[19]
`United States Patent
`6,009,614
`[11] Patent Number:
`[45] Date of Patent: Jan. 4, 2000
`Morales
`
`
`
`USOO6009614A
`
`[54]
`
`STENT CRIMPING TOOL AND METHOD OF
`USE
`
`US. application No. 08/962,632 filed Nov. 3, 1997.
`
`The eXTraordinary Stent, C.R. Bard Brochure (Undated).
`
`[75]
`
`Inventor: Stephen A. Morales, Mountain View,
`Calif.
`
`[73] Assignee: Advanced Cardiovascular Systems,
`Inc., Santa Clara, Calif.
`
`[21] Appl. No.: 09/063,905
`
`[22]
`
`Filed:
`
`Apr. 21, 1998
`
`[51]
`
`Int. Cl.7 ........................... A61M 29/00; B23P 11/00;
`B23P 19/02
`
`................................. 29/516; 29/270; 29/282;
`[52] US. Cl.
`29/407.08; 29/235; 606/1; 606/108; 606/198;
`623/1
`
`[58] Field of Search ................................. 29/516, 407.08,
`29/282, 280, 715, 423, 517, 234, 235, 283,
`269, 270, 237; 606/1, 108, 198; 623/1;
`72/402
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`696,289
`3,568,495
`4,043,172
`4,379,397
`4,468,224
`
`3/1902 Williams.
`3/1971 Duffield et a1.
`8/1977 Schmitton.
`4/1983 Langr.
`8/1984 Enzmann et a1.
`
`.
`
`.
`
`(List continued on next page.)
`FOREIGN PATENT DOCUMENTS
`
`159065
`WO 98/14120
`WO 98/19633
`
`2/1921 United Kingdom .
`4/1998 WIPO .
`5/1998 WIPO .
`
`OTHER PUBLICATIONS
`
`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.
`
`22
`
`40
`
`Primary Examiner—S. Thomas Hughes
`Assistant Examiner—John Preta
`
`Attorney, Agent, or Firm—Fulwider Patton Lee & Utecht,
`LLP
`
`[57]
`
`ABSTRACT
`
`A tool and method for enabling substantially uniform and
`tight crimping of an intravascular stent onto a balloon
`catheter assembly. The crimping tool is constructed from a
`rigid cylindrical chassis sealed at both ends, having a hollow
`interior containing an elastic tube that partially occupies the
`interior. Apiston abuts the elastic tube and forms a hermeti-
`cally sealed chamber behind the piston and a closed end
`ofthe chassis. A port connected to an indeflator and posi-
`tioned on the chassis provides an inlet into and out of the
`chamber. A stent that is loaded onto the balloon portion of
`the catheter is inserted through a central opening in another
`end of the chassis to position the stent catheter assembly
`within the axial space inside the elastic tube. The indeflator
`injects a fluid into the chamber thereby increasing its pres-
`sure which in turn displaces the piston into the elastic tube
`compressing the tube longitudinally. The elastic tube
`decreases in length and expands in thickness radially to
`crimp the stent onto the balloon catheter. Once pressure is
`relieved from the chamber, the piston moves away from the
`elastic tube, which restores to its original shape. The
`crimped stent and catheter can then be withdrawn. The
`piston may be driven by a power screw in place of fluid
`pressure.
`
`28 Claims, 3 Drawing Sheets
`
`I4
`
`30
`
`/l
`
`
`
`--»§_53—I§ii'
`
`
`
`
`
`
`
`IPR2017-00444 EX. 2048 Page 1 of11
`
`mm
`
`Edwards Lifesciences v. Boston Scientific
`
`US. Patent N0. 6,915,560
`
`Page 1 of 11
`
`

