6,141,855
`[11] Patent Number:
`[19]
`Unlted States Patent
`
`Morales
`[45] Date of Patent:
`Nov. 7, 2000
`
`USOO6141855A
`
`[54]
`
`[75]
`
`STENT CRIMPING TOOL AND METHOD OF
`USE
`
`5,810,871
`5,810,873
`
`.......................... 606/198
`9/1998 Tuckey et al.
`9/1998 Morales .................................. 606/198
`
`Inventor: Stephen A. Morales, Mountain View,
`Calif.
`
`(LISt continued on next page.)
`FOREIGN PATENT DOCUMENTS
`
`[73] Assignee: Advanced Cardiovascular Systems,
`~
`Inc" sama Clara’ cahf‘
`
`[21] Appl. No.: 09/069,010
`
`[22]
`
`Filed:
`
`Apr. 28, 1998
`
`Sumpean Eat. 83 '
`8 :3: 3:? 10/1998
`uropean a .
`.
`.
`159065
`2/1921 United Kingdom .
`WO 98/14120
`4/1998 WIPO .
`W0 98/19633
`5/1998 WIPO .
`
`OTHER PUBLICATIONS
`
`Int. Cl.7 ............................. B23P 11/00; B21D 39/00
`[51]
`[52] US. Cl.
`................................. 29/516; 606/1; 606/108;
`606/198; 623/1; 29/282
`[58] Field of Search .................................... 29/282, 283.5,
`29/515, 516, 517, 715; 606/1, 108, 198;
`623 1
`/
`
`[56]
`
`,
`References Clted
`U.s. PATENT DOCUMENTS
`
`US. application No. 08/795,335, filed Feb. 4, 1997.
`US. application No. 08/837,771, filed Apr. 22, 1997.
`US. application No. 08/089,936, filed Jul. 15, 1997.
`US. application No. 08/962,632, filed Nov. 3, 1997.
`The eXTraordinary Stent, C.R. Bard Brochure (Undated).
`Primary Examiner—David P. Bryant
`Assistant Examiner—Essama Omgba
`Attorney, Agent, or Firm—Fulwider Patton Lee & Utecht,
`LLP
`
`.
`
`696,289
`4,572,132
`4,644,936
`4,681,092
`4,697,573
`4:901:707
`4,907,336
`5,132,066
`5,133,732
`5,183,085
`5,189,786
`5,437,083
`5,546,646
`5,626,604
`596307830
`576537691
`5,693,066
`5’738’674
`5,746,764
`5 782 855
`’
`’
`5,782,903
`5,783,227
`5,785,715
`5,810,838
`
`3/1902 Williams .
`213:: Egg?“ et al’ ’
`2/1987 Schiff.
`7/1987 Cho et. a1.
`10/1987 Schiff .
`2/1990 Schiff .
`3/1990 Gianturco .
`7/1992 Charlesworth et a1.
`7/1992 Wiktor .
`2/1993 Timmermans .
`3/1993 Ishikawa et a1.
`8/1995 Williams et a1.
`8/1996 Williams et a1.
`5/1997 Cottone; JT-
`-
`5/1997 Verbeek.
`8/1997 RuPP 6t a1~ ~
`............................. 606/198
`12/1997 Rupp et al.
`4/1998 Wllhams et al'
`'
`5/1998 Green et al.
`.
`7/1998 Lau et al.
`................................ 606/194
`.
`7/1998 Wlktor
`........................................ 623/1
`7/1998 Dunham .
`7/1998 Schatz .
`9/1998 Solar ....................................... 606/108
`
`.
`
`.
`.
`.
