U.S. patent application number 10/358029 was filed with the patent office on 2004-03-04 for stent and stent-graft for treating branched vessels.
Invention is credited to Chouinard, Paul F., Clerc, Claude O., Thompson, Paul J..
Application Number | 20040044396 10/358029 |
Document ID | / |
Family ID | 49230952 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040044396 |
Kind Code |
A1 |
Clerc, Claude O. ; et
al. |
March 4, 2004 |
Stent and stent-graft for treating branched vessels
Abstract
An implantable stent and stent-graft for treating a patient
having a relatively healthy first aorta portion upstream from a
renal artery branch, and a diseased aorta portion downstream from
the renal artery branch. One embodiment of the device includes a
fixation section, a renal artery branch section and a diseased
aorta section, all of which can be tubular, radially compressible
and self-expandable structures formed from a plurality of filaments
which are helically wound in a braided configuration. When the
device is implanted and in its expanded state, the fixation section
engages the first aorta portion upstream from a renal artery branch
to provide substantial anchoring support. The diseased aorta
section engages the portion of the aorta downstream from the renal
artery branch and extends across the diseased portion of the aorta
for purposes of treatment. The renal artery branch section extends
across the renal artery branch and connects the diseased aorta
section to the fixation section while allowing blood flow between
the aorta and renal artery branch.
Inventors: |
Clerc, Claude O.;
(Marlborough, MA) ; Chouinard, Paul F.; (Maple
Grove, MN) ; Thompson, Paul J.; (Minnetonka,
MN) |
Correspondence
Address: |
RATNERPRESTIA
P O BOX 980
VALLEY FORGE
PA
19482-0980
US
|
Family ID: |
49230952 |
Appl. No.: |
10/358029 |
Filed: |
February 4, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10358029 |
Feb 4, 2003 |
|
|
|
09021804 |
Feb 11, 1998 |
|
|
|
60047749 |
May 27, 1997 |
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Current U.S.
Class: |
623/1.13 ;
623/1.35 |
Current CPC
Class: |
A61F 2/856 20130101;
A61F 2002/065 20130101; A61F 2220/0016 20130101; A61F 2/07
20130101; A61F 2002/061 20130101; A61F 2230/0008 20130101; A61F
2/90 20130101; A61F 2002/075 20130101 |
Class at
Publication: |
623/001.13 ;
623/001.35 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. An implantable medical device for treating a section of a
patient's vessel having a vessel branch, a relatively healthy first
vessel portion on a first side of the vessel branch, and a diseased
vessel portion on a second side of the vessel branch, including: a
fixation section comprising a plurality of filaments which are
helically wound in a braided configuration to form a tubular,
radially compressible and self-expandable structure, for engaging
the first vessel portion on the first side of the vessel branch
when in an expanded state to provide substantial anchoring support
for the implanted medical device; a diseased section comprising a
plurality of filaments which are helically wound in a braided
configuration to form a tubular, radially compressible and
self-expandable structure, for engaging a portion of the vessel on
the second side of the vessel branch and extending across and
treating the diseased vessel portion; and a branch section
comprising a radially compressible and expandable structure, for
extending across the vessel branch and connecting the diseased
section to the fixation section while allowing blood flow to the
vessel branch.
2. The implantable medical device of claim 1 wherein the branch
section includes a plurality of filaments extending between the
fixation section and the diseased section.
3. The implantable medical device of claim 2 wherein the branch
section filaments are generally parallel to one another and have
opposite ends wrapped around the filaments of the fixation section
and the diseased section.
4. The implantable medical device of claim 2 wherein the filaments
of the branch section are helically wound in a braided
configuration to form a tubular, radially compressible and
self-expandable structure.
5. The implantable medical device of claim 4 wherein a free state
diameter of the fixation section is equal to a free state diameter
of the branch section.
6. The implantable medical device of claim 4 wherein a radial
pressure of the fixation section is greater than a radial pressure
of the branch section.
7. The implantable medical device of claim 6 wherein the radial
pressure of the fixation section is greater than a radial pressure
of the diseased section.
8. The implantable medical device of claim 4 wherein a density of
the filaments in the branch section is less than a density of the
filaments in the fixation section.
9. A method for manufacturing the medical device of claim 8,
including: helically winding filaments to form a tubular fixation
section and a tubular branch section having the same density of
filaments; and removing some of the filaments from the branch
section.
10. The method of claim 9 wherein helically winding filaments
includes forming a tubular fixation section and a tubular branch
section having the same free state diameter.
11. The method of claim 9 and further including: helically winding
filaments to form a fixation section, branch section and diseased
section having the same density of filaments; and removing some of
the filaments from the branch section.
12. The method of claim 11 wherein helically winding filaments
includes forming a tubular fixation section, branch section and
diseased section having the same free state diameter.
13. A method for manufacturing the medical device of claim 8,
including: helically winding filaments at a first braid angle to
form the tubular structure of the fixation section; and helically
winding the filaments at a second braid angle which is less than
the first braid angle to form the tubular structure of the branch
section.
14. The method of claim 13 wherein helically winding filaments
includes forming a tubular fixation section and tubular branch
section having the same free state diameter.
15. The method of claim 13 and further including: helically winding
filaments at a third braid angle which is greater than the second
braid angle to form the tubular structure of the diseased
section.
16. The method of claim 15 wherein helically winding filaments
includes forming a tubular fixation section, tubular branch section
and tubular diseased section having the same free state
diameter.
