5,931,851
`[11] Patent Number:
`[19]
`Unlted States Patent
`
`Morales
`[45] Date of Patent:
`Aug. 3, 1999
`
`U5005931851A
`
`[54] METHOD AND APPARATUS FOR RUBBER-
`EgggTCRIMPING TOOL WITH PREMOUNT
`
`FOREIGN PATENT DOCUMENTS
`WO 98/14120
`4/1998 WIPO .
`WO 98/19633
`5/1998 WIPO .
`
`[75]
`
`Inventor: Stephen A. Morales, Mountain View,
`Calif.
`
`OTHER PUBLICATIONS
`
`[73] Assignee: Advanced Cardiovascular Systems,
`Inc., Santa Clara, Calif.
`
`[21] Appl. No.: 09/063,587
`
`APF- 21, 1998
`Flledi
`[22]
`Int. Cl.5 .................................................... A61M 29/00
`[51]
`[52] us. Cl.
`............................. 606/194 606/198' 29/235
`[58] Field of Search ........... ............. ............. 606/198, 194,
`606/192’ 108’ 623/1’ 604/96’ 29/282’ 234’
`235
`
`[56]
`
`References Cited
`US. PATENT DOCUMENTS
`
`696,289
`4,468,224
`4,576,142
`4,644,936
`4,681,092
`4,697,573
`49017707
`4,907,336
`5,132,066
`5,133,732
`5,183,085
`5,189,786
`5,437,083
`5,546,646
`5,626,604
`5,630,830
`596539691
`5,738,674
`
`5,746,764
`5,783,227
`5,785,715
`5,836,952
`
`.
`
`3/1902 Williams .
`8/1984 Enzmann et a1.
`3/1986 schiff .
`2/1987 Schiff .
`7/1987 Cho et a1.
`10/1987 Schiff .
`2/1990 SChlfl -
`3/1990 Gianturco .
`7/1992 Charlesworth et a1.
`7/1992 Wiktor.
`2/1993 Timmermans .
`3/1993 Ishikawa et a1.
`8/1995 Williams et a].
`8/1996 Williams et a1.
`5/1997 Cottone, Jr.
`.
`5/1997 Verbeek .
`8/1997 RuPP 6t a1~ -
`4/1998 Williams et a1.
`
`.
`
`.
`.
`.
`
`.
`
`.
`
`5/1998 Green et a1.
`7/1998 Dunham .
`7/1998 Schatz .
`11/1998 Davis et a1.
`
`.
`
`US. Patent Application Serial No. 08/795,335 filed Feb. 4,
`1997.
`US. Patent Application Serial No. 08/837,771 filed Apr. 22,
`1997.
`
`US. Patent Application Serial No. 08/089,936 filed Jul. 15,
`1997.
`
`US. Patent Application Serial No. 08/962,632 filed Nov. 3,
`1997~
`The eXTmordiWy 519% CR Bard BIOChure (Undated)
`Primary Examiner Michael Buiz
`Assistant Examiner—Julian W. Woo
`Attorney, Agent, or Firm—Fulwider Patton Lee & Utecht,
`LLP
`[57]
`
`ABSTRACT
`
`A stent crimping tool for firmly and uniformly crimping a
`stent onto a balloon catheter is constructed from a hous1ng
`containing a silicone tube wherein the silicone tube is
`compressed by a thumb screw that is threaded into one end
`of the housing. The silicone tube has a passage containing a
`premounted uncrimped stent. The balloon catheter is
`inserted through the thumb screw and aligned with the stent
`inside the tube. Both ends of the silicone tubing are tapered
`and engage a tapered internal end inside the housing and a
`tapered recess inside the thumb screw. Advancing the thumb
`screw decreases the length of the s111cone tubing and
`reshapes it so that
`the inside diameter of the passage
`decreases thereby crimping the stent onto the balloon. In an
`alternative embodiment, the opposite end of the housing is
`fitted with a second thumb screw. Further, the silicone tubing
`can be separated into two discrete segments by an annular
`washer located at a mid-point along the length of the silicone
`tube
`'
`
`............................ 606/108
`
`20 Claims, 3 Drawing Sheets
`
`24
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`
`
`
`
`
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`74
`
`28
`
`30
`
`Edwards Lifesciences v.
