United States Patent [19]
`MacGregor
`
`Patent Number:
`[11]
`[45] Date of Patent:
`
`4,994,071
`Feb. 19, 1991
`
`[54] BIFURCATING STENT APPARATUS AND
`METHOD
`
`4,856,5l6 8/1989 Hillstead ......................... .. 604/96 X
`4,913.141 4/1990 Hillstead ....................... 1 606/194 x
`
`[75] Inventor: David C. MacGregor, Miami, Fla.
`,
`_
`_
`_
`_
`[73] Asslgnee: Cord“ corporatlon’ Mlaml’ Fla‘
`[21] Appl. No.: 354,799
`[22] Filed:
`May 22, 1989
`[51]
`1111. 01.5 ...................... .. A61M 29/00; A61F 2/06
`[52] US. c1. ............................ .. 606/194; 606/192
`[53] Field of Search ____________ __ 606/191, 192, 198’ 200’
`606/194, 96, 151’ 153; 623/1, 12
`_
`References Clted
`[15 PATENT DOCUMENTS
`
`[56]
`
`gig?“ a a1‘ """"""""
`4’733’665 3/1988 palmazy
`606/191 X
`
`4,795,465 l/l989 Marten 1 . . . . . . .
`. . . 1 . .. 623/12 X
`4,830,003 5/1989 Wolff et al. ................... .. 606/l9l
`4,842,575 6/1989 Hoffman, Jr. et al. ........... .. 623/1 X
`
`Primary Examl'neP-Roben A- Hafer
`Assistant Examiner—Kevin G. Rooney
`Attorney, Agent, or Firm-Watts, Hoffmann, Fisher &
`Heinke CO.
`ABSTRACT
`[57]
`A bifurcating Stem for insertion in“) a bifurcating vessel
`Such as a blood vessel‘ The Stem can be expanded from
`an insertion con?guration to an implanted con?guration
`by the application of radially outward forces against a
`series of interconnected wire loops that make up the
`stent. The preferred and disclosed method of stent im
`plantation is accomplished with the use of a balloon
`catheter that expands the stent into contact with inner
`walls of the vessel. The balloon is then de?ated and
`withdrawn from the vessel, leaving the stent implanted
`
`wlthm the Vessel
`
`16 Claims, 3 Drawing Sheets
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`001
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`

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`US. Patent
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`Feb.19, 1991
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`Sheet 1 Ora
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`4 4,994,071
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`' 99:93.59l1
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`FIG.IA
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`002
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`US. Patent
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`Feb. 19, 1991
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`Sheet 2 of 3
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`4,994,071
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`5 s , A Q 2 1 F
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`B 2 G
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`l??g ?. ................ .. a . a
`m C 1. .. .... .. 2 .
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`1,,wamgw??5, ..... .. w 6 m H
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`FIG. 20 FIG.2E
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`US. Patent
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`Feb. 19, 1991
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`Sheet 3 of 3
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`4,994,071
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`Fla-5A
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`F|G.3B
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`lama;
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`FIG.3D
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`1
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`4,994,071
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`BIFURCATING STENT APPARATUS AND
`METHOD
`
`TECHNICAL FIELD
`The present invention relates to an endoprosthesis
`device for implantation within a body vessel, typically a
`blood vessel.
`'
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`20
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`2
`distingishing feature of the inserts disclosed in this pa
`tent is the ability to take apart the insert by pulling a free
`end ofa thread that forms the insert. This insert is surgi
`cally placed within a subject and no mention is made
`concerning the non-surgical placement of such an insert
`within a vessel.
`U.S. patent application Ser. No. 240,000 entitled “Ra
`dially Expandable Endoprosthesis and the Like" dis
`closes a generally cylindrical stent formed from a wire
`that is bent into a series of tight bends and then spirally
`wound about a cylindrical mandrel to form the stent. If
`a radially outward force is applied to the stent the sharp
`bends in the wire tend to straighten and the stent diame
`ter enlarges. One technique for implanting this stent
`uses a de?ated balloon catheter to position the stent
`within a vessel. Once the stent is properly positioned
`the balloon is in?ated to press the stent against the inner
`wall linings of the vessel. The balloon is then deflated
`and withdrawn from the vessel, leaving the stent in
`place.
