U.S. patent application number 09/401218 was filed with the patent office on 2001-05-31 for method for contracting, loading or crimping self-expanding and balloon expandable stent devices.
Invention is credited to AUSTIN, MICHAEL.
Application Number | 20010001890 09/401218 |
Document ID | / |
Family ID | 35137511 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010001890 |
Kind Code |
A1 |
AUSTIN, MICHAEL |
May 31, 2001 |
METHOD FOR CONTRACTING, LOADING OR CRIMPING SELF-EXPANDING AND
BALLOON EXPANDABLE STENT DEVICES
Abstract
An apparatus for manipulating a medical device is formed of at
least three coupled movable blades which are disposed about a
reference circle to form an aperture whose size may be varied. The
aperture capable of being sized to contain a medical device. Each
blade is in communication with an actuation device which is capable
of moving the blade to alter the size of the aperture. Each blade
includes a single radial point which a) lies on the circumference
of the reference circle prior to movement of the blade, and b) may
be moved only along a radius of the reference circle on movement of
the blade.
Inventors: |
AUSTIN, MICHAEL;
(GARDENFIELD, GB) |
Correspondence
Address: |
VIDAS, ARRETT & STEINKRAUS, P.A.
6109 BLUE CIRCLE DRIVE
SUITE 2000
MINNETONKA
MN
55343-9185
US
|
Family ID: |
35137511 |
Appl. No.: |
09/401218 |
Filed: |
September 22, 1999 |
Current U.S.
Class: |
29/282 ;
29/283.5; 72/402 |
Current CPC
Class: |
Y10T 29/49908 20150115;
Y10T 29/49925 20150115; Y10T 29/49927 20150115; A61F 2/9522
20200501; Y10T 29/4981 20150115; A61M 25/1029 20130101; A61F 2/95
20130101; A61F 2/958 20130101; Y10T 29/5367 20150115; Y10T 29/53717
20150115; A61F 2/9524 20200501; Y10T 29/53996 20150115; Y10T
29/53987 20150115; Y10T 29/49865 20150115; Y10T 29/53096 20150115;
Y10T 29/49913 20150115 |
Class at
Publication: |
29/282 ;
29/283.5; 72/402 |
International
Class: |
B23P 011/00; B21D
039/00 |
Claims
What is claimed is:
1. An apparatus for reducing in size a medical device comprising:
at least three coupled movable blades disposed about a reference
circle to form an aperture whose size may be varied, the aperture
capable of being sized to contain the medical device, each blade in
communication with an actuation device which is capable of moving
the blade to alter the size of the aperture, wherein each blade
includes a single radial point which a) lies on a radial line of
the reference circle prior to movement of the blade, and b) may be
moved only along the radial line of the reference circle on
movement of the blade.
2. The apparatus of claim 1 wherein the blades are constructed and
arranged to form a shrinkable polygonal aperture.
3. The apparatus of claim 1 wherein the blades are constructed and
arranged to form a substantially circular aperture.
4. The apparatus of claim 1 wherein the actuation device comprises
a cam, and a plurality of linear slide devices, each of the linear
slide devices in mechanical communication with the cam, and each
blade is mounted to a linear slide device, each linear slide device
movable along an axis parallel to the radius on which the radial
point of the blade lies.
5. The apparatus of claim 1 comprising from 4 to 16 blades.
6. The apparatus of claim 5 comprising 8 blades.
7. The apparatus of claim 1 wherein the blades are disposed about a
reference tube to form a tubular aperture whose size may be varied,
the reference circle lying along the reference tube, each blade in
communication with an actuation device which is capable of moving
the blade to alter the size of the tubular aperture, each blade
includes a single line which a) lies on the circumference of the
reference tube prior to movement of the blade, and b) may be moved
only along a radial plane of the reference tube on movement of the
blade.
8. The apparatus of claim 7 wherein the reference tube is a
cylinder.
9. The apparatus of claim 1 in combination with a medical device
which may be reduced in size, the medical device selected from the
group consisting of stents, grafts stent-grafts and vena cava
filters.
10. The apparatus of claim 1 wherein each blade has an inner end
and an outer end, the inner end being beveled to form a tip.
11. The apparatus of claim 13 wherein the single radial point on
each blade is at the tip of the blade
12. An apparatus for applying a radial inward force to a medical
device comprising: at least three coupled movable blades disposed
about a reference circle to form an aperture whose size may be
varied, the aperture capable of being sized to contain the medical
device, each blade in communication with an actuation device which
is capable of moving the blade to alter the size of the aperture,
wherein each blade includes a single radial point which a) lies on
the circumference of the reference circle prior to movement of the
blade, and b) may be moved only along a radius of the reference
circle on movement of the blade.
