U.S. patent application number 11/109604 was filed with the patent office on 2005-08-25 for method of recapturing a stent.
This patent application is currently assigned to Bard Peripheral Vascular, Inc.. Invention is credited to Edwin, Tarun J..
Application Number | 20050187612 11/109604 |
Document ID | / |
Family ID | 26802921 |
Filed Date | 2005-08-25 |
United States Patent
Application |
20050187612 |
Kind Code |
A1 |
Edwin, Tarun J. |
August 25, 2005 |
Method of recapturing a stent
Abstract
A method to retrieve a deployed stent in a blood vessel. In one
embodiment, the method includes the introduction of a retrieval
stent within the lumen of the deployed stent, enlarging the
retrieval stent to contact a surface of the deployed stent and
contracting the retrieval stent which in turn causes the deployed
stent to contract for removal from the blood vessel. The retrieval
stent may contain one or more fluid passageways through which
heated or cooled fluid can circulate and may be connected to a
catheter for circulation of the fluid. Fluid flow may be regulated
by a valve or valve assembly incorporated in the stent and/or the
catheter.
Inventors: |
Edwin, Tarun J.; (Chandler,
AZ) |
Correspondence
Address: |
MORRISON & FOERSTER, LLP
555 WEST FIFTH STREET
SUITE 3500
LOS ANGELES
CA
90013-1024
US
|
Assignee: |
Bard Peripheral Vascular,
Inc.
|
Family ID: |
26802921 |
Appl. No.: |
11/109604 |
Filed: |
April 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11109604 |
Apr 19, 2005 |
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10638182 |
Aug 8, 2003 |
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6881220 |
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10638182 |
Aug 8, 2003 |
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09975743 |
Oct 11, 2001 |
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6623519 |
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09975743 |
Oct 11, 2001 |
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09321496 |
May 27, 1999 |
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6358276 |
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60105768 |
Sep 30, 1998 |
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Current U.S.
Class: |
623/1.19 ;
606/108 |
Current CPC
Class: |
A61F 2210/0042 20130101;
A61F 2/82 20130101; A61F 2250/0067 20130101; A61F 2/88
20130101 |
Class at
Publication: |
623/001.19 ;
606/108 |
International
Class: |
A61F 002/06 |
Claims
What is claimed as new and desired to be protected by Letters
Patent of the United States is:
1. A method of retrieving a stent, comprising: positioning a
portion of a first stent within a lumen of a second stent residing
at a first location in a blood vessel; contacting a surface of the
second stent with the first stent; and translating the first and
second stents away from the first location.
2. The method according to claim 1, wherein the first stent is
comprised of a shape-memory material and the contacting step
comprises the step of expanding the first stent from a contracted
diameter to an expanded diameter by circulating heated fluid
through a fluid flow conduit of the first stent, the method further
comprising the step of contracting the first and second stents
concomitantly by delivering a cryogenic fluid to the first
stent.
3. The method according to claim 1, wherein the first stent is
connected to a catheter comprising a valve for controlling fluid
flow to and from the first stent, the contacting step comprising
the step of delivering fluid through the catheter and valve to the
first stent to expand the first stent.
4. The method according to claim 3, wherein the first stent
comprises a single fluid pathway having a first end and a second
end in fluid communication respectively with a first and second
lumen of the catheter, the delivering step comprising circulating
fluid through the first stent by delivering fluid from the catheter
first lumen to the first end of the first stent and from the second
end of the first stent to the catheter second lumen.
5. The method according to claim 3, wherein the first stent
comprises a first and second fluid pathway in fluid communication
respectively with a first and second lumen of the catheter, the
delivering step comprising circulating fluid through the first
stent by delivering fluid from the catheter first lumen to the
first fluid pathway of the first stent and from the second fluid
pathway of the first stent to the catheter second lumen.
6. The method according to claim 5, wherein the first and second
fluid pathways are connected at a distal end of the first stent,
the circulating step comprising fluid from the first fluid pathway
entering the second fluid pathway at the distal end of the first
stent.
