US20110015721A1 - Intraluminal Stent - Google Patents

Abstract

An intraluminal stent made of a zig-zag or sinusoidal member defining a successive series of struts connected by apex sections and formed into a series of axially displaced hoop members wherein at least one of the hoop members has at least 5 one strut connected to a strut of an adjacent hoop. The connected struts may be connected by spot welding, continuous welding, or suturing, for example, or by a bridging member connected to each strut, and may be spaced along the length of the stent in a pattern to form a connective spine. The number of zigs of the zig-zag member in each hoop member may be varied, as can the zig length. A plurality of 10 connective spines may also be included.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 10/747,848, filed Dec. 29, 2003, which is a continuation of U.S. patent application Ser. No. 09/623,347, filed Nov. 15, 2000, which is a U.S. national phase application from International Patent Application PCT/US99/04694, international filing date Mar. 4, 1999, which claims priority based on U.S. Provisional Application Ser. No. 60/076,946, filed Mar. 5, 1998, which is hereby incorporated by reference.
FIELD OF INVENTION
• This invention relates generally to intraluminal prostheses, and more particularly to intraluminal stents comprised of zig-zag or sinusoidal wire hoops.
BACKGROUND OF THE INVENTION
• A common method of treating vessel diseases such as stenoses, strictures, thrombosis, or aneurysms involves placing a stent into the affected vessel. Among other advantages, stents prevent vessels from collapsing, reinforce vessel walls, increase cross sectional area (and thereby volumetric flow), and restore or maintain healthy blood flow. Many stents have been developed, and the prior art includes a wide variety of types and methods for their manufacture.
SUMMARY OF THE INVENTION
• The present invention is a generally cylindrical intraluminal stent including a plurality of circumferential wire hoops disposed in succession along the axis of the stent. Each of the hoops has zig-zag or sinusoidal members defined by a successive series of struts connected by apex sections alternately pointing in opposite axial directions. The struts may be substantially straight sections connected to essentially sharp apex sections in a jagged zig-zag configuration, or the apex sections may be more rounded so that together with the struts there is formed a sinusoidal configuration. The lengths of these struts may be uniform throughout the stent or may vary alternately or continuously. Likewise, the angles or radii of curvature and configurations of the apices may be uniform or may vary. To provide mechanical integrity, selected portions of the hoops may be secured against relative axial movement, such as by spot welding overlying straight sections either in an individual hoop or in adjacent hoops. Such connections may also be made with bridging members aligned with straight sections in adjacent hoops.
• These connections (with or without intervening bridging members) may be disposed in one or more linear or helical paths along the length of the stent, thus acting as stabilizing spines. Alternatively, these connections may be disposed in other preselected patterns, such as alternating around the circumference of the stent, to impart stability at these preselected locations.
BRIEF DESCRIPTION OF THE DRAWINGS
• The figures provided are for illustrative purposes, and are not drawn to scale. The expanded relative dimensions allow a better understanding of the present invention. One skilled in the art will readily determine actual dimensions based on information supplied in this specification.
• FIG. 1 is a diagrammatic view of an exemplary embodiment of a stent according to this invention, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened; also shown are mandrel pins used in forming the stent.
• FIG. 2 is a diagrammatic view of another exemplary embodiment of a stent according to this invention having multiple spines and axial and circumferential offsets between facing apex sections, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened; also shown are mandrel pins used in forming the stent.
• FIG. 3 is a partial diagrammatic view of another exemplary embodiment of a stent according to this invention having a plurality of longitudinal sections, the middle section having a different number of spines, a different number of zigs, and a different zig length than the end sections, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened.
• FIG. 4 is a diagrammatic view of another exemplary embodiment of a stent according to this invention having end portions with different zig characteristics relative to a center portion, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened; also shown are mandrel pins used in forming the stent.
• FIG. 5 is a diagrammatic view of another exemplary embodiment of a stent according to this invention having connecting members that include separate bridging members, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened; also shown are mandrel pins and weld holes used in forming the stent.
• FIG. 6A is a diagrammatic view of an exemplary embodiment of a stent according to this invention having interdigitated zigs, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened.
• FIGS. 6B-6D are diagrammatic views of enlarged portions of the stent ofFIG. 6A, showing an exemplary end weld, and exemplary middle weld, and an exemplary radiopaque marker, respectively.
