U.S. patent application number 12/818575 was filed with the patent office on 2011-04-14 for bifurcated highly conformable medical device branch access.
Invention is credited to JOHN R. DAUGHERTY, Logan R. Hagaman, Larry J. Kovach.
Application Number | 20110087318 12/818575 |
Document ID | / |
Family ID | 43855461 |
Filed Date | 2011-04-14 |
United States Patent
Application |
20110087318 |
Kind Code |
A1 |
DAUGHERTY; JOHN R. ; et
al. |
April 14, 2011 |
BIFURCATED HIGHLY CONFORMABLE MEDICAL DEVICE BRANCH ACCESS
Abstract
The present invention comprises a highly conformable stent graft
with an optional portal for a side branch device. Said stent graft
comprises a graft being supported by a stent, wherein said stent
comprises undulations each which comprise apices in opposing first
and second directions and a tape member attached to said stent and
to said graft such that the tape member edge is aligned to the edge
of the apices in the first direction of the each of the
undulations, thus confining the apices in the first direction of
the undulations to the graft and wherein the apices in the second
direction of the undulation are not confined relative to the graft;
wherein said graft forms unidirectional pleats where longitudinally
compressed and wherein said apices in the first direction of said
undulation is positioned under an adjacent pleat when compressed.
The invention also discloses and claims methods of making and using
said highly conformable stent graft and method of making the
optional portal.
Inventors: |
DAUGHERTY; JOHN R.;
(Flagstaff, AZ) ; Hagaman; Logan R.; (Flagstaff,
AZ) ; Kovach; Larry J.; (Flagstaff, AZ) |
Family ID: |
43855461 |
Appl. No.: |
12/818575 |
Filed: |
June 18, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61250313 |
Oct 9, 2009 |
|
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|
Current U.S.
Class: |
623/1.13 |
Current CPC
Class: |
A61F 2220/0025 20130101;
A61F 2002/067 20130101; A61F 2220/0033 20130101; A61F 2220/005
20130101; A61F 2/89 20130101; Y10T 156/1056 20150115; Y10T 29/49885
20150115; A61F 2002/061 20130101; A61F 2002/075 20130101; A61F
2/954 20130101; A61F 2/852 20130101; A61F 2240/001 20130101; A61F
2/07 20130101; A61F 2230/001 20130101; A61F 2/88 20130101; A61F
2/856 20130101 |
Class at
Publication: |
623/1.13 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Claims
1. A stent graft comprising: a graft being supported by a stent,
wherein said stent comprises undulations each which comprise apices
in opposing first and second directions; and a tape member,
comprising first and second longitudinal edges, attached to said
stent and to said graft such that the first tape edge substantially
covers the apices in the first or second direction of the each of
the undulations, thus confining the apices in the first or second
direction of the undulations to the graft and wherein the apices in
the first or second direction of the undulation are not confined
relative to the graft; wherein said graft forms circumferentially
oriented unidirectional pleats when longitudinally compressed and
said apices in the first or second direction of said undulation are
positioned under an adjacent pleat when compressed.
2. The stent graft of claim 1, wherein said apices in the first
direction are confined to the graft and the apices in the second
direction are not confined relative to the graft.
3. The stent graft of claim 1, wherein said apices in the second
direction are confined to the graft and the apices in the first
direction are not confined relative to the graft.
4. The stent graft of claim 1, wherein said stent is formed from a
single continuous wire helically wrapped around said graft.
5. The stent graft of claim 1, wherein said stent is a
self-expanding stent.
6. The stent graft of claim 1, wherein said stent is made from
Nitinol.
7. The stent graft of claim 1, wherein said stent is a balloon
expandable stent.
8. The stent graft of claim 1, wherein said undulations have a
sinusoidal shape.
9. The stent graft of claim 1, wherein said unidirectional pleats
are formed in-vivo after deployment.
10. The stent graft of claim 1, wherein said graft comprises
polytetrafluoroethylene.
11. The stent graft of claim 10, wherein said
polytetrafluoroethylene is expanded.
12. The stent graft of claim 1, wherein said tape member comprises
polytetrafluoroethylene.
13. The stent graft of claim 1, wherein said tape member further
comprises a thermoplastic adhesive.
14. The stent graft of claim 13, wherein said thermoplastic
adhesive is FEP.
15. The stent graft of claim 1, wherein said stent graft comprises
at least one sealing cuff.
16. The stent graft of claim 1, wherein said stent graft comprises
at least one radiopaque marker.
17. The stent graft of claim 1, wherein said stent graft can bend
to at least 90.degree. without kinking in-vivo when deployed.
18. The stent graft of claim 17, wherein said stent graft is placed
into a body lumen with blood flow direction going with the pleats
to minimize flow disruption and turbulence.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit to U.S. Provisional Patent
Application Ser. No. 61/250,313 filed Oct. 9, 2009, which is
incorporated by reference herein for all purposes
FIELD OF THE INVENTION
[0002] One aspect of the invention is directed to an improved,
modular, bifurcated stent graft having an integral support tube.
Another aspect of the invention is directed to a highly conformable
stent graft with an optional bifurcation.
BACKGROUND
[0003] Aneurysms occur in blood vessels at sites where, due to age,
disease or genetic predisposition of the patient, the strength or
resilience of the vessel wall is insufficient to prevent ballooning
or stretching of the wall as blood passes through. If the aneurysm
is left untreated, the blood vessel wall may expand and rupture,
often resulting in death.
[0004] To prevent rupturing of an aneurysm, a stent graft may be
introduced into a blood vessel percutaneously and deployed to span
the aneurysmal sac. Stent grafts include a graft fabric secured to
a cylindrical scaffolding or framework of one or more stents. The
stent(s) provide rigidity and structure to hold the graft open in a
tubular configuration as well as the outward radial force needed to
create a seal between the graft and a healthy portion of the vessel
wall and provide migration resistance. Blood flowing through the
vessel can be channeled through the luminal surface of the stent
graft to reduce, if not eliminate, the stress on the vessel wall at
the location of the aneurysmal sac. Stent grafts may reduce the
risk of rupture of the blood vessel wall at the aneurysmal site and
allow blood to flow through the vessel without interruption.
[0005] However, various endovascular repair procedures such as the
exclusion of an aneurysm require a stent graft to be implanted
adjacent to a vascular bifurcation. Often the aneurysm extends into
the bifurcation requiring the stent graft to be placed into the
bifurcation. A bifurcated stent graft is therefore required in
these cases. Modular stent grafts, having a separate main body and
branch component are often preferred in these procedures due to the
ease and accuracy of deployment. See U.S. Patent Application No.
2008/0114446 to Hartley et al. for an example of a modular stent
graft having separate main body and branch stent components. In the
Hartley et al. publication the main body stent has a fenestration
in the side wall that is tailored to engage and secure the side
branch stent. The side branch stent in such a configuration is in a
"line to line" interference fit with the main body fenestration,
causing a potential compromise to the fatigue resistance of the
stent to stent junction. U.S. Pat. No. 6,645,242 to Quinn presents
a more robust stent to stent joining configuration. In the Quinn
patent, a tubular support, internal to the main body stent, is
incorporated to enhance the reliability of the stent to stent
joining. The tubular, internal support of Quinn provides an
extended sealing length along with improved fatigue resistance.
However, the innermost tube is made by adding additional material
shaped into a tube and sewn and/or adhered to the main graft
component.
[0006] In addition, Aneurysms occurring in the aorta, the largest
artery in the human body, may occur in the chest (thoracic aortic
aneurysm) or in the abdomen (abdominal aortic aneurysm). Due to the
curvature of the aortic arch, thoracic aortic aneurysms can be
particularly challenging to treat. Other parts of the vasculature,
such as the common iliac artery which extends from the aorta, can
also be extremely tortuous. Hence, a stent graft deployed into such
regions is preferably able to conform to the vasculature. The high
degree of conformability allows the stent graft to bend and
optimally oppose and seal against the native vessel.
SUMMARY OF THE INVENTION
[0007] The one embodiment of the invention is directed to an
improved, modular, bifurcated stent graft having an integral
support tube. In another embodiment, the invention is directed to a
highly conformable stent graft with or without at least one portal
for a side branch device (e.g. a stent graft).
[0008] One embodiment of the invention comprises a multi-lumen
stent graft comprising: a primary lumen defined by a graft composed
of an innermost tube with an opening and an outermost tube with an
opening, said graft being supported by a primary stent; and a
secondary lumen disposed between the innermost tube and outermost
tube of said graft, wherein said secondary lumen is in fluid
communication through said openings. In one embodiment, said
secondary lumen comprises a secondary stent or stent assembly. In
another embodiment, said secondary lumen can accept another smaller
stent graft.
