U.S. patent application number 12/441085 was filed with the patent office on 2010-01-21 for single layer eptfe and discrete bioresorbable rings.
This patent application is currently assigned to C.R. Bard, Inc. Invention is credited to John D. McDermott.
Application Number | 20100016946 12/441085 |
Document ID | / |
Family ID | 39201166 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100016946 |
Kind Code |
A1 |
McDermott; John D. |
January 21, 2010 |
SINGLE LAYER EPTFE AND DISCRETE BIORESORBABLE RINGS
Abstract
A stent-graft, including a generally tubular vascular graft of
biocompatible material, and a plurality of bio-resorbable discrete
annular members spaced apart along a longitudinal axis of the
vascular graft and attached thereto.
Inventors: |
McDermott; John D.;
(Chandler, AZ) |
Correspondence
Address: |
C. R. Bard, Inc.;Bard Peripheral Vascular, Inc.
1415 W. 3rd Street, P.O. Box 1740
Tempe
AZ
85280-1740
US
|
Assignee: |
C.R. Bard, Inc
Murray Hill
NJ
|
Family ID: |
39201166 |
Appl. No.: |
12/441085 |
Filed: |
September 13, 2007 |
PCT Filed: |
September 13, 2007 |
PCT NO: |
PCT/US07/78359 |
371 Date: |
March 12, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60845295 |
Sep 18, 2006 |
|
|
|
Current U.S.
Class: |
623/1.13 ;
139/116.1; 427/2.24 |
Current CPC
Class: |
B05D 3/007 20130101;
B05D 7/22 20130101; Y10T 29/49778 20150115; A61F 2210/0004
20130101; B05D 1/02 20130101; A61F 2002/826 20130101; Y10T 29/49838
20150115; A61F 2/07 20130101; A61F 2240/001 20130101; A61F 2/89
20130101; A61F 2002/075 20130101 |
Class at
Publication: |
623/1.13 ;
427/2.24; 139/116.1 |
International
Class: |
A61F 2/06 20060101
A61F002/06; B05D 3/00 20060101 B05D003/00; D03D 23/00 20060101
D03D023/00 |
Claims
1. A stent-graft, comprising: a generally tubular vascular graft of
biocompatible material; and a plurality of discrete bio-resorbable
annular members spaced apart along a longitudinal axis of the
vascular graft and attached thereto.
2. The stent-graft according to claim 1, wherein the vascular graft
is comprised of expanded polytetrafluoroethylene (ePTFE).
3. The stent-graft according to claim 2, the annular members
including a coating of polyurethane that covers at least a portion
of the annular members in contact with ePTFE.
4. The stent-graft according to claim 3, further comprising a layer
of amorphous fluoropolymer including tetrafluoroethylene (TEF) and
4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole, or a
perfluoroelastomer, covering the annular members.
5. The stent-graft according to claim 4, wherein the layer of
amorphous fluoropolymer comprises powder that is sintered to the
vascular graft.
6. The stent-graft according to claim 3, further comprising a
solvent layer disposed onto the surface of the vascular graft that
contacts the polyurethane to bond the annular members to the
vascular graft.
7. The stent-graft according to claim 6, wherein the solvent
comprises Tetrahydrofuran (THF).
8. (canceled)
9. (canceled)
10. (canceled)
11. The stent-graft according to claim 1, wherein the annular
members are woven into the tubular base and attached thereto with
bio-resorbable sutures.
12. The stent-graft according to claim 1, wherein the annular
members are attached to an abluminal surface of the vascular
graft.
13. (canceled)
14. (canceled)
15. (canceled)
16. The stent-graft according to claim 1, wherein the
bio-resorbable material is a balloon-expandable material.
17. The stent-graft according to claim 1, further comprising a
bio-resorbable adhesive disposed between the annular members and
the vascular graft.
18. (canceled)
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
23. (canceled)
24. (canceled)
25. (canceled)
26. (canceled)
27. (canceled)
28. (canceled)
29. (canceled)
30. (canceled)
31. (canceled)
32. (canceled)
33. (canceled)
34. (canceled)
35. (canceled)
36. A method of making a stent-graft, comprising: providing a
plurality of discrete radially expandable annular members including
a bio-resorbable balloon-expandable material; coating the annular
members with a polyurethane material; positioning the coated
annular members over a generally tubular expanded
polytetrafluoroethylene vascular graft along a longitudinal axis
thereof in spaced apart relation; and disposing a solvent between
the coated annular members and the vascular graft.
37. The method according to claim 36, wherein the disposing
comprises spraying the vascular graft with THF.
