Abstract:
Intravascular filters such as embolic protection filters can be configured to capture embolic debris when deployed within a patient&#39;s vasculature. In particular, intravascular filters such as embolic protection filters can be configured to reduce or eliminate emboli becoming ensnared in the stagnant flow patterns that can otherwise arise near a filter-vascular wall junction.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates generally to intravascular filters and methods of their formation. In particular, the invention relates to intravascular filters configured for improved vasculature interaction.  
       BACKGROUND  
       [0002]     Heart and vascular disease are major problems in the United States and throughout the world. Conditions such as atherosclerosis result in blood vessels becoming blocked or narrowed. This blockage can result in lack of oxygenation of the heart, which has significant consequences since the heart muscle must be well oxygenated in order to maintain its blood pumping action.  
         [0003]     Occluded, stenotic, or narrowed blood vessels may be treated with a number of relatively non-invasive medical procedures including percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA), and atherectomy. Angioplasty techniques typically involve the use of a balloon catheter. The balloon catheter is advanced over a guidewire such that the balloon is positioned adjacent a stenotic lesion. The balloon is then inflated and the restriction of the vessel is opened. During an atherectomy procedure, the stenotic lesion may be mechanically cut away from the blood vessel wall using an atherectomy catheter.  
         [0004]     During angioplasty and atherectomy procedures, embolic debris can be separated from the wall of the blood vessel. If this debris enters the circulatory system, it could block other vascular regions including the neural and pulmonary vasculature. During angioplasty procedures, stenotic debris may also break loose due to manipulation of the blood vessel.  
         [0005]     Because of this debris, a number of devices, such as intravascular filters, have been developed to filter out this debris. A need remains for improved intravascular filters. A need remains for improved methods of manufacture of intravascular filters.  
       SUMMARY  
       [0006]     The invention is directed to intravascular filters such as embolic protection filters that are configured to capture embolic debris when deployed within a patient&#39;s vasculature.  
         [0007]     Accordingly, an example embodiment of the invention can be found in a filter assembly that includes a support hoop, a filter membrane that has a proximal end that is secured to the support hoop, and stagnation prevention means that extend proximally from the support hoop.  
         [0008]     Another example embodiment of the invention can be found in an embolic protection filter that includes a support hoop, a filter membrane having a proximal region secured to the support hoop, and a filter fillet that is positioned proximate the support hoop and that extends proximally from the support hoop.  
         [0009]     Another example embodiment of the invention can be found in a method of forming a filter. A support hoop is provided. A filter membrane is formed, where the support hoop is positioned such that a proximal region of the filter membrane forms around the support hoop and encapsulates the support hoop. The filter membrane includes an extension that extends proximally from the support hoop.  
         [0010]     Another example embodiment of the invention can be found in a method of capturing stagnant emboli. A filter is provided that includes a support hoop and a filter membrane. The filter membrane includes an extension portion that extends proximally from the support hoop. The filter is deployed within a vasculature including a vascular wall, where the proximal portion of the filter membrane and the extension portion contact the vascular walls. The extension portion is configured to prevent emboli from stagnating proximate the support hoop and the vascular wall. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0011]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0012]      FIG. 1  is a perspective view of an intravascular filter in accordance with an embodiment of the invention;  
         [0013]      FIG. 2  is a closer view of a portion of the filter membrane included in the intravascular filter of  FIG. 1 ;  
         [0014]      FIG. 3  is a perspective view of the intravascular filter of  FIG. 1 , shown deployed within an artery or vein; and  
         [0015]      FIG. 4  is an axial cross-section view of a portion of  FIG. 3 . 
     
    
       [0016]     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.  
       DETAILED DESCRIPTION  
       [0017]     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.  
         [0018]     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.  
         [0019]     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).  
         [0020]     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.  
         [0021]     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The drawings, which are not necessarily to scale, depict illustrative embodiments of the claimed invention.  