[0009] Another embodiment of the invention comprises a stent graft
for implantation in a bifurcated body lumen having a main branch
vessel and a side branch vessel, wherein the stent graft comprises:
a graft, said graft composed of an innermost tube with an opening
and an outermost tube with an opening, said graft extending along a
longitudinal axis from a distal end to a proximal end and defining
a main lumen extending therethrough, said graft being supported by
a primary stent; and a secondary lumen disposed between the
innermost tube and outermost tube of said graft, said secondary
lumen portion positioned between the distal and proximal ends of
said graft, wherein said secondary lumen is in fluid communication
through said openings of said innermost and outermost tubes. In one
embodiment, said primary stent is a self expanding stent.
[0010] Another embodiment of the invention comprises covering a
first mandrel that comprises a groove and a back wall of said
groove with an innermost polymeric tube; slitting said polymeric
tube along said back wall of said groove; placing a second mandrel
into said groove of the first mandrel and aligning said second
mandrel with the back wall of the groove, deforming said innermost
polymeric tube; placing an outermost polymeric tube over said inner
most tube; and making an opening over said second smaller mandrel;
wherein said outermost tube and innermost tube comprise a graft
member.
[0011] Another embodiment of the invention comprises a graft being
supported by a stent, wherein said stent comprise undulations each
which comprise apices in opposing first and second directions, and
a tape member, having first and second longitudinal edges, attached
to said stent and to said graft such that the first tape edge
substantially covers the apices in the first or the second
direction of the each of the undulations, thus confining the apices
in the first direction or second direction of the undulations to
the graft and wherein the apices in the first or the second
direction of the undulation are not confined relative to the graft.
In one embodiment, said apices in the first direction are confined
to the graft and the apices in second direction are not confined
relative to the graft. In another embodiment, said apices in the
second direction apices are confined to the graft and the apices in
the first direction are not confined relative to the graft. In
another embodiment, said graft forms circumferentially oriented
unidirectional pleats where longitudinally compressed. In another
embodiment, said apices in the first direction of said undulation
are positioned under an adjacent pleat where compressed. In another
embodiment, said stent is formed from a single continuous wire
helical wrapped around said graft. In another embodiment, said
stent is a self-expanding stent. In another embodiment, said stent
is made from Nitinol. In another embodiment, said undulations have
a sinusoidal shape. In another embodiment, said graft comprises
polytetrafluoroethylene.
[0012] Additional features and advantages of the invention will be
set forth in the description or may be learned by practice of the
invention. These features and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0013] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings are included to provide a further
understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0015] In the drawings:
[0016] FIG. 1A is a perspective view of a modular, bifurcated stent
graft having a main body stent, an internal support tube and
attached side branch stent. FIGS. 1B, 1C, 1D and 1E comprise a
bifurcated stent graft, in which the main body comprises at least
one side branch portal made from a portion of the main body
graft.
[0017] FIGS. 2A and 2B depict perspective views of a mandrel used
to construct a main body stent graft having an integral support
tube.
[0018] FIGS. 3A and 3B depict perspective views of a mandrel used
to construct a main body stent graft having an integral support
tube and a secondary stent assembly.
[0019] FIGS. 4A and 4B depict schematic side views of a mandrel
used to construct a main body stent graft having an integral
support tube and a secondary stent assembly.
[0020] FIGS. 5A, 5B, 5C and 5D are side views of a mandrel and
stent fabrication process.
[0021] FIG. 6 is a top view of a bifurcated stent graft with a side
branch portal.
[0022] FIG. 7 is a perspective view of a side branch stent having
three purpose built portions.
[0023] FIG. 8 depicts a fully extended stent graft.
[0024] FIG. 9 depicts a flexible stent graft in a state of full
longitudinal compression, wherein the unidirectional pleats are
formed around the full circumference of the stent graft.
[0025] FIGS. 10A and B depict a partial cross-sectional view of one
wall of the stent graft, taken along cross-sectional plane 3-3 of
FIG. 8, illustrating the unidirectional pleating of the compressed
stent graft.
[0026] FIG. 11 depicts a flexible stent graft a state of partial
longitudinal compression (or in a bent shape), wherein the
unidirectional pleats are formed on a portion of the stent graft
circumference (or on the inner meridian) and the outer meridian has
un-pleated or straight graft portions.
[0027] FIG. 12 depicts a "flat or unrolled" drawing of the
cylindrical mandrel.
[0028] FIG. 13 depicts a single circumference winding pattern.
[0029] FIG. 14 depicts a stent graft having an undulating, helical
wire stent surrounding a graft material. The stent is attached to
the graft material by a helical a tape member.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0030] One embodiment of the invention is directed to an improved,
modular, bifurcated stent graft having an integral support tube. In
another embodiment, the invention is directed to a highly
conformable stent graft with or without at least one portal for a
side branch device (e.g. a stent graft).
[0031] In general, most bifurcated stent grafts have an internal
tube to create the bifurcation or a fenestration on the side of a
stent graft in which another tube or stent graft is inserted. See,
for example U.S. Pat. No. 6,645,242 to Quinn and U.S. Pat. No.
6,077,296 to Shokoohi. FIG. 1 is a perspective view of a general
modular bifurcated stent graft 100 having a main body 102 with an
internal tube 104. In general, most internal tubes (i.e.
bifurcation tubes) are made by adding additional material that is
formed into a tube or a bifurcation site and sewn and/or adhered to
the internal side of the main body (usually the graft). The
internal tube 104 is sized to engage and secure a side branch
device 106, shown protruding from a main body portal 108. The main
body 102 is shown implanted into a main vessel 110 with the side
branch stent implanted into a branch vessel 112. The instant
invention, as depicted in FIGS. 1B to 7, comprises a bifurcated
stent graft, in which the main body comprises at least one side
branch portal made from a portion of the main body graft wherein
said at least a portion of said portal is integral with said graft
and which at least a portion of said portal has no seams in the
main blood flow surface of the graft and/or weakened areas due to
non-continuous construction.
[0032] One embodiment of the invention is shown in FIGS. 1B to 1D.
FIG. 1B is a top view of a bifurcated stent graft 120 having a
primary stent (or main body stent) 122 with a side branch portal
124. Also depicted is a stent feature 121 which creates an area for
the side branch portal. In this embodiment, said feature is called
the "double W". In this embodiment, said "double W" helps support
the side branch portal and prevents said portal from collapsing. In
addition, this design creates a region for a side branch portal
without creating a high strain region in the body winding pattern
of the stent. Without being bound to a particular theory, one
reason may be that the "double W" design does not rely on shorter
amplitude struts that stiffen the frame and results in higher
stains, which may cause fractures when the stent is stressed. The
main body portal 124 is sized to engage and secure a side branch
stent, one embodiment of which is depicted in FIG. 7, 700.
[0033] FIG. 1C is a side view with a partial longitudinal cross
section of FIG. 1B. This Figure depicts primary lumen 128, a
secondary lumen 130, an outermost tube 132, an innermost tube 134
and an optional secondary stent 126. Also depicted is the innermost
tube opening 131.
[0034] FIG. 1D is a cross section of A-A in FIG. 1C. This Figure
depicts primary stent 122, secondary stent 126, primary lumen 128,
and secondary lumen 130. This Figure also depicts an outermost tube
132 and an innermost tube 134.
[0035] FIG. 1E is a close up of section D depicted on FIG. 1D.
Thus, this Figure is a close up of the cross section of the side
branch portal. This Figure depicts the primary stent 122, secondary
stent 126, and secondary lumen 130. This Figure also depicts an
outermost tube 132 and an innermost tube 134. Graft 136 is composed
of innermost tube 134 and outermost tube 132. Also depicted is the
blood flow surface 138 (i.e. the internal graft surface), the outer
surface of the innermost tube 140 and the inner surface of the
outermost tube 141.
[0036] Thus, one embodiment of the invention, the bifurcated
(multi-lumen) stent graft, comprises a primary lumen 128 defined by
a graft 136 composed of an innermost tube 134 with an opening 131
and an outermost tube 132 with an opening 124, said graft being
supported by a primary stent 122; and a secondary lumen 130
disposed between the innermost tube 132 and outermost tube 134 of
said graft 136; wherein said secondary lumen is in fluid
communication through said openings 131 and 124. In one embodiment,
said secondary lumen 130 comprises a secondary stent 126 or stent
assembly. As used herein, said secondary stent assembly is a
secondary stent that is covered and may comprise additional
features such as radiopaque markers. In another embodiment, said
secondary lumen is disposed between the ends of the main stent
graft or main body. In another embodiment, a portion of the said
secondary stent or stent assembly abuts against a portion of the
innermost tube 134. In another embodiment, said secondary stent or
stent assembly abuts against a portion of graft 136. In another
embodiment, a portion of said secondary stent or stent assembly
lays on the outer surface of the innermost tube 140. In another
embodiment, said secondary lumen is defined partially by the
innermost tube and partially by the outermost tube. In another
embodiment, said secondary lumen is defined partially by the outer
surface of the innermost tube 140 and the inner surface of the
outermost tube 141.
[0037] The graft of the stent graft of the invention may be made up
of any material which is suitable for use as a graft in the chosen
body lumen. Said graft can be composed of the same or different
materials. Furthermore, said graft can comprise multiple layers of
material that can be the same material or different material.
