U.S. patent application number 11/076568 was filed with the patent office on 2006-09-14 for stent delivery system.
This patent application is currently assigned to Cook Incorporated. Invention is credited to Fred T. Parker, Anthony O. Ragheb.
Application Number | 20060206187 11/076568 |
Document ID | / |
Family ID | 36602791 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060206187 |
Kind Code |
A1 |
Parker; Fred T. ; et
al. |
September 14, 2006 |
Stent delivery system
Abstract
A stent delivery system includes at least one stent and a
holder. The stent is expandable from a compressed state to an
expanded state. The holder is configured to interfere or interlock
with the stent. The holder may be blowmolded onto an inner surface
of the compressed stent. An outer diameter of the holder is
approximately the same as an inner diameter of the stent.
Inventors: |
Parker; Fred T.;
(Unionville, IN) ; Ragheb; Anthony O.; (West
Lafayette, IN) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE/CHICAGO/COOK
PO BOX 10395
CHICAGO
IL
60610
US
|
Assignee: |
Cook Incorporated
MED Institute, Inc.
|
Family ID: |
36602791 |
Appl. No.: |
11/076568 |
Filed: |
March 9, 2005 |
Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
B29C 2049/0089 20130101;
B29L 2031/7542 20130101; A61F 2/958 20130101; B29C 49/44 20130101;
A61F 2002/9583 20130101; A61F 2/95 20130101; A61F 2002/9665
20130101; B29K 2105/258 20130101 |
Class at
Publication: |
623/001.11 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Claims
1. A stent delivery system, comprising: at least one stent
expandable from a compressed state to an expanded state; and, a
holder interlocking and interfering with the stent in the
compressed state, an outer diameter of the holder thereby
contacting an inner diameter of the stent.
2. The stent delivery system of claim 1, wherein the holder is
blowmolded onto an inner surface of the stent in the compressed
state.
3. The stent delivery system of claim 1, wherein the holder
includes a pattern or impression that extends through the stent in
the compressed state.
4. The stent delivery system of claim 1 wherein: the stent includes
a plurality of radial openings, the radial openings being defined
in part by side surfaces of the stent; and, the holder having a
portion extended from the outer diameter of the holder, the portion
contacting the side surfaces of the stent, the portion thereby
restricting longitudinal movement of the stent relative to the
holder.
5. The stent delivery system of claim 1, further comprising: a
stimulator adapted to apply a predetermined force to an inner
surface of the holder, thereby releasing the stent from the holder,
wherein the stent delivery system comprises no sheath.
6. The stent delivery system of claim 5, wherein the stimulator
includes a ball that has a diameter larger than an inner diameter
of the holder.
7. The stent delivery system of claim 5, wherein an outer diameter
of the stent delivery system is smaller than about 0.0540 inch.
8. The stent delivery system of claim 5, further comprising: a
container positioned inside the holder and storing a liquid
supplied thereto, wherein the liquid is compatible with blood,
whereby the stent is released from the holder in response to
increased pressure of the container.
9. The stent delivery system of claim 1, wherein a plurality of
stents are longitudinally arranged one after another and the
plurality of stents are different in size, length and/or
flexibility.
10. A method for deploying a stent, wherein the stent is configured
to expand from a compressed state to an expanded state, comprising:
delivering the compressed stent placed on a blowmolded holder and
the holder into a predetermined deployment site, the holder being
blowmolded to the compressed stent; releasing the stent from
interference with the holder; and expanding the stent from the
compressed state to the expanded state.
11. The method of claim 10, further comprising: delivering a
container into the deployment site and positioning the container
inside the holder; supplying a quantity of liquid into the
container; stimulating an inner surface of the holder in response
to an increased pressure of the container, wherein the increased
pressure is responsive to supply of the liquid.
12. The method of claim 10, further comprising: delivering a
stimulator attached to a wire to a predetermined deployment site,
the wire extending from a proximal end to a distal end; delivering
the compressed stent and the holder to the deployment site by
threading the wire through an interior of the holder; and
stimulating an inner surface of the holder by retracting the
stimulator toward the proximal end, wherein a diameter of the
stimulator is larger than an inner diameter of the holder.
13. The method of claim 10, further comprising: (a) delivering the
plurality of stents in the compressed state and the holder to a
predetermined deployment site; (b) retracting the sheath toward a
proximal end to the extent that a first stent is exposed wherein
the first stent is disposed distally adjacent a distal end; (c)
expanding the first stent from the compressed state to the expanded
state; (d) retracting the sheath toward the proximal end to the
extent that a second stent is exposed wherein the second stent is
disposed proximally adjacent the first stent; and, (e) repeating
the step of (a)-(d) until remaining stents are expanded.
14. A method for manufacturing a stent delivery system having a
holder and at least one stent configured to expand from a first
diameter to a second diameter, wherein the second diameter is
larger than the first diameter, comprising: compressing the stent
to the first diameter; inserting the stent into a first tube;
placing a second tube inside the first tube and inside an inner
diameter of the stent, wherein the second tube is airtight; and,
applying pressure and heat suitable to the second tube, thereby
blowmolding the second tube against the stent.
15. The method of claim 14, wherein the pressure ranges between 30
psi and 90 psi.
16. The method of claim 14, wherein the heat ranges between
200.degree. F. and 280.degree. F.
17. The method of claim 14, wherein the pressure is about 40 psi
and the heat ranges between 210.degree. F. and 220.degree. F.
18. The method of claim 14, wherein the pressure is about 90 psi
and the heat is about 250.degree. F.
19. The method of claim 14, further comprising: applying a drug
coating material on an outer surface of the stent in the compressed
state.