7. The method according to claim 1, wherein the first stent is
connected to a catheter comprising a valve assembly for delivering
fluid to and from the first stent, the valve assembly comprising a
first and second hollow member configured for insertion through a
diaphragm of the first stent, the first and second hollow member
being in fluid communication with a first and second lumen of the
catheter, the contacting step comprising the step of delivering
fluid through the first lumen of the catheter and the first hollow
member to the first stent to expand the first stent.
8. The method according to claim 7, wherein the delivering step
further comprises removing fluid from the first stent through the
second hollow member and through the second lumen of the
catheter.
9. The method according to claim 1, wherein the first and second
stents are comprised of a shape memory material, further comprising
the step of collapsing the first and second stents concomitantly,
following the contacting step.
10. The method according to claim 9, wherein the first and second
stents are comprised of a shape memory metal, wherein the
collapsing step comprises the step of introducing a cryogenic fluid
into the first stent.
11. The method according to claim 10, wherein the first stent is
connected to a catheter comprising a valve for controlling fluid
flow to and from the first stent, the contacting step comprising
the step of delivering fluid through the catheter and valve to the
first stent to expand the first stent.
12. The method according to claim 11, wherein the first stent
comprises a single fluid pathway having a first end and a second
end in fluid communication respectively with a first and second
lumen of the catheter, the delivering step comprising circulating
fluid through the first stent by delivering fluid from the catheter
first lumen to the first end of the first stent and from the second
end of the first stent to the catheter second lumen.
13. The method according to claim 11, wherein the first stent
comprises a first and second fluid pathway in fluid communication
respectively with a first and second lumen of the catheter, the
delivering step comprising circulating fluid through the first
stent by delivering fluid from the catheter first lumen to the
first fluid pathway of the first stent and from the second fluid
pathway of the first stent to the catheter second lumen.
14. The method according to claim 13, wherein the first and second
fluid pathways are connected at a distal end of the first stent,
the circulating step comprising fluid from the first fluid pathway
entering the second fluid pathway at the distal end of the first
stent.
15. The method according to claim 9, wherein the first stent is
connected to a catheter comprising a valve assembly for delivering
fluid to and from the first stent, the valve assembly comprising a
first and second hollow member configured for insertion through a
diaphragm of the first stent, the first and second hollow member
being in fluid communication with a first and second lumen of the
catheter, the contacting step comprising the step of delivering
fluid through the first lumen of the catheter and the first hollow
member to the first stent to expand the first stent.
16. The method according to claim 15, wherein the delivering step
further comprises removing fluid from the first stent through the
second hollow member and through the second lumen of the
catheter.
17. The method according to claim 1, wherein the contacting step
comprises expanding the first stent from a contracted diameter to
an expanded diameter by heating the first stent, the method further
comprising the step of contracting the first and second stents
concomitantly to a diameter smaller than the expanded diameter by
cooling the first stent.
18. A method of retrieving a stent, comprising: positioning a
portion of a first shape memory stent attached to a catheter within
a lumen of a second shape memory stent deployed in a blood vessel;
delivering heated fluid from the catheter to the first stent to
cause the first stent to expand from a contracted diameter to an
expanded diameter, a surface of the first stent contacting a
surface of the second stent; introducing a cryogenic fluid into the
first stent to cause the first and second stents to contract to a
removal diameter; and removing the first and second stents from the
blood vessel.
19. A stent comprising a non-inflatable non-porous tubing,
including at least one fluid flow conduit therein, the tubing being
circumferentially arranged to form a side wall of the stent,
thereby creating a main lumen of the stent through which blood can
flow.
20. The stent according to claim 19, wherein the stent is comprised
of a shape memory material.
21. The stent according to claim 20, wherein the shape memory
material comprises a metal.
22. The stent according to claim 20, wherein the shape memory
material comprises a plastic.
23. The stent according to claim 19, further comprising: a
removable catheter including a proximal end that remains outside of
a patient's body and a distal end that is capable of sealing
attachment to the stent for fluid delivery to the stent; and a
valve for controlling the flow of fluid in the system.
