U.S. patent application number 15/349758 was filed with the patent office on 2017-03-02 for apparatus and methods for endoluminal graft placement.
The applicant listed for this patent is Timothy J. RYAN. Invention is credited to Timothy J. RYAN.
Application Number | 20170056156 15/349758 |
Document ID | / |
Family ID | 22969434 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170056156 |
Kind Code |
A1 |
RYAN; Timothy J. |
March 2, 2017 |
APPARATUS AND METHODS FOR ENDOLUMINAL GRAFT PLACEMENT
Abstract
A vascular graft comprises a perforate tubular compressible
frame having a fabric liner disposed over at least a portion of the
frames lumen. The graft may be used in combination with a base
structure to form a bifurcated graft in situ. The base structure
compresses a compressible frame having a fabric liner which defines
a pair of divergent legs. The base structure is positioned within
the aorta so that one leg enters each iliac. The tubular grafts can
then be introduced into each leg to form the bifurcated structure.
A graft delivery catheter includes a controllably flared sheath
which facilitates recapture of a partially deployed graft.
Inventors: |
RYAN; Timothy J.; (San
Pedro, CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
RYAN; Timothy J. |
San Pedro |
CA |
US |
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Family ID: |
22969434 |
Appl. No.: |
15/349758 |
Filed: |
November 11, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13928280 |
Jun 26, 2013 |
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15349758 |
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13281973 |
Oct 26, 2011 |
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13928280 |
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08463836 |
Jun 5, 1995 |
8206427 |
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13281973 |
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08255681 |
Jun 8, 1994 |
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08463836 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/91558
20130101; A61F 2002/9511 20130101; A61F 2/954 20130101; A61F
2250/0048 20130101; A61F 2002/9534 20130101; A61F 2250/0039
20130101; A61F 2/89 20130101; A61F 2/9522 20200501; A61F 2002/072
20130101; A61F 2002/91541 20130101; A61F 2/07 20130101; A61F
2240/001 20130101; A61F 2250/0019 20130101; A61F 2250/0098
20130101; A61F 2002/067 20130101; A61F 2220/0075 20130101; A61F
2/848 20130101; A61F 2/90 20130101; A61F 2220/0058 20130101; A61F
2250/0029 20130101; A61F 2250/0018 20130101; A61F 2002/075
20130101; A61F 2210/0019 20130101; A61F 2230/0054 20130101; A61F
2/91 20130101; A61F 2/915 20130101 |
International
Class: |
A61F 2/07 20060101
A61F002/07; A61F 2/954 20060101 A61F002/954; A61F 2/915 20060101
A61F002/915 |
Claims
1. A method for introducing a vascular graft into a primary artery
which divides into first and second branch arteries, said method
comprising: introducing and deploying a bifurcated structure
including an anchor section and first and second connector sections
so that the anchor section is disposed within the primary artery
and the first and second connector sections extend toward the first
and second branch arteries and thereafter; introducing a first
tubular graft into the first connector section and anchoring said
first tubular graft to extend between the first connector section
and the first branch artery to form a first continuous flow path
from the primary artery to the first branch artery; and introducing
a second tubular graft into the second connector section and
anchoring said second tubular graft to extend between the second
connector section and the second branch artery to form a second
continuous flow path from the primary artery to the second branch
artery.
2. A method as in claim 1, wherein the primary artery is an aorta,
the first branch artery is a right iliac, and the second branch
artery is a left iliac.
3. A method as in claim 1, wherein the anchor section of the
bifurcated structure is radially compressed while being
introduced.
4. A method as in claim 3, wherein the anchor section is composed
of a resilient material, said method further comprising releasing
the radially compressed anchor section at a target location with
the primary artery.
5. A method as in claim 1, wherein the bifurcated structure is
introduced through the primary artery in an antegrade
direction.
6. A method as in claim 1, wherein the bifurcated structure is
introduced through a branch artery in a retrograde direction.
7. A method as in claim 1, wherein the first tubular graft is
radially compressed while being introduced.
8. A method as in claim 7, wherein the first tubular graft is
composed of a resilient material, said method further comprising
releasing the radially compressed graft to anchor simultaneously
within the first connector and the first branch artery.
9. A method as in claim 1, wherein the first tubular graft is
introduced through the primary artery in an antegrade
direction.
10. A method as in claim 1, wherein the first tubular graft is
introduced through a branch artery in a retrograde direction.
11. A method as in claim 1, wherein the second tubular graft is
radially compressed while being introduced.
12. A method as in claim 11, wherein the second tubular graft is
composed of a resilient material, said method further comprising
releasing the radially compressed graft to anchor simultaneously
within the second connector and the second branch artery.
13. A method as in claim 1, wherein the second tubular graft is
introduced through the primary artery in an antegrade
direction.
14. A method as in claim 1, wherein the second tubular graft is
introduced through a branch artery in a retrograde direction.
15. A method for treating an aneurysm by introducing a vascular
graft into a primary artery which branches into first and second
branch arteries, said method comprising: introducing into a
patient's vasculature an anchor section and first tubular graft of
the vascular graft so that the anchor section is disposed within
the primary artery and the first tubular graft is at least
partially disposed within the first branch artery to form a first
continuous flow path from the primary artery to the first branch
artery; and securing a second tubular graft to the anchor section
via a connector leg of the anchor section to form a second
continuous flow path from the primary artery to the second branch
artery, wherein each of the grafts comprises a tubular frame and a
liner.