Although the graft can have several layers of material, said graft
may have a layer that is formed into a tube (innermost tube) and an
outermost layer that is formed into a tube (outermost tube). For
the purposes on this invention, the outermost tube does not
comprise a tape layer that may be used to adhere a stent to a graft
as described in more detail below. In one embodiment of the
invention, said graft comprises an innermost tube and an outermost
tube.
[0038] Many graft materials are known, particularly known are those
that can be used as vascular graft materials. In one embodiment,
said materials can be used in combination and assembled together to
comprise a graft. The graft materials used in a stent graft can be
extruded, coated or formed from wrapped films, or a combination
thereof. Polymers, biodegradable and natural materials can be used
for specific applications.
[0039] Examples of synthetic polymers include, but are not limited
to, nylon, polyacrylamide, polycarbonate, polyformaldehyde,
polymethylmethacrylate, polytetrafluoroethylene,
polytrifluorochlorethylene, polyvinylchloride, polyurethane,
elastomeric organosilicon polymers, polyethylene, polypropylene,
polyurethane, polyglycolic acid, polyesters, polyamides, their
mixtures, blends and copolymers are suitable as a graft material.
In one embodiment, said graft is made from a class of polyesters
such as polyethylene terephthalate including DACRON.RTM. and
MYLAR.RTM. and polyaramids such as KEVLAR.RTM., polyfluorocarbons
such as polytetrafluoroethylene (PTFE) with and without
copolymerized hexafluoropropylene (TEFLON.RTM. or GORE-TEX.RTM.),
and porous or nonporous polyurethanes. In another embodiment, said
graft comprises expanded fluorocarbon polymers (especially PTFE)
materials described in British. Pat. Nos. 1,355,373; 1,506,432; or
1,506,432 or in U.S. Pat. Nos. 3,953,566; 4,187,390; or 5,276,276,
the entirety of which are incorporated by reference. Included in
the class of preferred fluoropolymers are polytetrafluoroethylene
(PTFE), fluorinated ethylene propylene (FEP), copolymers of
tetrafluoroethylene (TFE) and perfluoro (propyl vinyl ether) (PFA),
homopolymers of polychlorotrifluoroethylene (PCTFE), and its
copolymers with TFE, ethylene-chlorotrifluoroethylene (ECTFE),
copolymers of ethylene-tetrafluoroethylene (ETFE), polyvinylidene
fluoride (PVDF), and polyvinyfluoride (PVF). Especially preferred,
because of its widespread use in vascular prostheses, is ePTFE. In
another embodiment, said graft comprises a combination of said
materials listed above. In another embodiment, said graft is
substantially impermeable to bodily fluids. Said substantially
impermeable graft can be made from materials that are substantially
impermeable to bodily fluids or can be constructed from permeable
materials treated or manufactured to be substantially impermeable
to bodily fluids (e.g. by layering different types of materials
described above or known in the art). In another embodiment, said
outermost tube comprises ePTFE. In another embodiment, said
innermost tube comprises ePTFE. In another embodiment, said
innermost and outermost tube comprises ePTFE film that has been
wrapped into a tube. In another embodiment, said secondary stent is
covered with any of the material disclosed herein or known in the
art. In another embodiment, the secondary stent covering comprises
ePTFE.
[0040] Additional examples of graft materials include, but are not
limited to, vinylidinefluoride/hexafluoropropylene
hexafluoropropylene (HFP), tetrafluoroethylene (TFE),
vinylidenefluoride, 1-hydropentafluoropropylene, perfluoro (methyl
vinyl ether), chlorotrifluoroethylene (CTFE), pentafluoropropene,
trifluoroethylene, hexafluoroacetone, hexafluoroisobutylene,
fluorinated poly(ethylene-co-propylene (FPEP),
poly(hexafluoropropene) (PHFP), poly(chlorotrifluoroethylene)
(PCTFE), poly(vinylidene fluoride (PVDF), poly(vinylidene
fluoride-co-tetrafluoroethylene) (PVDF-TFE), poly(vinylidene
fluoride-co-hexafluoropropene) (PVDF-HFP),
poly(tetrafluoroethylene-co-hexafluoropropene) (PTFE-HFP),
poly(tetrafluoroethylene-co-vinyl alcohol) (PTFE-VAL),
poly(tetrafluoroethylene-co-vinyl acetate) (PTFE-VAC),
poly(tetrafluoroethylene-co-propene) (PTFEP)
poly(hexafluoropropene-co-vinyl alcohol) (PHFP-VAL),
poly(ethylene-co-tetrafluoroethylene) (PETFE),
poly(ethylene-co-hexafluoropropene) (PEHFP), poly(vinylidene
fluoride-co-chlorotrifluoroe-thylene) (PVDF-CTFE), and combinations
thereof, and additional polymers and copolymers described in U.S.
Publication 2004/0063805, incorporated by reference herein in its
entirety for all purposes. Additional polyfluorocopolymers include
tetrafluoroethylene (TFE)/perfluoroalkylvinylether (PAVE). PAVE can
be perfluoromethylvinylether (PMVE), perfluoroethylvinylether
(PEVE), or perfluoropropylvinylether (PPVE), as essentially
described in U.S. Publication 2006/0198866 and U.S. Pat. No.
7,049,380, both of which are incorporated by reference herein for
all purposes in their entireties. Other polymers and copolymers
include, polylactide, polycaprolacton-glycolide, polyorthoesters,
polyanhydrides; poly-aminoacids; polysaccharides; polyphosphazenes;
poly(ether-ester) copolymers, e.g., PEO-PLLA, or blends thereof,
polydimethyl-siolxane; poly(ethylene-vingylacetate); acrylate based
polymers or copolymers, e.g., poly(hydroxyethyl methylmethacrylate,
polyvinyl pyrrolidinone; fluorinated polymers such as
polytetrafluoroethylene; cellulose esters and any polymer and
copolymners described in U.S. Publication 2004/0063805,
incorporated by reference herein in its entity.
[0041] Said stents of the instant intention are generally
cylindrical and comprise helically arranged undulations having
plurality of helical turns. The undulations preferably are aligned
so that they are "in-phase" with each other as shown in FIG. 8.
More specifically, undulations comprise apices in opposing first
814 and second 816 directions. When the undulations are in-phase,
apices in adjacent helical turns are aligned so that apices can be
displaced into respective apices of a corresponding undulation in
an adjacent helical turn. In one embodiment, said undulations have
a sinusoidal shape. In another embodiment, said undulations are U
shaped. In another embodiment, said undulations are V shaped. In
another embodiment, said undulations are ovaloid shaped. These
shapes are fully described in U.S. Pat. No. 6,042,605, FIGS. 14A-E.
U.S. Pat. No. 6,042,605 is incorporated by reference herein in its
entirety for all purposes.
[0042] In another embodiment of the invention, said stent can be
fabricated from a variety of biocompatible materials including
commonly known materials (or combinations of materials) used in the
manufacture of implantable medical devices. Typical materials
include 316L stainless steel,
cobalt-chromium-nickel-molybdenum-iron alloy ("cobalt-chromium"),
other cobalt alloys such as L605, tantalum, Nitinol, or other
biocompatible metals. In one embodiment, said stent graft is a
balloon expandable stent graft. In another embodiment, said stent
graft is a self-expanding stent graft. In another embodiment, said
stent is a wire wound stent. In another embodiment, said wire wound
stent comprise undulations.
[0043] The wire wound stent can be constructed from a reasonably
high strength material, i.e., one which is resistant to plastic
deformation when stressed. In one embodiment, the stent member
comprises a wire which is helically wound around a mandrel having
pins arranged thereon so that the helical turns and undulations can
be formed simultaneously, as described below. Other constructions
also may be used. For example, an appropriate shape may be formed
from a flat stock and wound into a cylinder or a length of tubing
formed into an appropriate shape or laser cutting a sheet of
material. In another embodiment, said stent is made from a
super-elastic alloy. There are a variety of disclosures in which
super-elastic alloys such as nitinol are used in stents. See for
example, U.S. Pat. No. 4,503,569, to Dotter; U.S. Pat. No.
4,512,338, to Balko et al.; U.S. Pat. No. 4,990,155, to Wilkoff;
U.S. Pat. No. 5,037,427, to Harada, et al.; U.S. Pat. No.
5,147,370, to MacNamara et al.; U.S. Pat. No. 5,211,658, to Clouse;
and U.S. Pat. No. 5,221,261, to Termin et al.
[0044] A variety of materials variously metallic, super elastic
alloys, such as Nitinol, are suitable for use in these stents.
Primary requirements of the materials are that they be suitably
springy even when fashioned into very thin sheets or small diameter
wires. Various stainless steels which have been physically,
chemically, and otherwise treated to produce high springiness are
suitable as are other metal alloys such as cobalt chrome alloys
(e.g., ELGILOY.RTM.), platinum/tungsten alloys, and especially the
nickel-titanium alloys generically known as "nitinol".
