United States Patent [19]
`Schmitt et al.
`
`111111111111111111111111111111111111111111111111111111111111111111111111111
`US005562725A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,562,725
`Oct. 8, 1996
`
`[54] RADIALLY SELF-EXPANDING
`IMPLANTABLE INTRALUMINAL DEVICE
`
`[75]
`
`Inventors: Peter J, Schmitt, Garnerville, N.Y.;
`David J. Lentz, Randolph, N.J.
`
`[73] Assignee: Meadox Medicals Inc., Oakland, N.J.
`
`[21] Appl. No.: 945,064
`
`[22] Filed:
`
`Sep. 14, 1992
`
`Int. Cl.6
`.................................. A61F 2/06; A61F 2/04
`[51]
`[52] U.S. Cl •.................................... 623/1; 623/12; 600/36
`[58] Field of Search .................................... 623/1, 11, 12;
`606/191-200; 600/36
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2,978,787
`3,095,017
`3,105,492
`3,272,204
`3,316,557
`3,317,924
`4,193,137
`4,719,837
`4,740,207
`4,743,250
`4,776,337
`4,820,298
`4,913,141
`4,917,699
`5,007,926
`5,078,726
`5,084,065
`5,108,416
`5,151,105
`5,383,925
`
`4/1961 Liebig .
`6/1963 Bleiler et al ..
`10/1963 Jeckel .
`9/1966 Artandi et al ..
`5/1967 Liebig .
`5/1967 LeVeen et al ..
`3/1980 Heck .
`1/1988 McConnell et al ..
`411988 Kreamer.
`5/1988 Kitagawa et al ..
`10/1988 Palmaz .
`4/1989 Leveen et al ............................... 623/1
`4/1990 Hillstead .
`411990 Chervitz .................................... 623/13
`4/1991 Derbyshire .
`111992 Kreamer .
`1/1992 Weldon et al ..
`4/1992 Ryan et al. .. ........................... 606/194
`911992 Kwan-Gett .
`111995 Schmitt ....................................... 623/1
`
`FOREIGN PATENT DOCUMENTS
`
`0183372Al
`0493788Al
`2548225Al
`2189150
`W083/0375
`8303752
`W088/00813
`8800813
`W088/06026
`8806026
`W090/15582
`9015582
`W091110766
`W092/16166
`
`6/1986
`7/1992
`1/1985
`10/1987
`1111983
`1111983
`2/1988
`2/1988
`811988
`811988
`1211990
`12/1990
`711991
`1011992
`
`European Pat. Off ..
`European Pat. Off ..
`France.
`United Kingdom .
`WIPO.
`WIPO ........................................ 62311
`WIPO.
`WIPO ........................................ 62311
`WIPO.
`WIPO ........................................ 62311
`WIPO.
`WIPO ........................................ 62311
`WIPO.
`WIPO.
`
`OTHER PUBLICATIONS
`
`R. T. Brown, ''Three-Dimensional Braiding", Handbook of
`Industrial Braiding. (Book publishing date unkown; how(cid:173)
`ever, book publishing date predates invention.).
`Zollikofer, C., et al., "Historical Overview of the Develop(cid:173)
`ment and Characteristics of Stents and Future Outlooks",
`Cardiovascular and Intreventional Radiology, 15, 272-278
`(1992).
`
`Primary Examiner-Debra S. Brittingham
`Attorney, Agent, or Firm-Hoffman & Baron
`
`[57]
`
`ABSTRACT
`
`A radially self-expanding implantable intraluminal device
`formed from a hollow tubular braid. The intraluminal device
`may be used in a variety of medical procedures which
`require a passageway to be maintained in an open position
`or which require reinforcement, support or a bypass conduit
`such as in blood vessels weakened by disease. The intralu(cid:173)
`minal device is longitudinally expanded or radially col(cid:173)
`lapsed for ease of insertion into a lumen and upon alignment
`within the lumen, the intraluminal device radially self(cid:173)
`expands to come into intimate contact with the inner surface
`of the lumen.
`
`0117072A1
`
`8/1984 European Pat. Off ..
`
`28 Claims, 3 Drawing Sheets
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 1
`
`

`

`U.S. Patent
`FIG-1
`
`Oct. 8, 1996
`
`Sheet 1 of 3
`
`5,562,725
`
`FIG-2
`
`FIG-3
`
`70
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 2
`
`