17. The implantable medical device of claim 8 wherein the density
of the filaments in the branch section is less than a density of
the filaments in the diseased section.
18. The implantable medical device of claim 8 wherein the density
of the filaments in the branch section is equal to a density of the
filaments in the diseased section.
19. A method for implanting the medical device of claim 1 in a
diseased vessel, including: providing the device in a radially
compressed state; delivering the device to the diseased vessel and
positioning the fixation section within the healthy first vessel
portion, the branch section within the vessel branch, and the
diseased section within the diseased vessel portion; and causing
the device to radially self-expand with the fixation section
engaging the first vessel portion, the branch section extending
cross the vessel branch, and the diseased section extending across
and engaging the diseased portion.
20. An implantable stent-graft for treating a section of a
patient's vessel having a vessel branch, a relatively healthy first
vessel portion on a first side of the vessel branch, and a diseased
vessel portion on a second side of the vessel branch; including: a
fixation section comprising a plurality of filaments which are
helically wound in a braided configuration to form a tubular,
radially compressible and self-expandable structure, for engaging
the first vessel portion on the first side of the vessel branch
when in an expanded state to provide substantial anchoring support
for the implanted medical device; a diseased section comprising: a
plurality of filaments which are helically wound in a braided
configuration to form a tubular, radially compressible and
self-expandable support structure, for engaging a portion of the
vessel on the second side of the vessel branch and extending across
and treating the diseased vessel portion; and a radially-expandable
membrane coextensive with at least a portion of the length of the
support structure; and a branch section comprising a radially
compressible and expandable structure, for extending across the
vessel branch and connecting the diseased section to the fixation
section while allowing blood flow to the vessel branch.
21. The stent-graft of claim 20 wherein the membrane is coextensive
with at least 75% of a continuous length of the diseased
section.
22. The stent-graft of claim 20 wherein the membrane is formed of
braided filaments.
23. The stent-graft of claim 22 wherein the membrane is formed of
braided polymeric filaments.
24. The stent-graft of claim 22 wherein the membrane is formed of
filaments interbraided with one another and the filaments of the
support structure.
25. The stent-graft of claim 20 wherein the branch section includes
a plurality of filaments extending between the fixation section and
the diseased section.
26. The stent-graft of claim 25 wherein the branch section
filaments are generally parallel to one another and have opposite
ends wrapped around the filaments of the fixation section and the
diseased section.
27. The stent-graft of claim 25 wherein the filaments of the branch
section are helically wound in a braided configuration to form a
tubular, radially compressible and self-expandable structure.
28. The stent-graft of claim 27 wherein a free state diameter of
the fixation section is equal to a free state diameter of the
branch section.
29. The stent-graft of claim 27 wherein a radial pressure of the
fixation section is greater than a radial pressure of the branch
section.
30. The stent-graft of claim 29 wherein the radial pressure of the
fixation section is greater than a radial pressure of the diseased
section.
31. The stent-graft of claim 27 wherein a density of the filaments
in the branch section is less than a density of the filaments in
the fixation section.
32. A method for manufacturing the stent-graft of claim 31,
including: helically winding and braiding filaments to form a
tubular fixation section and a tubular branch section having the
same density of filaments; and removing some of the filaments from
the branch section.
33. The method of claim 32 wherein helically winding and braiding
filaments includes forming a tubular fixation section and a tubular
branch section having the same free state diameter.
34. The method of claim 32 and further including: helically winding
and braiding filaments to form a fixation section, branch section
and diseased section having the same density of filaments; and
removing some of the filaments from the branch section.
35. The method of claim 34 wherein helically winding and braiding
filaments includes forming a tubular fixation section branch
section and diseased section having the same free state
diameter.
36. A method for manufacturing the stent-graft of claim 31,
including: helically winding and braiding filaments at a first
braid angle to form the tubular structure of the fixation section;
and helically winding and braiding the filaments at second braid
angle which is less than the first braid angle to form the tubular
structure of the branch section.
37. The method of claim 36 wherein helically winding and braiding
filaments includes forming a tubular fixation section and tubular
branch section having the same free state diameter.
38. The method of claim 36 and further including: helically winding
and braiding filaments at a third braid angle which is greater than
the second braid angle to form the tubular structure of the
diseased section.
39. The method of claim 38 wherein helically winding and braiding
filaments includes forming a tubular fixation section, tubular
branch section and tubular diseased section having the same free
state diameter.
40. The stent-graft of claim 31 wherein the density of the
filaments in the branch section is less than a density of the
filaments in the diseased section.
41. The stent-graft of claim 31 wherein the density of the
filaments in the branch section is equal to a density of the
filaments in the diseased section.
42. A method for implanting the stent-graft of claim 20, including:
providing the device in a radially compressed state; delivering the
device to the diseased vessel and positioning the fixation section
within the healthy first vessel portion, the branch section within
the vessel branch, and the diseased aorta section within the
diseased portion; and causing the device to radially self-expand
with the fixation section engaging the first vessel portion, the
branch section extending cross the vessel branch, and the diseased
section extending across and engaging the diseased vessel
portion.