[0045] Nitinol is especially preferred because of its
"super-elastic" or "pseudo-elastic" shape recovery properties,
i.e., the ability to withstand a significant amount of bending and
flexing and yet return to its original form without permanent
deformation. These metals are characterized by their ability to be
transformed from an austenitic crystal structure to a
stress-induced martensitic structure at certain temperatures, and
to return elastically to the austenitic shape when the stress is
released. These alternating crystalline structures provide the
alloy with its super-elastic properties. These alloys are well
known but are described in U.S. Pat. Nos. 3,174,851; 3,351,463; and
3,753,700.
[0046] Other suitable stent materials include certain polymeric
materials, particularly engineering plastics such as thermotropic
liquid crystal polymers ("LCP's"). These polymers are high
molecular weight materials which can exist in a so-called "liquid
crystalline state" where the material has some of the properties of
a liquid (in that it can flow) but retains the long range molecular
order of a crystal. The term "thermotropic" refers to the class of
LCP's which are formed by temperature adjustment. LCP's may be
prepared from monomers such as p,p'-dihydroxy-polynuclear-aromatics
or dicarboxy-polynuclear-aromatics. The LCP's are easily formed and
retain the necessary interpolymer attraction at room temperature to
act as high strength plastic artifacts as are needed as a foldable
stent. They are particularly suitable when augmented or filled with
fibers such as those of the metals or alloys discussed below. It is
to be noted that the fibers need not be linear but may have some
preforming such as corrugations which add to the physical torsion
enhancing abilities of the composite.
[0047] Another embodiment of the invention comprises a stent graft
for implantation in a bifurcated body lumen having a main branch
vessel and a side branch vessel, wherein the stent graft comprises:
a graft, said graft composed of an innermost tube with an opening
and an outermost tube with an opening, said graft extending along a
longitudinal axis from a distal end to a proximal end and defining
a main lumen extending therethrough, said graft being supported by
a primary stent; and a secondary lumen disposed between the
innermost tube and outermost tube of said graft, said secondary
lumen portion positioned between the distal and proximal ends of
said graft, said secondary lumen is in fluid communication through
said openings of said innermost and outermost tubes. In one
embodiment, said primary stent is a self expanding stent. In
another embodiment, said self expanding stent comprises a
titanium-nickel alloy. In another embodiment, said stent comprises
a single continuous wire helically wrapped around said graft. In
another embodiment, wherein said single continuous wire comprises
undulations. In another embodiment, said undulating wire comprises
multiple turns of said undulations, and each turn of said
undulating wire comprises multiple apexes, with undulation in one
turn generally in-phase with undulation in an adjacent turn. In
another embodiment, said undulations are U shaped. In another
embodiment, said undulations are V shaped. In another embodiment,
said undulations are ovaloid shaped. In another embodiment, said
undulations are sinusoidal shaped. In another embodiment, said
stent is attached to said graft. In another embodiment, said stent
is attached to said graft by a ribbon or tape. In another
embodiment, said ribbon or tape is adhered to a portion of said
stent and a portion of said graft. In another embodiment, said
ribbon or tape is arranged in a helical configuration with multiple
turns. In another embodiment, said ribbon or tape is arranged in a
helical configuration with multiple turns, each turn being spaced
from an adjacent turn. In another embodiment, said spacing between
said turns is uniform. In another embodiment, said ribbon covers a
portion of said undulation. In another embodiment, said stent
comprises undulations each which comprise an apex portion and a
base portion and said ribbon or tape is attached to said stent such
that the ribbon is placed along to the base portion of the each of
the undulations thus confining the base portion of the undulations
to the graft and wherein the apex portion of the undulation is not
confined.
[0048] At least one method of making a main body stent graft having
an integral support tube is described in FIG. 2 through FIG. 7.
[0049] FIG. 2A is a perspective view of a metallic mandrel 200
having a slot or groove 202 formed into one end of the mandrel. The
groove 202 terminates into a back wall 204. As shown in perspective
view FIG. 2B, an inner tube 206 is slip-fit over the mandrel 200,
covering a portion of the mandrel groove 202. An inner tube can
comprise any biocompatible polymer that is deformable (to allow a
subsequent insertion of a side branch stent) and can be extruded,
coated or formed from wrapped films. Suitable materials used for
the inner tube may include, but are not limited to, any of the
material described above, any other biocompatible material commonly
known in the art or a combination thereof.
[0050] FIG. 3A is a perspective view of the mandrel 200 covered by
the inner tube 206. The inner tube is cut, forming a slit 300 at
the back wall 204 of the mandrel groove 202. As shown in FIG. 3B, a
side branch or secondary stent assembly 302 is aligned to the
mandrel groove 202, mandrel back wall 204 and inner tube slit 300.
A first support segment (subsequently described) is placed into the
secondary stent assembly and the secondary stent assembly 302 (with
the first support segment) is then inserted into the mandrel groove
202, deforming the inner tube 206 into the mandrel groove. The back
wall 204 defines the opening in the innermost tube (131, FIG.
1E)
[0051] To control the deformed shape of the inner tube, support
segments are placed into the secondary stent assembly and into the
mandrel groove, as depicted in FIGS. 4A and 4B. Shown in FIG. 4A is
a side view schematic of the mandrel 200, the groove 202 and the
groove back wall 204. Shown in FIG. 4B is a side view schematic of
the mandrel 200, mandrel groove 202 and inner tube 206. The
secondary stent assembly 302 has been placed over a first support
segment 400 having an end formed to mate to the mandrel groove back
wall 204. The opposing end of the first support segment has a
tapered or angulated wall as depicted in FIG. 4B. A second support
segment 402 is placed into the mandrel groove 202 under the inner
tube 206. The second support structure can have an angulated wall
that mates with the angulated wall of the first support structure,
although it is not required for the second support structure to
have an angulated wall. One of the purposes of this second support
structure to keep first support segment 400 in place during
manufacturing. The inner tube 206 is shown deformed into the
mandrel groove 202. The inner tube 206 is also shown having a
tapered, beveled or angulated wall portion 404 formed by the
angulated wall of the support segment 400.
[0052] To further strengthen the inner tube (FIG. 3A, 206),
additional sheet or film layers may be added onto the inner tube
prior to the insertion of the secondary stent assembly. For example
a square/rectangle shaped thin film sheet having a high degree of
bi-axial strength may be placed onto the inner tube 206 and aligned
to the mandrel groove. The sheet can be dimensioned to be wider
than the mandrel groove width and have a length approximating the
mandrel groove length. This strengthening layer will then be
deformed into the mandrel groove, providing additional support to
the inner tube/secondary stent assembly. Multiple strengthening
layers may be combined to enhance the properties of the inner tube.
Suitable materials used for strengthening layers may include, but
are not limited to, any of the material described above, any other
biocompatible material commonly known in the art or a combination
thereof.
[0053] Although the above methods describe the making of a
bifurcated stent graft with only one portal, additional portals can
also be made using similar methods describe above. Thus, another
embodiment of the invention comprises a stent graft with at least
two portals. In another embodiment, said stent graft of the
invention comprises three, four, five, six or seven portals. Such a
stent graft may be useful for, inter alia, implanting a stent graft
in the abdominal aorta where the renal arteries branch off. In
addition, due to the stent graft of the invention being highly
conformable, see below, said stent graft of the invention with
three portals can be placed in the arch of the aorta without
blocking blood flow to the left subclavian artery, left common
carotid artery and the bachiocephalic artery. In another
embodiment, said several portals can be placed where desired
longitudinally along the stent and/or circumferentially around the
stent. A person of skill in the art can design said portals at any
region in the vasculature.
[0054] At least one method of making a secondary stent assembly is
outlined in FIGS. 5A through 5D. As shown in side view FIGS. 5A and
5B, a polymeric tube 502 is slip-fit onto a mandrel 500. An
undulating wire can be formed into a ring stent 506 by winding the
wire onto a mandrel with protruding pins. The diameters of the
mandrel and pins along with the locations of the pins dictate the
final configuration of the ring stent. After the wire is wound onto
the mandrel, the mandrel and wire are heat treated and quenched to
set the shape of the stent. The wire is then removed from the
mandrel. The ends of the wire are joined together with a section of
polymeric heat shrink tubing, forming ring stent 506. Other methods
can be used to make the secondary stent (e.g. laser cutting). One
or more of these ring stents 506 are then placed onto the polymeric
tube 502. Optional radiopaque marker bands 504 are then placed onto
the polymeric tube 502. The wire or metal tube used to make the
secondary stent is described above. In one embodiment, said
secondary stent comprises Nitinol.