16. A method as in claim 15, wherein the primary artery is an
aorta, the first branch artery is a right iliac, and the second
branch artery is a left iliac.
17. A method as in claim 15, wherein the anchor section and first
tubular graft of the vascular graft are radially compressed while
being introduced.
18. A method as in claim 17, wherein the anchor section and first
tubular graft of the vascular graft are resilient, said introducing
step comprising releasing the radially compressed anchor section
and first tubular graft at a target location with the
vasculature.
19. A method as in claim 18, wherein the anchor section and first
tubular graft of the vascular graft are introduced through the
primary artery in an antegrade direction.
20. A method as in claim 18, wherein the anchor section and first
tubular graft of the vascular graft are introduced through a branch
artery in a retrograde direction.
21. A method as in claim 18, wherein the second tubular graft is
radially compressed while being introduced.
22. A method as in claim 21, wherein the second tubular graft is
resilient, said method further comprising releasing the radially
compressed second tubular graft to anchor within the connector leg
on the anchor section.
23. A method as in claim 22, wherein the second tubular graft is
introduced through the primary artery in an antegrade
direction.
24. A method as in claim 22, wherein the second tubular graft is
introduced through a branch artery in a retrograde direction.
25. A method as in claim 15, wherein the introducing step comprises
securing the first tubular graft to the anchor section of the
vascular graft after the anchor section has been disposed within
the primary artery.
26. A method as in claim 25, wherein the first tubular graft is
secured to the anchor section via a second connector leg of the
anchor section.
27. A method as in claim 26, wherein the first tubular graft is
resilient and wherein the securing of the first tubular graft to
the anchor section comprises releasing the first tubular graft from
a compressed configuration to expand within the second connector
leg and the first branch artery.
28. A method as in claim 27, wherein the second tubular graft is
resilient and wherein the securing of the second tubular graft to
the anchor section comprises releasing the second tubular graft
from a compressed configuration to expand within its respective
connector leg and the second branch artery.
29. A method as in claim 25, wherein the primary artery is an
aorta, the first branch artery is a right iliac, and the second
branch artery is a left iliac.
30. A method as in claim 29, wherein the second tubular graft is
resilient and wherein the securing of the second tubular graft to
the anchor section comprises releasing the second tubular graft
from a compressed configuration to expand within the connector leg
and the left iliac.
31. A method as in claim 25, wherein the anchor section of the
vascular graft is radially compressed while being introduced.
32. A method as in claim 31, wherein the anchor section is
resilient, said introducing step comprising releasing the radially
compressed anchor section at a target location with the
vasculature.
33. A method as in claim 32, wherein the anchor section of the
vascular graft is introduced through the primary artery in an
antegrade direction.
34. A method as in claim 32, wherein the anchor section of the
vascular graft is introduced through a branch artery in a
retrograde direction.
35. A method as in claim 25, wherein the first tubular graft is
radially compressed while being introduced.
36. A method as in claim 35, wherein the first tubular graft is
resilient, said introducing step comprising releasing the radially
compressed first tubular graft to anchor within a second connector
leg on the anchor section.
37. A method as in claim 36, wherein the first tubular graft is
introduced through the primary artery in an antegrade
direction.
38. A method as in claim 36, wherein the first tubular graft is
introduced through a branch artery in a retrograde direction.
39. A method as in claim 36, wherein the second tubular graft is
radially compressed while being introduced.
40. A method as in claim 39, wherein the second tubular graft is
resilient, said method further comprising releasing the radially
compressed second tubular graft to anchor simultaneously within the
connector leg on the anchor section and the second branch
artery.
41. A method as in claim 40, wherein the second tubular graft is
introduced through the primary artery in an antegrade
direction.
42. A method as in claim 40, wherein the second tubular graft is
introduced through a branch artery in a retrograde direction.
Description
RELATED APPLICATION DATA
[0001] This application is a divisional of co-pending application
Ser. No. 13/281,973, filed Oct. 26, 2011, which is a divisional of
Ser. No. 08/463,836, filed Jun. 5, 1995, now U.S. Pat. No.
8,206,427, which is a divisional of application Ser. No.
08/255,681, filed Jun. 8, 1994, the entire disclosures of which are
expressly incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to apparatus and
methods for endoluminal placement of grafts, stents, and other
structures. More particularly, the present invention relates to a
low profile, compressible graft structure and apparatus and methods
for vascular placement of such structures for the treatment of
abdominal and other aneurysms.
[0004] Vascular aneurysms are the result of abnormal dilation of a
blood vessel, usually resulting from disease and/or genetic
predisposition which can weaken the arterial wall and allow it to
expand. While aneurysms can occur in any blood vessel, most occur
in the aorta and peripheral arteries, with the majority of aortic
aneurysms occurring in the abdominal aorta, usually beginning below
the renal arteries and often extending distally into one or both of
the iliac arteries.
[0005] Aortic aneurysms are most commonly treated in open surgical
procedures where the diseased vessel segment is bypassed and
repaired with an artificial vascular graft. While considered to be
an effective surgical technique, particularly considering the
alternative of a usually fatal ruptured abdominal aortic aneurysm,
conventional vascular graft surgery suffers from a number of
disadvantages. The surgical procedure is complex and require
experienced surgeons and well equipped surgical facilities. Even
with the best surgeons and equipment, however, patients being
treated frequently are elderly and weakened from cardiovascular and
other diseases, reducing the number of eligible patients. Even for
eligible patients prior to rupture, conventional aneurysm repair
has a relatively high mortality rate, usually from 3% to 10%.
