Ulllted States Patent [19]
`Jendersee et al.
`
`USOO5836965A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,836,965
`Nov. 17, 1998
`
`[54] STENT DELIVERY AND DEPLOYMENT
`METHOD
`[76] Inventors: Brad Jendersee; Robert Lashinski,
`both of 5345 Skylane Blvd., Santa
`Rosa, Calif. 95403
`
`5,571,135 11/1996 Fraser et al. ............................ .. 604/96
`Primary Examiner—Michael BuiZ
`2:01:36? ZZZZMZ;YEEECEZFSSL Klein
`’
`’
`'
`[57]
`ABSTRACT
`
`_
`21 A l. N .. 478 192
`0
`[
`1
`pp
`’
`[22]
`Filed:
`Jun. 7, 1995
`
`Related US- Application Data
`_
`_
`_
`[63] contlnuatlon'ln'part of Sen N°~ 3267023: Oet- 19: 1994:
`abandoned‘
`[51] Int. Cl.6 .................................................. .. A61M 29/00
`[52] US. Cl. ............................ .. 606/198; 606/194; 623/1;
`623/12; 604/96
`[58] Field of Search .............................. .. 606/1, 108, 191,
`606/194 195 198 200. 604/96_104. 623/1
`’
`’
`’
`’
`’
`12’
`
`[56]
`
`References Cited
`
`Us PATENT DOCUMENTS
`4/1992 Ryan et aL _
`5’108’416
`571587548 10/1992 Lau et a1_ _
`5,242,399
`9/1993 Lau et 211..
`5,445,646
`8/1995 Euteneuer et al. .................... .. 606/198
`
`A encapsulated stent device for implantation Within the
`vascular system includes a balloon of a balloon catheter
`formed around and adhered to a Wire-like stent so that the
`outer surface of the device is more regular for delivery
`through the vascular system Without an exterior sheath. The
`encapsulation securely anchors the stent to the balloon and
`maintains a loW pro?le for negotiation of tortuous and
`narroWed vessels. Encapsulation requires placement of the
`stent Over the balloon, placement of a sheath over the stent
`on the baneem heating and Preferably pressurization of the
`balloon to cause it to expand around the stent Within the
`Sheath’ and Cooling While preferably maintaining pressure to
`cause the balloon to adhere to the stent and to set the shape
`of the expanded balloon. Retainers may be placed at the
`distal and/or proximal ends of the stent during the encap
`sulation process, or the balloon material may expand to form
`retainers. The balloon de?nes at least three folded Wings for
`symmetrical expansion of the stent, and one or more con
`nected or non-connected stents may be encapsulated
`depending upon the area to be treated.
`
`14 Claims, 5 Drawing Sheets
`
`50
`
`10
`
`5a 30—\
`
`32
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 1
`
`

`

`U.S. Patent
`
`Nov. 17,1998
`
`Sheet 1 of5
`
`5,836,965
`
`FIGURE 1
`
`FIGURE 2
`
`10
`
`4
`
`~34~
`
`32
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 2
`
`

`

`U.S. Patent
`
`Sheet 2 of 5
`
`Nov. 17, 1998
`
`5,836,965
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 3
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 3
`
`

`

`U.S. Patent
`
`Nov. 17, 1998
`
`Sheet 3 0f 5
`
`38
`
`7%
`
`u Q
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 4
`
`

`

`U.S. Patent
`
`Nov. 17,1998
`
`Sheet 4 of5
`
`5,836,965
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 5
`
`

`

`U.S. Patent
`
`Nov. 17,1998
`
`Sheet 5 of5
`
`5,836,965
`
`FIGURE 7
`
`54L
`
`X
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`54 36_\ \/
`
`I I I I I I I I I I I I I I I I I I I I I I I A
`
`I I I I I I I I I I I I I I I I I I I I I I I I I \
`
`i X
`
`r /\
`
`FIGURE 8
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`54;‘
`
`I I I I
`
`I I I I I I I I I I I I
`
`I
`
`54 361 /
`
`I I I
`
`I I I I I I I I I I I I’ I I I I\\
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 6
`
`