`

`6,009,614
`Page 2
`
`US. PATENT DOCUMENTS
`
`4,576,142
`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
`
`3/1986
`2/1987
`7/1987
`10/1987
`2/1990
`3/1990
`7/1992
`7/1992
`2/1993
`3/1993
`8/1995
`8/1996
`
`.
`
`Schiff .
`Schiff .
`Cho et al.
`Schiff .
`Schiff .
`Gianturco .
`Charlesworth et al.
`Wiktor .
`Timmermans .
`Ishikawa et al.
`Williams et al.
`Williams et al.
`
`.
`.
`.
`
`.
`
`5,626,604
`5,630,830
`5,653,691
`5,695,515
`5,738,674
`5,746,764
`5,783,227
`5,785,715
`5,795,289
`5,810,838
`5,836,952
`5,860,966
`5,893,852
`
`5/1997
`5/1997
`8/1997
`12/1997
`4/1998
`5/1998
`7/1998
`7/1998
`8/1998
`9/1998
`11/1998
`1/1999
`4/1999
`
`Cottone, Jr.
`Verbeek .
`
`.
`
`.
`
`Rupp et al.
`Orejola .
`Williams et al.
`Green et al.
`.
`Dunham .
`Schatz .
`
`.
`
`Wyttenbach .
`Solar .
`DaVis et al.
`Tower .
`Morales .
`
`.
`
`PageZof11
`
`Page 2 of 11
`
`

`

`US. Patent
`
`Jan. 4,2000
`
`Sheet 1 0f3
`
`6,009,614
`
`F/G.
`
`/
`
`
` --’I
`
`.
`i? J?[ _§:?—g'e:.mss————ud'lllllllllllll
`
`£355? .I
`
`
`
`
`
`PageBof11
`
`Page 3 of 11
`
`

`

`US. Patent
`
`Jan. 4,2000
`
`Sheet 2 0f3
`
`6,009,614
`
`40
`
`I4
`
`30
`
`
`[/AWIIII/IIIV‘III‘VIAIAE
`[-0000M!i\\\\\\\\w\\V
`\\\\\\
`____\\\\\\\\\‘;\\\\‘_72W
`
`
`Ill/11W” I
`1/1)
`
`
`($331;
`
`28
`
`34
`
`I4
`
`30
`
`
`
`”WWI/”0mg
`\/\/\/\/\/\/\/\~i\\\\\
`\\“mi
`
`
`
`
`n -\\\‘
`,%
`[III/AIIIIIVIIVIIAQI
`‘—
`
`I I
`
`II:
`
`
`
`
`24
`
`l0
`
`Page4of11
`
`Page 4 of 11
`
`

`

`US. Patent
`
`Jan. 4, 2000
`
`Sheet 3 0f 3
`
`6,009,614
`
`06E
`
`
`
`m§§s§§k
`
`mm
`
`vm
`
`WEEmm.Km
`.\va
`
`Om
`
`\
`
`mm
`
`N\\\\\\\\\§
`
`
`
`mummu.
`
`mkUK«Nwe:
`
`PageSof11
`
`Page 5 of 11
`
`
`
`
`
`

`

`6,009,614
`
`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 ofthe guiding catheter into the patient’s coro-
`nary 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, nonuniform 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
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`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 resulting in potentially short and long term damage to
`the stent, 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 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
`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
`
`The present invention is directed to a tool operated by a
`pressurized fluid source such as an indeflator for crimping an
`intravascular stent onto a balloon catheter. In a preferred
`embodiment, the present invention tool comprises a rigid
`cylindrical shaped chassis having a hollow interior with a
`
`Page60f11
`
`Page 6 of 11
`
`