[0055] Next, as shown in FIG. 5C, one end of the polymeric tube 502
is inverted and drawn over the wire ring stents 506 and optional
radiopaque marker bands 504. The mandrel, polymeric tube, ring
stents and radiopaque bands are then heat treated to bond the
components together into a stent assembly. The assembly is removed
from the mandrel and trimmed to length, forming a secondary stent
assembly 302 as shown in FIG. 5D. The secondary stent assembly is
then placed onto a first support segment 400. Radiopaque markers
include, but are not limited to gold, platinum, platinum-tungsten,
palladium, platinum-iridium, rhodium, tantalum, or alloys or
composites of these metals.
[0056] As previously described in FIG. 4B, the secondary stent (or
secondary stent assembly) and the first support assembly are then
inserted into the mandrel groove 202, deforming the inner tube 206
into the mandrel groove. The assembly shown in FIG. 4B is then
covered with an outer polymeric tube. As described herein, said
tube can be can be extruded, coated or formed from wrapped
films.
[0057] The assembly is heat treated to join the inner tube to the
outer tube. A side branch portal or opening (FIG. 1, item 108) is
formed as described above. A primary wire stent is then formed by
winding a wire onto a mandrel with protruding pins. The wire is
heat treated to set the shape of the wire with a process similar to
that used to form the secondary stent (FIG. 5B). The primary stent
is then placed over the outer polymeric tube and overwrapped with a
polymeric film. The assembly is then heat treated to bond the
components together.
[0058] Methods of attaching a stent to a graft are known in the
art. One embodiment comprises a coupling member that is generally a
flat ribbon or tape having at least one generally flat surface. In
another embodiment of the invention, the tape member is made from
expanded PTFE (ePTFE) coated with an adhesive. In another
embodiment, said adhesive is a thermoplastic adhesive. In another
embodiment, said thermoplastic adhesive is fluorinated ethylene
propylene (FEP). In this embodiment, the FEP-coated side faces
toward and contacts the exterior surface of the stent and graft,
thus attaching the stent to the graft. Although a particular tape
member configuration and pattern has been illustrated and
described, other configuration and/or patterns may be used without
departing from the scope of the present invention. Materials and
method of attaching a stent to the graft is discussed in U.S. Pat.
No. 6,042,602 to Martin, incorporated by reference herein for all
purposes.
[0059] FIG. 6 depicts a top view of a bifurcated stent graft 120
with a side branch portal 124. In this embodiment, the stent graft
comprises a helically formed undulating wire primary stent 122. The
primary stent 122 is joined to graft 136 by a film wrapping 606, as
described above. The stent has film wrapped sealing cuffs 608 on
the two opposing ends of the stent graft assembly 120. Such methods
of assembly are generally disclosed in, for example, U.S. Pat. No.
6,042,605 issued to Martin, et al., U.S. Pat. No. 6,361,637 issued
to Martin, et al. and U.S. Pat. No. 6,520,986 issued to Martin, et
al. incorporated by reference herein for all purposes.
[0060] A side branch stent graft would ideally have a distal
portion having a high degree of radial stiffness to allow
apposition and sealing against a vessel wall. The side branch stent
would also have a mid-portion that is highly flexible and highly
fatigue resistant to the pulsatile and cyclic loading imparted by
the native vessels. The side branch stent would also have a
proximal portion that is deployed into the main body stent. This
proximal portion of the side branch stent requires a high degree of
radial stiffness in order to dock and seal properly into the main
body portal.
[0061] Shown in FIG. 7 is one embodiment of a side branch stent
graft 700, comprising a wire wound metallic stent 702, a graft
covering 704 and radiopaque marker bands 706. The side branch stent
has a distal portion 708, a mid-portion 710 and a proximal portion
712. The distal portion 708 has a high degree of radial stiffness
to allow apposition and sealing against a branch vessel wall (FIG.
1, 112). The mid-portion 710 is highly flexible and highly fatigue
resistant to the pulsatile and cyclic loading imparted by the
native vessels. The proximal portion 712 that is deployed into the
main body stent (FIG. 1, 102), has a high degree of radial
stiffness in order to dock and seal properly into the main body
portal and can resist compression and remain patent if an
additional device deployment is used (e.g. an extender).
[0062] The process used to manufacture a side branch stent graft
700, can be used to fabricate the stent graft assembly (FIG. 6,
120) as defined above. Such methods of assembly are generally
disclosed in, for example, U.S. Pat. No. 6,042,605 issued to
Martin, et al., U.S. Pat. No. 6,361,637 issued to Martin, et al.
and U.S. Pat. No. 6,520,986 issued to Martin, et al. The stiffness,
radial strength, flexibility and fatigue life of a side branch
stent can be controlled by the stent wire properties, wound pattern
geometries of the wire, graft properties and wire to graft
attachment configurations. For example in FIG. 7, the distal
portion 708 of the side branch stent 700 has an undulating wire
pattern with relatively large undulation amplitude. The undulations
are also spaced relatively far apart. In comparison, the
mid-portion 710 of the side branch stent has an undulating wire
pattern with relatively small undulation amplitude. The undulations
are also spaced relatively far apart. Finally, the proximal portion
712 that is deployed into the main body stent (FIG. 1, 102), has an
undulating wire pattern with relatively large undulation amplitude.
The undulations are also spaced relatively close to the adjacent
wires.
[0063] Methods of joining the side branch stent graft to the
main-stent graft are known. These include, but are not limited to
friction fits, hooks, and barbs and/or raised stent apices.
Additional methods are disclosed in U.S. Publication 2009/0043376
to Hamer and Zukowski, incorporated by reference herein in its
entirety for all purposes.
[0064] The stent graft may be delivered percutaneously, typically
through the vasculature, after having been folded to a reduced
diameter. Once reaching the intended delivery site it is expanded
to form a lining on the vessel wall. In one embodiment the stent
graft is folded along its longitudinal axis and restrained from
springing open. The stent graft is then deployed by removing the
restraining mechanism, thus allowing the graft to open against the
vessel wall. The stent grafts of this invention are generally
self-opening once deployed. If desired, an inflatable balloon
catheter or similar means to ensure full opening of the stent graft
may be used under certain circumstances. In another embodiment,
said stent graft is a balloon expandable stent. The side branch can
also be delivered percutaneously after having been folded to a
reduced diameter.
[0065] The stent graft of the invention may comprise at least one
or two radiopaque markers, to facilitate proper positioning of the
stent graft within the vasculature. Said radiopaque markers can be
used to properly align the stent graft both axially and
rotationally to confirm that the side portal is properly aligned.
Said radio markers include, but are not limited to gold, platinum,
platinum-tungsten, palladium, platinum-iridium, rhodium, tantalum,
or alloys. 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 to appropriately align the side branch(es). Additional
methods of delivering the bifurcated stent graft of the invention
and an associated side branch are disclosed in U.S. Publication
2008/0269866 to Hamer and Johnson and U.S. Publication 2008/0269867
to Johnson, both of which are incorporated by reference herein in
their entirety for all purposes.
[0066] Another embodiment of the invention comprises a highly
conformable stent graft that can conform to highly tortuous
sections of a native vessel. Said stent graft may optionally
encompass at least one side branch portal.
[0067] Referring to FIG. 8, the highly conformable stent graft of
the invention 800 generally includes a graft 804, a stent 802 and a
tape member (1406, FIG. 14) for coupling the stent and graft member
together and is highly conformable. Preferably, the stent and graft
are coupled together so that they are generally coaxial.
[0068] In one embodiment of the invention, the highly conformable
stent graft 800 has a helically formed wire stent 802 surrounding a
graft 804. The wire form stent has opposing first 814 and second
816 direction apices. The stent graft 800 has a first end portion
806 optionally comprising a sealing cuff 808. Similarly, the stent
graft 800 has a second end portion 810 optionally comprising a
second sealing cuff 812 (folded back for illustration purposes) and
a radiopaque marker 818. As depicted in FIG. 9, the flexible stent
graft 800 has unidirectional pleats 900 that are formed upon
longitudinal compression. In one embodiment, said stent graft of
the invention has at least one portal between the ends of said
stent graft of the invention for the introduction of a side branch
device. In another embodiment, said side branch device is a stent
graft.
[0069] FIG. 9 shows a flexible stent graft 800 in a state of
longitudinal compression, wherein the unidirectional pleats 900 are
formed around the full circumference of the stent graft 800.
[0070] FIG. 10A is a partial longitudinal cross-sectional view of
one wall of the stent graft 800, taken along cross-sectional plane
3-3 of FIG. 9, illustrating the unidirectional pleating of the
compressed stent graft 800. The unidirectional pleats have a common
orientation and are all bent in the same direction. The wire stent
802 is shown with opposing first directional apices 814 tucked
under an adjacent folded portion of the graft material 804, forming
a unidirectional pleat 900. The arrow 1000 indicates a preferred
blood flow direction as "going with the pleats" to minimize flow
disruption and turbulence. FIG. 10B is a long cross-sectional view
similar to that of FIG. 10A, showing unidirectional pleats 900,
along with a preferred blood flow direction 1000.
