Abstract:
A vascular prosthesis is described, having blunted wire ends. The blunted wire ends can take on a variety of configurations including end caps, bent ends, curved ends, or eyelets. The novel ends provide a smooth surface to contact the blood vessel walls thereby reducing the risk of trauma during placement of the prosthesis.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Application Ser. No. 62/220,895 filed Sep. 18, 2015 entitled Vessel Prosthesis, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Vascular prostheses such as stents and/or stent-grafts are used for a variety of reasons in the vasculature. For example, they can be used to prop open blood vessels, treat plaque buildup, replace a portion of a blood vessel, divert blood flow away from a target area, provide a scaffold or lumen for the introduction of other medical devices, or for various other reasons. 
         [0003]    It is desirable for these devices to have significant strength and to be able to effectively anchor within a blood vessel in order to remain expanded and to prevent migration from a target area after deployment. These devices must also be track-able through a delivery device (i.e. a catheter) without too much friction so that they can be delivered to a target site. Finally, these devices must also have some flexibility in order to conform to the shape of the vessel and mimic the natural movement of the vessels. 
         [0004]    Stents, stent-grafts, or other vascular prostheses are sometimes formed of one or more wires that are braided into a tubular structure. When these devices are braided by hand, the wire can be braided so as to terminate along the length of the stent instead of at the stent&#39;s proximal or distal ends. As a result, the hand-braided stent&#39;s ends may be relatively smooth. However, when a stent is machine-braided, its wires must typically be cut at its distal and proximal ends, creating relatively rough/sharp stent ends. Whether hand-braided or machine-braided, sharp stent ends can cause damage to the vessels as it is deployed and therefore is undesirable. 
       SUMMARY OF THE INVENTION 
       [0005]    One aspect of the present invention is directed to techniques and embodiments that reduce or eliminate any relatively sharp or rough edges created from wire ends of a braided stent. For example, the wire ends of a stent can be terminated in an end cap or by bending and welding the stent&#39;s wires. 
         [0006]    In another aspect of the present invention, a device, in particular a vascular prosthesis, in particular a stent and/or stent-graft is described. The device is comprised of one or more layers. In one embodiment, the device is comprised of metallic wires. In one embodiment, the device is comprised of two layers—an inner and an outer layer. In one embodiment, the device is comprised of two layers, where each layer is comprised of metallic wires. 
         [0007]    The device can utilize a tie component to bind the multiple layers together. In one embodiment the tie component is comprised of one or more wires. In one embodiment the tie component is comprised of one or more radiopaque wires. The tie component can be woven in an over-under pattern relative to the multiple layers of the device. 
         [0008]    In one embodiment, the device is comprised of an inner and outer layer. The outer layer has proximal and distal end loops or flares. The flares are comprised of wire pairs which combine to form the flares. In one embodiment, a flare cap is used to secure the wire pairs. In one embodiment, some of the flares are short and some of the flares are long. In one embodiment, the outer layer utilizes proximal and distal short and long flares. In one embodiment, the tie component generally follows the path of some of the wire(s) which comprise the flares. 
         [0009]    In one embodiment, the device is comprised of an inner and outer layer. Both layers are comprised of wires. In one embodiment, the wires comprising the outer layer have eyelets and pairs of these eyelet-comprising wires mate with each other. 
         [0010]    A method of making a device, in particular a stent and/or stent-graft, is described. In one embodiment, the device is wound over a mandrel with a compressed middle section and an expanded proximal and distal section. The expanded proximal and distal sections help create the flares and comprise channels to facilitate passage of the wires comprising the device. The wires can be cut at select locations to create the flares, and the wire pairs comprising the flares are bound with flare caps. 
         [0011]    A method of using a device, in particular a prosthesis, in particular a stent and/or stent-graft is described. In one embodiment, the prosthesis is used to treat atherosclerosis where the prosthesis is used in a blood vessel to keep the blood vessel open to maintain blood flow. In one embodiment, the prosthesis is used to treat superficial femoral artery disease where the prosthesis is placed within the superficial femoral artery and/or popliteal artery 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which 
           [0013]      FIG. 1  illustrates an embodiment of a stent according to the present invention. 
           [0014]      FIGS. 2-3  illustrate views of an outer layer of the stent from  FIG. 1 . 
           [0015]      FIGS. 4-5  illustrate a technique of creating end caps for the wires of the stent from  FIG. 1 . 
           [0016]      FIGS. 6-9  illustrate various alternate embodiments of blunted wire ends from a stent. 
