U.S. patent application number 10/755703 was filed with the patent office on 2004-10-14 for endoluminal vascular prosthesis.
Invention is credited to Henson, Michael R., Hoffmann, Gerard von, Shokoohi, Mehrdad M..
Application Number | 20040204753 10/755703 |
Document ID | / |
Family ID | 21877986 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040204753 |
Kind Code |
A1 |
Shokoohi, Mehrdad M. ; et
al. |
October 14, 2004 |
Endoluminal vascular prosthesis
Abstract
Disclosed is a tubular endoluminal vascular prosthesis, useful
in treating, for example, an abdominal aortic aneurysm. The
prosthesis comprises a self expandable wire support structure
surrounded by a flexible tubular membrane. A delivery catheter and
methods are also disclosed.
Inventors: |
Shokoohi, Mehrdad M.;
(Rancho Palos Verdes, CA) ; Henson, Michael R.;
(Trabuco Canyon, CA) ; Hoffmann, Gerard von;
(Trabuco Canyon, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
21877986 |
Appl. No.: |
10/755703 |
Filed: |
January 12, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10755703 |
Jan 12, 2004 |
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10032230 |
Dec 18, 2001 |
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10032230 |
Dec 18, 2001 |
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09483411 |
Jan 14, 2000 |
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6331190 |
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09483411 |
Jan 14, 2000 |
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09034689 |
Mar 4, 1998 |
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6077296 |
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Current U.S.
Class: |
623/1.16 ;
623/909 |
Current CPC
Class: |
A61F 2002/067 20130101;
A61F 2220/0075 20130101; A61F 2002/072 20130101; A61F 2230/0054
20130101; A61F 2/90 20130101; A61F 2002/075 20130101; A61F
2220/0016 20130101; A61F 2002/061 20130101; A61F 2002/828 20130101;
A61F 2/86 20130101; A61F 2220/005 20130101; A61F 2/958 20130101;
A61F 2/07 20130101; A61F 2/954 20130101; A61F 2/966 20130101 |
Class at
Publication: |
623/001.16 ;
623/909 |
International
Class: |
A61F 002/06 |
Claims
1-51. (Canceled)
52. An endoluminal prosthesis, comprising: a tubular wire support
having a proximal end, a distal end and a central lumen extending
therethrough; the wire support comprising a plurality of tabular
segments, each tabular segment comprising a series of proximal and
distal bends, wherein the tubular segments are joined by a
connector extending therebetween; the plurality of tubular segments
extending from a proximal region of the tubular wire support to a
distal region of the tubular wire support; wherein the distal
region of the wire support radially expands in response to distally
directed anatomical forces on the tubular wire support to increase
resistance to distal migration of the prosthesis.
53. The endoluminal prosthesis as in claim 52, wherein the
prostheses is self expandable from a first smaller diameter to a
second larger diameter.
54. An endoluminal prosthesis as in claim 52, further comprising a
polymeric sleeve on the wire support.
55. An endoluminal prosthesis as in claim 54, wherein the polymeric
sleeve comprises ePTFE.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 09/034,689 filed on Mar. 4, 1998.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to endoluminal vascular
prostheses, and, in one application, to self-expanding endoluminal
vascular prostheses for use in the treatment of abdominal aortic
aneurysms.
[0003] An abdominal aortic aneurysm is a sac caused by an abnormal
dilation of the wall of the aorta, a major artery of the body, as
it passes through the abdomen. The abdomen is that portion of the
body which lies between the thorax and the pelvis. It contains a
cavity, known as the abdominal cavity, separated by the diaphragm
from the thoracic cavity and lined with a serous membrane, the
peritoneum. The aorta is the main trunk, or artery, from which the
systemic arterial system proceeds. It arises from the left
ventricle of the heart, passes upward, bends over and passes down
through the thorax and through the abdomen to about the level of
the fourth lumbar vertebra, where it divides into the two common
iliac arteries.
[0004] The aneurysm usually arises in the infrarenal portion of the
diseased aorta, for example, below the kidneys. When left
untreated, the aneurysm may eventually cause rupture of the sac
with ensuing fatal hemorrhaging in a very short time. High
mortality associated with the rupture led initially to
transabdominal surgical repair of abdominal aortic aneurysms.
Surgery involving the abdominal wall, however, is a major
undertaking with associated high risks. There is considerable
mortality and morbidity associated with this magnitude of surgical
intervention, which in essence involves replacing the diseased and
aneurysmal segment of blood vessel with a prosthetic device which
typically is a synthetic tube, or graft, usually fabricated of
Polyester, Urethane, P, DACRON.RTM., TEFLON.RTM., or other suitable
material.
[0005] To perform the surgical procedure requires exposure of the
aorta through an abdominal incision which can extend from the rib
cage to the pubis. The aorta must be closed both above and below
the aneurysm, so that the aneurysm can then be opened and the
thrombus, or blood clot, and arteriosclerotic debris removed. Small
arterial branches from the back wall of the aorta are tied off. The
DACRON.RTM. tube, or graft, of approximately the same size of the
normal aorta is sutured in place, thereby replacing the aneurysm.
Blood flow is then reestablished through the graft. It is necessary
to move the intestines in order to get to the back wall of the
abdomen prior to clamping off the aorta.
[0006] If the surgery is performed prior to rupturing of the
abdominal aortic aneurysm, the survival rate of treated patients is
markedly higher than if the surgery is performed after the aneurysm
ruptures, although the mortality rate is still quite high. If the
surgery is performed prior to the aneurysm rupturing, the mortality
rate is typically slightly less than 10%. Conventional surgery
performed after the rupture of the aneurysm is significantly
higher, one study reporting a mortality rate of 66.5%. Although
abdominal aortic aneurysms can be detected from routine
examinations, the patient does not experience any pain from the
condition. Thus, if the patient is not receiving routine
examinations, it is possible that the aneurysm will progress to the
rupture stage, wherein the mortality rates are significantly
higher.