`
`ABSTRACT
`[57]
`A stent crimping tool for firmly and uniformly crimping a
`stent onto a balloon catheter. The stent crimping tool is
`constructed by curving and overlapping the ends of a
`flexible Mylar sheet and inserting the end portions through
`a thin slot of a rigid panel. The uncrimped stent and catheter
`assembly are placed within a cylindrical space formed by the
`curved and overlapping flexible sheet. A force is applied to
`the overlapping end portions to pull
`the flexible sheet
`through the slot thereby collapsing the cylindrical space and
`crimping the stent, held therein, onto the balloon. In another
`embodiment, the crimping tool is constructed from a mount
`having a grooved top with steeply sloped sides. The
`uncrimped catheter-stent assembly is placed on the mount
`and rests within the groove. A flexible sheet of Mylar is
`draped over the catheter-stent assembly and a downward
`force is applied to the end portions of the flexible sheet. This
`downward force places the flexible sheet in tension thereby
`-
`th
`th t
`t
`t
`bl b t
`.t
`d th
`compressmg 8“ e “'5 en 855631 y e ween 1 an
`e
`. A
`d1n 1
`the stent 1s crim ed onto the balloon
`mount
`CC“
`g y’
`p
`catheten
`
`13 Claims, 5 Drawing Sheets
`
` Edwards Lifesciences v.
`
`US. Patent N0. 6,915,560
`IPR2017-00444 EX. 2049
`
`Boston Scientific
`
`Page 1 of 12
`
`Page 1 of 12
`
`

`

`6,141,855
`
`Page 2
`
`US. PATENT DOCUMENTS
`
`5,951,569
`
`9/1999 Tuckey et a1.
`
`.......................... 606/108
`
`1
`t
`5836952 111998 D .
`606/108
`58939852
`441999 M1251; a"
`
`5,893,867
`4/1999 Bagaoisan et al.
`.. 606/198
`7/1999 Morales .........
`5920975
`29/282
`
`.. 606/194
`8/1999 Morales .....
`5,931,851
`8/1999 Green et a1.
`.. 606/194
`5,944,735
`
`9/1999 Morales .....
`.. 606/198
`5,947,993
`9/1999 Solovay .................................... 156/86
`5,948,191
`
`5,972,016
`5,974,652
`6,009,614
`6,024,737
`6,051,002
`6,063,092
`6,063,102
`6,074,381
`
`10/1999 Morales .................................. 606/198
`11/1999 Kimesetal.
`............................. 29/516
`1/2000 Morales .................................... 29/516
`2/2000 Morales ...................................... 606/1
`4/2000 Morales .................................. 606/108
`5/2000 Shin ........................................ 606/108
`
`5/2000 Morales
`.606/198
`.................................. 606/1
`6/2000 Dinh et al.
`
`Page 2 of 12
`
`Page 2 of 12
`
`

`

`US. Patent
`
`Nov. 7, 2000
`
`Sheet 1 0f 5
`
`6,141,855
`
`
`
`
`
`E§§mfi§§efi§§$¥§§§§k“§%%s$§$m\xm§§m.
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`
`Page 3 of 12
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`Page 3 of 12
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`

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`U.S. Patent
`US. Patent
`
`Nov. 7, 2000
`Nov. 7, 2000
`
`Sheet 2 of 5
`Sheet 2 0f 5
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`6,141,855
`6,141,855
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`Page 4 of 12
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`

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`U.S. Patent
`US. Patent
`
`Nov. 7, 2000
`Nov. 7,2000
`
`Sheet 3 of 5
`Sheet 3 0f5
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`6,141,855
`6,141,855
`
`7 4O
`
`?
`
`
`
`
`
`F/G. 4B
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`Page 5 of 12
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`U.S. Patent
`US. Patent
`
`Nov. 7, 2000
`Nov. 7,2000
`
`Sheet 4 of 5
`Sheet 4 0f5
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`6,141,855
`6,141,855
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`

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`U.S. Patent
`US. Patent
`
`Nov. 7, 2000
`Nov. 7,2000
`
`Sheet 5 of 5
`Sheet 5 0f5
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`6,141,855
`6,141,855
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`48
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`IO
`I0
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`F/G, 6
`F/G. 6
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`6,141,855
`
`1
`STENT CRIMPING TOOL AND METHOD OF
`USE
`
`2
`to ensure the proper crimping of a stent onto a catheter in a
`uniform and reliable manner.
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to an apparatus for loading
`a tubular graft, such as a stent, onto the distal end of a
`catheter assembly of the kind used, for example, in percu-
`taneous transluminal coronary angioplasty (PTCA) or per-
`cutaneous transluminal angioplasty (PTA) procedures.