           [0017]      FIGS. 10-12  illustrate a mandrel for winding a stent or stent layer. 
           [0018]      FIG. 13  illustrates an alternate embodiment of a mandrel end having grooves. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0019]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0020]    Stents, stent-grafts, or other vascular prostheses (herein referred to as stents for simplicity) are sometimes formed of one or more wires that are braided into a tubular structure. When these devices are braided by hand, the wire can be braided so as to terminate along the length of the stent instead of at the stent&#39;s proximal or distal ends. As a result, the hand-braided stent&#39;s ends may be relatively smooth. However, when a stent is machine-braided, its wires must typically be cut at its distal and proximal ends, creating relatively rough/sharp stent ends. Whether hand-braided or machine-braided, sharp stent ends can cause damage to the vessels as it is deployed and therefore is undesirable. 
         [0021]    One aspect of the present invention is directed to techniques and embodiments that reduce or eliminate any relatively sharp or rough edges created from wire ends of a braided stent. 
         [0022]      FIGS. 1-3  illustrate a braided stent  100  having distal and/or proximal ends that are rounded or blunted. Specifically, the braided stent has an outer layer  102  woven from a plurality of wires  104  that terminate with triangular or pointed loops  110 . Each triangular loop  110  is preferably formed from two wires  104  that contact each other at their ends and terminate in a single end cap  112 . These end caps  112  allow the ends to move freely without the complications of sharp or rough edges that would otherwise be present. These end caps  112  can also be used as a part of a delivery device to help hold and/or retrieve the stent  100  prior to full deployment where the delivery system grips the caps  112  to secure the stent  100  to the delivery system, and allow for greater retractability as described in co-pending U.S. patent application Ser. No. 15/268,271, which is incorporated by reference in its entirety. 
         [0023]      FIGS. 4 and 5  illustrate one technique of creating these triangular loops  110  and end caps  112 . First, two of the wires  104  at one end of the stent  100  are moved against each other and a crimp  114  is slid or moved over the wires  104  to a desired location. The crimp  114  can be a tube or a “C” shaped structure and is preferably composed of a material suitable for welding, such as Nitinol. The crimp  114  may be further crimped or compressed around the two wires  104  after placements to help maintain its position. If the ends of the two wires  104  are not in close proximity to the top of the crimp  114 , the wires  104  can be trimmed to such a level. Finally, location  116  is welded (e.g., laser welded), melting the ends of the wires  104  and the crimp  114  together until a shape resembling a rounded ball or cap results (i.e., end cap  112 ). 
         [0024]    While the crimp  114  is illustrated as a tube, in an alternate embodiment it can be configured as a cap member (e.g. metallic materials such as Nitinol, or radiopaque materials such as tantalum) having an inner spaced sized for two wires  104  and a closed end. With such a cap, the wires  104  can be trimmed to a desired length, moved together, and the cap can be placed over and welded onto the wires  104 . In such a configuration, the wires can either contact each other at or near the cap location or even be separated entirely—depending on the size of the cap. 
         [0025]      FIG. 6  illustrates an alternate technique for creating a stent  100  with blunted or smooth ends, having an end cap  122 , but without a crimp  114 . Symmetrical bends at locations  104 C are created with the two wires  104 . If necessary, the wires  104  are trimmed closely to the bend location  104 C and the ends of the wires  104  near the bends  104 C are welded (e.g., laser welded) at one or more weld locations  116  (e.g., three weld locations) until the wire ends resemble a rounded cap shape. 
         [0026]      FIG. 7  illustrates another alternate technique for creating a stent  100  with blunted or smooth ends, creating a curved or bent end  118 . One wire  104 A is trimmed to a length that is longer than the wire  104 B it is to be joined to (e.g., between 1 mm to 10 mm longer). The longer wire  104 A is bent at location  104 C to an angle that is preferably between, for example, about 90 and about 160 degrees so that the ends of the two wires  104 A and  104 B overlap when moved in proximity to each other. Finally, one or more welds are created at locations  116  (e.g., three welds). 
         [0027]      FIG. 8  illustrates yet another alternate technique for creating a stent  100  with blunted or smooth ends, creating a rounded curve  120 . A curved or rounded segment  104 D is created at the ends of both wires  104  that are to be joined together. These curved segments  104 D are moved together and welds are created near the ends of each wire  104  at locations  116 . For example, the weld locations  116  can be located between the very end of one wire  104  and a location spaced apart from the end of the other wire  104 , creating two or more weld locations  116  (e.g., 4 total weld locations  116  per rounded curve  120 ). 