[0071] FIG. 11 shows a flexible stent graft 800 in a bent shape
that imparts compression to the wall of the graft along the inner
meridian of the bend (i.e. partial longitudinal compression)
wherein the unidirectional pleats 900 are formed on a portion of
the stent graft circumference (or the inner meridian). The outer
meridian has un-pleated or straight graft portions 1100. The arrow
1102 indicates a preferred blood flow direction as previously shown
in FIG. 10.
[0072] One embodiment of the invention comprises a graft being
supported by a stent, wherein said stent comprises undulations each
which comprise apices in opposing first and second directions, and
a tape member, having first and second longitudinal edges, attached
to said stent and to said graft such that the first tape edge
substantially covers the apices in the first or the second
direction of the each of the undulations, thus confining the apices
in the first or the second direction of the undulations to the
graft and wherein the apices in the first or the second direction
of the undulation are not confined relative to the graft. In one
embodiment, said apices in the first direction apices are confined
to the graft and the second direction apices are not confined
relative to the graft. In another embodiment, said apices in the
second direction apices are confined to the graft and the first
direction apices are not confined relative to the graft. In another
embodiment, said graft forms circumferentially oriented
unidirectional pleats where longitudinally compressed. In another
embodiment, said confined apices (either in the first direction or
second direction) of said undulation are positioned under an
adjacent pleat when compressed. The term "confined apices" means
that the apices are attached to the graft by either a tape member
or attached by another method known in the art. In another
embodiment, said confined apices are positioned under an adjacent
pleat thereby covering about 1%, about 2%, about 3%, about 4%,
about 5%, about 10%, about 20%, about 30%, about 40%, about 50%
about 60%, about 70%, about 80% of undulation height 1312 (FIG. 13)
of the apices in the first direction. Depending on the method of
taping the stent to the graft, stent design, graft construction
and/or any other consideration due to the construction of the stent
graft, not all apices may be positioned under an adjacent pleat or
may differ in the undulation height 1312 that can be positioned
behind an adjacent pleat. Thus, there may be sections of the stent
graft that may not be compressible in accordance with the instant
invention. Thus, in another embodiment, only a section of the stent
graft may be compressed by positioning confined apices under an
adjacent pleat. In another embodiment, only a portion of the stent
graft may be folded by positioning confined apices under an
adjacent pleat (in the inner meridian), as depicted in FIG. 11.
Although the disclosed embodiment comprises the apices in the first
direction positioned behind pleats, the invention also encompasses
apices in the second direction that are attached to the graft and
are positioned under an adjacent pleat, while the apices in the
first direction are not confined.
[0073] An important aspect of the invention is that the tape
member, which comprises a first and second longitudinal edge,
secures the stent member to the graft member and covers only a
portion of the stent member. Specifically, said tape member is
attached to said stent and to said graft such that the first edge
of said tape member substantially covers of the apices in the first
direction of the each of the undulations, thus confining the apices
in the first direction of the undulations to the graft. In one
embodiment, the first edge of said tape member is aligned to the
edge of the apices in the first direction 814 of the each of the
undulations, as essentially depicted in FIG. 14. With this
construction when the stent graft is compressed, the graft forms
circumferentially unidirectional pleats and allows said apices in
the first direction 814 to be positioned under an adjacent pleat,
as shown in FIGS. 9 and 11. The formation of said unidirectional
pleats makes said stent graft more conformable, thus giving the
stent graft the ability to bend, as depicted in FIG. 11. In one
embodiment, said stent graft can bend to at least 90.degree.
without kinking (i.e. maintains an essentially circular
cross-section in the luminal surface). In another embodiment, said
stent graft can bend to at least 90.degree. without kinking after
in-vivo deployment.
[0074] The tape member has a generally broad and/or flat surface
for interfacing with the stent and graft. This increases potential
bonding surface area between the tape member and the graft member
to enhance the structural integrity of the stent graft. The
increased bonding surface area also facilitates minimizing the
thickness of the tape member. In addition, the tape member is
arranged in a helical configuration according to the embodiment
illustrated in FIG. 14 (helically arranged tape member 1406). As
shown, the tape member may be constructed with a constant width and
arranged with uniform spacing between turns. Tape member 1406 not
only covers the apices in the first direction of each of the
undulations, but also covers a portion of each undulation. In
another embodiment, there can be several tape members on a stent
graft, which serves the same function as described above. A
non-limiting reason to have several tape members on a stent graft
is if there is a disruption in the stent pattern, such as changing
the stent pattern to make room for a portal for a side-branch
device, as depicted in FIG. 12, 1206, FIG. 14, 1408, and FIG. 1B,
121. In another embodiment, said tape member does not overlap an
adjacent row of undulating stent members when the stent graft is
not compressed. Although the Examples and Figures show an
embodiment wherein apices in the first direction of the each of the
undulations are attached to the stent graft by the tape member,
said apices in the second direction may also be attached to the
stent graft while the apices in the first direction are not
attached.
[0075] It has been found that the width of the tape member can
affect the flexibility of the stent graft. The wider the tape
member, the less flexible the stent graft will become. Thus, in one
embodiment said tape member covers about 10%, about 20% about 30%,
about 40%, about 50%, about 60%, about 70%, about 80% of undulation
height 1312 (FIG. 13). In another embodiment, the full width of
said tape member is adhered to said stent and graft. In another
embodiment, said tape member does not extend to or touch an
adjacent row of the undulating stent members, e.g. when not
compressed or partially compressed. In another embodiment, the
width of said unidirectional pleats is the same as the width of the
tape member. Although the tape member can cover a portion of each
undulation, including confining the apices in the first direction
to the graft, as discussed above, apices in the second direction of
the undulation are not confined relative to the graft (e.g. 816 in
FIG. 8). This construction allows for the formation of pleats where
the stent graft is compressed. Pleats can be fully circumferential
when the stent graft is compress longitudinally, as depicted in
FIG. 9, or in the inner meridian of a bend, as depicted in FIG. 11.
In another embodiment, said unidirectional circumferential pleats
are formed when initially compressed. In other words, no further
manipulation of the stent graft is required to create said
unidirectional circumferential pleats. In another embodiment, said
unidirectional circumferential pleat are formed in-vivo when
deployed. In another embodiment said pleats will be formed in the
inner meridian in-vivo when said stent graft is deployed. Said
stent graft of the invention can conform, as describe above, to the
aortic arch or other tortuous, curved or bent body lumen. In
another embodiment, tape member (or separate pieces thereof) also
surrounds the terminal end portions of the stent graft to secure
the terminal portions of the graft member to the support structure
formed by stent member.
[0076] In another embodiment of the invention, the tape member is
made from expanded PTFE (ePTFE) coated with an adhesive. In another
embodiment, said adhesive is a thermoplastic adhesive. In another
embodiment, said thermoplastic adhesive is fluorinated ethylene
propylene (FEP). In this embodiment, the FEP-coated side faces
toward and contacts the exterior surface of the stent and graft,
thus attaching the stent to the graft. Although a particular tape
member configuration and pattern has been illustrated and
described, other configuration and/or patterns may be used without
departing from the scope of the present invention.
[0077] In another embodiment of the invention, said stent graft of
the invention comprises one or more radiopaque metallic fibers,
such as gold, platinum, platinum-tungsten, palladium,
platinum-iridium, rhodium, tantalum, or alloys or composites of
these metals that may be incorporated into the device,
particularly, into the graft, to allow fluoroscopic visualization
of the device.
[0078] In another embodiment of the invention, said stent graft of
the invention comprises optional sealing cuffs 808 and 812 as shown
in FIG. 8. Said sealing cuff comprises a cuff which has a first
cuff end secured to outer surface of the stent graft 800 and a
second cuff end at least a portion of which is unsecured to form a
flange. In this configuration, the flange forms a one-way valve
that circumferentially surrounds the stent graft 800 and occludes
flow around the stent graft. In one embodiment, said sealing cuff
is positioned around the first end portion 806 of the stent graft
800. In another embodiment, said sealing cuff is positioned around
the second end portion 810 of the stent graft 800. In another
embodiment, said sealing cuff is positioned around the first end
portion 806 and the second end portion 810 of the stent graft 800.
In another embodiment, sealing cuffs (808, 812) comprise a
hydrophilic material, preferably a hydrophilic polymer or gel-foam,
which expands when exposed to water, such as in blood or other
water-containing body fluids. In another embodiment, said sealing
cuffs 808 and 812 can comprise the materials described above. A
description of sealing cuffs is found in U.S. Pat. No. 6,015,431,
incorporated by reference herein in its entirety for all
purposes.
[0079] This invention is further illustrated by the following
Examples which should not be construed as limiting. The contents of
all Figures and references are incorporated herein by
reference.
[0080] While particular embodiments of the present invention have
been illustrated and described herein, the present invention should
not be limited to such illustrations and descriptions. It should be
apparent that changes and modifications may be incorporated and
embodied as part of the present invention within the scope of the
following claims.
EXAMPLE 1
Construction of a Highly Conformable Stent Graft
[0081] A flexible stent graft was assembled having the general
configuration as shown in FIG. 8.