38. The method according to claim 37, wherein the spraying
comprises spraying the inside surface of the vascular graft with
THF.
39. (canceled)
40. (canceled)
41. (canceled)
42. The method according to claim 36, wherein a laser alignment
fixture is utilized to space the annular members apart along the
longitudinal axis of the vascular graft.
43. (canceled)
44. (canceled)
45. (canceled)
46. The method according to claim 36, wherein the positioning
further comprises arranging the annular members in a manner to
prevent interference between adjacent annular members upon radial
compression of the stent-graft to a delivery configuration.
47. The method according to claim 36, further comprising creating a
plurality of micro-openings through a wall of the vascular
graft.
48. (canceled)
49. A method of making a stent-graft, comprising: providing a
plurality of discrete radially expandable bio-resorbable annular
members; positioning the annular members over a generally tubular
vascular graft along a longitudinal axis thereof in spaced apart
relation; and weaving portions of the annular members into the base
layer and attaching the annular members to the base layer with
bio-resorbable sutures.
50. The method according to claim 49, wherein a laser alignment
fixture is utilized to space the annular members apart along the
longitudinal axis of the vascular graft.
51. (canceled)
52. The method according to claim 49, wherein the weaving step
comprises positioning a first set of apices of adjacent annular
members on opposing surfaces of the vascular graft.
53. (canceled)
54. (canceled)
55. (canceled)
56. (canceled)
Description
PRIORITY
[0001] This application claims the benefit of priority to U.S.
Provisional Patent Application No. 60/845,295, filed Sep. 18, 2006,
which is incorporated by reference into this application as if
fully set forth herein.
BACKGROUND
[0002] Intraluminal prostheses used to maintain, open, or dilate
blood vessels are commonly known as stents. Stent constructions
generally include lattice type cylindrical frames that define a
plurality of openings. Common frameworks for stents include
individual rings linked along the length of the stent by a linking
member, a continuous helically wrapped member (that may include one
or more linking members), a braid or a mesh formed into a tubular
structure, and a series of interconnected struts. Stents are either
self-expanding or balloon expandable. Self-expanding stents are
delivered to a blood vessel in a collapsed condition and expand in
vivo following the removal of a constraining force and/or in the
presence of an elevated temperature (due to material properties
thereof), whereas balloon expandable stents are generally crimped
onto a balloon catheter for delivery and require the outwardly
directed force of a balloon for expansion. Stents can be made of
various metals and polymers. Stents can also be made of
bioabsorbable materials, such as described in U.S. Pat. No.
6,245,103 to Stinson et al., which is incorporated by reference in
its entirety into this application.
[0003] Synthetic vascular grafts are routinely used to restore the
blood flow in patients suffering from vascular diseases. For
example, prosthetic grafts made from expanded
polytetrafluoroethylene (ePTFE) are commonly used and have shown
favorable patency rates, meaning that depending on a given time
period, the graft maintains an open lumen for the flow of blood
therethrough. Grafts formed of ePTFE include a microstructure
characterized by spaced apart nodes connected by fibrils, the
distance between the nodes defined as internodal distance
(IND).
[0004] It is known in the art to use stents in combination with
vascular grafts to form stent-grafts. In one type of stent-graft,
individual rings without a linking member are spaced apart along a
length of the stent-graft. The rings may be encapsulated between
two layers, such as described in U.S. Pat. No. 5,123,917 to Lee, or
may be disposed on a surface of a graft, such as described in U.S.
Pat. No. 6,364,903 to Tseng et al., each of which is incorporated
by reference in its entirety into this application.
[0005] The following references relate to stent-grafts: U.S. Pat.
No. 6,626,939, U.S. Pat. No. 6,733,524, U.S. Patent Application
Publication No. 2004/0098095 and U.S. Patent Application
Publication No. 2004/0181278, each of which is incorporated by
reference in its entirety into this application.
[0006] Applicants have recognized that it would be desirable to
provide a stent-graft including an ePTFE graft and discrete
bio-resorbable members, embodiments of which are described herein
along with methods of making same.
SUMMARY
[0007] Accordingly, in one embodiment, a stent-graft includes a
generally tubular vascular graft of biocompatible material, and a
plurality of discrete bio-resorbable annular members spaced apart
along a longitudinal axis of the vascular graft and attached
thereto.
[0008] In one embodiment, a method of making a stent-graft includes
providing a plurality of discrete radially expandable annular
members including a bio-resorbable balloon-expandable material,
coating the annular members with a polyurethane material,
positioning the coated annular members over a generally tubular
expanded polytetrafluoroethylene vascular graft along a
longitudinal axis thereof in spaced apart relation, and disposing a
solvent between the coated annular members and the vascular
graft.