`

`1
`STENT DELIVERY AND DEPLOYMENT
`METHOD
`
`This application is a continuation-in-part of US. patent
`application Ser. No. 08/326,023, ?led on Oct. 19, 1994
`abandoned.
`
`FIELD OF THE INVENTION
`
`This invention relates to medical implant devices. More
`speci?cally, the invention relates to a stent encapsulated by
`an expandable balloon for delivery and deployment in
`narroWing coronary or peripheral vessels in humans.
`
`DESCRIPTION OF THE PRIOR ART
`Cardiovascular disease, including atherosclerosis, is the
`leading cause of death in the US. The medical community
`has developed a number of methods and devices for treating
`coronary heart disease, some of Which are speci?cally
`designed to treat the complications resulting from athero
`sclerosis and other forms of coronary arterial narroWing.
`An important development for treating atherosclerosis
`and other forms of coronary narroWing is percutaneous
`transluminal coronary angioplasty, hereinafter referred to as
`“angioplasty” or “PTCA”. The objective in angioplasty is to
`enlarge the lumen of the affected coronary artery by radial
`hydraulic expansion. The procedure is accomplished by
`in?ating a balloon Within the narroWed lumen of the coro
`nary artery. Radial expansion of the coronary artery occurs
`in several different dimensions, and is related to the nature
`of the plaque. Soft, fatty plaque deposits are ?attened by the
`balloon, While hardened deposits are cracked and split to
`enlarge the lumen. The Wall of the artery itself is also
`stretched When the balloon is in?ated.
`Angioplasty is typically performed as folloWs: A thin
`Walled holloW guiding catheter is introduced into the body
`via a relatively large vessel, such as the femoral artery in the
`groin area or the brachial artery in the arm. Once access to
`the femoral artery is achieved, a short holloW sheath, or
`guiding catheter, is inserted to maintain a passageWay during
`the procedure. The ?exible guiding catheter must negotiate
`an approximately 180 degree turn through the aortic arch to
`descend into the aortic cusp Where entry may be gained to
`either the left or the right coronary artery, as desired.
`After the guiding catheter is advanced to the area to be
`treated by angioplasty, a ?exible guideWire is inserted into
`the guiding catheter through an expandable balloon
`(described infra) and advanced to the area to be treated. The
`guideWire is advanced across the lesion, or “Wires” the
`lesion, in preparation for the advancement of a balloon
`catheter having an expandable balloon portion composed of
`polyethylene, polyvinyl chloride, polyole?n, or other suit
`able substance, across the guide Wire. Currently, most bal
`loons utiliZe tWo folded Wings Wrapped around the holloW
`catheter tube. The balloon catheter is placed into position by
`sliding it along the guide Wire. The use of the relatively rigid
`guide Wire is necessary for steerability to advance the
`catheter through the narroWed lumen of the artery and to
`direct the balloon, Which is typically quite ?exible, across
`the lesion. Radiopaque markers in the balloon segment of
`the catheter facilitate positioning across the lesion. The
`balloon catheter is then in?ated With contrast material to
`permit ?uoroscopic vieWing during treatment. The balloon
`is alternately in?ated and de?ated until the lumen of the
`artery is satisfactorily enlarged.
`Unfortunately, While the affected artery generally can be
`enlarged, in some instances the vessel restenoses
`
`15
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`5,836,965
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`2
`chronically, or closes doWn acutely, negating the positive
`effect of the angioplasty procedure. In the past, such rest
`enosis has frequently necessitated repeat PTCA or open