`

`U.S. Patent
`FIG-4
`
`Oct. 8, 1996
`
`Sheet 2 of 3
`
`5,562,725
`
`10
`
`FIG-Sa
`
`56
`
`54
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 3
`
`

`

`U.S. Patent
`FIG-5b
`
`Oct. 8, 1996
`
`Sheet 3 of 3
`
`5,562,725
`
`56
`
`55
`
`54
`
`55
`
`FIG-6
`
`6
`
`XI
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`I
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`68
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`~~~~~~~
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`
`68
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 4
`
`

`

`5,562,725
`
`1
`RADIALLY SELF-EXPANDING
`IMPLANTABLE INTRALUMINAL DEVICE
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to an implantable intralu(cid:173)
`minal device. More specifically, the present invention relates
`to a radially self-expanding implantable intraluminal device
`which is particularly useful for repairing or serving as a
`conduit for blood vessels narrowed or occluded by disease
`or for use in other body passageways requiring reinforce(cid:173)
`ment or the like.
`·Intraluminal devices or, more specifically, endovascular
`prosthesis, are known for treating stenosis, stricture, aneu(cid:173)
`rysm conditions and the like. These devices, which include
`stents and grafts, are generally implanted by a mechanical
`transluminal procedure. Stents are devices designed to hold
`open a constricting vessel and generally are not designed as
`conduits or bypass devices. Intraluminal or endoprosthetic
`grafts, on the other hand, are designed as internal bypass 20
`devices which relieve stress from the surrounding vessel
`wall. Often, a device of this type is percutaneously
`implanted within the vascular system to reinforce collaps(cid:173)
`ing, partially occluded, weakened or abnormally dilated
`localized sections of a blood vessel. Advantages of this 25
`method over conventional vascular surgery include obviat-
`ing the need for surgically exposing, incising, removing,
`replacing, or bypassing the defective blood vessel. Stents are
`often used in combination with other endoprosthesis, such as
`intraluminal grafts. In some cases a stent is positioned at 30
`each end of the graft, thus allowing the graft to serve as a
`conduit or internal support to relieve stress from the vessel
`wall. The stents on each end serve to keep the lumen open
`and to anchor the graft in place. Attachment of the graft to
`the stent can be accomplished with hooks or sutures. In some 35
`instances, the stent is attached to only one end of the
`intr'!luminal graft. In this case the graft is allowed to "float"
`in the downstream direction of the vessel.
`Structures which have previously been used as stents have 40
`included coiled stainless steel springs; helically-wound
`coiled springs manufactured from an expandable heat-sen(cid:173)
`sitive material; expanding stainless steel stents formed of
`stainless steel wire in a zig-zag pattern; cage-like devices
`made from malleable metal; and flexible tubes having a 45
`plurality of separate expandable ring-like scaffold members
`which permit radial expansion of the tube. Each of these
`devices is designed to be radially compressible and expand(cid:173)
`able so that they will easily pass through a blood vessel in
`a collapsed state and can radially expand to an implanted 50
`size after the problem area has been reached. None of these
`devices is designed to retain fluid.
`Each of the foregoing structures suffer from a number of .
`disadvantages. To begin with, current stents are not designed
`to be contractible once deployed and therefore a great deal 55
`of care must be taken to properly position and expand the
`device to the appropriate size. Over expansion of a stent
`places unnecessary stress on an already damaged vessel.
`Under expansion of the stent may result in inadequate
`contact with the inner wall of the vessel and migration of the 60
`stent may occur.
`Because the structures are designed to be delivered in a