• FIG. 6E is a diagrammatic view of an exemplary embodiment of stent6A, where the stent is shown in its normal tubular configuration.
• FIG. 6F is a diagrammatic view of an exemplary embodiment of a stent according to this invention having interdigitated zigs and a plurality of longitudinal sections of different zig configurations, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened
• FIG. 7 is a partial side view of an exemplary embodiment of a stent according to this invention having alternating zig lengths, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened.
• FIG. 8 is a partial diagrammatic view of another exemplary embodiment of a stent according to this invention having straight-edged apex sections, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened.
• FIG. 9 is a partial diagrammatic view of another exemplary embodiment of a stent according to this invention having connecting members formed by elongated struts, where the tubular stent is shown opened along a line parallel to the stent axis, and flattened; also shown are mandrel pins used in forming the stent.
• FIG. 10 is a partial diagrammatic view of the stent shown inFIG. 6A mounted on a mandrel during fabrication of the stent.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 illustrates anexemplary stent10 according to the present invention.Stent10 is generally cylindrical and adapted to be inserted into a lumen.Stent10 has been cut longitudinally and laid flat for purposes of illustration.Stent10 is formed by winding a continuous filament such as awire11 into a zig-zag or sinusoidal configuration and into a plurality ofcircumferential hoop members12a,12b,12cdisposed in succession along the axis ofstent10. Wire11 is preferably nitinol wire, which provides a stent that auto-expands by shape memory, but it may be made of any suitable material, including stainless steel and thermoplastic polymers. Thus, the stent may be capable of deployment by shape memory auto-expansion, thermal auto-expansion or balloon expansion, as are well-known in the art. The width of the wire affects the radial force exerted bystent10. Increasing the diameter ofwire11 increases the radial force.
• For convenience, the configuration of the wire is referred to throughout having a “zig-zag” shape with zigs or zig lengths. As so used herein, however, the term “zig-zag” encompasses not only a jagged zig-zag shape where the apex sections are relatively sharp and the struts are substantially straight, but also a sinusoidal shape where the apex sections are rounded and, together with the struts, form a shape resembling a sine wave having an amplitude (zig length) and a period or wavelength (zig width). Similarly, although the apex sections may be referred to as defining a zig angle, the angle may be more rounded such that lesser and greater angles may be more envisioned as smaller and larger radii of curvature, respectively. Of course, the actual wire configuration may have a shape intermediate the jagged zig-zag and rounded sine wave shapes, or may be even more rounded than a sine wave, and the apex sections may in fact have a truncated, straight edge rather than a rounded shape or sharp angle, as described herein later.
• To formstent10,wire11 is wound aroundpins13 on a mandrel (not shown). The mandrel is typically cylindrical (although other shapes may be used as necessary to form stents of varying shapes) and of a diameter determined by the diameter of the vessel into whichstent10 is to be inserted. Typically, the mandrel diameter, and hence the intended diameter ofstent10, is slightly larger (for example, by one millimeter) than the diameter of the vessel. The length ofstent10 is also determined by the particular application.
• Stent10 is formed by windingwire11 aroundpins13 beginning at point A inFIG. 1.Wire11 is extended to and aroundpins13a,13b,13cand so forth. In this manner, zig-zag members are formed and defined by a successive series of substantially straight sections (struts)14 connected byapex sections15 alternately pointing in opposite axial directions. The winding continues in this manner around the mandrel until afirst hoop member12ais completed by windingwire11 once around the circumference of the mandrel.Hoop member12aas shown inFIG. 1 has a circumference lying in a plane substantially perpendicular to the axis of the mandrel (and hence of stent10). Once afirst hoop member12ais formed,wire11 is extended frompin13dto and aroundpin13e. Winding then continues as before to form asecond hoop member12badjacent tofirst hoop member12a. By forming hoop members in this manner,adjacent hoops12aand12bare connected by the portion ofwire11 extending betweenfirst hoop member12aandsecond hoop member12b. At the completion of thesecond hoop member12b,wire11 is again extended to thethird hoop member12c, which is wound as before, and so forth until the desired number N ofhoop members12 are formed along the length ofstent10. Thus, as shown inFIG. 1, the winding extends in a series of hoops betweenhoops12aandhoop12N, with the wire beginning at point A and ending at point B. After completion of winding,wire11 is typically cut so that the wire terminates short of points A and B, generally terminating within thefirst hoop12aandlast hoop12N, respectively, as described with reference toFIG. 6C herein later.
