I
`
`Unlted States Patent [19]
`Fontaine
`
`IlllllllllllllllllllllIllllllllllllllllllllllllllllllllllllllllllllllllllll
`USOO5370683A
`[11] Patent Number:
`5,370,683
`[45] Date of Patent:
`Dec. 6, 1994
`
`[54] VASCULAR STENT
`
`'
`'
`[75] Invento? Arthur 3- Fontame, Fresno, Cah?
`.
`_
`-
`[73] Asslgnee' C°°k Inwmmed’ Blwmmgton’
`Ind-
`[21] Appl‘ No‘: 192’064
`[22] Filed;
`Feb. 4, 1994
`
`[63]
`
`Related US. Application Data
`Continuation of Ser. No. 858,304, Mar. 25, 1992, aban»
`doned'
`[51] Int. Cl.5 .............................................. .. A61F 2/06
`[52] US. Cl. ...................................... .. 623/1; 606/198;
`623/12
`[5 8] Field 01' Search .................. .. (306/198, 200; 623/ 1,
`623/11, 12, 900
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,776,337 10/1988 Palmaz .
`
`5,015,253 5/1991 MacGregor .
`5,019,090 5/ 1991 Pinchuk ............................ .. 606/ 194
`5,135,536 8/1992 Hillstead .
`...... .. 623/1
`5,161,547 11/1992 Tower
`606/198
`5,163,958 11/1992 PlnCl'luk ..
`606/198
`5,314,472 5/1994 P61161166 ............................... .. 623/1
`Priman/ Examiner-C. Fred Rosenbaum
`Assistant Examiner-N. Kent Gring
`Attorney, Agent, or Firm-Richard J. Godlewski
`[57]
`ABSTRACI
`A vascular Stem for reducing hemodynamic disturb
`ances caused by angioplasty. The stent is formed from a
`single ?lament of low memory biocompatible material
`having a series of U-shaped bends. The ?lament is
`wrapped around a mandril, in a circular fashion, in
`order to align the curved portions of each bend which
`may then be connected. The stent provides a maximum
`amount of structural support for the lumen while mini
`mizing hemodynamic disturbances inside the lumen.
`
`14 Claims, 6 Drawing Sheets
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`Dec. 6, 1994
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`1
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`VASCULAR STENT
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`5,370,683
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`LII
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`RELATED APPLICATION
`This is a continuation of copending application(s) Ser.
`No. 07/858,304 ?led on Mar. 25, 1992 now abandoned,
`which is a continuation-in-part of .co-pending applica
`tion Ser. No. 07/769,216, ?led in the United States Pa
`tent and Trademark Office on Oct. 1, 1991, now US.
`Pat. No. 5,314,472, and commonly assigned herewith,
`the disclosure of which is incorporated herein in its
`entirety. The present application is also a parent appli
`cation for copending continuation-impart applications
`Ser. Nos. 07/ 874,347, pending ?led Apr. 24, 1992, and
`07/943,000, pending ?led Sep. 10, 1992, both of which
`are commonly assigned herewith. This application is
`primarily related to copending design application Ser.
`No. 07/847,247, pending ?led Mar. 9, 1992, and com
`monly assigned herewith. This application is also sec
`ondarily related to copending design applications Ser.
`Nos. 07/723,525, pending ?led Jun. 28, 1991, and
`07/929,l50, pending ?led Aug. 13, 1992, both of which
`are commonly assigned herewith.
`'
`
`2
`PTCA procedures tend to restenose at an even higher
`rate than ?rst-time PTCA patients.
`A second, and sometimes fatal, complication of coro
`nary angioplasty is the abrupt re-closure of a previously
`dilated section of a vessel. There are many different
`factors that are thought to contribute to abrupt re-clo
`sure after PTCA including obstructive flaps of dis
`rupted wall tissue, vessel wall spasms with luminal con
`traction, and thrombus formation at the site of dilation.
`Vascular stents can be used like a scaffold to mechani
`cally bridge areas of narrowing (?aps or thrombus) and
`oppose spasms, and therefore, maintain artery patency.