`collapsed state within a blood vessel, it is difficult to ensure
`that the device, once deployed, will radially expand to the
`proper dimensions. For example, the expansion of a par- 65
`ticular coiled spring -type stent is predetermined by the
`spring constant and modulus of elasticity of the particular
`
`10
`
`2
`material used to manufacture the coiled spring structure.
`These same factors predetermine the amount of expansion of
`collapsed stents formed of stainless steel wire in a zig-zag
`pattern. Likewise, prostheses formed from heat sensitive
`5 material which expands upon heating have a predetermined
`amount of expansion based upon the alloy utilized in their
`manufacture.
`Another type of endovascular prosthesis consists of a thin
`wall textile radially fixed graft, which is folded up to fit
`inside an introducer sheath. The graft is manufactured to a
`predetermined diameter. If the graft is oversized, when
`displaced in the artery and subsequently expanded, the graft
`may not fully open leaving a fold or a crease in the graft
`which may further constrict an already narrowed or
`15 occluded blood vessel. On the other hand, if the graft is too
`small in diameter, it will slide around in the vessel and
`disrupt blood flow.
`As previously mentioned, intraluminal grafts are often
`used in combination with stents. Another disadvantage of
`the foregoing types of intraluminal devices is that once the
`device is deployed within the lumen, it is permanently and
`fully expanded and cannot be contracted for repositioning. It
`is advantageous to be able to realign an intraluminal graft
`which has been misdeployed through catheter malfunction
`or any other problem which may arise during the implan(cid:173)
`tation procedure. Generally, the present intraluminal devices
`once fully expanded cannot be easily moved within the
`lumen without surgery.
`When repairing blood vessels narrowed or occluded by
`disease, or repairing other body passageways, the device
`used in repairing or supporting the passageway must be
`flexible enough to negotiate the curves or bends of the body
`passageway. Most conventional endovascular prostheses do
`not have the requisite ability to bend so as to be advanta-
`geously placed within the vascular system.
`Accordingly, it would be desirable to develop a new and
`improved intraluminal device and, in particular, an intralu(cid:173)
`minal vascular graft that can be expanded to a variable size
`to accommodate the size of the diseased portion of the vessel
`and prevent migration of the graft away from the desired
`location and provide support functions similar to conven(cid:173)
`tional stents. The intraluminal grafts of the present invention
`are directed toward achieving this result as well as others
`including: preventing rupturing and/or erosion of the body
`passageway by the expanded graft; permitting tissue of an
`elongated section of a body passageway to be supported by
`an elongated graft; providing the necessary flexibility to
`negotiate the bends and curves of a vascular system; and
`being repositionable and adjustable even after being radially
`expanded within the lumen. Therefore, an intraluminal vas-
`cular graft which would overcome the foregoing difficulties
`and others while providing better and more advantageous
`overall results is highly desirable.
`
`SUMMARY OF THE INVENTION
`
`In accordance with the present invention, a new and
`improved radially self-expanding implantable intraluminal
`device is provided. More particularly, the present invention
`is formed from a hollow tubular braid which may be
`implanted intraluminally and thereafter radially self-ex(cid:173)
`pands to come in intimate contact with the inner surface of
`the lumen in which it is inserted.
`The device is preferably used as an endovascular pros(cid:173)
`thesis in which the device relieves the stress of weakened
`blood vessel, although it may be used in a variety of body
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 5
`
`