`
`Boston Scientific
`
`US. Patent No. 6,915,560
`IPR2017-00444 EX. 2043
`
`Page 1 of 9
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`Page 1 of 9
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`

`

`US. Patent
`
`Aug. 3, 1999
`
`Sheet 1 0f 3
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`5,931,851
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`Page 2 of 9
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`U.S. Patent
`
`Aug. 3, 1999
`
`Sheet 2 of 3
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`5,931,851
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`Page 3 of 9
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`U.S. Patent
`
`Aug. 3, 1999
`
`5,931,851
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`Page 4 of 9
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`

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`5,931,851
`
`1
`METHOD AND APPARATUS FOR RUBBER-
`TUBE CRIMPING TOOL WITH PREMOUNT
`STENT
`
`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
`
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`2
`vasculature, including thrombosis. Therefore, it is important
`to ensure the proper crimping of a stent onto a catheter in a
`uniform and reliable manner.
`
`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 is 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 tubular member and
`bladder are constructed 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 crimping 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
`from a rigid, tubular body with a ball at one end connected
`to a plurality of long, thin strips passing through the 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 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.
`
`While the prior art devices are suitable for crimping stents
`onto balloon catheters, they suffer from problems such as
`non-uniform crimping forces,
`resulting in non-uniform
`crimps. Consequently, they are unsuitable for use by phy-
`sicians in a cath lab who desire to crimp 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
`
`Page 5 of 9
`
`Page 5 of 9
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`

`

`5,931,851
`
`3
`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
`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.
`
`The present invention stent crimping tool is based on the
`mechanics of a rotational hemostatic valve (RHV). That is,
`the design attempts to concentrically crimp a stent onto a
`balloon catheter by relying on the action of three major
`components: a thick-walled resilient tube, a rigid but trans-
`parent housing, and a thumb screw.
`the present
`In particular,
`in a preferred embodiment,
`invention tool comprises a thumb screw having a cylindrical
`shape with a first end and a second end, wherein the second
`end includes external threads, and wherein the second end
`includes a recess having a taper leading to an opening in the
`first end; a housing having an internal cylindrical space with
`first and second ends, wherein the first end of the space is
`open and includes threads, and wherein the second end of
`the space includes a taper leading to an opening; a resilient
`tube having a passage therethrough, the tube having tapered
`ends, and wherein the tube is disposed within the cylindrical
`space of the housing.
`the tube is made from
`In the preferred embodiment,
`silicone, and the housing can be injection molded from a
`transparent but rigid thermoplastic material. It may also be
`machined out of acrylic or lexan. A transparent housing
`permits the physician to visually align the stent and catheter
`assembly with the tube just prior to undergoing the crimping
`step.
`The present invention tool should ideally be operated by
`a physician in a cath lab to crimp a stent onto a balloon
`catheter. An uncrimped stent is positioned inside the resilient
`tube such that the ends are equidistant from the ends. When
`the tool is to be used, the physician advances the balloon
`catheter through the opening in the first end of the thumb
`screw leading into the passage of the tube. The physician
`then uses the balloon markers and the ends of the stent to
`
`visually aligned their relative positions. Holding the balloon
`catheter in place,
`the physician next tightens the thumb
`screw to the extent of its travel. This further advances and
`
`compresses the thumb screw into the tube holding the stent
`and balloon. The compression causes the resilient tube to
`decrease in length, and because of surface tension and its
`containment by the housing, the volume of the tube is held
`constant. Hence, the decrease in length results is a propor-
`tionate increase in wall thickness of the tube and conversely,
`a proportionate decrease in the diameter of the passage
`containing the stent and balloon catheter. The decrease in the
`diameter of the passage collapses the space and compresses
`the stent on to the balloon catheter.
`
`At this point, the stent should be securely crimped on to
`the balloon. The thumb screw can be counter-rotated to
`
`relieve pressure on the crimped stent and balloon. The
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`balloon with the crimped stent can then be withdrawn from
`or advanced through the tool. The crimped stent is now
`ready for implantation in a patient.
`An optional mandrel can be inserted inside the balloon
`catheter to prevent excessive deformation of the stent during
`the crimping step. In an alternative embodiment, the tube
`can be made into at least two lengthwise-discrete segments
`separated by at
`least one annular washer. The smaller
`segments of the tube would offer less surface displacement
`during the crimping step. Yet another alternative embodi-
`ment includes at least two semicircular resilient tube halves.