[0082] The stent graft was fabricated by initially extruding and
expanding a tube of polytetrafluoroethylene (PTFE) to form a base
tube. The base tube had a length of about 60 mm, a wall thickness
of about 0.06 mm and a diameter of about 26 mm. The base tube had a
substantial fibril orientation in the longitudinal direction so
that the tube was relatively strong in the longitudinal direction
while being relatively weak in the radial direction. The base tube
was radially stretched over a mandrel having a diameter of about 31
mm.
[0083] To provide resistance to fluid permeation and to enhance the
radial strength of the base tube, a film of densified ePTFE was
wrapped over the base tube. The film was a thin, strong
fluoropolymer; a particularly preferred material for this
application is a non-porous ePTFE provided with an adhesive coating
of thermoplastic fluorinated ethylene propylene (FEP), referred to
hereinafter as "substantially impermeable ePTFE/FEP insulating
tape". The FEP was oriented down against the base tube. EPTFE is
well known in the medical device arts; it is generally made as
described by U.S. Pat. Nos. 3,953,566 and 4,187,390 to Gore. The
particular tape described herein is slit from a substantially
non-porous ePTFE/FEP film having a thickness of about 0.0064 mm, an
isopropyl bubble point of greater than about 0.6 MPa, a Gurley No.
(permeability) of greater than 60 (minute/1 square inch/100 cc);
(or 60 (minute/6.45 square cm/100 cc)), a density of 2.15 g/cc and
a tensile strength of about 309 MPa in the length direction (i.e.,
the strongest direction). The film had a width of about 19 mm
(0.75'') with four passes helically wrapped with a pitch angle of
about 86.degree..
[0084] To further enhance the radial strength of the base tube and
to provide an open structure bonding layer, an additional layer of
film was applied. The ePTFE film had high degree strength in the
longitudinal direction and had a very open microstructure. The open
microstructure enhanced the subsequent FEP/ePTFE bonding of a stent
frame to the graft. The film had a thickness of about 2.5 microns
(0.0001'') and a width of about 25.4 mm (1.0''). Eight helically
wrapped layers were applied with a pitch angle of about
83.degree..
[0085] The mandrel and wrapped films were then heat treated in an
air convection oven to bond the films together.
[0086] A stent frame was then formed by winding a Nitinol wire onto
a mandrel having protruding pins. A "flat or unrolled" drawing of
the cylindrical mandrel is shown in FIG. 12. Shown is an overall
winding pattern 1200, detailing a first end portion 1202 and a
second end portion 1204. Also shown is an optional "side branch
portal" configuration 1206 that can be incorporated into the
overall pattern if a branch portal is desired. The generic single
circumference winding pattern shown as 1206 can replace the
optional side branch pattern 1206 if desired.
[0087] Shown in FIG. 13 is a single circumference winding pattern
shown as 1206. The pattern includes a linear pitch 1300, a pin
diameter 1302, a wire diameter 1304, a wire apex angle 1306, a
circumference 1308 and an apex to base half frequency 1310. The
pattern shown was repeated along the stent length with the
exception of the first and second end portions previously shown in
FIG. 12 (1202, 1204). The optional side branch portal configuration
(FIG. 12, 1206) was not incorporated.
[0088] The stent frame was formed according to the following
dimensions as defined in FIG. 13: the linear pitch 1300 was about
9.7 mm (0.383''), the pin diameter 1302 was about 1.6 mm (0.063''),
the wire diameter 1304 was about 0.5 mm (0.0195''), the wire apex
angle 1306 was about 50.4 degrees, the circumference 1308 was about
97.3 mm (3.83'') and the apex to base half frequency 1310 was about
5.3 mm (0.21'').
[0089] The mandrel with the wound wire was then heat treated in an
air convection oven as is commonly known in the art (e.g. see U.S.
Pat. No. 6,352,561 to Leopold), and then quenched in room
temperature water.
[0090] The wire stent was the removed from the winding mandrel. The
wire ends (shown in FIGS. 12, 1202 and 1204) were trimmed and tied
together with high temperature fibers as shown in FIGS. 14, 1402
and 1404. The amplitude of the nested pair is longer than the
adjacent apexes so that when the wires are nested the nested wires
to not create an adversely high strained region (see FIGS. 14, 1410
and 1412). The stent was partially joined to the wrapped tube by
melting the underlying FEP adjacent to portions of the stent wire
using a soldering iron. A final layer of an ePTFE tape, laminated
with FEP, was wrapped over the wire stent according to the pattern
depicted in FIG. 14 and placed in an oven to bond the film to the
underlying graft, thus securing the stent to the graft.
[0091] Shown in FIG. 14 is a stent graft 1400 having an undulating,
helical wire stent 802 surrounding a graft material 804. The stent
is attached to the graft material by a helically applied tape
member 1406. As shown, the first edge of the helically applied tape
member 1406 covers the opposing first apices 814 of the wire stent.
An optional wrapping pattern section 1408 can be incorporated if a
side branch portal is desired. The tape 1406 was an ePTFE/FEP
laminate having a width of about 5.5 mm (0.215'') and a thickness
of about 10 microns (0.0004''). The tape was partially joined to
the wrapped tube by melting the underlying FEP adjacent to portions
of the stent wire using a soldering iron. A sacrificial compression
tape was helically wrapped onto the stent graft. The compression
tape was about 51 mm (2'') wide, about 0.5 mm (0.02'') thick and
was wrapped with an approximate 50% overlap. An additional
sacrificial film was wrapped to assist in the subsequent heat
treatment compression step. This film was an ePTFE tape having a
longitudinal fibril/strength orientation, a thickness of about 2.5
microns (0.0001'') and a width of about 51 mm (2''). Five passes
were applied with an approximate 50% overlap between the film
layers.
[0092] The assembly was then heat treated in an air convection oven
to bond the film layers together (as essentially described in U.S.
Pat. No. 6,352,561 to Leopold). During this heat treat cycle, the
film compressed down against the mandrel causing the melted FEP to
flow into the underlying film layers, joining the graft layers
together along with the wire stent. After cooling the sacrificial
film compression layers were removed, the ends of the graft
material were trimmed to length and the stent graft was removed
from the mandrel. The resulting stent graft is depicted in FIG. 8,
with the exception of the optional sealing cuffs (FIG. 8, 806,
810).
EXAMPLE 2
Construction of a Highly Conformable Stent Graft Having an Integral
Side Branch Portal
[0093] Referring to FIGS. 2A and 2B, a metallic mandrel 200 was
fabricated having a slot 202 formed into one end of the mandrel.
The slot 202 terminates onto a back wall 204. The mandrel had a
diameter of about 31 mm and the slot was about 12.5 mm wide, by
about 10 mm deep and about 13 cm long. As shown in FIG. 2B, an
inner tube 206 was radially stretched onto the mandrel 200,
covering a portion of the mandrel groove 202. The inner tube was an
extruded and expanded tube of polytetrafluoroethylene (PTFE). The
inner tube had a length of about 60 mm, a wall thickness of about
0.06 mm and a diameter of about 26 mm. The inner tube had a
substantial fibril orientation in the longitudinal direction so
that the tube was relatively strong in the longitudinal direction
while being relatively weak in the radial direction.
[0094] As shown in FIG. 3A the mandrel 200 was covered by the inner
tube 206. The inner tube was cut, forming a slit 300 at the back
wall 204 of the mandrel groove 202.
[0095] To further strengthen the inner tube (FIG. 3A, 206), two
additional polymeric sheets were added onto the inner tube prior to
the insertion of the secondary stent assembly. The strengthening
layers were then deformed into the mandrel groove, providing
additional support to the inner tube/secondary stent assembly. The
strengthening layers comprised densified ePTFE provided with an
adhesive coating of thermoplastic fluorinated ethylene propylene
(FEP) referred to hereinafter as "substantially impermeable
ePTFE/FEP insulating tape". The FEP of the strengthening layers was
oriented towards the base tube. EPTFE is well known in the medical
device arts; it is generally made as described by U.S. Pat. Nos.
3,953,566 and 4,187,390 to Gore. The particular strengthening
layers described herein were slit from a substantially non-porous
ePTFE/FEP film having a thickness of about 0.0064 mm, an isopropyl
bubble point of greater than about 0.6 MPa, a Gurley No.
(permeability) of greater than 60 (minute/1 square inch/100 cc);
(or 60 (minute/6.45 square cm/100 cc)), a density of 2.15 g/cc and
a tensile strength of about 309 MPa in the length direction (i.e.,
the strongest direction). The first strengthening layer was about
25 mm wide by about 25 mm long and was centered over the mandrel
slot about 15 mm from the slot back wall (towards the end of the
mandrel). The second strengthening layer was about 25 mm wide and
about 40 mm long and was centered over the mandrel slot abutting
the slot back wall 204.