13. The apparatus of claim 12 with a medical device selected from
the group consisting of stents, grafts, stent-grafts and vena cava
filters disposed in the aperture.
14. The apparatus of claim 13 wherein the medical device is
disposed about a catheter.
15. An apparatus for crimping a medical device comprising: at least
three coupled movable blades disposed about a reference circle to
form an aperture whose size may be varied, the aperture capable of
being sized to contain the medical device, each blade in
communication with an actuation device which is capable of moving
the blade to alter the size of the aperture, wherein each blade
includes a single radial point which a) lies on the circumference
of the reference circle prior to movement of the blade, and b) may
be moved only along a radius of the reference circle on movement of
the blade.
16. A method of manipulating a medical device comprising the steps
of: providing a medical device; providing at least three blades
capable of applying a radial inward force, the blades disposed
about a reference circle to form a shrinkable aperture; placing the
medical device into the shrinkable aperture; simultaneously moving
the blades inward to apply a radial inward force to the medical
device; wherein the blades are constructed and arranged such that
each blade has a single point which a) lies on the circumference of
the reference circle prior to movement of the blade, and b) is
moved along a radius of the reference circle on movement of the
blade.
17. The method of claim 16 wherein the medical device is selected
from the group consisting of stents, stent-grafts, grafts and vena
cava filters.
18. The method of claim 17 wherein the medical device is reduced in
size.
19. The method of claim 17 wherein the medical device is
characterized by a diameter and the diameter is reduced in
size.
20. The method of claim 17 wherein the medical device is disposed
about a catheter.
21. The method of claim 17 wherein the medical device is disposed
about a balloon which is disposed about a catheter.
22. The method of claim 20 wherein a sufficient radial inward force
is applied to crimp the medical device to the catheter.
23. The method of claim 21 further comprising the steps of:
simultaneously moving the blades outward; and removing the medical
device from the aperture.
24. A method of molding a balloon comprising the steps of:
providing a balloon preform; providing at least three movable
blades disposed about a reference tube to form a shrinkable tubular
aperture, wherein the blades are constructed and arranged such that
each blade has a single line which a) lies on the surface of the
reference tube prior to movement of the blade, and b) is moved
along a radial plane of the reference tube on movement of the
blade; placing the balloon preform into the shrinkable aperture;
providing an inflation fluid; and inflating the balloon preform so
that the preform contacts the blades.
25. The method of claim 24 wherein the balloon is heated during the
inflating step to form a balloon.
26. The method of claim 25 wherein the inflation fluid is removed
from the formed balloon and the balloon is removed from the
aperture.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to an apparatus and a method for
reducing in size a medical device such as a stent, stent-graft,
graft, or vena cava filter. The apparatus may be used in particular
for fastening a medical device onto a catheter.
[0002] Medical devices such as stents, stent-grafts, grafts, or
vena cava filters and catheters for their delivery are utilized in
a number of medical procedures and situations, and as such their
structure and function are well known.
[0003] A stent, for example, is a generally cylindrical prosthesis
introduced via a catheter into a lumen of a body vessel in a
configuration having a generally reduced diameter and then expanded
to the diameter of the vessel. In its expanded configuration, the
stent supports and reinforces the vessel walls while maintaining
the vessel in an open, unobstructed condition.
[0004] Stents are typically inflation expandable or self-expanding.
Self expanding stents which are constrained by a sheath or other
restraining means, must be provided in a reduced diameter.
[0005] An example of a stent described in PCT Application No. 960
3092 A1, published Feb. 8, 1996.
[0006] In advancing a stent through a body vessel to the deployment
site, the stent must be able to securely maintain its axial
position on the delivery catheter, without translocating proximally
or distally, and especially without becoming separated from the
catheter. Stents that are not properly secured or retained to the
catheter may slip and either be lost or be deployed in the wrong
location. The stent must be crimped in such a way as to minimize or
prevent altogether distortion of the stent and to thereby prevent
abrasion and/or reduce trauma of the vessel walls.
[0007] In the past, this crimping or size reduction has been done
by hand often resulting in the application of undesired uneven
forces to the stent. Such a stent must either be discarded or
re-crimped. Stents which have been crimped or otherwise reduced in
size multiple times can suffer from fatigue and may be scored or
otherwise marked which can cause thrombosis. A poorly crimped stent
can also damage the underlying balloon.