• Stent10 is removed from the mandrel and pins13a,13b,13c, etc., prior to use. In the illustrated embodiment, eachhoop member12 has one pair of aligned,adjacent struts14aand14b. According to one embodiment of the present invention, aligned,adjacent struts14aand14bof the same hoop are welded together. Such welding may be spot welding along the length of aligned,adjacent struts14aand14b, or it may be a continuous weld. In either case, a welded,connective spine16 is formed along the perimeter ofstent10.Connective spine16 typically winds around the circumference ofstent10 in an offset helical fashion (the embodiment shown flat inFIG. 1 being cylindrical or tubular in actual use).Connective spine16 provides strength and stability tostent10 while preserving the flexibility ofstent10. During insertion ofstent10 into a vessel (described below),connective spine16 rendersstent10 easier to push through a catheter. As an alternative to welding,connective spine16 may be formed by connecting aligned,adjacent struts14aand14baccording to any other suitable attachment means, including without limitation, tying, suturing, gluing, and stapling, with the glue or sutures being absorbable or non-absorbable, and including the use of polymer-containing connections.
• Whenstent10 comprises thermally expandable nitinol,stent10 is annealed before removal from the mandrel and pins13a,13b,13c, etc., at an annealing temperature for about one hour and then allowed to cool. This annealing temperature is desirably on the order of about 500° C., although any temperature sufficient to effect annealment ofstent10 will suffice. During annealing, it may be necessary to secure the nitinol wire to the mandrel by wrapping bailing wire, a thicker gauge and different material than the nitinol, around the stent on the mandrel. Such annealing of nitinol wire imparts a memory to the nitinol, such thatstent10 will “remember” its annealed shape and return to it after subsequent reconfiguration. This is a known property of nitinol, which has two distinct temperature-dependent phases, martensite and austenite. Below a certain temperature (the martensite transition temperature), nitinol is martensitic; above a certain temperature (the austenite transition temperature), it is austenitic. It is in the austenitic phase that nitinol remembers its annealed configuration.
• After annealing,stent10 is removed from the mandrel on which it is wound to compressstent10 into a configuration for introduction to a body passageway. Then, it is cooled to below its martensitic transition temperature. In this phase, nitinol is malleable and has virtually no resiliency. Thus, it can be easily compressed.Stent10 can be easily returned to its annealed shape by heating it to a temperature above its austenite transition temperature. Above this temperature, the stent resumes its annealed configuration.
• In its annealed configuration,stent10 has a first diameter. This is a relatively large diameter that is the intended final diameter ofstent10. In order to be inserted into a body vessel,stent10 must be compressed such that it may be inserted into a catheter. As indicated above, with a nitinol stent, this is accomplished by coolingstent10 to below its martensite transition temperature at whichtemperature stent10 is malleable and less resilient.Stent10 can then be easily compressed into a second, relatively small diameter for insertion into the catheter. Once inside the catheter,stent10 may be advanced to the desired location within a body vessel according to methods known in the art and discharged from the catheter at that location. U.S. Pat. Nos. 5,405,377 and 5,609,627, the disclosures of which are incorporated herein by reference, contain additional details regarding the formation, use, and insertion of nitinol stents. Those patents are incorporated herein by reference for their teaching on those subjects. When stainless steel, thermoplastic polymers, or other materials are used forwire11, formation, use and insertion ofstent10 may be accomplished according to methods known to those skilled in the art.
• Connective spine16 lends strength, including hoop strength, tostent10 during and after implantation to better resist compressive forces within the vessel in whichstent10 is implanted.Connective spine16 also allows flexibility, however, such thatstent10 may be easily compressed and expanded during the insertion process.
• Particular features of the stent according to this embodiment of the invention are illustrated inFIG. 2. As shown inFIG. 2, facingapex sections15 of respective adjacent hoops ofstent10A are offset circumferentially from one another by a distance D1, as opposed to abutting one another. The offset allowsstent10A to be compressed to a smaller diameter (profile) for insertion into the catheter because the apex sections do not contact one another and hinder such compression. Increasing the axial distance D2 between apex sections15 (the “zig gap”) also prevents interference between these sections during compression. The particular amount of offset and zig gap can be optimized according to particular stent sizes and the desired flexibility and compressed diameter as will be understood by those skilled in the art.