`

`6,009,614
`
`3
`closed back end leading to an open front end, an end cap
`enclosing the open front end, the end cap including a central
`opening. Inside the chassis is a cylindrical shaped elastic
`tube disposed adjacent to the front end and having a length
`less than a length of the hollow interior to define a chamber
`adjacent to the back end of the chassis. The invention further
`comprises a piston that
`is slidably disposed within the
`chamber, and a port in communication with the chamber
`disposed between the back end of the chassis and the piston,
`wherein a flow through the port from the pressurized fluid
`source forces the piston into and axially compresses the
`elastic tube. In this manner, the stent is crimped onto the
`balloon catheter.
`
`More precisely, after the stent is loaded onto the catheter
`and inserted through the central opening into the axial space
`within the elastic tube, the tube is compressed axially. Under
`compression the elastic tube encounters surface tension and
`outside containment by the chassis which force the tube to
`maintain a constant volume. Moreover, the tube by its elastic
`nature will attempt to maintain constant volume. To main-
`tain that constant volume while decreasing its length, the
`tube displaces material radially inward into the open axial
`space containing the stent-catheter assembly. This changes
`the form of the elastic tube cross-section to a shorter and
`
`squatter configuration. The elastic tube thus converts the
`axial displacement of material into a radial displacement of
`material. Accordingly,
`the diameter ofthe axial space
`decreases steadily eventually compressing the stent onto the
`balloon catheter by a factor of Al/lO(AO), where 10 is the
`initial length, A0 is the initial cross-sectional area.
`The present invention tool is operated under fluid pres-
`sure. In a preferred embodiment, the fluid pressure is gen-
`erated by an indeflator wherein a fluid or gas is injected into
`the chamber to displace the piston into the elastic tube. In the
`preferred embodiment,
`the elastic tube is made from a
`pliable rubber.
`Because it is compressed by the concentric expansion of
`the tube while held inside the axial space,
`the stent
`is
`uniformly and evenly crimped onto the balloon catheter.
`Once the present invention tool has been operated up to a
`predetermined pressure,
`the pressure can be released to
`depressurize the chamber thereby removing the axial force
`on the elastic tube. Once the piston and chamber return to
`atmospheric pressure, the balloon catheter with the crimped
`stent can be withdrawn from the tool.
`
`In an alternative embodiment, the present invention tool
`may use a mechanical drive source instead of the hydraulic
`drive source. In this embodiment, the piston is driven by a
`power screw that is threaded to the chassis. The power screw
`can be turned manually or by an electric motor. Rotation of
`the power screw drives the piston into the elastic tube to
`crimp the stent. Then counter-rotation of the power screw
`relieves the pressure on the piston to release the crimped
`stent.
`
`An advantage of the present invention is that the elasto-
`meric tube compresses somewhat for various types of cath-
`eters. The present invention is thus versatile and addresses
`the physician’s desire to use many different catheter con-
`figurations for one style of stent.
`In alternative embodiments of the present invention (not
`shown), the elastomeric tube can have various geometries.
`For example, the elastomeric tube can be fabricated to have
`a star-shaped cross-section, or it can be fashioned to have
`beveled ends. Rigid plastic fillet
`inserts can be placed
`adjacent
`the elastomeric tube within the chassis at
`the
`opposite ends to concentrate stress. The durometer hardness
`
`4
`of the elastomeric tube can also be changed depending on
`the mechanical properties and design of the various stents to
`be crimped. The present invention further contemplates an
`elastomeric tube that can apply circumferential pressure on
`the stent, perhaps with use of bands or rings disposed along
`the circumference of the tube.
`
`Therefore, the present invention crimping tool is highly
`versatile. It is useful to cardiologists and such physicians
`who are constantly concerned with proper deployment of the
`stent within the patient. With a consistently and reliably
`crimped stent as achieved by the present invention, proper
`deployment is possible. The present invention tool is further
`a time saver in that the stent crimping procedure can be
`performed fairly efficiently and quickly.
`In addition, precise control of the pressure inside the
`chamber translates to precise control of the amount of
`compression exerted by the elastic tube on the stent.
`Consequently, the uniformity and degree of crimping of the
`stent can be controlled. These and other advantages of the
`present invention will become apparent from the following
`detailed description thereof when taken in conjunction with
`the accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an elevational view, partially in section, depict-
`ing a stent that has been crimped onto a delivery catheter and
`disposed within a damaged vessel.
`FIG. 2 is a side elevational sectional view of a preferred
`embodiment of the present invention stent crimping tool.
`FIG. 3 is a side elevational sectional view ofthe present
`invention during operation of the tool when the stent is being
`crimped onto a balloon catheter.
`FIG. 4 is a partial cut-away, perspective view of a
`preferred embodiment of the present invention stent crimp-
`ing tool.
`FIG. 5 is a side elevational sectional view of an alternative
`
`embodiment of the present invention, which uses a power
`screw to drive the piston into the tube.
`FIG. 6 is a cross-sectional end view taken along line 6—6
`of FIG. 5 to show longitudinal striations within the elastic
`tube.
`FIGS. 7A and 7B are side elevational views in cross-
`
`section of alternative embodiments of the elastic tube having
`varying diameters.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`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 artery 15 or other vessel.
`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, polyeth-
`ylene terephthalate, polyvinyl chloride, 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.
`
`55
`
`60
`
`65
`
`Page70f11
`
`Page 7 of 11
`
`