24. The stent according to claim 23, wherein the valve comprises a
back flow preventer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/638,182, filed Aug. 7, 2003, now U.S. Pat. No. 6,881,220, which
is a division of application Ser. No. 09/975,743, filed Oct. 11,
2001, now U.S. Pat. No. 6,623,519, which is a division of
application Ser. No. 09/321,496, filed May 27, 1999, now U.S. Pat.
No. 6,358,276, which claims the benefit of U.S. Provisional
Application No. 60/105,768, filed Sep. 30, 1998. This application
expressly incorporates by reference the entirety of each of the
above-mentioned applications as if fully set forth herein.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A COMPACT DISK APPENDIX
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] The present invention relates generally to endoluminal
devices, and more particularly to stents.
[0005] Stents and similar endoluminal devices have been used to
expand a constricted vessel to maintain an open passageway through
the vessel in many medical situations, for example, following
angioplasty of a coronary artery. In these situations, stents are
useful to prevent restenosis of the dilated vessel through
proliferation of vascular tissues. Stents can also be used to
reinforce collapsing structures in the respiratory system, the
reproductive system, biliary ducts or any tubular body lumens.
Whereas in vascular applications fatty deposits or "plaque"
frequently cause the stenosis, in many other body lumens the
narrowing or closing may be caused by malignant tissue.
[0006] Fluids have traditionally been used to pressurize the
angioplasty balloons used to open restricted vessels. The balloons
may have a variety of shapes including a coiled form. In such a
device fluid is injected into the balloon to inflate the device and
maintain turgidity. Shturman (U.S. Pat. No. 5,181,911) discloses a
perfusion balloon catheter wound into a helically coiled shape with
one end attached to a fitting and the other to a syringe for
inflating the balloon with fluid. When the balloon is inflated, its
coiled form allows blood flow thorough the open center of the
structure. At the same time it is possible to actually have fluid
flow within the balloon structure so that the syringe can deliver
fluid into the balloon, fluid can flow through the balloon, and
fluid can then exit through a second lumen in a catheter attached
to the syringe.
[0007] Coiled stents that are connected to a catheter apparatus, as
in Wang et al. (U.S. Pat. No. 5,795,318), are used for temporary
insertion into a patient. Wang et al. discloses a coiled stent of
shape-memory thermoplastic tube that can be converted from a
relatively narrow diameter to a larger coiled form by heating. The
narrow diameter coil is mounted at the end of a catheter over a
balloon and in a preferred embodiment a resistive heating element
runs down the length of the thermoplastic element. An electric
current is applied to heat the element thereby softening it while
the balloon is expanded to enlarge the diameter of the coil. Upon
cooling the enlarged coil hardens and the balloon is withdrawn.
After the temporary stent has performed its duty, it is again
heated and removed while in the softened state. In one embodiment
the thermoplastic tube is supplied with an additional lumen so that
liquid drugs can flow into the stent and delivered through
apertures or semi-permeable regions.
[0008] The attempt to kill or prevent proliferation cells is a
common theme in clinical practice. This is generally true in
vascular and non-vascular lumens. It is known that ionizing
radiation can prevent restenosis and malignant growth. Although the
effect of temperature extremes, e.g., cryogenic (cold) or hot
temperatures, on cellular activity is not as well researched, it
may provide a safer approach to control of tissue proliferation.
Among the drawbacks of the prior art coiled balloons is that the
balloon material is relatively weak so that expansion and
contraction cause the balloon to fail. Failure of a balloon
containing radioactive or cryogenic fluids could be catastrophic.
It would be desirable to provide a catheter based, minimally
invasive device for stenting support that could deliver hot or
cryogenic or radioactive fluids or drugs and that would be sturdy
and could remain in the body for extended periods of time, detached
from the insertion device.
