U.S. patent application number 10/925784 was filed with the patent office on 2005-01-27 for stent delivery catheter and method of use.
Invention is credited to Boyle, William J., Muller, Paul F., Patel, Udayan G., Stack, Richard S., Stalker, Kent C. B..
Application Number | 20050021125 10/925784 |
Document ID | / |
Family ID | 23745762 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050021125 |
Kind Code |
A1 |
Stack, Richard S. ; et
al. |
January 27, 2005 |
Stent delivery catheter and method of use
Abstract
A deformable sheath is attached to a catheter and introduced
intravascularly to be expanded against an arterial wall and entrap
plaque therebetween. A stent is subsequently deployed within the
expanded sheath and the sheath is then withdrawn from within the
vasculature to leave the stent expanded against the arterial wall
with the plaque entrapped therebetween.
Inventors: |
Stack, Richard S.; (Chapel
Hill, NC) ; Patel, Udayan G.; (San Jose, CA) ;
Boyle, William J.; (Temecula, CA) ; Stalker, Kent C.
B.; (San Marcos, CA) ; Muller, Paul F.; (San
Carlos, CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
23745762 |
Appl. No.: |
10/925784 |
Filed: |
August 24, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10925784 |
Aug 24, 2004 |
|
|
|
09885468 |
Jun 19, 2001 |
|
|
|
09885468 |
Jun 19, 2001 |
|
|
|
09439692 |
Nov 15, 1999 |
|
|
|
6264671 |
|
|
|
|
Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
A61F 2/958 20130101;
A61F 2/966 20130101; A61F 2/95 20130101 |
Class at
Publication: |
623/001.11 |
International
Class: |
A61F 002/06 |
Claims
What is claimed:
1. An assembly for trapping arterial plaque against a vascular
wall, comprising: a radially outwardly deformable, tubular sheath
having a proximal end and a distal end, said sheath to be
introduced intravascularly and expanded against the vascular wall
to trap the plaque therebetween.
2. The assembly of claim 1, further comprising: a flexible
elongated tubular member with an inner lumen extending therethrough
from a proximal end of the tubular member to a distal end of the
tubular member that is attached to the proximal end of the
sheath.
3. The assembly of claim 2, wherein the tubular member is a
catheter.
4. The assembly of claim 3, wherein the sheath is an integral part
of the distal end of the catheter.
5. The assembly of claim 2, wherein the tubular member has a
plurality of perforations formed near the distal end to allow fluid
communication therethrough between the outside of the tubular
member and the inner lumen.
6. The assembly of claim 1, wherein the sheath is comprised of a
material selected from the group of materials consisting of
polymers, cross-linked materials, and composites.
7. The assembly of claim 6, wherein the sheath material has a yield
strength of between 50 psi and 300 psi.
8. The assembly of claim 7, wherein the sheath material has a break
point tensile strength of over 2000 psi.
9. The assembly of claim 1, further comprising: a radially
outwardly deformable, tubular member disposed within the sheath
between the distal end and the proximal end of the sheath to be
expanded together with the sheath against the vascular wall.
10. The assembly of claim 9, wherein the deformable member is
comprised of a material selected from the group of materials
consisting of metals and thermoplastics.
11. The assembly of claim 9, wherein the deformable member is a
wire mesh.
12. The assembly of claim 9, wherein the deformable member is a
stent.
13. The assembly of claim 9, wherein the deformable member is a
wire coil.
14. The assembly of claim 9, further comprising: a flexible,
elongated tubular member having an inner lumen extending
therethrough from a proximal end of the tubular member to a distal
end of the tubular member attached to the proximal end of the
sheath to introduce the sheath with the deformable member
intravascularly.
15. The assembly of claim 14, wherein the tubular member is a
catheter.
16. The assembly of claim 15, wherein the sheath is an integral
part of the distal end of the catheter.
17. The assembly of claim 14, wherein the tubular member has
perforations formed near the distal end to allow fluid
communication therethrough between the outside of the tubular
member and the inner lumen.
18. The assembly of claim 9, wherein the sheath is comprised of a
material selected from the group of materials consisting of
polymers, cross-linked materials, and composites.
19. The assembly of claim 19, wherein the sheath material has a
yield strength of between 50 psi and 300 psi.
20. The assembly of claim 19, wherein the sheath material has a
break point tensile strength of over 2000 psi.
21. The assembly of claim 9, wherein the deformable member is
formed from a radiopaque material.
22. The assembly of claim 9, wherein the deformable member is
formed from a shape memory alloy having a compressed state for
placing within the unexpanded sheath and an expanded state for
anchoring the sheath against the vascular wall, and exhibiting a
radially outward expansive force when in the compressed state.
