United States Patent 1191
`Andersen
`
`US005234457A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,234,457
`Aug. 10, 1993
`
`
`
`
`
`4,922,905 5/1990 Strecker 4,950,227 8/1990 Savin ‘ 5,026,377 6/1991 Burton :1 a1.
`
`606/195
`
`5 061,275 10/1991 Wallsten et a1. .
`
`
`
`
`
`5 078,720 l/ 1992 Burton et a1. $089,005 2/1992 Hnrada $092,877 3/1992 Pinchuk
`
`. 606/108
`623/1
`. 606/108
`.
`. 606/192
`623/1
`606/195
`5 133,732 7/1992 Wiktor FOREIGN PATENT DOCUMENTS
`
`[54] IMPREGNATED STENT
`[75] Inventor:
`Erik Andersen, Roskilde, Denmark
`[73] Assignee:
`Boston Scienti?c Corporation,
`Watertown, Mass.
`[21] Appl. N0.: 773,847
`[22] Filed:
`Oct. 9, 1991
`[51]
`Int. Cl! ..
`[521
`11.8. C1.
`[58]
`
`A61M 29/00
`606/198; 606/108;
`606/154; 606/195
`v606/108, 192, 194, 195,
`Field of Search
`606/198, 230, 77, 154, 191, 200; 623/1
`References Cited
`U.S. PATENT DOCUMENTS
`
`[561
`
`
`
`892980 4/1962 United Kingdom
`Primary Examiner-Edgar S. Burr
`Assistant Examiner-Ken Yan
`Attomey, Agent, or Firm-Pearson 8: Pearson
`[57]
`ABSTRACT
`A stent assembly, delivery system and method of manu
`
`623/1
`
`3,868,956 3/1975 Al?di et a1. . ..
`
`
`
`4,512,338 4/1985 Balko et a1. 4,580,568 4/ 1986 Gianturco
`
`..
`
`4,629,459 12/1986 Ionescu et a1 .
`4,655
`771 4/1987 Wallsten
`..
`4,665
`.
`918 5/1987 Garza et a1.
`4,690
`684 9/ 1987 McGreevy et a].
`665 3/1988 Palmaz
`4,733
`479 1/1989 Spears
`4,799
`4,878
`906 11/1989 Lindemann et a1.
`4/1990 Hillstead
`4,913
`
`1024
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`U.S. Patent
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`Aug. 10, 1993
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`Sheet 1 of 5
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`US. Patent
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`Aug. 10, 1993
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`Sheet 2 of 5
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`US. Patent
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`Aug. 10, 1993
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`Sheet 3 of 5
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`MANUFACTURE OF
`EXPANDABLE STENT
`DELIVERY SYSTEM
`
`MANUFACTURE OF SELF
`EXPANDING STENT
`DELIVERY SYSTEM
`
`MANUFACTURE A STENT
`FROM AN EXPANDABLE / 4|
`MATERIAL
`
`42
`
`MANUFACTURE A STENT
`FROM A SELF-EXPANDING
`MATERIAL
`
`SELECT A MANDREL
`
`{43
`
`SELECT AN APPROPRIATE
`44v LENGTH OF INSERT TUBE
`FOR A SUPPORT MANDREL
`1%
`§-_____l
`I MOUNT A MARKER AT THE I
`LOCATION OF THE
`PROXIMAL AND/OH DISTAL _/45
`ENDS OF THE STENT ON
`THE SUPPORT MANDREL
`
`COMPACT THE sTENT mm 46
`:L THE SELECTED MANDREL /
`
`CONTAIN THE STENT IN
`COMPACT FORM
`
`47
`./
`
`IMPREGNATE THE STEM
`WITH GELATIN
`
`50
`/
`
`WIPE THE sTENT AND CURE 5|
`THE GELATIN
`/
`
`FREE THE COMPACT
`IMPREGNATED sTENT FROM /52
`CONTAINMENT
`
`i
`
`REMOVE THE MANDREL
`
`I
`
`POSITION THE
`IMPREGNATED STENT ON
`AN EXPANDER DEVICE
`
`INSTALL END AND TIP
`BUSHINGS ON THE
`MANDREL
`I
`AFFIX THE END BUSHING TO
`A POSITIONING DEVICE AND
`LOCATE THE STENT
`ASSEMBLY IN A SHEATH
`
`004
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`US. Patent
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`Aug. 10, 1993
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`US. Patent
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`Aug. 10, 1993
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`1
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`DMPREGNATED STENT
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`10
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`30
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`35
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`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention generally relates to a class of endo
`prostheses known as “stents” and more speci?cally to
`the structure and manufacture of such stents and the
`assembly of such stents into delivery systems.