[0008] Recently, stent crimping devices halve been disclosed in
U.S. Pat. No. 5,546,646 to Williams et al, U.S. Pat. No. 5,183,085
to Timmermans et al., U.S. Pat. No. 5,626,604 to Cottone, Jr., U.S.
Pat. No. 5,725,519, U.S. Pat. No. 5,810,873 to Morales, WO 97/20593
and WO 98/19633.
[0009] A cam actuated stent crimper, shown in FIG. 1, employs a
plurality of arc-shaped or curved slots with semi-circular ends,
disposed such that each slot or cam engages a cam follower bearing
22. The arc-shaped or curved surfaces of the slots are inclined to
be non-concentric relative to the axis of rotation 26, and
therefore rotation of the cam plate 28 transmits equal radial
displacements to the cam follower bearings 22, to simultaneously
actuate a like number of linear bearings 24, which have their
corresponding linear tracks or rails mounted on a fixed plate. As
shown in FIG. 1 the cam plate rotary drive 29 comprises a pneumatic
cylinder mounted on a pivot or trunnion, arranged with the cylinder
rod connected rotatably to a short arm fixed rigidly to the cam
plate. Accordingly, linear motion produced by the pneumatic
cylinder translates into controllable arcs of motion of the
circular cam plate, which has a projecting V-shaped profile on its
outer edge in rolling engagement with three equally spaced rollers
with mating inverse V-shaped profiles to provide precise rotatable
support to the cam plate. Depending on the direction of rotation,
the linear slides which each carry a radially disposed crimping
blade, are either moved inwards to apply a crimping force to the
stent, or outwards to release the stent. Also when crimping,
depending on the degree of rotation of the cam plate, a specific
radial crimping displacement may be obtained to match the diametral
reduction required for any particular stent.
[0010] All US patents and applications and all other published
documents mentioned anywhere in this application are incorporated
herein by reference in their entirety.
BRIEF SUMMARY OF THE INVENTION
[0011] It would be desirable to produce at device capable of
crimping a stent uniformly while minimizing the distortion of and
scoring and marking of the stent due to the crimping. The present
invention is directed to that end.
[0012] The present invention is particularly concerned with the
crimping and otherwise reducing in size of inflation expandable
stents, self-expanding stents and other expandable medical devices.
For the purpose of this disclosure, it is understood that the term
`stent` includes stents, stent-grafts, grafts and vena cava
filters. It is also understood that the term `crimping` refers to a
reduction in size or profile of a stent.
[0013] In the description that follows it is understood that the
invention contemplates crimping a medical device either directly to
a catheter tube or to a catheter balloon which is disposed about a
catheter tube. When reference is made to crimping a medical device
to a catheter, a balloon may be situated between the medical device
and the catheter tube or the medical device may be crimped to a
region of a catheter tube directly. The invention also contemplates
crimping a stent in the absence of a catheter to reduce the stent
in size.
[0014] The present invention is directed, in one embodiment, to an
apparatus for reducing a medical device in size. Desirably, the
medical device is a stent, a stent-graft, a graft or a vena cava
filter, whether self-expandable, balloon expandable or otherwise
expandable, although the inventive apparatus may also be employed
with any other suitable, generally tubular medical device which
must be reduced in size.
[0015] The inventive apparatus comprises at least three coupled
movable blades disposed about a reference circle to form an
aperture whose size may be varied. Each blade is in communication
with an actuation device which is capable of moving the blade to
alter the size of the aperture. Each blade includes a single radial
point on the surface of the blade which a) lies on the
circumference of the reference circle prior to movement of the
blade, and b) may be moved only along a radius of the reference
circle on movement of the blade.
[0016] The apparatus further includes an actuation device which
comprises a cam and a plurality of linear slide devices. Each
linear slide device is in communication with a blade. Each of the
linear slide devices is also in mechanical communication with the
cam. Rotation of the cam results in linear translation of the slide
device and blade, such that the slide device moves along an axis
parallel to the radius on which the radial point of the blade lies
or along the radius itself.
[0017] The invention is also directed to an apparatus similar to
that described above, with blades disposed about a reference tube
to form a tubular aperture whose size may be varied. Each blade is
in communication with an actuation device which is capable of
moving the blade to alter the size of the tubular aperture. Each
blade includes a single line which a) lies on the surface of the
reference tube prior to movement of the blade, and b) may be moved
only along a radial plane of the reference tube on movement of the
blade.
