(12) United States Patent
`Milo
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,206,911 B1
`Mar. 27, 2001
`
`USOO6206911B1
`
`(54) STENT COMBINATION
`
`(76) Inventor: Simcha Milo, 6a Noga Street, Haifa,
`33407 (IL)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U_S_C_ 154(k)) by() days
`
`(21) Appl. No.:
`(22) PCT Filed:
`
`09/180,092
`Nov. 17, 1997
`
`(86) PCT N0.:
`
`PCT/IB97/01574
`
`NOV‘ 2’ 1998
`§ 371 Date‘
`§ 102(e) Date; Nov, 2, 1998
`
`(87) PCT Pub. N0.: WO98/26732
`PCT Pub. Date: Jun. 25, 1998
`_
`_
`_ Related U-_S- Apphcatlon Data
`_
`(60) PTOVlSlOnal apphcanon N°~ 60/0347877 ?led on Dec' 19’
`1996'
`.............. .. A61F 2/06
`(51) Int. Cl.7 ..
`. 623/115; 623/117
`(52) US. Cl. ................ ..
`(58) Field of Search ............................... .. 623/1, 12, 1.15,
`623/117, 136; 606/194
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,667,523 * 9/1997 Bynon et a1. .................... .. 623/12X
`5,681,345 * 10/1997 Euteneuer ..... ..
`623/12X
`5,695,516 * 12/1997 Fischell et a1.
`606/194
`5,800,526 * 9/1998 Anderson et a1. ..
`623/1
`5,807,404 * 9/1998 Richter .............. ..
`623/1
`5,824,037 * 10/1998 Fogarty et al- --
`623/1
`5,843,164 * 12/1998 FfaIltZeIl et a1- -
`623/1
`5,871,535 * 2/1999 Wolff et a1. ..
`623/1
`5,931,867 * 8/1999 Haindl ............................ .. 606/151 X
`
`* Cited by examiner
`
`Primary Examiner—David H. Willse
`Assistant Examiner—Brian E. Pellegrino
`(74) Attorney, Agent, or Firm—Arnall Golden & Gregory,
`LLP
`
`ABSTRACT
`(57)
`Radially expandable intraluminal stents (11) suitable for
`providing interior support Within a human blood vessel are
`disclosed. Amaterial (33‘) used to construct the stent (11) is
`formed into diamond cells (35). The diamond cells (35) each
`have arms (37) of equal length. Diamond cells (35) are
`interconnected to ntherdiarnnnd Cells (25) by legs (39, 39a)
`or to Pairs of Smaller Cells (41) Which have a Common Vertex
`and four arms (43) of equal length. Needle-like prongs (51,
`53) are attached to the diamond cells (35) at their vertex to
`function as attachment means for a biological membrane
`57‘ .
`
`(
`
`)
`
`5,556,414 * 9/1996 Turi ................................... .. 623/111
`
`15 Claims, 3 Drawing Sheets
`
`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 1 of 9
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`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 2 of 9
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`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 3 of 9
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`

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`U.S. Patent
`
`Mar. 27, 2001
`
`Sheet 3 013
`
`US 6,206,911 B1
`
`FIG. 5
`19 13
`13
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`19
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`13
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`5;’ 5,5 FIG. 7
`53
`51 355
`55 53
`57 Q2
`W/ /7/////////V/////////7%
`$332
`'' '.\\\‘/((\\\
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`/
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`I
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`11
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`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 4 of 9
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`US 6,206,91 1 B1
`
`1
`STENT COMBINATION
`
`This application claims priority from US. provisional
`application Ser. No. 60/034,787, ?led Dec. 19, 1996. The
`disclosure of this application is incorporated herein by
`reference.
`This invention relates to vascular stents and the like and
`more particularly to intraluminal stents and to such stent and
`biomembrane combinations Which can be carried to a
`desired in vivo location and then expanded, as by use of a
`balloon catheter, into an operative con?guration. Reference
`is made to Disclosure Document No. 404,393 Which Was
`?led on Sep. 9, 1996.