`
`Use of the thumb screw permits the physician to precisely
`control the amount of crimping force transmitted to the stent.
`With precise control of applied crimping forces, the present
`invention tool is capable of homogeneously crimping a stent
`onto a balloon catheter.
`
`Such a crimping tool is highly useful to cardiologists, for
`example. Such physicians are often concerned with proper
`deployment of the stent within the patient that it 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 performed fairly efficiently
`and quickly.
`Another advantage of this particular invention is that it is
`balloon friendly.
`In that regard,
`the compliance of the
`resilient
`tube can be varied so that
`the balloon is not
`
`damaged by the crimping of the stent onto the catheter.
`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 cross-sectional view of a preferred embodi-
`ment of the present invention, showing a stent end balloon
`catheter positioned within a resilient
`tube held inside a
`housing with a thumb screw.
`FIGS. 3A and 3B are a plan view and a side elevational
`view, respectively, of the present invention housing.
`FIGS. 4A and 4B are a plan view and a side elevational
`view, respectively, of a thumb screw.
`FIGS. 5A and 5B are a plan view and a side elevational
`view, respectively, of a resilient tube.
`FIG. 6 is a cross-sectional view of an alternative embodi-
`
`ment of the present invention tool employing two thumb
`screws.
`
`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 coaxially and interconnected by members 13 dis-
`posed 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
`
`Page 6 of 9
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`Page 6 of 9
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`

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`5,931,851
`
`5
`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.
`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.
`The present invention stent crimping tool is based on the
`mechanics of a rotational hemostatic valve (RHV). That is,
`the design attempts to concentrically crimp a stent onto a
`balloon catheter by relying on the action of three major
`components: a thick-walled resilient tube, a rigid but trans-
`parent housing, and a thumb screw.
`FIG. 2 provides a sectional view of a preferred embodi-
`ment of the present invention stent crimping tool 22. Stent
`crimping tool 22 includes thumb screw 24, housing 26, and
`resilient tube 28. As seen in this figure, stent 10 has already
`been inserted into a lumen or passage 30 of resilient tube 28.
`Also depicted in the drawing, balloon 14 of catheter 11 has
`been aligned with stent 10 and is ready for the crimping step.
`Although not specifically shown, stent 10 should preferably
`be positioned equidistant from both ends of tube 28. FIGS.
`3A and 3B provide a top plan view and a side elevational
`view of a preferred embodiment of the present invention
`housing 26. Housing 26 as shown here has a cylindrical
`shape, but other external shapes for housing 26 are contem-
`plated. Housing 26 has internal cylindrical space 42 leading
`to opening 44.
`In the exemplary embodiment,
`internal
`cylindrical space 42 includes a 60 degree taper 46 at one end.
`Housing 26 should preferably be made from a transparent
`or at least translucent material to permit the physician to
`visually align the balloon catheter with the premounted stent
`inside the present invention tool. Housing 26 should thus be
`
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`injection molded from a clear or transparent thermoplastic
`material. It may also be machined out of clear acrylic or
`lexan. In an alternative embodiment, the housing may be
`created from materials such as lead, which offer shielding
`from a radioactive stent. FIGS. 4A and 4B provide a top plan
`view and a side elevational view of a preferred embodiment
`thumb screw 24 having external screw threads 32. Thumb
`screw 24 preferably has a two-tier, dual cylindrical shape for
`easier gripping by the physician. More precisely,
`large
`diameter portion 36 may have an optional
`textured or
`contoured outside diameter (not shown) to improve friction
`and ergonomics for the physician to apply a torque to
`operate the tool. Also as seen in FIGS. 4A and 4B, thumb
`screw 24 includes recess 38 leading to opening 40.
`Preferably, recess 38 has a 60 degree taper.
`FIGS. 5A and 5B provide a top plan view and a side
`elevational view of a preferred embodiment of resilient tube
`28. In the preferred embodiment, resilient tube 28 is made
`from silicone; other resilient materials known in the art are
`contemplated including rubber,
`foam, gels, etc.
`Furthermore, the opposite ends of tube 28 are tapered 48 at
`approximately 60 degrees. The tapered ends of resilient tube
`28 also help in concentrating material flow to reshape tube
`28 during the crimping step. Passage 30 extends through a
`length of tube 28. Passage 30 preferably has a diameter that
`approximates an outside diameter of an uncrimped stent.