`2. Description of Related Art
`' Certain medical devices, called “stents”, are well
`known and have a variety of forms. For example, U.S.
`Pat. No. 4,690,684 of Sep. 1, 1987 to McGreevy et al for
`a “Meltable Stent for Anastomosis” discloses a solid
`stent formed of a biologically compatible material, such
`a frozen blood plasma or the like. According to the
`disclosure, a solid stent of this type may be inserted into
`opposed ends of a ruptured vessel to support the sepa
`rated vessel walls while the ends are bonded together.
`20
`The heat from the bonding operation and the body
`eventually melt the stent and clear the vessel.
`A stent that constitutes an endoprosthesis usually
`comprises a tubular structure that expands radially to be
`implanted into the tissue surrounding a “vessel” thereby
`25
`to maintain its patency. It is well known that stents may
`be utilized in body canals, blood vessels, ducts and other
`body passageways, and the term “vessel” is meant to
`include all such passageways. Generally speaking, a
`stent delivery system includes the stent and some means
`for positioning and ?xing the stent in place. Typically,
`the stent delivery system includes a catheter that sup
`ports the stent in a compacted form for transport to a
`site of implantation. Means integral with or ancillary to
`the catheter then expand the stent radially into the ves
`sel walls to be implanted at the selected site. After the
`catheter is removed, the stent retains an expanded shape
`to keep the vessel walls from closing.
`Stent delivery systems must conform to several im
`portant criteria. First, it is important to keep the trans
`verse dimension of the delivery system to a minimum,
`so the stent must be capable of compaction against a
`delivery device, such as a catheter. Second, the delivery
`system must facilitate the deployment of the stent into
`contact with the vessel walls once it is located in a
`body. Third, the stent delivery system must easily disen
`gage from the stent after the stent is deployed. Fourth,
`the procedure for removing the delivery system from
`the body must be straightforward. Fifth, the delivery
`system must operate reliably.
`‘U.S. Pat. No. 4,922,905 of Ernst P. Strecker for a
`“Dilatation Catheter” describes the manufacture, con
`struction and use of such stents and is incorporated
`herein by reference. In the speci?c disclosure of the
`Strecker patent, the stent comprises a tubular structure
`that is knitted from metal or plastic ?lament in loosely
`interlocked loops. A stent delivery system from metal
`or includes a balloon catheter and a coaxial sheath. The
`balloon catheter supports the compacted stent during its
`transport to a site within the body. The sheath covers
`the stent‘to prevent premature stent expansion and to
`facilitate the transfer of the stent through various pas
`sages in the body. A physician properly locates the
`stent, and then moves the sheath axially with respect to
`the catheter thereby to expose the stent. Then the physi
`cian operates a balloon pumping system to expand the
`balloon catheter and move the stent into a ?nal con?gu
`ration in contact with tissue surrounding the stent.
`When the stent expands radially, the ?lament material
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`5,234,457
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`undergoes a plastic deformation. Consequently, the
`stent retains its new expanded shape. When the balloon
`subsequently de?ates, it is free of the expanded stent, so
`the catheter, sheath and remainder of the delivery sys
`tem can be withdrawn from the patient.