         [0028]      FIG. 9  illustrates yet another alternative embodiment for creating a stent  100  with blunted or smooth ends involving the use of eyelets  132 . Specifically, the wires  104  comprising the outer layer of the stent  100  would utilize a wire with eyelets  132  on both the proximal and distal ends of the wires  104 . The eyelets  132  may be formed by pulling the wire  104  back onto itself and welding the wire at location  134 . The eyelet  132  of one wire end is first created. The second wire is then inserted into the eyelet  132  of the first wire end, and the second wire is then welded at location  134  to create the second eyelet  132  to connect the eyelets  132 . The eyelets  132  allow the wires  104  to be free to move relative to each other around the eyelet region. Thus, this configuration offers some advantages in terms of flexibility of the stent  100 . 
         [0029]    Returning to  FIG. 1 , the stent  100  is shown as comprising two layers, an inner layer  106  and an outer layer  104  (although alternative embodiments may only have a single layer). In one embodiment, both layers are comprised of metallic wires or ribbons, such as nitinol wires. The inner layer  106  is preferably comprised of 36-60 braided wires (48 wires). The diameter of the wire  108  of the inner layer  106  can range from about 0.001″ to about 0.003″, such as about 0.0016″ to about 0.002″. The outer layer  102  is also preferably comprised of 6-24 braided or woven wires  104 , such as 12 wires. The wire  104  of the outer layer  102  preferably has a diameter between about 0.004″ to about 0.008″, and more preferably between about 0.0055″ to about 0.007″. 
         [0030]    The wires  104 ,  108  are preferably comprised of a metallic material such as nitinol, a radiopaque material, can be coated with radiopaque material, or can have a radiopaque core. Other materials such as cobalt-chromium or stainless steel may also be used. 
         [0031]    As shown in the  FIG. 1 , the outer layer  102  is located axially outward relative to the inner layer  106 . In one embodiment, the inner layer  106  is formed of a braided mesh structure with a tubular shape that is longer than the outer layer  102  and where the mesh of the inner layer  106  is cut at either or both ends. 
         [0032]    In one embodiment, the outer layer  102  is comprised of a braided mesh of 12 wires  104  and the terminal ends (i.e. at the proximal and distal ends) of the wires  104  comprising the outer layer terminates into 6 flares or triangular loops  110 . The loops  110  may all be about the same length or can vary in length. For example, the loops  110  may alternate between relatively longer loops  110  and relatively shorter loops  110 , which may improve tracking through a catheter by distributing contact points to various places around the inner periphery of the catheter instead of concentrating the contact points to a few particular sections. In other words, the areas of high friction are decentralized, which improves pushing through the catheter or delivery device. 
         [0033]    In other example embodiments, the outer layer  102  may be comprised of 8 wires and 4 triangular loops  110  at both ends or may be comprised of 16 wires with 8 triangular loops  110 . The outer layer  102  and inner layer  106  may also be connected via a number of different tie mechanism, such as one or more woven wires or wire coils. Additional details of the tie components, inner/outer layers, and other aspects of the stent  100  can be found in U.S. Pub. No. 20130245745, the contents of which are hereby incorporated herein by reference. In one embodiment, the tie component is comprised of one or more wire that are weaved under the inner layer and over the outer layer of the prosthesis to bind the layers together. Alternative approaches, such as marker coils wrapped in selective locations around both the inner and outer layers, can be used in place of, or in addition to, the woven wire(s). In one embodiment, the tie component is comprised of a tantalum wire woven through the inner and outer layers of the prosthesis. In one embodiment, the tie component is comprised of a tantalum wire which follows the path of one of the wires which comprise the outer layer. Using a radiopaque material for the tie component, such as tantalum, enhances imaging of the device. Other radiopaque materials such as palladium, platinum, or gold may also be used. Non-radiopaque materials can also be used, for example a nitinol, cobalt-chromium, or stainless steel wire can be used for the tie component. Alternatively, the tie component can utilize a radiopaque core with a non-radiopaque cover or a radiopaque cover with a non-radiopaque core. Multiple tie components may also be used, where some tie components are radiopaque and some tie components are non-radiopaque. The tie component is woven in an over-under pattern with the inner and outer layer of the prosthesis to bind the layers together. The tie component can continue in this over-under pattern through the length of the prosthesis to bind the layers together. Additionally, since the tie component is preferentially made of a radiopaque material (i.e. tantalum, or other materials such as platinum, palladium, gold, etc.), the imaging of the device is augmented during delivery and placement of the prosthesis. 