`
`BACKGROUND OF THE INVENTION
`Expandable stents have noW proved to be extremely
`useful in treating occluded blood vessels and/or diseased
`blood vessels. Whereas there are numerous expandable
`stents that are noW commercially available, these stents
`invariably undergo a foreshortening in axial length as a
`result of their radial expansion. When treating a diseased
`blood vessel, and oftentimes When treating an occluded
`blood vessel, such as a coronary artery or other peripheral
`vessel, there is a desire to carry a tubular graft in surrounding
`relationship to the stent in order to deliver the graft With the
`stent to patch a diseased vascular location affected With
`lesions or the like. It is believed such grafts may prevent
`intimal cell proliferation caused by direct contact of a metal
`stent With the vessel Wall Which frequently otherWise results
`in early stent occlusion. Heretofore, truly acceptable tech
`niques have not been developed for carrying such grafts to
`a desired location in surrounding relationship to a stent on a
`balloon catheter or the like. Because such present commer
`cially available stents undergo axial foreshortening as a
`result of expansion, tubular grafts secured to the exterior of
`such a stent Would be likeWise subject to such foreshorten
`ing and Would undergo undesirable Wrinkling even if they
`Were slightly elastic.
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`SUMMARY OF THE PRESENT INVENTION
`The present invention provides multiple designs of
`expandable stents Which are created so as to undergo essen
`tially no axial foreshortening (or only minimal axial
`foreshortening) When expanded from an unexpanded or
`compressed con?guration to an operative con?guration.
`Moreover, tubular biological membranes can noW be effec
`tively interconnected With expandable stents of this charac
`ter and effectively located in surrounding, isolating relation
`ship to the stent. Interconnection may be via pairs of
`needle-like projections or prongs Which may be bent to have
`a radial orientation during the installation of such a tubular
`biomembrane upon the unexpanded stent and then bent in
`opposite directions back into the plane of the stent, prefer
`ably in opposite axially extending directions, to secure the
`tubular biomembrane in such a mating connection.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a plan vieW of an expanded form of stent
`material before it is rolled and Welded into a tubular stent
`and then appropriately crimped, Which material design is
`effective to create a particularly advantageous crimped stent.
`FIG. 2 is a vieW similar to FIG. 1 illustrating an alterna
`tive material design to that shoWn in FIG. 1 Which alterna
`tive employs pairs of small diamond cells.
`FIG. 3 shoWs a further alternative material design that
`constitutes a hybrid version of the tWo materials shoWn in
`FIGS. 1 and 2.
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`FIG. 4 is a vieW similar to FIG. 1 Which is another
`alternative material design similar to that shoWn in FIG. 3
`but Which incorporates needle-like projections that extend in
`opposite longitudinal directions and that are employed to
`mount a tubular biological membrane exterior of the stent.
`FIG. 5 is a fragmentary elevation vieW of the stent
`material illustrated in FIG. 1 shoWn in its crimped condition.
`FIG. 5A is a fragmentary elevation vieW of the stent
`material illustrated in FIG. 3 shoWn in its crimped condition.
`FIG. 6 is a perspective vieW of a tubular stent made from
`the material of FIG. 4 shoWn in its expanded con?guration.
`FIG. 7 is a fragmentary sectional vieW through a crimped
`tubular stent made from material shoWn in FIG. 4 With a
`tubular membrane mounted in place and in the process of
`being staked thereupon, With the radially outWardly bent
`needle-like prongs being shoWn as they are in various stages
`of being bent back toWard the plane of the stent.
`FIG. 8 is a sectional vieW similar to FIG. 7 shoWing an
`alternative method of joining a tubular membrane to a
`crimped stent by folding each end of the tubular stent back
`upon itself to securely sandWich the ends of the tubular
`membrane therebetWeen.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`The stents of the invention are provided With properties
`Which render them superior to commercially available
`expandable intraluminal stents. The stents illustrated herein
`not only experience substantially no shortening in axial
`length upon expansion but also demonstrate high lateral
`pliability, alloWing the stent to relatively easily folloW the
`curved features of a blood vessel or the like as it is being
`inserted on a balloon catheter or the like. Both of these
`objectives are achieved While at the same time providing
`good radial support, suf?cient to Withstand the tendency of
`a blood vessel that has been ballooned to recoil to a smaller
`diameter. Such radial support remains a characteristic even
`though the stent may have been radially expanded to
`increase its unexpanded or crimped diameter by a factor of
`about 2 to 4, eg from a crimped exterior diameter of about
`1.3—1.5 mm or even as loW as 1.1 mm.