20. The method of claim 14, wherein the step of applying the drug
coating material includes spraying the drug coating material.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The invention relates to a stent delivery system. More
particularly, the invention relates to a stent delivery system
having a holder interlocking and interfering with a stent.
[0003] 2. Related Art
[0004] Stents are commonly used to treat stenosis of various
arteries. Where blood vessels are clogged or narrowed by substances
that restrict blood flow, stents are delivered into such vessels
and expanded to dilate blood vessels or maintain the dilated state
of blood vessels. Expansion of stents may be made with or without
the aid of a balloon. Balloon-expandable stents are expanded by
inflating a balloon disposed beneath a stent. On the other hand,
self-expandable stents are capable of expanding without the use of
a balloon. For this purpose, self-expandable stents are generally
made from shape memory or spring metal, such as nitinol or
stainless steel, so that self-expandable stents are able to expand
from a compressed state upon removal of pressures applied
thereon.
[0005] Determining the proper stent to use is the first step to
deploying a stent. The proper stent is determined, in part, based
on where a stent is to be deployed. For example, balloon-expandable
stents are suitable for coronary arteries, whereas self-expandable
stents are more suitable for peripheral arteries. However, the uses
of balloon-expandable stents and self-expandable stents often
overlap, and each type of stent may be used in a variety of
applications. In addition, long lesions or tandem lesions require
long coverage. Multiple short stents or a single long stent may be
implanted in long lesions or tandem legions.
[0006] Once deployed into a human body such as an artery, stents
generally remain as permanent implants. Accordingly, stents need to
comply with high quality standards and minor manufacturing defects
on the stents may result in the manufacturing rejection of the
stents. Stents are generally manufactured through complicated and
labor-intensive processes. Stent manufacturing processes include
laser cutting spring metal to form multiple, interconnected struts
of a stent; sandblasting a stent to eliminate debris generated from
the laser cutting, and electropolishing processes. Because of these
processes, it is more difficult to manufacture long stents with
high precision and quality than short stents, in part because a
long stent is prone to manufacturing defects along the length
compared to a short stent. Where a long stent is rejected due to
manufacturing defects, material costs and manufacturing expenses
substantially increase.
[0007] Although defect-free long stents may be successfully
manufactured, conventional stent delivery systems tend to
improperly deploy long stents. This is particularly a problem in
conventional stent delivery systems where uneven, high forces are
applied at the proximal end to push a long stent out of the
delivery system upon deployment. FIGS. 1A and 1B illustrate a
conventional stent delivery system 1 for a self-expandable stent
10. The stent delivery system 1 includes the self-expandable stent
10, a holder 18 and a sheath 8. The sheath 8 radially constrains
the stent 10 during delivery and is retracted when the stent 10
needs to be deployed as shown in FIG. 1B. The holder 18 is disposed
beneath the stent 10 and supports the stent 10 during delivery. The
stent 10 expands from a compressed state to an expanded state as
shown in FIGS. 1A and 1B. The stent delivery system 1 is mounted on
one end of a delivery catheter 50. The delivery catheter 50 has an
outer tube 8 functioning as a sheath and a core 4, which
longitudinally extends from a proximal end 20 to a distal end 22.
The core 4 is connected to a hub 2 at the proximal end 20 and to a
holder 18 at the distal end 22. The outer tube 8 is connected to a
handle 7. A physician deploys the stent 10 by pulling the handle 7
towards the hub 2. As the outer tube 8 is retracted by pulling the
handle 7, the stent 10 is exposed and starts expanding. The stent
10 is fully deployed when the handle 7 reaches the hub 2. However,
the stent delivery system 1 often experiences problems when the
stent to be deployed is long. Deployment of long stents often
requires high concentrated force particularly at the proximal end
22 to push the long stent out of the stent delivery system 1. This
frequently results in improper or inaccurate deployment of the long
stent.
[0008] In addition to improper deployment of long stents, the stent
delivery system 1 presents other disadvantages as well. One
disadvantage is that it is difficult to reduce the size of the
stent delivery system 1. It is generally desirable for most stent
delivery systems to have a low profile. Stent delivery systems that
have lower profiles reduce possible damage to blood vessels during
delivery and deployment of the stent. Further, stent delivery
systems with lower profiles may be able to get to small and/or
tortuous blood vessels. However, the sheath 8 substantially
increases the overall profile of the stent delivery system 1. When
the sheath 8 is retracted, the stent 10 may unexpectedly and/or
uncontrollably move. As previously stated, because the stent 10 is
made from spring metal, it tends to expand upon retraction of the
sheath 8. This makes it difficult for physicians to accurately
position the stent 10. Various attempts have been made to address
this problem. For example, structures such as rings and shafts may
be added to an inner holder adjacent the proximal end. These
structures may engage the proximal end of a stent in order to
longitudinally restrain the stent. When the sheath is retracted,
the distal end of the stent is first exposed into the blood vessel.
Because the proximal end of the stent is temporarily restrained by
these structures, the stent may not abruptly move in response to
the retraction of the sheath. However, the structures, such as
rings and shafts, may be counterproductive to accurate deployment
of stents because they trap the stent which must be expanded. In
addition, such structures require sophisticated design, which
increases manufacturing expenses.