`heart surgery. While such restenosis does not occur in the
`majority of cases, it occurs frequently enough that such
`complications comprise a signi?cant percentage of the over
`all failures of the PTCAprocedure, for example, tWenty-?ve
`to thirty-?ve percent of such failures.
`To lessen the risk of restenosis, various devices have been
`proposed for mechanically keeping the affected vessel open
`after completion of the angioplasty procedure. Such
`mechanical endoprosthetic devices, Which are generally
`referred to as stents, are typically inserted into the vessel,
`positioned across the lesion, and then expanded to keep the
`passageWay clear. Effectively, the stent overcomes the natu
`ral tendency of the vessel Walls of some patients to close
`back doWn, thereby maintaining a more normal ?oW of
`blood through that vessel than Would be possible if the stent
`Were not in place.
`Various types of stents have been proposed, including
`self-expandable and expandable stents, although to date
`none has proven completely satisfactory. Expandable stents
`generally are conveyed to the area to be treated on balloon
`catheters or other expandable devices. For insertion, the
`stent is positioned in a compressed con?guration along the
`delivery device, such as a balloon catheter de?ning a balloon
`With tWo folded and Wrapped Wings, to make the stent
`diameter as small as possible. After the stent is positioned
`across the lesion, it is expanded by the delivery device,
`causing the length of the stent to contract and the diameter
`to expand. Depending on the materials used in construction
`of the stent, the stent maintains the neW shape either through
`mechanical force or otherWise.
`One such expandable stent for delivery on a balloon
`catheter is the PalmaZ stent (US. Pat. No. 4,733,665) Which
`may be thought of as a stainless steel cylinder having a
`number of slits in its circumference, resulting in a mesh
`When expanded. The stainless steel cylinder is compressed
`onto the outside of a non-expanded balloon catheter Which
`includes stent retainer rings at each end of the stent to help
`to maintain the stent on the balloon. Also, it is advisable to
`place a sheath over the compressed stent and balloon assem
`bly to retain the stent on the balloon and to create an even
`outer surface on the assembly for negotiation through the
`narroWed vessels. Boneau US. Pat. No. 5,292,331 provides
`a unitary Wire-like stent structure con?gured to form a
`plurality of upper and loWer axial peaks, and is delivered and
`expanded in a similar manner.
`Signi?cant dif?culties have been encountered With
`deployment of knoWn prior art stents, including dif?culty in
`maintaining the stent on the balloon and in achieving
`symmetrical expansion of the stent When deployed.
`Currently, some stent delivery systems retain the stent on the
`delivery catheter by means of either (a) plastically deform
`ing the stent so that it is crimped onto the balloon, or (b)
`having the stent exhibit a small enough internal diameter to
`act as an interference ?t With the outside diameter of the
`balloon catheter. The disadvantage With these methods is
`that the limited amount of securement betWeen the stent and
`the balloon is not alWays adequate to insure that the stent
`Will properly stay in place While advancing the stent to and
`through the target lesion. Additionally, the outer surface of
`the delivery device is uneven because the stent generally
`extends outWardly beyond the balloon and may contact a
`narroWed vessel Wall and be displaced While the catheter
`negotiates a narroWed vessel. Most knoWn expandable stent
`delivery systems utiliZe a removable sheath system on the
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 7
`
`