[0007] Disadvantages associated with the conventional, prior art
surgery, in addition to the high mortality rate include the
extended recovery period associated with such surgery; difficulties
in suturing the graft, or tube, to the aorta; the loss of the
existing aorta wall and thrombosis to support and reinforce the
graft; the unsuitability of the surgery for many patients having
abdominal aortic aneurysms; and the problems associated with
performing the surgery on an emergency basis after the aneurysm has
ruptured. A patient can expect to spend from one to two weeks in
the hospital after the surgery, a major portion of which is spent
in the intensive care unit, and a convalescence period at home from
two to three months, particularly if the patient has other
illnesses such as heart, lung, liver, and/or kidney disease, in
which case the hospital stay is also lengthened. Since the graft
must be secured, or sutured, to the remaining portion of the aorta,
it is many times difficult to perform the suturing step because the
thrombosis present on the remaining portion of the aorta, and that
remaining portion of the aorta wall may many times be friable, or
easily crumbled.
[0008] Since many patients having abdominal aortic aneurysms have
other chronic illnesses, such as heart, lung, liver, and/or kidney
disease, coupled with the fact that many of these patients are
older, the average age being approximately 67 years old, these
patients are not ideal candidates for such major surgery.
[0009] More recently, a significantly less invasive clinical
approach to aneurysm repair, known as endovascular grafting, has
been developed. Parodi, et al. provide one of the first clinical
descriptions of this therapy. Parodi, J. C., et al., "Transfemoral
Intraluminal Graft Implantation for Abdominal Aortic Aneurysms," 5
Annals of Vascular Surgery 491 (1991). Endovascular grafting
involves the transluminal placement of a prosthetic arterial graft
in the endoluminal position (within the lumen of the artery). By
this method, the graft is attached to the internal surface of an
arterial wall by means of attachment devices (expandable stents),
typically one above the aneurysm and a second stent below the
aneurysm.
[0010] Stents permit fixation of a graft to the internal surface of
an arterial wall without sewing or an open surgical procedure.
Expansion of radially expandable stents is conventionally
accomplished by dilating a balloon at the distal end of a balloon
catheter. In U.S. Pat. No. 4,776,337, for example, Palmaz describes
a balloon-expandable stent for endovascular treatments. Also known
are self-expanding stents, such as described in U.S. Pat. No.
4,655,771 to Wallsten.
[0011] Notwithstanding the foregoing, there remains a need for a
transluminally implantable endovascular prosthesis, such as for
spanning an abdominal aortic aneurysm. Preferably, the tubular
prosthesis can be self expanded at the site to treat the abdominal
aortic aneurysm.
SUMMARY OF THE INVENTION
[0012] There is provided in accordance with one aspect of the
present invention an endoluminal prosthesis. The endoluminal
prosthesis comprises a tubular wire support having a proximal end,
a distal end and central lumen extending therethrough. The wire
support comprises at least a first and a second axially adjacent
tubular segments, joined by a connector extending therebetween. The
first and second segments and the connector are formed from a
single length of wire.
[0013] In one embodiment, the wire in each segment comprises a
series of proximal bends, a series of distal bends, and a series of
wall (strut) segments connecting the proximal bends and distal
bends to form a tubular segment wall. Preferably, at least one
proximal bend on a first segment is connected to at least one
corresponding distal bend on a second segment. The connection may
be provided by a metal link, a suture, or other connection means
known in the art.
[0014] Preferably, the endoluminal prosthesis further comprises a
polymeric layer such as a tubular PTFE sleeve, on the support.
[0015] In accordance with another aspect of the present invention,
there is provided a method of making an endoluminal prosthesis. The
method comprises the steps of providing a length of wire, and
forming the wire into two or more zig zag sections, each zig zag
section connected by a link. The formed wire is thereafter rolled
about an axis to produce a series of tubular elements positioned
along the axis such that each tubular element is connected to the
adjacent tubular element by a link. Preferably, the method further
comprises the step of positioning a tubular polymeric sleeve
concentrically on at least a portion of the endoluminal
prosthesis.
[0016] In accordance with another aspect of the present invention,
there is provided a multizone endoluminal prosthesis. The multizone
prosthesis comprises a tubular wire support having a proximal end,
a distal end and a central lumen extending therethrough. The wire
support comprises at least a first and a second axially adjacent
tubular segments, joined by a connector extending therebetween. The
first tubular segment has a different radial strength than the
second tubular segment. In one embodiment, the prosthesis further
comprises a third tubular segment. At least one of the tubular
segments has a different radial strength than the other two tubular
segments. In another embodiment, a proximal end of the prosthesis
is self expandable to a greater diameter than a central region of
the prosthesis.
[0017] In accordance with another aspect of the present invention,
there is provided an endoluminal prosthesis. The prosthesis
comprises an elongate flexible wire, formed into a plurality of
axially adjacent tubular segments spaced along an axis. Each
tubular segment comprises a zig zag section of wire, having a
plurality of proximal bends and distal bends, with the wire
continuing between each adjacent tubular segment creating an
integral structural support system throughout the longitudinal
length of the device. The prothesis is radially collapsible into a
first, reduced cross sectional configuration for implantation into
a body lumen, and self expandable to a second, enlarged cross
sectional configuration at a treatment site in a body lumen.
[0018] Preferably, the prosthesis further comprises an outer
tubular sleeve surrounding at least a portion of the prosthesis.
One or more lateral perfusion ports may be provided through the
tubular sleeve.
[0019] In one embodiment, the prosthesis has an expansion ratio of
at least about 1:5, and, preferably at least about 1:6. The
prosthesis in another embodiment has an expanded diameter of at
least about 20 mm in an unconstrained expansion, and the prosthesis
is implantable using a catheter no greater than about 16 French.
Preferably, the prosthesis has an expanded diameter of at least
about 25 mm, and is implantable on a delivery device having a
diameter of no more than about 16 French.