23. The assembly of claim 22, wherein the resistance to elastic
deformation of the sheath is greater than the expansive force
exhibited by the deformable member.
24. The assembly of claim 23, wherein the resistance to elastic
deformation of the sheath is between 1 percent to 5 percent greater
than the expansive force exhibited by the deformable member.
25. The assembly of claim 14, further comprising: a catheter
disposed within the lumen of the tubular member with a balloon
portion of the catheter lying within the deformable member to
expand the deformable member together with the sheath against the
vascular wall.
26. The assembly of claim 9, wherein the deformable member is
embedded within the sheath.
27. The assembly of claim 26, wherein the deformable member is a
wire coil.
28. The assembly of claim 26, wherein the deformable member is a
stent.
29. A method for entrapping plaque particles against a vascular
wall at a predetermined intravascular site, comprising the steps
of: providing a radially outwardly deformable, tubular sheath
having a proximal end and a distal end; providing an intravascular
deployment catheter having a proximal end, a distal end, and a
lumen extending therebetween; attaching the sheath proximal end to
the deployment catheter distal end; introducing the deployment
catheter into the vasculature; advancing the deployment catheter
through the vasculature to position the sheath at the intravascular
site; and expanding the sheath against the vascular wall at the
intravascular site to trap the plaque therebetween.
30. The method of claim 29, wherein the sheath is formed as a
unitary part of a distal tip of the deployment catheter.
31. The method of claim 29, wherein the step of providing an
intravascular deployment catheter comprises providing an
intravascular deployment catheter having a plurality perforations
formed near the distal end of the deployment catheter to allow
fluid communication between the outside of the deployment catheter
and the deployment catheter lumen.
32. The method of claim 29, wherein the sheath is comprised of a
material selected from the group of materials consisting of
polymers, cross-linked materials, and composites.
33. The device of claim 32, wherein the sheath material has a yield
strength of between 50 psi and 300 psi.
34. The method of claim 33, wherein the sheath material has a break
point tensile strength of over 2000 psi.
35. The method of claim 29, comprising, prior to the step of
introducing the deployment catheter, the further steps of:
providing a radially outwardly deformable, tubular member;
disposing the deformable member within the sheath; and wherein the
step of expanding the sheath comprises expanding the deformable
member along with the sheath, the sheath contacting the vascular
wall and the deformable member contacting the sheath.
36. The method of claim 35, wherein the deformable member is a wire
mesh.
37. The method of claim 35, wherein the deformable member is a
stent.
38. The method of claim 35, wherein the deformable member is a wire
coil.
39. The method of claim 35, wherein the deformable member is formed
from a shape memory alloy having a compressed state for placing
within the unexpanded sheath and an expanded state for anchoring
the sheath against the vascular wall, and exhibiting a radially
outward expansive force when in the compressed state.
40. The method of claim 39, wherein the resistance to elastic
deformation of the sheath is greater than the expansive force
exhibited by the deformable member.
41. The method of claim 40, wherein the resistance to elastic
deformation of the sheath is between 1 percent to 5 percent greater
than the expansive force exhibited by the deformable member.
42. The method of claim 35, wherein the deformable member is formed
from a radiopaque material.
43. The method of claim 35, wherein the deformable member is
embedded within the sheath.
44. The method of claim 43, wherein the deformable member is a wire
stent.
45. The method of claim 43, wherein the deformable member is a wire
coil.
46. The method of claim 29, comprising, following the step of
expanding the sheath, the further steps of: providing a delivery
catheter having a proximal end and a distal end and a lumen
extending therebetween; providing a self-expanding intravascular
device having a proximal end and a distal end and further having a
compressed state and an expanded state; placing the intravascular
device in its compressed state within the delivery catheter distal
end; introducing the delivery catheter into the lumen of the
deployment catheter; advancing the delivery catheter through the
lumen of the deployment catheter to position the distal end of the
delivery catheter adjacent the distal end ofthe sheath; partially
retracting the delivery catheter to allow the distal end of the
intravascular device to expand against the vessel wall at a
location distal of the plaque at the intravascular site;
withdrawing the sheath proximally from the intravascular site to
expose the distal end of the delivery catheter; retracting the
delivery catheter to allow the entire intravascular device to
expand against the vessel wall at the intravascular site and trap
the plaque therebetween; withdrawing the delivery catheter from
within the intravascular catheter; and withdrawing the
intravascular catheter and the sheath from within the
vasculature.