`Commercial embodiments of the structures shown in
`the Strecker patent include rings for overlapping the
`end portions of the compacted stent thereby to elimi
`nate the sheath. In such embodiments, however, the
`entire assembly of the catheter and compacted stent
`slides into position after passing through a previously
`positioned introducer sheath.
`U.S. Pat. No. 4,733,665 of Mar. 29, 1988 to Palmaz
`for an "Expandable Intraluminal Graft, and Method
`and Apparatus for Implanting an Expandable Interlumi
`nal Graft” discloses a catheter with rings for positioning
`a compacted stent on a balloon portion of the catheter.
`A sleeve encases the compact stent. When the stent is
`properly positioned, a physician retracts the sleeve and
`pumps the catheter to expand the stent into position.
`During its expansion the stent detaches from the mount
`ing rings. Then the physician de?ates the balloon and
`removes the catheter, leaving the stent in place.
`Other patents disclose other devices and operators
`for releasing stents. For example, in some stents the
`compaction process introduces stresses into the stent
`materials that act to expand the stent after its release
`from a sleeve or similar restraint. The following patents
`disclose examples of such structures:
`U.S. Pat. No. 4,580,568 (1986) Gianturco
`U.S. Pat. No. 4,665,918 (1987) Garza et al
`U.S. Pat. No. 4,913,141 (1990) Hillstead
`Other patents disclose various structures in which
`heat expands the stent and include:
`U.S. Pat. No. 3,868,956 (1975) Al?di et al
`U.S. Pat. No. 4,512,338 (1985) Balko et al
`U.S. Pat. No. 4,799,479 (1989) Spears
`U.S. Pat. No. 5,026,377 of Jun. 25, 1991 to Burton et
`al for a “Stent Placement Instrument and Method”
`discloses a delivery system for a self-expanding stent.
`The stent is a braided structure formed of a shape mem
`ory material. An outer sleeve retains the stent radially
`during transport to a ?nal site within the body. A grip
`member enables both deployment and retraction of the
`stent. There-are several examples of grip members in
`this patent. One, for example, comprises a releasable
`adhesive on a support for the stent. The adhesive grips
`the stent without slipping while the stent is in the instru
`ment, but allows the stent to expand when a outer sleeve
`is retracted.
`As known the overall diameter and ?exibility of a
`stent and its delivery system determine the range of
`vessels that can receive a stent. It is important that any
`stent structure have as small an overall diameter as
`possible. The smaller the diameter, the greater the range
`of vessels for which the endoprosthesis becomes viable.
`That range of vessels is limited with prior art structures
`particularly by a protective sheath or the like that sur
`rounds a stent and has two functions. First, the protec
`tive sheath provides a smooth surface over the stent to
`facilitate its transport through the body with minimal
`trauma. Second, the protective sheath prevents the stent
`from expanding prematurely. The second function de
`termines the wall thickness of a sheath or like structure
`and with it the overall diameter of the stent delivery
`' system. The wall must be suf?ciently thick to provide
`the strength necessary to restrain the stent. This thick
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`ness is greater than the wall thickness required by the
`?rst function. For a given diameter stent, the overall
`diameter of the stent and the sheath or the like can
`exceed a minimal diameter. It is this characteristic that
`prevents the introduction of prior art stents into smaller
`vessels.
`
`4
`BRIEF DESCRIPTION OF THE DRAWINGS
`The appended claims particularly point out and dis
`tinctly claim the subject matter of this invention. The
`various objects, advantages and novel features of this
`invention will be more fully apparent from a reading of
`the following detailed description in conjunction with
`the accompanying drawings in which like reference
`numerals refer to like parts, and in which:
`FIG. 1 depicts a stent that is adapted for use in con
`nection with this invention;
`FIG. 2 depicts a stent assembly embodying this in
`vention;
`FIG. 3 including FIGS. 3A through 3F and FIG. 4,
`taken together, depict manufacturing steps that convert
`the stent of FIG. 1 to a stent assembly as shown in FIG.