[0020] In accordance with a further aspect of the present
invention, there is provided a method of implanting an endoluminal
vascular prosthesis. The method comprises the steps of providing a
self expandable endoluminal vascular prosthesis, having a proximal
end, a distal end, and a central lumen extending therethrough. The
prosthesis is expandable from a first, reduced diameter to a
second, enlarged diameter. The prosthesis is mounted on a catheter,
such that when the prosthesis is in the reduced diameter
configuration on the catheter, the catheter diameter through the
prosthesis is no more than about 16 French. The catheter is
thereafter introduced into the body lumen and positioned such that
the prosthesis is at a treatment site in the body lumen. The
prosthesis is released at the treatment site, such that it expands
from the first diameter to the second diameter, wherein the second
diameter is at least about 20 mm.
[0021] Further features and advantages of the present invention
will become apparent to those of ordinary skill in the art in view
of the disclosure herein, when considered together with the
attached drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic representation of an endoluminal
vascular prosthesis in accordance with the present invention,
positioned within a symmetric abdominal aortic aneurysm.
[0023] FIG. 2 is an exploded view of an endoluminal vascular
prosthesis in accordance with the present invention, showing a self
expandable wire support structure separated from an outer tubular
sleeve.
[0024] FIG. 3 is a plan view of a formed wire useful for rolling
about an axis into a multi-segment support structure in accordance
with the present invention.
[0025] FIG. 4 is an enlarged detail view of a portion of the formed
wire illustrated in FIG. 3.
[0026] FIG. 5 is a cross sectional view taken along the lines 5-5
of FIG. 4.
[0027] FIG. 6 is an alternate cross sectional view taken along the
lines 5-5 of FIG. 4.
[0028] FIG. 7 is a fragmentary view of an alternate wire layout in
accordance with a further aspect of the present invention.
[0029] FIG. 8 is an elevational view of a crosslinked wire layout
in accordance with the present invention.
[0030] FIG. 8A is a plan view of a formed wire layout useful for
forming the crosslinked embodiment of FIG. 8.
[0031] FIG. 9 is a fragmentary view of an alternate wire layout in
accordance with a further aspect of the present invention.
[0032] FIG. 10 is a fragmentary view of an alternate wire layout in
accordance with a further aspect of the present invention.
[0033] FIG. 11 is a fragmentary view of an apex in accordance with
one aspect of the present invention.
[0034] FIG. 12 is a fragmentary view of an alternate embodiment of
an apex in accordance with the present invention.
[0035] FIG. 13 is a further embodiment of an apex in accordance
with the present invention.
[0036] FIG. 14 is a fragmentary view of a further wire layout in
accordance with the present invention.
[0037] FIG. 15 is a fragmentary view of a further wire layout in
accordance with the present invention.
[0038] FIG. 16 is a fragmentary view of a further wire layout in
accordance with the present invention.
[0039] FIG. 17 is a schematic illustration of a delivery catheter
in accordance with the present invention, positioned within an
abdominal aortic aneurysm.
[0040] FIG. 18 is an illustration as in FIG. 17, with the
endoluminal prosthesis partially deployed from the delivery
catheter.
[0041] FIG. 19 is a cross sectional view taken along the lines
19-19 of FIG. 17.
[0042] FIG. 20 is a detailed fragmentary view of a tapered wire
embodiment in accordance with a further aspect of the present
invention.
[0043] FIG. 21 is a schematic representation of the abdominal
aortic anatomy, with an endoluminal vascular prosthesis of the
present invention positioned within each of the right renal artery
and the right common iliac.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0044] Referring to FIG. 1, there is disclosed a schematic
representation of the abdominal part of the aorta and its principal
branches. In particular, the abdominal aorta 30 is characterized by
a right renal artery 32 and left renal artery 34. The large
terminal branches of the aorta are the right and left common iliac
arteries 36 and 38. Additional vessels (e.g., second lumbar,
testicular, inferior mesenteric, middle sacral) have been omitted
for simplification. A generally symmetrical aneurysm 40 is
illustrated in the infrarenal portion of the diseased aorta. An
expanded endoluminal vascular prosthesis 42, in accordance with the
present invention, is illustrated spanning the aneurysm 40.
Although features of the endoluminal vascular prosthesis of the
present invention can be modified for use in a bifurcation
aneurysm, such as the common iliac bifurcation, the endoluminal
prosthesis of the present invention will be described herein
primarily in terms of its application in the straight segment of
the abdominal aorta, or Thoracic or iliac arteries.
[0045] The endoluminal vascular prosthesis 42 includes a polymeric
sleeve 44 and a tubular wire support 46, which are illustrated in
situ in FIG. 1. The sleeve 44 and wire support 46 are more readily
visualized in the exploded view shown in FIG. 2. The endoluminal
prosthesis 42 illustrated and described herein depicts an
embodiment in which the polymeric sleeve 44 is situated
concentrically outside of the tubular wire support 46. However,
other embodiments may include a sleeve situated instead
concentrically inside the wire support or on both of the inside and
the outside of the wire support. Alternatively, the wire support
may be embedded within a polymeric matrix which makes up the
sleeve. Regardless of whether the sleeve 44 is inside or outside
the wire support 46, the sleeve may be attached to the wire support
by any of a variety of means, including laser bonding, adhesives,
clips, sutures, dipping or spraying or others, depending upon the
composition of the sleeve 44 and overall graft design.
[0046] The polymeric sleeve 44 may be formed from any of a variety
of synthetic polymeric materials, or combinations thereof,
including PTFE, PE, PET, Urethane, Dacron, nylon, polyester or
woven textiles. Preferably, the sleeve material exhibits relatively
low inherent elasticity, or low elasticity out to the intended
enlarged diameter of the wire cage 46. The sleeve material
preferably has a thin profile, such as no larger than about 0.002
inches to about 0.005 inches.
[0047] In a preferred embodiment of the invention, the material of
sleeve 44 is sufficiently porous to permit ingrowth of endothelial
cells, thereby providing more secure anchorage of the prosthesis
and potentially reducing flow resistance, sheer forces, and leakage
of blood around the prosthesis. Porosity in polymeric sleeve
materials may be estimated by measuring water permeability as a
function of hydrostatic pressure, which will preferably range from
about 3 to 6 psi.