[0009] In another embodiment, a method of making a stent-graft
includes providing a plurality of discrete radially expandable
bio-resorbable annular members, positioning the annular members
over a generally tubular vascular graft along a longitudinal axis
thereof in spaced apart relation, and weaving portions of the
annular members into the base layer and attaching the annular
members to the base layer with bio-resorbable sutures.
[0010] In one embodiment of a stent-graft and delivery system, the
delivery system includes a balloon catheter and an outer sheath,
the stent-graft is positioned over a balloon of the balloon
catheter, the outer sheath is positioned over the stent-graft, and
the stent-graft includes a generally tubular vascular graft of
biocompatible material and a plurality of discrete radially
expandable bio-resorbable annular members spaced apart along a
longitudinal axis of the vascular graft and attached thereto.
[0011] In one embodiment, a method of treating a blood vessel
includes providing a balloon catheter including a balloon on a
distal end thereof and a stent-graft positioned over a length of
the balloon, the stent-graft including a generally tubular vascular
graft of biocompatible material and a plurality of discrete
radially expandable bio-resorbable annular members spaced apart
along a longitudinal axis of the vascular graft and attached
thereto, inserting the balloon catheter in a blood vessel,
navigating the balloon to a predetermined region of the blood
vessel, and inflating the balloon to bring a surface of one or more
of the annular members in contact with the blood vessel wall.
[0012] In one embodiment, a method of loading a stent-graft in a
sheath includes forming a stent-graft, including positioning a
plurality of discrete annular bio-resorbable members along a
surface of an ePTFE graft, the annular members spaced apart along a
longitudinal axis of the ePTFE graft and attached thereto, the
annular members having an expanded configuration defining an
expanded perimeter, compressing the stent-graft, the annular
members collapsing to a collapsed configuration defining a
collapsed perimeter smaller than the expanded perimeter, and
positioning a sheath over the stent-graft, the sheath maintaining
the annular members in the collapsed configuration.
[0013] These and other embodiments, features and advantages will
become more apparent to those skilled in the art when taken with
reference to the following more detailed description of the
invention in conjunction with the accompanying drawings that are
first briefly described.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of an embodiment of a
stent-graft with discrete annular members loaded onto an expandable
member.
[0015] FIG. 2 is a perspective view of one embodiment of a discrete
annular member in isolation.
[0016] FIGS. 3A-C are perspective views of separate stages of
making one embodiment of a stent-graft with discrete annular
members.
[0017] FIG. 4 is an enlarged perspective view of another embodiment
of a stent-graft with discrete annular members.
DETAILED DESCRIPTION
[0018] The following description should be read with reference to
the drawings, in which like elements in different drawings are
identically numbered. The drawings, which are not necessarily to
scale, depict selected embodiments and are not intended to limit
the scope of the invention. The description illustrates by way of
example, not by way of limitation, the principles of the invention.
This description will clearly enable one skilled in the art to make
and use the invention, and describes several embodiments,
adaptations, variations, alternatives and uses of the invention,
including what is presently believed to be the best mode of
carrying out the invention.
[0019] The stent-graft described herein may be utilized with
bio-active agents to control the formation of emboli. Bio-active
agents can be coated onto a portion or the entirety of the stent
and/or graft for controlled release of the agents once the
stent-graft is implanted. Bio-active agents can be added to the
prosthesis (e.g., either by a coating or via a carrier medium such
as resorbable polymers) for delivery to the host's vessel or duct.
The bio-active agents may also be used to coat the entire stent,
stent-graft or the graft. A coating may include one or more
non-genetic therapeutic agents, genetic materials and cells and
combinations thereof as well as other polymeric coatings.