[0018] The inventive apparatus finds particular utility in crimping
a medical device such as those mentioned above to a catheter or to
a balloon disposed about a catheter.
[0019] The inventive apparatus also finds utility in reducing the
diameter of a medical device such as those mentioned above prior to
crimping.
[0020] The invention is also directed to a method of manipulating a
medical device which comprises the steps of providing the medical
device and providing at least three blades capable of applying a
radial inward force. The blades are disposed about a reference
circle to form a shrinkable aperture. A medical device such as a
stent is placed into the shrinkable aperture and the blades
simultaneously moved inward to apply a radial inward force to the
medical device. The blades are constructed and arranged such that
each blade has a single point which a) lies on the circumference of
the reference circle prior to movement of the blade, and b) is
moved along a radius of the reference circle on movement of the
blade.
[0021] The inventive apparatus may also be used as a variable size
balloon mold. To that end, the invention is further directed to a
method of molding a medical balloon. In the practice of the method,
a balloon preform prepared through any suitable technique known in
the art is provided. The preform is placed in an apparatus which
has a shrinkable tubular aperture formed by at least three movable
blades disposed about a reference tube. The blades are constructed
and arranged such that each blade has a single line which a) lies
on the surface of the reference tube prior to movement of the
blade, and b) is moved along a radial plane of the reference tube
on movement of the blade. The aperture may be set to a
predetermined size prior to placement of the preform therein or
after placement of the preform therein. An inflation fluid is
supplied to the balloon preform to expand the balloon preform until
it contacts the blades. The preform may optionally be heated prior
to, during or after the blowing step. The thus formed balloon is
then pressure relieved and removed from the apparatus.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0022] FIG. 1 shows a perspective view of a stent crimper;
[0023] FIG. 2a is a schematic front view of an embodiment of the
inventive apparatus;
[0024] FIG. 2b is a schematic front view of the embodiment of FIG.
2a after the stent has been reduced in size;
[0025] FIGS. 3a and 3b are schematics of blades;
[0026] FIG. 3c is a partial schematic front view of an embodiment
of the inventive apparatus employing the curved blades of FIG.
3b;
[0027] FIG. 4a is a partial front view of an embodiment of the
inventive apparatus;
[0028] FIG. 4b is a partial front view of an embodiment of the
inventive apparatus;
[0029] FIG. 4c shows a side view of the embodiment of FIG. 4b taken
along lines 4c-4c;
[0030] FIG. 5a shows a partial front view of another embodiment of
the inventive apparatus;
[0031] FIG. 5b shows a link connected to a blade;
[0032] FIG. 6 is a schematic, perspective view of an embodiment of
the inventive apparatus;
[0033] FIG. 7 shows a partial view of the embodiment of FIG. 6;
[0034] FIGS. 8a and 8b are partial side elevational views of an
embodiment of the inventive apparatus taken along a radial plane
during the size reduction process;
[0035] FIG. 8c is a partial side elevational view of an embodiment
of the inventive apparatus taken along a radial plane following
crimping of a stent to a catheter;
[0036] FIG. 9 is a diagrammatic side elevational view of an
embodiment of the inventive apparatus;
[0037] FIG. 10 is a partial side elevational view of an embodiment
of the inventive apparatus taken along a radial plane of an
embodiment of the invention consisting of three individual
apparatuses arranged sequentially;
[0038] FIG. 11 is a schematic showing a stent being reduced in size
and loaded into a sheath;
[0039] FIG. 12 is a partial side elevational view of an embodiment
of the inventive apparatus taken along a radial plane showing a
balloon that has been molded with the inventive device; and
[0040] FIG. 13 is a partial side elevational view taken along a
radial plane showing a stepped balloon that has been molded with
the inventive device.
DETAILED DESCRIPTION OF THE INVENTION
[0041] While this invention may be embodied in many different
forms, there are described in detail herein specific preferred
embodiments of the invention. This description is an
exemplification of the principles of the invention and is not
intended to limit the invention to the particular embodiments
illustrated.
[0042] As shown generally at 100 in FIGS. 2a and 2b, the inventive
apparatus comprises eight coupled blades 106 disposed about a
reference circle 114 to form an aperture 118 whose size may be
varied. The apparatus may comprise as few as three blades and as
many as sixteen or more blades. Desirably, the apparatus will have
four or more blades and more desirably, eight or more blades. The
maximum number of blades is limited only by how many blades can
physically be coupled together under the relevant size constraints.