[0096] As shown in FIG. 3B, a secondary stent assembly 302 was
aligned to the mandrel groove 202, mandrel back wall 204,
strengthening layers and inner tube slit 300. A first support
segment (subsequently described) was placed into the secondary
stent assembly and the secondary stent assembly 302 (with the first
support segment) was then inserted into the mandrel groove 202,
deforming the inner tube 206 (and strengthening layers) into the
mandrel groove. The back wall 204 defined the opening in the
innermost tube (130, FIG. 1E).
[0097] To control the deformed shape of the inner tube, a support
segment was placed into the secondary stent assembly and into the
mandrel groove, as depicted in FIGS. 4A and 4B. Shown in FIG. 4A is
a side view schematic of the mandrel 200, the groove 202 and the
groove back wall 204. Shown in FIG. 4B is a side view schematic of
the mandrel 200, mandrel groove 202 and inner tube 206. The
secondary stent assembly 302 was placed over a first support
segment 400 having an end formed to mate to the mandrel groove back
wall 204. The opposing end of the first support segment had a
tapered or angulated wall as depicted in FIG. 4B. A second support
segment 402 was placed into the mandrel groove 202 under the inner
tube 206. The second support structure had flat walls and was used
to hold of the first support structure 400 in place. The inner tube
206 is shown deformed into the mandrel groove 202. The inner tube
206 is also shown having a tapered, beveled or angulated wall
portion 404 formed by the angulated wall of support segment
400.
[0098] A secondary stent assembly was assembled as outlined in
FIGS. 5A through 5D. As shown in FIGS. 5A and 5B, a polymeric tube
502 was slip-fit onto a mandrel 500. The tube was formed from a
film of the same material used for the strengthening layers as
previously described. The film was helically wrapped onto a mandrel
having a diameter of about 8 mm with the FEP layer oriented away
from the mandrel. The wrapped mandrel was then heat set to fuse the
FEP/ePTFE layers forming a tube. An undulating wire was formed into
a ring stent 506 by winding the wire onto a mandrel with protruding
pins. The diameters of the mandrel and pins along with the
locations of the pins dictated the final configuration of the ring
stent. The wire was Nitinol and had a diameter of about 0.15 mm.
The undulating stent pattern had an apex to apex length of about 5
mm. After the wire was wound onto the mandrel, the mandrel and wire
were heat treated and quenched in room temperature water to set the
shape of the stent. The wire was then removed from the mandrel. The
ends of the wire were joined together with a section of polymeric
heat shrink tubing, forming ring stent 506. Two of these ring
stents 506 were then placed onto the polymeric tube 502. Radiopaque
gold marker bands 504 were then placed onto the polymeric tube
502.
[0099] Next, as shown in FIG. 5C, one end of the polymeric tube 502
was inverted and drawn over the wire ring stents 506 and radiopaque
marker bands 504. The mandrel, polymeric tube, ring stents and
radiopaque bands were then heat treated to bond the components
together into a stent assembly. The assembly was removed from the
mandrel and trimmed to length, forming a secondary stent assembly
302 as shown in FIG. 5D. The secondary stent assembly was then
placed onto a first support segment 400.
[0100] As previously described (FIG. 4B), the secondary stent (or
secondary stent assembly) and the first support assembly were then
inserted into the mandrel groove 202, deforming the inner tube 206
into the mandrel groove. A second support segment 402 was placed
into the mandrel groove 202 under the inner tube 206. The assembly
shown in FIG. 4B was then covered with an outer support film. The
support was formed from a film of the same material used for the
strengthening layers as previously described. The film was about 30
mm wide by about 27 mm wide and was centered over the mandrel slot
about 6 mm behind the slot back wall (away from the mandrel end).
The FEP layer was oriented down toward the mandrel.
[0101] To provide resistance to fluid permeation and to enhance the
radial strength of the base tube, a film of densified ePTFE was
wrapped over the base tube. The film was a thin, strong
fluoropolymer; a particularly preferred material for this
application is a non-porous ePTFE provided with an adhesive coating
of thermoplastic fluorinated ethylene propylene (FEP), referred to
hereinafter as "substantially impermeable ePTFE/FEP insulating
tape". The FEP was oriented down against the base tube. EPTFE is
well known in the medical device arts; it is generally made as
described by U.S. Pat. Nos. 3,953,566 and 4,187,390 to Gore. The
particular tape described herein is slit from a substantially
non-porous ePTFE/FEP film having a thickness of about 0.0064 mm, an
isopropyl bubble point of greater than about 0.6 MPa, a Gurley No.
(permeability) of greater than 60 (minute/1 square inch/100 cc);
(or 60 (minute/6.45 square cm/100 cc)), a density of 2.15 g/cc and
a tensile strength of about 309 MPa in the length direction (i.e.,
the strongest direction). The film had a width of about 19 mm
(0.75'') with four passes helically wrapped with a pitch angle of
about 86.degree..
[0102] To further enhance the radial strength of the base tube and
to provide an open structure bonding layer, an additional layer of
film was applied. The ePTFE film had a high degree strength in the
longitudinal direction and had a very open microstructure. The open
microstructure enhanced the subsequent FEP/ePTFE bonding of a stent
frame to the graft. The film had a thickness of about 2.5 microns
(0.0001'') and a width of about 25.4 mm (1.0''). Eight helically
wrapped layers were applied with a pitch angle of about
83.degree..
[0103] The mandrel and wrapped films were then heat treated in an
air convection oven to bond the film layers together.
[0104] A stent frame was then formed by winding a Nitinol wire onto
a mandrel having protruding pins. A "flat or unrolled" drawing of
the cylindrical mandrel is shown in FIG. 12. Shown is an overall
winding pattern 1200, detailing a first end portion 1202 and a
second end portion 1204. Also shown is a "side branch portal"
configuration 1206 that was incorporated into the overall pattern
to form a branch portal.
[0105] Shown in FIG. 13 is a single circumference winding pattern
shown as 1206. The pattern includes a linear pitch 1300, a pin
diameter 1302, a wire diameter 1304, a wire apex angle 1306, a
circumference 1308 and an apex to base half frequency 1310. The
pattern shown was repeated along the stent length with the
exception of the first and second end portions previously shown in
FIG. 12 (1202, 1204). The optional side branch portal configuration
(FIG. 12, 1206) was incorporated.
[0106] The stent frame was formed according to the following
dimensions as defined in FIG. 13: the linear pitch 1300 was about
9.7 mm (0.383''), the pin diameter 1302 was about 1.6 mm (0.063''),
the wire diameter 1304 was about 0.5 mm (0.0195''), the wire apex
angle 1306 was about 50.4 degrees, the circumference 1308 was about
97.3 mm (3.83'') and the apex to base half frequency 1310 was about
5.3 mm (0.21'').
[0107] The mandrel with the wound wire was then heat treated in an
air convection oven as is commonly known in the art and then
quenched in room temperature water.
[0108] The wire stent was the removed from the winding mandrel. The
wire ends (shown in FIGS. 12, 1202 and 1204) were trimmed and tied
together with high temperature fibers as shown in FIGS. 14, 1402
and 1404. The wire stent was then placed onto the previously film
wrapped tube/mandrel. The stent was partially joined to the wrapped
tube by melting the underlying FEP adjacent to portions of the
stent wire using a soldering iron. A final layer of an ePTFE tape,
laminated with FEP was wrapped over the wire stent according to the
pattern depicted in FIG. 14.
[0109] Shown in FIG. 14 is a stent graft 1400 having an undulating,
helical wire stent 802 surrounding a graft material 804. The stent
was attached to the graft material by a helically applied tape
member 1406. As shown, the first edge of the helically applied tape
member 1406 covers the opposing first apices 814 of the wire stent.
The wrapping pattern section 1408 was incorporated to form a side
branch portal. The tape 1406 was an ePTFE/FEP laminate having a
width of about 5.5 mm (0.215'') and a thickness of about 10 microns
(0.0004''). The tape was partially joined to the wrapped tube by
melting the underlying FEP adjacent to portions of the stent wire
using a soldering iron. A sacrificial compression tape was
helically wrapped onto the stent graft. The compression tape was
about 51 mm (2'') wide, about 0.5 mm (0.02'') thick and was wrapped
with an approximate 50% overlap. An additional sacrificial film was
wrapped to assist in the subsequent heat treatment compression
step. This film was an ePTFE tape having a longitudinal
fibril/strength orientation, a thickness of about 2.5 microns
(0.0001'') and a width of about 51 mm (2''). Five passes were
applied with an approximate 50% overlap between the film
layers.
[0110] The assembly was then heat treated in an air convection oven
to bond the film layers together. During this heat treat cycle, the
film compressed down against the mandrel causing the melted FEP to
flow into the underlying film layers, joining the graft layers
together along with the wire stent. After cooling the sacrificial
film compression layers were removed, the ends of the graft
material were trimmed to length and the stent graft was removed
from the mandrel. The resulting stent graft is depicted in FIG. 8,
with the exception of the optional sealing cuffs (FIG. 8, 806,
810).
[0111] It will be apparent to those skilled in the art that various
modifications and variation can be made in the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *