh. The filter structure  34   f  extends from the anchor leg  46  over a portion of the filter leg  48 , including over the elbow portion  52 . The support structure includes a pair of rails  222  that are integral with and extend in a proximal direction  216  from the filter structure  34   f . The rails  222  have a wider or thicker cross section than the strands of the mesh  84  of the filter structure  34   f . In some embodiments, the rails  222  extend in a distal direction  218  into the filter structure  34   f . The rails  222  each include a proximal end portion  224  and a distal end portion  226 . The proximal end portions  224  that may be coupled together to form a loop  228 . Herein, “proximal” and “distal” are relative terms that refer generally to the direction of blood flows, with proximal being generally upstream of the blood flow from distal. For the support structure  32   f , two rails  222  are depicted, but additional rails are also contemplated. 
     The filter structure  34   f  extends from a distal end  232  to a proximal end  234 , defining an assembled length  236 . The filter structure  34   f  may define a channel-shaped portion  238  at the proximal end  234  and transition to a closed neck portion  244  at the distal end  232  that defines the first opening  36  of the filter assembly  30   f . In some embodiments, the first opening  36  is bounded by a hoop structure  242  that is integral with the filter structure  34   f . The rails  222  may extend to the hoop structure  242 . The channel-shaped portion  238  may define a cross-section  246  in a plane that is orthogonal to the second central axis  49 . The cross-section may define, for example, a U-shape (depicted) or a V-shape. The channel-shaped portion  238  includes opposed lateral edge portions  248  separated by a web portion  252 . The filter structure  34   f  is coupled to the rails  222  at the opposed lateral edge portions  248  and at the closed neck portion  244 . 
     The rails  222  extend at beyond the proximal end  234  of the filter structure  34   f  to define an inside length  254  of the loop  228 . The inside length  254  is defined as the distance along the second central axis  49  from the proximal end  234  of the filter structure  34 ,  34   f  to an intersection of an inside surface of the loop  228  with the second central axis  49  when the filter assembly  30 ,  30   f  is in a pre-implant configuration ( FIG. 18 ). In some embodiments, a ratio of the assembled length  236  to the inside length  254  when in the pre-implant configuration  164  is in a range of 5 to 1 inclusive. In some embodiments, a ratio of the inside length  254  to the assembled length  236  in the pre-implant configuration  164  is in a range of 1.25 to 2.5 inclusive. In some embodiments, a ratio of the inside length  254  to the length assembled  236  in the pre-implant configuration  164  is in a range of 1.4 to 2 inclusive. 
     In fabrication, the filter structure  34   f  may be interlaced with the rails during formation of the mesh  84  of the filter structure  34   f  In this way, the rails  222  are incorporated into mesh  84 . The distal end portions  226  of the rails  222  may be woven into the mesh  84 . In this way, the filter structure  34   f  captures the rails  222 . The rails  222 , being substantially stouter than the filter structure  34   f , provide support for the filter structure  34   f.    
     The distal end portions  226  of the rails  222  may be tightly woven into the mesh  84  at or proximate the closed neck portion  244 . In contrast, the rails  222  may be loosely woven into the mesh  84  within the channel-shaped portion  238 . Other forms of attaching the rails to the mesh  84  may also be implemented, for example tac welding. In some embodiments, the hoop structure  242  is formed by rolling or folding excess material of the mesh  84  at the first opening  36 . 
     The rails  222  are coupled together at the proximal end portions  224  and formed to shape the loop  228 . The loop  228  defines the inside length  254  beyond the proximal end  234  of the filter structure  34   f  when in the pre-implant configuration  164 . The proximal end portions  224  of the rails  222  may be coupled, for example, with a crimp  258 , which may comprise a radiopaque material. Other techniques for coupling the proximal end portions  224  of the rails  222  include, for example, twisting together, fusion, and tac welding. The filter assembly  30   f  is formed to shape (e.g., with mandrel) and heat set. 
     Functionally, the tight weave of the mesh  84  about the distal end portions  226  of the rails  222  may secure the rails  222  to the filter structure  34   f . Conversely, the loose weave of the mesh  84  about the rails  222  within the channel-shaped portion  238  enables a sliding action between the rails  222  and the channel-shaped portion  238 . The sliding fit of the loose weave in combination with the inside length  254  facilitates collapsing the filter assembly  30   f  for deployment. Herein, to “collapse” the filter assembly  30  refers to substantially straightening the filter assembly  30  about a linear axis and constricting the filter assembly  30  to within a reduced diameter (typically about two millimeters) for insertion into a delivery device. 