`Many of the factors responsible for abrupt closure
`(post balloon inflation) may also in?uence the develop
`ment of restenosis, and therefore, long term patency. In
`this regard, vascular stents, by virtue of their ability to
`limit elastic recoil of the vessel wall and to eliminate the
`negative physical consequences of PTCA (including
`obstructing intimal flaps and dissection) may be useful
`in limiting restenosis.
`Therefore, there are two potential bene?ts of vascu
`lar stents in the treatment of vascular disease: 1) preven
`tion of abrupt arterial closure, and 2) prevention of
`restenosis.
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`35
`
`SUMMARY OF THE INVENTION
`Generally speaking, the present invention provides a
`vascular stent for reducing hemodynamic disturbances
`caused by angioplasty and the stent itself. In a preferred
`embodiment, the stent is formed from a single ?lament
`of low memory biocompatible material having a series
`of U-shaped bends. The ?lament is wrapped around a
`mandril in a circular fashion in order to align opposing
`curved portions of each bend which are then con
`nected. The stent therefore provides a maximum
`amount of structural support for the lumen while mini
`mizing the level of hemodynamic disturbance inside the
`lumen.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The present invention generally relates to vascular
`stents.
`2. State of the Art
`A stent, generally speaking, is a device that can be
`placed within the lumen, or interior space, of a tubular
`structure for supporting and assuring patency of a con
`tracted, but otherwise intact, lumen. (Patency, the state
`of being freely open, is particularly important in the
`?eld of angioplasty, which is concerned with the recon
`struction of blood vessels.) Stents are used, for example,
`for holding blood vessels open or for back tacking inti
`mal ?aps inside vessels after angioplasty. More gener
`40
`ally, however, stents can be used inside the lumina of
`any physiological conduit including arteries, veins, ves
`sels, the biliary tree, the urinary tract, the alimentary
`tract, the tracheobronchial tree, the genitourinary sys
`tem, and the cerebral aqueduct. Furthermore, stents can
`be used inside lumina of animals other than humans.
`In the ?eld of angioplasty, the most common angio
`plasty surgical procedure is percutaneous transluminal
`coronary angioplasty, or “PTCA”, which is employed
`for enlarging narrowed arteries near the heart. In a
`PTCA procedure, a balloon-tip catheter is maneuvered
`into position in a narrowed artery where the balloon is
`expanded in order to dilate this area of narrowing. After
`the arterial lumen is dilated, the balloon at the catheter
`tip is de?ated and the catheter is removed from the
`enlarged artery. A vascular stent can be used to dilate
`an artery after a suboptimal PTCA dilation.
`In practice, the above-described conventional PTCA
`procedure has several shortcomings. One drawback is
`that approximately one-third of all PTCA patients suf
`fer from restenosis, a chronic regrowth of obstructive
`tissue that narrows the lumen. Typically, restenosis
`occurs within six months following an angioplasty pro
`cedure. Since a majority of these restenosis patients also
`display symptoms of deteriorating cardiac status, they
`frequently must undergo additional PTCA procedures
`or more risky coronary artery bypass graft surgery.