• FIG. 2 also illustrates an embodiment of this invention having multiple, in this case two,connective spines16. To form twoconnective spines16, twoseparate wires11 and11A are used to formstent10A. As shown inFIG. 3,first wire11 is formed in a zig-zag shape extending from point A to points B, C, D, E, F, G, H, I, J, K, L, M, N, O, P (etc.) sequentially. Asecond wire11A is used to form the remainder of the stent by extending, in sequence from point E to points Q, R, S, A, T, U, V, W, X, V, Z (etc.). In this manner, each hoop contains two pairs of aligned,adjacent struts14aand14b. Aligned,adjacent struts14aand14bare then welded (or otherwise connected) to formconnective spines16. In general, the number ofwires11,11A, etc. used to formstent10A directly corresponds to the number ofconnective spines16 that are desired. The strength and rigidity ofstent10A increase with the addition ofconnective spines16.
• In the above configuration, the mandrel peg at each lettered point may be considered to be one of a set of pegs corresponding to the wire to wound about the set. Thus, pegs at points A, B, C, etc. above are a part of one set, and pegs E, Q, R, etc. above are part of a second set. Each set, however, contains at least one common peg (for example, F in the first set and W in the second set) where both wires follow a common path between the common pegs of the circumferentially adjoining sets. The wires that form the common path (adjacent struts14aand14b) are connected as described above.
• FIG. 3 illustrates another alternative embodiment of this invention wherein the zig length L₁is varied withinstent10B. Zig length L₁is the distance betweenapex sections15′ and15″ measured in a direction parallel to the stent axis (vertical, inFIG. 3). As previously indicated, the zig length may similarly be described as the amplitude of a sinusoidally shaped zig-zag. In this embodiment, the zig length atend sections22 ofstent10B may be relatively short (relatively small amplitude), while the zigs inmiddle section20 ofstent10B are relatively long (having greater amplitude). This may provide greater radial force at the ends ofstent10B to assist in anchoring the stent in place in the vessel into which it is inserted by asserting a greater force against the walls of the vessel. This may also prevent blood from leaking betweenstent10B (when the stent is used in combination with a graft, as will be understood by those skilled in the art) and the vessel wall.
• As illustrated inFIG. 3, there may also be atransition section21 in which there is a transition zig length, between the short zig length at the stent ends22 and the long zig length in the stent middle20, to provide a gradual transition from the short to the long zigs. Typical short zig lengths are between two and three millimeters. Typical long zig lengths are between three-and-a-half and five millimeters. The actual zig lengths may be optimized for particular applications as will be understood to those skilled in the art based on the disclosure herein.
• Another aspect of this invention involves the variation of the number of zigs in each hoop member. Referring back toFIG. 1, a “zig” is considered to be the part ofwire11 extending from, for example, point X to point Y to point Z. X-Y-Z inFIG. 1 is considered to represent one zig. Thus, each similarly-oriented apex section (i.e. each apex section pointing in the same direction) defines a zig. As previously indicated, the number of zigs in a hoop may be similarly described as the number of periods of a sinusoidally shaped zig-zag. InFIG. 1, each hoop member has five zigs. Using fewer zigs allowsstent10 to be compressed to a smaller insertion diameter (that is, fewer zigs decreases the profile of stent10). Increasing the number of zigs provides more support for any graft covering used in conjunction with the stent, however, preventing the possibility of in-folding of such graft layer.
• FIG. 4 illustrates an alternative embodiment, not drawn to scale, wherein thecenter portion20 ofstent10 has four zigs perhoop member12, a first zig length, and oneconnective spine16; and theend portions22 have six zigs perhoop member12, a second zig length, and twoconnective spines16. The second spines on both ends overlap twohoop members12 of the center portion as a transition. The number ofconnective spines16 can thus be varied within a stent to provide a more rigid portion at the ends and a more flexible portion in the middle. The stent illustrated inFIG. 8 may have, for example, a wire diameter of 0.007 inches, a 6.4 mm 00, a 6 mm ID, and a length of 100 mm. Other wire diameters slightly larger than 0.007 inches such as 0.008 or 0.009 inches, for example, will suffice.