43. An implantable medical device for treating a portion of a
patient's vessel having a branch, a first portion on a first side
of the branch, and a second portion on a second side of the branch,
including: a first section having a first porosity and comprising a
plurality filaments which are helically wound in a braided
configuration to form a tubular, radially compressible and
self-expandable structure, for engaging the first portion of the
vessel on the first side of the branch; a second section having a
second porosity and comprising a plurality filaments which are
helically wound in a braided configuration to form a tubular,
radially compressible and self-expandable structure, for engaging
the second portion of the vessel on the second side of the branch;
and a branch section having a third porosity which is less than at
least one of the first and second porosities and comprising a
radially compressible and expandable structure, for extending
across the branch and connecting the first and second sections
while allowing blood flow to the branch.
44. The implantable medical device of claim 43 wherein the
filaments of the branch section are helically wound in a braided
configuration to form a tubular, radially compressible and
self-expandable structure.
45. The implantable medical device of claim 44 wherein free state
diameters of the first section, second section and branch section
are equal to one another.
46. The implantable medical device of claim 44 wherein the second
section includes a radially-expandable and relatively low porosity
membrane coextensive with at least a portion of the length of the
self-expandable structure.
47. The implantable medical device of claim 46 wherein the second
section membrane is formed of braided filaments.
48. The implantable medical device of claim 47 wherein the second
section membrane is formed of filaments interbraided with one
another and the filaments of the self-expandable structure.
49. The implantable medical device of claim 46 wherein the first
section includes a radially-expandable and relatively low porosity
membrane coextensive with at least a portion of the length of the
self-expandable structure.
50. The implantable medical device of claim 49 wherein the first
section membrane is formed of braided filaments.
51. The implantable medical device of claim 50 wherein the first
section membrane is formed of filaments braided with one another
and the filaments of the self-expandable structure.
Description
REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application Serial No. 60/047,749, filed on May 27, 1997, and
entitled "Bifurcated Stent Graft".
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is a radially self-expanding stent and
stent-graft for treating bifurcated and other branched vessels of a
patient, and methods for manufacturing and implanting the stent and
stent-graft.
[0004] 2. Description of the Related Art
[0005] Medical prostheses frequently referred to as stents and
stent-grafts are well known and commercially available. These
devices are used within body vessels of humans and other animals
for a variety of medical applications. Stents and stent-grafts are,
for example, used to repair (i.e., treat) abdominal aortic
aneurysms. An abdominal aortic aneurysm is an enlarged (i.e.,
dilated) and weakened diseased area of the portion of the aorta
between the renal artery branch (i.e., the location at which the
renal arteries meet the aorta) and the iliac bifurcation (i.e., the
location downstream from the renal artery branch at which the aorta
branches or divides into the iliac arteries). Stenosis, a narrowing
and occlusion of the aorta typically caused by tissue buildup, also
is often present at these aneurysms. Aneurysms and stenosis at the
carotid artery bifurcation (i.e., the location at which the common
carotid artery branches into the internal carotid artery and the
external carotid artery) are also treated with stents and
stent-grafts.
[0006] The Parodi U.S. Pat. No. 5,591,229 is directed to an aortic
graft for repairing an abdominal aortic aneurysm. Briefly, the
graft includes an elongated tube having first and second ends, and
securing means for securing the first end of the tube to the aorta.
The securing means is an expandable thin-walled member with a
plurality of slots parallel to the longitudinal axis of the member.
The thin-walled member is configured for delivery in an unexpanded
and undeformed diameter state with an inflatable balloon within the
member. After being intraluminally delivered to the site of the
aneurysm, the balloon is inflated to radially extend the
thin-walled member to an expanded and deformed diameter state. The
first end of the thin-walled member is thereby secured to the
aorta. Deflation of the balloon causes it to be disengaged from the
thin-walled member and permits its withdrawal.
[0007] A graft for treating an aneurysm which extends above the
renal arteries is shown in FIG. 7 of the Parodi patent. This graft
includes a thin-walled securing member which is interconnected to
the tube by at least one flexible connector member. The flexible
connector member spans the part of the aorta adjacent the renal
arteries so that blood flow through the renal arteries is not
obstructed.
[0008] There remains, however, a continuing need for stents and
stent-grafts for treating branched vessels. Improved stents and
stent-grafts for treating abdominal aortic aneurysms and/or
stenosis at the carotid artery bifurcation would be especially
useful. For example, stents and stent-grafts capable of remaining
fixed within a branched vessel as the diseased area of the vessel
expands would be desirable. Since accurately positioning a stent
and stent-graft in a branched vessel can be challenging, a device
of this type that can be relatively easily repositioned would also
be desirable. In general, stents and stent-grafts having different
characteristics enable medical personnel to select a device most
suitable for the treatment of the particular indication of the
patient.
SUMMARY OF THE INVENTION
[0009] The present invention is an implantable medical device for
treating a portion of a patient's vessel having a branch, a first
portion upstream from the branch, and a second portion downstream
from the branch. One embodiment of the device includes a first or
upstream section, a second or downstream section and a branch
section. The upstream section has a first porosity and comprises a
plurality filaments which are helically wound and interwoven in a
braided configuration to form a tubular, radially compressible and
self-expandable structure. The upstream section engages the first
portion of the vessel upstream from the branch when in an expanded
state. The downstream section has a second porosity and comprises a
plurality filaments which are helically wound and interwoven in a
braided configuration to form a tubular, radially compressible and
self-expandable structure. The downstream section engages the
downstream portion of the vessel downstream from the branch when in
an expanded state. The branch section has a third porosity which is
greater than at least one of the first and second porosities, and
comprises a radially compressible and expandable structure. When
implanted, the branch section extends across the branch to connect
the upstream and downstream sections while allowing blood flow from
the first portion of the vessel to the branch. The device can be
used to efficaciously treat indications such as aneurysms in the
abdominal aorta and stenosis near the carotid artery
bifurcation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an illustration of a portion of an aorta in which
stents and stent-grafts in accordance with the present invention
can be implanted.