`

`5,836,965
`
`3
`outside of the stent, With or Without retainer rings, that is
`removed once the stent is at the delivery site. This method
`protects the stent and provides a smooth surface for easier
`passage through vessels, but the method increases the cross
`ing pro?le of the delivery device thereby decreasing the
`device’s ability to track through narroWed and tortuous
`vasculature. This and other complications have resulted in a
`loW level of acceptance for such stents Within the medical
`community, and to date stents have not been accepted as a
`practical method for treating chronic restenosis.
`A long felt need exists for a delivery and deployment
`method for stents Which ensures positional stability of the
`stent during delivery Without the need for an external sheath,
`thereby substantially decreasing the cross sectional pro?le of
`the balloon delivery device, and ensures symmetrical expan
`sion of the stent at deployment.
`
`SUMMARY OF THE INVENTION WITH
`OBJECTS
`
`The stent delivery and deployment method of this inven
`tion provides a froZen-in balloon in intimate contact With,
`and/or surrounding, a stent to assure stent attachment to the
`balloon, i.e. excapsulation. This method is especially valu
`able at the proximal and distal ends of the stent for delivery
`purposes because a smoother transition occurs betWeen the
`distal and proximal surfaces of the balloon catheter and the
`distal and proximal ends of the stent, and it also is effective
`along substantially the entire length of the stent. The froZen
`in balloon form is achieved by encapsulating the stent so that
`the balloon may expand part Way around the stent and
`adhere thereto. The preferred method of encapsulating the
`stent and balloon includes the steps of compressing the stent
`on the outside of the balloon, placing a sheath over the
`compressed stent to prevent expansion, and exposing the
`sheathed stent and balloon to an elevated temperature While
`pressuriZing the balloon. The elevated temperature and
`pressuriZation causes the balloon to expand from beloW the
`stent to ?ll at least some of the spaces betWeen the stent and
`the sheath. FolloWing expansion and exposure to an elevated
`temperature, the balloon and stent are cooled While main
`taining pressure in the balloon, so that the balloon pro?le
`Will be “froZen around” (formed and someWhat adhered to)
`the stent. Alternatively, heat Without pressuriZation of the
`balloon may be suf?cient for encapsulation When the com
`pressive forces of the sheath against the stent, Which is
`pressed against the heated balloon, enables encapsulation of
`the stent.
`If desired, the encapsulated stent may include conven
`tional retainers at the proximal and/or distal end of the
`balloon. Such retainers may be located on top of the balloon
`or Within the balloon. Additionally, the balloon itself may be
`used to form one or more stent retainers during encapsula
`tion. In this aspect of the invention, a space is de?ned
`betWeen the balloon and the sheath, proximal and/or distal
`to the stent, so that the balloon expands to occupy the space
`and form one or more retainers during the encapsulation
`process. Retainers assist in delivery by providing a smooth
`transition betWeen the encapsulated stent and the catheter
`surface.
`The preferred balloon for the method described above
`de?nes multiple (three or more) folded and Wrapped
`“Wings” or radial extensions on a balloon delivery device to
`assure radially symmetrical stent expansion during deploy
`ment. The preferred balloon utiliZes four Wings for a Boneau
`stent having four axial turns at each end, and the balloon