• As shown inFIG. 9, another method of making connecting members may comprise axially opposedapex sections15 ofadjacent hoops12 being axially spaced from one another with one or both of the first andsecond struts14′ of the connecting member elongated relative to the remainder of thestruts14 in the adjacent hoops. Suchelongated struts14′ may thus lie adjacent one another for at least some axial distance to permit connection therebetween.
• FIG. 5 illustrates a stent constructed according to another exemplary embodiment of the present invention.Stent30 is generally cylindrical and adapted to be inserted into a lumen.Stent30 has been cut longitudinally and laid flat for purposes of illustration.Stent30 is formed by winding a continuous filament such as awire24 into a zig-zag configuration and into a plurality ofcircumferential hoop members33,25a. . .25N, and37 disposed in succession along the axis ofstent30.Wire24 is extended to and around pins23a,23b,23cand so forth. In this manner, zig-zag members are formed and defined by a successive series of substantiallystraight sections34 connected byapex sections35 alternately pointing in opposite axial directions. The winding continues in this manner around the mandrel until afirst hoop member33 is completed by windingwire24 once around the circumference of the mandrel. Winding then continues as before to form asecond hoop member25aadjacent tofirst hoop member33 and athird hoop member25badjacent tosecond hoop member25a. Unlikehoop members12 ofstent10 as shown inFIG. 1,hoops25a. . .25N are disposed at an angle to a plane perpendicular to the stent longitudinal axis;wire24 then gradually spirals about the axis ofstent30 to form a coil.End hoops33 and37, however, are disposed perpendicular to the stent axis. The helical configuration may be effected by each apex section in the helix having one connected strut longer than the other.
• As further illustrated inFIG. 5, adjacent hoops are connected by aseparate bridging member26 adjacent portions of respectivestraight sections34 and34A of axially opposed apex sections of adjacent hoops. As illustrated inFIG. 5, bridgingmember26 is preferably linear and aligned with alignedstruts34 and34A of proximate sections ofadjacent hoops25_i, and25_i+1although non-linear and nonaligned bridging members are also contemplated in accordance with the present invention, as may be appreciated by those skilled in the art. Separate bridging “member26 may be the same material as or a different material thanwire24 used to formhoops33,25a-N, and37 ofstent30, depending on the desired flexibility and compressed stent diameter. In one embodiment, separate bridgingmember26 andwire24 are made of the same material, for example, nitinol. Separate bridgingmember26 andwire24 may have approximately the same or different cross sectional dimensions (i.e. the same or a different wire gauge), depending on the desired implementation.
• An exemplaryseparate bridging member26 is preferably formed by extending a wire segment between a pair ofpins28 extending from the mandrel proximatestraight sections34 and34A ofadjacent hoops25_iand25_i+1. Thesepins28 and29 are in addition topins23a,23b, etc. used to form zig-zag members of the respective hoops ofstent30. Wire-segment bridging member26 is extended betweenpins28 and both ends are at least partially wrapped around the pins, preferably with enough tension to remove unwanted slack from the wire, although various amounts of slack may be maintained, depending on the desired rigidity, flexibility, and compressed diameter ofstent30.
• To effect welds during manufacture of a stent of the present invention, and as shown inFIG. 5, ballweld cutting holes29 may be formed in the mandrel providing access to the mandrel interior, the holes desirably positioned such that sections to be welded, such as aligned,adjacent struts34 and34A, lie approximately above the ball weld cutting holes. In this way, a laser may be focused into ballweld cutting holes29 to: (i) remove excess wire extending past ballweld cutting holes29 and around the pins, and (ii) weld the remaining wire segment between the aligned, adjacent struts of adjacent hoops as, for example, bridgingmember26 betweenstruts34 and34A. The connection between bridgingmember26 and struts34 and34A may, instead of a weld, may be accomplished according to any other suitable attachment means, including without limitation, tying, suturing, gluing, and stapling, with the glue or sutures being absorbable or non-absorbable, and including the use of polymer-containing connections.