47. The method of claim 46, wherein: the step of providing a
delivery catheter further comprises providing a pusher rod disposed
within the delivery catheter lumen to contact the proximal end of
the intravascular device; and the steps of advancing the
intravascular device out of the delivery catheter comprise
withdrawing the delivery catheter proximally along the pusher rod
to expose the intravascular device and thereby allow it to assume
its expanded state.
48. The method of claim 46, wherein the intravascular device is a
stent.
49. The method of claim 48, wherein the stent is formed with a
plurality of apertures, each aperture being no larger than 200
microns across when the stent is in the expanded state.
50. The method of claim 46, wherein the intravascular device is a
wire mesh.
51. The method of claim 50, wherein the wire mesh is formed with a
plurality apertures, each aperture being no larger than 200 microns
across when the wire mesh is in the expanded state.
52. The method of claim 46, wherein: the step of expanding the
sheath against the vascular wall comprises partially expanding the
sheath; and comprising, after the step of withdrawing the delivery
catheter, the further steps of: providing a balloon catheter;
inserting the balloon catheter into the lumen of the deployment
catheter; advancing the balloon catheter to position the balloon
within the intravascular device; inflating the stent to further
expand the intravascular device against the vessel all and entrap
the plaque therebetween; and withdrawing the balloon catheter from
the deployment catheter lumen.
53. The method of claim 46, wherein the step of providing a
delivery catheter comprises providing a delivery catheter with
perforations formed near the distal end of the delivery catheter to
allow fluid communication between the outside of the delivery
catheter and the delivery catheter lumen.
54. An assembly for trapping arterial plaque against a vascular
wall, comprising: a deployment catheter having a proximal end, a
distal end, and an inner lumen extending therebetween; a radially
outwardly, deformable, tubular sheath to be introduced
intravascularly and expanded against the vascular wall to entrap
the plaque therebetween, the sheath having a proximal end attached
to the deployment catheter distal end, and a distal end; a delivery
catheter being axially movably disposed within the deployment
catheter lumen and having a distal end and an inner lumen; a
self-expanding intravascular device disposed within the delivery
catheter lumen adjacent the delivery catheter distal end; an outer
sheath disposed over the deployment catheter to receive the
deformable sheath therein; and a pusher rod axially movably
disposed within the delivery catheter lumen proximal of the
intravascular device.
55. The assembly of claim 14, further comprising: an outer sheath
disposed over the tubular member to receive the sheath therein.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to angioplasty procedures, and
more particularly to a device and method to prevent arterial plaque
from being dislodged from the arterial wall in procedures such as,
for example, percutaneous transluminal coronary angioplasty (PTCA)
or percutaneous transluminal angioplasty (PTA), especially carotid
PTA, and migrating into the patient's vasculature.
[0003] In typical carotid PTA procedures, a guiding catheter or
sheath is percutaneously introduced into the cardiovascular system
of a patient through the femoral arteries and advanced through the
vasculature until the distal end of the guiding catheter is in the
common carotid artery. A guidewire and a dilatation catheter having
a balloon on the distal end are introduced through the guiding
catheter with the guidewire sliding within the dilatation catheter.
The guidewire is first advanced out of the guiding catheter into
the patient's carotid vasculature and is directed across the
arterial lesion. The dilatation catheter is subsequently advanced
over the previously advanced guidewire until the dilatation balloon
is properly positioned across the arterial lesion. Once in position
across the lesion, the expandable balloon is inflated to a
predetermined size with a radiopaque liquid at relatively high
pressures to radially compress the atherosclerotic plaque of the
lesion against the inside of the artery wall and thereby dilate the
lumen of the artery. The balloon is then deflated to a small
profile so that the dilatation catheter can be withdrawn from the
patient's vasculature and the blood flow resumed through the
dilated artery. As should be appreciated by those skilled in the
art, while the above-described procedure is typical, it is not the
only method used in angioplasty.
[0004] In angioplasty procedures of the kind referenced above,
abrupt reclosure may occur or restenosis of the artery may develop
over time, which may require another angioplasty procedure, a
surgical bypass operation, or some other method of repairing or
strengthening the area. To reduce the likelihood of the occurrence
of abrupt reclosure and to strengthen the area, a physician can
implant an intravascular prosthesis for maintaining vascular
patency, commonly known as a stent, inside the artery across the
lesion. The stent is crimped tightly onto the balloon portion of
the catheter and transported in its delivery diameter through the
patient's vasculature. At the deployment site, the stent is
expanded to a larger diameter, often by inflating the balloon
portion of the catheter. The stent also may be of the
self-expanding type.