`2;
`FIG. 5 is a cross-sectional view of one embodiment of
`a stent delivery system constructed in accordance with
`this invention;
`FIG. 6 is a view of a vessel with a stent and a stent
`delivery system of FIG. 5 positioned therein; and
`FIG. 7 is another embodiment of a stent delivery
`system constructed in accordance with this invention.
`
`DESCRIPTION OF ILLUSTRATIVE
`EMBODIMENTS
`FIG. 1 discloses one embodiment of a tubular endo
`prothesis stent 10, in expanded form and constructed in
`accordance with the disclosure of the previously identi
`?ed US. Pat. No. 4,922,905. In this particular embodi
`ment the stent 10 comprises a single ?lament 11 that is
`knitted into a mesh cylinder 12 extending coaxially with
`an axis 13 and comprising a fabric of loosely interlocked
`?lament loops that form the wall of the cylinder 12. The
`?lament can be selected from two groups of materials
`depending upon the ultimate characteristics of the stent
`10
`Generally, the ?lament 11 should be formed of a
`biocompatible material. When expanded to a ?nal form
`as shown in FIG. 1, the structure should be resistant to
`subsequent deformation. Thus these materials normally
`are taken from a group of shape memory metals that
`maintain the stent in an expanded form. The material
`preferably is radiopaque.
`When a stent 10 is to be self-expanding, a self-expand
`ing material such as a super elastic material is selected so
`compaction produces internal restoring forces within
`the material. Nitinol is an example of such a super elas
`tic material that is particularly adapted for self-expand
`ing stents. Obviously if the stent 10 is self-expanding, it
`will be necessary to contain such self-expanding stents
`in compact form. The stent 10 will return to the shape
`shown in FIG. 1 when it is freed from any containment.
`If some external apparatus, such as a balloon catheter,
`is to expand the stent 10, the stent 10 may be comprised
`of a material from a group of plastic deformable materi
`als that include stainless steel and tantalum.
`In accordance with another aspect of this invention,
`the stent 10 in FIG. 1 is compacted into a stent assembly
`20 as shown in FIG. 2. As described in more detail later,
`compaction can produce a reduction in the overall ra
`dius of the stent 10 by a 10:1 with about a 30% increase
`in the overall length of the stent 10. The stent assembly
`20 also ' includes a cured, dissolvable material that
`readily shifts between liquid and solid phases at a melt
`ing temperature in the range of 30° C. to 40° C. This
`material impregnates the interstices of the mesh stent l0
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`SUMMARY
`Therefore it is an object of this invention to provide
`an improved stent system.
`Another object of this invention is to provide an
`improved stent structure that
`the overall
`diameter of the stent and the apparatus for delivering
`the stent to a vessel.
`Still another object of this invention is to provide an
`improved stent structure that is formed of a self’expend
`ing ?lament material in loosely interlocked loops.
`Yet another object of this invention is to provide an
`improved stent structure that enables the placement of
`20
`the stent in vessels that are smaller than those that could
`receive prior art stents.
`Still another object of this invention is to provide a
`stent delivery system with an improved stent structure.
`Still yet another object of this invention is to provide
`a stent delivery system with an improved stent structure
`that minimizes the overall diameter of the delivery sys
`tem at the stent.
`Yet still another object of this invention is to provide
`an improved stent delivery system with a stent that
`enables the placement of a stent in vessels that are
`smaller than those that could receive prior art stents. g
`Yet another object of this invention is to provide an
`improved method for the manufacture of stents.
`Yet still another object of this invention is to provide
`an improved method for manufacture of stents that
`allows the incorporation of the stents in apparatus that
`is adapted for implanting the stent in smaller vessels
`than previously possible.
`.