`

`6,009,614
`
`5
`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 ofthe 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 damaged
`arterial section with the 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. Balloon 14 of delivery
`catheter 11 is then inflated using an inflation fluid. Expan-
`sion 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 highly critical.
`FIG. 2 provides a side elevational sectional view of a
`preferred embodiment of the present invention stent crimp-
`ing tool 22.
`In the preferred embodiment shown, stent
`crimping tool 22 is constructed from cylindrical shape
`chassis 24 having open end 26 and closed end 28. Open end
`26 is sealed closed with optional end cap 30 that is bonded
`to open end 26 using adhesive 32 of a type known in the art.
`Within cylindrical shape chassis 24 is a hollow interior
`that contains a resilient or pliant elastic tube 34 that is
`preferably coaxially disposed within chassis 24. Notably, in
`the exemplary embodiment, elastic tube 34 has a length that
`is shorter than the interior of chassis 24. Because of this
`
`difference in length, and because elastic tube 34 is disposed
`adjacent open end 26, chamber 36 is formed adjacent closed
`end 28. Slidably disposed within chamber 36 is movable
`piston 38.
`As best seen in the cross-sectional end view of FIG. 6,
`taken along line 6—6 of FIG. 5, elastic tube 34 includes
`optional striations 58 that preferably extend longitudinally
`along the length thereof. Conceptually, striations 58 are
`made from cuts or grooves formed along the inside diameter
`of elastic tube 34. Striations 58 act as stress concentrators
`
`that essentially define the geometry of axial space 46. As
`depicted in FIG. 6, striations 58 engage the stent-catheter
`assembly during the crimping process. Other shapes and
`lengths of striations 58 are contemplated, including a helical
`pattern, serpentine pattern, zig zag pattern, etc. The stria-
`tions may further have bumps or contours to apply stress to
`specific zones along the stent-catheter assembly.
`Optional compression spring 40 biases piston 38 into
`contact with elastic tube 34. Other mechanisms known in the
`
`art can be used to support piston 38 to prevent it from rattling
`or loosely moving within chamber 36. For example, in an
`alternative embodiment, rails and a dove tail can be formed
`into an outer circumference ofthe piston, respectively, allow-
`ing the piston to traverse longitudinally without losing its
`alignment and contact with the elastic tube. In yet another
`alternative embodiment, the dimensional tolerances between
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`the chassis and piston are close, and the movable piston has
`a large thickness to maintain its alignment within the chas-
`sis. In this embodiment, the piston can traverse within the
`chamber without use of the optional compression spring or
`other support structure.
`In the preferred embodiment, chamber 36 is hermetically
`sealed except for port 42 disposed between piston 38 and
`closed end 28. Port 42 is preferably connected to an inde-
`flator (not shown), known in the art, which is used to inject