`Unfortunately, those patients who undergo repeated
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The present invention can be further understood with
`reference to the following description in conjunction
`with the appended drawings, wherein like elements are
`provided with the same reference numerals. In the
`drawings:
`FIG. 1 shows a ?lament shaped into a compressed
`planar wave used to make the nearly sinusoidal wave
`form of FIG. 2;
`FIG. 2 shows the planar wave of FIG. 1 expanded
`along its longitudinal centerline to form a nearly sinu
`soidal waveform used in making a stent;
`FIG. 3 shows an alternative waveform that can be
`also be used in making a stent;
`FIG. 4 shows another alternative waveform that can
`be used in making a stent;
`FIG. 5 shows the waveform of FIG. 3 spirally
`wrapped around a round mandril;
`FIG. 6 shows a connection for the end of the ?lament
`after the waveform of FIG. 3 is completely wrapped
`around the mandril;
`FIG. 7 shows a preferred alternative waveform that
`can be used in making a stent;
`FIG. 8 shows the relative positions of the U-shaped
`bends in each component section of the preferred alter
`native waveform of FIG. 12;
`FIG. 9 shows the preferred alternative waveform of
`FIG. 7 being wrapped around a cylindrical mandril;
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`FIG. 10 shows a side elevation of a stent formed from
`waveform of FIG. 3 is preferably one-half of the peak to
`the preferred alternative waveform of FIG. 7 by wrap
`peak amplitude of the waveform. In FIG. 3, the longitu
`ping it around a mandril in a circular fashion in order to
`dinal centerlines of the small waveforms 170 at the ends
`align the curved portion of each bend;
`of the device are approximately parallel to each other,
`FIG. 11 shows an opposite side elevation of the stent
`but the centerline of the large waveforms 15a is inclined
`in FIG. 10;
`relative to the longitudinal centerlines of the smaller
`FIG. 12 shows an end view of the stents in FIGS. 10
`waveforms, preferably at an inclination angle of approx
`and 11;
`imately 45°. In FIG. 4, the waveform is similar to that of
`FIG. 13 shows a stent mounted on a balloon-tip cath
`FIG. 3 except that the centerline of the larger wave
`eter ready for insertion into a lumen;
`forms 15b is perpendicular to the centerline of the
`FIG. 14 shows a stent being used with a graft to
`smaller waveforms 17b; in other words, the inclination
`repair a pseudo-‘aneurysm in the common femoral ar
`angle of the larger waveforms is approximately 90".
`tel'y;
`FIG. 5 shows the expanded waveform of FIG. 3
`FIG. 15 shows two stents being used with a graft to
`formed into a stent by wrapping it, in a spiral, around a
`bypass an occlusion in the femoral-popliteal artery; and
`mandril 21. Similar waveforms could also be used. For
`FIG. 16 shows a stent being used with a graft to
`instance, if the waveform of FIG. 4 were used, the
`repair an aorto-iliac aneurysm.
`longitudinal centerline of the large. waveforms would
`remain parallel to the centerline of the mandril and the
`peaks of the waveforms would be wrapped around the
`mandril, perpendicular to the centerline of the mandril.
`As shown in FIG. 5, the centerline of the large wave
`forms 15a is arranged to spiral along the length of the
`mandril 21. One side of each of the larger waveforms
`15a is arranged approximately parallel to the longitudi
`nal axis of the mandril 21, and the remaining sections of
`each of the waveforms are arranged at a small angle to
`the longitudinal axis of the mandril. (In the drawing, the
`“small” angle has been greatly exaggerated for purposes
`of illustration.) It will be appreciated that the shown
`arrangement allows the stent to be wound in a very
`tight spiral.
`By forming the above-described stent as a tight spiral
`on a mandril, the stent expands primarily in the radial
`direction, with relatively slight movement at the ends,
`as it is expanded internally in a lumen. Even greater
`radial expansion might be achieved by the wrapping the
`waveform as a circle around the mandril. However,
`such a radially-wrapped con?guration would use an
`excessive amount of ?lament per unit surface area to
`support the lumen, especially where the ?laments were
`allowed to overlap.
`In FIG. 6, each of the last three smaller waveforms
`17a (from FIG. 5) at the end of the stent is wrapped
`with its longitudinal centerline around the circumfer
`ence of the mandril. It should be noted that the peaks of
`the last three smaller waveforms (indicated in FIG. 6 by
`the letters “a”, “b” and “0”, respectively) are approxi
`mately the same distance from the edge of the mandril,
`and the fourth peak “d” as well as the ?fth peak “e” are
`slightly further away from the end of the mandril. Also,
`the end of the stent near peak “a” is connected to the
`apex of peak “d.” The result of this connection is that
`peaks “a”, “b”, and “c” are substantially equally spaced
`around the circumference of the mandril and are all at
`the approximately same distance from the end of the
`mandril.
`In practice, the connection between the loop and the
`?lament is slidable along the ?lament 11, thereby allow
`ing for radial expansion. Although this connection can
`be easily made using a loop as shown, it can also be
`made by, for example, using a bracket. The connector
`could also be made by brazing, welding, or gluing the
`end to the ?lament.