     When the mesh  84  is collapsed, the pores  76  are elongated, causing the major dimension  86  ( FIG. 8 ) of mesh  84  to increase. The cumulative effect of the elongation of the pores  76  cause the collapsed mesh  84  to extend axially. Because of the loose weave between the rails  222  and the channel-shaped portion  238 , the channel portion  238  slides over the rails  222  toward the proximal end portions  224 . The inside length  254  provided by the support structure  32   f  provides space within the loop  228  for the cumulative elongation of the filter structure  34   f . The sliding action also accommodates repositioning of the channel-shaped portion  238  relative to the rails  222  when transitioning between the pre-implant configuration  164  and the implanted configuration  22 , which limits stresses imposed on the mesh  84 . 
     The hoop structure  242  may enhance separation of the rails  222  from each other when transitioning between a collapsed configuration to the implanted configuration  22 . The hoop structure  242  may also provide some biasing of the first opening  36  against the wall of the host artery. The loop  228  assures capture of the filter structure  34   f  within the support structure  32   f . The radiopaque crimp  258 , when utilized, serves as a location marker for various imaging systems. The crimp  258  can also function as a snare to facilitate retrieval of the filter assembly  30   f . The larger cross section of the rails  222  relative to the strands of the mesh  84  enable the rails  222  to support and shape the filter structure  34   f , causing the filter structure  34   f  to conform to the heat set shape of the rails  222 . The cross sections of the rails  222  also provide spring biasing of the filter leg portion  48  for seating against the roof of the aortic arch  31 . 
     In some embodiments, the rails  222  are made of wire. The wire is of substantially heavier gauge than that of the mesh  84 . In some embodiments, the diameter of the wire forming the rails  222  is in a range of 100 to 500 micrometers inclusive; in some embodiments, in a range of 100 to 350 micrometers inclusive. In some embodiments, the cross-sections of the rails  222  may range from 0.03 to 0.4 square millimeters inclusive. 
     Referring to  FIGS. 20 through 29 , a filter assembly  30   g  including a support structure  32   g  and a filter structure  34   g  is depicted according to an embodiment of the disclosure. The filter assembly  30   g  includes some of the same components and attributes as the filter assembly  30   f , some of which are indicated with same-numbered reference characters. The support structure  32   g  includes an anchor portion  302  distal to the rails  222 . In some embodiments, the anchor portion  302  is an expanded tube structure  304 . The rails  222  may be unitary with the expanded tube structure  304 . 
     A planar projection  306  of a pre-expanded tube structure  308  prior to expansion is depicted at  FIGS. 21 and 22 . A planar projection  312  of the expanded tube structure  304  after expansion is depicted at  FIGS. 23 and 24 . Pre-expansion pores  314  define an elongate shape having a pre-expansion major dimension  316  ( FIG. 22 ). After expansion, the pores  76  define a major dimension  318 . Because of the lateral expansion of the pre-expanded tube structure  308 , the post-expansion major dimension  318  is substantially shorter than the pre-expansion major dimension  316 . The pores  76  define the coarse mesh  82  relative to the fine mesh  84  of the filter structure  34   g . In some embodiments, a distal edge  320  of the anchor portion  302  defines a taper  321  at a distal extremity  322 . The distal extremity  322  may define a hook portion  324  ( FIG. 24 ). In some embodiments, the rails  222  are also formed from the pre-expanded tube structure  308  ( FIG. 21 ), thereby being unitary with the anchor portion  302 . In some embodiments, the pre-expanded tube structure  308  has a wall thickness that is substantially greater than the diameter of the strands of the mesh  84 , and the tangential (height) dimension is tailored to provide the desired rigidity. In some embodiments, the wall thickness of the pre-expanded tube structure is within a range of 0.007 inches to 0.15 inches inclusive. The tangential dimension (height) of the rails  222  are cut to within a range of 0.007 inches to 0.04 inches inclusive. Accordingly, the rails  222  are substantially stouter than the mesh  84 . 