`In typical PTCA procedures, a guiding catheter is percu-
`taneously introduced into the cardiovascular system of a
`patient through the brachial or femoral arteries and advanced
`through the vasculature until the distal end of the guiding
`catheter is in the ostium. A guide wire and a dilatation
`catheter having a balloon on the distal end are introduced
`through the guiding catheter with the guide wire sliding
`within the dilatation catheter. The guide wire is first
`advanced out of the guiding catheter into the patient’s
`coronary vasculature and the dilatation catheter is advanced
`over the previously advanced guide wire until the dilatation
`balloon is properly positioned across the arterial
`lesion.
`Once in position across the lesion, a flexible and expandable
`balloon is inflated to a predetermined size with a radiopaque
`liquid at relatively high pressures to radially compress the
`atherosclerotic plaque of the lesion against the inside of the
`artery wall and thereby dilate the lumen of the artery. The
`balloon is then deflated to a small profile so that
`the
`dilatation catheter can be withdrawn from the patient’s
`vasculature and the blood flow resumed through the dilated
`artery. As should be appreciated by those skilled in the art,
`while the above-described procedure is typical, it is not the
`only method used in angioplasty.
`In angioplasty procedures of the kind referenced above,
`restenosis of the artery may develop over time, which may
`require another angioplasty procedure, a surgical bypass
`operation, or some other method of repairing or strengthen-
`ing the area. To reduce the likelihood of the development of
`restenosis and to strengthen the area, a physician can implant
`an intravascular prosthesis for maintaining vascular patency,
`commonly known as a stent, inside the artery at the lesion.
`The stent is crimped tightly onto the balloon portion of the
`catheter and transported in its delivery diameter through the
`patient’s vasculature. At the deployment site, the stent is
`expanded to a larger diameter, often by inflating the balloon
`portion of the catheter. The stent also may be of the
`self-expanding type.
`Since the catheter and stent travel through the patient’s
`vasculature, and probably through the coronary arteries, the
`stent must have a small delivery diameter and must be firmly
`attached to the catheter until
`the physician is ready to
`implant it. Thus, the stent must be loaded onto the catheter
`so that it does not interfere with delivery, and it must not
`come off the catheter until it is implanted.
`In procedures where the stent is placed over the balloon
`portion of the catheter, it is necessary to crimp the stent onto
`the balloon portion to reduce its diameter and to prevent it
`from sliding off the catheter when the catheter is advanced
`through the patient’s vasculature. Non-uniform crimping
`can result in sharp edges being formed along the now uneven
`surface of the crimped stent. Furthermore, non-uniform stent
`crimping may not achieve the desired minimal profile for the
`stent and catheter assembly. Where the stent is not reliably
`crimped onto the catheter, the stent may slide off the catheter
`and into the patient’s vasculature prematurely as a loose
`foreign body, possibly causing blood clots in the
`vasculature, including thrombosis. Therefore, it is important
`
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`This crimping is often done by hand, which can be
`unsatisfactory due to the uneven application of force result-
`ing in non-uniform crimps. In addition,
`it
`is difficult
`to
`visually judge when a uniform and reliable crimp has been
`applied.
`Some self-expanding stents are difficult to load by hand
`onto a delivery device such as a catheter. Furthermore, the
`more the stent is handled the higher the likelihood of human
`error, which would be antithetical to a properly crimped
`stent. Accordingly, there is a need in the art for a device for
`reliably crimping a stent onto a catheter.
`There have been attempts at devising a tool for crimping
`a stent onto a balloon delivery catheter. An example of such
`a tool comprises a series of plates having substantially flat
`and parallel surfaces that move in a rectilinear fashion with
`respect to each other. A stent carrying catheter is disposed
`between these surfaces, which surfaces crimp the stent onto
`the outside of the catheter by their relative motion and
`applied pressure. The plates have multiple degrees of free-
`dom and may have force-indicating transducers to measure
`and indicate the force applied to the catheter during crimp-
`ing of the stent.