Morbidity related to the conventional surgery includes myocardial
infarction, renal failure, impotence, paralysis, and other
conditions. Additionally, even with successful surgery, recovery
takes several weeks, and often requires a lengthy hospital
stay.
[0006] In order to overcome some or all of these drawbacks,
endovascular graft placement for the treatment of aneurysms has
been proposed. Although very promising, many of the proposed
methods and apparatus suffer from other problems. Often times the
proposed graft structures will have exposed anchors or frame which
can be thrombogenic. It is also difficult to provide graft
structures which remain sealed to the blood vessel lumen to prevent
the leakage or bypass of blood into the weakened aneurysm,
especially when subjected to external deforming forces which result
from vessel expansion and contraction as the heart beats. Many
vascular graft structures have difficulty in conforming to the
internal arterial wall, particularly since the wall can have a
highly non-uniform surface as a result of atherosclerosis and
calcification and is expanding and contracting with the patient's
heartbeat and blood flow. Additionally, many previous vascular
graft structures are difficult to position and anchor within the
target region of the vessel.
[0007] For these reasons, it would be desirable to provide improved
apparatus and methods for the endovascular placement of
intraluminal grafts for treating aneurysms and other conditions. It
would be particularly desirable if the graft structures were easy
to place in the target region, displayed little or no
thrombogenicity, provided a firm seal to the vascular wall to
prevent leakage and blood bypass, and were able to conform to
uniform and non-uniform blood vessel walls, even while the wall is
expanding and contracting with the patient's heartbeat.
[0008] 2. Description in the Background Art
[0009] Vascular grafts and devices for their transluminal placement
are described in U.S. Pat. Nos. 5,219,355; 5,211,658, 5,104,399;
5,078,726; 4,820,298; 4,787,899; 4,617,932; 4,562,596; 4,577,631;
and 4,140,126; and European Patent Publications 508 473; 466 518;
and 461 791. Expandable and self-expanding vascular stents are
described in U.S. Pat. Nos. 5,147,370; 4,994,071; and 4,776,337;
European patent Publications 575 719; 556 850; 540 290; 536 610;
and 481 365; and German patent Publication DE 42 19 949. A flexible
vascular stent structure having counter wound helical elements,
some of which are separated at particular locations to enhance
flexibility, is commercially available from Angiomed, Karlsruhe,
Germany, as described in a brochure entitled Memotherm Iliaca
Stents.
[0010] Catheters for placing vascular stents are described in U.S.
Pat. Nos. 5,192,297; 5,092,877; 5,089,005; 5,037,427; 4,969,890;
and 4,886,062.
[0011] Vascular grafts intended for open surgical implantation are
described in U.S. Pat. Nos. 5,236,447; 5,084,065; 4,842,575;
3,945,052; and 3,657,744; and PCT applications WO 88/00313 and WO
80/02641; and SU 1697787.
[0012] Nickel titanium alloys and their use in medical devices are
described in U.S. Pat. Nos. 4,665,906 and 4,505,767.
SUMMARY OF THE INVENTION
[0013] The present invention comprises apparatus and methods for
the endoluminal placement of intraluminal grafts for the treatment
of disease conditions, particularly aneurysms. The intraluminal
grafts comprise a radially compressible, perforate tubular frame
having a proximal end, a distal end, and an axial lumen between
said ends. An interior liner, typically a fabric, polymeric sheet,
membrane, or the like, covers all or most of the surface of the
lumen of the tubular frame, extending from a near-proximal
location-to a near-distal location. The liner is attached to the
frame at at least one end, as well as at a plurality of locations
between said ends. Optionally, a second liner may be provided over
at least a portion of the exterior of the frame to cover both sides
of the frame. Such exterior coverage provides a circumferential
seal against the inner wall of the blood vessel lumen in order to
inhibit leakage of blood flow between the graft and the luminal
wall into the aneurysm or stenosis which is being treated.
[0014] The grafts of the present invention will find particular use
in the treatment of vascular conditions, such as abdominal and
other aneurysms, vascular stenoses, and other conditions which
require creation of an artificial vessel lumen. For the treatment
of vascular stenoses, the graft may serve as a stent to maintain
vessel patency in a manner similar to that described in the
above-described U.S. and, foreign patent documents relating to
stents. Other intraluminal uses of the devices and methods of the
present invention include stenting of the ureter, urethra, biliary
tract, and the like. The devices and methods may also be used for
the creation of temporary or long term lumens, such as the
formation of a fistula.