[0011] FIG. 2 is an illustration of a stent in accordance with a
first embodiment of the present invention.
[0012] FIG. 3 is a detailed illustration of a portion of the stent
shown in FIG. 2, showing one of the filaments of the renal artery
branch section wound around a filament of the fixation section.
[0013] FIG. 4 is an illustration of the stent shown in FIG. 2 after
implantation in the portion of the aorta shown in FIG. 1.
[0014] FIG. 5 is an illustration of a stent in accordance with a
second embodiment of the present invention.
[0015] FIG. 6 is an illustration of a stent in accordance with a
third embodiment of the present invention.
[0016] FIG. 7 is an illustration of a stent-graft in accordance
with a fourth embodiment of the present invention.
[0017] FIG. 8 is an illustration of a stent-graft in accordance
with a fifth embodiment of the present invention.
[0018] FIG. 9 is an illustration of a stent-graft in accordance
with a sixth embodiment of the present invention.
[0019] FIG. 10 is an illustration of a portion of a carotid artery
in which stents and stent-grafts in accordance with the present
invention can be implanted.
[0020] FIG. 11 is an illustration of a stent-graft in accordance
with a seventh embodiment of the present invention.
[0021] FIG. 12 is an illustration of the stent-graft shown in FIG.
11 after implantation in the portion of the carotid artery shown in
FIG. 10.
[0022] FIG. 13 is an illustration of a stent-graft in accordance
with an eighth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] FIG. 1 is an illustration of a section of a diseased
abdominal aorta 12 which can be treated by the aortic stent and
stent-graft of the present invention. As shown, renal arteries 14A
and 14B extend from the aorta 12 at renal artery branch 16.
Downstream from (i.e., on a first side of) the renal artery branch
16 is the iliac bifurcation 20 at which the aorta 12 divides (i.e.,
branches) into iliac arteries 18A and 18B. The stent and
stent-graft of the present invention can be used to treat a
diseased portion 26 of the aorta 12 which is located between the
renal artery branch 16 and the iliac bifurcation 20. The diseased
portion 26 is represented in FIG. 1 by an aneurysm, (i.e., a
weakened and expanded-diameter section). Although not shown in FIG.
1, the aneurysm or other disease attributes (i.e., indications) of
the aorta 12 being treated can extend all the way to the renal
arteries 14A and 14B, and/or beyond the iliac bifurcation 20 into
the iliac arteries 18A and/or 18B. As described in greater detail
below, the stent and stent-graft of the present invention can make
use of a portion 24 of the aorta 12 which is typically relatively
healthy, and located upstream from the renal artery branch 16
(i.e., on a second side of the renal artery branch and opposite the
branch from the diseased portion 26). Arrows 22 are included in
FIG. 1 to illustrate the direction of blood flow through the aorta
12, renal arteries 14A and 14B and iliac arteries 18A and 18B.
[0024] Aortic stent 10, a first embodiment of the present
invention, is shown in FIG. 2. Stent 10 is a tubular device and
includes an upstream or fixation section 30, renal artery branch
section 32 and downstream or diseased aorta section 34. Fixation
section 30 and diseased aorta section 34 are formed from two sets
of oppositely-directed, parallel, spaced-apart and helically wound
elongated strands or filaments 36. The sets of filaments 36 are
interwoven in an over and under braided configuration intersecting
at points to form an open mesh or weave construction. Methods for
fabricating stent structures such as fixation section 30 and
diseased aorta section 34 are generally known and disclosed, for
example, in the Wallsten U.S. Pat. No. 4,655,771 and the Wallsten
et al. U.S. Pat. No. 5,061,275, which are hereby incorporated by
reference in their entirety for all purposes. In the embodiment of
stent 10 shown in FIG. 2, the fixation section 30 and diseased
aorta section 34 are formed from structures which are substantially
similar with the exception of their length. Other embodiments of
the invention described below include fixation and diseased aorta
sections which are formed from stent structures having different
characteristics.
[0025] Renal artery branch section 32 is formed by filaments 38
which have their opposite ends 40 connected to filaments 36 of the
fixation section 30 and diseased aorta section 34. Six filaments 38
(only four are visible) which are parallel to the longitudinal axis
and equally spaced around the circumference of the stent 10 are
shown in FIG. 2. As perhaps best shown in FIG. 3, the opposite ends
40 of the filaments 38 are connected to the fixation section 30 and
diseased aorta section 34 by being wound around the filaments 36 of
the fixation and diseased aorta sections. The ends 40 of the wound
filaments 38 can extend at an acute angle with respect to a
longitudinal axis of the stent 10, and toward the diseased aorta
section 34, to form a barb which can help anchor the stent 10 to
the aorta 12 or other vessel in which the stent is implanted. In
other embodiments (not shown) the filaments 38 of the renal artery
branch section 32 can be attached to the fixation section 30 and
diseased aorta section 34 by other known or methods such as
welding. As is evident from FIG. 2, the porosity of the renal
artery branch section 32 is greater that that of the fixation
section 30 and the diseased aorta section 34 (i.e., the density of
the filaments 36 in the fixation and diseased aorta sections is
greater than the density of the filaments 30 in the renal artery
branch section).