`When the above-described stent is wound around a
`mandril in the shape of a tight spiral, the non-expanded
`form of the stent provides a pro?le that is lower than
`conventional stents, and the “tines” of the non
`expanded stent are almost parallel and packed closely
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`FIG. 1 shows a ?lament 11 formed in a compressed
`planar waveform. Preferably, the ?lament 11 is made
`from 0.005—0.020 inch diameter stainless steel wire;
`however, it can be made from materials such as tita
`nium, tantalum, gold, copper and copper alloys, combi
`nations of these materials, or any other biologically
`compatible material with a low shape~memory level. (In
`the present context, a low shape-memory level implies
`that the stent will not contract to its compressed shape
`after it is inserted and internally expanded in a lumen.)
`The ?lament 11 can also be formed from several sepa
`rate strands which are wrapped or woven together.
`The compressed waveform pattern in FIG. 1 is pref
`erably formed generally in the shape of a compressed
`sinusoid, but can have any wave-like pattern. In the
`drawing, it should be noted that the waveforms at the
`ends 19 and 21 of the wire having smaller amplitudes
`than the waveforms 15 in the middle of the wire. The
`drawing shows, for example, four reduced amplitude
`peaks 17 at each of the ends 19 and 21, respectively.
`Preferably, the heights of the reduced amplitude wave
`forms 17 are one-half to two-thirds of the heights of the
`larger waveforms.
`In FIG. 2, the compressed waveforms of FIG. 1 are‘
`expanded along their longitudinal centerline into a
`nearly sinusoidal waveform by stretching the com
`pressed waveforms from their ends. (The broken line
`shows the longitudinal centerline of the expanded
`waveforms.) At both ends 19 and 21, the longitudinal
`centerline of the smaller waveforms is displaced from
`the longitudinal centerline of the waveforms near the
`middle of the wire. At one end 19, for instance, the
`centerline of the smaller waveforms 17 is displaced
`below the broken line; at the end 21, by way of contrast,
`the centerline of the smaller waveforms is displaced
`above the broken line.
`In practice, the above-described expanded wave
`forms preferably have a period of about eight millime
`ters. The larger waveforms 15 preferably have a peak
`to-peak amplitude of eight millimeters while the smaller
`waveforms 17 are one-half to two-thirds the height of
`the larger waveforms. However, other sizes may be
`used. Although all of the waveforms normally have the
`same period, they are not necessarily sinusoidal, regu
`lar, repeating, or continuous.
`FIGS. 3 and 4 show the expanded state of two alter
`native waveforms that can be used to form the above
`described stent. The period of each waveform in the
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`together. This is important because such stent can be
`accommodated through a smaller incision and, there
`fore, reduces blood loss during surgery. Furthermore,
`such a stent can provide an expansion ratio of about
`10:1, enabling it to be used in large arteries.
`As shown in FIG. 12, the connections at the ends of
`the ?lament 11 create a circular hoop near each end of
`the stent with no sharp edges, or points, protruding
`from the perimeter to project into a lumen or to catch
`on the balloon or plaque inside of a vessel. Also, because
`the centerline of the smaller waveforms is arranged
`along the circumference of the stent, the end hoops
`allow the stent to ?t snugly inside the lumen and pre
`vent migration. In other words, in this arrangement, the
`hoops expand radially to lock the expanded stent in
`place in a lumen while permitting only limited longitu
`dinal expansion.
`FIG. 7 shows a preferred alternative waveform
`which can be used in making a stent. The waveform of
`FIG. 7 is formed from a series of U-shaped bends hav
`ing substantially straight legs on each side of the curved
`portion of each “U”. The legs are preferably parallel;
`but they may also be formed at angles to each other.
`The curved portions are preferably semi-circular; how
`ever, other shapes of curves can be used to connect the
`straight legs in each bend. The curved portions may
`have the same or different sizes. It is also preferred that
`the curved portions are connected to the straight por
`tions at the tangent of each curve in order to prevent
`any discontinuities in the length of the ?lament.
`FIG. 8 shows the relative positions of the U-shaped
`bends for each component section A, B, C of the pre
`ferred alternative waveform of FIG. 7. Sections A and
`C of the waveform are upside down mirror images of
`each other. The broken lines in FIG. 8 are reference
`35
`lines which are preferably equally spaced and parallel.