`

`5,562,725
`
`4
`such as a finger-like member, for grasping the braided device
`so that the device may be realigned to a proper position
`within the lumen. By pulling on one end of the intraluminal
`device of the present invention, the device will elongate in
`the longitudinal direction causing a decrease in diameter of
`the device such that it is free to move within the vessel,
`thereby permitting the device to be easily repositioned. Once
`in the repositioned location and no longer longitudinally
`elongated, the device of the present invention will once
`10 again radially self-expand to come into intimate contact with
`the inner surface of the lumen.
`One method of producing a radially self-expanding
`implantable intraluminal device includes radially expanding
`a hollow tubular braid and subjecting the radially expanded
`15 braid to conditions of time and temperature sufficient to set
`the material in the radially expanded position. As a conse(cid:173)
`quence of radial expansion, the device is shortened in length
`due to changes in the angle of the yarns with respect to the
`longitudinal axis. The braid is then permitted to cool while
`20 maintaining the braid in the radially expanded position. The
`heat source for heat conditioning the thermoplastic braid
`includes a convection oven, a heated mandrel, an infra-red
`light source or immersing the device in a hot liquid medium.
`The thermoplastic braid is preferably heated at a temperature
`25 of about 200° F. to about 700° F. for a time period of about
`five to thirty minutes. However, the heat parameters will
`vary depending upon the thermoplastic selected for forming
`the tubular braid. The heat conditioning of the thermoplastic
`yarns of the braid provides the intraluminal device of the
`30 present invention with memory to return the device to a
`radially expanded position following a reduction in diameter
`due to longitudinal expansion so that the device may be
`intraluminally inserted into a body passageway.
`In an alternative embodiment of the present invention, the
`intraluminal device may also include a means for attaching
`the device to the inner surface of the lumen to provide
`additional anchoring of the device. Such attaching means
`may include small hooks which are integrally formed on the
`outside or extraluminal surface of the device during the
`braiding process. Preferably, the hooks are integrally formed
`in at least one end of the device, although, depending upon
`the procedure being performed, both ends may include
`hooks. Anchoring means may also be added as a separate
`component if desired.
`A preferred form of the intraluminal device, as well as
`other embodiments, features and advantages of this inven(cid:173)
`tion will be apparent from the following detailed description
`of illustrative embodiments thereof, which is to be read in
`connection with the accompanying drawings.
`
`50
`
`3
`passageways to provide reinforcement of a supporting pasc
`sageway or the like. The implantable intraluminal device is
`both radially and longitudinally flexible or bendable. When
`the tubular braid is elongated in the longitudinal direction,
`the diameter of the device is decreased so that it may be 5
`percutaneously implanted within a body passageway. Once
`the device has been properly positioned within the body
`passageway, it is permitted to radially self-expand or self(cid:173)
`deploy to come in intimate contact with the interior surface
`of the body passageway.
`The hollow tubular braid may be formed from a number
`of natural and synthetic materials, including collagen, ther(cid:173)
`moplastics and metals. More specifically, thermoplastics
`which are useful include polyesters, polypropylenes, poly(cid:173)
`ethylenes, polyurethanes, or polytetrafiuoroethylenes and
`combinations and mixtures thereof. Useful metallic sub(cid:173)
`stances include stainless steel, titanium and nichol-chro(cid:173)
`mium alloys, among others. The hollow tubular braid is
`formed to be radially self-expanding by heat-conditioning
`the thermoplastic or metal fibers from which the device is
`made at a sufficient time and temperature to effectuate
`memory. The braid is heat-conditioned in a radially
`expanded or longitudinally compressed position to provide
`the radially self-expanding feature of the device. For
`example, if the thermoplastic chosen for making a tubular
`braid is polyester, the tubular braid is preferably heat con(cid:173)
`ditioned at a temperature from about 200° F. to about 700°
`F. for approximately five to thirty minutes and subsequently
`cooled while being maintained in a radially expanded posi(cid:173)
`tion, thereby effectuating memory within the braided device.
`The type of braid used to form the tubular device may be
`varied. More specifically, the intraluminal device of the
`present invention may be formed from a simple three yarn
`tubular braid (two-dimensional braid) or may be formed
`from a three-dimensional braid. The braid may also include 35
`a yarn which is used to stiffen the tubular braided structure
`and provide a greater radially expanding force. The expand(cid:173)
`ing radial force is preferably designed so that the intralu(cid:173)
`minal device will open up to be in intimate contact with the
`interior surface of the body passageway in which it is 40
`inserted and anchor itself thereto.
`Generally, the fibers used to form the braid have a denier
`in the range of20 to 500 denier, although deniers outside this
`range may have utility for specific applications. The force 45
`exerted by the device is non-rupturing, i.e., sufficient to open
`the device without causing damage to the vessel wall. The
`braid may be formed with a braid angle between 15° and
`about 90° and preferably about 54.50 to about 75° with
`respect to the longitudinal axis of the braided structure. The
`braid angle is measured from the longitudinal axis of the
`braided device.
`Once inserted into the body passageway, the intraluminal
`device will be permitted to radially self-expand and sub(cid:173)
`stantially conform to the shape and inner surface of the body 55
`passageway. The intraluminal device need not be perfectly
`sized to the vessel or passageway into which the device is
`inserted since the diameter of the device is infinitely variable
`in the ranges between its minimum diameter and its maxi(cid:173)
`mum diameter.
`An advantage of the radially self-expanding implantable
`intraluminal device of the present invention is that once it is
`inserted and permitted to self-expand, the device may still be
`repositioned or realigned if not properly positioned within
`the lumen. A method of repositioning an implanted intralu(cid:173)
`minal device of the present invention includes introducing a
`guide wire having on its distal end a means or mechanism,
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`60
`
`FIG. 1 is a side elevational view of the intraluminal device
`of the present invention shown in a radially expanded
`position;
`FIG. 2 is a side elevational view of the intraluminal device
`of the present invention shown in a longitudinally expanded,
`radially collapsed insertion position;
`FIG. 3 is a side elevational view of an embodiment of the
`present invention showing anchors positioned at one end of
`the intraluminal device;
`FIG. 4 is a side perspective partial cutaway view of an
`implanted intraluminal device of the present invention and a
`65 guidewire for repositioning the intraluminal device;
`FIG. Sa is a cross-sectional view of a prior art stent-graft
`combination in an unexpanded state;
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 6
`
`