`loading tool design is comprised of a
`Another stent
`tubular member housing a bladder. The bladder is inside a
`guide catheter. The tubular member and bladder are con-
`structed to hold a stent that is to be crimped onto a balloon
`catheter assembly. Upon placement of the stent over the
`balloon portion of the catheter, a valve in the loading tool is
`activated to inflate the bladder. The bladder compresses the
`stent radially inward to a reduced diameter onto the balloon
`portion of the catheter to achieve a snug fit. In this way, the
`stent is crimped onto the distal end of a balloon catheter with
`a minimum of human handling. The foregoing stent crimp-
`ing tools are disclosed in, for example, US. Pat. Nos.
`5,437,083 and 5,546,646 to Williams et al.
`Yet another stent crimping tool is known in the art as the
`BARD XT, which is actually a stent loader. It is constructed
`of a tubular body with a ball at one end connected to a
`plurality of long, thin strips passing through the rigid tubular
`body. An uncrimped stent is placed over the plurality of
`long, thin strips, which hold the stent in an expanded state.
`The balloon portion of a catheter is inserted into the cylin-
`drical space formed by the plurality of strips. When the user
`pulls on the ball while holding the tubular body against the
`stent, the strips are slid from beneath the stent and the stent
`is transferred onto the balloon portion.
`Still another conventional stent crimping tool is manu-
`factured by Johnson & Johnson and appears similar to a
`hinged nutcracker. Specifically, the tool is comprised of two
`hand operated levers hinged at one end and gripped in the
`palm of the hand at the opposite end. A cylindrical opening
`holding a crimping tube is provided through the mid-portion
`of the tool to receive therein a stent loaded onto a balloon
`
`catheter. The crimping operation is performed by the user
`squeezing the handle thereby pressing the crimping tube
`which in turn pinches the stent onto the balloon catheter.
`SUMMARY OF THE INVENTION
`
`Both PTCA and PTA procedures have become common-
`place in treating stenoses or lesions in blood vessels and
`coronary arteries. In approximately 35% to 40% of the
`procedures,
`restenosis may develop requiring a further
`angioplasty, atherectomy or bypass procedure to return the
`patency of the vessel. Intravascular stents are now being
`
`Page 8 of 12
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`Page 8 of 12
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`

`

`6,141,855
`
`3
`deployed after PTCA and PTA procedures, and after
`atherectomies, in order to help prevent the development of
`restenosis. Importantly, such stents, mounted on the balloon
`portion of a catheter, must be tightly crimped to provide a
`low profile delivery diameter, and to ensure that the stent
`stays on the balloon until the balloon is expanded and the
`stent is implanted in the vessel.
`The present invention is directed to a crimping tool that
`can repeatedly provide a uniform and tight crimp to ensure
`the low profile diameter of the stent on the balloon portion
`of the catheter, and to ensure that the stent remains firmly
`attached until it is implanted in the vessel by expanding the
`balloon. More precisely, the present invention is directed to
`a tool for crimping a stent onto a balloon catheter comprising
`a sheet of flexible material having a central portion and end
`portions, wherein the sheet is curved so that the end portions
`overlap. The present invention tool further comprises a rigid
`panel having a top side and a bottom side, and having a thin
`slot therethrough, a cylindrical space defined by the curved
`sheet, wherein the uncrimped stent is placed over the cath-
`eter to form a catheter-stent assembly, and wherein the
`catheter-stent assembly is disposed within the cylindrical
`space, wherein the overlapping end portions pass through
`the slot of the rigid panel so that the cylindrical space is
`disposed at the top side and the overlapping end portions are
`at
`the bottom side, and wherein the user pulls on the
`overlapping ends to collapse the sheet forming a signifi-
`cantly narrower cylindrical space thereby crimping the stent
`onto the catheter. In the preferred embodiment, the sheet of
`flexible material is made of Mylar. Further, to reduce friction
`between the Mylar sheet and the rigid panel, it is desirable
`to have a rounded edge around the thin slot.
`To maximize the crimp on the stent to closely approxi-
`mate the circle of the balloon catheter, the radius of curva-
`ture of the Mylar should not be less than the radius of
`curvature of the crimped stent. This demands that at the
`transition between the crimping portion of the Mylar and the
`part that is pulled through the thin slot, the Mylar must be
`plastically deformed. Indeed, the Mylar sheet undergoes a
`significant amount of stress at the point where it slides into
`the thin slot because, by design, it is expected to undergo a
`180 degree turn.