[0026] Stent 10 is shown in its expanded or relaxed state in FIG.
2, i.e., in the configuration it assumes when subjected to no
external loads or stresses. The filaments 36 are resilient,
permitting the radial compression of the fixation section 30 and
diseased aorta section 34 of stent 10 into a reduced-radius,
extended-length configuration or state. The renal artery branch
section 32 can also be radially compressed into a reduced-radius
configuration or state along with the fixation section 30 and
diseased aorta section 34, thereby rendering the stent 10 suitable
for delivery to the diseased aorta treatment site through a body
vessel (i.e., transluminally). Stent 10 is also self-expandable
from the compressed state, and axially flexible.
[0027] A wide variety of materials can be used for the
self-expanding stent filaments 36 and 38. Commonly used materials
include Elgiloy.RTM. and Phynox.RTM. spring alloys. Elgiloy.RTM.
alloy is available from Carpenter Technology Corporation of Reading
Pennsylvania. Phynox.RTM. alloy is available from Metal Imphy of
Imphy, France. Other materials used for self-expanding stent
filaments 36 and 38 are 316 stainless steel and MP35N alloy which
are available from Carpenter Technology Corporation and Latrobe
Steel Company of Latrobe, Pa. and superelastic Nitinol alloy which
is available from Shape Memory Applications of Santa Clara,
Calif.
[0028] Conventional or otherwise known devices for delivering
self-expanding stents can be used to deliver stent 10 to a diseased
aorta 12. Delivery devices of these types are, for example,
disclosed in the Wallsten et al. U.S. Pat. No. 4,732,152, Burton et
al. U.S. Pat. No. 5,026,377, Heyn et al. U.S. Pat. No. 5,201,757
and Braunschweiler et al. U.S. Pat. No. 5,484,444. Briefly, the
delivery devices (not shown) can include an elongated and flexible
inner tube having proximal and distal ends. The stent 10 is forced
into its reduced-radius compressed state around the distal end of
the inner tube, and constrained in the compressed state by an outer
tube which surrounds the inner tube and stent 10. A deployment
mechanism which can be actuated from the proximal end of the
delivery device retracts the outer tube with respect to the inner
tube, thereby allowing the stent 10 to self-expand into engagement
with the inner wall of the aorta 12.
[0029] The assembled delivery device is inserted percutaneously
into the femoral artery and directed through the artery until the
distal end with the constrained stent 10 is positioned at the
diseased portion 26 of the aorta 12. The deployment mechanism is
then actuated to allow the stent 10 to self-expand into engagement
with the aorta 12. FIG. 4 is an illustration of the stent 10
implanted into the aorta 12 shown in FIG. 1. As shown, fixation
section 30 is located at and engaged with the relatively healthy
portion 24 of the aorta 12 immediately opposite the renal arteries
14A and 14B from the iliac branch 20. Renal artery branch section
32 is located at the renal artery branch 16 and extends across the
locations at which the renal arteries 14A and 14B open into the
aorta 12. The diseased aorta section 34 of the stent 10 extends
across the diseased portion 26 of the aorta 12, and therefore
provides additional strength for this vessel. In a similar manner,
the support provided by diseased aorta section 34 can help maintain
a diseased aorta open in the presence of stenosis (not shown in
FIGS. 1 and 2) which would otherwise reduce the blood flow
capabilities of the vessel.
[0030] In the embodiment shown in FIG. 4, the diseased aorta
section 34 of stent 10 extends from a location immediately
downstream from the renal arteries 14A and 14B to a location
immediately adjacent to the iliac arteries 18A and 18B. A first end
42 of the diseased aorta section 34 adjacent to the renal artery
branch section 32 is expanded radially outwardly into engagement
with the inner walls of the aorta 12 adjacent to the renal arteries
14A and 14B. A second end 44 of the diseased aorta section 36 is
expanded radially outwardly into engagement with the inner walls of
the aorta 12 adjacent to the location at which the iliac arteries
18A and 18B intersect the aorta. As shown, the diseased portion 26
of aorta 12 between the portions at which ends 42 and 44 of the
section 34 engage the aorta (i.e., the aneurysm) is weakened and
extends outwardly beyond the stent 10. Under this and other similar
conditions the amount of anchoring support provided by the
relatively small surface area engagement of the ends 42 and 44 with
the diseased portion 26 of the aorta 12 may not be sufficient to
securely maintain the stent section 34 in its implanted
position.
[0031] Fixation section 30 of the stent 10, through its engagement
with the relatively healthy portion 24 of the aorta 12 and its
interconnection to the diseased aorta section 34 by filaments 38,
provides substantial anchoring support for the diseased aorta
section. The fixation section 30 thereby enhances the positional
stability of the implanted diseased aorta section 34. This enhanced
positional stability is achieved without substantially restricting
blood flow to the renal arteries 14A and 14B since the material
density of the renal artery branch section 34 (i.e., the density of
filaments 38 of stent 10) is relatively low. As used in this
document, the term "porosity" also refers to the density or spacing
of the filaments 38 (e.g., the amount of open space between the
filaments with respect to the amount of space occupied by the
filaments). Additional anchoring support for the stent 10 is
provided by the barbed-type ends 40 of filaments 38 which engage
the interior wall of the aorta 12.