`
`DISCLOSURE OF THE INVENTION
`
`BACKGROUND ART
`A type of endoprosthesis device, commonly referred
`to as a stent, is placed or implanted within a blood vessel
`for treating occlusions, stenoses, or aneurysms in the
`blood vessel. These devices are implanted within the
`vascular system to reinforce collapsing, partially oc
`cluded, weakened, or abnormally dilated sections of the
`blood vessel. Stents also have been successfully im
`planted in the urinary tract or the bile duct to reinforce
`those body vessels.
`One of the drawbacks of conventional stents is that
`they are produced in a straight tubular con?guration.
`The use of such a stent to treat disease at or near a
`branch or bifurcation of a blood vessel runs the risk of
`compromising the degree of patency of the primary
`vessel and/ or its branches or bifurcation. This may
`occur as a result of several problems such as displacing
`diseased tissue, vessel spasm, dissection with or without
`intimal ?aps, thrombosis, and embolism.
`One common procedure for implanting the endopros
`thesis or stent is to ?rst open the region of the vessel
`with a balloon catheter and then place the stent in a
`position that bridges the weakened portion of the vessel.
`' Prior art patents refer to the construction and design
`of both the stent as well as the apparatus for positioning
`the stent within the vessel. One representative patent is
`U.S. Pat. No. 4,140,126 to Chaudhury which issued
`Feb. 20, 1979. This patent discloses a technique for
`positioning an elongated cylindrical stent at a region of
`an aneurysm to avoid catastrophic failure of the blood
`vessel wall. The ’l26 patent discloses a cylinder that
`expands to its implanted con?guration after insertion
`with the aid of a catheter
`A second prior art patent to Dotter U.S. Pat. No.
`4,503,569 which issued Mar. 12, 1985 discloses a spring
`stent which expands to an implanted con?guration with
`a change in temperature. The spring stent is implanted
`in a coiled orientation and heated to cause the spring to
`expand.
`U.S. Pat. No. 4,733,665 to Palmaz which issued Mar.
`29, 1988 discloses a number of stent con?gurations for
`implantation with the aid of a catheter. The catheter
`includes a mechanism for mounting and retaining the
`vascular prosthesis or stent, preferably on an in?atable
`portion of the catheter The stent is implanted by posi
`tioning it within the blood vessel and monitoring its
`position on a viewing monitor. Once the stent is prop
`erly positioned, the catheter is expanded and the stent
`separated from the catheter body. The catheter can then
`be withdrawn from the subject, leaving the stent in
`place within the blood vessel.
`U.S. Pat. No. 4,413,989 to Schjeldahl et al. which
`issued Nov. 8, 1983 discloses a variety of balloon cathe
`ter constructions. FIG. 5 of this patent discloses a bifur
`cating expander for insertion into diverging branches of
`a subject blood vessel.
`65
`U.S. Pat. No. 3,993,078 to Bergentz et al. discloses an
`insert for use in vascular surgery. The embodiment of
`this insert disclosed in FIG. 2 forms a “Y” tube. A
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`The present invention concerns a stent and more
`particularly a bifurcating stent for insertion into a
`branching vessel of a subject. A stent constructed in
`accordance with the invention includes structure that
`de?nes a ?rst ?ow path for ?uid to ?ow through the
`stent. More particularly, a series of interconnected
`loops extend axially along and bound this ?rst ?uid ?ow
`path.
`Additional structure, preferably constructed using a
`second series of interconnected loops, de?nes a second
`branching ?uid ?ow path. A ?exible interconnection
`joins the structure that de?nes the ?rst and second ?ow
`paths. By proper bending of the ?exible interconnection
`the ?rst and second ?uid ?ow paths can be made to
`conform to a shape of the vessel into which the bifurcat
`ing stent is inserted.
`The bifurcating stent is constructed from a material
`that allows the stent to be expanded from an initial
`shape which can be inserted into a branching vessel to
`an expanded shape ?xed within the branching vessel. A
`balloon catheter is preferably used to expand the stent
`by application of outward forces against the series of
`loops that make up the stent. To deposit the bifurcating
`stent within the subject, the balloon is expanded to
`bring the stent into contact with the inner walls of the
`vessel and then de?ated, leaving the stent in place.