[0015] Such graft structures provide a number of advantages over
previously proposed designs, particularly for vascular uses. By
covering the lumen of the tubular frame, thrombogenicity of the
graft resulting from exposed frame elements is greatly reduced or
eliminated. Such reduction of thrombogenicity is achieved while
maintaining the benefits of having a frame structure extending over
the graft. Such an external frame helps anchor the graft in place
and maintain patency and evenness of the graft lumen, both of which
are advantages over graft structures which are anchored and
supported only at each end. The vascular grafts of the present
invention are also self-expanding and easy to place. The
self-expanding nature of the frame also counteracts external
deforming forces that may result from the continuous physiologic
expansion and contraction of the blood vessel lumen. Moreover, the
lack of cleats, tines, or other penetrating elements on the graft
allows the graft to more closely conform to the surrounding vessel
wall and facilitates retrieval and/or repositioning of the graft,
as will be described in more detail hereinafter. Additionally, the
resilient tubular frame structure permits the graft to conform to
even irregular regions of the blood vessel wall as the wall is
expanding and contracting as a result of the pumping of the
patient's heart.
[0016] The tubular frame preferably comprises a plurality of
radially compressible band or ring structures, each of which have a
relaxed (i.e., non-compressed) diameter which is greater than the
diameter of the blood vessel to be treated. Adjacent compressible
band members may be independent of each other or may be joined at
one or more locations therebetween. If joined, the bands are
preferably joined at only two diametrically opposed points to
enhance flexibility of the frame over its length. Independent band
members will be held together by their attachment to the interior
and/or exterior, liner(s).
[0017] Alternatively, the tubular frame may comprise a plurality of
laterally compressible axial members, with adjacent axial members
preferably not being directly connected to each other. The axial
members will usually comprise a multiplicity of repeating
structural units, e.g., diamond-shaped elements, which are axially
connected. The axial members will be attached to the inner liner,
either by stitching or by capturing the axial members in pockets
formed between the inner liner and an outer liner disposed over the
frame. The pockets may be formed by attaching the inner and outer
liners to each other along axial lines between adjacent axial
members.
[0018] The present invention also provides methods and systems for
the in situ placement of bifurcated grafts for the treatment of
aorto-iliac segments and other bifurcated lumens. The system
comprises a bifurcated base structure including a proximal anchor,
typically a self-expanding frame, which defines a common flow lumen
and a pair of connector legs that establish divergent flow lumens
from the common flow lumen. The system also includes a first
tubular graft which can be anchored within first of the connector
legs to form a continuous extension of the first divergent flow
lumen and a second tubular graft which can be anchored within a
second of the connector legs to form a continuous extension of the
second divergent flow lumen. The method of placement comprises
first introducing the bifurcated base structure so that the anchor
section is positioned within a primary vessel, i.e., the aorta,
below the renal arteries. After the bifurcated base structure is
anchored, the first tubular graft is introduced into the first
connector leg and anchored between said leg and the first branch
artery, e.g., the right iliac. The second tubular graft is then
inserted into the second connector section and anchored between the
second connector and the second branch artery. By properly
selecting the dimensions of the bifurcated base structure, the
first tubular graft, and the second tubular graft, the resulting
bifurcated graft structure can have dimensions which are
specifically matched to the vessel dimensions being treated.
Preferably, the bifurcated base structure, first tubular graft, and
second tubular graft, will be formed from radially compressible
perforate tubular frames having interior and/or exterior liners,
generally as described above for the preferred vascular graft of
the present invention. The radially compressible perforate tubular
frame on the base structure, however, will terminate above the
region where the connector legs diverge. The connector legs below
the divergent region will be reinforced by placement and expansion
of the tubular graft structures therein.
[0019] The present invention further provides a delivery catheter
for endovascular placement of radially compressible grafts or
stents, such as the vascular grafts and bifurcated base structures
described above. The catheter comprises an elongate shaft having a
proximal end and a distal end. Preferably, a retaining structure is
provided near the distal end of the shaft for holding the graft or
the stent on the shaft until such a time that the graft or stent is
positively released, e.g., by withdrawing a pull wire which extends
through locking stays on either side of the graft or stent. The
delivery catheter further comprises a sheath slidably mounted over
the shaft. The sheath is initially disposed to cover and restrain
the radially compressed graft or stent while the catheter is being
intervascularly introduced to a desired target location. The sheath
may then be withdrawn, releasing the radially compressed graft or
stent to occupy and anchor within the vasculature or other body
lumen. Preferably, the graft or stent will remain fixed to the
shaft even while the sheath is being withdrawn so that the
physician can recapture the graft by advancing the sheath back over
its exterior. Only after the graft or stent is fully expanded at
the target location within the vessel lumen is the graft or stent
finally released. Preferably, the sheath will have a flared or
outwardly tapered distal end to facilitate both release and
recapture of the graft or stent by axial translation of the sheath.
The flared end may be fixed or deployable, i.e., selectively
shiftable between a flared and a non-flared configuration.
Preferably, the flared end will be deployable so that the sheath
may be introduced with the distal end in its non-flared
configuration to minimize its profile. After properly positioning
the sheath, the distal end may be opened to assume its tapered
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a side view of a vascular graft constructed in
accordance with the principles of the present invention.
[0021] FIG. 1A is a side view of a first alternate embodiment of a
vascular graft constructed in accordance with the principles of the
present invention.
[0022] FIG. 1B is a side view of a second alternate embodiment of a
vascular graft constructed in accordance with the principles of the
present invention.
[0023] FIG. 2 is a side view of a radially compressible perforate
tubular frame of a type which may be used in a vascular graft of
FIG. 1.
[0024] FIGS. 3A and 3B are a schematic illustrations showing the
joining pattern of the radially compressible band members of the
tubular frame of FIG. 2.