[0009] The stent delivery system 1 may not be optimal for
delivering and deploying drug coated stents. The stent 10 may
include drug coatings on the outer surface thereof. Drugs may be
coated on the stent 10 for various purposes. For example, drugs may
prevent the formation of scar tissue on the vessel walls or reduce
restenosis. Contrary to these benefits, some drug coatings may
cause unfavorable consequences if applied improperly. For example,
drugs, such as scar prevention drugs, may be highly incompatible
with blood. Thus, when drugs that are coated on the stent 10 come
into contact with blood, the drugs may cause problems such as blood
clots. For this reason, it is desirable that drugs are disposed
only on the outer surface of the stent 10. Because the outer
surface of the stent 10 is pressed against the vessel walls upon
expansion, blood does not flow between the outer surface of the
stent 10 and the vessel walls. However, the conventional stents 10
usually contain drug coatings on the sides and inner surfaces which
come into contact with the blood. Drug coating material is
typically sprayed on a stent 10 when it is in an expanded state.
Because the stent 10 is self-expandable, it is generally not
possible to spray the drug coating material on the compressed stent
10 since the outer surface of the stent 10 is constantly pressed
against the inner surface of a transfer tube or a sheath 8 when it
is compressed. When the drug coating material is sprayed on the
expanded stent 10, it easily covers the sides and inside surfaces
of the stent 10 through the openings between the struts of the
stent 10. Further, the stent has relatively large openings when it
is expanded. This reduces the efficiency of spraying because a
substantial amount of sprayed drugs passes through the
openings.
[0010] Even if drugs may be adequately sprayed on the expanded
stent 10, they may be lost in the course of manufacturing (e.g.,
loading into the delivery system) and the deployment processes of
the stent 10. The stent 10 must be compressed, for example, by
rolling it down to a smaller diameter. During this compression
process, shear force or mechanical trauma is applied to the stent
10 and a substantial amount of the drug coating may be lost.
Further, when the stent 10 is pushed into the sheath 8 and the
sheath 8 is later retracted rearward to deploy the stent 10, a
substantial portion of the drug coating may be lost. Accordingly,
there is a need for a stent delivery system that overcomes the
foregoing drawbacks.
SUMMARY
[0011] The invention provides a stent delivery system that
comprises at least one stent and a holder. The stent is expandable
from a compressed state to an expanded state. The holder interlocks
and interferes with the stent in the compressed state. An outer
diameter of the holder contacts an inner diameter of the stent. For
example, the holder may be blowmolded onto an inner surface of the
stent in the compressed state. Various other processes are possible
to interlock the stent with the holder. The stent delivery system
may or may not include sheath. In one embodiment, the sheath may
radially constrain the stent. In other embodiment, the sheathless
stent delivery system may include a stimulator configured to apply
a predetermined force to an inner surface of the holder.
[0012] In yet another embodiment, a stent delivery system includes
a holder having a pattern or impression. The pattern or impression
interlocks and interferes with the stent in the compressed state.
The pattern or impression may be formed by a blowmolding process.
The pattern or impression does not extend through the stent and
contacts side surfaces of the stent. Alternatively, or
additionally, the pattern or impression may extend through the
stent in the compressed state.
[0013] In yet another embodiment, a stent delivery system includes
at least one stent having a plurality of radial openings. The
radial openings are defined in part by side surfaces of the stent.
The stent delivery system further includes a holder having a
portion extended from an outer diameter of the holder. The portion
of the holder contacts the side surfaces of the stent. Accordingly,
the portion restricts longitudinal movement of the stent relative
to the holder. When an expansion force of the stent exceeds the
restraining force of the holder, the stent is expanded to the
expanded state. The stent delivery system further includes a sheath
radially constraining the stent. Alternatively, or additionally,
the stent delivery system includes no sheath. Instead of the
sheath, the portion of the holder further extends around a portion
of an outer diameter of the stent. Thus, the portion of the holder
may radially constrain the stent. This sheathless stent delivery
system further includes means for stimulating an inner surface of
the holder, thereby to release the stent from the holder. The stent
delivery system further includes a tip attached to the holder at
one end of the stent. The holder is made from one of polyethylene
terephathalate, crosslink nylon and irradiated polyethelene.
[0014] In yet another embodiment, a sheathless stent delivery
system includes at least one stent and a holder blowmolded onto an
inner surface of the stent in the compressed state. The stent
includes a plurality of struts interconnected with one another to
form multiple openings therebetween, and the holder includes a
plurality of extensions that extend through the multiple openings
of the stent. The holder wraps around a portion of an outer surface
of the stent, thereby to retain the stent in the compressed state.
The sheathless stent delivery system further includes a stimulator
adapted to apply a predetermined force to an inner surface of the
holder, thereby to release the stent from the holder. For example,
the stimulator includes a ball that has a diameter larger than an
inner diameter of the holder. The ball is attached to a wire that
extends through a hollow interior of the holder. The ball is
configured to stimulate the inner surface of the holder as the ball
is pulled rearward. The ball is made from a rigid material such as
steel. The sheathless system may have an outer diameter smaller
than about 0.0540 inch.
[0015] In yet another embodiment, a sheathless stent delivery
system includes a container positioned inside the holder and
storing a liquid supplied thereto. Preferably, the liquid may be
compatible with blood. The stent is released from the holder in
response to increased pressure of the container. For example, the
container may include an occluder.
[0016] In yet another embodiment, a stent delivery system includes
a holder and a plurality of stents longitudinally arranged one
after another. The plurality of stents are expandable from a
compressed state and an expanded state. The holder is blowmolded
onto an inner surface of stents in the compressed state. The
plurality of stents may be different in size, length and/or
flexibility. At least one of the plurality of stents may include a
drug coating.