`All three major components depicted in FIGS. 3, 4, and 5
`are assembled as shown in FIG. 2. Assembled, an exemplary
`embodiment of the present invention tool 22 is no larger than
`the existing packaging for other hand crimped stents; that is:
`2 inches by 2 inches by 0.75 inch. Thumb screw 24 as
`mentioned above has a two-part cylinder with a maximum
`outside diameter of 0.75 inch and a secondary outside
`diameter of 0.25 inch. The inside diameter of opening 40 is
`a constant 0.1 inch. As mentioned earlier, to provide better
`gripping, the larger outside diameter of portion 36 may be
`patterned with indentations approximately 0.05 inch deep. In
`total, the length of thumb screw 24 is approximately 0.4
`inch.
`
`Tube 28, which is in contact with stent 10 and balloon 14,
`is preferably 0.25 inch in its outside diameter with a 0.1 inch
`inside diameter defining passage 30. The total length of
`resilient tube 28 is approximately one inch.
`Housing 26 is preferably a tube cut to fit over the outside
`diameter of resilient tube 28. It is a clear plastic with tapped
`threads 34 at one end to match external threads 32 of thumb
`
`screw 24. The wall thickness of housing 26 is preferably
`between 0.125 inch and 0.25 inch. As mentioned above,
`inner cylindrical space 42 of housing 26 at one end is tapered
`at 60 degrees to the horizontal, and in that same end, a 0.1
`inch diameter opening 44 is preferably made concentric with
`the center of the housing inside diameter and outside diam-
`eter.
`
`tube 28 is placed inside internal cylindrical
`Resilient
`space 42 of housing 26. Thumb screw 24 is inserted into
`open end 48 of housing 26 and screw threads 32 are
`advanced along internal threads 34 of housing 26.
`Stent 10 should already be positioned within resilient tube
`28 from the cath lab or manufacturer. Tube 28 serves as a
`
`holding place for stent 10. When the physician is ready to
`use the tool, he or she must insert
`the balloon catheter
`through the distal end of the tool; i.e., through opening 40 of
`thumb screw 24. While watching through transparent hous-
`ing 26, the physician then uses a balloon marker (not shown)
`to help align balloon 14 with the ends of stent 10. Holding
`catheter 11 in place, the physician then tightens thumb screw
`24 to the extent of its travel.
`
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`Page 7 of 9
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`5,931,851
`
`7
`The length of resilient tube 28 begins to decrease with the
`incremental advancement of thumb screw 24. Due to surface
`tension of resilient
`tube 28 and its containment within
`
`internal cylindrical space 42 of housing 26, the volume of
`resilient tube 28 is held constant. So as its length dimension
`decreases, material
`is displaced reshaping the walls to
`become thicker, which in turn decreases the inside diameter
`of resilient tube 28. In doing so, the inside walls of tube 28
`compress stent 10 onto balloon 14. At this point in the
`procedure, stent 10 should be securely crimped on to balloon
`14.
`
`thumb screw 24 can be rotated in the opposite
`Next,
`direction to relieve the pressure on resilient tube 28 and in
`turn on the stent-balloon catheter assembly. The crimped
`stent-balloon catheter assembly can be withdrawn from the
`tool 22, or the assembly can be passed through opening 44
`and advanced over guide wire 18 into the patient.
`Of course, the advancement and retraction of thumb screw
`24 can be repeated as necessary to ensure a consistent crimp.
`Also, an optional mandrel can be installed within catheter 11
`to prevent over compression of stent 10 on balloon 14.
`Moreover, between each crimp end release cycle,
`it
`is
`possible to rotate the stent-balloon catheter assembly to
`ensure an even crimp.
`FIG. 6 provides a cross-sectional view of an alternative
`embodiment tool 50. The theory of operation is similar to the
`previous exemplary embodiment with the addition of a
`second thumb screw. As seen in FIG. 6, alternative embodi-
`ment tool 50 includes thumb screws 52, 54 having respective
`grippable large diameter portions 56, 58. As in the previous
`embodiment, thumb screws 52, 54 have respective openings
`60, 62 leading to tapered recesses 64, 66. As in the previous
`embodiment, thumb screws 52, 54 are threaded to engage
`the internal threads of housing 70.
