Abstract:
A bifurcated stent comprises a body portion, a first branch portion, a second branch portion, a first pivot portion and a second pivot portion constructed from a common continuous sheet of stent material. The body portion, first branch portion and second branch portion provided with a substantially tubular shape, the tubular shape of each defines a lumen respectively therethrough. The lumen defined by the body portion is in fluid communication with the lumen defined by the first branch portion and the second branch portion. The first branch portion is pivotally engaged to an end of the body portion by the first pivot portion. The second branch portion is pivotally engaged to an end of the body portion by the second pivot portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not Applicable  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
         [0002]    Not Applicable  
         BACKGROUND OF THE INVENTION  
         [0003]    Stents, grafts, stent-grafts, vena cava filters and similar implantable medical devices, collectively referred to hereinafter as stents, are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents may be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, etc. Stents may be used to reinforce body vessels and to prevent restenosis following angioplasty in the vascular system. They may be self-expanding or expanded by an internal radial force, such as when mounted on a balloon.  
           [0004]    Stents are generally tubular devices for insertion into body lumens. Balloon expandable stents require mounting over a balloon, positioning, and inflation of the balloon to expand the stent radially outward. Self-expanding stents expand into place when unconstrained, without requiring assistance from a balloon. A self-expanding stent is biased so as to expand upon release from the delivery catheter. Some stents may be characterized as hybrid stents which have some characteristics of both self-expandable and balloon expandable stents.  
           [0005]    Stents may be constructed from a variety of materials such as stainless steel, Elgiloy, nitinol, shape memory polymers, etc. Stents may also be formed in a variety of manners as well. For example a stent may be formed by etching or cutting the stent pattern from a tube or section of stent material; a sheet of stent material maybe cut or etched according to a desired stent pattern whereupon the sheet may be rolled or otherwise formed into the desired tubular or bifurcated tubular shape of the stent; one or more wires or ribbons of stent material may be braided or otherwise formed into a desired shape and pattern.  
           [0006]    A stent may be used to provide a prosthetic intraluminal wall e.g. in the case of a stenosis to provide an unobstructed conduit for blood in the area of the stenosis. An endoluminal prosthesis comprises a stent which carries a prosthetic graft layer of fabric and is used e.g. to treat an aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of embolism, or of the natural artery wall bursting. Typically, a stent or endoluminal prosthesis is implanted in a blood vessel at the site of a stenosis or aneurysm by so-called “minimally invasive techniques” in which the stent is compressed radially inwards and is delivered by a catheter to the site where it is required through the patient&#39;s skin or by a “cut down” technique in which the blood vessel concerned is exposed by minor surgical means. When the stent is positioned at the correct location, the catheter is withdrawn and the stent is caused or allowed to re-expand to a predetermined diameter in the vessel.  
           [0007]    Within the vasculature however it is not uncommon for stenoses to form at any of a wide variety of vessel bifurcations. A bifurcation is an area of the vasculature or other portion of the body where a first (or parent) vessel is bifurcated into two or more branch vessels. Bifurcations exist within the body in a wide variety of configurations, angles, and vessel diameters. Where a stenotic lesion or lesions form at such a bifurcation, the lesion(s) can affect only one of the vessels (i.e., either of the branch vessels or the parent vessel) two of the vessels, or all three vessels.  
           [0008]    Unfortunately however, many prior art stents are not wholly satisfactory for use where the site of desired application of the stent is juxtaposed or extends across a bifurcation, particularly the carina of the bifurcation. Many current stent designs are unsuited for directing blood flow around and/or away from an aneurism located at or adjacent to the carina of a bifurcation. Moreover, many of the currently available stent designs are incapable of being implanted into various configurations and sizes of bifurcations within a body without out extensive pre-implantation modification, if at all.  
           [0009]    Thus, there remains a need for a bifurcated stent that may be utilized in a wide variety of vessel bifurcations, without requiring that the stent be extensively modified prior to implantation, and to provide a stent that is capable of fully supporting the carina of a vessel bifurcation while still being capable of deflecting blood from a lesion located at or around the carina and/or diverting blood around the carina.  
           [0010]    All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.  
           [0011]    Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.  
           [0012]    A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.  
         BRIEF SUMMARY OF THE INVENTION  
         [0013]    The present invention includes many different embodiments. For example in at least one embodiment, the invention is directed to a bifurcated stent constructed from a sheet of suitable material and formed into three main sections, wherein two of the sections, or branches, are pivotally engaged to the third section, or body, of the stent.  
           [0014]    In some embodiments the stent, one or more individual stent sections or one or more portions thereof may be balloon expandable, self-expandable, or hybrid expandable.  
           [0015]    In at least one embodiment the stent is constructed from at least one sheet of nickel, titanium, nickel-titanium alloys such as nitinol, stainless steel and alloys thereof, tantalum, or other suitable material. The at least one sheet is etched, cut or otherwise provided with a suitable stent pattern of interconnected strut members.  