         [0034]    The actual over-under pattern can be customized depending on the properties of the prosthesis. A tighter crossing density pattern (i.e. one over followed by one under, followed by one over followed by one under, etc.) would tightly bind the inner and outer layers together and produce a stiffer prosthesis. A looser crossing density pattern (i.e. one under followed by an over pattern over several cells) would loosely bind the inner and outer layers together and produce a more flexible prosthesis. 
         [0035]      FIGS. 10-13  illustrate tools and techniques for braiding one layer of the stent  100  (e.g., outer layer  102 ). The outer stent layer  102  is wound over mandrel  140 , which has a smaller diameter middle region  140 B and larger diameter ends  140 A. The wires  104  are first placed in the longitudinal grooves  144  on one of the larger diameter ends  140 . Preferably, two wires  104  are placed into each channel or groove  144  and these wire pairs are later used to later create the triangular loops  110 . The wires  104  are maintained in the grooves  144  by screws  142  that screw into the larger diameter ends  140 A and partially overlap on the grooves  144 , thereby acting as a clamp mechanism. Once all of the desired wires  104  are clamped in the grooves  104 , the outer stent layer  102  is braided over the smaller middle diameter  140 B. This braiding can be achieved by hand or with braiding machine. Once the braiding is complete, the wires  104  can be clamped with screws  142  in the grooves  144  on the opposite side of the mandrel  140 . 
         [0036]    As seen in  FIG. 11 , tubing  146  can be placed over each pair of wires  104  to help create the location at which they come together and thereby the size of the resulting triangular loop  110 . The wires can then be connected via any of the previously described techniques in this specification. For example,  FIGS. 11 and 12  illustrate tubes  146  placed at longitudinally alternating positions which allows for the creation of loops  110  that alternate in size (e.g., larger, smaller, larger, smaller, etc.). 
         [0037]    Once the desired size of the loops  110  is determined by the tube  146  location, the outer stent layer  102  is then heat set to maintain this braided configuration and size. Further electro-polishing and other manufacturing may be done as well. The outer stent layer  102  is then removed from the mandrel  140 , the tubing  146  is then removed and the two wires  104  are connected via one of the previously described loop-creation techniques. 
         [0038]      FIG. 13  shows an alternative configuration for the larger enlarged ends  104 A, different from what is shown in  FIGS. 10-12 . In this configuration, the grooves  144  are located on a radially tapered face portion of the enlarged end, and the screw  142  (only the recess accommodating the screw is shown, but the screw  142  screws into this recess) is also on the tapered face to lock the wires  104  within the groove  144 . 
         [0039]    The inner layer  106  of the stent  100  may also be wound on a mandrel  140  having a substantially consistent diameter throughout, since the inner layer  106  has a substantially consistent diameter. The inner layer  106  is then heat set and optionally electro-polished to remove any surface irregularities. The inner layer  106  can then be placed within the outer layer and the tie component can be wound through both layers  102 ,  106  to bind the layers together. 
         [0040]    The heat treatment sets the shape memory to the stent  100 . In one embodiment, the stent  100  is self-expandable and has an expanded shape shape-memory. The stent  100  adopts a collapsed configuration during delivery through a delivery device (i.e. a catheter) and radially expands upon release. Though the stent  100  is self-expandable, balloons may also be used to open the stent  100 . 
         [0041]    The stent  100  described in the various embodiments, in one example, may have an overall size of about 4 millimeters to about 8 millimeters outer diameter, and a length of about 40 millimeters to about 150 millimeters. 
         [0042]    The stent  100  is primarily described as utilizing metallic (i.e. nitinol) wires, however, other materials may be used such as stainless steel, cobalt-chromium, polymers, nitinol, and/or combinations therein may be used. Radiopaque materials such as gold, palladium, tantalum, and/or platinum may also be used, or may be used in combination with the materials described above. 
         [0043]    The stent  100  embodiments described can be stents and/or stent-grafts used for a variety of reasons discussed earlier, such as flow diversion, propping open a vessel, treating a calcified vessel, as a scaffold use to contain additional medical devices, or similar uses. The embodiments may also be used in a variety of blood vessels sizes and locations, such as within the smaller vessels of the neuro-vasculature or within the larger vessels of the peripheral vasculature. The device can be sized appropriately based on need. 
