U.S. patent application number 17/063092 was filed with the patent office on 2021-01-21 for low profile non-symmetrical stent.
This patent application is currently assigned to COOK MEDICAL TECHNOLOGIES LLC. The applicant listed for this patent is COOK MEDICAL TECHNOLOGIES LLC. Invention is credited to David Brocker, William K. Dierking, Jarin A. Kratzberg, Alan R. Leewood, Erik E. Rasmussen, Blayne A. Roeder.
Application Number | 20210015643 17/063092 |
Document ID | / |
Family ID | 1000005131949 |
Filed Date | 2021-01-21 |
View All Diagrams
United States Patent
Application |
20210015643 |
Kind Code |
A1 |
Brocker; David ; et
al. |
January 21, 2021 |
LOW PROFILE NON-SYMMETRICAL STENT
Abstract
Various stents and stent-graft systems for treatment of medical
conditions are disclosed. In one embodiment, an exemplary
stent-graft system may be used for endovascular treatment of a
thoracic aortic aneurysm. The stent-graft system may comprise
proximal and distal components, each comprising a graft having
proximal and distal ends, where upon deployment the proximal and
distal components at least partially overlap with one another to
provide a fluid passageway therebetween. The proximal component may
comprise a proximal stent having a plurality of proximal and distal
apices connected by a plurality of generally straight portions,
where a radius of curvature of at least one of the proximal apices
may be greater than the radius of curvature of at least one of the
distal apices. The distal component may comprise a proximal z-stent
coupled to the graft, where the proximal end of the graft comprises
at least scallop formed therein that generally follows the shape of
the proximal z-stent. Further, the distal component may comprise at
least one z-stent stent coupled to the distal end of the graft and
extending distally therefrom that reduces proximal migration of the
distal component.
Inventors: |
Brocker; David; (Carmel,
IN) ; Dierking; William K.; (Louisville, KY) ;
Leewood; Alan R.; (Lafayette, IN) ; Roeder; Blayne
A.; (Bloomington, IN) ; Kratzberg; Jarin A.;
(West Lafayette, IN) ; Rasmussen; Erik E.;
(Slagelse, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COOK MEDICAL TECHNOLOGIES LLC |
BLOOMINGTON |
IN |
US |
|
|
Assignee: |
COOK MEDICAL TECHNOLOGIES
LLC
BLOOMINGTON
IN
|
Family ID: |
1000005131949 |
Appl. No.: |
17/063092 |
Filed: |
October 5, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15982523 |
May 17, 2018 |
10828183 |
|
|
17063092 |
|
|
|
|
14952498 |
Nov 25, 2015 |
9980834 |
|
|
15982523 |
|
|
|
|
12904452 |
Oct 14, 2010 |
9226813 |
|
|
14952498 |
|
|
|
|
12332904 |
Dec 11, 2008 |
9180030 |
|
|
12904452 |
|
|
|
|
61016753 |
Dec 26, 2007 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2230/005 20130101;
A61F 2/848 20130101; A61F 2002/8483 20130101; A61F 2/915 20130101;
A61F 2210/0014 20130101; A61F 2002/91516 20130101; A61F 2002/8486
20130101; A61F 2002/91541 20130101; A61F 2002/075 20130101; A61F
2220/0075 20130101; A61F 2002/061 20130101; A61F 2002/826 20130101;
A61F 2/852 20130101; A61F 2230/0067 20130101; A61F 2002/91533
20130101; A61F 2220/0016 20130101; A61F 2/07 20130101; A61F 2/856
20130101; A61F 2002/91508 20130101; A61F 2002/065 20130101; A61F
2250/006 20130101; A61F 2230/0054 20130101; A61F 2/89 20130101 |
International
Class: |
A61F 2/89 20060101
A61F002/89; A61F 2/915 20060101 A61F002/915; A61F 2/07 20060101
A61F002/07 |
Claims
1-20. (canceled)
21. A stent-graft system for treatment of a medical condition, the
stent-graft system comprising: a proximal component comprising a
graft having proximal and distal ends, and further comprising a
stent having a plurality of proximal and distal apices connected by
a plurality of generally straight portions, where at least one of
the distal apices of the stent is attached to the graft using one
or more sutures, where each proximal apex comprises a first curved
portion and each distal apex comprises a second curved portion,
where the first curved portion and the second curved portion each
comprises at least one radius of curvature, and the radius of
curvature of at least one of the proximal apices is greater than
the radius of curvature of at least one of the distal apices; and a
distal component comprising a graft having proximal and distal
ends, where, upon deployment, the proximal and distal components at
least partially overlap with one another to permit continuous fluid
flow therebetween, where a first radius of curvature of one of the
proximal apices is greater than 1.5 mm.
22. The stent-graft system of claim 21 where the first radius of
curvature of one of the proximal apices is at least two times
greater than the radius of curvature of at least one of the distal
apices.
23. The stent-graft system of claim 21, where the distal component
further comprises a proximal z-stent coupled to the graft, and
where the proximal end of the graft comprises at least one scallop
formed therein that generally follows the shape of the proximal
z-stent.
24. The stent-graft system of claim 21, where the distal component
further comprises at least one z-stent stent coupled to the distal
end of the graft and extending distally therefrom that reduces
proximal migration of the distal end of the distal component.
25. The stent-graft system of claim 24, wherein the at least one
z-stent stent coupled to the distal end of the graft comprises at
least one barb oriented in a proximal direction.
26. The stent-graft system of claim 21 where each of the proximal
apices of the stent are circumferentially offset from the distal
apices.
27. The stent-graft system of claim 21 where the stent is a
proximal stent, and where the proximal component comprises at least
five additional z-stents coupled to the graft at locations distal
to the proximal stent.
28. The stent-graft system of claim 27 where, of the at least five
additional z-stents, proximal and distal z-stents are coupled to an
inner surface of the graft and at least three intermediate z-stents
are coupled to an outer surface of the graft.
29. A stent-graft system for treatment of a medical condition, the
stent-graft system comprising: a proximal component comprising a
graft having proximal and distal ends, and further comprising a
first stent having a plurality of proximal and distal apices
connected by a plurality of generally straight portions, where at
least one of the distal apices of the first stent is attached to
the graft using one or more sutures, where each proximal apex
comprises a first curved portion and each distal apex comprises a
second curved portion, where the first curved portion and the
second curved portion each comprises at least one radius of
curvature, and the radius of curvature of at least one of the
proximal apices is greater than the radius of curvature of at least
one of the distal apices; and a distal component comprising a graft
having proximal and distal ends, where, upon deployment, the
proximal and distal components at least partially overlap with one
another to provide a fluid passageway therebetween, where one of
the proximal apices comprises a first radius of curvature, where a
second radius of curvature of one of the distal apices is from
about 0.6 mm to about 1.5 mm, and where a ratio of the second
radius of curvature to the first radius of curvature is about 1:2.6
to about 1:18.
30. The stent-graft system of claim 29 where the distal component
further comprises a proximal z-stent coupled to the graft, and
where the proximal end of the graft comprises at least one scallop
formed therein that generally follows the shape of the proximal
z-stent.
31. The stent-graft system of claim 29 where each of the proximal
apices of the first stent are circumferentially offset from the
distal apices.
32. The stent-graft system of claim 29 where the proximal component
comprises at least five additional z-stents coupled to the graft at
locations distal to the first stent.
33. The stent-graft system of claim 29 where the first radius of
curvature is about 1 mm, and the second radius of curvature is
about 6 mm.
34. A stent-graft system for treatment of a medical condition, the
stent-graft system comprising: a proximal component comprising a
graft having proximal and distal ends, and further comprising a
stent having a plurality of proximal and distal apices connected by
a plurality of generally straight portions, where at least one of
the distal apices of the stent is attached to the graft using one
or more sutures, where each proximal apex comprises a first curved
portion and each distal apex comprises a second curved portion,
where the first curved portion and the second curved portion each
comprises at least one radius of curvature, and the radius of
curvature of at least one of the proximal apices is greater than
the radius of curvature of at least one of the distal apices; and a
distal component comprising a graft having proximal and distal
ends, where, upon deployment, the proximal and distal components at
least partially overlap with one another to provide a fluid
passageway therebetween, where a first radius of curvature of one
of the distal apices of the stent is at least two times less than a
second radius of curvature of one of the proximal apices.
35. The stent-graft system of claim 34 where a ratio of the first
radius of curvature to the second radius of curvature is about
1:2.6 to about 1:18.
36. The stent-graft system of claim 34 where each of the proximal
apices of the stent are circumferentially offset from the distal
apices.
37. The stent-graft system of claim 34 where the distal component
further comprises a proximal z-stent coupled to the graft, and
where the proximal end of the graft comprises at least one scallop
formed therein that generally follows the shape of the proximal
z-stent.
38. The stent-graft system of claim 34 where the at least one
z-stent stent coupled to the distal end of the graft comprises at
least one barb oriented in a proximal direction.
39. The stent-graft system of claim 34 where the first radius of
curvature is about 1 mm, and the second radius of curvature is
about 6 mm.
40. The stent-graft system of claim 34 where the stent is a
proximal stent, and where the proximal component comprises at least
five additional z-stents coupled to the graft at locations distal
to the proximal stent.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Utility
patent application Ser. No. 12/841,807, filed Jul. 22, 2010 and
entitled "Apparatus and Methods for Deployment of a Modular
Stent-Graft System," which is a continuation-in-part of U.S.
Utility patent application Ser. No. 12/622,351, filed Nov. 19, 2009
and entitled "Low Profile Non-Symmetrical Stent," which claims
priority to U.S. Provisional Application Ser. No. 61/016,753, filed
Dec. 26, 2007, co-pending U.S. patent application Ser. No.
12/332,904, filed Dec. 11, 2008 and Ser. No. 12/472,082, filed May
26, 2009, and co-pending Great Britain Patent Application Nos.
GB0920235.9, filed Nov. 18, 2009 and GB0920327.4, filed Nov. 19,
2009, each of which is incorporated herein by reference in its
entirety.
BACKGROUND
[0002] The present invention relates generally to stents for use in
body vessels to treat medical conditions. In particular, this
invention relates to an asymmetric stent having opposing sets of
curved apices, where the curved section of one set of apices has a
radius of curvature that is greater than the curved section of the
other set of apices, and may present a lower profile, better
compliance with irregular vascular geometry, and higher sealing
forces than conventional stents.
[0003] Stents may be inserted into an anatomical vessel or duct for
various purposes. Stents may maintain or restore patency in a
formerly blocked or constricted passageway, for example, following
a balloon angioplasty procedure. Other stents may be used for
different procedures, for example, stents placed in or about a
graft have been used to hold the graft in an open configuration to
treat an aneurysm. Additionally, stents coupled to one or both ends
of a graft may extend proximally or distally away from the graft to
engage a healthy portion of a vessel wall away from a diseased
portion of an aneurysm to provide endovascular graft fixation.
[0004] Stents may be either self-expanding or balloon-expandable,
or they can have characteristics of both types of stents. Various
existing self-expanding and balloon-expandable stent designs and
configurations comprise generally symmetrical end regions including
one or more apices formed of nitinol or another alloy wire formed
into a ring. The apices commonly comprise relatively acute bends or
present somewhat pointed surfaces, which may facilitate compression
of the stent to a relatively small delivery profile due to the
tight bend of the apices. Although having this advantage, in some
situations, such relatively acute or pointed apices may be
undesirable, in particular in vessel anatomies that are curved or
tortuous such as, for example, the thoracic aorta.
[0005] The thoracic aorta presents a challenging anatomy for stent
grafts used to treat thoracic aneurysms or dissections. The
thoracic aorta comprises a curve known as the aortic arch, which
extends between the ascending thoracic aorta (closet to the heart)
and the descending thoracic aorta (which extends toward the
abdominal aorta). Thoracic stent grafts are used to exclude
thoracic aortic aneurysms. A stent graft's ability to conform to
the tortuous anatomy of the aortic arch is a major concern. Current
designs sometimes lack the desired sealing ability at the proximal
end of the stent graft (closest to the heart). Also, current
thoracic devices present a relatively large profile which, with
some patients' anatomies may be problematic. Finally, many current
stents have relatively acute points that may prevent them from
being used in the aortic arch for fear of undesirable interaction
with the artery wall after an extended amount of time in the
patient.
[0006] Therefore, a generally nonsymmetrical stent having at least
one relatively rounded apex that is less invasive in an expanded
state than stents with more acute apices may alleviate the above
problems, while providing an improved compliance to the aortic arch
and increased radial force if used as a sealing and/or alignment
stent, as well as a desirable ability to be crimped to a readily
introducible diameter.
[0007] As one particular example, type-A thoracic aortic dissection
(TAD-A) is a condition in which the intimal layer of the ascending
thoracic aorta develops a tear, allowing blood to flow into the
layers of the aortic wall, causing the development of a medial or
subintimal hematoma. TAD-A is associated with a strikingly high
mortality rate (about one-fourth to one-half of victims die within
the first 24-48 hours). The only current treatment for TAD-A is
open surgery, where the chest is opened, the aorta is clamped, and
a vascular prosthesis is sewn in place. Operative mortality rate
for this procedure may be around 10%. Endovascular treatment of
TAD-B (which affects the descending thoracic aorta) has been
effective in reducing short-term and longer term mortality.
Therefore, it is desirable to provide an endovascular device
configured to address the anatomic challenges of the thoracic
aorta.
SUMMARY
[0008] Various stents and stent-graft systems for treatment of
medical conditions are disclosed. In one embodiment, an exemplary
stent-graft system may be used for endovascular treatment of a
thoracic aortic aneurysm.
[0009] The stent-graft system may comprise proximal and distal
components, each comprising a graft having proximal and distal
ends, where upon deployment the proximal and distal components at
least partially overlap with one another to provide a fluid
passageway therebetween. The proximal component may comprise a
proximal stent having a plurality of proximal and distal apices
connected by a plurality of generally straight portions, where a
radius of curvature of at least one of the proximal apices may be
greater than the radius of curvature of at least one of the distal
apices.
[0010] The distal component may comprise a proximal z-stent coupled
to the graft, where the proximal end of the graft comprises at
least scallop formed therein that generally follows the shape of
the proximal z-stent. Further, the distal component may comprise at
least one z-stent coupled to the distal end of the graft and
extending distally therefrom that reduces proximal migration of the
distal component.
[0011] Advantageously, when the stent graft system is deployed, the
proximal stent of the proximal component will maximize the efficacy
of the proximal seal while reducing atraumatic contact with an
artery wall, and further preventing distal migration of the
proximal end of the proximal component. Further, the at least one
scallop may advantageously reduce the potential for graft
infolding, thereby reducing or eliminating the likelihood of
impeded blood flow and/or endoleaks around the distal
component.
[0012] Other systems, methods, features and advantages of the
invention will be, or will become, apparent to one with skill in
the art upon examination of the following figures and detailed
description. It is intended that all such additional systems,
methods, features and advantages be within the scope of the
invention, and be encompassed by the following claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention can be better understood with reference to the
following drawings and description. The components in the figures
are not necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. Moreover, in the
figures, like referenced numerals designate corresponding parts
throughout the different views.
[0014] FIGS. 1-3 show different views of a symmetrical stent;
[0015] FIG. 4 depicts an example of an asymmetric stent;
[0016] FIG. 5 diagrammatically illustrates the asymmetrical radii
of curvature of the stent of FIG. 4;
[0017] FIG. 6 shows the stent of FIG. 4 in a simulated artery;
[0018] FIG. 7 depicts another example of an asymmetric stent;
[0019] FIG. 8 diagrammatically illustrates the asymmetrical radii
of curvature of yet another example of a stent;
[0020] FIG. 9 shows the stent of FIG. 8 in a simulated artery;
[0021] FIG. 10 shows an end view of still another example of an
asymmetric stent;
[0022] FIG. 11 shows a side view of the stent of FIG. 10;
[0023] FIG. 12 is a top perspective view of the stent of FIG.
10;
[0024] FIG. 13 shows the stent of FIG. 10 in a simulated
artery;
[0025] FIG. 14 is a partial perspective of a stent-graft
incorporating the stent of FIG. 10;
[0026] FIG. 15 illustrates a side view of the stent-graft of FIG.
14;
[0027] FIGS. 16-18 show a stent-graft with side branches; and
[0028] FIG. 19 is a side view of a stent-graft device configured
for endovascular treatment of a thoracic aorta dissection.
[0029] FIG. 20 is a side view of a stent-graft configured for
endovascular treatment of a thoracic aortic aneurysm.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] The present invention relates generally to stents for use in
body vessels to treat medical conditions. In particular, this
invention relates to a novel asymmetric stent having opposing sets
of curved apices, where the curved section of one set of apices has
a radius of curvature that is greater than the curved section of
the other set of apices, and may present a lower profile than
conventional stents. The lower profile may present advantages for
use in patients with particularly tortuous or small-diameter
vessels.
[0031] In the present application, the term "proximal" refers to a
direction that is generally closest to the heart during a medical
procedure, while the term "distal" refers to a direction that is
furthest from the heart during a medical procedure. Reference
throughout is made to proximal and distal apices, but those of
skill in the art will appreciate that the proximal-distal
orientation of stents of the present invention may be reversed
without exceeding the scope of the present invention.
[0032] As shown in FIGS. 4-15, this novel stent is not symmetrical
like many commercially available stents, in that the radius of
curvature of the opposing proximal and distal apices is different
between the top and bottom of the stent. The stents may be attached
to either end of a stent graft to provide sealing and may be used
internally or externally to the graft material to provide support
to the graft.
[0033] The asymmetric stent may be configured such that, when used
with a graft, it will provide a sufficiently strong radial force at
the graft's end openings to hold the graft material open against
the artery wall. Also, the stent is intended to be short in length
so that the graft will include flexibility sufficient to
accommodate a patient's anatomy. This combination of flexibility
and strong radial force provides an improved seal between the graft
and artery wall. In addition, enhanced flexibility is provided as
well, particularly when one or more stents are used to provide
short segments and better accommodate curves.
[0034] FIG. 1 shows a conventional stent 100, which has symmetrical
apices 102, 103. Specifically, the proximal apices 102 and the
distal apices 103 all have generally the same radii of curvature
(r.sup.1), which is illustrated in graphic form in FIG. 2. FIG. 3
is adapted from an FEA contour simulation and shows the stent 100
in a simulated artery 110, where the stent 100 is 20% oversized.
The proximal and distal apices 102, 103 (circled) exert little or
no pressure against the artery wall 110, while an intermediate
region 107 exerts a higher pressure to provide--in one example--a
total radial sealing force of 0.178 lbf. This configuration may be
crimped to 18 Fr (e.g., for introduction via a catheter), with a
maximum bend strain in the apices 102, 103 of about 5.8%. When
using, for example, a typical NiTi wire for the stent, it is
desirable not to exceed 10-12% strain to avoid increased risk of
deforming the wire or adversely affecting its durability.
[0035] FIGS. 4-7 show a first example of a non-symmetrical stent
200, which is formed as a wire ring that has non-symmetrical
proximal and distal generally curved apex portions (apices) 202,
203 separated from each other by intermediate generally straight
portions. Specifically, the distal apices 203 all have generally
the same radii of curvature (r.sup.d) as each other, but the distal
apices' radii of curvature are different from those of the proximal
apices 202 (r.sup.p). The distal apices 203 (which may be attached
to and generally covered by graft material in a stent graft as
described below with reference to FIGS. 14-15) are generally
narrowly rounded in a manner not dissimilar from a traditional
z-stent, but the proximal apices 202 are more broadly rounded. The
difference in the proximal and distal apices 202, 203 is
illustrated in graphic form in FIG. 5. In the illustrated example,
the rounded proximal apices 202 have a radius of curvature of 6.0
mm, while the narrower distal apices 202 have a radius of curvature
of 1.0 mm. In certain examples of non-symmetrical stents of the
present invention, the radius of curvature of the rounded proximal
apices (measured in the manner shown in FIG. 5) may be from about 4
mm to about 9 mm, and the radius of curvature of the narrower
distal apices may be from about 0.5 mm to about 1.5 mm.
[0036] In these and other examples, the ratio of the proximal
apices' radius of curvature to the distal apices' radius of
curvature may be about 2.6:1 to about 18:1, and desirably may be
about 6:1. The outer circumference of the stent 200 preferably is
generally consistent such that, in this configuration, a solid
outer face around the stent 200 would form a cylinder, although the
stent will most preferably provide compliance with a surface less
smooth than a cylinder.
[0037] FIG. 6 is adapted from an FEA contour simulation and shows
the stent 200 in a simulated artery 210, where the stent 200 is 20%
oversized. The proximal and distal apices 202, 203 (circled) exert
little or no pressure against the artery wall 210, while an
intermediate region 204 (boxed) exerts a greater pressure to
provide --in the illustrated example--a total radial sealing force
of about 0.160 lbf. This configuration may be crimped to 18 Fr,
with a maximum bend strain in the apices 202, 203 of about
6.5%.
[0038] FIG. 7 shows another non-symmetrical stent embodiment 250
that is very similar to the embodiment of FIGS. 4-6, but which has
a shorter proximal-distal length. Each of the examples shown in
FIGS. 4-7 may be manufactured in substantially the same manner as
current z-stents, with a modification only of forming the proximal
apices to include a greater radius of curvature than the distal
apices.
[0039] FIGS. 8-9 illustrate another example of a non-symmetrical
stent 300, which has a proximal "rounded roof shape" profile rather
than the generally semicircular profile of the examples described
above with reference to FIGS. 4-7. The profile of each proximal
apex 302 includes a central fillet 302a and a pair of symmetrically
opposed shoulder fillets 302b that may be generally equidistant
from the central fillet 302a, or that may be disposed at varied
distances therefrom. For the proximal apices of the stent 300, the
central fillets 302a each have a radius of curvature of 1.0 mm, and
the shoulder fillets 302b each have a fillet radius of curvature of
0.5 mm. The distal apices 304 have a radius of curvature of 1.0 mm.
In another example having the rounded roof shape configuration (not
shown), the central and shoulder fillets of proximal apices may
each have the same radius of curvature such as, for example, 0.5 mm
each, with distal apices also having a 0.5 mm radius of curvature.
In other examples, the central and shoulder fillets 302a, 302b may
each have a radius of curvature from about 0.5 mm to about 5 mm,
and the distal apices may each have a radius of curvature of about
0.5 mm to about 1.5 mm. In another example having the rounded roof
shape configuration (not shown), the ratio between the radii of
curvature of the central and each shoulder fillet of the proximal
apices may be about 3:1. FIG. 8 also shows three spans useful for
describing desirable proportions in stent embodiments: "x"
indicates the distance between the apical extremities of the
shoulder fillets 302b, "y" indicates the distance between the tips
of the distal apices 304, and "z" indicates the distance along a
longitudinal axis between the tip of the distal apices 304 and the
apical extremity of the proximal fillet 302a. Desirable embodiments
may include an x:y ratio of about 1:3 to about 7:8 and a y:z ratio
of about 1:1 to about 3:1. In yet another example (not shown), the
filleted apices of this example may be combined with the generally
semicircular apices of the example described with reference to
FIGS. 4-7.
[0040] FIG. 9 is adapted from an FEA contour simulation and shows
the stent 300 in a simulated artery 310, where the stent 300 is 20%
oversized. The proximal and distal apices 302, 304 exert little or
no pressure against the artery wall 310, while an intermediate
region exerts a greater pressure to provide --in the illustrated
example--a total radial sealing force of about 0.420 lbf. This
configuration may be crimped to 18 Fr, with maximum bend strains in
the apices that may be less than about 9% and preferably are less
than about 10-12%. The greater radial sealing force of this example
may provide advantages for stent placement and retention in certain
circumstances as compared to existing z-stents.
[0041] FIGS. 10-13 illustrate another example of a non-symmetrical
stent 400, which has an expanded "flower configuration" as shown in
FIG. 10. Specifically, when the stent 400 is in an expanded
configuration, the circumference around the proximal more-rounded
apices 402 is greater than the circumference around the distal
less-rounded apices 404, which is shown most clearly in FIGS.
11-14. In this configuration a solid outer face around an expanded
stent 400 would form a frustum of a cone. This configuration may be
manufactured in the same manner as the examples described above
with reference to FIGS. 4-7 (i.e., producing a stent with a
generally uniform outer circumference), with an added step that may
include drawing the distal apices 404 into a smaller circumference
upon suturing them to a smaller diameter graft material.
Alternatively, or in addition, the stent 400 may be heat-set to
impose the desired shape.
[0042] FIG. 13 is adapted from an FEA contour simulation and shows
the stent 400 in a simulated artery 410, where the stent 400 is 20%
oversized. Surprisingly, the contour of pressure distribution along
proximal and distal apices 402, 404 as well as an intermediate
region is generally uniform throughout the stent circumference. The
illustrated configuration provides a total radial sealing force of
about 0.187 lbf. This property of generally uniform pressure
distribution may provide advantages in certain applications of
providing a seal and/or presenting less abrasion of a vessel wall
through graft material as compared to stents with less uniform
pressure distribution.
[0043] FIGS. 14-15 show two different views of a stent graft 500
using a stent example 400 of the present invention described above
with reference to FIGS. 10-13. The stent graft 500 is shown in an
expanded state and may be configured for use in treating a thoracic
aortic aneurysm. The stent 400 is disposed at the proximal end of a
generally cylindrical graft sleeve 502, to which its distal apices
404 are secured by sutures 504. The stent graft 500 also includes a
series of z-stents 510a-d disposed distally from the stent 400. The
first z-stent 510a is attached to the inner circumference of the
graft 502, and the other z-stents 510b-510d are attached to the
outer diameter of the graft 502. The proximal end of the stent 400
extends beyond the proximal end of the graft in a manner that may
facilitate anchoring the graft in a vessel of a patient (e.g., a
blood vessel).
[0044] The rounded points on the stent may protrude from the graft
material only a small amount as is shown in FIGS. 14-15. In this
example, only a small portion of the bare wire will be exposed to
the artery wall. These unique (larger radii) rounded points are far
less likely to perforate the artery wall than sharper points of a
different stent configuration. Advantageously, this asymmetric
stent design will maximize the efficacy of the seal while
preserving the condition of the artery wall. Specifically, the
narrower stent apices will provide for desirable radial
expansion/sealing force, and the broader rounded apices will
provide for a desirably atraumatic contact with an artery wall.
[0045] FIGS. 16-18 show a stent-graft embodiment 600 that includes
a non-symmetrical stent 602 having more broadly rounded proximal
apices 604 and more narrowly rounded distal apices 606. The stent
602 is attached by sutures to the inner surface (not shown) or
outer surface of a generally columnar graft 610, which includes
other stents 608. A second layer of graft material 612 is also
attached to the inner circumference of the graft 610 midway down
its length and extends proximally through the inner circumference
of the stent 602.
[0046] As shown in the end view of FIG. 17, this construction
provides a passage for branch structures 614 (that may be embodied,
for example, as tubular or non-tubular stents, stent-grafts, shown
here for the sake of illustration as generic tubular structures),
which pass through the passage formed between the two layers 610,
612 and through an aperture 611 in the graft 610. The tubular
structures 614 will advantageously be disposed generally
transversely through the inner radius of the more broadly rounded
proximal apices 604 of the stent 602, which provides atraumatic
columnar support for the graft 610 as well as an anchor for the
tubular structures 614. The stent-graft 600 may be particularly
useful for treatment of an abdominal aortic aneurysm (AAA) that is
immediately adjacent to, or that goes across, the renal arteries
such that it has a short neck and lacks a contact area that is
sufficient to create an effective proximal seal and avoid the
proximal Type I endoleaks that may occur with some
currently-available AAA stent-grafts. Those of skill in the art
will appreciate that the stent-graft 600 will allow general
occlusion of the AAA, while providing patent passage through the
descending aorta and from the aorta to the renal arteries.
Specifically, a stent-graft configured in the manner of the
stent-graft embodiment 600, which includes a modular design that
may include branch stents and/or stent-grafts, will allow a seal to
be formed above the renal arteries and below the celiac and
superior mesenteric arteries. Also, as shown in FIG. 16, a second
non-symmetrical stent 622 may be placed adjacent the first
non-symmetrical stent 602 in an opposite orientation that will
provide additional atraumatic support for the branching tubular
structures 614.
[0047] FIG. 19 shows a stent-graft device 700 configured for
endovascular treatment of a thoracic aorta dissection. The device
700 includes a non-symmetrical alignment stent 702 attached to a
first end of a tubular graft material 704. A sealing stent 706 is
attached in the central lumenal graft space proximate the alignment
stent 702. The sealing stent 706 preferably is configured with a
high radial force to promote efficacious sealing of the graft
material 704 against a vessel wall. A body stent 708 configured
here as a z-stent is disposed on the exterior of the graft material
704 and preferably is configured to provide longitudinal and
circumferential stability/columnar support for the graft material
of the device 700, such that it will conform to the vasculature and
resist buckling when deployed in torturous anatomy such as the
ascending thoracic aorta. A bare cannula stent 710 (such as, for
example, a cut nitinol stent) is attached in the tubular graft
material 704 at the opposite end from the alignment stent 702. This
cannula stent 710 preferably is a conformable kink-resistant stent
that provides distal sealing and migration-resistance. In a
deployment of the device 700 to treat an aortic dissection, the
alignment stent 702 preferably will be disposed proximal (nearer
the heart) relative to the vessel tear, with the graft material
traversing the tear in a manner generally sealing it from blood
flow. And, the distal cannula stent 710 will help conform to the
vasculature and retain a seal for treatment of the dissection. One
or more of the sealing stent 706, body stent 708, and bare stent
710 may include one or more barbed projections configured to help
anchor the device 700.
[0048] FIG. 20 shows a stent-graft device 800 configured for
endovascular treatment of a thoracic aortic aneurysm. The device
800 includes a proximal component 802 and a distal component 822.
The proximal component 802 has a tubular graft material 805 having
proximal and distal ends 803a and 803b, and further may comprise a
proximal stent 804 attached to the proximal end 803a of the graft
material 805. The proximal stent 804 preferably is a
non-symmetrical alignment stent provided in accordance with the
stent 400 described above, such that the rounded points on the
stent may protrude from the graft material and are less likely to
perforate the artery wall than sharper points of a different stent
configuration. In a deployment of the device 800 to treat a
thoracic aortic aneurysm, the alignment stent 804 preferably will
be disposed proximal (nearer the heart) relative to the aneurysm,
with the graft material 805 traversing the aneurysm in a manner
generally sealing it from blood flow.
[0049] The proximal component 802 further comprises a series of
z-stents 810a-810f disposed distally from the proximal stem 804. A
proximal z-stent 810a may be attached to the inner circumference of
the graft material 805, other z-stents 810b-810e may be attached to
the outer diameter of the graft material 805, and a distal z-stent
810f may be attached to the inner circumference of the graft
material 805, as depicted in FIG. 20. However, it should be noted
that some stents depicted on the inner circumference of the graft
material 805 alternatively may be attached to the outer diameter of
the graft material 805, and vice versa.
[0050] Moreover, in one embodiment, the proximal stent 804
extending from the graft material 805 may at least partially
overlap with the most proximal z-stent 810a, as depicted in FIG.
20, The overlap may be range from about 1.0 mm to about 3.0 mm, and
more preferably about 2.0 mm.
[0051] The distal component 822 has a graft material 825 having
proximal and distal ends 823a and 823b, and a series of z-stents
830a-830g. In the example shown, the proximal three z-stents
830a-830c are attached to the inner circumference of the graft
material 805, three other z-stents 830d-830f are attached to the
outer diameter of the graft material 805, and a distal z-stent 830g
is attached to the inner circumference of the graft material 805.
However, like the proximal component 802, the z-stents of the
distal component 822 may be attached to either the inner
circumference or the outer diameter of the graft material 805.
[0052] The proximal end 823a of the graft material 825 may comprise
one or more scallops 845. Preferably, a plurality of scallops 845
are provided that closely follow the shape of the proximal z-stent
830a, such that portions of the graft material 825 are cut out just
proximal to the z-stent 830a, as shown in FIG. 20. In this manner,
the plurality of scallops 845 may advantageously reduce the
potential for graft infolding, thereby reducing or eliminating the
likelihood of impeded blood flow and/or endoleaks around the distal
component 822.
[0053] At the distal end 823b of the distal component 822, there is
also a distally extending z-stent stent 834, which has a proximal
end that may be fastened to the graft 825 using sutures, and then
is exposed distal to the graft material, as shown in FIG. 20. The
distally extending stent 834 has barbs 836 on some of its struts
and the barbs 836 are directed proximally. The barbs 836 may be
formed integrally with the stent 834, or formed externally and
attached thereto, and reduce or prevent proximal migration of the
distal end 823b of the distal component 822. Further, one or more
radiopaque markers may be provided to facilitate correct
positioning of the distal end of the distal component 822.
[0054] The proximal and distal components 802 and 822 may be
introduced and deployed using separate deployment systems. In one
embodiment, the proximal component 802 is introduced using a
delivery system having a curved tip, while the distal component 822
is introduced using a delivery system having a straight tip.
[0055] When the stent graft device 800 of FIG. 20 is deployed to
treat a thoracic aortic aneurysm, proximal and distal components
802 and 822 at least partially overlap with one another to provide
a fluid passageway therebetween. The proximal end 823a of the
distal component 822 may be deployed either inside the distal end
803b of the proximal component 802, although in other embodiments
the proximal component 802 may be deployed inside of the distal
component 822. This means that in deploying the stent graft
assembly 800, either the proximal or distal components 802 and 822
may be deployed first and the other portion subsequently deployed
depending upon the requirements in a particular case. In either
case, it is preferable to have at least two stents overlap to
facilitate sealing between the first and second portions. Also, by
having an overlap of at least two stents, relative movement between
the first and second portions is less likely to cause parting of
the first and second portions when it is deployed and pulsating
blood flow through the stent graft causes sideways movement.
[0056] Advantageously, when the stent graft device 800 of FIG. 20
is deployed, the proximal stent 804, which preferably is a
non-symmetrical alignment stent, will maximize the efficacy of the
proximal seal while reducing atraumatic contact with an artery
wall, as noted above, and preventing distal migration of the
proximal end of the stent graft. Further, as noted above, the
plurality of scallops 845 may advantageously reduce the potential
for graft infolding, thereby reducing or eliminating the likelihood
of impeded blood flow and/or endoleaks around the distal component
822.
[0057] Stent examples of the present invention may be constructed
of NiTi alloys or other materials presently known or yet to be
developed, all within the scope of the present invention. The
stents preferably are made from Nitinol wire and will therefore be
MRI compatible. In another preferable embodiment, a stent may be
made from a laser-cut Nitinol cannula, effectively rendering it a
seamless or nearly-seamless wire-like construction. Nitinol's
superelastic properties will facilitate the stents ability to be
crimped down into a low profile delivery system.
[0058] While various embodiments of the invention have been
described, the invention is not to be restricted except in light of
the attached claims and their equivalents. Moreover, the advantages
described herein are not necessarily the only advantages of the
invention and it is not necessarily expected that every embodiment
of the invention will achieve all of the advantages described.
* * * * *