[0032] A stent 10 for implantation in the aorta 12 of an average
size adult patient can be between about 5 cm and 15 cm in length,
and have an expanded state diameter between about 2 cm and 5 cm.
The fixation section 30 can be between about 1 cm and 5 cm in
length. The renal artery branch section 32 can be between about 1
cm and 5 cm in length. The diseased aorta section 34 can be between
about 4 cm and 15 cm in length. These dimensional ranges can of
course be larger and smaller to accommodate the anatomy of larger
and smaller patients.
[0033] Features and characteristics of the fixation section 30 can
be varied to change the amount of anchoring support being provided.
For example, the amount of anchoring support will increase with
increasing length of the fixation section 30 (due to increased
surface area of engagement), with increasing braid angle .theta. of
filaments 36 (illustrated in FIG. 2, due to increased radial force
generated by the section), and with increasing diameter (e.g., an
outwardly flared end) and/or stiffness of filaments 36 (due to
increased radial force of the section). Conversely, these and other
characteristics of the fixation section can be decreased or
otherwise varied to decrease the amount of anchoring support
provided by the fixation section 30. The force exerted by the
fixation section 30 on the aorta, and therefore the amount of
anchoring support being provided, is the summation of the radial
pressure exerted over the surface area of the section. The amount
of anchoring support can therefore be varied by changing the radial
pressure and surface area characteristics of the fixation section
30.
[0034] The amount of anchoring support to be provided by the
fixation section 30, and the features and characteristics of the
fixation section to provide the support, can be optimized and
selected to suit the indications of the particular diseased aorta
12 in which the stent 10 is to be implanted. For example, the
relative amount of anchoring support to be provided by the fixation
section 30 will often depend upon the amount of positional support
that the diseased aorta section 34 is capable of generating in
connection with the aorta 12 in which it is implanted. In the
example shown in FIG. 4, for example, the diseased aorta section 34
generates at least some anchoring support where its ends 42 and 44
engage the aorta 12. Diseased aortas that are relatively more or
less healthy than that shown at 12 in FIG. 4 may be suitable for
use with stents 10 having a fixation section 30 which provides less
or more anchoring support, respectively, than the fixation section
shown in FIG. 4. The manner by which the fixation section 30 is
configured to provide the desired amount of anchoring support can
depend on the nature (e.g., relative health) of the portion 24 of
the aorta 12 in which the fixation section is to be implanted. For
example, if the portion 24 of aorta 12 in which the fixation
section 30 is to be implanted-is relatively weak, it may be
advantageous to provide a fixation section which generates
relatively low radial forces, but which is relatively long to
achieve the desired anchoring support.
[0035] Stent 210, a second embodiment of the present invention, is
illustrated in FIG. 5. Features of stent 210 which are similar to
those of stent 10 shown in FIG. 2 are indicated by like reference
numbers, and have similar characteristics. As shown, the stent 210
includes fixation section 230, renal artery branch section 232 and
diseased aorta section 234. Sections 230, 232 and 234 are all
formed from self-expanding, braided filament stent structures of
the type described above. Stent 210 can be manufactured from a
unitary braided filament stent structure by cutting and removing
selected filaments from the portion of the structure to form the
renal artery branch section 232. The density of the braided
filaments 236 in the renal artery branch section 232 is thereby
reduced from the density of the filaments in the fixation section
230 and the diseased aorta section 234. By way of example, stents
such as 210 can be formed from thirty-eight to ninety-six filaments
236 (each of which is an individual wire and/or a pair of wires),
with fifty to seventy-five percent of these filaments being cut and
removed from the original structure to form the renal artery branch
section 232. Stent 210 can be implanted in a manner similar to that
of stent 10 and described above.
[0036] Stent 310, a third embodiment of the present invention, is
illustrated in FIG. 6. Features of stent 310 which are similar to
those of stent 10 shown in FIG. 2 are indicated by like reference
numbers, and will have similar characteristics. As shown, the stent
310 includes fixation section 330, renal artery branch section 332
and diseased aorta section 334. Sections 330, 332 and 334 are all
formed from self-expanding, braided filament stent structures of
the type described above. The braid angle .theta. of the filaments
336 (and therefore the density and radial force)of the fixation
section 330 is greater than the braid angle .theta. of the
filaments in the renal artery branch section 332 and the diseased
aorta section 334. In the embodiment shown, the braid angle .theta.
of the filaments 336 in the renal artery branch section 332 and the
diseased aorta section 334 are substantially similar. Stent 310 can
be manufactured as a unitary braided filament structure by changing
the braid angle during manufacture at the location corresponding to
the intersection of the renal artery branch section 332 and the
fixation section 330. The braid angle can also be changed by
changing the braiding mandrel diameter, and by heat treating the
stent at a given diameter. Stent 310 can be implanted in a patient
in a manner similar to that of stent 10 and described above.
[0037] Stent-graft 410, a fourth embodiment of the present
invention, is illustrated in FIG. 7. Many features of stent-graft
410, and in particular fixation section 430 and renal artery branch
section 432, are similar to those of stent 10 described above, are
indicated by like reference numbers, and will have similar
characteristics. A primary difference between stent 10 and
stent-graft 410 is that the stent-graft includes a tubular graft
cover 450 incorporated on the diseased aorta section 434. The
illustrated embodiment of stent-graft 410 includes a diseased aorta
section 434 formed from a braided filament stent structure of the
type described above with reference to stent 10, and a separately
fabricated graft cover 450 which is attached to the stent structure
by adhesive, thread or filament stitching or other conventional
techniques. The braided filament stent structure provides the
radially self-expandable features and characteristics described
above, and thereby effectively functions as a support structure.
The tubular graft cover 450 effectively functions as a blood
flow-shunting lumen, thereby supplementing the functionality of the
portion of the aorta 12 in which the diseased aorta section 434 is
implanted. The tubular graft cover 450 is flexible and radially
collapsible. When the braided filament stent structure is in its
reduced-radius, compressed state, the graft cover 450 collapses,
enabling the stent-graft 410 to be mounted on a deployment
mechanism in the manner described above. The graft cover 450 is
forced into and supported in its tubular, blood flow-shunting shape
by the braided filament stent structure when the stent-graft 410 is
deployed.
[0038] Graft cover 450 can be any of a variety of structures which
have the characteristics described above (e.g., are flexible and
radially collapsible) and which are sufficiently non-porous to
shunt blood flow. Graft cover 450 can, for example, be formed from
relatively tightly braided filaments of polymers such as
polyethylene, polyethelyne terephalate and polyester. One suitable
high molecular weight polyethylene is sold under the brand name
"Spectra." A suitable PET material is commercially available under
the brand name "Dacron." Alternatively, graft cover 450 can be
formed from a sheet of material which is either itself impervious
to blood flow, or covered with a coating which renders the material
impervious; In still other embodiments, graft cover 450 is a film,
sheet or tube of biocompatible material such as ePTFE.
[0039] Other embodiments of graft cover 450 are formed by winding
or spinning an extruded fiber onto a mandrel. Materials and methods
for manufacturing graft covers 450 of these types are described in
the following U.S. Patents, all of which are hereby incorporated by
reference in their entirety: Wong, U.S. Pat. No. 4,475,972; Pinchuk
et al., U.S. Pat. No. 4,738,740; Pinchuk, U.S. Pat. No. 5,229,431;
and Dereume, U.S. Pat. No. 5,653,747.
[0040] Yet other embodiments of stent-graft 410 (not shown) include
a diseased aorta section 434 in which the graft cover 450 is formed
by multiple textile strands which are interbraided with each other
and the filaments 436 of the stent structure to effectively form a
composite stent and graft cover structure. Structures of these
types which can be incorporated into stent-graft 410, and
associated methods of manufacture, are described in European Patent
Publication EP 0 804 934, and commonly assigned U.S. application
Ser. No. 08/640,062, filed Apr. 30, 1996, Ser. No. 08/640,091,
filed Apr. 30, 1996, Ser. No. 08/946,906, filed Oct. 8, 1997, and
Ser. No. 08/988,725, filed Dec. 11, 1997, all of which are hereby
incorporated by reference in their entirety.
[0041] Stent-graft 510, a fifth embodiment of the present
invention, is illustrated in FIG. 8. Fixation section 530, renal
artery branch section 532 and the braided filament stent structure
of the diseased aorta section 534 are similar in structure and
characteristics to those of stent 210 described above, and are
indicated by like reference numbers. The graft cover 550 of
stent-graft 510 can be similar in structure and characteristics to
that of graft cover 450 of stent graft 410 described above. The
graft cover 550 can be incorporated on the diseased aorta section
534 in a manner similar to the manner described above by which
graft cover 450 is incorporated on the diseased aorta section 434
of stent-graft 410.
[0042] Stent-graft 610, a sixth embodiment of the present
invention, is illustrated in FIG. 9. Fixation section 630, renal
artery branch section 632 and the braided filament stent structure
of the diseased aorta section 634 are similar in structure and
characteristics to those of stent 310 described above, and are
indicated by like reference numbers. The graft cover 650 of
stent-graft 610 can be similar in structure and characteristics to
that of graft cover 450 of stent-graft 410 described above. The
graft cover 650 can be incorporated on the diseased aorta section
634 in a manner similar to the manner described above by which
graft cover 450 is incorporated on the diseased aorta section 434
of stent-graft 410.
[0043] Stent-grafts 430, 530 and 630 described above all include a
tubular diseased aorta section 434, 534 and 634, respectively.
Other embodiments of the invention (not shown) include bifurcated
diseased aorta sections. Self-expanding bifurcated stent-grafts
are, for example, described in the Alcime et al. U.S. Pat. No.
5,632,772, the Dereume et al. U.S. Pat. No. 5,639,278 and the
Thompson and Du U.S. patent application Ser. No. 60/047,749
entitled "Bifurcated Stent Graft." Bifurcated stent-grafts of these
types can be used for indications in which the aortic aneurysm
extends to the iliac bifurcation 20 (FIG. 1), or beyond the iliac
bifurcation and into one or both of the iliac arteries 18A and 18B.
Still other embodiments of the invention (also not shown) include
an aorto-monoiliac diseased aorta section. Aorto-monoiliac
stent-grafts of these types are used in connection with
femoro-femoral bypass surgical procedures.
[0044] FIG. 10 is an illustration of a portion of a carotid artery
80 which can be treated by the stent and stent-graft of the present
invention. As shown, the common carotid artery 82 divides into the
internal carotid artery 84 and the external carotid artery 86 at
the branch or bifurcation 88. The stent and stent-graft of the
present invention are configured to treat a diseased portion of
carotid artery 80 which is located adjacent to the bifurcation 88.
Often, the diseased portion of carotid artery 80 will include a
section of the common carotid artery 82 immediately upstream from
the bifurcation 88 and a portion of at least one of the internal
carotid artery 84 and the external carotid artery 86 immediately
downstream from the bifurcation. Arrows 90 are included in FIG. 10
to illustrate the direction of blood flow through the common
carotid artery 82 (an upstream portion) and the internal and
external carotid arteries 84 and 86, respectively (downstream
portions).
[0045] Stent-graft 710, a seventh embodiment of the present
invention, is illustrated in FIG. 11. As shown, stent-graft 710
includes an upstream section 730, a branch section 732 and a
downstream section 734. The braided filament stent structures of
stent-graft sections 730, 732 and 734 can be portions of a unitary
braided filament stent structure such as those described above, and
are similar in structure and characteristics. In a manner similar
to that of the fixation section 30 of stent 10 described above, the
features and characteristics of the braided filament stent
structures of upstream section 730 and/or downstream section 734
can be varied to change the amount of anchoring support being
provided by these sections.
[0046] Graft covers 750 and 751 are incorporated into the
downstream section 734 and upstream section 730, respectively, of
the stent-graft 710. The downstream section graft cover 750 and
upstream section graft cover 751 can be similar in structure and
characteristics to those of graft cover 450 of stent-graft 410
described above. These graft covers 750 and 751 have a relatively
low porosity (i.e., are microporous), so they substantially prevent
fluid flow after coagulation, but allow the exchange of nutrients.
The graft covers 750 and 751 also can be incorporated on the
upstream section 730 and downstream section 734 in a manner similar
to the manner described above by which the graft cover 450 is
incorporated on the section 434 of stent-graft 410. Since the graft
covers 750 and 751 have a relatively low porosity, the porosity of
the interwoven filaments 736 of the branch section 732 will be
relatively high with respect to the porosity of the downstream
section 734 and upstream section 730.
[0047] Stent-graft 710 can be mounted on a delivery device in a
manner similar to stent 10 described above. Similarly, the
assembled device is inserted percutaneously into the femoral,
brachial or radial artery and positioned and deployed like that of
stent 10 described above. FIG. 12 is an illustration of the
stent-graft 710 implanted into the portion of the carotid artery 80
shown in FIG. 10. As shown, upstream section 730 is located at and
engaged with the common carotid artery 82 immediately upstream from
the branch 88. Branch section 732 is located at the branch 88 and
extends across the location at which the external carotid artery 86
opens into the common carotid artery 82. The downstream section 734
of the stent-graft 710 is located at and engaged with the internal
carotid artery 84 immediately downstream from the branch 88.
Sections 730 and 734 of the stent-graft 710 function as blood
flow-shunting lumens to supplement the functionality of the
portions of the arteries 82 and 84, respectively, in which they are
implanted. The relatively high porosity branch section 732,
however, allows a portion of the blood flow through the common
carotid artery 82 to flow into the external carotid artery 86.
Stent-graft 710 thereby effectively functions as a pseudobifurcated
device.
[0048] Stent-graft 810, an eighth embodiment of the present
invention, is illustrated in FIG. 13. Upstream section 830, branch
section 832 and downstream section 834 are similar in structure and
characteristics to those of stent-graft 710 described above, and
are indicated by like reference numbers. Stent-graft 810 can be
implanted in a manner similar to that of stent-graft 710 described
above. A primary difference between stent-grafts 710 and 810 is
that branch section 832 of stent-graft 810 includes a graft cover
portion 853 with an aperture 855. In the embodiment shown, graft
cover portion 853 is a section of a unitary graft cover which also
includes portions 850 and 851 on the downstream section 834 and
upstream section 830, respectively, of the stent-graft 810.
Stent-graft 810 can be implanted in a manner similar to that of
stent-graft 710 described above, with the aperture 855 aligned with
the intersection of the common carotid artery 82 and either the
internal or external carotid artery 84 or 86, respectively, to
function as a pseudobifurcated device.
[0049] Stents and stent-grafts in accordance with the present
invention offer a number of important advantages. They have the
potential to be highly efficacious, especially in severely diseased
aortas and carotid arteries that may not otherwise be capable of
receiving conventional stents or stent-grafts. They can be
manufactured so as to have selected ones of a wide range of
characteristics, thereby enhancing the range of indications for
which they can be used. The self-expanding properties of the
devices provides a structure that is dynamically compliant. The
stent and stent-graft can therefore expand and contract with
fluctuations in the diameter of the vessels in which they are
implanted. Stress shielding of the host tissue and associated
complications such as degeneration and necrosis can thereby be
reduced with respect to that caused by balloon expandable or other
relatively rigid devices. The dynamic compliance also enables the
device to change diameter over time with the vessel. For example,
if the aneurysmal disease spreads to the fixation section of the
vessel, the self-expanding device can continue to conform to the
shape of the vessel wall. In contrast, rigid devices will remain at
a fixed diameter and may not continue to engage the more recently
diseased vessel portions. The self-expanding nature of the device
also allows it to be reconstrained and repositioned by a
development device. Since accurate placement of the device can be
challenging, the ability to reposition the device enhances its
usefulness.
[0050] Although the present invention has been described with
reference to preferred embodiments, those skilled in the art will
recognize that changes can be made in form and detail without
departing spirit and scope of the invention.
* * * * *