[0048] The porosity characteristics of the polymeric sleeve 44 may
be either homogeneous throughout the axial length of the prosthesis
42, or may vary according to the axial position along the
prosthesis 42. For example, referring to FIGS. 1 and 2, different
physical properties will be called upon at different axial
positions along the prosthesis 42 in use. At least a proximal
portion 55 and a distal portion 59 of the prosthesis 42 will seat
against the native vessel wall, proximally and distally of the
aneurysm. In these proximal and distal portions, the prosthesis
preferably encourages endothelial growth, or, at least, permits
endothelial growth to infiltrate portions of the prosthesis in
order to enhance anchoring and minimize leakage. A central portion
57 of the prosthesis spans the aneurysm, and anchoring is less of
an issue. Instead, minimizing blood flow through the prosthesis
wall becomes a primary objective. Thus, in a central zone 57 of the
prosthesis 42, the polymeric sleeve 44 may either be nonporous, or
provided with pores of no greater than about 60% to 80%.
[0049] A multi-zoned prosthesis 42 may also be provided in
accordance with the present invention by positioning a tubular
sleeve 44 on a central portion 57 of the prosthesis, such that it
spans the aneurysm to be treated, but leaving a proximal attachment
zone 55 and a distal attachment zone 59 of the prosthesis 42 having
exposed wires from the wire support 46. In this embodiment, the
exposed wires 46 are positioned in contact with the vessel wall
both proximally and distally of the aneurysm, such that the wire,
over time, becomes embedded in cell growth on the interior surface
of the vessel wall.
[0050] In one embodiment of the prosthesis 42, the sleeve 44 and/or
the wire support 46 is tapered, having a relatively larger expanded
diameter at the proximal end 50 compared to the distal end 52. The
tapered design may allow the prosthesis to conform better to the
natural decreasing distal cross section of the vessel, to reduce
the risk of graft migration and potentially create better flow
dynamics.
[0051] The tubular wire support 46 is preferably formed from a
continuous single length of round (shown in FIG. 5) or flattened
(shown in FIG. 6) wire. The wire support 46 is preferably formed in
a plurality of discrete segments 54, connected together and
oriented about a common axis. Each pair of adjacent segments 54 is
connected by a connector 66 as will be discussed. The connectors 66
collectively produce a generally axially extending backbone which
adds axial strength to the prosthesis 42. Adjacent segments can be
connected both by the backbone, as well as by other structures,
including circumferentially extending sutures 56 (illustrated in
FIGS. 1 and 2), solder joints, wire loops and any of a variety of
interlocking relationships. The suture can be made from any of a
variety of biocompatible polymeric materials or alloys, such as
nylon, polypropylene, or stainless steel. Other means of securing
the segments 54 to one another are discussed below (see FIG.
8).
[0052] The segmented configuration of the tubular wire support 46
facilitates a great deal of flexibility. Each segment 54, though
joined to adjacent segments, may be independently engineered to
yield desired parameters. Each segment may range in axial length
from about 0.3 to about 5 cm. Generally, the shorter their length
the greater the radial strength. An endoluminal prosthesis may
include from about 1 to about 50 segments, preferably from about 3
to about 10 segments. For example, while a short graft patch, in
accordance with the invention, may comprise only 2 segments and
span a total of 2 to 3 cm, a complete graft may comprise 4 or more
segments and span the entire aortic aneurysm. In addition to the
flexibility and other functional benefits available through
employment of different length segments, further flexibility can be
achieved through adjustments in the number, angle, or configuration
of the wire bends associated with the tubular support. Potential
bend configurations are discussed in greater detail below (see
FIGS. 4-16).
[0053] A variety of additional advantages can be achieved through
the multi-segment configuration of the present invention. For
example, referring to FIG. 2, the wire cage 46 is dividable into a
proximal zone 55, a central zone 57 and a distal zone 59. As has
been discussed, the wire cage 46 can be configured to taper from a
relatively larger diameter in the proximal zone 55 to a relatively
smaller diameter in the distal zone 59. In addition, the wire cage
46 can have a transitional tapered and or stepped diameter within a
given zone.
[0054] The cage 46 can also be provided with a proximal zone 55 and
distal zone 59 that have a larger relative expanded diameter than
the central zone 57, as illustrated in FIG. 2. This configuration
may desirably resist migration of the prosthesis within the vessel.
The proximal zone 55 and/or distal zone 59 can be left without an
outer covering 44, with the outer sleeve 44 covering only the
central zone 57. This permits the proximal and distal zones 55, 59
to be in direct contact with tissue proximally and distal to the
lesion, which may facilitate endothelial cell growth.
[0055] In addition to having differing expanded diameters in
different zones of the prosthesis 42, different zones can be
provided with a different radial expansion force, such as ranging
from about 0.2 lbs to about 0.8 lbs. In one embodiment, the
proximal zone 55 is provided with a greater radial force than the
central zone 57 and/or distal zone 59. The greater radial force can
be provided in any of a variety of manners discussed elsewhere
herein, such as through the use of an additional one or two or
three or more proximal bends 60, distal bends 62 and wall sections
64 compared to a reference segment 54 in the central zone 57 or
distal zone 59. Alternatively, additional spring force can be
achieved in the proximal zone 55 through the use of the same number
of proximal bends 60 as in the rest of the prosthesis, but with a
heavier gauge wire. Radial force beyond the expanded diameter limit
of the central zone 57 can be achieved by tightening the suture 56
as illustrated in FIG. 2 such that the central zone 57 is retained
under compression even in the expanded configuration. By omitting a
suture at the proximal end and/or distal end of the prosthesis, the
proximal end and distal end will flair radially outwardly to a
fully expanded configuration as illustrated in FIG. 2.
[0056] The wire may be made from any of a variety of different
alloys, such as elgiloy, nitinol or MP35N, or other alloys which
include nickel, titanium, tantalum, or stainless steel, high Co--Cr
alloys or other temperature sensitive materials. For example, an
alloy comprising Ni 15%, Co 40%, Cr 20%, Mo 7% and balance Fe may
be used. The tensile strength of suitable wire is generally above
about 300 K psi and often between about 300 and about 340 K psi for
many embodiments. In one embodiment, a Chromium-Nickel-Molybdenum
alloy such as that marketed under the name Conichrom (Fort Wayne
Metals, Indiana) has a tensile strength ranging from 300 to 320 K
psi, elongation of 3.5-4.0% and breaking load at approximately 80
lbs to 70 lbs. The wire may be treated with a plasma coating and be
provided with/without coating such as: PTFE, Teflon, Perlyne and
Drugs.