`In accordance with this invention, the above objects
`are attained by a stent assembly that comprises a com
`pact mesh in a cylindrical form. The mesh can expand
`into a cylindrical mesh stent that engages the tissue
`walls surrounding a vessel. A cured dissolvable material
`impregnates the mesh and contains the mesh in its com
`pact form during placement. The cured material dis
`solves when the stent is in position in the body thereby
`to free the mesh and enable its expansion into a ?nal
`form contacting the tissue surrounding the vessel.
`In accordance with another aspect of this invention, a
`stent delivery system comprises an elongated stent as
`sembly, a delivery structure for positioning the stent
`assembly at a predetermined position in the body and a
`stent support. The stent support is coaxial and coexten
`sive with the stent assembly and affixes it to the delivery
`structure. The stent assembly includes a compact mesh
`and a cured soluble dissolvable material that impreg
`nates and contains the mesh. After the stent assembly is
`properly positioned, the cured material, that is soluble
`in the vessel, dissolves and frees the mesh for expansion.
`In still another aspect of this invention the manufac
`ture of a stent assembly includes the step of producing a
`cylindrical stent in compact form. Then the stent is
`impregnated with dissolvable material in liquid form.
`The material cures and forms a solid structure for con
`taining the stent in its compact form.
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`and has suf?cient strength to contain the stent 10 in its
`compact form.
`There are several materials that have these character
`istics, including polymers, such as resorbable polyesters
`or polyvinyl alcohol based materials and gelatin. Gela
`tin is particularly adapted for use in accordance with
`this invention as it transforms from a liquid form'on
`cooling into a cured, solid mass. The mass has sufficient
`strength to contain the stent 10 in its compact form,
`even when the stent 10 is formed of a self expanding
`material. Gelatin also has the property of liquefying
`when heated above some predetermined temperature
`that is normally less than 37‘ C. In addition certain
`enzymes, such as those found in the body, will attack
`the gelatin and cause it to lose its strength and viscosity.
`Thus, when a stent assembly 20 having a compact
`stent 10 and gelatin 21 as shown in FIG. 2 is introduced
`into the body, the body temperature and liquids that the
`stent assembly 20 contacts coact to liquify the gelatin.
`The body ?uids transport the gelatin out of the system
`and this liquefaction releases the stent for expansion.
`The rate of thermal decomposition of gelatin depends
`upon the type and quality of the gelatin, the tempera
`ture of the gelatin and the nature of any enzymes that
`may attack the solution. All these parameters can be
`controlled by the selection of gelatins with particular
`properties. Particularly, it has been found that Vee Gee
`Extra Fine 100 Bloom Type A gelatin or Vee Gee 100
`Bloom Type B gelatin from the Vyse Gelatin Company
`produce satisfactory gelatins for impregnating a mesh
`30
`stent.
`Although the stent assembly 20 may be constructed
`with pure gelatin or like dissolvable materials that only
`contain the stent, other disparate constituents can be
`added for producing other functions. For example, it is
`_ possible to mix barium or other marker materials into
`gelatin for assisting during ?uoroscopy or other imag
`ing techniques. Alternatively the gelatin or other mate
`rial could entrain any of a number of encapsulated medi
`cines for a timed release into the body as the material
`dissolves, particularly if a gelatin is designed to dissolve
`over a longer time period. It is also possible to combine
`the markers or medicines in a stent assembly comprising
`an axial distribution of gelatins or other materials with
`different rates of thermal decomposition. In such an
`application, the materials would release at differing
`times and rates. Moreover, the axial distribution could
`be used to control the physical profile of a the stent as
`it expands.
`When a stent is impregnated with a cured gelatin or
`other material, it becomes rigid. This rigidity impacts
`the ability of the stent assembly 20 to pass through a
`tortious path to a vessel. In accordance with another
`aspect of this invention, a helical groove 22 in the outer
`cylindrical surface 23 of the stent assembly 20 facilitates
`bending of the stent assembly 20. As another altema
`tive, the gelatin 21 could be located at discrete, sepa
`rated axial positions along the length of the compact
`stent and achieve the same general results while also
`improving ?exibility. As still another alternative a
`groove could be formed on an inner cylindrical surface
`24 of the stent assembly 20.