[0025] FIG. 4 illustrates a structure which has been etched from a
tube and which may be subsequently expanded to form the tubular
frame of FIG. 2.
[0026] FIG. 5 illustrates a bifurcated base structure which is part
of a system for forming a bifurcated graft in situ.
[0027] FIG. 6 illustrates the distal end of a graft and stent
placement catheter constructed in accordance with the principles of
the present invention.
[0028] FIG. 7-12 illustrate placement of a bifurcated aortic graft
using the bifurcated graft placement system of the present
invention.
DESCRIPTION OF THE SPECIFIC EMBODIMENT
[0029] The present invention provides apparatus and methods for the
transluminal placement of graft structures, particularly within the
vascular system for treatment of aneurysms and other vascular
conditions, but also in other body lumens, such as ureter, urethra,
biliary tract, gastrointestinal tract, and the like, for the
treatment of other conditions which benefit from the introduction
of a reinforcing or protective structure in the lumen. The
apparatus and methods can also find use in the creation of
artificial lumens through solid tissue and structures, such as the
placement of a TE fistula via an endoscope. The vascular grafts
will be placed endovascularly. As used herein, "endovascularly"
will mean placement by percutaneous or cutdown transluminal
procedures using a catheter over a guidewire under fluoroscopic
guidance. The catheters and guidewires may be introduced through
conventional access sites to the vascular system, such as through
the brachial and subclavian arteries for access to the aorta and
through the femoral arteries for access to the aorta or to
peripheral and branch blood vessels.
[0030] A vascular graft according to the present invention will
comprise a radially compressible perforate tubular frame and an
inner or interior liner attached within a central lumen defined by
the frame and optionally a second or outer liner formed over the
exterior of the frame. The radially compressible frame can take a
variety of forms, usually comprising or consisting of a plurality
of independent or interconnected structural elements, such as
rings, bands, helical elements, serpentine elements, axial struts,
parallel bars, and the like, that can be compressed from a relaxed,
large diameter configuration to a small diameter configuration to
facilitate introduction, as discussed below. It is necessary, of
course, that the liner(s) remain attached to the frame both in its
radially compressed configuration and in its expanded, relaxed
configuration.
[0031] A preferred configuration for the tubular frame comprises a
plurality of radially compressible band members, where adjacent
band members are joined to each other at only two diametrically
opposed points in order to enhance flexibility. In a particularly
preferred aspect, the diametrically opposed attachment points are
rotationally staggered in order to provide flexibility in more than
one direction. A preferred method for forming such a tubular frame
is described in more detail hereinafter. In another preferred
configuration, at least some of the bands of the frame are
independent, i.e., are not directly connected to each other.
Instead, the bands are connected only to the liner(s) which
maintain the axial integrity of the graft. Preferably, the
independent bands are stitched or sealed between interior and
exterior liners, as will be described in more detail below. Other
suitable frame structures are described in the patent
literature.
[0032] In an alternate configuration, the perforate tubular frame
comprises a plurality of laterally compressible axial members which
are attached directly, e.g., by stitching, or indirectly, e.g., by
lamination, to the inner liner. The axial members may be a
multiplicity of repeating structural elements, such as diamonds, or
could be formed from two or more overlapping elements. By
positioning the axial members in pockets formed between an inner
liner and an outer liner, the axial elements will be able to flex
independently while providing the desired radial compressibility
and self-expansion characteristics for the graft.
[0033] The dimensions of the tubular graft will depend on the
intended use. Typically, the graft will have a length in the range
from about 50 mm to 500 mm, preferably from about 80 mm to 200 mm
for vascular applications. The relaxed diameter will usually be in
the range from about 4 mm to 45 mm, preferably being in the range
from about 5 mm to 25 mm for vascular applications. The graft will
be radially compressible to a diameter in the range from 3 mm to 9
mm, preferably from 4 mm to 6 mm for vascular applications.
[0034] The liner(s) will be composed of conventional biological
graft materials, such as polyesters, polytetrafluoroethylenes
(PTFE's), polyurethanes, and the like, usually being in the form of
woven fabrics, non-woven fabrics, polymeric sheets, membranes, and
the like. A presently preferred, fabric liner material is a plain
woven polyester, such as type 56 Dacron.RTM. yarn (Dupont,
Wilmington, Del.), having a weight of 40 denier, woven at 27
filaments with 178 warp yarns per circumferential inch, and 78
yarns per inch in the fill direction.
[0035] The liner will be attached to the interior lumen of the
tubular frame and will cover most or all of the interior surface of
the lumen. For example, the liner may be stitched or otherwise
secured to the tubular frame along a plurality of circumferentially
spaced-apart axial lines. Such attachment permits the liner to fold
along a plurality of axial fold lines when the frame is radially
compressed. The liner will further be able to open and conform to
the luminal wall of the tubular frame as the frame expands.
Alternatively, when inner and outer liners are used, the liners may
be stitched, heat welded, or ultrasonically welded together to
sandwich the tubular frame therebetween. In an exemplary embodiment
where a plurality of independent band members are disposed between
interior and exterior liners, the liners are secured together along
circumferential lines between adjacent band members to form pockets
for holding the band members. In a second exemplary embodiment
where a plurality of independent axial members are disposed between
interior and exterior liners, the liners are secured together along
axial lines to form pockets for holding the axial members.
[0036] The liner will preferably be circumferentially sealed
against the tubular frame at at least one end, preferably at both
ends in the case of straight (non-bifurcated) grafts. It is also
preferred in some cases that the distal and proximal end of the
perforate tubular frame be exposed, i.e., not covered by the liner
material, typically over a length in the range from about 1 mm to
25 mm. Frame which is not covered by the liner permits blood
perfusion through the perforations and into branch arteries such as
the renal arteries in the case of abdominal aorta grafts, while
providing additional area for anchoring the frame against the blood
vessel lumen. In an exemplary embodiment, the liner will extend
through the frame and over the exterior surface near either or both
ends to provide a more effective seal against the adjacent blood
vessel wall.
[0037] The radially compressible perforate tubular frame will be
composed of a resilient material, usually metal, often times a heat
and/or shape memory alloy, such as nickel titanium alloys which are
commercially available under the trade name Nitinol.RTM.. The
frames may also be composed of other highly elastic metals, such as
MP-35 N, Elgiloy, 316 L stainless steel, and the like. In the case
of Nitinol.RTM. and other memory alloys, the phase transition
between austenitic and martensitic states may occur between an
introduction temperature, e.g., room temperature (approximately
22.degree. C.), and body temperature (37.degree. C.), to minimize
stress on the unexpanded frame and enhance radial expansion of the
frame from its radially compressed condition. Expansion can also be
achieved based on the highly elastic nature of the alloy, rather
than true shape recovery based on phase change.
[0038] In some cases, it may be desirable to form a tubular frame
having different elastic or other mechanical properties at
different regions along its length. For example, it is possible to
heat treat different regions of the tubular frame so that some
regions possess elastic properties while others become malleable so
that they may be deformed by external force. For example, by
providing at least one malleable end portion and an elastic
(radially compressible) middle portion, the graft can be firmly
expanded and implanted by internal balloon expansion force (to
anchor the end(s) in the inner wall of the blood vessel) while the
middle will remain open due to the elastic nature of the tubular
member. Malleable end portions are a particular advantage since
they can be expanded with a sufficient force, and re-expanded if
necessary, to assure a good seal with the blood vessel wall.
Alternatively, the malleable ends could be formed from a different
material than that of the middle portion of the tubular frame. The
use of different materials would be particularly convenient when
the frame is formed from a plurality of independent bands, where
one or more band members at either or both ends could be formed of
a malleable metal. Usually, such malleable end(s) will extend over
a distance in the range from 5 mm to 50 mm, preferably from 5 mm to
20 mm.
[0039] Malleable portions or segments can also be formed in other
parts of the tubular frame. For example, some circumferentially
spaced-apart segments of the tubular frame could be malleable while
the remaining circumferential segments would be elastic. The frame
would thus remain elastic but have an added malleability to permit
expansion by applying an internal expansion force. Such a
construction would be advantageous since it would allow the
diameter of the graft or stent structure to be expanded if the
initial diameter (which resulted entirely from elastic expansion)
were not large enough for any reason. The proportion of elastic
material to malleable material in the tubular frame can be selected
to provide a desired balance between the extend of initial, elastic
opening and the availability of additional, malleable opening. Such
construction can be achieved by selective heat treatment of
portions of a frame composed of a single alloy material, e.g.
nickel titanium alloy, or by forming circumferential segments of
the frame from different materials having different
elastic/malleable properties. In particular, individual laterally
compressible axial members 204 (as described in connection with
FIG. 1B) could be formed from materials having different
elastic/malleable properties.
[0040] Referring now to FIGS. 1-4, an exemplary graft structure 10
will be described. The graft structure 10 includes a fabric liner
12 and a radially compressible perforate tubular frame 14. For
convenience, the frame 14 is illustrated by itself in FIG. 2. The
frame is illustrated in its expanded (relaxed) configuration in
each of these figures, but may be radially compressed by applying a
radially inward compressive force, usually by placing the graft 10
in an outer sheath, as will be described in more detail
hereinafter.
[0041] The tubular frame 14 comprises a plurality of radially
compressible band members 11, each of which comprises a zig-zag or
z-shaped element which forms a continuous circular ring. Each band
member 11 will typically have a width w in the range from 2 mm to
15 mm, and the tubular frame will comprise from 1 to 30 individual
band members. Adjacent band members 11 are preferably spaced-apart
from each other by a short distance d and are joined by bridge
elements 13. Flexibility is enhanced by providing only two
diametrically opposed bridge elements 13 between each adjacent pair
of band members 11. As will be described further with reference to
FIG. 1A, flexibility can be further enhanced by leaving the band
members connected only by the liner.
[0042] Usually, the perforate tubular frame 14 will be left open at
each end, e.g., at least a portion of the last band member 11 will
remain uncovered by the liner 12. The liner 12 will be stitched or
otherwise secured to the band members 11, preferably at the
junctions or nodes when the element reverses direction to form the
z-pattern (although the stitching should not cross over between the
band members in a way that would restrict flexibility). The liner
12 will usually pass outward from the inner lumen of the tubular
frame 14 to the exterior of the frame through the gap between
adjacent band members, as illustrated in FIG. 1. The portion of
liner 12 on the exterior of the tubular frame 14 helps seal the
end(s) of the graft 10 against the wall of the blood vessel or
other body lumen in which it is disposed.
[0043] The joining pattern of adjacent band members 11 is best
illustrated in FIGS. 3A and 3B. FIG. 3A illustrates the tubular
frame 14 as it would look if unrolled onto a flat surface. FIG. 3B
is similar to FIG. 3A, except that the band members are expanded.
The expansion is shown at 30.degree., but will frequently extend up
to 60.degree. or higher in use.
[0044] A preferred method for forming the tubular frame 14 in the
present invention may be described with reference to FIG. 4. A tube
of the desired elastic material, such as nickel titanium alloy
having a phase transformation temperature significantly below
37.degree. C., preferably between 30.degree. C. and 32.degree. C.,
is obtained. The tube will have dimensions roughly equal to the
desired dimensions of the frame when radially compressed. The tube
may be drawn, rolled, or otherwise treated to achieve the desired
wall thickness, diameter, and the like. Suitable wall thicknesses
are in the range of about 0.1 mm to 0.5 mm. A pattern of axial
slots is then formed in the tube, as illustrated in FIG. 4. The
slots may be formed by electrical discharge machining (EDM),
photochemical etching, laser cutting, machining or other
conventional techniques. After the slots have been formed, the tube
is mechanically expanded to its desired final (relaxed) diameter
and heat treated at a suitable temperature to set the tube in the
desired expanded state. Sharp edges are removed by conventional
techniques, such as deburring, abrasive extrusion, or the like. The
result of the expansion is the tubular frame illustrated in FIGS. 1
and 2.
[0045] Preferably, each end of the liner 12 will be
circumferentially sealed at or near the distal and proximal ends of
the tubular graft. As illustrated in FIG. 1A, this can be achieved
by folding over the end of the liner 12 onto the external surface
of the graft 10. Conveniently, this can be done through the gaps
which are present between adjacent band members 14. Where the
junctions 13 remain, the liner 12 can be carefully stitched onto
the underlying surface of the frame, as shown at 18 in FIG. 1A.
Other techniques for circumferentially sealing the liner include
heat or ultrasonic welding of the liner, laminating an outer
gasket, sewing an outer reinforcement member, or the like.
[0046] Referring now to FIG. 1A, an alternative embodiment 100 of a
vascular graft constructed in accordance with the principles of the
present invention will be described. The graft 100 comprises a
perforate tubular frame 102 which includes a plurality of
independent (non-connected) band members 104 separated from each
other by gaps 106. The perforate tubular frame 102 is similar in
construction to frame 14 of graft 10, except that adjacent band
members 104 are not directly connected to each other. Band numbers
104 will be connected only by an inner liner 108 and an outer liner
110, where the inner and outer liners together encase or sandwich
the otherwise free-floating band members 104. In order to secure
the band members 104 in place, and secure the liners to the
perforate tubular frame 102, the inner and outer liners are joined
together along circumferential lines 112, preferably located in the
gaps 106 between adjacent band members 104. The liners may be
joined together by stitching, heat welding, ultrasonic welding, or
the like. In the exemplary embodiment, the liners 108 and 110 are
formed from polymeric sheet material and are joined together by
ultrasonic welding. The band members 104 at each end of the graft
100 will have to be further secured to the liners 108 and 110. For
example, they could be stitched, welded, or otherwise joined to the
liners to hold them in place. The dimensions, materials, and other
aspects of the graft 100 will be generally the same as those
described previously for graft 10.
[0047] Referring now to FIG. 1B, a second alternative embodiment
200 of the vascular graft of the present invention is illustrated.
The graft 200 comprises a perforate tubular frame 202 including a
plurality of laterally compressible axial members 204. Each axial
member 204 comprises a plurality of diamond-shaped structural
elements which are connected to each other in a linear fashion. It
will be appreciated that each diamond-shaped structural element is
laterally compressible so that the frame 202 as a whole may be
radially compressed from a reduced-diameter configuration to an
expanded-diameter configuration. As illustrated in FIG. 1B, the
frame is in a partially compressed configuration. The axial members
202 will be captured between an inner liner 206 and an outer liner
208. The inner liner 206 and outer liner 208 will be secured to
each other along a plurality of axial lines 210 disposed between
adjacent axial members 204. In this way, each axial member 204 will
be captured within a pocket formed between the inner liner 206 and
outer liner 208. As with previous embodiments, the ends of the
frame may extend beyond the liners to provide for improved
anchoring and perfusion on either side of the graft.
[0048] Referring now to FIG. 5, a bifurcated base structure for
forming a bifurcated graft in combination with a pair of the
vascular grafts 10 just discussed will be described. The bifurcated
base structure 20 comprises an anchor segment 22, which typically
will be a radially compressible perforate frame having a structure
similar or identical to that just discussed. The frame of anchor 22
will typically have a length in the range from about 5 mm to 50 mm,
and a diameter in the range from about 5 mm to 30 mm. A liner 24
will be disposed within the frame 22, typically being
circumferentially sealed near the upper end of the frame, e.g.,
being folded over and stitched as described previously. As with the
straight graft embodiment of FIGS. 1-4, the proximal end of the
liner 24 will preferably be distally spaced-apart from the proximal
end of the anchor segment 22, typically by a distance in the range
from 1 mm to 25 mm. The fabric 24 defines a common flow lumen at
its upper end and a pair of divergent flow lumens at its lower end,
one in each leg 26 and 28. The legs 26 and 28 are preferably not
covered by the frame of anchor 22. The fabric legs 26 and 28 will
each have a diameter in the range from 6 mm to 18 mm and a length
in the range from 5 mm to 30 mm. The dimensions of each leg need
not be the same.
[0049] Referring now to FIG. 6, a catheter 30 for delivering the
vascular graft 10 or bifurcated base structure 20 will be
described. The catheter 30 includes a shaft 32 having a pair of
axially spaced-apart stays 34 and 36. A pull wire 38 extends
through a lumen 40 of shaft 32 and through protrusions on each of
the stays 34 and 36. A sheath 42 is slidably disposed over the
shaft 32 so that it may be advanced over the stays 34 and 36.
Guidewire 34 extends through the shaft 32 and shaft extension 46 to
facilitate vascular introduction of the catheter 30. A radially
compressible graft G (such as graft 10) is placed over the distal
end of the shaft extension 46, generally being aligned between the
stays 34 and 36. The pull wire 38 is then advanced through the
stays 34 and 36 so that it passes through each end of the graft G
to maintain the graft in place until the pull wire is withdrawn.
While the pull wire 38 remains in place, the sheath 42 may be
axially advanced over the graft to radially compress the graft into
its desired low profile diameter. The sheath 42 includes a flared
(i.e., outwardly tapered) distal end 46 to facilitate advancing the
sheath over the graft, in particular so that the graft may be
recaptured when it is partially deployed, as described hereinafter.
The outward taper may be permanently fixed in the body of the
sheath, but will preferably be selectively deployable between the
tapered configuration and a non-tapered or straight configuration
(shown in broken line) to facilitate introduction of the sheath
through the vasculature or other body lumen. A variety of suitable
mechanisms for selectively expanding the distal end of the sheath
are known in the art, such as pull wires and the like. The sheath
42 will be introduced through the vasculature through a
conventional introducer sleeve having a proximal hemostasis
valve.
[0050] The catheter 30 may be modified to provide alternate
delivery techniques for the graft G. For example, the catheter 30
may include a balloon at or near its distal end for use with grafts
having malleable portions which need to be expanded. The catheter
30 might also include bumpers or other means for aligning the graft
on the shaft 46 while the sheath 42 is being retracted. A variety
of other catheter constructions and techniques for delivering the
radially-compressible graft and stent structures of the present
invention.
[0051] Referring now to FIGS. 7-12, placement of a bifurcated graft
structure in an abdominal aortic aneurysm AA of a patient will be
described. Initially, the delivery catheter 30 is introduced
through an introducer sleeve 50 via an antegrade approach (e.g. the
subclavian artery SC), as illustrated in FIG. 7. The bifurcated
base structure is initially maintained within sheath 42 so that it
remains radially compressed. After the compressed base structure 20
is properly positioned, the sheath 42 will be withdrawn, allowing
the base structure 20 to expand in place, as illustrated in FIG. 8.
The catheter 30 may then be withdrawn, leaving the guidewire GW in
place. A vascular graft 10 is then mounted on the catheter 30 and
reintroduced so that the compressed vascular graft lies within the
fabric liner leg 28 while covered with sheath 42, as illustrated in
FIG. 9. The sheath 42 is then withdrawn so that the vascular graft
10 will expand both within the leg 28 and the left iliac LI, as
illustrated in FIG. 10. The catheter 30 is then withdrawn, and the
guidewire is transferred from the left iliac LI to the right iliac
RI. Alternatively, a separate guidewire could be introduced.
Catheter 30 is then reintroduced over the guidewire with sheath 42
covering a second vascular graft 10 and advanced into the right
iliac, as illustrated in FIG. 11. The sheath 42 is then withdrawn,
allowing the second vascular graft 10 to expand within both the
right iliac RI and the second leg 26 of the fabric liner. The
completed bifurcated graft structure is then in place, as
illustrated in FIG. 12, and the guidewire GW, catheter 30, and
introducer sheath 50 may then be withdrawn.
[0052] Femoral access and retrograde placement of the graft
structures of the present invention will be possible although such
an approach is not presently preferred.
[0053] Positioning and repositioning of the stent-graft structure
of the present invention can be facilitated by use of an ultrasonic
imaging catheter or guidewire, such as the guidewires described in
U.S. Pat. No. 5,095,911 and PCT WO 93/16642. Such ultrasonic
guidewires can be used in place of the conventional guidewire 30
illustrated in FIGS. 7-12, typically being sealed by a hemostasis
valve at the proximal end of the delivery catheter 30. Locking
means, clamps, markings, and the like, may be provided on either or
both of the delivery catheter 30 and the imaging guidewire to
assure proper positioning of the ultrasonic transducer within the
stent-graft structure during the placement procedure. The aneurysm
or other anomaly being treated can then be precisely located prior
to release of the stent-graft 10. After partial placement, proper
location of the stent-graft 10 can be confirmed with the ultrasonic
imaging device. If the position is not correct, the stent-graft 10
can be drawn back into the sheath 42, and the stent-graft be
repositioned prior to complete release. The use of an ultrasonic
imaging guidewire is advantageous since there is no need to
exchange the guidewire for a separate ultrasonic imaging
catheter.
[0054] Although the foregoing invention has been described in some
detail by way of illustration and example, for purposes of clarity
of understanding, it will be obvious that certain changes and
modifications may be practiced within the scope of the appended
claims.
* * * * *