As the number of blades is increased, the profile of the aperture
and hence of the medical device following reduction in size,
becomes smoother. FIG. 2b shows the apparatus of FIG. 2a after the
stent has been reduced in size.
[0043] Blades 106 as shown in FIG. 3a have an inner end 108 which
is desirably beveled 111 so as to mesh with adjacent blades and an
outer end 110 which is displaced from aperture 118. Aperture 118 is
polygonal. Blades 106 may also be shaped with a curved end 112, as
shown in FIGS. 3b and 3c so as to form a substantially circular
shaped aperture, when the aperture is fully closed.
[0044] Each blade 106 includes a single radial point 122 which lies
on a radial line 126 of reference circle 114 prior to movement of
blade 106 and which may be moved only along the radius 126 of
reference circle 114 on movement of blade 106. Desirably, the
single radial point 122 will be disposed at the tip of the blade
adjacent to beveled end 111.
[0045] In the embodiment shown in FIG. 4a, radial point 122 lies at
the tip of blade 106. Each blade 106 has a connecting link 130
extending from second end 110. Connecting link 130 ends in mounting
means 134, typically a mounting flange adapted for attachment to a
linear bearing block, for interfacing with an actuation device,
shown generally at 138. Actuation device 138 is capable of
simultaneously moving blades 106 to alter the size of aperture
118.
[0046] Actuation device 138 includes actuation plate 142 which is
coaxial with reference circle 114. Actuation plate 142 has eight
equi-spaced radial slots 146. More generally, for every blade there
will be a corresponding radial slot on actuation plate 142. Each
radial slot 146 overlaps a mounting means 134 for a linear bearing
block at the end of a connecting link 130. Each blade 106 is
engaged to actuation plate 142 via a cam follower bearing 150
disposed in radial slot 146 and attached to mounting means in
slotted end 134.
[0047] Each bearing 150 extends from a linear slide 154. Linear
slide 154 is mounted on a non-rotating plate 156 (shown in FIG. 8).
Linear slide 154 is constructed and arranged to slide along a line
158 which is parallel to the radius 126 on which radial point 122
of blade 106 lies.
[0048] For the purposes of this disclosure, the term `cam follower
bearing` includes cam follower bearings, low friction rollers,
roller bearings, needle roller bearings and a slipper block pivot
mounted on a bearing and stub shaft. FIG. 4b is a partial front
view of an embodiment in which a slipper block is used. A side view
of the embodiment of FIG. 4b taken along lines 4c-4c is shown in
FIG. 4c. Slipper block 150 resides in slot 146 of actuation plate
142. Slipper block 150 is mounted on stub shaft 151 which extends
from connecting link 130. Desirably, bearings 153 will be present
between shaft 151 and slipper block 150. Connecting link 130, in
turn, is fastened to linear bearing block 212 via fasteners 214.
Bearing block 212 is linearly mounted on linear slide which is
mounted on fixed plate 156. Linear motion is facilitated by the
presence of bearings 216.
[0049] Cam follower bearing 150 may be replaced by any other
suitable connecting member which can connect the slide and the
link.
[0050] In use, as actuation plate 142 is rotated in a clockwise
direction, the clockwise motion of the actuation plate is
translated into linear motion of each of linear slide 154 and blade
106 via bearing 150. Each blade 106 moves outward in a direction
parallel to the radius 126 on which the radial point 122 of the
blade 106 lies, resulting in the opening of aperture 118. As
actuation plate 142 is rotated in a counterclockwise direction,
each blade 106 moves inward in a direction parallel to the radius
126 on which the radial point 122 of the blade 106 lies, resulting
in the closing of aperture 118. As aperture 118 closes, a radially
inward force is applied to a medical device disposed in the
aperture. The actuation plate is rotated until the desired size
reduction of the aperture and medical device has been achieved.
Following the reduction, the actuation plate is rotated in the
opposite direction to allow for removal of the medical device from
the aperture.
[0051] The apparatus may be used to reduce the diameter of a
suitable medical device such as those disclosed above or may be
used to crimp a medical device to a catheter.
[0052] Another embodiment of the invention is shown in FIG. 5a.
Each blade 106, as shown in FIG. 5a, has a connecting link 130
extending therefrom. Connecting link 130 is rigidly attached to
blade 106. Connecting link 130 ends in an angled end 134 for
interfacing with an actuation device, shown generally at 138.