`length and number of Wings may be tailored to the particular
`
`4
`stent or stents to be deployed. By utiliZing more than tWo
`Wings, more symmetrical stent deployment and vessel cov
`erage can be achieved. Symmetrical stent deployment
`results in symmetrical expansion and support of the target
`lesion thereby suggesting use of multiple folds for standard
`PTCA balloon catheters With or Without stents.
`The method of this invention may be used With most
`self-expanding and expandable prior art stents, such as
`tubular slotted stents, and including connected stents, articu
`lated stents, and multiple connected or non-connected stents.
`It is preferred to use a stent apparatus such as the Boneau
`stent Which is formed preferably from a single piece of Wire
`de?ning axial bends or turns betWeen straight segments. The
`stent apparatus can then be encapsulated on a balloon
`catheter using the inventive method, delivered to the affected
`vessel and expanded in place, all as described herein. Some
`of the intended uses include PTCA type stenting, PTA type
`stenting, graft support, graft delivery, INR use, GI tract use,
`drug delivery, and biliary stenting.
`A general object of the present invention is to provide a
`stent delivery and deployment method that overcomes the
`draWbacks and limitations of the prior art.
`A speci?c object of the present invention is to provide a
`stent delivery and deployment method that eliminates the
`need for a deployment sheath and results in a loW pro?le
`device With a more regular outer surface that may be
`delivered through tortuous, narroWed vessel.
`Another speci?c object of the present invention is to
`provide a stent delivery and deployment method Which
`encapsulates the balloon and stent thereby securing the stent
`to the balloon and decreasing the pro?le of the stent and
`balloon.
`Yet another speci?c object of the present invention is to
`provide a stent delivery and deployment method Which
`includes a balloon With three or more Wrapped and folded
`Wings to ensure symmetrical deployment of the stent and
`expansion of the lesion to be treated.
`One more speci?c object of the present invention is to
`provide an encapsulated stent and balloon have a retainer at
`the distal and/or proximal ends of the stent for maintaining
`the stent on the balloon and for forming a smooth outer
`surface on the encapsulated stent device.
`Still another speci?c object of the invention is to provide
`a method for encapsulating the majority of expandable and
`self-expanding stents for treating vessels in humans.
`These and other objects, advantages and features of the
`present invention Will become more apparent upon consid
`ering the folloWing detailed description of preferred
`embodiments, presented in conjunction With the accompa
`nying draWings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a longitudinal cross sectional vieW of tWo
`encapsulated stents and a balloon embodying the principles
`of the present invention and shoWn on a balloon catheter
`device.
`FIG. 2 is a longitudinal cross sectional vieW of the stents
`of FIG. 1 compressed upon a balloon of a balloon catheter
`and shoWn prior to the encapsulation process.
`FIG. 3 is a longitudinal cross sectional vieW of the stents
`and balloon during the encapsulation process and shoWn
`positioned Within interior and exterior sheaths.
`FIG. 4 is a cross sectional vieW taken along lines 4—4 of
`FIG. 2 and shoWing four folded and Wrapped Wings of the
`balloon beneath one of the stents.
`
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`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 8
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`

`

`5,836,965
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`5
`FIG. 5 is a cross sectional vieW showing the partially
`in?ated form of the balloon around the stent.
`FIG. 6 is a cross sectional vieW taken along lines 6—6 of
`FIG. 1 and shoWing the froZen-in form of the balloon around
`the stent.
`FIG. 7 is a longitudinal cross sectional vieW of tWo
`encapsulated stents and a balloon shoWing retainers on the
`outside of the balloon.
`FIG. 8 is a longitudinal cross sectional vieW of encapsu
`lated stents and a balloon shoWing retainers on the inside of
`the balloon and attached to the balloon catheter.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`FIG. 1 shoWs an encapsulated stent assembly 20 embody
`ing the principles of the present invention. TWo stent seg
`ments 10 are shoWn, and it Will be recogniZed by those
`skilled in the art that one or more stent segments 10 may be
`used depending upon the siZe and con?guration of the
`narroWed vessel to be treated. Additionally, When more than
`one stent segment 10 is used, the segments may be con
`nected together by articulated or rigid joints, or multiple
`single stent segments may be deployed on the balloon
`catheter 30.
`The balloon catheter 30 preferably is of a loW pro?le
`design de?ning a tapered distal tip 32, and an inner lumen
`34 for insertion of a conventional guide Wire (not shoWn).
`Any conventional or modi?ed balloon catheter device may
`be used, such as a PTCA balloon catheter, and it is preferred
`that the expandable balloon portion 36 be con?gured on the
`catheter 30 so that the collapsed balloon de?nes three or
`more folded Wings 38 Which are Wrapped around the outside
`of the catheter tube 40 as best shoWn in FIG. 4. In the
`embodiment in FIG. 4, the balloon 36 de?nes four folds 38
`Wrapped around the catheter tube 40 in a clockWise direc
`tion.
`The preferred balloon 36 is formed from a material such
`as polyethylene, polyethylene terephthalate (PET), or from
`nylon or the like. The length and diameter of the balloon
`may be selected to accommodate the particular con?guration
`of the stent to be encapsulated. The balloon may be carried
`on any catheter, although PTCA loW pro?le catheters and
`over the Wire catheters are preferred. The Wings of the
`balloon are formed by pulling the balloon catheter through
`a forming tool having a generally cylindrical cross section
`and de?ning a terminal opening con?gured to produce the
`desired number of Wings in the balloon. For instance,
`con?guration of the terminal opening may include three or
`four slits radiating outWardly from the end of the forming
`tool, depending upon the number of folds to be produced. As
`the balloon catheter is pulled through the forming tool, the
`balloon is pushed through the con?gured terminal opening
`and exits having, for instance, three separate ?utes. The
`balloon catheter bearing the ?uted balloon portion then is
`pulled into a sheath, preferably a tWo part sheath made of
`Te?on or other suitable materials, so that the ?utes fold and
`Wrap around the catheter in a clockWise direction to form a
`generally spiral con?guration around the catheter. The
`sheath-balloon catheter assembly is subjected to heat, pref
`erably by placing the assembly in a heat set oven, to form a
`crease in substantially the length of each of the folded ?utes.
`The sheath also may be of unitary construction. FolloWing
`heat setting, the balloon 36 retains the creases formed in the
`Wings and de?nes a generally symmetrical, cylindrical cross
`section, as best seen in FIG. 4.
`Referring noW to FIGS. 1—5, the Boneau stent is shoWn
`for illustration purposes only, and Boneau US. Pat. No.
`
`10
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`
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`5,292,331 is hereby incorporated by reference. Each of the
`stent segments 10 is preferably a short, single Wire stent 10
`having an expandable, generally cylindrical body portion
`de?ning an inside surface and an outside surface. In the stent
`segments 10 shoWn, the single piece of Wire is bent to form
`a plurality of upper and loWer axial turns 2. The plurality of
`upper turns 2 are connected to the plurality of loWer turns 2
`by substantially straight sections 4. The axial turns 2 can be
`seen to permit the stent segment 10 to be compressed or
`expanded over a Wide range While still maintaining a sig
`ni?cant mechanical force, such as required to prevent a
`vessel from restenosis or recoiling.
`The stent segments 10 are preferably constructed of
`implantable materials having good mechanical strength,
`such as implantable quality stainless steel Wire. The outside
`of the stent segments may be selectively plated With
`platinum, or other implantable radiopaque substances, to
`provide improved visibility during ?uoroscopy. The cross
`sectional shape of the ?nished stent segment 10 may be