[0020] Non-genetic therapeutic agents include anti-thrombogenic
agents such as heparin, heparin derivatives, urokinase, and PPack
(dextrophenylalanine proline arginine chloromethylketone);
anti-proliferative agents such as enoxaprin, angiopeptin, or
monoclonal antibodies capable of blocking smooth muscle cell
proliferation, hirudin, and acetylsalicylic acid; anti-inflammatory
agents such as dexamethasone, prednisolone, corticosterone,
budesonide, estrogen, sulfasalazine, and mesalamine;
antineoplastic/antiproliferative/anti-miotic agents such as
paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine,
epothilones, endostatin, angiostatin and thymidine kinase
inhibitors; anesthetic agents such as lidocaine, bupivacaine, and
ropivacaine; anti-coagulants, an RGD peptide-containing compound,
heparin, antithrombin compounds, platelet receptor antagonists,
anti-thrombin antibodies, anti-platelet receptor antibodies,
aspirin, prostaglandin inhibitors, platelet inhibitors and tick
antiplatelet peptides; vascular cell growth promotors such as
growth factor inhibitors, growth factor receptor antagonists,
transcriptional activators, and translational promotors; vascular
cell growth inhibitors such as growth factor inhibitors, growth
factor receptor antagonists, transcriptional repressors,
translational repressors, replication inhibitors, cell cycle
inhibitors and activators inhibitory antibodies, antibodies
directed against growth factors, bifunctional molecules consisting
of a growth factor and a cytotoxin, bifunctional molecules
consisting of an antibody and a cytotoxin; cholesterol-lowemember
agents; vasodilating agents; cytostatic or cytotoxic and agents
which interfere with endogenous vasoactive mechanisms.
[0021] Genetic materials include anti-sense DNA and anti-sense RNA
as well as other molecules working via the same mechanism of
transcriptional or translational inhibition or activation. Genetic
material also include (sense) DNA or (sense) RNA or equivalents
thereof coding for Genes to replace defective or deficient
endogenous molecules or increase their amount or stability, or
encode for non-endogenous or endogenous modified molecules with
biological effects. Genetic material also includes nucleic acids
affecting Gene expression or other cellular mechanisms by other
ways than described above. Such Genetic materials could be
organized "naked," packed with supporting molecules or in form of
viruses or other vectors. Genes and their expression affected by
above Genetic materials include but are not restricted to: tRNA or
rRNA angiogenic factors including growth factors such as acidic and
basic fibroblast growth factors, vascular endothelial growth
factor, epidermal growth factor, transforming growth factor alpha
and beta, platelet-derived endothelial growth factor,
platelet-derived growth factor, tumor necrosis factor alpha,
hepatocyte growth factor and insulin like growth factor, cell cycle
inhibitors and activators including CD inhibitors, thymidine kinase
("TK") and other agents useful for interfemember with cell
proliferation, transcription factors, translation factors, the
family of bone morphogenic proteins ("BMP's"), BMP-2, BMP-3, BMP-4,
BMP-5, BMP-6 (Vgr-1), BMP-7 (OP-1), BMP-8, BMP-9, BMP-10, BMP-1,
BMP-12, BMP-13, BMP-14, BMP-15, and BMP-16. Desirable BMP's are any
of BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 and BMP-7. These dimeric
proteins can be provided as homodimers, heterodimers, or
combinations thereof, alone or together with other molecules.
Alternatively or, in addition, molecules capable of inducing an
upstream or downstream effect of a BMP can be provided. Such
molecules include any of the "hedgehog" proteins, or the DNA"s
encoding them.
[0022] Cells can be of human origin (autologous or allogeneic) or
from an animal source (xenogeneic), genetically engineered if
desired to deliver proteins of interest at the deployment site. The
cells may be provided in a delivery media. The delivery media may
be formulated as needed to maintain cell function and
viability.
[0023] Suitable polymer materials as a coating or the base material
may include polycarboxylic acids, cellulosic polymers, including
cellulose acetate and cellulose nitrate, gelatin,
polyvinylpyrrolidone, cross-linked polyvinylpyrrolidone,
polyanhydrides including maleic anhydride polymers, polyamides,
polyvinyl alcohols, copolymers of vinyl monomers such as EVA,
polyvinyl ethers, polyvinyl aromatics, polyethylene oxides,
glycosaminoglycans, polysaccharides including cellulose, chitin,
dextran, polyesters including polyethylene terephthalate,
polyacrylamides, polyethers, polyether sulfone, polycarbonate
including tyrosine-derived polycarbonate, polyalkylenes including
polypropylene, polyethylene and high molecular weight polyethylene
and poly(butylene terephthalate) (PBT), halogenated polyalkylenes
including polytetrafluoroethylene, polyurethanes, polyorthoesters,
proteins (including fibrin und casein), polypeptides, silicones,
siloxane polymers, polylactic acid (PLA), polyglycolic acid (PGA),
poly(lactide-co-glycolide) (PLGA) polycaprolactone, polydioxanone,
poly(g-ethyl glutamate), poly(DTH iminocarbonate), poly(bisphenol A
iminocarbonate), poly(ortho ester), polycyanoacrylate, and
polyphosphazene, polyhydroxybutyrate valerate and blends and
copolymers thereof, coatings from polymer dispersions such as
polyurethane dispersions (for example, BAYHDROL.RTM. fibrin,
collagen and derivatives thereof, polysaccharides such as
celluloses, starches, dextrans, alginates and derivatives,
hyaluronic acid, squalene emulsions. Polyacrylic acid, available as
HYDROPLUS.RTM. (Boston Scientific Corporation, Natick, Mass.), and
described in U.S. Pat. No. 5,091,205, the disclosure of which is
incorporated by reference in its entirety into this application, is
particularly desirable.