[0017] In yet another embodiment, the invention provides a method
for deploying a stent disposed on a blowmolded holder. The method
includes delivering a stimulator attached to a wire to a
predetermined deployment site and delivering the compressed stent
and the holder to the deployment site by threading the wire through
an interior of the holder. The wire may extend from a proximal end
to a distal end. The method further includes stimulating an inner
surface of the holder by retracting the stimulator toward the
proximal end. A diameter of the stimulator is larger than an inner
diameter of the holder. The method also includes releasing the
stent from the holder, thereby to expand the stent to the expanded
state.
[0018] In yet another embodiment, a deploying method includes
delivering the compressed stent and the holder into a predetermined
deployment site and delivering a container into the deployment site
and positioning the container inside the holder. The deployment
method further includes supplying a quantity of liquid into the
container and stimulating an inner surface of the holder in
response to an increased pressure of the container. The increased
pressure is responsive to supply of the liquid. The method further
includes releasing the stent from the holder, thereby to expand the
stent to the expanded state.
[0019] In yet another embodiment, a deploying method includes (a)
delivering the plurality of stents in the compressed state and the
holder to a predetermined deployment site and (b) retracting the
sheath toward a proximal end to the extent that a first stent is
exposed wherein the first stent is disposed distally adjacent a
distal end. The method further includes (c) expanding the first
stent from the compressed state to the expanded state, (d)
retracting the sheath toward the proximal end to the extent that a
second stent is exposed wherein the second stent is disposed
proximally adjacent the first stent and (e) repeating the step of
(a)-(d) until remaining stents are expanded.
[0020] In yet another embodiment, a method for manufacturing a
stent delivery system is provided. The stent delivery system
includes compressing the stent to the first diameter, inserting the
stent into a first tube and placing a second tube inside the first
tube and inside an inner diameter of the stent. The second tube is
airtight. The manufacturing method further includes applying
pressure and heat suitable to the second tube, thereby to blowmold
the second tube against the stent. The method further includes
cooling down the first tube, the stent and the second tube without
any pressure. The method also includes inserting the stent and the
second tube into a sheath as the first tube is removed, and sealing
an end of the second tube during blowmolding and removing the seal
after the blowmolding.
[0021] The pressure may range between 30 psi and 90 psi. The heat
may range between 200.degree. F. and 280.degree. F. Specifically,
the pressure may range between 35 psi and 45 psi and the heat
ranges between 210.degree. F. and 220.degree. F. More specifically,
the pressure is about 40 psi and the heat ranges between
210.degree. F. and 220.degree. F. In other embodiment, the pressure
ranges between 85 psi and 95 psi and the heat ranges between
230.degree. F. and 280.degree. F. More specifically, the pressure
is about 90 psi and the heat is about 250.degree. F.
[0022] In yet another embodiment, a method for manufacturing a
sheathless stent delivery system is provided. The method includes
compressing the stent from an expanded state to a compressed state,
blowmolding the holder against the stent by applying suitable heat
and pressure, and applying a drug coating material on an outer
surface of the stent in the compressed state. The drug coating
material does not cover an inner surface and side surfaces of the
stent. The step of applying the drug coating material includes
spraying the drug coating material.
[0023] The invention provides a stent delivery system having a low
profile. The stent delivery system also minimizes damage to blood
vessels and properly deploys long stents. The stent delivery system
further addresses specific needs of deployment sites, such as blood
vessels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention can be better understood with reference to the
following drawings and description. The components in the figures
are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Moreover, in the
figures, like referenced numerals designate corresponding parts
throughout the different views.
[0025] FIGS. 1A and 1B depict a conventional stent delivery
system.
[0026] FIG. 2 depicts a first embodiment of a stent delivery
system.
[0027] FIG. 3 illustrates one embodiment of a method for
manufacturing the stent delivery system of FIG. 2.
[0028] FIG. 4 illustrates one embodiment of a method for deploying
the stent delivery system of FIG. 2.
[0029] FIG. 5 depicts a second embodiment of a stent delivery
system.
[0030] FIG. 6 depicts a third embodiment of a stent delivery
system.
[0031] FIG. 7A illustrates one embodiment of a method for deploying
the stent delivery system of FIG. 5.
[0032] FIG. 7B illustrates another embodiment of the method for
deploying the stent delivery system of FIG. 6.
[0033] FIG. 8 depicts an exemplary drug coating process.
[0034] FIG. 9 depicts an enlarged view of a portion of the stent
delivery system of FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] FIG. 2 shows a first embodiment of a stent delivery system
according to the invention. The stent delivery system 100 includes
a first stent 106, a second stent 108, a sheath 110 and a holder
104. At a distal end of the first stent 106, a distal tip 102 is
coupled to the holder 104. In FIG. 2, two stents 106 and 108 are
delivered by the stent delivery system 100, but delivery of more or
less stents is possible. The first stent 106 and the second stent
108 are self-expandable stents, respectively, and expand from a
compressed state to an expanded state. The stents 106, 108 have a
plurality of radial openings and the radial openings are defined in
part by side surfaces of the stents 106, 108. The sheath 110
radially constrains the stents 106, 108 to keep the compressed
state. The holder 104 interlocks and interferes with the inner
surfaces of the stents 106, 108. Specifically, the holder 104 has a
portion extended from its outer diameter and that portion contacts
the side surfaces of the stents 106, 108.
[0036] For interlocking and interference, the holder 104 has a
first pattern or impression as shown in FIG. 2. The stents 106, 108
may be press-fit or friction-fit into the first pattern of the
holder. This first pattern or impression of the holder 104 does not
extend through the radial openings of the stents 106, 108. Rather,
it contacts the side surfaces of the stents 106, 108. To form the
first pattern or impression, the holder 104 may be blowmolded. The
manufacturing of the holder 104 is not limited to the blowmolding
process and various processes are possible. For instance, processes
such as casting, injection molding, milling, etching, lithography,
electrical discharge machining and laser machining may be used.