BRIEF SUMMARY OF THE INVENTION
[0009] In its simplest embodiment the present invention is an
endoluminal coil stent comprising a hollow tube formed into a
series of loops or other known stent shapes which initially has a
low profile and diameter. This structure can be delivered into a
patient's vascular system and expanded to full size. The present
invention to provides a stent that is hollow allowing the passage
of fluid. The stent has either one or a plurality of passageways
for fluid flow. The stent is attached to a catheter via a special
fitting so that when engaged with the catheter, fluid flows freely
from the catheter to the stent with a possible return circuit
through the catheter. When disengaged, the fitting prevents leakage
from the stent permitting the stent to remain in place in a
patient's vasculature.
[0010] This invention provides a way of treating vascular areas
affected with malignant growths or experiencing restenosis from
smooth muscle cell proliferation, etc. The stent is inserted in a
small diameter configuration and after being enlarged to a larger
diameter, acts as a support device for the areas of restenosis or
malignant growth. In addition, the stent can treat these affected
areas in a unique way by flowing radioactive, heated or cryogenic
fluids through the stent.
[0011] The present invention also provides a way of delivering
drugs to an affected site. A stent to accomplish this purpose can
be composed of several different materials. For example, the stent
can formed from a metal or other material with small pores machined
or otherwise formed (e.g., with a laser). When such a stent is
filed with a drug, that drug slowly disperses through the pores.
Alternatively, an entire metal tube or portions of the tube could
be formed e.g., from sintered metal powder thereby forming a porous
structure for drug delivery. Another embodiment would alternate a
metal tube (for structural stability) with dispensing segments
inserted at various intervals. The segments would be perforated to
allow seepage of the drug or would be otherwise formed from a
porous material. Another embodiment employs an expanded
polytetrafluoroethylene (PTFE) tube around a support wire or metal
tube in the form of a coiled stent so that a hollow passageway is
created between the metal and the PTFE. A drug is flowed into this
space and slowly dispensed through the porous PTFE.
[0012] One embodiment of the hollow stent of the present invention
comprises a shape memory metal such as nitinol. Shape memory metals
are a group of metallic compositions that that have the ability to
return to a defined shape or size when subjected to certain thermal
or stress conditions. Shape memory metals are generally capable of
being deformed at a relatively low temperature and, upon exposure
to a relatively higher temperature, return to the defined shape or
size they held prior to the deformation. This enables the stent to
be inserted into the body in a deformed, smaller state so that it
assumes its "remembered" larger shape once it is exposed to a
higher temperature (i.e. body temperature or heated fluid) in
vivo.
[0013] Special fittings are incorporated at the ends of the hollow
stent. These fittings facilitate the injection and removal of fluid
and also allow the stent to be detached from the insertion device
to be left in place in a patient. The hollow stent has an inlet and
an outlet so that a complete fluid path can be created, and fluid
can be continually circulated through the stent. In the simplest
configuration the inlet and outlet are at opposite ends of the
stent. However, if the stent is equipped with a plurality of
lumens, two lumens can be connected at a distal end of the
structure so that the outlet and inlet are both together at one
end. Other arrangements can be readily envisioned by one of
ordinary skill in the art.
[0014] The stent is inserted into the body while connected to a
catheter in a small, deformed state. Once inside the patient's body
the stent is advanced to a desired position and expanded to its
larger full size. If the stent is composed of shape memory metal,
for example, the stent expands from its small-deformed state to its
remembered larger state due to the higher body temperature or due
to the passage of "hot" fluid through the stent. Subsequently
"treatment" fluid (e.g., heated, cryogenic or radioactive) is
pumped through the catheter to the stent where it is circulated
throughout the stent, treating the adjacent vascular walls. The
catheter can either be left in place for a certain period of time
or removed, leaving the fluid inside the stent. This would
particularly be the case with radioactive fluid or with a porous
drug delivery stent.