     The filter structure  34   g , depicted at  FIGS. 27 through 29 , may be a channel or “half pipe” structure  332 , akin to the channel-shaped portion  238  of the filter structure  34   f . The channel structure  332  includes a proximal end  334  and a distal end  336 . A tail  335  may extend from the proximal edge  334  and include a crimp  337  of radiopaque material. The channel structure  332  may include hem structures  338  formed at the lateral edge portions  248 . The rails  222  extend through the hem structures  338  to support the filter structure  34   g . The rails  222  thereby capture the filter structure  34   g  between loop  228  and the anchor portion  302 . Like the channel-shaped portion  238  of the filter structure  34   f , the channel structure  332  may define the cross-section  246  having a U-shape or a V-shape. 
     In fabrication, the pre-expansion pores  314  and hook portion  324  are formed in the pre-expanded tube structure  308 , for example in a laser cutting process. The pre-expanded tube structure  308  may also be trimmed to define the taper at the distal edge  320 . In some embodiments, elongate segments  309  (depicted in phantom in  FIGS. 25 and 26 ) of the pre-expanded tube structure  308  are also cut from the pre-expanded tube structure  308  to define the rails  222 . The pre-expanded tube structure  308  is expanded to form the anchor portion  302 . 
     For the filter structure  34   g , the hem structures  338  may be formed by folding and fastening lateral extremities  344  of the mesh  84  to the web portion  252  to define the lateral edge portions  248 . Fastening of lateral extremities  344  to the web portion  252  may be accomplished, for example, with an interwoven wire  340 . The hem structures  338  are slid over the open rails  222  and brought into contact with the anchor portion  302 . In some embodiments, the distal end  336  of the channel structure  332  is attached to the anchor portion  302 , for example, with wire sutures or crimps  346 . The crimps  346  may include a radiopaque material. The distal end  336  of the filter structure  34   g  may be disposed inside the second opening  38  the anchor portion  302 , wrapped around the second opening  38  of anchor portion  304 , or brought into abutment or otherwise align with the second opening  38  of the anchor portion  304 . In the abutment option, the distal end  336  of the filter structure  34   g  defines a radius that is substantially the same as the radius of the anchor leg  46  about the first central axis  47 , thereby reducing the effect of any axial discontinuity at the second opening  38 . 
     The proximal end portions  224  of the rails  222  are formed to shape the loop  228  and define the inside length  254  beyond the proximal end  234  of the filter structure  34   g . As with the filter assembly  30   f , the proximal end portions  224  of the rails  222  may be coupled with a radiopaque crimp  258  (depicted), or by other techniques available to the artisan. The filter assembly  30   g  is formed to shape (e.g., with mandrel) and heat set. 
     In some embodiments, the filter structure  34   g  is fabricated from a polymer material. The pores  76  of the mesh  84  may be formed, for example, by laser cutting and/or expansion techniques. The hem structures  338  may be fabricated by fusing the lateral extremities  344  of the mesh  84  to the web portion  252 . 
     Functionally, the hem structures  338  facilitate sliding of the filter structure  34   g  along the rails during the axial elongation that occurs when collapsing the filter assembly  30   g  for deployment. The hem structures  338  also facilitate assembly of the filter assembly  30   g  without interlacing the mesh  84  onto the support structure  32 , and also enable use of different materials (e.g., polymer) for the filter structure  34   g . As with the filter assembly  30   f , the sliding action accommodates repositioning of the channel-shaped portion  238  relative to the rails  222  when transitioning between the pre-implant configuration  164  and the implanted configuration  22 . 
     When implanted in the aortic arch  31 , filter structures  34  that have a channel-shaped portion  238  (e.g., filter structures  34   a ,  34   f , and  34   g ) suspend the mesh  84  of the web portion  252  away from the roof of the aortic arch  31  and the ostia of the arteries, which reduces the effect of pore blockage. Consider a configuration where the mesh structure is in apposition with the aortic roof at the perimeter of the ostia. Essentially, all of the blood flowing into the respective artery must pass through those pores which are bounded by the perimeter of the respective ostium. If some of the pores become blocked, the flow area into the artery is partially obstructed. Should such blockage become significant, blood flow into the artery may be substantially compromised. 
     By suspending the mesh  84  away from the ostia, the blood flow into a given artery is spread over a larger area of the filter structure  34 . Spreading the blood flow over a larger area (i.e., over more pores of the filter structure  34 ) mitigates the effect of pore blockage. That is, if emboli entrained in the blood flow blocks a pore  76  of filter structure  34 , the blockage affects a smaller fraction of the total number of pores  76  through which blood flows. Also, should several pores  76  become blocked such that the blockage of pores becomes significant, the blood flow will flow around the significant blockage by utilizing more pores adjacent to the blockage. The suspension of web portion  252  away from the roof of the aortic arch  31  also facilitates the self-cleaning aspect of the filter assembly  30 . The separation enables cross flows to occur through the filter structure  34  during the cardiac cycle that may dislodge emboli from the pores of the mesh  34 , with the emboli being returned to the aortic arch and away from the inlets of the arteries. 
     It is noted that the web portion  252  does not need to be arcuate for to have the beneficial effect described above. The web portion may extend linearly between the rails and provide the same effect, provided that the location of the seating of the rails  222  against the aortic arch  31  provides adequate separation between the mesh  84  and the ostia of the filtered arteries. 
     The crimps  346  secure the distal end  336  the filter structure  34   g  to the anchor portion  302 , thereby maintaining coverage of the elbow portion  52  with the filter structure  34   g . The crimps  346 , when including a radiopaque material, serve as a location marker of the junction between the filter structure  34   g  and the anchor portion  302  that can be viewed with various imaging systems. The crimp  337  of the tail  335  can function as a snare for retrieval of the filter assembly  30   g.    
     The loop  228  assures capture of the filter structure  34   g  within the support structure  32   g . The crimp  258  not only provide closure of the loop  228 , but can also facilitate retrieval of the filter assembly  30   g . A radiopaque crimp  258 , when utilized, serves as a location marker for various imaging systems. The increased cross section of the rails  222  relative to the strands of the mesh  84  enable the rails  222  to support the filter structure  34   g  and to cause the filter structure  34   g  to conform to the heat set shape of the rails  222 . The cross sections of the rails  222  also provides spring biasing of the filter leg portion  48  for seating against the roof of the aortic arch  31 . 
     Referring to  FIGS. 30 through 33 , a three dimensional (3D) contoured shape  400  tailored to provide substantially continuous (sealed) posterior and anterior contact about the ostia of the heart is depicted according to an embodiment of the disclosure. The depiction of  FIG. 30  portrays the filter assembly  30  implanted in the innominate artery  402  and extending over the ostia of the left carotid artery  404  and the left subclavian artery  406 . A blood flow  408  is depicted as passing through the filter assembly  30  into the arteries  402 ,  404 , and  406 . Also depicted are the superior direction  33  and the inferior direction  35  of the filter assembly  30  when implanted, and the lateral projection plane  66 . The lateral projection plane  66  is coplanar with first central axis  47  and centered about the second central axis  49 . The projection plane  66  is defined as being “centered” about the second central axis  49 , for example by a least-squares fit between the second central axis  49  and the projection plane  66 . 
     In general and approximate terms, the lateral projection plane  66  is parallel to the coronal plane of the human body and orthogonal to an anterior direction  412  and posterior direction  414  of the human body. While depictions of the filter assembly  30  in  FIGS. 30 through 33  correlate specifically with the features of the filter assembly  30   f , the principles governing the 3D contoured shape  400  are similar for all filter assemblies  30  depicted herein, such that, in view of this disclosure, an artisan of ordinary skill can apply the governing principles mutatis mutandis for all filter assemblies  30  presented herein. The various arteries  402 ,  404 , and  406  are not typically coplanar, and typically do not enter the aortic arch  31  normal to the aortic wall. Accordingly, to provide a snug fit between the filter assembly  30  and the aortic arch  31 , it is advantageous to tailor the filter assembly  30  to conform to the aortic arch  31 . 
     The depictions of  FIGS. 31 through 33  present an outline  420  of the relevant aspects of the filter assembly  30 , and include some of the same components and attributes presented throughout this disclosure, some of which are identified by same-numbered reference characters. These include the lateral edge portions  248 , identified individually as a first lateral edge portion  248   a  and a second lateral edge portion  248   b . Also included in the outline  420  is the first central axis  47 , the second central axis  49 , the anchor leg portion  46 , the filter leg portion  48 , the first opening  36 , and the second opening  38 . The second opening  38  is located at the junction between the anchor leg portion  46  and the filter leg portion  48 . 