`In addition, the stents of the invention can be advanta
`geously employed in combination With tubular, biological
`membranes, sometimes referred to as biomembranes, Which
`Will serve to separate the major portion of the metal material
`of the stent from the vascular Wall and thus obviate reoc
`clusion secondary to intimal cell proliferation. Biomem
`branes can also be valuable in repairing blood vessels in
`certain diseased states, as for example those Which are torn
`or have suffered the results of affection With different lesions
`or the like. Impregnation of the exterior surface and the
`interior surface of biomembranes With different pharmaceu
`ticals can be effectively used to differentially deliver medi
`cations. These stent biomembrane combinations can be
`carried to the desired location in a patient upon a balloon
`catheter and then expanded to just the desired diameter by
`the careful expansion of the balloon catheter. As a result,
`these stents have a substantial advantage in ?exibility of
`usage over self-expanding stents Which may inherently
`continue to expand past the desired diameter, resulting in
`their becoming undesirably deeply embedded in the vessel
`Wall. Because the stents of the present invention do not
`signi?cantly decrease in axial length upon expansion, they
`are perfectly suited for use in combination With biological
`membranes Which are pliable and slightly stretchable and
`elastic.
`
`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 5 of 9
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`US 6,206,91 1 B1
`
`3
`Illustrated in FIG. 1 is a generally rectangular piece or
`blank of malleable metal sheet 11 which represents an
`expanded framework of an approximate shape for being
`rolled, welded (or otherwise joined) and crimped to create a
`balloon-expandable stent. By malleable is meant a non
`brittle, pliable metal that can be bent to a different shape but
`which has sufficient stability so as to retain its expanded
`shape when subjected to the normal forces that may likely be
`encountered within the human body. The illustrated stent
`blank 11 is constructed with an open framework which
`includes a plurality of axially extending legs which have a
`Zig-Zag con?guration and which are formed by intercon
`nected leg segments 13. Each junction between adjacent legs
`in the framework is also the vertex of a diamond-shaped cell
`17. Each of the cells 17 is made up of four interconnected
`arms 19, and thus the cells 19 serve as spacers which
`uniformly space apart the adjacent, axially-extending, Zig
`Zag legs. Viewed from a different perspective, the open
`framework material has a construction in the form of side
`by-side axially extending rows of major diamond-shaped
`cells with the adjacent rows being staggered so as to inter?t
`and create a regular pattern. The result of such overlapping
`is that each of these major cells would include two spaced
`apart minor diamond cells 17 along with pairs of ?anking leg
`segments 13.
`The stent material may be made from ?at wire that is
`welded or suitably joined at the points of contact; however,
`it is preferably made by suitably machining a sheet of
`malleable metal, such as titanium, stainless steel or other
`suitable metal alloy material. Wire or sheets of a memory
`type nickel alloy, such as Nitinol, might also be used. Such
`could be shaped and then welded to create a tubular structure
`of desired diameter and length, and such a tubular structure
`might then be cooled below the temperature transformation
`level and suitably compressed before being loaded into a
`catheter.
`When a sheet of nonmemory malleable metal is used,
`suitable openings are formed in such a sheet by conventional
`laser-cutting techniques or by electrical discharge machining
`or the like. Such an open framework may alternatively be
`machined from a thin metal tube, seamless or welded,
`although more sophisticated equipment might be required to
`machine a tubular body. Thus, stents may be preferably
`made from a ?at sheet, as depicted in FIG. 1, which is
`subsequently rolled into a tubular con?guration (which
`would be about a horiZontal axis as oriented in FIG. 1) and
`then welded or otherwise appropriately fusion-bonded. For
`example, it may be made from a sheet of stainless steel
`having a thickness of about 0.08 mm to about 0.1 mm. The
`leg segments preferably have a width at least about 40%
`greater than the width of the arms of the cells. For example,
`the arms may have a width of about 0.05 mm, with the leg
`segments having a width of about 0.075 mm. The machined
`sheet would be ?nally polished as well known in this art.
`More speci?cally, each of the diamond-shaped cells 17
`has four arms 19 of preferably equal length which are
`connected to one another at their ends to form a diamond
`which, in the expanded con?guration, as illustrated in FIG.