[0015] The stent can be removed by reattaching the catheter
allowing one to chill and shrink the stent (in the case of a memory
alloy). Alternatively, the device can readily be used in its
tethered form to remove memory alloy stents of the present
invention or of prior art design. For this purpose a device of the
present invention is inserted into the vasculature to rest within
the stent to be removed. Warm fluid is then circulated causing the
stent to expand into contact with the memory alloy stent that is
already in position. At this point cryogenic (e.g., low
temperature) fluid is circulated causing the attached stent and the
contacted stent to shrink so that the combination can be readily
withdrawn.
[0016] These and other embodiments, features and advantages of the
present invention will become more apparent to those skilled in the
art when taken with reference to the following more detailed
description of the invention in conjunction with the accompanying
drawings that are first briefly described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a hollow coiled stent.
[0018] FIG. 2 is a perspective view of a valve assembly to be used
with FIG. 1.
[0019] FIG. 3 is a sectional view of the hollow stent tube of FIG.
2.
[0020] FIG. 4 is a representation of the stent of FIG. 1 in the
position for treatment.
[0021] FIG. 5 is a sectional view of a second embodiment of a
hollow coiled stent.
[0022] FIG. 6 is a perspective view of a second embodiment of a
hollow coiled stent.
[0023] FIG. 7 is a perspective view of a third embodiment of a
hollow coiled stent.
[0024] FIG. 8 is a perspective view of a valve assembly to be used
with FIG. 6.
[0025] FIG. 9 is a perspective view of a fourth embodiment of a
hollow coiled stent.
[0026] FIG. 10 is a sectional view of the hollow stent tube of FIG.
8.
[0027] FIG. 11 (11a, 11b, and 11c) is an illustration of the method
detailed in FIG. 12.
[0028] FIG. 12 is a flow diagram explaining use a stent of the
present invention to a shape memory stent already in place.
DETAILED DESCRIPTION OF THE INVENTION
[0029] The following detailed description should be read with
reference to the drawings, in which like elements in different
drawings are identically numbered. The drawings, which are not
necessarily to scale, depict selected preferred embodiments and are
not intended to limit the scope of the invention. The detailed
description illustrates by way of example, not by way of
limitation, the principles of the invention. This description will
clearly enable one skilled in the art to make and use the
invention, and describes several embodiments, adaptations,
variations, alternatives and uses of the invention, including what
is presently believed to be the best mode of carrying out the
invention.
[0030] Referring now to the drawings, in which like reference
numbers represent similar or identical structures throughout the
drawings, FIG. 1 depicts a preferred embodiment of this invention.
Pictured in FIG. 1 is a medical apparatus 10 comprising an
endoluminal stent 20 attached to a delivery catheter 30 by means of
a valve assembly 40. In this representation endoluminal stent 20 is
generally coiled in shape leaving a tubular space down the center
of its length. Obviously, the principle of a hollow stent can be
applied to stents of a zigzag or other construction other than
simply coiled. The tubing 22 of the stent 20 is preferably composed
of a metal material that can be crimped onto a balloon catheter
(not shown) for insertion into a body. Once positioned inside of
the body at the desired location, the balloon can be inflated,
bringing the stent from a compact small size to its enlarged full
size thus opening a pathway for blood flow.
[0031] Inside the tubing 22 of stent 20, two fluid pathways exist.
These pathways can be seen in the cross sectional view of FIG. 3.
Pathways 26 and 28 have opposite flowing fluid streams and connect
at the distal end 24 of stent 20. By allowing for opposite streams,
radioactive, heated or cryogenic liquids can continuously flow
through stent 20 for the purpose of killing or preventing
proliferation of cells. By "heated" or "hot" is meant temperatures
above body temperature. By "cryogenic" or "cold" is meant
temperatures below body temperature. The stent 20 can either remain
connected to a delivery catheter 30 for temporary insertion, or be
detached for a more permanent insertion. In either case, fluid flow
can be circulated throughout stent 20 prior to disconnection. In
the simplest design, fluid passageways connected to the stent 20
are lumens of the delivery catheter so that when the catheter is
withdrawn, fluid flow must cease.