[0005] A danger always present during any intravascular procedure
is the potential for particles of the atherosclerotic plaque, which
can be extremely friable, breaking away from the arterial wall.
These emboli can subsequently migrate through the patient's
vasculature to sensitive organs such as the brain, where they may
induce trauma.
[0006] 2. Description of the Prior Art
[0007] The majority of devices that have been proposed to prevent
the problem of emboli generated during an angioplasty procedure
fall into either of two broad categories: devices that simply
intercept emboli flowing within the patient's blood stream, and
devices that intercept as well as remove such emboli from within
the patient's body. A device typical of the first category is
described by Goldberg in U.S. Pat. No. 5,152,777 and consists of a
filter comprised of a plurality of resilient, stainless steel wire
arms joined at one end so as to form a conical surface, and having
rounded tips at their other ends to prevent damage to the vessel
walls. Alternatively, the filter may be attached to a catheter
through which lysing agents can be introduced to dissolve any
trapped emboli. Most devices of this type are intended for
permanent deployment within the patient's body, and thus pose the
risk of trapping sufficient emboli to adversely affect the flow of
blood within the vessel in which they are deployed. Furthermore,
any foreign object in the body tends to provoke a response from the
immune system and over time can lead to endothelial cell
formation.
[0008] Devices that remove emboli from the blood stream are similar
to the filter devices described above and are typically connected
to a deployment device such as a catheter that permits their
withdrawal from the vasculature. U.S. Pat. No. 4,969,891 to
Gewertz, for example, discloses a removable vascular filter
permanently attached to a wire sufficiently long to extend out of
the patient when the filter is deployed within. The filter is
comprised of a bundle of wires secured together and having end
portions that flare outwards to form the actual filter element. The
filter is introduced through a catheter and the filter wires expand
on their own once released from the catheter to obstruct the vessel
and strain the blood flowing therethrough. This device, and others
like it, are not adapted for permanent deployment within the body
and can only be used for limited periods of time, limiting their
efficacy.
[0009] In light of the above, it becomes apparent that there
remains a need for a device or method that will prevent friable
plaque from breaking away from arterial walls during intravascular
procedures and forming emboli in the bloodstream, that is easy and
safe to deploy, and that may be easily removed or alternatively
employed over extended periods of time with minimal adverse impact
or immunological response.
SUMMARY OF THE INVENTION
[0010] The present invention addresses the above mentioned need by
providing a sheath at the distal tip of a catheter to be expanded
against an arterial wall and trap plaque therebetween. A stent or
other intravascular graft subsequently can be partially deployed
distally of the plaque, the sheath then can be removed, and the
stent fully expanded to trap the arterial plaque and any emboli
between the stent and the arterial wall.
[0011] Thus, in one aspect, it is an object of the present
invention to provide a device for trapping plaque against a
vascular wall comprising an expandable sheath mounted to the distal
end of an elongated tube such as a catheter, the sheath to be
expanded by a balloon against a mass of atherosclerotic plaque site
lining the intima of a body vessel. In another aspect of the
present invention, the expandable sheath is reinforced by an
expandable element embedded within it.
[0012] In yet another aspect of the present invention, an assembly
is provided for trapping plaque against a vascular wall comprising
an expandable sheath mounted to the distal end of an elongated tube
such as a perfusion catheter, a delivery catheter axially slidably
disposed within the perfusion catheter, a self-expanding
intravascular device such as a stent disposed within the distal tip
of the delivery catheter, and a pusher rod axially slidably
disposed within the delivery catheter.