Actuation device 138 is capable of simultaneously moving blades 106
to alter the size of aperture 118.
[0053] Actuation device 138 includes a rotatable actuation plate
142 which is co-axial with reference circle 114. Rotatable
actuation plate includes cam slots 146 which are not concentric
with the axis of rotation, arcing inward. Each connecting link 130
is engaged to actuation plate 146 via a cam follower bearing 150
disposed in slot 146 and attached to both angled end 134 of
connecting link 130 and to a linear slide 154. Linear slide 154 is
mounted on a non-rotating plate similar to that shown in FIG. 8.
Linear slide 154 is constructed and arranged to slide along a
radial line 158 on which radial point 122 of blade 106 lies.
[0054] Connecting link 130 may be bonded adhesively, welded, joined
with a fastener or otherwise joined to blade 106. As shown in FIG.
5a, a single screw 131 is used to connect link 130 to blade 106.
FIG. 5b shows a connecting link 130 including a right angle portion
which is fastened to a blade 106 using two screws 131. Connecting
link 130 and blade 106 may optionally be formed of a single piece
of material. Regardless of how the connecting member is joined to
the blade, no movement of the blade relative to the connecting link
is permitted.
[0055] In use, as actuation plate 142 is rotated in a clockwise
direction, the clockwise motion of the actuation plate is
translated into a linear outward motion of each of linear slides
154 and blades 106 via bearings 150 resulting in the opening of
aperture 118. The outward motion results from the radially outward
arcing of cam slot 146. As actuation plate 142 is rotated in a
counterclockwise direction, each blade 106, because of the radially
inward arc of cam slots 146, moves inward in a direction parallel
to the radius 126 on which the radial point 122 of the blade 106
lies, resulting in the closing of aperture 118. As discussed above,
as the aperture is decreased in size, a radial inward force is
brought to bear against a medical device disposed in the aperture,
thereby reducing the size of the medical device.
[0056] The embodiment of FIG. 5a differs from the embodiment of
FIG. 4a in that in the embodiment of FIG. 5a, the slide moves along
the radial line on which the radial point of the attached blade
lies whereas in FIG. 4a the slide moves parallel to the radial
line. In both of the embodiments, each of the blades is constrained
with two degrees of freedom to satisfy the condition that the
movement of the tip be radial in accordance with the invention.
[0057] In the embodiments of FIGS. 4a and 5a, the slots in the
actuation plate are constructed and arranged to allow for a
sufficient reduction in size of the aperture so that a medical
device can be reduced in size to a desired diameter. Those of
ordinary skill in the art will recognize other suitable actuation
devices that may be used in the practice of this invention.
[0058] Desirably, in the above embodiments, the blades will be as
long as or longer than the medical device disposed within so that
the medical device is uniformly reduced in size along its entire
length.
[0059] This is illustrated in the embodiment of FIGS. 6 and 7 and
further in FIGS. 3a and 3b in which blades 106 are disposed about a
reference tube 160 to form a tubular aperture 162 whose size may be
varied. Reference circle 114 is seen to lie along reference tube
160. Each blade 106 is in communication with an actuation device
such as that shown in FIGS. 4 or 5. The actuation device is capable
of moving blades 106 to alter the size of tubular aperture 162.
Each blade 106 includes a single line 166 which a) lies on a radial
plane 170 of the reference tube 160 prior to movement of blade 106,
and b) may be moved only along a radial plane 170 of reference tube
160 on movement of blade 106. Desirably, reference tube 160 is
cylindrical and exceeds the length of the medical device to be
reduced in size.
[0060] Another embodiment of the invention is illustrated in FIGS.
8a and 8b. In the embodiment of FIGS. 8a and 8b, two non-rotating
plates 156 are present, one at each end of the apparatus. Each
blade 106 is connected at first end 174 to a linear slide 154a via
a connecting link 130a and at second end 178 to a linear slide 154b
a via a connecting link 130b. Linear slide 154a is mounted on
non-rotating plate 156a and linear slide 154b is mounted on
non-rotating plate 156b. The presence of the second non-rotating
plate 156b, linear slide 154b and connecting link 130b is optional
but contributes to providing a rigid frame upon which the
connecting links and associated blades may slide without
misalignment relative to the reference circle.
[0061] FIGS. 8a and 8b illustrate the use of the inventive
apparatus in various stages of the size reduction process. In FIG.