`1, has four interior 90° angles. The aforementioned major
`diamond cells 17 of the overall repeating pattern are formed
`by two adjacent arms of each cell 17, together with two pairs
`of interconnected leg segments 13. Following rolling or
`otherwise forming into tubular con?guration, a spot-welding
`operation is carried out to connect the vertices A of each
`diamond cell 15 located along the top edge of the generally
`rectangularly-shaped piece of material 11 to the junction
`points between adjacent leg segments 13 that are located
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`along the bottom edge, ie at the locations marked B. This
`diamond-within-a-diamond pattern allows for compression
`or crimping of the framework to a smaller dimension, eg
`about one-half of the height shown in FIG. 1, without any
`substantial change in axial length.
`When the stent is machined from ?at metal stock, the
`tubular framework con?guration may ?rst be formed and
`then compressed to create a smaller diameter tubular struc
`ture. The leg segments 13 in the zigzag, axially extending
`legs are oriented so as to be at an angle to each other of
`between about 120° and 140° and preferably at an angle of
`between about 125° and 135°. In viewing the framework
`shown in FIG. 1, it can be seen that each leg segment 13 ends
`at a junction point where it is in connection with two arms
`19 of a diamond-shaped cell and the next adjoining leg
`segment 13. As a result, there is good stabiliZing support at
`these locations. At the other two vertices of each diamond
`cell 17 that are not at junctions between leg segments, there
`is no lateral support. As a result, when the open framework
`structure is subjected to crimping or compressing force, the
`diamond-shaped cells 17 collapse in a direction transverse to
`the axis, signi?cantly reducing the circumference of the
`tubular structure.
`FIG. 5 is a fragmentary view of a stent made from the
`material 11 shown in its compressed condition, where it can
`be seen that the triangular cells 17 have completely col
`lapsed. The arms 19 of the diamond cells 17 lie adjacent to
`each other in pairs. The Zig-Zag con?guration of the legs has
`now reversed, i.e. compared to the orientation in the
`expanded con?guration illustrated in FIG. 1, the orientation
`is the inverse of what it was. However, the leg segments 13
`are still oriented at about the same angle to each other. The
`collapsing of the diamond-shaped cells 17 has no effect upon
`the axial length of the tubular structure because they are
`isolated from the legs, and there is no signi?cant change in
`the axial length of the stent in its unexpanded and expanded
`con?gurations. However, a slight extension in length occurs
`during transition when the adjacent leg segments approach
`an angle of 180°.
`Illustrated in FIG. 2 is an alternative embodiment of a
`piece or blank of sheet material 23 similarly designed to be
`formed into an expandable intraluminal stent. The material
`also uses a type of general pattern of a diamond-in-a
`diamond; however, in this repeating pattern, axially extend
`ing legs that are formed by short leg segments 25, are spaced
`apart not by single minor diamond cells, but by pairs of
`diamond cells 27 having a common vertex. The material 23
`can likewise be made by machining from a single sheet.
`Alternatively, it could be formed from a plurality of indi
`vidual wire sections, each of which would ultimately run
`circumferentially of the tubular stent. As depicted in FIG. 2,
`if such lengths of wire were used, adjacent, vertically
`oriented, formed lengths of wire would be joined, as by
`spot-welding, at three points. As indicated hereinbefore, the
`framework material is preferably machined from a unitary
`sheet or tube, and to achieve more ef?cient use of material,
`the structure is machined in the unexpanded form which also
`eliminates the step of crimping or compressing.
`The open framework structure shown in FIG. 2 is such
`that each of the diamond cells of the interconnected pairs has
`a common vertex 31 and an opposite open vertex 32 which
`lies at what would otherwise be the junction between the
`ends of the adjacent leg segments 25. As a result, the leg
`segments 25, instead of being directly connected to one
`another at these junctions, are indirectly connected through
`the arms 29 of one of the diamond cells 27. Even though
`they are not directly interconnected, the leg segments 25 are
`
`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 6 of 9
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`US 6,206,91 1 B1
`
`5
`still oriented at an angle to each other between about 120°
`and about 140° as mentioned above. Following rolling of the
`material 23 or otherWise forming it into a tubular
`con?guration, spot Welding or the like is carried out so as to
`join the ends of the arms 29 at each open vertex along the
`upper edge of the sheet, at the points marked A, by spot
`Welding or the like, to the ends of the leg segments 25 at the
`points marked B.