`However, it is also possible to form the stent so that the
`top and bottom reference lines are parallel to each other
`but not equally spaced from or parallel to the other
`reference lines.
`De?ning the distance between the reference lines as
`one unit of measurement, then each of the U-shaped
`bends in end sections A and C each have a different
`length. For example, U-shaped bend 1 is one unit long
`while U-shaped bend 3 is three units long. Similarly,
`45
`U-shaped bend 7’ is one unit long while U-shaped bend
`5' is three units long. In contrast, each of the waveforms
`in section B has one long leg which is four units long
`and one short leg which is three units long. For exam
`ple, the left leg of U-shaped bend 5 is four units long
`while the right leg is three units long as measured be
`tween the reference lines. Each of the curved portions,
`except for the ends of the ?lament, are preferably semi
`circular with a diameter of one unit. The curved portion
`at each end of the ?lament is preferably one half of the
`semicircular arc. However, other shapes and propor
`tions may also be used to appropriately size the stent.
`As shown in FIG. 9, the stent is formed by wrapping
`the waveform of FIG. 7 around a mandril which is
`preferably cylindrical. However, mandrils with other
`shapes could also be used. The waveform is preferably
`wrapped around the mandril so that the legs of each
`U-shaped bend are parallel to the axis of the mandril,
`which in turn results in each U-shaped bend bisected by
`the longitudinal axis of the mandrel. In this con?gura
`tion, a single wire may be formed into an extremely
`rigid tubular structure with very little material to dis
`turb ?ow inside the lumen. However, the waveform
`
`6
`might also be wrapped around the mandril in a slightly
`spiral manner. Once the waveform is wrapped around
`the mandril, the outside edge of curves on the same
`reference line will be arranged back-to-back adjacent to
`(or overlapping with) each other. As shown in FIGS.
`7-10, the stent is made from a single strand of continu
`ous wire which does not cross over itself over the
`length of stent. For example, the outside edge of curve
`1 will be back-to-back with the outside edge of curve 1’.
`Similarly, the outside edge of curve 7 will be adjacent to
`curve 7 ’. The outside edges of these U-shaped bends can
`then be fastened together by any conventional means
`such as welding, brazing, soldering, or gluing.
`FIGS. 10, 11, and 12 illustrate the stent which is
`formed by wrapping the waveform of FIG. 8 around a
`circular mandril with the reference lines arranged on
`the circumference of the mandril. It will be apparent
`that each of the labeled U-shaped bends on parallel
`reference lines in FIG. 8 have been connected in FIGS.
`10 and 11. For example, U-shaped bend 7’ is shown to
`be connected to U-shaped bend 7 at the top of FIG. 10.
`Although it is preferred that the U-shaped bends are
`welded, it is also possible to form the connecting por
`tions of the ?lament from a single piece of material in
`order to eliminate the need for connecting each of the
`appropriate U-shaped bends. The ends of the ?lament
`are also connected back to the ?lament and trimmed in
`order to remove any excess filament precluding from
`the free end.
`The rigidity of the structure may be controlled by
`welding less than all of the adjacent curved portions.
`For example, a stent with only half the U-shaped por
`tions welded together would be approximately half as
`rigid as a stent with all the tangent points welded to
`gether. Of course, the stent can also be used without any
`connections between adjacent curved portions.
`The lowest possible pro?le (i.e., diameter) is provided
`by arranging the long leg of each U-shaped bend paral
`lel to the axis of the catheter before it is inserted into a
`lumen. This arrangement increases the diameter to
`which the stent can be expanded without, at the same
`time, decreasing the end-to-end length of the stent. By
`increasing or decreasing the length of the long leg of
`each U~shaped bend, one can alter the expansion ratio
`without altering the pro?le. Consequently, a nearly
`unlimited circumferential expansion ratio may be cre
`ated without contracting the stent along its longitudinal
`axis. The expansion ratio is therefore nearly indepen
`dent of this profle.