8a, stent 180 has been placed in tubular aperture 162 which is
characterized by a diameter d.sub.1. In FIG. 8b, the device has
been actuated by rotating actuation plate 142 so as to move blades
106 inward. Aperture 162, as shown in FIG. 8b is characterized by a
diameter d.sub.2 which is reduced relative to diameter d.sub.1.
Stent 180 is seen to be of reduced diameter relative to its
previous diameter as shown in FIG. 8a.
[0062] FIG. 8c differs from FIG. 8b, only in that stent 180 has
been crimped onto catheter 184 in FIG. 8c.
[0063] Blades 106 may be made of any suitable, hard material
including hardened steel. Desirably, the blades will be made of a
material such as zirconia ceramic. Blades made of zirconia ceramic
may be used without lubrication. Furthermore, because of their low
thermal conductivity, they may be used to create a highly insulated
chamber suitable for cryogenic processing of martensite in nitinol
stents.
[0064] Such an embodiment is shown in FIG. 9. Stent 180 is disposed
between blades 106 which can move inward in the direction of the
arrows. Blades 106 are cooled by a first source of cooling fluid
184 located at first end 174 of blades 106. Although not shown, a
second source of cooling fluid may be provided at second end 178 of
blades 106 as well. The cooling fluid may be a liquid cryogenic.
Exemplary cryogenics include liquid nitrogen, argon or carbon
dioxide although other cryogens may also be used. The cooling fluid
may also be a chilled gas such as air. The cooling fluid may also
be a cooled inert gas such as nitrogen, argon or other inert
gasses.
[0065] The aperture formed by the blades is a highly insulated
chamber which is suitable for cryogenic processing of martensite in
nitinol stents. The chamber is maintained at -80.degree. C. and a
nitinol stent inserted therein. Upon equilibration of the
temperature of the stent, the blades are moved inward to reduce the
diameter of the stent. The stent is thus reduced in diameter while
being maintained in the martensitic state.
[0066] The embodiment of FIG. 9 further has a loading plunger 188
for loading a stent or other suitable medical device into the
aperture. A sheath housing 192 which houses sheath 196 is provided
at second end 178 of blades 106. Plunger 188 may be further used to
transfer the stent after it has been reduced in diameter or size to
sheath 196. Desirably, sheath 196 will have a slightly larger
diameter than stent 180 following reduction in size of the stent.
More desirably, the fit of the stent within the sheath will be
within about {fraction (1/32)}" and even more desirably, within
about {fraction (1/64)}".
[0067] Where lengthy stents or other medical devices are to be
reduced in size, the invention contemplates using one of the above
described apparatuses with long blades to accommodate the stent. As
an alternative, the invention also contemplates disposing two or
more of such apparatuses sequentially to form one long aperture.
The two or more apertures may then be reduced in size
simultaneously or consecutively. The arrangement of FIG. 10 shows
an embodiment with three devices 100a-c arranged sequentially. A
stepped reduction in size may be achieved by placing a stent 180 or
similar medical device in the apparatus and independently reducing
each aperture 118 a-c to a desired size. To that end, the invention
may provide particular utility in manipulating bifurcated stents or
other stents whose diameter varies along its length. The embodiment
of FIG. 10 shows the end portions of the stent being reduced in
size prior to the middle portion of the stent. The device may also
be operated so as to reduce the middle portion in size prior to the
end portions or in any other sequence.
[0068] The invention contemplates yet another approach to reducing
the diameter of lengthy stents or similar medical devices, namely
walking the stent through the apparatus. This may be accomplished
by either moving the stent relative to the apparatus or moving the
apparatus relative to the stent as shown schematically in FIG. 11.
To that end, stent 180 is inserted in device 100. Aperture 118a is
reduced in size with blades 106a in turn reducing portion 180a of
stent 180 in size. Aperture 118a is then opened and aperture 118b
reduced in size thereby reducing portion 180b of stent 180.
Simultaneously, or shortly thereafter, sheath 196 is pushed by
plunger 188 over the portion of the stent that has been reduced in
size. Aperture 118b is opened and the stent advanced in the
apparatus. The process is repeated until the entire length, or the
desired portion of the stent or medical device is reduced in
size.
[0069] The reduction in size of the stent or other medical device
may occur as part of a precrimping step or it may occur as part of
crimping a stent onto a catheter and desirably, onto a balloon
disposed about a catheter. In a general sense, it may be used for
manipulating a medical device and specifically, for applying a
radial inward force to a medical device.