`The exact method of manufacture of a given stent
`assembly in accordance with this invention depends
`upon several factors. Two major factors are the ?nal
`application for the stent and whether the stent 10 is
`formed of a self-expanding material or an expansible
`material that requires some external force to expand it.
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`The manufacturing process begins with a selection of a
`stent 10 shown in FIG. 3A and represented by steps 41
`and 42 in FIG. 4. That is, in accordance with step 41 the
`stent 10 in FIG. 3A would be formed of an expansible
`plastic deformable material, such as stainless steel or
`tantalum. In step 42 the stent would be selected from
`any of the self-expanding super elastic alloys for stent
`material such as Nitinol.
`A next step is optional and dependent upon the end
`application. As shown by step 43, it is possible to select
`a mandrel 30 in FIG. 3B. If the stent 10 is already in a
`compact form, it may be possible that no mandrel is
`required at all. In other applications, the mandrel 30
`might become an integral part of the ?nal stent assem
`bly 20. In such an application the mandrel might consti
`tute a balloon portion of a balloon catheter. In still other
`applications, the mandrel 30 might be used only for
`manufacture and then removed from the ?nal stent
`assembly 20. If the stent is to be manufactured as a
`self-expanding stent, the mandrel 30 might be selected
`as a tube insert formed of an extruded polymer material
`as shown in step 44.
`Step 45 in FIG. 4, is also an optional step in which
`radiopaque markers 31 and 32 are attached to the man
`drel 30, as shown in FIG. 3C. The spacing between the
`markers 31 and 32 corresponds to the axial length of the
`stent 10 of FIG. 3A in its compact form.
`In step 46 the stent 10, if in an expanded form, is
`compacted onto the mandrel 30 by applying tension in
`an axial direction simultaneously with radial compres
`sion so the stent will have a low pro?le that facilitates
`its introduction into a body passageway. During this
`process, as shown in FIG. 3D, a supplementary mandrel
`33 can be positioned in the mandrel 30 for added sup
`port. During the compaction process, a ?lament 34 may
`be wrapped around the compacted stent l0 and tied to
`the mandrel 30 in step 47. This ?lament 34 contains the
`stent 10 in its compact form for subsequent processing.
`The ?lament 34 can comprise any number of materials
`that contain the stent in its compact form during the
`processing and do not adhere to the gelatin or other
`material that impregnates the stent. Elastic ?laments
`containing polymeric silicons are preferred because of
`advantages in subsequent processing steps; Silastic®
`?laments are examples.
`In step 50, liquid gelatin 35, or a similar liquid, is
`poured from a container 36 onto the stent 10 while the
`entire assembly rotates on the mandrel 33. The liquid 35
`?lls the spaces formed by the interstices of the mesh and
`the spaces between the ?lament 34. As the material 35
`?lls the interstices of the compact stent 10, it cools and
`begins to form a semi-rigid mass.
`In step 51 excess material 35 is wiped from the stent
`l0 and the material 35 cures to produce an interdisposed
`restraining structure for maintaining the stent in its
`compact form. After the material 35 cures, it is possible
`to remove the ?lament 34 from the assembly. If this is
`an elastic material, then applying tension to the ?lament
`34 reduces its diameter slightly and facilitates its re
`moval from the cured material 35. This leaves the heli
`cal groove 22 shown in FIG. 3F that improves the
`overall ?exibility of the stent assembly 20. The stent 10
`remains in a compact form because the cured dissolv
`able material 35, such as cured gelatin, has sufficient
`strength to contain the stent 10.
`If the stent assembly 10 is being manufactured of a
`self-expanding material, the procedure may then use
`step 53 to install various termination elements, such as
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`end and tip bushings, as needed on the mandrel 30, and
`tem can be withdrawn along the guide wire 61 and
`removed from the body.