`circular, ellipsoidal, rectangular, hexagonal, square, or other
`polygon, although at present it is believed that circular or
`ellipsoidal may be preferable.
`The minimum length of each stent segment 10, or the
`distance betWeen the upper turns and loWer turns 2, is
`determined in large measure by the siZe of the vessel into
`Which the stent 20 Will be implanted. Additionally, each
`stent segment 10 may de?ne N number of turns, N being
`preferable betWeen 2 and 10. In the stent segments 10 shoWn
`in the draWings, the segments de?ne four upper and four
`loWer axial turns 2. The stent segments 10 may be connected
`together by articulated or rigid joints, or they may be
`deployed in a multiple spaced apart, non-connected con?gu
`ration. The implanted encapsulated stent assembly 20 Will
`preferably be of suf?cient length as to maintain its axial
`orientation With the vessel Without shifting under the
`hydraulics of blood ?oW (or other ?uid ?oW in different
`types of vessels), While also being long enough to extend
`across at least a signi?cant portion of the affected area. At
`the same time, the encapsulated stent 20 should be short
`enough as to not introduce unnecessarily large amounts of
`material as might cause undue thrombosis.
`FolloWing selection of the con?guration and siZe of a
`stent segment 10, or multiple connected or non-connected
`stent segments, the segment or segments 10 are compressed
`upon the outside of the balloon 36 of the balloon catheter 30
`as best shoWn in FIGS. 2 and 4. An interior sheath 42 is
`placed over each end of the balloon catheter 30, and an
`exterior sheath 44 is placed over the interior sheath 42 to
`cover the stent segments 10 and overlap With the interior
`sheath 42. The sheaths 42, 44 are preferably non
`expandable, and of a siZe to accept insertion of the stent
`segments 10 mounted on the balloon. Sheaths 42, 44 are
`shoWn for example only, and it Will be recogniZed by those
`skilled in the art that the balloon catheter and stents com
`pressed thereon also may be placed Within a mold to prevent
`expansion of the stent and con?gured to alloW expansion of
`the balloon as desired.
`Next, the balloon catheter 30 preferably is pressuriZed by
`introducing air, or an inert gas such as nitrogen, through the
`lumen 34 into the interior of the balloon to partially expand
`the balloon 36 Within the sheaths 42, 44. The assembly then
`is exposed to an elevated temperature While maintaining
`pressuriZation of the balloon. The pressure may be, for
`example, approximately 70 psi, and the elevated temperature
`may be achieved by placing the sheathed assembly into an
`oven at approximately 150 degrees Fahrenheit to accomplish
`the heating step.
`
`Petitioner Edwards Lifesciences Corporation - Exhibit 1016 - Page 9
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`5,836,965
`
`7
`FIGS. 4—6 demonstrate, respectively, the con?guration of
`the balloon 36 prior to pressurization, the con?guration
`during in?ation, and the froZen-in form con?guration around
`and adhering to a stent segment 10. The balloon 36, and the
`Wings 38, expand partially outWardly to occupy spaces
`around the axial turns 2 and betWeen the straight sections 4
`so that the balloon 36 and the stent segments 10 are in
`intimate contact. Those skilled in the art Will recogniZe that
`expansion of the balloon also depends upon the form of the
`particular stent selected for encapsulation. Pressure betWeen
`the stent and the balloon during heating and balloon pres
`suriZation causes an adherence upon cooling. Adherence is
`required for encapsulation Which includes both intimate
`contact betWeen the stent and the balloon as Well as contact
`Where the balloon surrounds at least a portion of the stent.
`Alternatively, pressuriZation of the balloon during the
`heating step is not required Where the sheaths 42, 44 ?t
`tightly around the stent-balloon assembly. Pressure radiating
`inWardly from the sheaths 42, 44 to press against the stents
`10 causes the stents 10 to press against the heated balloon to
`achieve encapsulation.
`FolloWing heating, the balloon-stent assembly is removed
`from the heat and alloWed to cool Within the sheath. In those
`cases Where the balloon has been pressuriZed during heating,
`the internal pressure is maintained. Cooling sets the shape of
`the balloon 36 Which adheres to the stent 10 folloWing
`cooling, thereby alloWing removal of the sheaths 42, 44 for
`delivery of the assembly 20 Within a vessel. Because of the
`adherence betWeen the stent segment 10 and the balloon 36
`of the encapsulated stent assembly 20 and the more regular
`surface area created by encapsulating stent assembly
`segments, the encapsulated stent assembly 20 may be deliv
`ered Without an external sheath.
`As best shoWn in FIG. 3, and in FIG. 1, the encapsulated
`stent assembly 20 may include a distal retainer 50 and/or a
`proximal retainer 52. The retainers 50, 52 further secure the