         [0022]      FIG. 1  is a perspective view of an example intravascular filter  10 , which includes a filter membrane  12 . The filter membrane  12  can be formed from any suitable moldable material or combination of materials. For example, the filter membrane  12  can include polymers such as polyether block amide, polybutylene terephthalate/polybutylene oxide copolymers sold under the Hytrel and Arnitel trademarks, Nylon 11, Nylon 12, polyurethane, polyethylene terephthalate, polyvinyl chloride, polyethylene naphthalene dicarboxylate, olefin/ionomer copolymers, polybutylene terephthalate, polyethylene naphthalate, ethylene terephthalate, butylene terephthalate, ethylene naphthalate copolymers, polyamide/polyether/polyester polyamides, aromatic polyamides, polyurethanes, aromatic polyisocyanates, polyetheretherketone, polycarbonates, polyamide/polyether, and polyester/polyether block copolymers, among others.  
         [0023]     In some embodiments, the filter membrane  12  can be formed from at least one of polyether block amide, olefin/ionomer copolymers, nylon, polyurethane, polyethylene terephthalate, polyvinyl chloride, polyethylene naphthalene dicarboxylate and mixtures or copolymers thereof.  
         [0024]     The filter membrane  12  can be porous, having pores  14  that are configured to permit blood flow while retaining embolic material of a desired size. The pores  14  are seen in greater detail in  FIG. 1 . While the pores  14  as illustrated are at least substantially circular in profile, other profiles are contemplated as well. The filter membrane  12  can have a mouth  16  and a closed end  18  and is capable of moving between an open state and a closed state. The mouth  16  can be sized to occlude the lumen of the body vessel in which the filter may be installed, thereby directing all fluid and any emboli through the filter.  
         [0025]     A support hoop  20  can be attached to the filter membrane  12  at or proximal to the mouth  16 . The support hoop  20  can be attached to the filter membrane  12  through melt bonding or other suitable means. In some embodiments, as discussed in greater detail hereinafter, the support hoop  20  can be integrally molded within the filter membrane  12 . The support hoop  20  has an expanded state and a compressed state. The expanded state of the support hoop  20  is configured to urge the mouth  16  to its full size, while the compressed state permits insertion into a small lumen.  
         [0026]     The support hoop  20  can be made from a flexible metal such as spring steel, from a super-elastic elastic material such as a suitable nickel-titanium alloy, or from other suitable material. The support hoop  20  can be a closed hoop made from a wire of uniform diameter, it can be a closed hoop made from a wire having a portion with a smaller diameter, it can be an open hoop having a gap, or it can have another suitable configuration.  
         [0027]     A strut  22  can be fixedly or slideably attached to and extend from the support hoop  20 . An elongate member  24  can be attached to and extend from the strut  22 . The elongate member  24  can be attached to the strut  22  at an angle or the strut  22  can have a small bend, either at a point or over a region. The strut  22  can be attached to the support hoop  20  at a slight angle such that when the elongate member  24 , the strut  22 , and the support hoop  20  are in an unconstrained position, the elongate member  24  can generally extend perpendicular to the support hoop  20 .  
         [0028]     In the unconstrained position, the elongate member  24  can also lie along an axis which passes through the center of the region created by the support hoop  20 . This may help position the support hoop  20  in contact with the wall of a vascular lumen or it may help in enhancing predictability or reliability during deployment. In some embodiments, the elongate member  24  can terminate at the strut  22 . In other embodiments, the elongate member  24  can extend through the filter membrane  12 , as shown. Whether or not the elongate member  24  extends through the filter membrane  12 , it may be fixedly or slideably/rotatably attached to the filter membrane  12 .  
         [0029]     The filter membrane  12  can include a waist  26  at the closed end  18 . In some embodiments, the waist  26  can be integrally formed with the filter membrane  12 . In other embodiments, the filter membrane  12  can be further processed to form the waist  26 . In some embodiments, integrally forming the waist  26  with the filter membrane  12  can reduce the outer diameter of the filter device when in a compressed state, increase the reliability and uniformity of the bond between the filter membrane and the elongate member, and reduce the number of steps or components needed to form the filter device.  
         [0030]     The waist  26  is a region largely incapable of moving between two states and having a lumen of substantially constant diameter therethrough. The elongate member  24  can extend through and be bonded to the waist  26 . This bonding can be heat bonding such as laser bonding or may be an adhesive or other suitable means.  