           [0016]    In some embodiments the individual sections of the stent are each formed by rolling or joining two opposing sides of a respective section of the sheet into a substantially tubular form. The substantially tubular shape of each section may be retained together by engaging the opposing side of the sheet along a joining seam. The opposing sides may be joined by chemical or physical adhesion, welding, through the use of external ties, or fasteners, or by any type of engagement mechanism desired. In some embodiments the opposing sides of the sheet section are at least partially overlapped and remain free to move relative to one another. Whether the sections are joined at a seam or are free to move relative to one another, the individual sections of the stent may be independently expandable between at least an unexpanded state, an expanded state and/or one or more diameters therebetween.  
           [0017]    In some embodiments, each branch of the stent is engaged to the body at a pivot connection. The pivot connection between each branch portion of the stent and the body portion of the stent comprises at least one strut member. In at least one embodiment the pivotal connections are each defined by a portion of the sheet which has a circumferential length less than that of either branch or the body portion of the stent. The pivot connections provide a pivot point between each branch and the stent body to allow the stent to accommodate a variety of bifurcation angles and configurations.  
           [0018]    In some embodiments the design or pattern of struts provided to the walls of each branch of the stent (via the etching or cutting of the sheet from which the stent sections are formed) is varied in density to provide one or more regions which are less porous, have a greater concentration of struts or stent material and/or define holes that are fewer in number and/or smaller than adjacent portions of the stent section. This “denser region” is constructed and arranged to overlay a lesion located at or around the carina of the bifurcation. The denser region of the sections may be configured to prevent or reduce blood from reaching the lesion site so that blood passing through the stent branches is directed around the bifurcation.  
           [0019]    In some embodiments one or more of the branches may be provided with one or more aneurysm flaps on the external surface of the branch which is to be immediately adjacent to the carina and/or inside surface of the vessel bifurcation. The flaps are constructed and arranged to divert blood flow away from and around the aneurysm or lesion site.  
           [0020]    These and other embodiments which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference should be made to the drawings which form a further part hereof and the accompanying descriptive matter, in which there is illustrated and described embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0021]    A detailed description of the invention is hereafter described with specific reference being made to the drawings.  
         [0022]    [0022]FIG. 1 is a cross-sectional longitudinal side view of an embodiment of the invention positioned at a bifurcation of vessels.  
         [0023]    [0023]FIG. 2 is a perspective view of the embodiment of FIG. 1.  
         [0024]    [0024]FIG. 3 is a top down view of a sheet for use in constructing the embodiment of FIG. 2.  
         [0025]    [0025]FIG. 4 is a cross-sectional view of a portion of the sheet shown in FIG. 3 formed into a tubular section of the stent of FIG. 2 wherein the opposing sides of the sheet portion are overlappingly engaged.  
         [0026]    [0026]FIG. 5 is a cross-sectional view of a portion of the sheet shown in FIG. 3 formed into a tubular section of the stent of FIG. 2 wherein the opposing sides of the sheet portion are engaged along a seam.  
         [0027]    [0027]FIG. 6 is a partial side view of an embodiment wherein at least a portion of the sheet for constructing a bifurcated stent defines a pattern of at least two different densities of stent material.  
         [0028]    [0028]FIG. 7 is a perspective view of the embodiment of FIG. 1 wherein the stent is equipped with aneurysm flaps.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    As indicated above the present invention includes many different embodiments. In some embodiments the invention is directed to various designs of bifurcated stents and their methods of manufacture and use.  
         [0030]    In at least one embodiment, the invention is directed to a bifurcated stent, indicated generally at  10  in FIGS. 1 and 2, having three main sections, wherein two of the sections, or branches  12  and  14 , are pivotally engaged to the third section, or body  16 , of the stent  10 .  
         [0031]    In use, stent  10  may be advanced to a bifurcation  20  of vessels  22  by any delivery mechanism or device known such as one or more stent delivery catheters (not shown) that may be capable if independently positioning each of the branches  12  and  14  as well as the body  16  within one or more vessels  22 , such as is shown in FIG. 1. The stent  10  or one or more portions of one or more of the sections  12 ,  14  and  16  may be balloon expandable, self-expandable, and/or hybrid expandable as desired.  
         [0032]    As is discussed in greater detail below, the branches  12  and  14  are flexibly or pivotally engaged to the body  16  at one or more pivot connections  28 . As indicated by arrows  30  in FIG. 2, the individual branches  12  and  14  may be pivotally positioned relative to body  16 , to form an angle  32  with the body of about 0 degrees to about 180 degrees. In some embodiments the branches may be pivoted to form angles with the body  16  of about 0 to about 90 degrees. By providing the stent  10  with pivot connections  28 , the branches  12  and  14  may be positioned into a wide variety of bifurcation configurations that may be found with a human or mammalian anatomy.  