[0032] It is also possible to provide separate flexible tubes that
are threaded through the catheter so that the delivery catheter can
be withdrawn leaving the relatively smaller fluid delivery tubes
(not shown) behind. Preventing leakage of the fluid from the stent
20 after the catheter 30 is disconnected is accomplished through a
valve mechanism contained in the catheter 30, or the stent 20
and/or both. In the example illustrated in FIG. 2 rubber or
elastomer diaphragms 25 are penetrated by small hollow needles 48
in the valve assembly 40. In addition, the valve 40 may comprise a
simple back flow preventer. Thus, when pressure is applied from
incoming fluid to the valve assembly 40, a ball 45 which sits in a
ball seat 44 is forced back against a spring 46 and the valve 40
opens for the incoming fluid pathway 28. A similar arrangement
allows pressure to open the outgoing fluid pathway 26. A check ball
valve is shown only as an example. Flap valves or any of a number
of other back flow valve designs well known in the art can be
employed. Complex systems in which a bayonet-type attachment
automatically opens a valve are also possible.
[0033] The catheter 30 comprises a catheter shaft 32, which further
contains two fluid pathways 34 and 36 as seen in FIG. 2. At the
distal end of catheter 30, the valve assembly 40 has small hollow
needles 48 that are designed to puncture elastomer diaphragms 25.
The catheter 30 is slightly larger in diameter than the stent
member 20 so that the catheter tubing wall 32 forms a friction fit
over the stent wall 22. This creates a seal between the catheter
30, and the stent 20 for fluid delivery and removal. Upon detaching
the catheter 30 leakage from the stent 20 is prevented due to the
self-healing properties of the diaphragms 25. Obviously, the back
flow preventer 40 could be on the stent 20 and the diaphragms could
be on the catheter 30.
[0034] As discussed above, stent 20 is inserted into the body to
the desired site through the use of a catheter insertion device
well known in the art. FIG. 4 depicts stent 20 in its enlarged form
after it has been inserted into the body at the affected location
and expanded. Other means of stent expansion other than a balloon
catheter are possible. If the stent 20 is formed from shape memory
metal, such as Nitinol, the heat of the body can cause the stent 20
to assume a larger, remembered form. Alternatively, heated fluid
can be circulated through the stent to cause it to recover its
remembered form. A self-expanding stent made of a spring-type alloy
can also be employed. In that case the delivery catheter would be
equipped with means (e.g., an outer sheath) to keep the stent
compressed until it was at the desired location.
[0035] By increasing the diameter of stent 20 at an affected
location, the passageway is enlarged to permit increased blood
flow. At the same time, fluids can pass through the interior of
tubes 22 of the hollow stent 20 to treat the vascular wall. The
walls of the vasculature can be treated by running either a
radioactive, cryogenic or heated fluid through the stent 20 or by
delivering a drug through a stent equipped for drug diffusion
(e.g., through holes or a porous region).
[0036] FIG. 5 depicts a second embodiment of the invention. In this
embodiment, the hollow stent 60 has only one fluid pathway 66, an
inlet without an outlet, and is used to deliver drugs to affected
areas. Once the stent 60 is inserted into place and is in its
enlarged configuration, drugs are delivered through the catheter to
the stent 60. Stent 60 can be constructed in various ways to
facilitate the delivery of drugs. In one case, as shown in FIG. 6,
the stent 60 is constructed with regions or segments that have
pores 64 to allow drug seepage from the tubing 62. Alternatively,
continuously porous metal, porous plastic, or a combination of
metal and plastic can be used. The perforations 64 or slits in the
stent to facilitate drug delivery must be of sufficiently small
size to allow the passage of the drug through the entire length of
the stent so that all areas can be treated. It will be apparent
that pore size can control the rate at which the drug is dispensed.
It is possible to cover the pores 64 with semi-permeable membrane
to further control and restrict drug outflow. A semi-permeable
membrane with inclusion of an osmotic agent with the drug will
result in water uptake and more rapid and controlled pressurized
delivery of the drug.