`A preferred use for a bifurcating stent constructed in
`accordance with the present invention is for insertion
`into a branching blood vessel. A stent constructed in
`accordance with the present invention is typically in
`tended for use in the coronary vasculature (the right,
`left common, left anterior descending, and circum?ex
`coronary arteries and their branches) and the peripheral
`vasculature (branches of the carotid, aorta, femoral,
`popliteal, etc. arteries).
`A stent constructed in accordance with the invention
`is suitable for implantation in other branching vessels of
`a subject. By way of example the invention has utility
`for implantation in the gastrointestinal system, the tra
`cheobronchial tree, the biliary system and the genitouri
`nary system.
`From the above it is appreciated that one object of
`the invention is a bifurcating stent which can be ex
`panded from an insertion to an in use con?guration.
`This and other object advantages and features of the
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`4,994,071
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`3
`invention will become better understood from a de
`tailed description of the invention which is described in
`conjunction with the accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective view of a bifurcating stent
`constructed in accordance with the invention;
`FIG. 1A is plan view of the FIG. 1 bifurcating stent
`illustrating a backbone structure that interconnects
`branch portions of the stent;
`FIG. 2A is a schematic depiction of a blood vessel
`showing a branching juncture of that vessel with two
`guidewires in place;
`FIG. 2B shows the branching blood vessel of FIG.
`2A wherein a stent constructed in accordance with the
`invention has been inserted;
`FIG. 2C shows a balloon in?ated to bring a portion of
`a bifurcating stent into contact with inner walls of the
`branching blood vessel;
`FIG. 2D shows one leg or branch of the bifurcating
`stent expanded into contact with one branch of the
`blood vessel;
`FIG. 2E shows a second branch or leg of the bifurcat
`ing stent expanded into contact with the blood vessel
`wall;
`FIG. 2F shows the stent placed within the blood
`vessel with the balloon catheter(s) used in deploying the
`stent withdrawn from the blood vessel;
`FIGS. 3A-3D show an alternate mounting technique
`for a bifurcating stent wherein the stent is mounted on a
`balloon catheter which is in?ated to bring the entire
`stent into contact with the inner wall members of the
`branching vessel.
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`20
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`The lattice 16 is preferably constructed from a ?exi
`ble wire 24 that connects this lattice 16 to the lattice 22.
`The same wire 24 forms the series of interconnected
`loops 12' that form the lattice 22.
`A second wire 26 interconnects the cylindrical lattice
`16 with the cylindrical lattice 20. The wire 26 forms a
`backbone 28 extending axially along the length of the
`lattice 16 that extends away from the lattice l6 and is
`used to construct the interconnecting loops 12" of the
`lattice 20. Appropriate bending of the portions of the
`wires 24, 26 interconnecting the lattices 16, 20, 22 al
`lows the angles between ?ow paths to be properly ori
`ented before the stent 10 is inserted into a vessel.
`The loops 12a, 12b of the lattices 20, 22 closest to the
`lattice 16 are not interconnected in the preferred design.
`A small loop of wire could be used to interconnect these
`lattices 20, 22. Also, backbones similar to the backbone
`28 could be added to the two lattices 20, 22.
`Other techniques are known in the art for construct
`ing cylindrical expansible forms for use in stent con
`struction. As an additional example, US. Pat. applica
`tion Ser. No. 240,000 entitled “Radially Expandable
`Endoprosthesis and the Like” discloses a stent con
`structed from a wire which spirals around a ?uid ?ow
`path in a series of interconnected loops. A bifurcating
`stent which de?nes branching flow paths such as those
`depicted in FIG. 1 can also be constructed using inter
`connected spirally loops as disclosed in this pending
`patent application.
`The bifurcating stent of the invention can also be
`constructed using a tubular passageway design similar
`to that disclosed in the Palmaz ‘665 patent. Other stent
`designs and a number of suitable materials can be used
`in constructing a bifurcating stent in accordance with
`the invention.
`A method of implantation for a bifurcating stent is
`depicted in FIGS. 2A-2F. For ease in illustration, the
`stent disclosed in these ?gures has been schematically
`depicted as a series of spiraling interconnected loops
`such as that disclosed in ’O00 patent application. As seen
`in FIG. 2A, a main trunk 50 ofa blood vessel splits into
`two branches 50a, 50b. Two guide wires 52, 54 have
`been routed through a subject cardiovascular system
`and into the branches 50a, 50b respectively. Techniques
`for routing guidewires into a subject are well known in
`the prior art.