`If the Mylar sheet were preformed or prestressed, it might
`be better suited to achieving a near perfect circle. The perfect
`circle would translate to a more circular shape crimp on the
`stent. Also, the slot size could be reduced, which would
`allow an even closer approximation of the cylindrical shape
`over smaller sized balloons and stents.
`
`Optionally, a rigid mandrel may be disposed within the
`guide wire lumen of the balloon catheter to help the structure
`maintain its shape during the crimping process. Thus, as the
`sheet squeezes down on the stent to crimp it to the balloon,
`the rigid mandrel resists the downward force and prevents
`the balloon from collapsing and losing its shape longitudi-
`nally.
`In an alternative embodiment, the present invention stent
`crimping tool can be adapted to an actuator. The actuator
`may be spring loaded or pneumatically operated. For
`example, the user would initiate the actuator by moving a
`lever to release the spring which is biased to pull
`the
`overlapping end portions away from the panel thus tightly
`collapsing the cylindrical space thereby crimping the stent
`onto the balloon catheter. Alternatively, a piston disposed
`inside a fluid operated cylinder is connected to the overlap-
`ping end portions of the sheet. When actuated, the cylinder
`fills with fluid thereby displacing the piston and pulling the
`
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`65
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`4
`overlapping end portions away from the rigid panel thereby
`again collapsing the cylindrical space around the catheter-
`stent assembly and performing the stent crimping operation.
`The foregoing are examples of time saving, high force
`generating devices to be preferably incorporated into a high
`production procedure.
`the present invention is
`In an alternative embodiment,
`directed to a tool for crimping a stent onto a catheter wherein
`the tool is mounted to a fixture, comprising a sheet of
`flexible material having a central portion and opposite end
`portions, a mount having a raised end grooved support
`surface with sloping sides, mounted to the fixture, wherein
`the uncrimped stent is mounted on the catheter and the
`catheter-stent assembly is placed on the grooved support
`surface which corresponds to the features of the stent,
`wherein the user curves the sheet to conform the central
`portion of the flexible sheet to the catheter-stent assembly,
`and so that the end portions overlie the sloping sides of the
`mount, and whereby the user pulls on the end portions to
`crimp the stent onto the catheter.
`In the preferred
`embodiment, the grooved support surface has a preferably
`semicircular cross-sectional shape. Furthermore, the sloping
`sides of the mount have low friction surfaces. Moreover, the
`sheet of flexible material is preferably made from Mylar.
`During the stent crimping operation, the Mylar is pulled
`down over the mount, effectively squeezing the stent over
`the balloon portion of the catheter and the mount. By forcing
`at least one row of cells in the stent length to collapse, the
`stent should theoretically fit over the balloon perfectly,
`assuming correct sizing of the semicircular mount and
`assuming negligible friction between the stent and the Mylar
`sheet.
`
`To insure secure and proper stent crimping, the Mylar
`should be released and the catheter-stent assembly rotated,
`and the foregoing process repeated. Again, an optional
`mandrel can be inserted into the guide wire lumen of the
`balloon catheter. During the repeated stent crimping process,
`the limit of deformation and crimping is reached when the
`radial forces encounter the mandrel, which resist further
`deformation and resultant decreases in the stent diameter.
`
`The present invention tool is thus capable of homoge-
`neously and precisely crimping a stent onto a balloon
`catheter. Such a crimping tool
`is highly useful
`to
`cardiologists, for example. Such physicians are constantly
`concerned with proper deployment of the stent within the
`patient that is desirable to have a consistently and reliably
`crimped stent. The present invention tool is further a time
`saver, because the stent crimping procedure can be per-
`formed efficiently and quickly. Indeed,
`these and other
`advantages of the present invention will become apparent
`from the following detailed description thereof when taken
`in conjunction with the accompanying exemplary drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a side elevational view partially in section,
`depicting a stent that has been crimped onto a delivery
`catheter and disposed within a vessel.
`FIG. 2 is a perspective view of a preferred embodiment
`stent crimping tool showing the curved flexible sheet pass-
`ing through a slot formed in a rigid panel.