[0037] A third embodiment of the invention, FIG. 7, has a hollow
stent 70 containing a single fluid pathway. The tubing 72 can be
made of any of the materials discussed above, but in this
embodiment, the stent 70 has an inlet path 78 that carries the
fluid to the distal end 74 of stent 70 where it then runs through
the coils. In this embodiment, a valve 80 connects the stent 70 to
catheter 30. FIG. 8 shows a cross-sectional view of valve 80. The
pressure from the liquid sent through the catheter causes the gate
82 of valve 80 to open to allow the fluid into the inlet path 78.
The pressure that forces the opening of gate 82 causes the
simultaneous opening of gate 84, allowing the fluid that is
circulated through the stent 70 to exit through pathway 36 of
catheter 30. The fluid entering and exiting through catheter 30
must also go through a check ball valve assembly similar to the one
shown in FIG. 2. Again, flaps or other "one way" valve mechanisms
can be applied. After all incoming fluid has been delivered to the
stent 70, the absence of pressure causes gate 82 and gate 84 to
close, thereby closing valve 80. This design can be used with any
of the fluids mentioned above. The stent 70 can be used to
circulate radioactive or cryogenic fluids for treatment of the
vascular walls and can also be perforated for the delivery of
drugs.
[0038] In a fourth embodiment, a hollow coiled stent 90 is formed
from polytetrafluoroethylene (PTFE) 92. In FIG. 9, a perspective
view of this embodiment can be seen. The stent 90 consists of a
support wire 94 over which PTFE 92 is fitted. The pliable structure
resulting is then formed into a coiled stent. The PTFE 92 is fitted
around the wire 94 so that there is sufficient room to allow the
passage of fluid. FIG. 10 shows a cross-sectional view of stent 90,
illustrating the pathway 96 created around the support wire 94 to
allow the passage of fluid. In this embodiment, stretched expanded
PTFE can be used to create a porous stent to facilitate the
delivery of drugs. The wire 94 can also be hollow (passageway 95)
so that the stent 90 can simultaneously deliver drugs and
radioactive fluid or temperature regulating fluid.
[0039] A fifth embodiment of the invention is illustrated in FIG.
11 and described in a flow diagram shown in FIG. 12. This
embodiment is a method for recapturing an existing shape memory
metal stent already in the body. With reference to both FIGS. 11
and 12, a shape memory metal stent A is inserted into the body in
its small, deformed state through the use of an insertion device
well known in the art in step 112. The inserted stent A in its
deformed state is placed into the center of a memory alloy stent B
that is already in an enlarged support position in the body in step
114. The deformed stent A is then enlarged so that it comes in
contact with stent B. This can be accomplished in one of two ways.
Either the stent A may enlarge due to the higher in vivo body
temperature in step 115, or a hot liquid may be pumped through
stent A to cause it to expand in step 116. Once expanded and in
contact with stent B, cryogenic liquid may be pumped through stent
A so that both stent A and stent B are chilled and either shrink
down to their deformed states or become sufficiently relaxed to
allow ready removal in step 118. Once in a small, deformed or
relaxed state, stents A and B are easily removed from the body in
step 119 by withdrawing the catheter attached to stent A. FIG. 11a
illustrates stent A in its reduced state being inserted into stent
A. FIG. 11b shows an enlarged version of stent A contacting stent
B. Thereafter, a temperature change caused, for example, by fluid
circulating through stent A will shrink both stents and enable
their removal (FIG. 11c).
[0040] Having thus described a preferred embodiment of a hollow
endoluminal stent, it should be apparent to those skilled in the
art that certain advantages of the within system have been
achieved. It should also be appreciated that various modifications,
adaptations, and alternative embodiments thereof may be made within
the scope and spirit of the present invention. For example, a
hollow stent with a coiled, tubular shape has been illustrated,
however, many other possibilities exist for the shape and size of
the hollow stent. In addition, the passageways are illustrated as
round but could take on a variety of other shapes. The described
embodiments are to be considered illustrative rather than
restrictive. The invention is further defined by the following
claims.
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