[0013] It is a further object of the present invention to provide a
method for trapping plaque against a vascular wall comprising the
steps of expanding a sheath mounted to the distal end of an
elongated tube such as a perfusion catheter against the plaque,
inserting within the perfusion catheter a delivery catheter with a
self-expanding intravascular device such as a stent or
intravascular graft disposed within its distal end and a pusher rod
disposed adjacent the intravascular device, positioning the
delivery catheter distal tip within the expanded sheath, partially
withdrawing the delivery catheter to allow the distal portion of
the intravascular device to expand against the vessel wall at a
location distal of the plaque, withdrawing the expanded sheath, and
withdrawing the delivery catheter to expose the rest of the
intravascular device and thus allow it to fully expand and trap the
plaque against the vessel wall.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1a depicts a cross-sectional side view of an expandable
sheath device according to the present invention inserted into a
body vessel at an atherosclerotic plaque site;
[0015] FIG. 1b depicts a cross-sectional side view of the device
shown in FIG. 1a with the sheath in an expanded configuration;
[0016] FIG. 2a depicts a side view, partially in cross-section, of
the device shown in FIG. 1a with a balloon catheter inserted
therethrough;
[0017] FIG. 2b depicts a side view, partially in cross-section, of
the device shown in FIG. 2a with the sheath expanded by the
catheter balloon and the plaque shown in FIG. 1 partially
compressed against the vascular wall;
[0018] FIG. 2c depicts a side view, partially in cross-section, of
the device shown in FIG. 2b with the sheath in an expanded
configuration after the balloon catheter has been deflated and
withdrawn;
[0019] FIG. 2d depicts a side view, partially in cross-section, of
the device shown in FIG. 2c with a delivery catheter inserted
therethrough and a self-expanding stent disposed within the
delivery catheter in a compressed state;
[0020] FIG. 2e depicts a side view, partially in cross-section, of
the device shown in FIG. 2d with the delivery catheter partially
withdrawn and the exposed distal portion of the self-expanding
stent in an expanded state contacting the vessel wall at a location
distal of the partially compressed plaque;
[0021] FIG. 2f depicts a side view, partially in cross-section, of
the device shown in FIG. 2e with the sheath withdrawn proximally
from contact with the plaque to expose the distal tip portion of
the delivery catheter;
[0022] FIG. 2g depicts a side view, partially in cross-section, of
the device shown in FIG. 2f with the delivery catheter fully
withdrawn and the self-expanding stent in a fully expanded state
against the vascular wall to compress and trap the plaque
therebetween;
[0023] FIG. 3 depicts a side view, partially in cross-section, of
the device shown in FIG. 1a with a coil embedded within the
sheath;
[0024] FIG. 4a depicts a side view of the expandable sheath device
shown in FIG. 1a with a stent embedded in the sheath; and
[0025] FIG. 4b depicts a side view of the device shown in FIG. 4a
with the sheath and the stent embedded therein expanded against the
plaque on the vascular wall.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] With reference to FIG. 1a, wherein a preferred embodiment of
the catheter assembly and expandable sheath device of the present
invention is depicted in its operating environment, expandable
sheath 100 is comprised of a tubular wall 102 with a proximal end
104 and a distal end 106, and defining an inner lumen 108 extending
therebetween. Sheath 100 as depicted in FIG. 1a is in its
unexpanded configuration.
[0027] With continued reference to FIG. 1a, sheath 100 preferably
is connected to a delivery/deployment device 120 that can introduce
the sheath into a patient's body lumen 110 and advance it to the
desired deployment site. Insertion device 120 is preferably an
elongated tubular member such as catheter 130 depicted in FIG. 1a,
with catheter wall 131 defining inner lumen 132 which extends from
distal end 134 to a proximal end [not shown] that remains outside
of the patient's body. Radiopaque marker 136 is disposed at distal
end 134 to enable a physician to precisely position the catheter
and sheath with the aid of fluoroscopy.
[0028] In a preferred embodiment, catheter 130 is a perfusion
catheter provided with perfusion holes 138 formed near distal end
134. Perfusion holes 138 extend from the outside of catheter 130
through catheter wall 131 to inner lumen 132 to allow blood or any
other fluid flowing through body lumen 110 to pass between the
outside of the catheter and the inner lumen. This feature allows
the sheath of the present invention and its associated delivery
device to be deployed within a patient's vasculature for extended
periods of time without blocking the patient's blood flow. In a
preferred embodiment, blood flow through the perfusion holes will
be somewhat less than normal blood flow which will lessen the
chance of dislodging particles, and if particles are dislodged, the
emboli will move more slowly in the reduced blood flow and will be
easier to trap in sheath 100.
[0029] Sheath 100 is formed from a permanently deformable material,
preferably a polymeric material such as a low or medium molecular
weight polyolefin, examples of which include PE, EVAc, EVA, and
Ionomers. Any other plastically deformable material or blend of
materials, including cross-linked materials and composites, may be
suitable. The material, once formed into sheath 100, should
preferably display a plastic yield strength of between 50 psi and
300 psi, and a tensile break strength of over 2,000 psi. The
catheter is of conventional construction with an inner diameter of
preferably no less than 8 French in size. Sheath 100 may be
attached to distal end 134 of catheter 130 by any known means, such
as adhesives or thermoplastics, or may be formed integrally as one
piece with the catheter wall 131 through any known extrusion,
drawing, rolling, or similar process.