`Housing 70 has an internal cylindrical space 72 that has
`a constant diameter from end to end, with internal threads at
`each end. Inside internal cylindrical space 72 is resilient
`tubing 74 with passage 76 containing stent 10 already loaded
`therein. As depicted in FIG. 6, balloon 14 of delivery
`catheter 11 has been aligned with stent 10 just prior to the
`crimping step.
`tubing 74 is
`In this alternative embodiment, resilient
`In between
`broken into two discrete segments 78, 80.
`discrete segments 78, 80 is an annular washer 82. Washer 82
`serves as a partition separating resilient tube 74 into its two
`discrete parts. One benefit is that separate discrete segments
`78, 80 offer a smaller surface displacement during the
`crimping process. This would obviate undue friction buildup
`from movement of the resilient material making up resilient
`tube 74 as it is compressed length-wise. Yet another alter-
`native embodiment of resilient tubing 74 includes at least
`two semicircular resilient tube halves.
`
`Furthermore, operation of tool 50 is achieved by twisting
`thumb screws 52 and 54 alternately or simultaneously. The
`use of a second thumb screw and segmenting resilient tube
`74 are various methods of minimizing friction on stent 10.
`Other methods of minimizing friction on the stent during the
`crimping process include: polishing the walls of passage 76,
`coating those walls, adding a lining to passage 76, or treating
`the walls through a process known in the art, etc. The goal
`is to minimize damage or harm to stent 10 during the
`crimping step.
`The alternative embodiment design shown in FIG. 6 is
`also useful for stents having a larger length or for stents used
`in a multi-link system, which are very fragile. Having two
`thumb screws 52, 54 controls the amount of material dis-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`placed within each discrete segment 78, 80, and distributes
`the pressure exerted by discrete segments 78, 80 to ensure a
`homogeneous crimping force throughout the length of the
`stent.
`
`An advantage of the present invention is that it is balloon
`friendly, because the compliance of resilient tube 28, 74 can
`be varied so that the balloon is not damaged by crimping the
`stent onto the catheter. Further, the present invention works
`best when the difference between the stent inside diameter
`and the balloon outside diameter is minimal, approximately
`0.020 to 0.015 inch. Also from empirical experience, the
`present
`invention crimping tool may tend to slightly
`lengthen the stent during the crimping process.
`The present invention tool is preferably sterilized and
`intended to be used in a cath lab by a trained technician or
`cardiologist. As will be appreciated by those skilled in the
`art, the present invention crimping tool is designed both for
`single use applications in a cath lab by a physician, or for
`multiple use applications in a sterile environment in a high
`volume manufacturing facility. In such a manufacturing
`facility where sterile conditions exist, the present invention
`stent crimping tool can be used repeatedly to crimp stents
`onto balloons until the mechanism wears out. Thus, repeated
`uses of the present
`invention are contemplated for
`controlled, sterile environments, as are single use applica-
`tions when operated by cath lab personnel.
`Furthermore, the present invention crimping tool can be
`used with any stent
`that
`is released without a delivery
`system. The crimping tool may also be sold alone, because
`its design is robust enough to undergo many uses.
`Other modifications can be made to the present invention
`without departing from the scope thereof. The specific
`dimensions, procedural steps, and materials of construction
`are provided as examples, and substitutes are readily con-
`templated which do not depart from the invention.
`What is claimed is:
`1. A tool for crimping a stent on to a balloon catheter,
`comprising:
`a thumb screw having a cylindrical shape with a first end
`and a second end, wherein the second end includes first
`threads, and wherein the second end includes a recess
`leading to an opening in the first end;
`a housing having an internal cylindrical space with first
`and second ends, wherein the first end is open and
`includes second threads;
`a resilient tube having a passage therethrough, wherein
`the tube is disposed within the cylindrical space of the
`housing;
`whereby the stent is loaded inside the passage and the
`balloon catheter is inserted therein, and the thumb
`screw is threaded into the first end of the housing; and
`whereby turning the thumb screw advances the thumb
`screw, compressing the resilient tube, and crimping the
`stent on to the balloon catheter.
`
`2. The stent crimping tool according to claim 1, wherein
`the internal cylindrical space of the housing includes a
`tapered second end.
`3. The stent crimping tool according to claim 1, wherein
`the recess of the thumb screw includes a taper.
`4. The stent crimping tool according to claim 1, wherein
`the tube has tapered ends.
`5. The stent crimping tool according to claim 1, wherein
`t