`Illustrated in FIG. 3 is a further alternative embodiment of
`a piece or blank of sheet material 33, designed to be formed
`into an expandable intraluminal stent, having a structure
`Which is a hybrid of those shoWn in FIGS. 1 and 2. The
`material 33 uses alternating sections of the FIG. 1 material
`and the FIG. 2 material. In a center section and the tWo
`lateral edge sections, larger diamond cells 35 are formed,
`similar to the cells 17. Each of these diamond cells 35 has
`four arms 37 of equal length, and the upper and loWer
`vertices are located at junctions betWeen adjacent intercon
`nected leg segments or ribs 39. The tWo intermediate regions
`resemble the frameWork construction shoWn in FIG. 2. Pairs
`of smaller diamond cells 41 With a common vertex and four
`arms 43 of equal length indirectly interconnect leg segments
`39a at the locations of the open vertices.
`The blank 33 is used to form a stent as previously
`described by rolling or otherWise deforming it into a tubular
`form and then spot-Welding or the like at the aligned points
`betWeen the tWo common axially extending edges. After
`formation into such a tube, it is conventionally crimped as
`by being forced axially through a tubular passageWay of
`ever-decreasing diameter to effect such a smooth transition
`from the expanded, highly open frameWork to a fairly
`closely compressed cylindrical form, such as that depicted in
`the fragmentary vieW FIG. 5A. The arms 37 Which make up
`the larger diamond cells 35 lie generally adjacent one
`another in pairs. LikeWise, the arms 43 of the smaller
`diamond cells 41 are similarly compressed so as to lie
`adjacent one another, as shoWn in the left-hand portion of
`FIG. 5A.
`In the expanded material shoWn in FIG. 3, the leg seg
`ments 39 and 39a are oriented at an angle of betWeen 125°
`to 135° to each other, Which Would be the “internal” angle
`in the major diamond pattern as described hereinbefore.
`During crimping, these tWo pairs of leg segments 39, 39a
`pass through an angle of orientation to each other of 180°.
`FolloWing the completion of crimping, the same tWo leg
`segments are still oriented at about an angle of about 125°
`to about 135° to each other; hoWever, noW that angle is on
`the exterior of What Was once the major diamond cell in the
`expanded con?guration. What Was once the internal angle is
`noW the inverse of that angle. For example, if the intercon
`nected leg segments in the major cells Were oriented at an
`interior angle of about 130° to each other, that “interior”
`angle Would noW be about 230° in the crimped
`con?guration, as can be seen in FIG. 5. HoWever, because
`the relative angular orientation of the individual leg seg
`ments to one another is still the same, ie about 130°, in both
`the expanded and the unexpanded con?gurations of the
`stent, the axial length of the legs has not changed; thus, the
`length of the stent in its crimped condition is substantially
`the same as the length of the stent in its expanded con?gu
`ration. It can of course be seen that the expansion/
`compression of the diamond cells 35 and 41 has no effect
`upon the axial length of the stent, Whereas it provides the
`major amount of the circumferential dimensional change.
`ShoWn in FIG. 4 is a piece or-blank of stent material 33‘
`Which is essentially the same construction as the material 33
`With the exception that a plurality of pairs of oppositely
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`extending needle-like projections or prongs 51 and 53 are
`included. These projections are located so they are encom
`passed Within What has sometimes been termed the major
`diamond cells, and they are oriented axially, ie they Will lie
`parallel to the longitudinal axis of the fabricated tubular
`stent body. The projections 51 and the projections 53 extend
`in opposite directions and are used to affix a tubular bio
`logical membrane to the stent so that such a membrane can
`be transported in surrounding relationship about a crimped
`stent to a desired location Within a diseased artery or the like.