[0037] When the first pattern or impression of the holder 104
|.sub.[s1]is formed by using the blowmolding process, the holder
104 may precisely conform to inner diameters of the stents 106,
108, as will be described below. A self-expandable stent such as
the stents 106, 108 is typically compressed to have a predetermined
compressed diameter, regardless of types or sizes of the stents.
Although the first stent 106 and the second stent 108 have
different diameters upon expansion, they may be compressed to have
the same diameter. Accordingly, the holder 104 may support the
compressed stents 106, 108, although the stents 106, 108 may be of
different types and have different lengths and/or diameters. The
tip 102 may be bonded to the holder 104. The distal tip 102 may
facilitate navigation of tortuous arteries and vessels during the
delivery of the stents 106, 108.
[0038] The stent delivery system 100 is manufactured as shown in
FIG. 3. The self-expandable stents 106 and 108 are compressed for
delivery at block 310. For example, the stents 106 and 108 may be
mechanically rolled down to be compressed. Alternatively, or
additionally, other known compression methods may be used.
Subsequently, the compressed stents 106, 108 are slid into a first
tube (block 320). The first tube may be made from any material that
has a higher plastically melting threshold than blowmoldable
materials. For example, the first tube may be made from steel. The
first tube is also made from polytetrafluoroethylene ("PTFE"). PTFE
is radially flexible and longitudinally stiff, and therefore, it is
frequently used to form a tube that is used for manufacturing stent
delivery systems. At the next block 330, a second tube is inserted
into the first tube and inside the inner diameters of the stents
106, 108. The second tube may be made from any material that is
capable of being blowmolded. For example, polyethylene
terephthalate ("PET"), crosslink nylon or irradiated polyethylene
may be used to form the second tube. The second tube may have a
thick wall and is small enough in diameter to fit inside of the
stents 106, 108. The second tube is a pre-form of a final
structure, so that it has a substantially similar shape as that of
the final structure. By way of example, the second tube may have an
outer diameter, 0.050.+-.0.001 inch and an inner diameter,
0.021.+-.0.001 inch. Alternatively, or additionally, the second
tube may be thin. The thin second tube may be, in particular,
suitable for a stent with a high radial force.
[0039] As a process of manufacturing the holder 104, a blowmolding
process is described in detail. However, various other processes
are available. After the second tube is inserted, it is sealed at
the end so that it is airtight (block 340). Next, heat and pressure
suitable for blowmolding is applied to the second tube (block 350).
For example, heating temperature ranges may be between 200.degree.
F. to 240.degree. F. More specifically, the heating temperature may
range from 210.degree. F. to 220.degree. F. Air pressure ranges
between 35 psi and 45 psi, and more preferably, may be about 40
psi. Under the heat and pressure, the second tube is blown out and
is molded to the inner surface of the stents 106, 108. The stents
106, 108 include multiple struts that are made from shape memory or
spring metal which are interconnected with one another. A plurality
of radial openings are formed between the struts and defined in
part by side surfaces of the stents 106, 108. The struts and the
radial openings may form the inner surface of the stents 106, 108.
The second tube is molded to the struts of the stents 106, 108 and
is tightly fitted into the inner diameter of the stents 106, 108.
As previously described, the inner diameter of the second tube
before the blowmolding may be 0.021.+-.0.001. However, after the
blowmolding, the inner diameter of the second tube may be enlarged
to have a diameter of about 0.035 to 0.040 inch. The blowmolding
process may take a few seconds. For example, it may take about 12
seconds. As a final step (block 360), the first tube, the stents
106, 108 and the second tube are cooled down. While the first tube,
the stents 106, 108 and the second tube are exposed to heating and
pressure for the blowmolding process, the second tube and the
stents 106, 108 push against the first tube. The first tube may be
separated from the second tube and the stent by cooling it down.
The cooling down process may take a few seconds, for example, 5-10
seconds.
[0040] After the cooling down process, the stents 106, 108 and the
holder may be released from the first tube. The stents 106, 108 and
the holder 104 are then slid into the sheath 110 and at the same
time, the first tube is removed by pulling it off the stents 106,
108 (at block 370). The tip 102 may be coupled to the holder 104 at
the distal end. Alternatively, or additionally, the tip 102 may be
coupled to the holder 104 before the holder 104 is slid into the
sheath 110. The stent delivery system 100 is completed and mounted
on one end of a delivery catheter for delivery and deployment of
the stents 106, 108. The delivery catheter may have the structure
similar to the delivery catheter 50 as shown in FIGS. 1A and
1B.
[0041] Referring to FIG. 4, delivery and deployment of the stents
106, 108 are described. To deliver the stents 106, 108, the
Seldinger techniques may be used at block 430. The Seldinger
techniques may involve a needle, a guidewire and a dilator. The
stent delivery system 100 is introduced through the dilator and
removed therefrom later. When the stent delivery system 100 arrives
at the desired deployment site, a physician starts retracting the
sheath 110 rearward, i.e., toward the proximal end (block 440). As
the sheath 110 is retracted, the first stent 106 becomes exposed
and is released. The stent 106 maintains its compressed state until
the sheath 110 is sufficiently retracted (block 450). Because the
holder 104 is molded to the first stent 106, the holder temporarily
restrains a longitudinal movement of the first stent 106.