`FIG. 3 is a side elevational view of the embodiment
`shown in FIG. 2.
`
`FIGS. 4A, 4B, and 4C depict an alternative embodiment
`wherein the flexible sheet is creased or prestressed to create
`90 degree angles that interact with the edges of the slot.
`FIGS. 5A and 5B are front elevational and side elevational
`
`respectively, of an alternative embodiment stent
`views,
`crimping tool using a mount.
`
`Page 9 of 12
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`Page 9 of 12
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`

`6,141,855
`
`5
`FIG. 6 is a front elevational view of the alternative
`embodiment shown in FIG. 5A, wherein the stent is under-
`going the crimping procedure.
`FIG. 7 is a front elevational view of the embodiment
`shown in FIG. 5A, wherein the pressure on the flexible sheet
`has been released to rotate the catheter-stent assembly.
`FIG. 8 is a front elevational view of the alternative
`embodiment shown in FIG. 5A wherein the flexible sheet is
`pulled downward to continue the crimping procedure.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`FIG. 1 illustrates intravascular stent 10 which is mounted
`
`onto delivery catheter 11. Stent 10 generally comprises a
`plurality of radially expandable cylindrical elements 12
`disposed generally coaxially and interconnected by mem-
`bers 13 disposed between adjacent cylindrical elements 12.
`Delivery catheter 11 has an expandable portion or balloon 14
`for expanding stent 10 within coronary artery 15 or other
`vessel such as saphenous veins, carotid arteries, arteries, and
`veins. Artery 15, as shown in FIG. 1, has dissected lining 16
`which has occluded a portion of the arterial passageway.
`Delivery catheter 11 onto which stent 10 is mounted is
`essentially the same as a conventional balloon dilatation
`catheter for angioplasty procedures. Balloon 14 may be
`formed of suitable materials such as polyethylene, polyvinyl
`chloride, polyethylene terephthalate and other like poly-
`mers. In order for stent 10 to remain in place on balloon 14
`during delivery to the site of the damage within artery 15,
`stent 10 is compressed onto balloon 14. This compressing
`step is known as crimping.
`An optional retractable protective delivery sleeve 20 may
`be provided to further ensure that stent 10 stays in place on
`balloon 14 of delivery catheter 11 and to prevent abrasion of
`the body lumen by the open surface of stent 10 during
`delivery to the desired arterial location. Other means for
`securing stent 10 onto balloon 14 may also be used, such as
`providing collars or ridges on the ends of the working
`portion, i.e., the cylindrical portion of balloon 14.
`In order to implant stent 10,
`it is first mounted onto
`inflation balloon 14 on the distal extremity of delivery
`catheter 11. Stent 10 is crimped down onto balloon 14 to
`ensure a low profile. The present invention addresses this
`crimping procedure.
`The catheter-stent assembly can be introduced into the
`patient’s vasculature through processes known in the art.
`Briefly, guide wire 18 is disposed across the arterial section
`where an angioplasty or atherectomy has been performed
`requiring a follow-up stenting procedure. In some cases, the
`arterial wall lining may be detached so that guide wire 18 is
`advanced past detached or dissected lining 16 and the
`catheter-stent assembly is advanced over guide wire 18
`within artery 15 until stent 10 is directly under detached
`lining 16. Prior to inflation of balloon 14, delivery sleeve 20
`is retracted to expose stent 10. Depending on the balloon and
`stent assembly, a delivery sleeve may be unnecessary. Bal-
`loon 14 of delivery catheter 11 is then inflated using an
`inflation fluid. Expansion of balloon 14 in turn expands stent
`10 against artery 15. Next, balloon 14 is deflated and
`catheter 11 is withdrawn leaving stent 10 to support the
`damaged arterial section. As mentioned above, in order to
`ensure proper seating of stent 10 on balloon 14, and to
`ensure proper deployment of stent 10 at
`the site of the
`damage within artery 15, the stent crimping procedure is
`important.