`Once so located and folloWing radial expansion of the stent,
`this biomembrane Will serve to provide a smooth interface
`betWeen the diseased or torn (dissected) Wall of the artery
`and the stent itself, thus isolating the major portion of the
`metal stent from the intima. In this form, the stent combi
`nation can simultaneously deal With tWo major and critical
`problems of coronary or other occlusive disease. Tubular
`biological membranes that are frequently employed as blood
`vessel substitutes are available from various sources, such as
`Shellhigh, Inc. of Millbourne, N.J., USA; they are typically
`given a tissue preservation treatment, such that as offered by
`Shellhigh as its No-ReactTM treatment. Such treatments are
`commonly knoWn in this art and may be employed to “?x”
`the tissue, ie to cross-link the collagenaceous chains of the
`tissue to give it increased strength, and also to endoW the
`tissue With some resistance to calci?cation. Mammary and
`other blood vessels from animals of the bovine and porcine
`species, for example, are available and frequently employed
`for such blood vessel substitutes; they Will serve as suitable
`biomembranes for the present invention. There may be
`advantages in af?xing the untreated blood vessels folloWing
`harvesting, and then treating the blood vessel as it has a
`tendency to shrink during ?xation. This Will cause the
`treated vessel to lie close to the surface of the stent Within
`the catheter sheath; hoWever, such biological membrane Will
`stretch along With the expansion of the stent Without tearing.
`In addition to the aforementioned stabiliZing treatments,
`these biomembranes may be used to carry and deliver
`different classes of medications from the interior and the
`exterior surfaces. For example, the intima may be medicated
`by impregnating the exterior surface With an antiprolifera
`tive medication, such as is Well knoWn in this art, Which
`Would serve to avoid rapid groWth of the adjacent tissue of
`the living blood vessel in Which the stent-biomembrane
`combination is being placed. At the same time, the interior
`surface of the biomembrane might be impregnated With
`pharmaeuticals that are released sloWly into the blood
`stream; examples include antithrombotic agents, such as
`heparin and salicilates, thrombolytic drugs, such as TPA, SK
`(streptokinase) and ReoproTM, and sloW-releasing gene
`therapy molecules Which stimulate rebuilding of neW blood
`vessels, i.e. neovascular proliferation.
`Illustrated in FIG. 6 is a fragmentary perspective vieW of
`a stent fabricated from the material illustrated in FIG. 4. In
`this tubular con?guration, the prongs 57, 53 are oriented
`axially of the tubular open frameWork so that the distance
`betWeen the adjacent prongs does not change as a result of
`expansion/compression of the stent. FIG. 6 of course illus
`trates the stent in its expanded con?guration Which Would
`occur Within the blood vessel, and the tubular biomembrane
`Would be installed about the stent When it is in its com
`pressed or unexpanded condition as explained hereinafter.
`Illustrated in FIG. 7 a fragmentary sectional vieW of a
`crimped tubular stent made from the material 33‘ Which
`shoWs a biological membrane 57‘ that is punctured by the
`pairs of needle-like prongs 51, 53 Which are bent radially
`outWard for the installation of the biomembrane. The
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`Edwards Lifesciences Corporation, et al. Exhibit 1114, Page 7 of 9
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`US 6,206,91 1 B1
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`7
`biomembrane 57 is installed over these radially oriented
`projections and aligned so that there is generally no slack in
`the membrane longitudinally. There could be shalloW folds
`of membrane betWeen axial roWs of pairs of prongs, or the
`biomembrane could have shrunk to a diameter close to that
`of the compressed stent. Precise radial cuts are preferably
`made in the tubular membrane at the sites Where the prongs
`Will penetrate the membrane so there Will be no local
`tearing. Once the membrane is in place, the tips of the
`projections 51 and 53 may optionally be bent in the appro
`priate directions to create short tangs 55, as shoWn on three
`of the four projections in FIG. 6. The prongs 51 are then bent
`to the right, as shoWn in tWo different stages, until they again
`lie essentially in the plane of the tubular stent. The projec
`tions 53, With their tips bent in the opposite direction to form
`tangs 55, are then bent to the left to the orientation as shoWn
`in one instance so as to ?rmly secure the biological mem
`brane 57 to the stent With the tangs embedded in the surface.
`Thereafter, upon circumferential expansion of the tubular
`stent Within the blood vessel of a patient, the biological
`membrane becomes spread out and/or stretches tautly on the
`exterior surface of the expanded stent With no folds or
`Wrinkles because of the fact that the axial length of the stent
`does not shorten during its transition to the expanded
`condition, having substantially the same length as in the
`crimped con?guration. Such biological membranes have
`considerable stretchability, as mentioned hereinbefore, so
`the slight axial expansion that occurs When the leg segments
`pass through an angular orientation of 180° during expan
`sion creates no dif?culty.