`stent segment 10 to the balloon 36 and create a smooth
`transition betWeen the balloon/stent area of the delivery
`device and the distal and proximal surfaces of the delivery
`device of the encapsulated stent assembly 20. The retainers
`50, 52 may be formed by the balloon itself during the
`encapsulation process, With the con?guration of the formed
`retainers 50, 52 determined by the dimensions of the spaces
`betWeen the inner sheath 42 and the stent segments 10.
`Formed retainers 50, 52 may be tapered or non-tapered.
`Alternatively, conventional retainers 54 may be attached
`over the balloon 36 prior to encapsulation, as shoWn in FIG.
`7, or the retainers 54 may be placed Within the balloon 36,
`as shoWn in FIG. 8. One or tWo retainers 54 may be used,
`and conventional retainers may be made from any implant
`able material, such as implantable stainless steel or poly
`mers. Depending upon the con?guration of the encapsulated
`stent assembly 20, retainers generally range in length from
`0—20 mm.
`The encapsulated stent assembly 20 is delivered to the
`desired site With or Without a guiding catheter and using a
`conventional guideWire for steerability to negotiate the area
`to be treated. Conventional radiopaque markers and ?uo
`roscopy may be used With the device for positioning the
`encapsulated stent assembly and for vieWing the expansion
`procedure. Once the encapsulated stent assembly is in place
`across the lesion, the balloon may be in?ated in a conven
`tional manner. In the embodiment shoWn in FIGS. 4—6, the
`four Wings 38 expand evenly to form four, symmetrical
`expanded ?utes Which symmetrically expand the inner
`diameter of the encapsulated stent outWardly by increasing
`the angle at the axial bends. During typical balloon expan
`
`15
`
`25
`
`35
`
`45
`
`55
`
`65
`
`8
`sion pressures of approximately 6 atmospheres or 90 psi,
`occurring Within the human body and at body temperature,
`the heat set creases dissipate. The folded and Wrapped Wing
`con?guration of the balloon ensures that the balloon Will
`provide radially uniform in?ation so that the stent Will
`expand substantially equally along each of the peaks. Uni
`form expansion of the lumen of the vessel occurs With
`uniform, symmetrical expansion of the encapsulated stent
`and balloon. The amount of in?ation, and commensurate
`amount of expansion of the stent, may be varied as dictated
`by the lesion itself, making the stent assembly of the present
`invention particularly ?exible in the treatment of chronic
`restenosis and abrupt reclosure.
`Because of the in?ation of the balloon and expansion of
`the arterial Wall of the vessel, the arterial Wall bulges
`radially. At the same time, the plaque deposited Within the
`intima of the vessel is displaced and thinned, and the stent
`is embedded in the plaque or other ?brotic material adhering
`to the intima of the vessel.
`FolloWing in?ation of the balloon and expansion of the
`encapsulated stent Within the vessel, the balloon is de?ated
`so that it pulls aWay from the stent for removal. The de?ated
`balloon generally forms from 11/2 to 2% Wings, including a
`generally U-shaped de?ated form, and the de?ated Wings do
`not retain the creases created by the heat setting balloon
`formation process discussed above. The de?ated balloon
`easily folds around the balloon catheter for removal.
`The exterior Wall of the vessel attempts to return to its
`original shape through elastic recoil. The stent, hoWever,
`remains in its expanded form Within the vessel, and prevents
`further recoil and restenosis of the vessel. The stent main
`tains an open passageWay through the vessel. Because of the
`loW mass of the preferred support device of the present
`invention, thrombosis is less likely to occur. Ideally, the
`displacement of the plaque deposits and the implantation of
`the stent Will result in a relatively smooth inside diameter of
`the vessel.
`While the primary application for the stent is presently
`believed to be treatment of cardiovascular disease such as
`atherosclerosis or other forms of coronary narroWing, the
`stent of the present invention may also be used for treatment
`of vessels in the kidney, leg, carotid, or elseWhere in the
`body. In such other vessels, the siZe of the stent may need to
`be adjusted to compensate for the differing siZes of the
`vessel to be treated.
`While this invention has been described in connection
`With preferred embodiments thereof, it is obvious that modi
`?cations and changes therein may be made by those skilled
`in the art to Which it pertains Without departing from the
`spirit and scope of the invention. For instance, the encap
`sulation method and deployment is not limited to any
`particular expandable stent device. Accordingly, the aspects
`discussed herein are for illustration only and should not limit
`the scope of the invention herein Which is de?ned by the
`claims.
`W