`a pressurized fluid into chamber 36.
`End cap 30 includes central opening 44 that is aligned
`with axial space 46 of elastic tube 34. Central opening 44
`allows the stent-catheter assembly to be inserted into the
`present invention tool 22 prior to undergoing the crimping
`procedure.
`Leading up to the crimping procedure, a user introduces
`stent 10 already loaded onto balloon portion 14 of catheter
`11 into axial space 46 within elastic tube 34. In the exem-
`plary embodiment, the inside diameter of elastic tube 34 is
`slightly greater than the outside diameter of the uncrimped
`stent 14.
`FIG. 3 is a side elevational sectional view of stent
`
`crimping tool 22 shown in FIG. 2 undergoing the stent
`crimping process. In particular, port 42 is connected to the
`indeflator which has injected fluid into chamber 36. Pres-
`sures may range from one atmosphere in the unpressurized
`state of FIG. 2 to approximately three atmospheres in the
`pressurized state in FIG. 3. The increasing pressure inside
`chamber 36 displaces piston 38 into elastic tube 34.
`As a result, elastic tube 34 is compressed axially or
`lengthwise. The elastic material of elastic tube 34 must
`maintain a constant volume due to its surface elasticity and
`containment within the confines of chassis 24. Continuous
`
`compression of elastic tube 34 by piston 38 causes the
`material of elastic tube 34 to displace axially and then
`radially into axial space 46 within elastic tube 34. This
`decreases the diameter of axial space 46.
`In turn, stent 10 contained inside axial space 46 is
`compressed radially onto balloon portion 14 of catheter 11,
`as seen in FIG. 3. The arrows of FIG. 3 indicate movement
`
`of the material consisting of the elastic tube 34, wherein
`elastic tube 34 is contained in all directions except radially
`inward toward the center of axial space 46.
`Once stent 10 is crimped onto balloon 14, the pressure
`supplied by the indeflator can be released by reversing the
`flow out port 42. Natural resilience of elastic tube 34 causes
`it to re-assume its initial shape thereby opening up axial
`space 46 an deflecting piston 38 in the opposite direction.
`Once axial space 46 re-assumes its original diameter, the
`crimped stent-catheter assembly can be withdrawn out of
`tool 22 through central opening 44.
`FIG. 4 is a perspective view of a preferred embodiment of
`the present invention stent crimping tool 22. The partial
`cut-away view of FIG. 4 exposes the internal components of
`cylindrical shape chassis 24. As best seen in this figure,
`elastic tube 34 has a cylindrical shape contained by the
`inside diameter of cylindrical shape chassis 24. Abutting the
`back end of elastic tube 34 is piston 38. Directly behind
`piston 38 is hermetically sealed chamber 36 adjacent closed
`end 28. Flow into and out of chamber 36 is controlled by
`port 42 which may optionally be modified with a control
`valve known in the art. The stent-catheter assembly is
`inserted through central opening 44 into tool 22 to undergo
`the crimping process.
`The present invention tool 22 is designed to be used inside
`a cath lab to crimp stents 10 onto balloon catheters 11 by
`
`Page80f11
`
`Page 8 of 11
`
`