[0030] With reference now to FIG. 1b, when formed from a material
such as described above, sheath 100 is plastically deformable by a
typical angioplasty balloon. When expanded by such a balloon,
sheath 100 assumes the expanded configuration depicted in FIG. 1b,
wherein the sheath is deployed against vascular wall 112 and any
arterial plaque 114 deposited thereon, thus compressing and
trapping the plaque against the vascular wall.
[0031] In keeping with the invention, as shown in FIG. 2a, in a
preferred method of use of the device of the present invention,
guidewire 200 is first inserted percutaneously in a conventional
manner and advanced through a guide catheter [not shown] and then
the patient's body lumen 110 until its distal end lies distal of
the arterial plaque 114. Perfusion catheter 130 with sheath 100
attached to its distal end 134 is next inserted into the guide
catheter and advanced therethrough over guidewire 200 until the
sheath is positioned adjacent to arterial plaque 114 in the
patient's body lumen. Radiopaque marker 136 on distal end 134 of
perfusion catheter 130 aids the operating physician in accurately
placing the catheter and sheath 100 within body lumen 110 by
tracking the progress of the radiopaque marker on an x-ray or
similar visualization apparatus.
[0032] Once perfusion catheter 130 has been properly positioned
with sheath 100 adjacent to arterial plaque 114, guidewire 200 may
optionally be withdrawn. Conventional balloon catheter 210 next is
inserted within inner lumen 132 of perfusion catheter 130 and
advanced over guidewire 200 until balloon 212 on the distal end of
the balloon catheter is positioned within sheath 100 with the
distal end of the balloon extending past the distal end of the
sheath. It is understood that the type of balloon catheter that is
employed is dictated by whether guidewire 200 remains within
perfusion catheter 130 throughout the procedure or is withdrawn
following placement of perfusion catheter 130 and sheath 100.
Balloon catheter 210 will typically also have a radiopaque marker
214 to aid the physician in accurately placing balloon 212.
Optionally, balloon catheter 210 may also be a perfusion catheter
with perfusion holes 218 provided distally and proximally of the
balloon 212, which allow uninterrupted blood flow to the brain
throughout the entire procedure.
[0033] Referring now to FIG. 2b, once properly positioned within
sheath 100, balloon 212 is inflated to a predetermined pressure.
Sheath 100 is expanded by balloon 212 as the balloon is inflated,
and therefore the balloon must be inflated with fluid of sufficient
pressure to overcome the plastic yield strength of the sheath and
thus plastically, or permanently, expand the sheath. Balloon 212 is
inflated to a size sufficient to expand sheath 100 against vascular
wall 112 and thus compress arterial plaque 114 and trap the plaque
against the vascular wall. In this manner any portions of arterial
plaque 114 that may have become loose are prevented by sheath 100
from breaking away from vascular wall 112 and embolizing in the
blood stream of the patient.
[0034] With reference to FIG. 2c, after sheath 100 has been
expanded and has trapped arterial plaque 114 against vascular wall
112, balloon 212 is deflated and allowed to regress to its folded
configuration, following which balloon catheter 210 is withdrawn
from within perfusion catheter 130. At this point perfusion
catheter 130 is still located within body lumen 110 to maintain
expanded sheath 100 in position to retain arterial plaque 114
against vascular wall 112. At this time perfusion holes 138 allow
blood to flow uninterrupted through body lumen 110 by providing a
flow channel between proximal end 104 and distal end 106 of sheath
100. Blood thus flows from the outside of perfusion catheter 130 on
the proximal side of sheath 100 through perfusion holes 138, into
sheath inner lumen 108, out through expanded sheath distal end 106,
and on into body lumen 110 on the distal end of the sheath.
Providing perfusion holes 138 in perfusion catheter 130 therefore
enables use of the device of the present invention over extended
periods of time with no adverse effects that may otherwise be
induced by throttling off the patient's normal blood flow. This is
especially important in applications to the carotid artery, which
supplies blood to the brain and which could trigger a stroke or
seizure if starved of blood.
[0035] In the next step, as depicted in FIG. 2d, delivery catheter
310 is inserted into interior lumen 132 of perfusion catheter 130.
Delivery catheter 310 is of conventional construction and may
include perfusion holes 312 to allow blood flow therethrough.
Self-expanding stent 320 is disposed within the distal end of
delivery catheter 310, which further includes pusher rod 316
disposed within it and adjacent to the stent. Pusher rod 316 is
formed with pusher plate 318 mounted at its distal end, and the
pusher rod is disposed within delivery catheter 310 such that the
pusher plate is adjacent to and in contact with the proximal end of
stent 320. If guidewire 200 is utilized to advance delivery
catheter 310, then pusher plate 318 and optionally pusher rod 316
must be formed with an appropriately sized lumen [not shown] to
permit the guidewire to pass through.