`

`5,562,725
`
`5
`FIG. Sb is a cross-sectional view of a prior art stent-graft
`combination in an expanded state within a lumen; and
`FIG. 6 is a side elevational view of a stent-graft combi(cid:173)
`nation of the present invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`5
`
`6
`The tubular braid is preferably a simple, conventional
`two-dimensional braid formed from two sets of yams spi(cid:173)
`ralling in opposing directions about a longitudinal axis of the
`tube being formed. The braid angle (helix angle) of the
`tubular braid is the angle in relation to the longitudinal axis
`of the tube being formed and may vary from about 15° to
`70°. The tubular braid is formed so that the yam components
`20 can scissor through severe angle changes thereby altering
`the diameter of the tubular structure. In this regard, a tubular
`braid can be formed which can be radially collapsed or
`longitudinally extended or elongated to form a small diam(cid:173)
`eter for implanting intraluminally into a body passageway.
`Following insertion and positioning within the lumen, the
`device of the present invention will radially self-expand or
`longitudinally compress to form a relatively large diameter
`tube by causing the yams 20 to scissor to the larger diameter.
`This type of braided structure maintains structural integrity
`even when undergoing these geometric changes because the
`two opposing yam systems are interwoven. The yams 20 are
`sufficiently spaced to allow them to move freely in place. As
`20 can be seen comparing a radially collapsed tubular braid
`shown in FIG. 2 with a radially expanded tubular braid
`shown in FIG. 1, the space between the yams will decrease
`as the diameter increases.
`For example, FIG. 1 illustrates a tubular braid of the
`25 present invention in its radially expanded state 10 and FIG.
`2 illustrates the same tubular braid in its radially collapsed
`state 30. In the radially collapsed state, the tubular braid may
`have a diameter of 6 millimeters whereas in the radially
`expanded state the diameter may be 18 millimeters. In this
`30 example, the diameter increase is three fold, and therefore,
`the ratio of the sine of the helix angle for the radially
`expanded tubular braid should be three times that for the
`radially collapsed tubular braid. If the helix angle is 15°
`when the diameter of the tube is 6 millimeters, then the helix
`angle when the diameter is increased will be about 51 o. This
`is mathematically proven by taking the sine of 15° which is
`0.2588, multiplying this value by three to yield 0.7764 and
`taking the inverse sine to arrive at a helix angle of about 51 o
`and a diameter of 18 mm.
`Another characteristic of the tubular braided structure of
`the present invention which makes it highly desirable for use
`as an endovascular prosthesis is the flexibility of the struc(cid:173)
`ture. In a diseased or occluded blood vessel, the blood flow
`may be distorted or disturbed due to irregularities on the
`inner surface of the blood vessel as well as the bends or
`curves of the vessel. The tubular braided structure of the
`present invention is highly flexible and bendable both in the
`radial and longitudinal directions, can negotiate any curves
`or bends formed in the blood vessel and can conform to
`inner surface conditions found within the blood vessel. The
`tubular braid can be bent to angles approaching 180° and
`still maintain an open lumen through the bend. The yams 20
`used to produce the flexible tubular braid preferably have a
`denier in the range of 20 to 500 denier whereby the smaller
`the yam denier, the finer or thinner the yam.
`The selection of the yam denier, type of yam and braid
`angle and the number of carriers will also determine the
`porosity of the structure. These factors also dictate the
`strength and diameter of the device. The intraluminal device
`of the present invention is most likely to be used to support