         [0044]    In one embodiment, the stent  100  is used to treat atherosclerotic disease, where blood vessels become calcified and must be propped open. The stent  100  helps open the blood vessel and acts as a conduit for blood flow. 
         [0045]    In one embodiment, the stent  100  is used to treat superficial femoral artery disease. This is a disease state where arthrosclerosis, calcification, and/or plaque occurs in the peripheral vasculature, particularly in the superficial femoral artery and/or popliteal artery near the leg and knee region of the body. Please note though the terms arthrosclerosis, calcification, and plaque may technically refer to different things, they are being used synonymously here to refer generally to the build-up of unwanted or harmful matter within the blood vessel. The stent  100  may be considered a stent-graft since the prosthesis is used to mimic a portion of the vessel which is calcified. Since this artery is located near the knee, the vessels in this area flex considerably and are relatively long. A flexible stent-graft is necessary to track the movement of the vessel—however this must be combined with good anchor strength and high radial force so the prosthesis stays at the location and does not migrate. The flared ends help anchor the prosthesis in place, the inner and outer layers allow a strong scaffold to prop the blood vessel open, while the potential for a variable tie layer configuration (i.e. the over-under wound pattern described above) can customize the flexibility of the prosthesis. 
         [0046]    A method of use of a device of the preceding embodiments involves placing a balloon in a target region with arthrosclerosis, calcification, and/or plaque and inserting and expanding a balloon in order to compress the calcification toward the vessel wall and break up some of the looser sclerotic buildup. The balloon is then deflated and removed. The stent  100  is then delivered to the target site and expanded. The stent  100  creates a scaffold to constrain the further growth of the sclerotic material, plaque, and/or calcification, and provides a flow-path for blood thus restoring flow to the vessel. In one embodiment, the device could be used in the superficial femoral artery or the popliteal arteries in the leg. 
         [0047]    The mesh pattern of the inner layer  106  and outer layer  102  offer some advantages when used to treat plaque, calcification, and/or arthrosclerosis. Specifically, the outer layer  102  provides a strong scaffolding layer to contact the buildup, while the smaller mesh size of the inner layer  106  provides relatively small pores which sit radially inward of the outer layer  102 . These small pore sizes offer a few advantages. First, they limit the amount of plaque that can be serrated or sheared by the stent  100  during placement. While it may be desirable to break up some of the undesirable matter, this is primarily done by the balloon. The stent  100  primarily acts as a scaffold to restore blood flow to the region. Any additional matter which may be sheared off by the inner or outer layer  102 ,  106  will likely be caught by the small pores of the inner layer  106 , and there is therefore less chance of additional fragments shearing off and migrating downstream. Thus, the small pore sizes of the inner layer  106 , sitting under the outer layer  102 , provide another scaffolding layer to constrain additional growth of the plaque, sclerotic material, and/or calcification while allowing blood flow through the lumen of the prosthesis. 
         [0048]    During delivery through a catheter or delivery device, the frictional contact points are limited to the outer layer  102  mesh wires  104  and the flared end components, making deliverability easier than a covered textile prosthesis in which the frictional contact is continuous throughout the length of the prosthesis. Strong radial force is achieved through the use of the outer metallic mesh layer  102 , which may use larger diameter wires than the inner layer  106 . The end loops  110  may offer good anchoring and retention within the vessel, to prevent the stent  100  from migrating after placement. The stent  100  also offers some degree of flexibility since the stent  100  is comprised of multiple mesh layers linked together via a tie component. The flexibility of the prosthesis can be customized by controlling the wind technique (e.g. the over-under pattern) of the tie component. A tighter tie component wind pattern would create a stiffer stent  100  where the inner and outer layers  106 ,  102  have limited freedom to move relative to each other. A looser tie component wind pattern would create a more flexible stent  100  where the inner and outer layers  106 ,  102  have more freedom to move relative to each other. 
         [0049]    In one example, the inner layer pore size is between about 200 to about 500 micrometers. In one example, the outer layer pore size is between about 800 to about 1600 micrometers. The pore size is taken by inscribing a circle within the roughly diamond-shaped cell created by the wires comprising the respective layers. 
         [0050]    The figures used within the specification are meant to be illustrative in nature and not restricted to what is actually shown. Similarly, any descriptive items such as measurements, materials, etc. are used for illustrative purposes to help conceptually explain the various embodiments presented herein and are not meant to be limited to what is explicitly disclosed. 
         [0051]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.