         [0033]    As illustrated in FIG. 1, once the stent  10  is advanced to the bifurcation  20 , the branches  12  and  14  are each positioned for deployment so as to extend from the main vessel  22   a  and into one of the side vessels  22   b  or  22   c  respectively. The flexible connection between the body  16  and each branch  12  and  14  allows each branch to be positioned into the respective side vessel regardless of the angle that the side vessel  22   b  and  22   c  forms with the main vessel  22   a . In at least one embodiment, the branches  12  and  14  are configured to at least partially surround a lesion  26  located at or around the carina  24  of the bifurcation  20 . If desired the stent may be positioned such that the branches  12  and  14  are immediately engaged to the carina  24  or lesion  26  positioned thereon or adjacent thereto.  
         [0034]    In at least one embodiment, an example of which is illustrated in FIG. 3, the stent  10  of FIGS. 1 and 2 is constructed from at least one sheet  40  of nickel, titanium, nickel-titanium alloys such as nitinol, stainless steel and alloys thereof, tantalum, or other suitable material for constructing a stent. If desired one or more portions of the stent may be made more or less radiopaque depending on the material from which the stent  10  is constructed. In some embodiments the stent  10  comprises one or more radiopaque markers or marker bands.  
         [0035]    The at least one sheet  40  is etched, cut or otherwise provided with a suitable stent pattern  42  of interconnected strut members  44 .  
         [0036]    In at least one embodiment the individual sections  12 ,  14  and/or  16  of the stent  10  are formed by rolling or joining two opposing sides  46  and  48  of a respective section  12 ,  14  and/or  16  of the sheet  40  into a substantially tubular form such as illustrated in FIGS. 4 and 5. In the embodiment shown in FIG. 5, the substantially tubular shape of each section  12 ,  14  and/or  16  may be retained by engaging the opposing side  46  and  48  of the sheet  40  together along a joining seam  50 . The seam  50  may comprise a chemical or physical adhesive, weld, one or more external ties or fasteners, or any type of engagement mechanism desired.  
         [0037]    Alternatively, in the embodiment shown in FIG. 4 the opposing sides  46  and  48  of the sheet  40  of the desired section  12 ,  14  and/or  16  are at least partially overlapped or coiled but remain free to move and expand relative to one another.  
         [0038]    Whether the sections  12 ,  14  and/or  16  of the resulting stent  10 , such as is shown FIG. 2 are joined at a seam  50 , as shown in FIG. 5, or are free to move relative to one another, as shown in FIG. 4, the individual sections  12 ,  14  and/or  16  of the stent  10  may be independently expandable between at least an unexpanded state, an expanded state and/or one or more diameters therebetween by any manner such as is known in the art.  
         [0039]    In the stent  10  shown in FIG. 2, the pivot connection  28  between each branch portion  12  and  14  of the stent  10  and the body portion  16  of the stent  10  comprises at least one strut member  44  of the sheet  40  shown in FIG. 3. In some embodiments however, a pivot connection  28  may be comprised of a connector portion  52  of the sheet  40  which extends between the body  16  and the respective branch  12  and  14  and defines a planar or circumferential length  54  less than that of any of the sections  12 ,  14 , and  16  of the sheet  40 .  
         [0040]    In some embodiments the design or pattern  42  of struts  44  provided to the sections  12 ,  14  and/or  16  of the stent  10  by the etching, cutting or other processing of the sheet  40  shown in FIG. 3 is varied in density to provide one or more regions  56  which are less porous, have a greater concentration of struts  44  or stent material and/or define holes  58  that are fewer in number and/or smaller than adjacent portions of the respective stent section, such as in the manner shown in FIG. 6. Such “denser regions”  56  are constructed and arranged to overlay or be positioned against the lesion  26  located at or around the carina  24  of the bifurcation  20 , as shown in FIG. 1. The denser region  56  of the branch sections  12  and  14  are configured to prevent or reduce blood flow, indicated by arrows  60  and  61 , from reaching the lesion  26  so that the blood passing through the stent sections  12 ,  14  and  16  is directed around the bifurcation  20 .  
         [0041]    In some embodiments, an example of which is illustrated in FIG. 7, one or more of the branches  12  an  14  may be provided with one or more aneurysm flaps  62  on the external surface of the branch  12  and/or  14  which is to be immediately adjacent to the carina  24  and/or inside surface  64  of the vessel branches  22   b  and  22   c . The flaps  62  are constructed and arranged to overlap one another to close the lumens  66  and  68  defined by each branch  12  and  14 , respectively, from the aneurysm or lesion site  26 . In order to provide the flaps  62  with the ability to overlappingly engage one another, the flaps  62 , or a portion thereof may be constructed from a shape-memory material which, when allowed to transition to a memorized shape upon implantation of the stent  10 , causes the flaps  62  to bend toward and/or around the carina  24  of the bifurcation  20 .  
         [0042]    In some embodiments the flaps  62  may be characterized as pivot connections  28 , such as have been previously described, but which are engaged only to branches  12  and  14 , respectively, and are not engaged to the body  16 . The flaps  62  are moveable or pivotable between an open position wherein blood or other fluid is free to access the lesion  26  and a closed position shown wherein the flow of blood  60  and  61  is diverted around the lesion  26 .  
         [0043]    The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.  
         [0044]    Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim  1  should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.  
         [0045]    This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.