`a weakened body passageway or maintain an opening in an
`occluded body passageway. Accordingly, the porosity of the
`device should be sufficient to allow ingrowth of surrounding
`tissue into the structure to encourage assimilation and
`anchorage of the device within the body passageway.
`The yams 20 used to form the tubular braid are preferably
`thermoplastics and metallic material. Suitable thermoplastic
`
`10
`
`15
`
`FIGS. 1 and 2 illustrate a radially self-expanding implant(cid:173)
`able intraluminal device formed from a hollow tubular
`thermoplastic braid. For purposes of describing the present
`invention, the terms "intraluminal device" and "radially
`self-expanding prosthesis" are interchangeably used in
`describing the methods, apparatus and structures of the
`present invention. The intraluminal device may be used not
`only as an intraluminal vascular graft for supporting a
`diseased or damaged vessel, but its radially self-expanding
`capabilities give it a stent-like feature for expanding par(cid:173)
`tially occluded segments of a blood vessel or body passage(cid:173)
`way. Many other procedures which require a radially
`expandable prosthesis for a variety of body passageways are
`contemplated.
`The intraluminal device of the present invention may
`especially be used in the following procedures: supportive
`graft placement within blocked blood vessels opened by
`transluminal recanalization, but which are likely to collapse
`in the absence of an internal support; a supporting graft
`structure following passage of a catheter through vessels
`occluded by inoperable cancers; supportive graft placement
`of narrowing of the esophagus, the intestine and the urethra;
`and supportive graft reinforcement of reopened and previ(cid:173)
`ously obstructed bile ducts. Accordingly, the terms "pros(cid:173)
`thesis" and "intraluminal device" encompass the foregoing
`usages within various body passageways or lumens. Further
`in this regard, the term "body passageway" encompasses
`any duct within the human body, such as those previously
`described, as well as any vein, artery or blood vessel within
`the human vascular system.
`FIGS. Sa and 5b illustrate a prior art graft-stent combi(cid:173)
`nation used to open constricted lumens as well provide a 40
`support for a weakened lumen. Referring to FIG. Sa, an
`unexpanded stent 52 is illustrated positioned within a graft
`54. The graft 54 is attached to the stent 52 by means of
`sutures 56. As illustrated in FIG. Sb, this stent-graft com(cid:173)
`bination may be inserted into a body lumen and once 45
`correctly positioned, the stent 52 is radially expanded to
`bring the stent-graft combination into contact with the inner
`wall of the lumen 58. The graft 54 is pressed against the
`inner wall of the lumen 58 by the expansion of the stent 52.
`The diameter of the graft shown in FIG. Sb was oversized 50
`and upon expansion by the stent, folds or creases 55 were
`formed in the graft because the graft could not be fully
`expanded. The folds 55 may further weaken an already
`weakened lumen by placing excessive force on the lumen in
`the areas of contact. Accordingly, it would be advantageous 55
`to be able to properly size the stent-graft combination to
`form a more exact fit within the lumen.
`FIG. 1 illustrates a preferred embodiment of the present
`invention in its radially expanded position. The intraluminal
`device of the present invention is in the form of a hollow 60
`tubular braid. The tubular braid may be any type of braid, for
`example either a simple, conventional braid, i.e., a two(cid:173)
`dimensional braid, or a three-dimensional braid. A braided
`structure is ideally suited for making tubular structures
`which can radially expand and contract, thereby forming a 65
`structure with an infinitely variable diameter within certain
`minimum and maximum values.
`
`35
`
`Medtronic and Medtronic Vascular
`Exhibit 1011 - Page 7
`
`