• As further illustrated inFIG. 5, astent30 constructed in accordance with the present invention may further include the plurality ofseparate bridging members26a-26N disposed in succession along the length of the stent. Each successiveseparate bridging member26, connects a successive pair of adjacent hoops along the axis ofstent30 to form a spine along the length ofstent30. The spine may be a continuous spine of helically-aligned bridging members, similar to the spine illustrated inFIG. 1, or may be constructed of a single bridging member connecting a plurality of hoops along the length of the stent. Alternatively, as shown inFIG. 5, each successive connectingmember26, may be circumferentially offset from a preceding connecting member with respect to the axis ofstent30 to define a helical spine of disjointed connecting members, or a “floating” spine.Hoop members33,37 disposed at each end ofstent30 may have the apex sections that point outwardly from the stent disposed in common planes perpendicular to the axis ofstent30, such asapex sections35′ ofhoop34 along plane I, as shown inFIG. 5.
• To make this transition from hoops other thanperpendicular end hoops33 and37 to the end hoops, the successive lengths of struts in the end hoops may be reduced along the circumference of the hoops. Additionally, or in the alternative, the successive amount of interdigitation (overlap) between apex sections of adjacent hoops may increase along the circumference ofend hoops33 and37 approaching the end ofwire24.
• FIGS. 6A-6E illustratedstent40, another exemplary embodiment of the present invention. Instent40,adjacent hoops42a. . .42N are interdigitated with respect to one another. That is, oppositely directedapex sections44A and44B in respectiveadjacent hoops42band42c, for example, overlap one another axially, or expressed another way, they intersect a common plane angularly disposed with respect to the axis ofstent40.Hoop members42a. . .42N also preferably have zigs substantially in phase circumferentially aboutstent40.Stent40 comprises a continuous series of similarly-orientedapex sections44A arranged in a helix in which each hoop42; comprises one 360-degree wrap of the helix. Each apex section in the helix comprises two struts attached thereto, in this embodiment with one strut being longer than the other to effect the helical progression. Such a hoop configuration is also seen in U.S. Pat. No. 5,575,816 to Rudnick et al., which is incorporated herein by reference and which illustrates a variety of other interdigitated stent configurations.
• In a pair of adjacent hoops, such ashoops42band42c, onestrut45 ofhoop member42bis aligned with and overlaps strut45 ofhoop member42c, and is connected to form a connectingmember48a-N, preferably by spot welding, although other connection mechanisms are contemplated as will be understood by those skilled in the art.Interdigitated stent40 in its normal tubular form is illustrated inFIG. 6E.
• Referring now toFIG. 10, there is shown ahelical stent110, corresponding to the layout shown inFIG. 6A, on atubular mandrel114.Helical stent110 or a helical segment thereof, as shown inFIG. 10, may be constructed by windingN filaments111, where N is a whole number of at least 1, around N respective sets of pegs112a-N on atubular mandrel114. As shown inFIG. 11, N=1. Each of the N sets includes at least three axially offset pegs, such aspegs112a,112b, and112c, defining a zig-zag configuration at a preselected axial location onmandrel114, with circumferentially successive pairs of pegs (pegs112cand112d, for example) being axially offset in a preselected direction from the pair which precedes it (pegs112aand112b) so as to form a helical zig-zag pattern repeatedly traversing the mandrel along the length ofstent110. Each traversal of a preselected angular portion ofmandrel114 by pegs112a-N includes at least one common peg (112r, for example) approximately 360° helically offset from an adjacent peg (112k). The peg adjacent the common peg may be part of the same set of pegs (for instance, where N is equal to 1) or a part of a circumferentially adjoining set of pegs (where N is greater than 1).Common peg112rprovides at least one circumferential location in each traversal of a preselected angular portion, where a portion of the filament in each traversal of a preselected angular portion contacts a portion of a filament in an adjacent traversal. This contact may be with the same filament (for instance, where N is equal to 1 as shown inFIG. 11) or with an different filament (where N is greater than 1). Aconnection48 is formed along the contacting adjacent filaments or portions thereof, forming a circumferential stent or segment thereof comprised of a helical succession of zig-zags. Thus, the wire configuration may form a helix as shown inFIGS. 6A,6E, and11, or a double- or other multiple-helix (not shown). As shown inFIG. 6A, a single filament (N=1) repeatedly traverses the mandrel (not shown) along a single set of pegs, wherein in each angular traversal of 450° there is acommon peg13′ approximately (in this case slightly greater than) 360° offset from anadjacent peg13′ (the pegs immediately adjacent each connectingmember48a-N).