Consequently, abrupt movement of the first stent 106 upon
retraction of the sheath 110 is restrained by the holder 104, which
allows the physician some time to retract the sheath 110 without
being concerned about the abrupt movement of the first stent 106
(block 450). When expansion force of the first stent 106 exceeds
the restraining force of the holder 104, the first stent 106 starts
to expand. The sheath 110 is then retracted further to expose the
second stent 108 at block 460. The second stent 108 is deployed in
the same manner as the first stent 106 in block 470. After the
stents 106, 108 are fully expanded, the holder 104 is removed from
the deployment site at block 480.
[0042] Although FIGS. 2-4 illustrate delivery and deployment of the
two stents 106 and 108, it is possible to deploy a single long
stent or multiple stents with the stent delivery system 100. Where
multiple stents are deployed, each stent may have different
diameters, special coatings, radial forces and/or flexibility
characteristics or combinations thereof. Where an artery is curved
or has nonuniform diameters along the length, implanting multiple
stents having different diameters and lengths may optimize the
treatment of such an artery. For example, if a certain vessel has
different diameters along its length, stents corresponding to the
different diameters of the vessel may be arranged and deployed in
the vessel. Further, if a portion of the vessel needs a certain
treatment, a stent to be deployed in that portion may include
effective drug coatings. Multiple stents may be arranged to address
different needs of various deployment sites. This results in
optimized stenting that is specifically tailored to the needs of
deployment sites. Furthermore, where a single, long stent is
deployed, the holder 104 uniformly restrains the long stent along
the longitudinal direction as a result of the blowmolding. Thus,
the pressure is evenly distributed along the length of the long
stent and does not concentrate on the distal end of the long stent.
Accordingly, proper and accurate deployment of the long stents is
possible. The stent delivery system 100 also substantially reduces
the waste associated with the complicated and costly manufacturing
processes of long stents.
[0043] FIG. 5 shows a second embodiment of a stent delivery system.
Unlike the first embodiment, the stent delivery system 500 is a
sheathless stent delivery system. The stent delivery system 500 has
no sheath such as the sheath 110. Two stents 106, 108 are delivered
by the stent delivery system 500, but more or less stents may be
delivered. A holder 502 has a second pattern or impression that
extends through the openings of the stents 106, 108, which are
formed by multiple struts. The height of the extensions 507 that
extend through the openings is adjustable by changing the heat
and/or pressure that is applied during the blowmolding process, as
will be described in detail below. The second pattern or impression
is different from the first pattern or impression shown in FIG. 2
in that the second pattern or impression extends through the
opening of the stents 106, 108. The first pattern or impression
interlocks or interferes with the stents 106, 108, but it does not
extend further. The first pattern may contact side surfaces of the
stents 106, 108. To the contrary, the second pattern or impression
may partially radially wrap around the stents 106, 108 and press
over edges of the stents 106, 108. A tip such as the tip 102 in
FIG. 1 may be attached to the holder 502.
[0044] The stent delivery system 500 further includes a stimulator
such as a ball 504 attached to a wire 506. The wire 506 passes
through the center of the stent delivery system 500 as shown in
FIG. 5. The ball 504 may be made from any material that is rigid
such as steel. The ball 504 may be solid and has a throughhole
inside. Alternatively, the ball 504 may be hollow inside. The ball
504 has a diameter that is about the same as the inner diameter of
the stents 106, 108 but is not smaller than the inner diameter of
the holder 502. In this embodiment, the ball 504 is used as a
stimulator, but various other structures are possible. As long as
the structure has a diameter that is not smaller than the inner
diameter of the holder 502, the shape of such structure is not
limited to a ball shape. The ball 504 provides appropriate
pressure, stimuli or force to the holder 502. Because the holder
502 extends radially through the stents 106, 108, and more
specifically, through the radial openings of the stents 106, 108,
it securely restrains the stents 106, 108 from expanding.
Accordingly, apart from the nature of the stents 106, 108, i.e.,
the tendency to expand, a separate force and/or pressure is
required to release the stents 106, 108 from the holder 502. As the
ball 504 passes through the interior of the holder 502 by pulling
back on the wire 506, it continuously stimulates the inner walls of
the holder 502.
[0045] Alternatively, or additionally, the ball 504 may take the
ball 504 in and pushed through the interior of the holder 502. The
stent delivery system 500 is already disposed within the blood
vessel. The ball 504 attached to the wire 506 may be moved to the
blood vessel and pushed through the interior of the holder 502.
[0046] The requisite force may differ depending on the flexibility
of the holder 502. If the holder 502 is very flexible, a minimum
amount of pressure allows the stents 106, 108 to be released from
the holder 502. If the holder 502 is more or less rigid, a
relatively high pressure may be required. The ball 504 may touch,
strike and/or interfere with the inner surface of the holder
502.
[0047] The manufacturing process of the stent delivery system 500
is in many ways similar to that of the stent delivery system 100.
The stents 106, 108 are compressed and inserted into the first tube
made from, for example, PTFE. Then, the second tube which will
become the holder 502 is inserted into the first tube and inside
the inner diameters of stents 106, 108. The end of the second tube
is sealed so that it is airtight, and the second tube is blowmolded
to the stents 106, 108 by applying appropriate heat and pressure.
As noted above, the holder 502 may be formed with various other
processes. Unlike the stent delivery system 100, the stent delivery
system 500 typically requires higher pressure and heat than the
stent delivery system 100. This is because some portions of the
holder 502 are forced to extend through the openings in the stents
106, 108. For example, pressure applied to the stent delivery
system during blowmolding ranges from about 85 psi to 95 psi. More
preferably, pressure may be about 90 psi. Heating temperature
ranges between 230.degree. F. and 280.degree. F., and more
preferably, is about 250.degree. F. By adjusting the pressure,
temperature or the combination thereof, it is possible to control
how far the holder 502 extends radially through the stents 106,
108.