`

`5,562,725
`
`10
`
`7
`materials for forming the braid of the intraluminal device of
`the present invention include but are not limited to polyester,
`polypropylene, polyethylene, polyurethane and polytetraf(cid:173)
`louroethylene. Suitable metallic materials for forming the
`braid of the intraluminal device of the present invention
`include but are not limited to stainless steel, titanium and a
`nickel-chromium alloys, among others. A thermoplastic yarn
`is preferably used so that, upon heat conditioning in the
`radially expanded state the braid becomes heat set with
`elastomeric memory and a natural tendency to return to this
`position. Thus, the braided device is radially self-expanding
`when restraining forces are removed. The braid may be
`formed on a mandrel having the diameter equal to the
`maximum expanded diameter of the braid. Alternatively, the
`tubular braid can be braided at a smaller diameter and heat
`set at a larger diameter. Thus, when the intraluminal device
`is in an unstressed condition, the tubular braid will be in the
`radially expanded state. The heat conditioning of the ther(cid:173)
`moplastic braid effectuates memory. More specifically, the
`tubular braid contracts in diameter when placed under
`longitudinal stress, or in other words, radially compresses. 20
`When the longitudinal stress is removed, the tubular braid
`radially self-expands or returns to its original position or
`diameter, i.e., approximately the diameter at which the
`device was heat conditioned or the diameter of the vessel in
`which it is contained. The tubular braid of the present 25
`invention may also include a stiffening component, such as
`polymeric or metallic wires, to add a greater degree of
`stiffness, rigidity and resiliency to the structure. The stiff(cid:173)
`ening component could also provide the intraluminal device
`of the present invention with a greater self-expanding or
`spring-like force. Additionally, the tubular braid of the 30
`present invention may include axial yarns which are braided
`into the structure to limit or control the amount of expansion
`of the device when in an unstressed state.
`The method for making the intraluminal device of the
`preferred embodiment includes forming a tubular braid from
`a yarn and preferably a thermoplastic yarn. The tubular braid
`is preferably formed having a small diameter and is there(cid:173)
`after placed in a radially expanded state for heat condition(cid:173)
`ing. A preferred method for heat conditioning includes 40
`placing the tubular braid on a mandrel so that the braid is
`radially expanded. The radially expanded thermoplastic
`braid is then heat-conditioned or heat set at a sufficient time
`and temperature to effectuate memory. The heating time and
`temperature is dependent upon the yarn material chosen to 45
`form the braid. Upon completion of the heating process, the
`tubular braid is cooled while maintaining the braid in the
`radially expanded position.
`For example, if the thermoplastic chosen is polyester, the
`radially expanded tubular braid is preferably heat condi(cid:173)
`tioned at a temperature between 300° F. and 400° F. for
`approximately ten to thirty minutes. The heating process
`may be accomplished by a variety of heating methods. The
`heating methods include but are not limited to the use of a
`convection oven, an infra-red light source, immersing the
`tubular braid in a hot liquid medium or by heating the
`mandrel on which the tubular braid is radially expanded.
`Following heat conditioning, the tube is maintained in the
`radially expanded position and cooled to ambient tempera(cid:173)
`ture. An additional step in the process optionally includes a
`cleaning or scouring process of the tubular braid prior to or
`following heat conditioning in order to remove any residuals
`which may be present on the tube from the braiding process.
`The cleaning is preferably performed using water or com(cid:173)
`patible solvents and cleaning agents.
`The advantage of using the thermoplastic yarn and heat
`treating the tubular braid is that the intraluminal device
`
`8
`formed by this process is radially self-expanding. Thus, the
`intraluminal device of the present invention does not require
`expansion in-vivo by a balloon catheter, such as the majority
`of mechanical stents available for use as an endovascular
`5 prosthesis. The intraluminal braided device of the present
`invention is radially self-expanding and has the stent feature
`inherently incorporated into the device.
`The present devices can be effectively used in combina(cid:173)
`tion with other prosthetic devices such as stents as illustrated
`in FIG. 6. This alternative embodiment of a stent-graft
`combination includes at least one stent 62, coupled to an
`intraluminal device 66 formed in accordance with the
`present invention. The stent 62 is secured to the end of the
`intraluminal device 66 by means of hooks or sutures 68. The
`stent 62 serves to keep the lumen open and to enhance
`15 anchoring the intraluminal device 66 in position. The
`intraluminal device 66 formed in accordance with the
`present invention is radially self-expanding and, therefore
`radially expands along with the expansion of the stent. The
`intraluminal device 66 may be used to support a weakened
`or diseased vessel.
`As previously mentioned, tubular endoprothesis devices,
`i.e., intraluminal grafts, have been used in combination with
`stents which were not self-expanding or radially adjustable.
`Also these tubular endoprosthetic devices were fixed in
`diameter and were therefore not capable of being radially
`adjustable. Thus, this conventional combination use of stent
`and tubular endoprosthetic device required special attention
`to the diameter size of the endoprosthesis such that it was
`large enough to allow for full expansion of the stent which
`was placed within it.