`Once the two guidewires 52, 54 have been inserted
`into the position shown in FIG. 2A, a bifurcating stent
`10' (FIG. 2B) is slipped over the proximal ends of the
`guidewires 52, 54 and routed to the branches of the
`blood vessel. A bifurcating stent 10 such as that de
`picted in FIG. 1 is suitable for implantation in the
`branching vessel 50 depicted in FIG. 2B. The two
`branching cylindrical lattices of the stent 10 are routed
`separately over the guidewires 52, 54 and guided with
`the help of a guide catheter into the subject until the
`FIG. 2B position of the stent 10’ is achieved.
`As seen in FIG. 2B, in the inserted con?guration, the
`stent 10’ is tightly coiled and therefore passes freely into
`the subject blood vessel. The stent 10’ is typically in
`serted through a guide catheter (not shown) so that the
`coils or loops that form the bifurcating stent do not
`engage the inner walls of the blood vessel. To ?x the
`stent 10’ in place, one guidewire is removed and a bal
`loon catheter having a distally located balloon 60 is
`inserted into the stent’s cylindrical lattice 16' and in
`?ated to bring the cylindrical lattice 16’ into contact
`with the blood vessel walls. The lattice 16' engages the
`
`BEST MODE FOR PRACTICING THE
`INVENTION
`Turning now to the drawings, FIG. 1 depicts a bifur
`cating stent 10 for implantation in a subject vessel.
`While the stent 10 has use in conjunction with other
`subject vessels, the preferred embodiment of the stent is
`described in conjunction with use with a blood vessel
`wherein the stent 10 is utilized for reinforcing the exist
`ing vascular structure.
`The stent of FIG. 1 is shown in a contracted state
`prior to insertion within a subject. Copending patent
`application entitled Endovascular Stem Apparatus and
`Method which was ?led Jan. 9, 1989 under application
`Ser. No. 07/295,129 to Hillstead discloses a technique
`for fabricating an in-line stent that can be expanded after
`it is controllably inserted within a subject by means of a
`balloon catheter The disclosure of this copending pa
`tent application is incorporated herein by reference.
`The stent 10 includes a main or trunk portion con
`structed from a series of generally parallel oriented
`loops 12 interconnected by a sequence of half-hitch
`connections 14 (FIG. 1A) which extend along an axial
`dimension. In combination the series of loops 12 form a
`generally cylindrical lattice or matrix 16 that de?nes a
`?rst ?ow passageway along the direction of the arrow
`16A of FIG. 1.
`Two additional cylindrical lattices 20, 22 having di
`ameters less than the lattice 16 are similarly constructed
`from a sequence of loops interconnected by a half
`hitches which de?ne ?ow passageways (indicated by
`arrows 20A, 22A in FIG. 1) extending away from the
`?rst ?ow passageway at angles dependent upon the
`vessel structure into which the stent 10 is inserted. .
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`main trunk portion of the blood vessel so that during
`fabrication of the stent 10’ the initial diameter of the
`loops that make up the lattice 16’ may be chosen to be
`greater than the two branching lattices.
`FIGS. 2D and 2E show a smaller dilatation balloon
`62 that is routed through the expanded cylindrical lat
`tice 10' and placed into one and then the other branch of
`the stent 10’ over a single guidewire. When the balloon
`62 is in?ated the two branch lattices 20',22' of the stent
`expand into contact with the branching blood vessels
`50a, 50b respectively. FIG. 2F shows the fully deployed
`branching stent 10’ supporting the lumen of both the
`main trunk 50 and two branches 50a, 50b of the blood
`vessel.
`FIG. 3A shows a typical blood vessel bifurcation,
`again with a guidewire positioned in each of the two
`branches of the vessel. FIG. 3B shows a bifurcated
`dilatation balloon 70 over which a bifurcated stent 10"
`has been compressed. Two guidewires 52, 54 are used to
`guide the branching dilatation balloon plus the bifur
`cated stent into the vessel. FIG. 3C shows that the fully
`dilated bifurcated balloon 70 has deployed the bifur
`cated stent into place. FIG. 3D shows the fully de
`ployed bifurcated stent 10” with the dilatation balloon
`removed.
`A branching or bifurcated stent may be deployed in
`other ways without resort to a balloon catheter. For
`example, a bifurcated spring stent passed over two
`guidewires and contained within a guide catheter could
`be deployed by passing the guide catheter towards the
`bifurcation of the vessel, at which time the stent would
`be ejected into place by advancing a smaller inner cath
`eter through the guide catheter into contact with the
`stent. The method of deployment of a branching stent
`will largely depend on the design of the stent and the
`success of the different deployment techniques for dif
`ferent branching vessel con?gurations.
`The stent may be produced from a variety of materi
`als, either alone or in combination, such as metals or
`alloys (stainless steel, titanium, tantalum, nitinol, El
`giloy, NP35N) that can vary in their springiness, malle
`ability, and response to temperature; polymers (poly
`urethane, polyether sulfone, polyimide, polycarbonate,
`polyethylene, etc.) that can vary in their ability to bi
`oabsorb or biodegrade; carbon; and ceramics. Various
`surface treatments can be applied to render the stents
`more biocompatible (pyrolytic carbon, hydrogels, etc.)
`and to provide for the elution of drugs (heparin, anti
`platelet agents, platelet-derived growth factor, antibiot
`ics, steroids, etc.).
`The present invention has been described with a de
`gree of particularity. It is the intent that the invention
`include all modi?cations and alterations from the dis
`closed embodiments that fall within the spirit of slope of
`55
`the appended claims.
`I claim:
`1. A bifurcating stent for placement in a subject vessel
`comprising:
`a ?rst generally cylindrical matrix of ?lament mate
`rial forming a series of interconnected loops that
`de?ne a ?rst ?ow path for ?uid ?ow; and a second
`generally cylindrical matrix of ?lament material
`forming a series of interconnected loops that de?ne
`a second branching ?ow path; said ?rst and second
`matrices connected by a ?exible interconnecting
`member bent to de?ne an angle between the ?rst
`and the branching flow paths;
`
`6
`said matrices constructed from a material that allows
`that stent to conform to an insertion con?guration
`and expand to an in place con?guration.
`2. The bifurcating stent of claim 1 additionally com
`prising a third generally cylindrical matrix of ?lament
`material forming a series of interconnected loops that
`de?ne a third ?ow path wherein one of the three matri
`ces has a larger diameter to de?ne a trunk matrix and
`further wherein two smaller diameter matrices are con
`nected to the trunk matrix by ?exible interconnecting
`members bent to de?ne angles between the trunk matrix
`and the two smaller diameter matrices.
`3. The bifurcating stent of claim 1 wherein adjacent
`loops along the length of the ?rst and second matrices
`are interconnected by half hitch junction and end loops
`of the ?rst and second matrices are connected by the
`?exible interconnecting member.
`4. The bifurcating stent of claim 1 wherein the loops
`of both the ?rst and the second matrix comprise a series
`of spiralling loops.
`5. A bifurcating stent for placement in a subject vessel
`comprising:
`a ?rst series of ?lament loops that de?ne a ?rst ?ow
`path for blood ?ow through the stent; and at least
`one additional series of ?lament loops which de?ne
`a second branching flow path; said ?rst and addi
`tional series of loops connected by a ?exible inter
`connecting member which is bent to de?ne an
`angle between the ?rst and the branching ?ow
`paths;
`said ?lament loops constructed from a material that
`allows the stent to conform to an insertion con?gu
`ration and expand to an inplace con?guration in
`contact with inner walls of a branching vessel.
`6. The stent of claim 5 wherein adjacent loops of both
`the ?rst and the additional series of ?lament loops are
`interconnected by half hitch junctions.
`7. The stent of claim 5 wherein the ?lament loops of
`both the ?rst and the additional series of ?lament loops
`comprise a series of spiralling loops.
`8. A method for implanting a branching stent having
`?rst and second branching portions connected together
`at a junction comprising the steps of:
`routing a ?rst guidewire into a subject to a branch
`location and inserting the ?rst guide wire into a
`?rst branch vessel at the branch location;
`routing a second guidewire into a subject to said
`branch location and inserting the second guidewire
`into a second branch vessel at the branch location;
`inserting the branching stent to the region of the
`branch location and routing the ?rst and second
`branching portions of said stent into the ?rst and
`second branch vessels;
`expanding the ?rst branching portion of said stent
`into contact with an inner wall of one branch ves
`sels;
`expanding the second branching portion of said stent
`into contact with an inner wall of a second branch
`vessel; and
`withdrawing the ?rst and second guidewires, leaving
`said stent at the branch location.
`9. The method of claim 8 wherein the step of inserting
`the branching stent is performed by mounting the
`branching stent to a bifurcating balloon located at the
`distal end of an insertion catheter, routing the balloon
`and stent to the branch location, and wherein the step of
`expanding the ?rst and second branching portions is
`performed by in?ating the bifurcating balloon to bring
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`the stent into contact with the inner wall of the ?rst and
`second branch vessel, said method including an addi
`tional step of de?ating the bifurcating balloon and re
`tracting the insertion catheter.
`10. A method for implanting a branching stent having
`a main stent portion and ?rst and second branching
`stent portions connected together at a junction compris
`ing the steps of:
`routing a ?rst guidewire into a subject to a branch
`location of a main vessel and inserting the ?rst
`guidewire into a ?rst branch vessel at the branch
`location;
`routing a second guidewire into a subject to said
`branch location and inserting the second guidewire
`into a second branch vessel at the branch location;
`inserting the branching stent into the subject to a
`region of the branch location and routing the ?rst
`and second branching portions of said stent into the
`?rst and second branch vessels leaving a main stent
`portion within the main vessel;
`causing the stent portions to come into contact with
`inner walls of the vessel; and
`withdrawing the ?rst and second guidewires to leave
`said stent at the branch location.
`11. The method of claim 10 wherein the step of insert
`ing the branching stent is performed by mounting the
`branching stent to a bifurcating balloon located at the
`distal end of an insertion catheter, routing the bifurcat
`ing balloon and branching stent to the branch location,
`and wherein the step of causing the stent portions to
`come into contact with inner walls of the vessel is per
`formed by in?ating the bifurcating balloon to bring the
`stent into contact with the inner walls of the vessel, said
`method including the additional steps of de?ating the
`bifurcating balloon and withdrawing the insertion cath
`eter.
`12. The method of claim 10 wherein the step of caus
`ing the stent portions to come into contact with inner
`walls of the vessel is performed by successively routing
`an appropriately dimensioned balloon into the main
`vessel and the ?rst and second branch vessels and in?at
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`ing the balloon to expand the main, ?rst and second
`branching stent portions.
`13. A method for implanting a stent having a main
`portion and ?rst and second branching portions con
`nected together at a junction to form a branching stent
`comprising the steps of:
`routing a guidewire into a subject to a branch vessel
`location;
`inserting the branching stent to the branch vessel
`location by advancing the branching stent along
`the guidewire and inserting the ?rst and second
`branching portions of said stent into ?rst and sec
`ond branch vessels leaving the main portion of the
`stent within a main vessel;
`causing the main, ?rst, and second branching portions
`of said stent to come into contact with inner walls
`of the branching and main vessels; and
`withdrawing the guidewire from the subject to leave
`said stent at the branch vessel location.
`14. The method of claim 13 wherein the step of insert
`ing the branching stent is performed by mounting the
`branching stent to a bifurcating balloon located at a
`distal end of an insertion catheter, routing the bifurcat
`ing balloon and branching stent into the subject, and
`wherein the bifurcating balloon is in?ated to bring the
`stent into contact with inner walls of the main and the
`?rst and second branch vessels, said method including
`the additional steps of de?ating the balloon and with
`drawing the insertion catheter.
`15. The method of claim 13 wherein the step of caus
`ing the main, ?rst, and second branching portions to
`come into contact with inner walls of the vessels is
`performed by sequentially routing an appropriately
`dimensioned dilation balloon into the main, ?rst and
`second branching portions of the stent and inflating the
`balloon to expand the main, ?rst and second branching
`portions.
`16. The method of claim 13 wherein as the branching
`stent is inserted it is in a contracted con?guration and
`wherein the stent is expanded to bring it into contact
`with the inner walls of the main and branch vessels.
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