[0048] The manufacturing process further allows the stent delivery
system 500 to have a compact and tight design. A stent is subject
to an electropolishing process that rounds corners off. However,
some residual corners may be present even after the
electropolishing process. The holder 502 wraps around edges and/or
corners of the stents 106, 108, and therefore, the stent delivery
system 500 may not interfere with even a small, tortuous blood
vessel during the delivery. Further, by radially pressing the
stents 106, 108 with the holder 502, the stent delivery system 500
may have a tighter, compact and low profile.
[0049] The ball 504 and the wire 506 may be manufactured separately
from the stent delivery system 500. The ball 504 is solid and has a
main throughhole. The wire 506 may be connected through the main
throughhole. The wire 506 may be a guidewire and no additional wire
may be required. Alternatively, or additionally, the ball 504 may
be hollow and the wire 506 is soldered to the end of the ball 504
as shown in FIG. 3. The ball 504 may be attached to a distal end of
a guidewire.
[0050] Once the stent delivery system 500 is manufactured, the
stents 106, 108 are delivered and deployed. Referring to FIG. 7A,
operations of the stent delivery system 500 are described. FIG. 7A
illustrates one embodiment of a method for deploying the stents
106, 108 using the stent delivery system 500. The method
illustrated in FIG. 7A uses the Seldinger techniques at block 720.
The ball 504 and the wire 506 may be used to deploy the stents 106,
108. In this case, the ball 504 bonded to the wire 506 is inserted
into a predetermined deployment site, for example, a blood vessel.
In this embodiment, a guidewire may not be used. Alternatively, or
additionally, it is possible to thread the ball 504 over a
guidewire and insert it into the deployment site. In other
embodiment, the ball 504 may be taken in and pushed through the
blood vessel. Physicians may choose whether the ball 504 is
introduced prior to or after the introduction of the stent delivery
system 500, depending on their preferences, deployment sites, or
many other factors.
[0051] The stent delivery system 500 is mounted on one end of a
delivery catheter. The delivery catheter is inserted over the wire
506 until the stents 106, 108 arrive at the deployment site (block
730). Because a sheath is not a part of the stent delivery system
500, there is no retraction of a sheath. Instead, the ball 504 is
pulled back to apply appropriate force to the holder 502. The ball
504 is retracted rearward by pulling the wire 506 (block 740).
Alternatively, or additionally, the ball 506 may be taken in and
pushed through. Due to the movement of the ball 504, the inner
surface of the holder 502 is stimulated and the stents 106, 108 are
released from the holder 506 (block 750). Once released from the
holder 502, the stents 106, 108 start to expand at block 760. After
the stents 106, 108 are expanded, the holder 502 is removed from
the blood vessel, leaving the stents 106, 108 (block 780).
[0052] FIG. 6 is a third embodiment of a stent delivery system. A
stent delivery system 600 includes the stents 106, 108 and the
blowmolded holder 502 having the extensions 507 like the stent
delivery system 500. However, instead of the ball 504, the stent
delivery system 600 further includes a container device 610. In the
stent delivery system 600, a certain type of liquid, which is
preferably compatible with blood, may be used to provide pressure
to the holder 502. Such liquid may be, for example, saline or
carbon dioxide. To supply the liquid, a syringe (not shown) may be
connected to a delivery catheter and introduce the liquid into the
delivery catheter. Alternatively, handle-turned or knob-turned
pressure devices may introduce the liquid into the delivery
catheter. The container device 610 may be an artery or vessel
occluder. The container device 610 may be required to be disposed
inside the holder 502. The container device 610 may block the
liquid from flowing into a blood vessel. As the liquid flows into
the container device 610, pressure builds up inside the container
device as indicated by small arrows in FIG. 6. This built-up
pressure provides pressure or stimuli on the inner surface of the
holder 502 and makes the holder 502 release the stents 106,
108.
[0053] FIG. 7B illustrates another embodiment of a method for
deploying stents 106, 108 by using the sheathless stent delivery
system 600. In particular, as a stimulator, a certain type of
liquid is used to stimulate the inner surface of the holder 502. At
block 722, the stent delivery system 600 may be introduced using
the Seldinger techniques to a deployment site. The stent delivery
system 500 is delivered through a delivery catheter (block 732).
After the stent delivery system 500 is delivered to the deployment
site, the container device 610 is inserted over the guidewire and
positioned inside of the inner surface of the holder 742 at block
742. Alternatively, or additionally, the container device 610 may
be inserted before the stent delivery system 500 is delivered. When
the container device 610 is placed properly, a certain type of
liquid is provided through the delivery catheter to the container
device at block 752. Due to the flow of the liquid, the inner
pressure of the container device 610 increases and stimulates the
inner surface of the holder 502 at block 752. This stimuli, force
or pressure by the container device onto the inner surface of the
holder 502 makes it possible for the stents 106, 108 to be released
from the holder 502 at block 762. As a result, the stents 106, 108
expand and the holder 502 is removed from the deployment site
(block 782).
[0054] As previously stated, the stent delivery system 500 and 600
do not need a sheath, and therefore, has a lower profile. The stent
delivery system 500, 600 have a substantially reduced outer
diameter, for example, 0.040.about.0.060 inches due to absence of a
sheath. Specifically, the stent delivery system 500, 600 may have
an outer diameter smaller than 0.054 inch. Accordingly, damage to
blood vessels which may arise during conventional stenting process
may be substantially reduced and manufacturing labor and costs may
also be minimized. Furthermore, the stent delivery system 500, 600
provide the same advantages that are provided by the stent delivery
system 100.
[0055] Another advantage is that the stent delivery system 500, 600
are suitable for delivery and deployment of drug coated stents.
FIG. 8 shows one embodiment of a drug coating process for the
sheathless stent delivery systems 500, 600. As shown in FIGS. 5 and
6, the sheathless stent delivery systems 500, 600 include the
compressed stents 106, 108 and the blowmolded holder 502. The
blowmolded holder 502 radially wraps around the stents 106, 108.
More specifically, the extensions 507 of the holder 502 securely
retain the stents 106, 108. Drug coating material may be applied to
the outer surfaces of the compressed stents 106, 108 as shown in
FIG. 8. For example, the drug coating material may be sprayed on
the compressed stents 106, 108. Alternatively, drug coating
materials may be sprayed on the expanded stents 106, 108 if
necessary. In other embodiments, only one stent 106 or 108 may be
sprayed.
[0056] Drug coating materials may include a drug only, a drug mixed
with a polymer, or any type of a drug carrier or binder carrying a
drug. The drug coating material may have multiple layers including
one layer of a drug or one layer of a polymer. The drug carrier or
binder may be disposed underneath or on the top of the drug layer.
Drugs coated on the stents 106, 108 may include drugs that prevent
scar formation, restenosis, etc. These drug coatings may or may not
be compatible with blood. For example, drugs for prevention of scar
formation may not be compatible with blood. By way of example, drug
coating materials may include drugs such as Batimastat,
Angiopeptin, ABT 578, Dexamethasone, 17 beta estradiol, Paclitaxel,
Myfortic, Endothelial progenitor cells (EPC), surface antibodies,
Pimecrolimus, Absorbable MG-alloy, QP-2 Paclitaxel derivative,
Everolimus, Sirolimus, Biolimus A7 Biolimus A9, Viral proteins,
Actinomycin D, Tranilast, Rapamune, Tacrolimus, C-myc,
Cyclosporine, EQs, CD-34 antibody, and/or Tacrolimus. Detailed
descriptions on drug coating materials may be found in U.S. Pat.
Nos. 5,380,299; 5,609,629; 5,824,049; 5,873,904; 6,096,070;
6,299,604; 6,530,951; 6,730,064; 6,774,278 and U.S. Patent
Publication Nos. 2003/28243; 2003/28244; 2003/36794 and 2004/47909,
which are incorporated herein by reference.
[0057] As shown in FIG. 8, the blowmolded holder 502 tightly wraps
around the inside of the stents 106, 108. Specifically, the holder
502 has a portion extended from an outer diameter thereof, i.e.,
the extensions 507. The extensions contact the side surfaces of the
stents 106, 108 such as side surfaces 910 shown in FIG. 9 and
restrict longitudinal movement of the stents 106, 108 relative to
the holder 502. Further, the extensions 507 of the holder 502
extend around a portion of an outer diameter of the stents 106, 108
and radially constrain the stents 106, 108. As a result, no sheath
is required for delivery and deployment of the stents 106, 108.
Without a sheath, the stents 106, 108 remain compressed and are
able to be deployed. Sprayed drug coatings may be applied only on
the outer surface of the stents 106, 108. Because the outer
surfaces of the stents 106, 108 are pressed against vessel walls,
blood does not flow between the outer surfaces of the stents 106,
108 and the vessel walls. FIG. 9 depicts an enlarged view of a
portion of the stent delivery system 500, 600. The stents 106, 108
include the side surfaces 910 disposed at its radial openings. The
radial openings are defined in part by the side surfaces. The
stents 106, 108 also have inner surfaces 920. The drug coating
material may be precisely sprayed on the outer surfaces of the
stents 106, 108 and does not spread to the sides 910 and/or inside
surfaces 920 of the stents 106, 108. Unlike the outer surface, the
sides 910 and/or inside surfaces 920, 930 of the stents 106, 108
may contact blood. Therefore, even if the drug coatings are
incompatible with blood, no restenosis, blood clots or related
problems occur because the drugs do not reside on the sides 910
and/or the inside surfaces 920, 930 of the stents 106, 108.
Further, because the drug coatings may be sprayed on the compressed
stents 106, 108, loss of the drug coatings through large openings
of the expanded stents 106, 108 and compression processes of the
stents 106,108 may be substantially minimized. In addition, the
drug coatings are not lost due to a sheath since the stent delivery
system 500 is sheathless.
[0058] The advantages of the effective drug coatings may be
achieved regardless the holder 502. The holder 502 may be made from
materials that have high or low surface tensions. Upon application
of the drug coatings, the holder 502 with high surface tension may
keep drug coatings thereon and loss of the drug coatings may be
minimized. Alternatively, the holder 502 with low surface tension
may not keep the drug coatings thereon. Instead, the drug coatings
may flow onto the stents 106, 108 interfered with the holder 502.
Loss of the drug coatings may be again reduced.
[0059] Although various embodiments have been described in
connection with a stent delivery system, the invention is not
limited to the described embodiment of the stent delivery system.
The invention may be applicable to other medical systems or methods
that involve implantation of a device or structure like a stent.
The application of the invention may be more useful if the device
or structure has characteristics of self-expansion.
[0060] While various embodiments of the invention have been
described, it will be apparent to those of ordinary skill in the
art that many more embodiments and implementations are possible
within the scope of the invention. Accordingly, the invention is
not to be restricted except in light of the attached claims and
their equivalents.
* * * * *