`FIG. 2 is a perspective view of a preferred embodiment of
`the present invention stent crimping tool 22. Specifically, the
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`present invention is directed to tool 22 for crimping intra-
`vascular stent 10 onto balloon 14 of delivery catheter 11. In
`a preferred embodiment, stent crimping tool 22 includes
`sheet 24 that is made from a flexible material, such as Mylar.
`Flexible sheet 24 is curved and folded over so that end
`
`portions 26 thereof overlap as shown in the perspective view
`of FIG. 2. As part of the invention, end portions 26 of
`flexible sheet 24 are designed to pass through thin slot 28
`formed in rigid panel 30. Preferably, rigid panel 30 is locked
`or mounted to a stationary work bench, fixture, or the like.
`The mounting hardware has been omitted from FIG. 2 for
`the sake of clarity.
`As seen in FIG. 2, after uncrimped stent 10 is loaded onto
`balloon 14 of delivery catheter 11, the catheter-stent assem-
`bly is placed within cylindrical space 32 formed by curving
`and overlapping flexible sheet 24. End portions 26 are held
`together by optional clamp 34, which is used to apply a
`downward force represented by arrow F. This downward
`force F pulls flexible sheet 24 through thin slot 28 and
`simultaneously collapses cylindrical space 32. Continued
`downward force F on end portion 26 stretches flexible sheet
`24 taut around the catheter-stent assembly. Because of its
`size relative to thin slot 28,
`the catheter-stent assembly
`cannot pass through thin slot 28 while flexible sheet 24 can
`slide therethrough. This is therefore the preferred mecha-
`nism used to crimp stent 10 onto balloon 14.
`Optionally, a rigid mandrel (not shown) may be disposed
`within guide wire lumen 17 of delivery catheter 11 to help
`the structure maintain its shape during the crimping process.
`Thus, as flexible sheet 24 squeezes down on stent 10 to
`crimp it onto balloon 14,
`the rigid mandrel resists the
`downward force and prevents balloon 14 from collapsing
`completely and losing its shape.
`In addition, the present invention crimp stenting tool can
`be adapted for use with an actuator. For example, actuator 36
`is anchored to ground 38 and can be embodied in a spring
`or a pneumatically operated piston within a cylinder. Actua-
`tor 36 can be manually operated, lever operated, pneumati-
`cally operated, or triggered by a similar technology known
`in the art
`in order to generate the downward force F.
`Primarily, actuator 36 would be used as a time saving
`measure for high cyclic rates in a production line for
`example. Moreover, a machine generated downward force
`would be uniform and controlled so that very precise crimp-
`ing of stent 10 can be achieved.
`FIG. 3 provides a front elevational view of the present
`invention stent crimping tool 22. In the instant of time
`shown here, the catheter-stent assembly has been positioned
`within cylindrical space 32 of curved flexible sheet 24
`similar to the depiction in FIG. 2. As best seen in FIG. 3,
`rigid panel 30 is represented in a cross-section to best
`illustrate thin slot 28 with rounded edges 40. Rounded edges
`40 are preferable because as tension is applied to flexible
`sheet 24 to draw the material through thin slot 28, flexible
`sheet 24 assumes a tear drop shape that does not conform
`stent 10 to balloon 14 very well. Rounded edges 40 therefore
`reduce frictional drag on the movement of flexible sheet 24
`through thin slot 28, and further insures a tighter crimp as
`flexible sheet 24 pulls the catheter-stent assembly against
`rounded edges 40.
`Ideally, to maximize the crimp of stent 10 onto balloon 14,
`the radius of curvature of cylindrical space 32 formed by
`flexible sheet 24 should not be less than or greater than but
`exactly the radius of the crimped stent. This demands that at
`the transition between the crimping portion of flexible sheet
`24 and the portion thereof that is pulled through thin slot 28,
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`flexible sheet 24 is plastically deformed. Indeed, flexible
`sheet 24 undergoes a significant amount of stress at the point
`where it slides into thin slot 28 because, by design, it is
`expected to undergo a 90 degree turn. This is illustrated in
`the front elevational view of FIG. 4A. If flexible sheet 24
`
`were preformed (i.e., prestressed) as seen in the front
`elevational view of FIG. 4B, it is possible to achieve a near
`perfect circle surrounding the catheter-stent assembly result-
`ing in a symmetrical crimp as shown in FIG. 4A. To be sure,
`FIG. 4C provides a front elevational view of a preformed or
`prestressed flexible sheet 24 which is shown being pulled
`through thin slot 28 of rigid panel 30. Because the process
`is not complete and flexible sheet 24 has not been pulled
`through thin slot 28 sufficiently to remove slack, 90 degree
`turn kinks 42 do not coincide with rounded edges 40.