`step 54 to af?x a positioning, or steering device in the
`end bushing and to locate the stent assembly in a sheath.
`FIG. 7 depicts an embodiment in which a balloon
`During the manufacture of a stent assembly 20 that
`catheter 91 supports a stent assembly 20 as an example
`of a stent that requires an external force to expand. In
`relies on some external means for expansion, optional
`this particular embodiment a balloon 92 could consti
`step 55 is used to remove the mandrel 30 if that mandrel
`is not required in the ?nal assembly. If that mandrel is
`tute a mandrel 30 in FIG. 3B to support the stent assem
`bly 20. The remaining portions of the balloon catheter
`formed of a Silastic material, its removal is facilitated as
`include a central supporting catheter 93 typically with
`tensioning the material in an axial direction reduces its
`two lumens. A central lumen 94 receives a guide wire
`diameter and facilitates its removal from a central aper
`61. A second lumen 95 provides a passage for allowing
`ture along the axis of the assembly. In that case the
`a balloon control system 96 to in?ate and de?ate the
`structure that results from the manufacture appears as
`balloon 92. FIG. 7 also includes the markers 31 and 32
`the structure in FIG. 2 that is adapted for later installa
`at the opposite ends of the stent assembly 20.
`tion on an expansion or other device. Step 56 represents
`The delivery system in FIG. 7 may or may not be
`procedures for ?nally positioning the stent assembly 20
`constructed with a protective sheath. If the dissolvable
`on a support device.
`material is selected properly, it is possible to introduce
`FIG. 5 discloses an embodiment of a stent delivery
`the stent assembly into the body without any protective
`system that is adapted for positioning a self-expanding
`sheath. In such an embodiment, the body ?uids and the
`stent assembly in a vessel. As previously indicated with
`temperature will produce slow initial dissolution at the
`respect to steps 53 and 54, the impregnated stent assem
`circumferential surface 97 of the stent 20. This surface is
`bly 20 mounts on a tubular mandrel 30 with markers 31
`relatively smooth and the slight melting produces a
`and 32. A central aperture 60 through the tubular man
`lubricating function thereby to allow the structure to
`drel 30 enables the tube to slide over a guide wire 61. A
`transfer through the vessels with minimal trauma.
`tip bushing 62 includes a hollow shank portion 63 and
`Once the stent is located in a ?nal position, a sheath,
`an end portion 64. The shank portion 63 has an outer
`if used, is withdrawn. When the gelatin dissolves, the
`diameter that inter?ts with a distal end of a sheath 65
`stent 10 will be freed from the balloon catheter and
`and a center aperture 66 that ?ts snugly over the tubular
`pumping the balloon catheter expands the balloon 92
`mandrel 30. A central aperture 67 in the tip 61 aligns
`thereby forcing the stent 10 into its ?nal position. After
`with the central aperture 60 thereby to allow the guide
`this occurs, the balloon control system 96 de?ates the
`wire 61 to pass through the tip 62.
`balloon 92 and the entire balloon catheter 91 can be
`The proximal end of the sheath 65 terminates at a
`withdrawn along the guide wire 61.
`steering bushing 70 that includes a shank portion 71 that
`In summary, this invention provides an improved
`receives the proximal end of the sheath 65 and a head
`stent assembly that uses a cured, dissolvable material to
`portion 72. The steering bushing 70 has a central aper
`retain a stent in a compact form until it is properly
`ture or through hole 73 that allows the passage of a
`oriented within a vessel. Speci?c materials for contain
`pusher tube 74 therethrough. At its proximal end, the
`ing the stent are disclosed. Others may also exist or be
`pusher tube 74 terminates in a handle or thumb pad 75.