[0057] In addition to segment length and bend configuration,
discussed above, another determinant of radial strength is wire
gauge. The radial strength, measured at 50% of the collapsed
profile, preferably ranges from about 0.2 lb to 0.8 lb, and
generally from about 0.4 lb to about 0.5 lb. or more. Preferred
wire diameters in accordance with the present invention, range from
about 0.004 inches to about 0.020 inches. More preferably, the wire
diameters range from about 0.006 inches to about 0.018 inches. In
general, the greater the wire diameter, the greater the radial
strength for a given wire layout. Thus, the wire gauge can be
varied depending upon the application of the finished graft, in
combination with/or separate from variation in other design
parameters (such as the number of struts, or proximal bends 60 and
distal bends 62 per segment), as will be discussed. A wire diameter
of approximately 0.018 inches may be useful in a graft having four
segments each having 2.5 cm length per segment, each segment having
six struts intended for use in the aorta, while a smaller diameter
such as 0.006 inches might be useful for a 0.5 cm segment graft
having 5 struts per segment intended for the iliac artery. The
length of cage 42 could be as long as about 28 cm.
[0058] In one embodiment of the present invention, the wire
diameter is tapered from the proximal to distal ends.
Alternatively, the wire diameter may be tapered incrementally or
stepped down, or stepped up, depending on the radial strength
requirements of each particular clinical application. In one
embodiment, intended for the abdominal aortic artery, the wire has
a cross section of about 0.018 inches in the proximal zone 55 and
the wire tapers down to a diameter of about 0.006 inches in the
distal zone 59 of the graft 42. End point dimensions and rates of
taper can be varied widely, within the spirit of the present
invention, depending upon the desired clinical performance.
[0059] Referring to FIG. 3, there is illustrated a plan view of the
single formed wire used for rolling about a longitudinal axis to
produce a four segment tubular wire support. The formed wire
exhibits distinct segments, each corresponding to an individual
tubular segment 54 in the tubular support (see FIGS. 1 and 2).
[0060] Each segment has a repeating pattern of proximal bends 60
connected to corresponding distal bends 62 by wall sections 64
which extend in a generally zig zag configuration when the segment
54 is radially expanded. Each segment 54 is connected to the
adjacent segment 54 through a connector 66, except at the terminal
ends of the graft. The connector 66 in the illustrated embodiment
comprises two wall sections 64 which connect a proximal bend 60 on
a first segment 54 with a distal bend 62 on a second, adjacent
segment 54. The connector 66 may additionally be provided with a
connector bend 68, which may be used to impart increased radial
strength to the graft and/or provide a tie site for a
circumferentially extending suture.
[0061] Referring to FIG. 4, there is shown an enlarged view of the
wire support illustrating a connector 66 portion between adjacent
segments 54. In the embodiment shown in FIG. 4, a proximal bend 60
comprises about a 180 degree arc, having a radial diameter of (w)
(Ranging from 0.070 to 0.009 inches), depending on wire diameter
followed by a relatively short length of parallel wire spanning an
axial distance of d1. The parallel wires thereafter diverge
outwardly from one another and form the strut sections 64, or the
proximal half of a connector 66. At the distal end of the strut
sections 64, the wire forms a distal bend 62, preferably having
identical characteristics as the proximal bend 60, except being
concave in the opposite direction. The axial direction component of
the distance between the apices of the corresponding proximal and
distal bends 60, 62 is referred to as (d) and represents the axial
length of that segment. The total expanded angle defined by the
bend 60 and the divergent strut sections 64 is represented by
.alpha.. Upon compression to a collapsed state, such as when the
graft is within the deployment catheter, the angle .alpha. is
reduced to .alpha.'. In the expanded configuration, .alpha. is
generally within the range of from about 35.degree. to about
45.degree.. The expanded circumferential distance between any two
adjacent distal bends 62 (or proximal bends 60) is defined as
(s).
[0062] In general, the diameter W of each proximal bend 60 or
distal bend 62 is within the range of from about 0.009 inches to
about 0.070 inches depending upon the wire diameter. Diameter W is
preferably as small as possible for a given wire diameter and wire
characteristics. As will be appreciated by those of skill in the
art, as the distance W is reduced to approach two times the cross
section of the wire, the bend 60 or 62 will exceed the elastic
limit of the wire, and radial strength of the finished segment will
be lost. Determination of a minimum value for W, in the context of
a particular wire diameter and wire material, can be readily
determined through routine experimentation by those of skill in the
art. Similarly, although at least some distance of d1 is desired,
from the apex to the first bend in the wall section 64, the
distance d1 is preferably minimized within the desired radial
strength performance requirements. As d1 increases, it may
disadvantageously increase the collapsed profile of the graft.
[0063] As will be appreciated from FIGS. 3 and 4, the sum of the
distances (s) in a plane transverse to the longitudinal axis of the
finished graft will correspond to the circumference of the finished
graft in that plane. For a given circumference, the number of
proximal bends 60 or distal bends 62 is directly related to the
distance (s) in the corresponding plane. Preferably, the finished
graft in any single transverse plane will have from about 3 to
about 10 (s) dimensions, preferably from about 4 to about 8 (s)
dimensions and, more preferably, about 5 or 6 (s) dimensions for an
aortic application. Each (s) dimension corresponds to the distance
between any two adjacent bends 60-60 or 62-62 as will be apparent
from the discussion herein. Each segment 54 can thus be visualized
as a series of triangles extending circumferentially around the
axis of the graft, defined by a proximal bend 60 and two distal
bends 62 or the reverse.
[0064] By modifying wire support parameters (such as d, d1, s,
alpha and alpha), the manufacturer enjoys tremendous design control
with respect to the total axial length, axial and radial
flexibility, radial force and expansion ratios, and consequently
prosthesis performance. For example, an increase in the dimension
(w) translates directly into an increased collapsed profile since
the circumference of the collapsed profile can be no smaller than
the sum of the distances (w) in a given transverse plane.