`

`6,009,614
`
`7
`exerting pressure evenly around stent 10 while it is correctly
`positioned on balloon 14 of catheter 11. Once the uncrimped
`stent-balloon catheter assembly is properly inserted inside
`axial space 46 of elastic tube 34, the assembly is locked into
`place by an optional snap lock, known in the art, at end cap
`30. After catheter 11 is locked in place thus ensuring that
`stent 10 does not change position during the crimping
`process,
`the indeflator can be attached to port 42. The
`indeflator is used to increase the pressure inside chamber 36
`which in turn exerts pressure on piston 38, which com-
`presses elastic tube 34. As explained, the inside diameter of
`elastic tube 34 decreases, compressing stent 10 onto balloon
`14 of catheter 11. The decreasing inside diameter of elastic
`tube 14 during compression is fairly homogeneous thus,
`evenly and uniformly compressing stent onto balloon 14.
`Once tool 22 has undergone a predetermined pressure
`increase inside chamber 36, the pressure can be released.
`The pressurization of chamber 36 can be repeated or termi-
`nated. Once terminated, the pressure exerted by piston 38 on
`elastic tube 34 is eliminated allowing elastic tube 34 to
`return to its original unstressed shape. Axial space 46
`reforms and the crimped stent-catheter assembly can be
`withdrawn.
`
`The present invention as explained above can be actuated
`using a hydraulic drive source to move the piston. FIG. 5
`provides a side elevational cross-sectional view of an alter-
`native embodiment which uses a mechanical drive source to
`
`actuate the piston. In this exemplary embodiment of stent
`crimping tool 48 the construction is very similar to the
`hydraulically driven tool 22, although chassis 50 no longer
`requires port 42. Also, threaded opening 52 is formed in
`closed end 56. Power screw 54 is threaded through opening
`52 and engages piston 38. Power screw 54 can be rotated
`manually by a crank, electrically by a motor, through an
`impeller driven by an indeflator, or by other means known
`in the art. Rotation of power screw 54 displaces piston 38
`into elastic tube 34 in a manner akin to the influx of fluid in
`
`the previous embodiment. Elastic tube 34 is compressed
`axially and, through the same mechanism described above,
`stent 10 is crimped on to balloon 14. Counter-rotation of
`power screw 54 retracts piston 38 and relieves pressure on
`elastic tube 34. The crimping cycle can be repeated, or the
`crimped stent-catheter assembly can be removed from tool
`48.
`
`The present invention crimping tool is preferably made
`from injection molded plastics and rubber. In an alternative
`embodiment, it is possible to use translucent or transparent
`polymers so that the crimping process can be monitored
`visually. The present invention design is also well suited to
`be made from surgical steel or like metals.
`In alternative embodiments of the present invention (not
`shown), the elastic tube can assume various geometries. For
`example, the elastic tube can be fabricated to have a star-
`shaped cross-section, or it can be fashioned to have beveled
`ends. At those beveled ends of the elastic tube, the void
`created between the beveled surface and the inside walls of
`
`the tubular chassis, piston, and end cap, can be filled with a
`rigid, plastic, fillet insert to help concentrate compression of
`the elastic tube.
`
`Still other alternative embodiments of the elastic tube may
`have an outside diameter that varies along the length thereof.
`This is shown in FIGS. 7A and 7B, which are side eleva-
`tional views taken in cross-section. In FIG. 7A, elastic tube
`60 has a dual cone profile, while in FIG. 7B, elastic tube 62
`has an ovoid profile. A single cone profile is also
`contemplated, although not shown. During the crimping
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`process, the particular outside geometry helps concentrate
`stress at specific regions of the stent-catheter assembly when
`it is positioned within axial space 46.
`The elastic tube is preferably made from an elastomer. As
`such,
`the durometer hardness/toughness ofthe elastic/
`elastomeric tube can be changed depending on the mechani-
`cal properties and design of the various stents to be crimped.
`The present invention also contemplates an elastic tube that
`can apply circumferential pressure on the stent, perhaps with
`use of bands or rings disposed along the circumference of
`the elastic tube.
`
`As is appreciated by those skilled in the art, the present
`invention stent 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 the latter scenario, where sterile
`conditions exist, the stent crimping tool can be used repeat-
`edly to crimp stents onto balloons until the elasticity in the
`elastic tube is worn or the hermetic seal in the chamber is
`
`broken. Repeated uses are therefore contemplated for the
`present invention in controlled sterile environments. On the
`other hand, single use applications are contemplated in the
`present invention and are required when used by cath lab
`personnel.
`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 in combination with a stent,
`the combination comprising;
`the tool having a rigid chassis, the rigid chassis having a
`hollow interior, a front end, and a back end;
`a back end cap enclosing the back end of the chassis;
`a front end cap having a first central opening and enclos-
`ing the front end of the chassis;
`an elastic tube having a second central opening extending
`therethrough and having a length less than the length of
`the hollow interior to define a chamber adjacent to the
`back end, the elastic tube being disposed within the
`hollow interior and adjacent the front end cap such that
`the second central opening is in axial alignment with
`the first central opening;
`a piston slidably disposed within the chamber; and
`a drive source engaging the rigid chassis and the piston
`and disposed within the