[0070] In another embodiment, the invention is directed to a method
of manipulating a medical device. As part of the method, a medical
device such as those disclosed above is provided. The device has at
least three blades capable of applying a radial inward force. The
blades are disposed about a reference circle to form a shrinkable
aperture. The blades are constructed and arranged such that each
blade has only a single point which a) lies on the circumference of
the reference circle prior to movement of the blade, and b) is
moved along a radius of the reference circle on movement of the
blade. The medical device is placed into the shrinkable aperture
and the blades simultaneously moved inward to apply a radial inward
force to the medical device and thereby reduce the medical device
in size, and desirably, in diameter. Following reduction in size of
the medical device, the blades are simultaneously moved outward and
the medical device removed from the aperture.
[0071] The inventive apparatus may also be incorporated into a blow
molding tool to provide a variable size balloon mold as shown
generally at 100 in FIG. 12. The various parts of the apparatus of
FIG. 12 have been discussed in conjunction with FIGS. 8a-c and,
with exception of balloon 181 and mold cavity ends 193, the
reference numerals used in FIG. 12 correspond to those used for
FIGS. 8a-c. Mold cavity ends 193 may be provided in a variety of
sizes and lengths to contain the balloon at each end. Desirably,
the end molds will be adjustably mounted to a portion of the
apparatus such as fixed plates 156 to provide for an adjustable
length balloon mold.
[0072] The invention is also directed to a method for molding a
medical balloon using the inventive apparatus described above. A
balloon preform prepared through any standard method is provided.
The inventive mold, shown generally at 100 is also provided.
Balloon 181 is inserted into aperture 162. Aperture 162 is
optionally reduced to a predetermined size and the preform expanded
using standard techniques. An inflation fluid, for example, may be
supplied to the preform and the preform expanded and heated. The
balloon in its expanded state is shown in FIG. 12.
[0073] More generally, the invention may be practiced by providing
at least three movable blades disposed about a reference tube to
form a shrinkable tubular aperture. The blades are constructed and
arranged such that each blade has a single line which a) lies on
the surface of the reference tube prior to movement of the blade,
and b) is moved along a radial plane of the reference tube on
movement of the blade. A balloon preform is placed into the
shrinkable aperture. The aperture may be set at a predetermined
size prior to or following insertion of the balloon therein. An
inflation fluid is provided and the balloon preform inflated so
that the preform expands to the size of the aperture. The preform
may be heated during this inflation blowing step. The inflation
fluid is then removed from the thus formed balloon and the balloon
removed from the apparatus.
[0074] The balloon may be also be molded in accordance with the
method described in U.S. Pat. No. 5,163,989, or in accordance with
other methods as are known to those of ordinary skill in the art,
substituting the instant apparatus for the standard balloon mold.
Other patents which discuss balloon molding include U.S. Pat. No.
5,807,520. Other references illustrating the materials and methods
of making catheter balloons include: U.S. Pat. No. 4,413,989 and
U.S. Pat. No. 4,456,000 to Schjeldahl et al, U.S. Pat. No.
4,490,421, U.S. Pat. No. Re 32,983 and U.S. Pat. No. Re 33,561 to
Levy, and U.S. Pat. No. 4,906,244, U.S. Pat. No. 5,108,415 and U.S.
Pat. No. 5,156,612 to Pinchuck et al.
[0075] The use of the inventive apparatus as a mold allows for the
blowing of a balloon to a predetermined size using a single
adjustable size balloon mold thereby eliminating the need to have
multiple molds of different sizes.
[0076] The invention further contemplates molding a balloon to a
desired shape using a plurality of the inventive devices arranged
sequentially. As an example of this, shown in FIG. 13, a stepped
balloon 181 may be prepared by arranging several devices 100a, 100b
and 100c sequentially. A balloon preform is inserted in the
aperture formed by the device. The aperture of each device may be
preset at a desired size or may be reduced in size to a
predetermined size after the balloon preform is inserted therein.
The balloon may then be blow molded in accordance with any suitable
blow molding technique known in the art.
[0077] The invention is also understood to be directed to
embodiments employing various combinations of the features
disclosed herein.
[0078] The above disclosure is intended to be illustrative and not
exhaustive. This description will suggest many variations and
alternatives to one of ordinary skill in this art. All these
alternatives and variations are intended to be included within the
scope of the attached claims. Those familiar with the art may
recognize other equivalents to the specific embodiments described
herein which equivalents are also intended to be encompassed by the
claims attached hereto.
* * * * *