`When expanded, each of the U-shaped portions in the
`stent may assume a rhomboidal pattern where the legs
`of each U-shaped bend are no cell longer parallel. As
`shown in FIGS. 10 and 11, a plurality of rhomboidal
`cells are distributed around the cylindrical surface de
`?ned by the stent. Furthermore, because the legs alter~
`nate in length over the middle portion of the waveform
`as shown in FIG. 8, each adjacent leg of each rhomboi
`dal cell differs in length. The expansion ratio of the stent
`may therefore exceed 10 to 1 in terms of the expanded
`diameter versus the unexpanded diameter of the stent.
`Consequently, the outside surface of the stent touching
`the vessel is small while the effective support area is
`very large. This feature dramatically reduces the possi
`bility of causing any hemodynamic disturbances inside
`the vein or artery because of the stent. The large expan
`sion ratio also allows the stent to be used with smaller
`incisions. Moreover, this con?guration allows the stent
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`The foregoing has described the principles, preferred
`to be ?exible in the radial direction in order to accom
`modate the pulsation of an artery.
`embodiments and modes of operation of the present
`The stent may also be coated with anti-thrombolytic
`invention. However, the invention should not be con
`agents in order to limit the thrombotic formation which
`strued as limited to the particular embodiments dis
`often accompanies angioplasty.
`cussed. Instead, the above-described embodiments
`FIGS. 13-16 illustrate a typical stent of which could
`should be regarded as illustrative rather than restrictive,
`represent any one of the embodiments described above.
`and it should be appreciated that variations may be
`FIG. 13 shows a typical stent mounted on a 4/5 F bal
`made in those embodiments by workers skilled in the art
`loon (4-10 mm) with a 6/7 F sheath. The apparatus of
`without departing from the scope of present invention
`FIG. 13 is preferably used with a 0.078—0.09l guide
`as de?ned by the following claims.
`sheath. FIG. 14 shows the stent, inside a graft, being
`What is claimed is:
`used to repair a pseudo-aneurysm in a common femoral
`1. A stent having a longitudinal axis comprising:
`artery. The stent 8 is placed inside graft 9 which blocks
`a continuous ?lament shaped into a waveform pattern
`off pseudo-aneurysm 10. Although the stent is shown to
`having a plurality of substantially straight legs
`be completely inside graft 9, it may also extend outside
`connected by U-shaped bends, consecutive ones of
`the edges of the graft in order to provide additional
`said straight legs varying in length, said waveform
`support for the incisions at the end of the graft.
`pattern being spirally wrapped about said axis to
`FIG. 15 shows two stents being used at each end of a
`de?ne a cylindrical surface in which a plurality of
`graft to bypass an occlusion 12 in, for example, the
`said U-shaped bends are in tangential contact;
`femoral-popliteal artery. FIG. 16 illustrates how three
`said straight legs being substantially parallel to said
`stents can be used with a branched graft to repair an
`longitudinal axis when the stent is in a radially
`aorto-iliac aneurysm 13. The graft 9 is placed inside the
`compressed state;
`aneurysm and secured at one end to the aorta 14. The
`said U-shaped bends being substantially bisected by
`other ends of the graft are similarly stented to iliac
`said longitudinal axis; and
`branches 16.
`a plurality of pairs of said U-shaped bends that are in
`FIG. 16 also illustrates how the catheter holding the
`tangential contact being attached together in a
`stent can be. used to insert the stent 8 inside a lumen.
`non-overlapping manner so that said cylindrical
`Typically, a short incision is made in the lumen (for
`surface includes a plurality of rhomboidal cells
`example, a vein or artery) and the stent, which is
`bounded on all four sides by said substantially
`mounted on the balloon, is then slipped into the incision.
`straight legs.
`When the stent is in place, the balloon is expanded in
`order to expand the stent against the inside walls of the
`2. The stent of claim 1 wherein said continuous ?la
`lumen. Once the stent is in place, the balloon is de?ated
`ment is a single strand of wire and the stent is made
`and removed through the inside of the stent and the
`without said wire crossing over itself.
`incision in order to leave the stent in place.
`35
`3. The stent of claim 2 wherein said consecutive ones
`Various advantages of the present invention can now
`of said straight legs alternate in length over a portion of
`be understood. For example, the above-described stent
`said waveform pattern.