[0036] Self-expanding stent 320 can be formed from any number of
materials, including metals, metal alloys, and polymeric materials.
Preferably, the stents are formed from metal alloys such as
stainless steel, tantalum, or the so-called heat-sensitive metal
alloys such as nickel titanium (NiTi). When formed from
shape-memory alloys such as NiTi, stent 320 will remain passive in
its martensitic state when it is kept at a temperature below the
transition temperature. In this case, the transition temperature
will be below the normal body temperature, or about 98.6.degree.
F., and in a preferred embodiment the stent self expands at room
temperature. When the NiTi is exposed to normal body temperature
upon insertion of delivery catheter 310 into perfusion catheter
130, it will attempt to return to its austenitic state and, if not
constrained, will rapidly expand radially outwardly to assume its
preformed, expanded state. Alternative shape-memory materials that
may be used to form stent 320 include stress-induced martensite
(SIM) alloys, which transform into martensite upon the application
of stress such as a compressive load, and return to their
austenitic, preformed state when the stress is removed.
[0037] Stent 320 is thus restrained by delivery catheter 310 from
assuming its expanded state, and the delivery catheter wall must be
of sufficient thickness to withstand the radially outward expansive
forces exerted by the stent upon it. Delivery catheter 310
typically is provided with radiopaque marker 314 to aid the
physician in accurately positioning its distal tip relative to
sheath 100. The radiopacity of stent 320 also further enhances the
visualization of delivery catheter 310 via fluoroscopy. With
continued reference to FIG. 2d, upon insertion into interior lumen
132, delivery catheter 310 is advanced through perfusion catheter
130 until it is placed so as to position the distal end of stent
320 outside distal end 106 of sheath 100, and thus distally of
plaque 114.
[0038] Referring now to FIG. 2e, the preferred method of deployment
entails disposing the distal portion of stent 320 distally of
distal end 106 of sheath 100, and thus distally of arterial plaque
114, and then partially retracting delivery catheter 310 proximally
to expose the distal portion of the stent. While retracting
delivery catheter 310 proximally, pusher rod 316 is immobilized so
as to ensure that stent 320 does not travel proximally along with
the delivery catheter due to any frictional forces applied by the
wall of the delivery catheter as it slides over the stent. Thus, as
delivery catheter 310 is retracted proximally, the stent will
likely be urged proximally along with it by the friction between
the delivery catheter wall and the stent outer surface, but the
progress of the stent will be halted by pusher plate 318, which
will ensure that the stent remains located at the position
initially selected by the physician for deployment.
[0039] With continued reference to FIG. 2e, as delivery catheter
310 is retracted, the distal portion of self-expanding stent 320
becomes exposed and, because the restraint applied by the delivery
catheter is thereby removed, the radially outward expansive forces
exhibited by the stent urge the distal portion of the stent to
assume its expanded state, with the distal end of the stent thus
expanding to contact the vessel wall 112 at a location distal of
the arterial plaque 114. At this point stent 320, although only
partially deployed, is in position to intercept any plaque that may
come loose and break off from vascular wall 112.
[0040] To be able to intercept and retain plaque that may break
off, the stent must be designed such that, when in its expanded
state, the apertures in the stent wall are no larger than about 200
microns, more preferably no larger than about 50 to 100 microns,
and in a preferred embodiment no larger than 25 microns. Thus, the
stent may be an expandable tube with slots or other shaped
apertures cut therein, or a wire mesh, or a wire coil, or any other
practicable self-expanding device. Co-owned U.S. Pat. No. 5,514,154
to Lau et al., U.S. Pat. No. 5,569,295 to Lam, U.S. Pat. No.
5,591,197 to Orth et al., U.S. Pat. No. 5,603,721 to Lau et al.,
U.S. Pat. No. 5,649,952 to Lam, U.S. Pat. No. 5,728,158 to Lau et
al., and U.S. Pat. No. 5,735,893 to Lau et al. describe suitable
stents, and these patents are hereby incorporated herein in their
entirety by reference thereto. The device of the present invention
may also be used in conjunction with other expandable intravascular
devices, such as grafts or fine mesh filters that may have a
completely or substantially closed outer surface.