Similarly, an increase in the number of proximal bends 60 in a
given segment may increase radial strength, but will similarly
increase the collapsed profile. Since the primary radial force
comes from the proximal bends 60 and distal bends 62, the wall
sections 64 act as a lever arm for translating that force into
radial strength. As a consequence, decreasing the length of strut
sections 64 for a given number of proximal bends 60 will increase
the radial strength of the segment but call for additional segments
to maintain overall graft length. Where a minimal entry profile is
desired, radial strength is best accomplished by decreasing the
length of wall sections 64 rather than increasing the number of
proximal bends 60. On the other hand, increasing the number of
(shorter) segments 54 in a given overall length graft will increase
the degree of axial shortening upon radial expansion of the graft.
Thus, in an embodiment where axial shortening is to be avoided,
increased radial strength may be optimized through selection of
wire material or wire gauge and other parameters, while minimizing
the number of total segments in the graft. Other geometry
consequences of the present invention will be apparent to those of
skill in the art in view of the disclosure herein.
[0065] In one embodiment of the type illustrated in FIG. 8A, w is
about 2.0 mm.+-.1 mm for a 0.018 inch wire diameter. D1 is about 3
mm.+-.1 mm, d is about 20 mm.+-.1 mm, c is about 23 mm.+-.1 mm, g
is about 17 mm,.+-.1 mm, a is about 3 mm.+-.1 mm and b is about 3
mm.+-.1 mm. Specific dimensions for all of the foregoing variables
can be varied considerably, depending upon the desired wire
configuration, in view of the disclosure herein.
[0066] Referring to FIG. 7, there is shown an alternative wire
layout having a plurality of radiussed bends 70 in one or more
sections of strut 64 which may be included to provide additional
flex points to provide enhanced fluid dynamic characteristics and
maintain the tubular shape.
[0067] In another embodiment of the wire support, illustrated in
FIG. 8, each pair of adjacent proximal and distal segments, 76 and
78, may be joined by crosslinking of the corresponding proximal and
distal bends. Thus, a proximal bend 60 from a distal segment 78 is
connected to the corresponding distal bend 62 of a proximal segment
76, thereby coupling the proximal segment 76 and distal segment 78.
The connection between corresponding proximal bends 60 and distal
bends 62 can be accomplished in any of a variety of ways as will be
apparent to those of skill in the art in view of the disclosure
herein. In the illustrated embodiment, the connection is
accomplished through the use of a link 72. Link 72 may be a loop of
metal such as stainless steel, a suture, a welded joint or other
type of connection. Preferably, link 72 comprises a metal loop or
ring which permits pivotable movement of a proximal segment 76 with
respect to a distal segment 78.
[0068] In one example of an endoluminal vascular prosthesis in
accordance with the present invention, the proximal segment 76 is
provided with six distal bends 62. The corresponding distal segment
78 is provided with six proximal bends 60 such that a one to one
correspondence exists. A link 72 may be provided at each pair of
corresponding bends 60, 62, such that six links 72 exist in a plane
transverse to the longitudinal axis of the graft at the interface
between the proximal segment 76 and the distal segment 78.
Alternatively, links 72 can be provided at less than all of the
corresponding bends, such as at every other bend, every third bend,
or only on opposing sides of the graft. The distribution of the
links 72 in any given embodiment can be selected to optimize the
desired flexibility characteristics and other performance criteria
in a given design.
[0069] The use of connectors such as cross link 72 enables improved
tracking of the graft around curved sections of the vessel. In
particular, the wire cage 46 as illustrated in FIG. 8 can be bent
around a gentle curve, such that it will both retain the curved
configuration and retain patency of the central lumen extending
axially therethrough. The embodiment illustrated in FIG. 2 may be
more difficult to track curved anatomy while maintaining full
patency of the central lumen. The ability to maintain full patency
while extending around a curve may be desirable in certain
anatomies, such as where the aorta fails to follow the linear
infrarenal path illustrated in FIG. 1.
[0070] Referring to FIG. 8a, there is illustrated a plan view of a
formed wire useful for rolling about an axis to produce a
multi-segmented support structure of the type illustrated in FIG.
8. In general, the formed wire of FIG. 8a is similar to that
illustrated in FIG. 3. However, whereas any given pair of
corresponding distal bends 62 and proximal bends 60 of the
embodiment of FIG. 3 overlap in the axial direction to facilitate
threading a circumferential suture therethrough, the corresponding
distal bend 62 and proximal bend 60 of the embodiment illustrated
in FIG. 8a may abut end to end against each other or near each
other as illustrated in FIG. 8 to receive a connector 72
thereon.
[0071] The appropriate axial positioning of a distal bend 62 with
respect to a corresponding proximal bend 60 can be accomplished in
a variety of ways, most conveniently by appropriate formation of
the connector bend 68 between adjacent segments of the wire
cage.
[0072] FIGS. 9-16 illustrate alternative bend configurations in
accordance with the present invention. FIG. 9 shows one embodiment
having the proximal and distal bends as eyelets, but the connector
bend 68, remaining in the usual configuration. The embodiment
illustrated in FIG. 10 has the proximal and distal bends as well as
the connector bend in the eyelet configuration. Various eyelet
designs in accordance with the present invention are shown in
greater detail in FIGS. 11-13, including a double-looped circular
eyelet (FIG. 11), a double-looped triangular eyelet (FIG. 12), and
a single-looped triangular eyelet (FIG. 13). The eyelets can be
used to receive a circumferentially extending suture or wire as has
been described.
[0073] Additional embodiments of the wire configuration are
illustrated in FIGS. 14-16. FIG. 14 shows an embodiment of the
proximal 60 and distal 62 bends in which double bends are employed
to increase the flexion. Alternatively, FIG. 15 shows triangular
bends having a more pronounced length (d1) of parallel wire, and
accordingly shorter wall sections 64. Another embodiment of the
proximal and distal bends is shown in FIG. 16, wherein the
triangular bends include additional flexion points in the form of
wall segment bends 70.
[0074] Referring to FIGS. 17 and 18, a deployment device and method
in accordance with a preferred embodiment of the present invention
are illustrated. A delivery catheter 80, having a dilator tip 82,
is advanced along guidewire 84 until the (anatomically) proximal
end 50 of the collapsed endoluminal vascular prosthesis 86 is
positioned between the renal arteries 32 and 34 and the aneurysm
40. The collapsed prosthesis in accordance with the present
invention has a diameter in the range of about 2 to about 10 mm.
Preferably, the diameter of the collapsed prosthesis is in the
range of about 3 to 6 mm (12 to 18 French). More preferably, the
delivery catheter including the prosthesis will be 16 F, or 15 F or
14 F or smaller.
[0075] The prosthesis 86 is maintained in its collapsed
configuration by the restraining walls of the tubular delivery
catheter 80, such that removal of this restraint would allow the
prosthesis to self expand. Radiopaque marker material may be
incorporated into the delivery catheter 80, and/or the prosthesis
86, at least at both the proximal and distal ends, to facilitate
monitoring of prosthesis position. The dilator tip 82 is bonded to
an internal catheter core 92, as illustrated in FIG. 18, wherein
the internal catheter core 92 and the partially expanded prosthesis
88 are revealed as the outer sheath of the delivery catheter 80 is
retracted. The internal catheter core 92 is also depicted in the
cross-sectional view in FIG. 19.
[0076] As the outer sheath is retracted, the collapsed prosthesis
86 remains substantially fixed axially relative to the internal
catheter core 92 and consequently, self-expands at a predetermined
vascular site as illustrated in FIG. 18. Continued retraction of
the outer sheath results in complete deployment of the graft. After
deployment, the expanded endoluminal vascular prosthesis has
radially self-expanded to a diameter anywhere in the range of about
20 to 40 mm, corresponding to expansion ratios of about 1:2 to
1:20. In a preferred embodiment, the expansion ratios range from
about 1:4 to 1:8, more preferably from about 1:4 to 1:6.
[0077] In addition to, or in place of, the outer sheath described
above, the prosthesis 86 may be maintained in its collapsed
configuration by a restraining lace, which may be woven through the
prosthesis or wrapped around the outside of the prosthesis in the
collapsed reduced diameter. Following placement of the prosthesis
at the treatment site, the lace can be proximally retracted from
the prosthesis thereby releasing it to self expand at the treatment
site. The lace may comprise any of a variety of materials, such as
sutures, strips of PTFE, FEP, polyester fiber, and others as will
be apparent to those of skill in the art in view of the disclosure
herein. The restraining lace may extend proximally through a lumen
in the delivery catheter or outside of the catheter to a proximal
control. The control may be a pull tab or ring, rotatable reel,
slider switch or other structure for permitting proximal retraction
of the lace. The lace may extend continuously throughout the length
of the catheter, or may be joined to another axially moveable
element such as a pull wire.
[0078] In general, the expanded diameter of the graft in accordance
with the present invention can be any diameter useful for the
intended lumen or hollow organ in which the graft is to be
deployed. For most arterial vascular applications, the expanded
size will be within the range of from about 10 to about 40 mm.
Abdominal aortic applications will generally require a graft having
an expanded diameter within the range of from about 20 to about 28
mm, and, for example, a graft on the order of about 45 mm may be
useful in the thoracic artery. The foregoing dimensions refer to
the expanded size of the graft in an unconstrained configuration,
such as on the table. In general, the graft will be positioned
within an artery having a slightly smaller interior cross section
than the expanded size of the graft. This enables the graft to
maintain a slight positive pressure against the wall of the artery,
to assist in retention of the graft during the period of time prior
to endothelialization of the polymeric sleeve 44.
[0079] The radial force exerted by the proximal segment 94 of the
prosthesis against the walls of the aorta 30 provides a seal
against the leakage of blood around the vascular prosthesis and
tends to prevent axial migration of the deployed prosthesis. As
discussed above, this radial force can be modified as required
through manipulation of various design parameters, including the
axial length of the segment and the bend configurations. In another
embodiment of the present invention, radial tension can be enhanced
at the proximal, upstream end by changes in the wire gauge as
illustrated in FIG. 20. Note that the wire gauge increases
progressively along the wall segments 64 from T1 at the proximal
bends 60 to T2 at the distal bends 62. Consequently, the radial
flex exerted by the distal bends 62 is greater than that exerted by
the proximal bends 60 and the radial tension is thereby increased
at the proximal end 50 of the prosthesis. T1 may range from about
0.001 to 0.01 inches whereas T2 may range from about 0.01 to 0.03
inches.
[0080] An alternative embodiment of the wire layout which would
cause the radial tension to progressively decrease from the
proximal segments to the distal segments, involves a progressive or
step-wise decrease in the wire gauge throughout the entire wire
support, from about 0.01 to 0.03 inches at the proximal end to
about 0.002 to 0.01 inches at the distal end. Such an embodiment,
may be used to create a tapered prosthesis. Alternatively, the wire
gauge may be thicker at both the proximal and distal ends, in order
to insure greater radial tension and thus, sealing capacity. Thus,
for instance, the wire gauge in the proximal and distal segments
may about 0.01 to 0.03 inches, whereas the intervening segments may
be constructed of thinner wire, in the range of about 0.001 to 0.01
inches.
[0081] Referring to FIG. 21, there is illustrated two alternative
deployment sites for the endoluminal vascular prosthesis 42 of the
present invention. For example, a symmetrical aneurysm 33 is
illustrated in the right renal artery 32. An expanded endoluminal
vascular prosthesis 42, in accordance with the present invention,
is illustrated spanning that aneurysm 33. Similarly, an aneurysm of
the right common iliac 37 is shown, with a prosthesis 42 deployed
to span the iliac aneurysm 37.
[0082] Referring to FIG. 22, there is illustrated a modified
embodiment of the endovascular prosthesis 96 in accordance with the
present invention. In the embodiment illustrated in FIG. 22, the
endovascular prosthesis 96 is provided with a wire cage 46 having
six axially aligned segments 54. As with the previous embodiments,
however, the endovascular prosthesis 96 may be provided with
anywhere from about 2 to about 10 or more axially spaced or
adjacent segments 54, depending upon the clinical performance
objectives of the particular embodiment.
[0083] The wire support 46 is provided with a tubular polymeric
sleeve 44 as has been discussed. In the present embodiment,
however, one or more lateral perfusion ports or openings are
provided in the polymeric sleeve 44, such as a right renal artery
perfusion port 98 and a left renal artery perfusion port 100 as
illustrated.
[0084] Perfusion ports in the polymeric sleeve 44 may be desirable
in embodiments of the endovascular prosthesis 96 in a variety of
clinical contexts. For example, although FIGS. 1 and 22 illustrate
a generally symmetrical aneurysm 40 positioned within a linear
infrarenal portion of the abdominal aorta, spaced axially apart
both from bilaterally symmetrical right and left renal arteries and
bilaterally symmetrical right and left common iliacs, both the
position and symmetry of the aneurysm 40 as well as the layout of
the abdominal aortic architecture may differ significantly from
patient to patient. As a consequence, the endovascular prosthesis
96 may need to extend across one or both of the renal arteries in
order to adequately anchor the endovascular prosthesis 96 and/or
span the aneurysm 40. The provision of one or more lateral
perfusion ports enables the endovascular prosthesis 96 to span the
renal arteries while permitting perfusion therethrough, thereby
preventing "stent jailing" of the renals. Lateral perfusion through
the endovascular prosthesis 96 may also be provided, if desired,
for a variety of other arteries including the second lumbar,
testicular, inferior mesenteric, middle sacral, and alike as will
be well understood to those of skill in the art.
[0085] The endovascular prosthesis 96 is preferably provided with
at least one, and preferably two or more radiopaque markers, to
facilitate proper positioning of the prosthesis 96 within the
artery. In an embodiment having perfusion ports 98 and 100 such as
in the illustrated design, the prosthesis 96 should be properly
aligned both axially and rotationally, thereby requiring the
ability to visualize both the axial and rotational position of the
device. Alternatively, provided that the delivery catheter design
exhibits sufficient torque transmission, the rotational orientation
of the graft maybe coordinated with an indexed marker on the
proximal end of the catheter, so that the catheter may be rotated
and determined by an external indicium of rotational orientation to
be appropriately aligned with the right and left renal
arteries.
[0086] In an alternative embodiment, the polymeric sleeve 44
extends across the aneurysm 40, but terminates in the infrarenal
zone. In this embodiment, a proximal zone 55 on the prosthesis 96
comprises a wire cage 46 but no polymeric sleeve 44. In this
embodiment, the prosthesis 96 still accomplishes the anchoring
function across the renal arteries, yet does not materially
interfere with renal perfusion. Thus, the polymeric sleeve 44 may
cover anywhere from about 50% to about 100% of the axial length of
the prosthesis 96 depending upon the desired length of uncovered
wire cage 46 such as for anchoring and/or lateral perfusion
purposes. In particular embodiments, the polymeric sleeve 44 may
cover within the range of from about 70% to about 80%, and, in one
four segment embodiment having a single exposed segment, 75%, of
the overall length of the prosthesis 96. The uncovered wire cage 46
may reside at only a single end of the prosthesis 96, such as for
traversing the renal arteries. Alternatively, exposed portions of
the wire cage 46 may be provided at both ends of the prosthesis
such as for anchoring purposes.
[0087] In a further alternative, a two part polymeric sleeve 44 is
provided. A first distal part spans the aneurysm 40, and has a
proximal end which terminates distally of the renal arteries. A
second, proximal part of the polymeric sleeve 44 is carried by the
proximal portion of the wire cage 46 which is positioned superiorly
of the renal arteries. This leaves an annular lateral flow path
through the side wall of the vascular prosthesis 96, which can be
axially aligned with the renal arteries, without regard to
rotational orientation.
[0088] The axial length of the gap between the proximal and distal
segments of polymeric sleeve 44 can be adjusted, depending upon the
anticipated cross sectional size of the ostium of the renal artery,
as well as the potential axial misalignment between the right and
left renal arteries. Although the right renal artery 32 and left
renal artery 34 are illustrated in FIG. 22 as being concentrically
disposed on opposite sides of the abdominal aorta, the take off
point for the right or left renal arteries from the abdominal aorta
may be spaced apart along the abdominal aorta as will be familiar
to those of skill in the art. In general, the diameter of the
ostium of the renal artery measured in the axial direction along
the abdominal aorta falls within the range of from about 7 cm to
about 20 cm for a typical adult patient.
[0089] Clinical and design challenges, which are satisfied by the
present invention, include providing a sufficient seal between the
upstream end of the vascular prosthesis and the arterial wall,
providing a sufficient length to span the abdominal aortic
aneurysm, providing sufficient wall strength or support across the
span of the aneurysm, and providing a sufficient expansion ratio,
such that a minimal percutaneous axis diameter may be utilized for
introduction of the vascular prosthesis in its collapsed
configuration.
[0090] Prior art procedures presently use a 7 mm introducer (18
French) which involves a surgical procedure for introduction of the
graft delivery device. In accordance with the present invention,
the introduction profile is significantly reduced. Embodiments of
the present invention can be constructed having a 16 French or 15
French or 14 French or smaller profile (e.g. 3-4 mm) thereby
enabling placement of the endoluminal vascular prosthesis of the
present invention by way of a percutaneous procedure. In addition,
the endoluminal vascular prosthesis of the present invention does
not require a post implantation balloon dilatation, can be
constructed to have minimal axial shrinkage upon radial expansion,
and avoids the disadvantages associated with nitinol grafts. While
a number of preferred embodiments of the invention and variations
thereof have been described in detail, other modifications and
methods of using and medical applications for the same will be
apparent to those of skill in the art. Accordingly, it should be
understood that various applications, modifications, and
substitutions may be made of equivalents without departing from the
spirit of the invention or the scope of the claims.
* * * * *