`uses substantially less material than conventional stents
`4. A stent having a longitudinal axis comprising:
`(especially knitted ones with overlapping wires) and,
`a continuous ?lament shaped into a waveform pattern
`therefore, introduces a substantially lesser quantity of
`40
`having a plurality of substantially straight legs
`foreign material into a lumen. The stent also provides a
`connected by U-shaped bends, consecutive ones of
`maximum amount of structural support with a minimum
`said straight legs varying in length, said waveform
`amount of material. As another example, the above
`pattern being wrapped about said axis to de?ne a
`described stent connects its ?lament ends back onto the
`cylindrical surface; and
`?lament to prevent thrombosis in blood vessels or dam
`45
`a plurality of pairs of said U-shaped bends being at
`age to any type of a lumen wall such as is caused by
`tached together in a non-overlapping manner so
`stents that have loose wire ends that protrude into a
`that said cylindrical surface includes a plurality of
`lumen.
`rhomboidal cells bounded on all four sides by said
`Another advantage of the above-described stent is
`substantially straight legs.
`that it provides substantial radial expansion with only
`5. The stent of claim 4 wherein said straight legs are
`limited longitudinal migration and, therefore, reduces
`substantially parallel to said axis when the stent is in a
`the problem of migration inside a lumen. More particu
`radially compressed state.
`larly, the hoops and end component sections at each end
`6. The stent of claim 5 wherein said waveform pattern
`of the above-described stent reduce migration by secur
`is spirally wrapped about said axis.
`ing the stent inside of a lumen. In the preferred embodi
`7. The stent of claim 5 wherein said waveform pattern
`ment, the hoops, end component sections, as well as the
`includes a portion in which at least four successive
`spiral shape of the stent itself are oriented to inhibit
`straight legs alternate in length.
`longitudinal growth of the stent during radial expan
`8. The stent of claim 4 wherein said continuous ?la
`sion.
`ment is a single strand of wire and the stent is made
`Yet another advantage of the above-described stent is
`without said wire crossing over itself.
`that it provides sufficient ?exibility to allow implanta
`9. A stent having a longitudinal axis comprising:
`tion in tortuous lumens and in applications where lumen
`bending is required. This overcomes the problem with
`a continuous ?lament shaped into a waveform pattern
`having a plurality of substantially straight legs
`conventional stents that are so stiff that they are dif?cult
`to negotiate through a tortuous vessel during implanta
`connected by U-shaped bends, consecutive ones of
`said straight legs varying in length, said waveform
`tion. Furthermore, a stiff stent can cause damage to
`pattern being spirally wrapped about said axis to
`certain vessels, such as those around joints, that require
`flexibility.
`define a cylindrical surface;
`
`30
`
`50
`
`55
`
`65
`
`011
`
`

`
`9
`said straight legs being substantially parallel to said
`longitudinal axis when the stent is in a radially
`compressed state; and
`said U-shaped bends being substantially bisected by
`said longitudinal axis.
`10. The stent of claim 9 wherein said consecutive
`ones of said straight legs alternate in length over a por
`tion of said waveform pattern.
`11. The stent of claim 10 wherein at least one pair of
`said U-shaped bends is attached together to de?ne an
`attachment.
`12. The stent of claim 11 wherein said at least one pair
`of said U-shaped bends is attached together in a non
`overlapping manner and wherein a plurality of said
`
`10
`attachments result in the stent having at least one rhom
`boidal cell bounded on all sides by said straight legs.
`13. The stent of claim 12 wherein said continuous
`?lament is a single strand of wire and the stent is made
`without said wire crossing over itself.
`14. A method of forming a stent comprising the steps
`Of:
`forming a continuous ?lament into a waveform pat
`tern having a plurality of substantially straight legs
`connected by U-shaped bends, consecutive ones of 7
`said straight legs alternating in length;
`wrapping the waveform pattern around a cylindrical
`mandrel so that some of the U-shaped bends are
`arranged back to back in tangential contact; and
`connecting in a non-overlapping manner at least some
`of the U-shaped bends in tangential contact.
`* * * * *
`
`5,370,683
`
`10
`
`25
`
`30
`
`35
`
`45
`
`55
`
`65
`
`012