• Stent40 as shown inFIG. 6A comprises a plurality of connectingmembers48a-N disposed in succession along the stent axis between pairs of adjacent hoops. Each set of connectingmembers48a-N connects a successive pair of adjacent hoops along the axis ofstent40 to form a spine along the length of the stent. As with the successive connectingmembers26 ofFIG. 5, each pair of successive connectingmembers48; is circumferentially offset from a preceding connectingmember48_i−1with respect to the axis ofstent40.
• As shown inFIG. 6A, eachapex section44B includes an apex angle α and a zig width W measured between adjacent,apex sections44A oppositeapex section44B. As shown inFIG. 6A, the included angle (zig angle) and zig width ofapex sections44B are essentially uniform throughoutstent40, except for the apex sections44W and44W′ that include thestruts45 that form connectingmembers48a-N.Apex sections44B′ and44B″ have a non-uniform zig angle and resulting zig width as compared toapex sections44B. As shown inFIG. 6A, the zig includingapex section44B′ has a greater included angle and has a greater zig width than the uniform angle and width included byapex sections44B;apex section44B″ has a lesser included angle and smaller zig width than the uniform angle and width. As shown inFIG. 6A,stent40 comprises a helical configuration having 4 zigs per 360-degree wrap, each such wrap comprising a hoop. Apex section44W is spaced 5 zigs from each preceding44B′;apex section44B″ is similarly spaced 5 zigs from each preceding44B″. Thus, for a stent with N zigs, the non-uniform zigs are spaced every N+1 zigs to achieve the helical pattern ofconnections48a-N as shown inFIG. 6A. In other words, for the 4-zig stent of6A, connectingmembers48a-N are uniformly distributed in a helical spacing approximately every 450° along the length of the stent to form a helical spine. Other helical or non-helical spine configurations may be achieved by spacing the non-uniform zigs differently.
• FIGS. 6B and 6C illustrate exemplary spot weld configurations withinstent40. For adjacent, aligned struts48b-48_n−1, the portion of each strut adjacent one another may be of a first length having aweld54 of length L₁, as shown inFIG. 6B. For adjacent, aligned struts48aand48N on the end hoops, however, the portions of each strut adjacent one another may be longer, and thus may include aweld56 of length L₂, as shown inFIG. 6B. To avoid sharp edges protruding from the stent,end strut58 may be cut, as shown inFIG. 6C, so that it terminates a distance D fromweld56 in a position that lies short of plane II on whichapex section46 lies. For instance, the end ofend strut58 may be cut so that it terminates a distance above plane II equivalent to the radius R ofapex section46. As shown inFIG. 6A,end strut58 has not yet been cut, but may be cut using ballweld cutting hole29, similar to those described with reference toFIG. 5.
• FIG. 6D illustrates an exemplaryradiopaque marker59 that may be used with the present invention.Marker59 may comprise a radiopaque substance, such as a platinum wire, wrapped about a strut on an end hoops. This substance thus defines a surface having a different radiopacity than the area surrounding it. This same effect may be achieved by marking a particular location of the stent with an area of lower radiopacity. One ormore markers59 may be disposed on one or both of the end hoops.Marker59 generally may be tightly wound with no underlying strut visible to the unaided eye, and may extend 1-2 wraps past the start of the radius where the strut bends to form the apex section.Marker59 is typically configured without sharp edges at the ends.
• FIG. 6F is a diagrammatic view of an exemplary embodiment ofstent60, opened along a line parallel to the stent axis and flattened, having interdigitated zigs, similar tostent40 ofFIG. 6A-E, but additionally having a plurality of longitudinal sections, similar tostent10C as shown inFIG. 4.Middle section62 has a longer zig length thanend sections64, andtransition sections63 intermediate the middle section and each end section have a zig length that is between the length of the middle and the end section zigs.