         [0031]     With respect to  FIG. 3 , the intravascular filter  10  can be deployed within a vasculature  28  that can include an artery or a vein within a patient. For illustration purposes only, the vasculature  28  will be referred to herein as the vessel  28 . In some embodiments, the vessel  28  can include vessel walls  30 . As can be seen, the open mouth end  16  can be in substantial contact with the vessel walls  30  at a contact point  34 . In some embodiments, at least a proximal portion  32  of the filter membrane  12  can also be in substantial contact with the vessel walls  30 , depending on the particular geometry of the vessel  28 .  
         [0032]      FIG. 4  is an axially aligned partial section view of  FIG. 3 , taken near the contact point  34 . In this illustration, the support hoop  20  can be seen embedded within the filter membrane  12 . In some embodiments, a fillet  36  that is integrally formed with the filter membrane  12  can extend proximally beyond the support hoop  20 . The fillet  36  can extend circumferentially at least partially around the support hoop  20 . In some embodiments, the fillet  36  can extend circumferentially substantially or completely around the support hoop  20 .  
         [0033]     As can be seen in  FIG. 4 , the fillet  36  provides a more gradual transition to the open mouth end  16  of the intravascular filter  10 . The fillet  36  can taper from a more distal position  38  proximate the support hoop  20  to a proximal position  40 . At the distal position  38 , the fillet  36  can have a material thickness T that is about equal to that of the filter membrane  12 . The fillet  36  can have an overall thickness W at the distal position  38  that is about equal to a cross-sectional diameter D of the support hoop  20  plus twice the thickness T of the filter membrane  12 .  
         [0034]     At the proximal position  40 , the fillet  36  can have a thickness W that tapers to about zero. The fillet  36  can have any suitable length L. In some embodiments, the fillet  36  has a length L that is about one to four times a cross-sectional diameter D of the support hoop  20 . In particular embodiments, the fillet  36  can have a length L that is about one to two times the cross-sectional diameter D of the support hoop  20 .  
         [0035]     The intravascular filter  10  can be built to any suitable dimensions. In some embodiments, the support hoop  20  can have a cross-sectional diameter D that is in the range of about 0.001″ to about 0.010″. In some embodiments, the filter membrane  12  can have a thickness T that is in the range of about 0.0004″ to about 0.003″. In such embodiments, the fillet  36  can have an overall thickness W that is in the range of about 0.002″ to about 0.016″ (equal to D+2T) and a length L that is in the range of about 0.001″ to about 0.004″ (1D to 4D) and in particular embodiments a length L that is in the range of about 0.010″ to about 0.040″ (1D to 2D).  
         [0036]     The fillet  36  can be configured with any suitable shape or profile, provided that the shape or profile provides for relatively smooth blood flow between a region  42  that is upstream of the intravascular filter  10  and the open mouth end  16  of the intravascular filter  10 . In some embodiments, providing for relatively smooth blood flow in this region can reduce or eliminate the formation or collection of emboli that could otherwise form or collect just upstream of the contact point  34 . As shown, the fillet  36  tapers linearly from the distal position  38  to the proximal position  40 . In other embodiments, the fillet  36  can taper in a concave or convex configuration between the distal position  38  and the proximal portion  40 .  
         [0037]     The filter membrane  12  can be formed in any suitable manner. In some embodiments, the filter membrane  12  can be formed using spray molding in which an appropriately shaped mandrel is provided. A number of layers of polymeric material are sprayed onto the mandrel to form the filter membrane. After several layers of polymeric material are sprayed onto the mandrel, the support loop  20  can be positioned over the mandrel, and additional polymeric layers can be sprayed onto the mandrel. In some embodiments, the fillet  36  can be formed by positioning the support loop  20  an appropriate distance distally of the proximal end of the sprayed polymeric layers. As a result, the support loop  20  is encapsulated within the filter membrane  12 .  
         [0038]     In some embodiments, the tapered profile of the fillet  36  can be created by masking during the spray molding process. In some embodiments, the tapered profile of the fillet  36  can be formed in a post-spraying grinding or milling process.  
         [0039]     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.