`Illustrated in FIG. 7 is an alternative method of joining a
`tubular biological membrane 57 to a stent Which can be
`effectively carried out using stent material that does not
`become foreshortened upon expansion. The stent material,
`for example, can be any of the constructions shoWn in FIGS.
`1, 2 or 3. The stent material is formed into its tubular
`condition, and then the tubular biological membrane is
`installed in place regularly surrounding the stent Which is in
`the compressed con?guration, With the tubular membrane 57
`being slightly shorter than the stent so as to leave a short
`margin at each axial end. Each end 61 of the stent is ?rst
`?ared outWard and then folded back upon itself so as to
`sandWich each end of the tubular membrane 57 betWeen tWo
`layers of stent material. Because of the relatively open
`pattern at each end of the stent, each end of the tubular
`membrane 57 becomes Well secured by this folding and
`crimping of the malleable metal stent material at spaced
`apart locations Which might lie betWeen shalloW folds in the
`membrane. Thus, the biological membrane 57 can be effec
`tively carried in place as part of such a stent combination,
`and upon expansion of the stent by an interior balloon
`catheter or the like, it provides a tubular support structure
`With a biological membrane smoothly disposed about its
`entire exterior circumference.
`Although the invention has been described in terms of its
`preferred embodiments Which constitute the best mode
`presently envisioned by the inventor for carrying out the
`invention, it should be understood that various changes and
`modi?cations as Would be obvious to one having ordinary
`skill in this art, may be made Without departing from the
`scope of the invention Which is de?ned by the appended
`claims. In this respect, Whereas the materials from Which the
`stents are preferably constructed are primarily illustrated in
`their expanded conditions, it should be understood that they
`may be laser-cut or otherWise suitably machined from mal
`leable sheet or tube material in their compressed or unex
`panded condition and suitably polished in this con?guration
`
`15
`
`3O
`
`35
`
`45
`
`55
`
`8
`to render them ready for installation in a human body.
`Moreover, it may be preferable to machine them from a tube
`of intermediate diameter and polish the tubular stent in such
`a partially expanded state prior to crimping. The medications
`With Which such biological membrane may be impregnated
`may be designed for fairly immediate release, or for sloW
`release over a predetermined period of time, and different
`classes of medications can be carried by the interior and the
`exterior of a biological membrane in the form of a mam
`malian blood vessel. Whereas the exterior surface may be
`impregnated With Well knoWn anti-proliferative compounds
`to prevent local intimal proliferation, the interior surface
`may be impregnated With thrombolytic agents, such as TPA,
`SK and urokinase, or With antithrombotic agents, such as
`heparin and salicitates, or With gene therapy molecules
`designed to promote neovasculariZation.
`Particular features of the invention are emphasiZed in the
`claims Which folloW.
`What is claimed is:
`1. An unexpanded intraluminal stent Which is radially
`expandable to an operative con?guration in Which it pro
`vides interior support for a blood vessel, Which stent com
`prises
`a tubular structure capable of being radially expanded
`from a smaller diameter unexpanded con?guration to a
`larger diameter fully expanded con?guration Without
`substantially any shortening of its axial length,
`said structure being formed of a malleable material Which
`in its fully expanded con?guration Will effectively
`resist return to a smaller diameter condition When
`subject to normal forces acting Within the body of a
`mammal,
`said structure constituting an open frameWork Which
`includes a plurality of axially extending leg means that
`extend from one axial end to the other of said tubular
`structure,
`said leg means each including a plurality of leg segments
`Which are interconnected With one another in the fully
`expanded con?guration at an angle of betWeen about
`120° and 140° in a Zig-Zag pattern, and
`said legs being spaced apart from one another in the fully
`expanded con?guration by a plurality of open diamond
`shaped cells Which are axially unconnected to one
`another, at least one vertex of each of said diamond
`shaped cells being connected to at least one of said legs,
`Wherein the leg do not form part of the diamond-shaped
`cells.
`2. The stent according to claim 1 Wherein said adjacent leg
`segments are oriented at an angle of betWeen about 125° and
`about 135° to each other both in said unexpanded con?gu
`ration and in said expanded con?guration.
`3. The stent according to claim 1 Wherein each of said
`cells includes four arms having approximately the same
`length and Width as one another.
`4. The stent according to claim 3 Wherein the Width of said
`leg segments is at least about 40% greater than the Width of
`said arms