• FIG. 7 illustrates still anotherstent70 constructed in accordance with the present invention.Stent70 has been cut longitudinally and laid flat for purposes of illustration.Stent70 is formed by winding a wire around pins extending from a mandrel somewhat similar to the manner described with reference toFIG. 1, although the pins are configured such that zig-zag sections ofrespective hoops76a,76b,76c,76dare of varying height and varying width. In the embodiment illustrated inFIG. 7, the width of the zig length alternates between distance XX and WW along each hoop circumferentially aboutstent70. The zig length similarly alternates between length YY and ZZ moving along each hoop circumferentially aboutstent70. Length ZZ is approximately half of length YY inFIG. 7, although other length variations are contemplated. Adjacent hoops, such ashoops76aand76b, are phase-shifted by approximately and 180 degrees and inverted with respect to one another. Accordingly,apex sections65 and66 ofhoop member76apass through a plane perpendicular to the axis ofstent60 determined by the positions of oppositely directed alternateapex sections67 and68 inadjacent hoop76b. The configuration ofFIG. 7 may be incorporated into transition segments of other stents constructed according to the present invention.
• A series ofseparate bridging members72a,72b, and72cconnectsadjacent hoops76aand76b, as shown inFIG. 7. Another series of separate connectingmembers74aand74bconnects adjacent hoops62band62c. Bridgingmembers72a,72b, and72care angled relative to the tubular axis ofstent70 in opposite orientations than bridgingmembers74aand74b, to counter rotating effects in stents in which bridging members between successive pairs of adjacent hoops are oriented in the same direction. The number of bridging members may vary, depending on the desired implementation, as may the orientations of bridgingmembers72a,72b,72c,74aand74b.
• Stent80 ofFIG. 8 is formed by winding afirst wire81 around pins (not shown) on a mandrel. The geometry of the pins may be substantially circular to produce rounded apex sections, as inFIG. 1, or have straight edges such as to produce apex sections having straight edges as inFIG. 8. In this manner, zig-zag members are formed and defined by a successive series ofstruts84 connected byapex sections85 alternately pointing in opposite axial directions. The winding continues in this manner around about half the circumference ofstent80. Asecond wire86 is introduced and wound around the remaining circumference ofstent80 to complete afirst hoop member82a. Wherewires81 and86 overlie one another, they may be spot or linearly welded, thus to produce a pair of helical spines lending integrity tostent80.
• Any of the variations described herein may be combined with any other variation described herein or known in the art, where practical, to develop a stent architecture according to the present invention. Such variations may be uniformly utilized throughout the length of the stent, or as shown inFIG. 6F, the stent may comprise a plurality of longitudinal sections, each of which may differ from another segment with respect to, for example without limitation: the size of one or more of the apex section angles, the apex section axial length, the number of apex sections per hoop, the number of connective spines, the spacing or offset between facing apex sections, the type of connecting member, and the uniformity of adjacent zigs. Moreover, the “struts” of each apex section and the connections therebetween may be straight, as in a jagged zig-zag configuration, or curved somewhat, such as when the overall stent section is more sinusoidal.
• Although this invention has been described with reference to particular embodiments, it is not intended that this invention be limited thereto. Rather, the scope of the appended claims should be construed to cover all forms and variants of the invention as may be made by those skilled in the art without departing from the spirit and scope thereof.

Claims (5)

1. A stent having a circumference and a longitudinal axis, the stent comprising a first end, a first end section, a middle section, a second end section, and a second end, the middle section engaged to and extending between the first and second end sections;

the first end section comprising a plurality of substantially straight portions connected one to another by turns, the plurality of substantially straight portions and turns forming a circumferential ring that extends about the circumference of the stent,

the middle section comprising a plurality of substantially straight portions connected one to another by turns, the plurality of substantially straight portions and turns forming a plurality of helical hoops, the plurality of substantially straight portions comprising first substantially straight portions having a first length and second substantially straight portions having a second length less than the first length; and

the second end section comprising a plurality of substantially straight portions connected one to another by turns, the plurality of substantially straight portions and turns forming a circumferential ring that extends about the circumference of the stent.

2. The stent ofclaim 1 wherein some of the turns form the first end of the stent, the turns forming the first end being intersected by a plane which is perpendicular to the longitudinal axis of the stent and some of the turns form the second end of the stent, the turns forming the second end being intersected by a plane which is perpendicular to the longitudinal axis of the stent

3. The stent ofclaim 1, the substantially straight portions of the first end section and the substantially straight portions of the second end portions having variable lengths.

4. The stent ofclaim 1, the substantially straight portions of the first end section being substantially the same length and the substantially straight portions of the second end section being substantially the same length.

5. The stent ofclaim 1, helical hoops which are longitudinally adjacent one another are engaged by a connector, the connector engaging two substantially straight portions.

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