     A roof  416  of the aortic arch  31  presents an arcuate shape. As such, the lateral edges  248  of the filter  34  may also be arcuately shaped to better conform to the profile of the aortic roof  416 . Because of the arcuate cross-section  246  of the web portion  252 , the seating of the rails against the aortic roof  416  does not put the web portion  252  in apposition with the aortic roof  416 . The benefit of such an arrangement is described attendant to filter assembly  30   g  at  FIGS. 20 through 29 . When implanted, the first central axis  47  in the depicted example is concentric with the innominate artery  402 , and therefore generally is not normal to the aortic roof  416 . Accordingly, as projected onto the lateral projection plane  66 , the portion of the aortic roof  416  that contacts the first lateral edge portion  248   a  extends further in the superior direction  33  than does the portion of the aortic wall that contacts the second lateral edge portion  248   b  ( FIG. 32 ). Ergo, the first lateral edge portion  248   a  may be configured to extend further in the superior direction  33  than is the second lateral edge portion  248   b . The arcuate shape of the lateral edges  248  may also be characterized as arcing in the inferior direction  35 . 
     The filter assembly  30  may also accommodate the non-linear arrangement of the ostia of the innominate artery  402 , the left carotid artery  404 , and the left subclavian artery  406 . Generally, the left carotid artery  404  is located further in the anterior direction  412  than is the left subclavian artery  406 . Accordingly, the lateral edge portions  248  may arc generally in the posterior direction  414  ( FIG. 31 ), so that the second central axis  49  is in substantial alignment with the centers of the ostia of the arteries  404  and  406 . 
     The filter assembly  30  may be configured during fabrication as outlined above and heat set to adopt the stated characteristics in the pre-implant configuration  164 . Functionally, the conformance of the filter assembly  30  to the aortic wall prevents emboli from bypassing the filter structure  34  and entering the arteries  402 ,  404 , and  406 . The conformance also enables substantial contact along the aortic arch  31  without application of an excessive biasing. Any reduction in the biasing force generally reduces erosion and irritation of the aortic roof  416 , and can also reduce distortions of the filter assembly  30 . 
     Each of the disclosed embodiments defines a minimum projected angle θ, which may also be described in reference to the outline  420  of  FIGS. 31 and 32 . The minimum projected angle θ is a minimum angle defined by the first central axis  47  and a projection of a tangent line  422  that is tangent to the second central axis  49 , as the line is projected onto the lateral projection plane  66 . For the outline  420 , a tangent point  424  is identified on the second central axis  49  where the tangent line  422  that defines the minimum (smallest) projected angle θ. Note that the trajectory of the tangent line  422  itself may not be parallel to the lateral projection plane  66 , as depicted in  FIG. 31 . However, the depiction of  FIG. 32  provides a view that is orthogonal to the lateral projection plane  66 , and thus presents the projected angle θ. 
     The minimum projected angle θ of  FIG. 32  defines a projected angle θ that is obtuse. However, acute projected angles θ angle are also contemplated and disclosed herein (e.g., at  FIG. 4 ). In some embodiments, the projected angle θ is in a range of 40 degrees to 80 degrees inclusive. In some embodiments, the projected angle θ is in a range of 50 degrees to 70 degrees inclusive. 
     Each of the additional figures and methods disclosed herein can be used separately, or in conjunction with other features and methods, to provide improved devices and methods for making and using the same. Therefore, combinations of features and methods disclosed herein may not be necessary to practice the disclosure in its broadest sense and are instead disclosed merely to particularly describe representative and preferred embodiments. 
     Various modifications to the embodiments may be apparent to one of skill in the art upon reading this disclosure. For example, persons of ordinary skill in the relevant arts will recognize that the various features described for the different embodiments can be suitably combined, un-combined, and re-combined with other features, alone, or in different combinations. Likewise, the various features described above should all be regarded as example embodiments, rather than limitations to the scope or spirit of the disclosure. 
     Persons of ordinary skill in the relevant arts will recognize that various embodiments can comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the claims can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     Unless indicated otherwise, references to “embodiment(s)”, “disclosure”, “present disclosure”, “embodiment(s) of the disclosure”, “disclosed embodiment(s)”, and the like contained herein refer to the specification (text, including the claims, and figures) of this patent application that are not admitted prior art. Herein, references to “proximal” and associated derivative terms refer to a direction or position that is toward the surgeon or operator. References to “distal” and associated derivative terms refer to a direction or position that is away from the surgeon or operator. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in the respective claim.