`FIGS. 5—8 depict an alternative embodiment of the
`present invention. FIGS. 5A and 5B provide a front eleva-
`tional and a side elevational view of an alternative embodi-
`
`ment of the present invention stent crimping tool 44. In this
`preferred embodiment, stent crimping tool 44 includes
`mount 46 operating in conjunction with flexible sheet 48. In
`the front elevational view of FIG. 5A, the present invention
`is shown in connection with an uncrimped catheter-stent
`assembly placed upon mount 46. To insure stability, mount
`46 preferably includes a grooved surface to help center the
`catheter-stent assembly thereon. In particular, groove 50
`preferably has a radius that approximates the catheter-stent
`assembly.
`FIG. 5B is a side elevational view wherein flexible sheet
`
`48 has been omitted to expose placement of the catheter-
`stent assembly on mount 46. In this view, it can be seen that
`stent 10 has already been loaded onto balloon 14 of catheter
`11. In the preferred embodiment, mount 46 generally has a
`lengthwise dimension approximating the length of stent 10.
`Mount 46 is situated on a work surface so that it is stable and
`
`immobile during the crimping process.
`Mount 46 can be fashioned from a rigid material known
`in the art. Importantly, mount 46 has steeply sloped side
`walls 52 to minimize frictional drag and interference with
`movement of flexible sheet 48 during the crimping process.
`FIGS. 6—8 illustrate use of the present invention stent
`crimping tool 44. FIG. 6 provides a front elevational view of
`stent crimping tool 44 when a downward force is exerted at
`end portions 54 of flexible sheet 48. The downward force is
`represented by arrows labeled F. This force places flexible
`sheet 48 in tension and compresses the catheter-stent assem-
`bly between flexible sheet 48 and mount 46. As seen in the
`previous exemplary embodiment, the present invention may
`be used with an optional rigid mandrel that is inserted into
`a guide wire lumen of balloon 14 to provide internal support
`during the crimping process.
`In FIG. 7, the downward force and tension in flexible
`sheet 48 have been removed;
`this state is depicted with
`flexible sheet 48 having slack. In this state, it is possible to
`rotate the catheter-stent assembly to reorient the parts before
`undergoing the next crimping step. To this end, FIG. 8 shows
`downward force F being reapplied to end portions 54 of
`flexible sheet 48 to again resume compressing the catheter-
`stent assembly between flexible sheet 48 and mount 46. The
`steps shown in FIGS. 6—8 are repeated until stent 10 is firmly
`crimped onto balloon 14.
`As seen with the previous embodiment of the present
`invention,
`it
`is possible to mechanize or automate this
`process by use of actuators discussed earlier. Once the
`process is complete, the downward force F is removed to
`remove the tension from flexible sheet 48. The crimped
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`catheter-stent assembly can then be removed from the
`crimping tool 44.
`In the preferred embodiment, groove 50 has a cradle or
`semicircular cross-sectional shape to support the catheter-
`stent assembly during the crimping process. Other cross-
`sectional shapes are contemplated, and may be useful for
`various purposes or to accommodate varying stent profiles.
`Groove 50 may be optionally coated, covered, or include
`other surface features. Such surface features include
`
`optional ribs, contours, bumps, indentations, and the like to
`accommodate the features of the catheter-stent assembly, to
`provide support and stability, or to achieve frictional contact
`with the catheter-stent assembly to minimize twisting.
`Mount 46 is preferably held inside another enclosure (not
`shown) for correct alignment of stent 10 and balloon 14.
`Again, as mentioned earlier, flexible sheet 48 is preferably
`made from Mylar or the like and should drape over side
`walls 52 of mount 46. Correct sizing between stent 10 and
`flexible sheet 48 insures a perfect fit of stent 10 over balloon
`14. This