[0041] In the next step, as depicted in FIG. 2f, perfusion catheter
130 is withdrawn proximally to retract sheath 100 from contact with
plaque 114 and expose the distal tip of delivery catheter 310 to
the plaque. This step presents the potential for portions of plaque
114 breaking off due to the frictional forces between the sliding
sheath and the plaque, but because the distal end of stent 320 is
deployed against vascular wall 112, any dislodged plaque will be
safely intercepted and retained by the stent. The remaining,
restricted length of stent 320, which is still disposed within
delivery catheter 310, can now be deployed directly against plaque
114.
[0042] Therefore, as shown in FIG. 2g, in the next step delivery
catheter 310 is retracted to expose the entire length of stent 320
and thereby allow the rest of the stent to fully expand against
vascular wall 112 and thus further compress and trap arterial
plaque 114 therebetween. At this time plaque 114 is safely
stabilized against vascular wall 112, the cross-section of the body
lumen 110 has been largely restored to about its nominal size, and
the procedure is almost completed. In the following steps [not
shown in the Figures], guidewire 200, delivery catheter 310, and
perfusion catheter 130 are withdrawn from the body lumen, either
sequentially or as one unit, and the entry wound into the patient's
body is closed. Optionally, prior to withdrawing perfusion catheter
130, the physician may choose to insert a balloon catheter into the
perfusion catheter and further expand stent 320 with the balloon to
ensure that plaque 114 is sufficiently compressed and/or lumen 110
has been sufficiently expanded.
[0043] Referring once again to FIG. 2e, in an alternative
embodiment the assembly of the present invention may additionally
comprise outer sheath 350, which overlies perfusion catheter 130
and is sized so that when in its expanded state, sheath 100 may be
retracted into outer sheath. The principal purpose of outer sheath
350 is to scrape off any plaque that may be adhering to the outer
surface of sheath 100, and thus the outer sheath is preferably
sized so that, as shown in FIG. 2f, expanded sheath 100 contacts
the outer sheath as the expanded sheath is drawn into the outer
sheath and thereby dislodges any plaque adhering to the expanded
sheath. It would therefore be advantageous if outer sheath is
formed of a relatively flexible, compliant material such as PTFE
that will expand to accommodate expanded outer sheath 100 as it is
drawn into the outer sheath, and thus allow the physician to expand
sheath 100 to any desired size during the procedure with no
limitations imposed on the maximum expandable size of sheath 100 by
outer sheath 350. To further aid the process, proximal end 104 of
sheath 100 may be formed with an angled configuration that will
more easily slide into outer sheath 350.
[0044] In an alternative embodiment of the device of the present
invention, as depicted in FIG. 3, sheath 100 comprises an
expandable support element such as helical coil 400 embedded within
tubular wall 102. The purpose of coil 400 is to impart additional
structural strength and crush resistance to sheath 100, and thus
enable the sheath to better support body lumen 110 while a stent or
graft is being deployed. An alternative embodiment of an expandable
support element is depicted in FIG. 4a, wherein stent 500 is
embedded in tubular wall 102. FIG. 4b depicts sheath 100 with stent
500 in an expanded configuration. Such reinforced sheaths may be
used to expand body lumen 110 to 100 percent or more of its
nominal, unconstricted size.
[0045] With continued reference to FIGS. 3 and 4, in an alternative
embodiment of the device of the present invention, the expandable
support element such as illustrated by coil 400 and stent 500 may
comprise materials exhibiting shape memory properties, such as
spring steel, Nitinol, superelastic or shape memory nickel-titanium
alloys, and resilient engineering plastics such as polysulfones,
PEEK, polysulfides, LCPs, etc. In such an embodiment, the
expandable support element would be formed to exhibit a radially
outward expansive force that is weaker than the force required for
plastic deformation of sheath 100 and, preferably, the resistance
to elastic deformation of the sheath would be between one and five
percent greater than the expansive force exhibited by the support
element. The sheath would thus remain in its unexpanded
configuration until expanded by a balloon or similar expansion
device, as detailed elsewhere in the specification, but would
require a lessened degree of expansive force (e.g., a lower balloon
inflation pressure) to be deployed into its expanded configuration
due to the aiding outward force exhibited by the expandable support
element. These embodiments could also be used in conjunction with
outer sheath 350, as discussed previously in conjunction with FIGS.
2e & 2f.
[0046] In view of the foregoing, it is apparent that the device and
method of the present invention enhance substantially the safety of
angioplasty procedures by significantly reducing the risk
associated with friable plaque deposits breaking away from the
vascular wall and migrating into the patient's blood stream to form
emboli and potentially cause injury. Further modifications and
improvements may additionally be made to the device and method
disclosed herein without departing from the scope of the invention.
Accordingly, it is not intended that the invention be limited,
except as by the appended claims.
* * * * *