`developed that will shift from a liquid state to a solid
`At its distal end, the tube 74 engages an end bushing
`state at room temperature and shift back to a liquid state
`80. The end bushing 80 has a proximal shank portion 81
`at a controlled rate at temperatures normally encoun
`and a distal head portion 82. An aperture 83 is coexten
`tered in the body. The same material can be utilized
`sive with at least the head portion 82 and receives the
`with both self-expanding stents and stents that require
`proximal end of the mandrel 30. The shank portion 81
`some external source for expansion.
`has another aperture 84 that receives the distal end of
`A stent may be formed in compact form or be com
`the pusher tube 74. The diameter of the head portion 82
`pacted from a ?nal form. Different stents can comprise
`is selected so it can slide freely within the sheath 65.
`a wide variety of materials or combinations of materials.
`In use the guide wire 61 will be located in a body as
`The stents may be knitted, woven, formed, rolled, ex
`shown in FIGS. 5 and 6. Then the assembly, shown in
`truded or machined. The term “mesh” is exemplary
`FIG. 5, can be slid over the guide wire 61. During
`only. Some delivery systems may include external
`transport the tip bushing 62 seals the end of the stent
`sheaths around the stent assembly; others may not.
`delivery system and prevents any body ?uids 84 from
`When a sheath is desirable, the sheath can be very thin
`reaching the stent assembly 20 as the stent assembly
`because it only needs to provide a smooth exterior sur
`passes through various vessels 85 in tissue 86. Radio
`face. There is no requirement for the sheath having
`graphic or ?uoroscopic techniques provide ?nal loca
`sufficient strength to contain a stent. As a result, the
`tion information by imaging the markers 31 and 32. The
`55
`overall size of a stent delivery system decreases so it can
`physician can then withdraw the steering bushing 70
`transfer a stent assembly into smaller vessels. Other
`toward the pusher tube 74 thereby withdrawing the
`con?gurations of catheters and delivery systems could
`sheath 65 from the tip bushing 62. This exposes the stent
`be substituted for either self-expanding stents or stents
`assembly 20 to the body ?uids. The ?uids, through their
`requiring some external expansion source.
`temperature and constituents, dissolve the material 21,
`Although this stent assembly has been described in
`such as gelatin, over a controlled time interval. As the
`terms of particular cured dissolvable materials, stent
`gelatin dissolves, and shifts from a solid phase to a liquid
`materials and two speci?c stent delivery systems, it will
`phase the body ?uids ?ush the gelatin material, now in
`be apparent that many modi?cations can be made with
`the liquid phase, from the site and the stent 10 eventu
`the attainment of some or‘ all of the objects and advan
`ally expands into a ?nal form as shown in FIG. 6. When
`tages of this invention. Moreover it will be apparent
`65
`this occurs, the stent 10 has a much larger diameter than
`that many modi?cations can be made to the disclosed
`the overall diameter of the stent delivery system includ
`apparatus without departing from the invention. There
`ing the tip bushing 62, so the entire stent delivery sys
`fore, it is the intent of the appended claims to cover all
`
`60
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`40
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`50
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`010
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`such variations and modi?cations as come within the
`true spirit and scope of this invention.
`What is claimed as new and desired to be secured by
`Letters Patent of the United States is:
`1. A stent assembly for insertion in a vessel bounded
`by a vessel wall comprising:
`A. compact mesh stent means in a cylindrical form
`for expanding into engagement with a vessel wall,
`and
`B. cured, dissolvable means impregnating said mesh
`for containing said mesh in its compact form, said
`cured, dissolvable means transforming from a solid
`to a liquid state when said stent assembly is in posi
`tion in the vessel thereby to free said stent and
`enable its expansion into a vessel wall.
`2. A stent assembly as recited in claim 1 wherein said
`stent means consists of a ?lament formed of a biocom
`patible material that resists deformation in an expanded
`form.
`3. A stent assembly as recited in claim 1 wherein said
`stent assembly is disposed along a longitudinal axis and
`additionally comprises central support mean at the inte
`rior of said stent assembly that is concentric with the
`axis.
`4. A stent assembly as recited in claim 3 wherein said
`central support means includes means for expanding
`sa