[0024] One suitable bioabsorbable material for the stent as
described herein can be one or more of a metal alloy shown and
described in U.S. Pat. No. 6,287,332, or the metal alloy shown and
described in U.S. Patent Application Publication No. 2002/0004060,
each of which is incorporated by reference in its entirety into
this application. Preferably, the metallic bioabsorbable material
is selected from a first group consisting essentially of:
magnesium, titanium, zirconium, niobium, tantalum, zinc, silicon,
and combinations thereof. Also provided are mixtures and alloys of
metallic bioabsorbable materials, including those selected from the
first group. Various alloys of the materials in the first group can
also be used as a metallic bioabsorbable material, such as a
zinc-titanium alloy, for example, as discussed in U.S. Pat. No.
6,287,332 to Bolz et al., which is incorporated by reference in its
entirety into this application. The physical properties of the
alloy can be controlled by selecting the metallic bioabsorbable
material, or forming alloys of two or more metallic bioabsorbable
materials. For example, the percentage by weight of titanium can be
in the range of about 0.1% to about 1%, which can reduce the
brittle quality of crystalline zinc. Without being bound to theory,
it is believed that the addition of titanium leads to the formation
of a Zn.sub.15 Ti phase. In another embodiment, gold can be added
to the zinc-titanium alloy at a percentage by weight of about 0.1%
to about 2%, which is believed to result in a further reduction of
the grain size when the material cures and further improving the
tensile strength of the material.
[0025] In some embodiments, the metallic bioabsorbable material can
be an alloy of materials from the first group and a material
selected from a second group consisting essentially of: lithium,
sodium, potassium, calcium, iron, manganese, and combinations
thereof. The metallic bioabsorbable material from the first group
can form a protective oxide or passivation coating upon exposure to
blood or interstitial fluid. The material from the second group is
preferably soluble in blood or interstitial fluid to promote the
dissolution of the oxide coating. Also provided are mixtures and
alloys of metallic bioabsorbable materials, including those
selected from the second group and combinations of materials from
the first group and the second group.
[0026] Briefly, the combination of metal materials can be a metal
alloy, the selection of the alloy constituents (as explained in
detail below) serving to attain the prerequisite of biocompatible
decomposition. Consequently, the metal alloy may consist of a
combination of material that will decompose in the body
comparatively rapidly while forming harmless constituents. Such
alloy may include a component A which covers itself with a
protective oxide coating. This component A is selected from one or
several metals of the group of magnesium, titanium, zirconium,
niobium, tantalum, zinc, silicon, or combinations thereof. For
uniform dissolution of the mentioned oxide coat to be attained, a
component B is added to the alloy, possessing sufficient solubility
in blood or interstitial fluid, such as lithium sodium, potassium,
calcium, iron or manganese. The corrosion rate is adjusted by way
of the composition so that gases, such as hydrogen, which evolve
during the corrosion of lithium, sodium, potassium, magnesium,
calcium or zinc, dissolve physically and essentially not forming
any macroscopic gas bubbles. Other alloys can be utilized such as,
for example, alloy of lithium and magnesium in the ratio of about
60:40; a sodium-magnesium alloy; a zinc-titanium alloy--the
percentage by weight of which is in the range of about 0.1% to
about 1% with the gold being optionally added at a percentage by
weight of about 0.1% to about 2%. Further details relating to these
metallic bioabsorbable materials are found in U.S. Pat. No.
6,287,332 to Bolz et al.
[0027] Other materials for the stent as described herein can
include biodegradable polymers including shape memory polymers,
such as, for example, polylactic acid, i.e., PLA, polyglycolic
acid, i.e., PGA, polydioxanone, i.e., PDS, polyhydroxybutyrate,
i.e., PHB, polyhydroxyvalerate, i.e., PHV and copolymers or a
combination of PHB and PHV (available commercially as Biopol.RTM.),
polycaprolactone (available as Capronor.RTM.), polyanhydrides
(aliphatic polyanhydrides in the back bone or side chains or
aromatic polyanhydrides with benzene in the side chain),
polyorthoesters, polyaminoacids (e.g., poly-L-lysine, polyglutamic
acid), pseudo-polyaminoacids (e.g., with back bone of
polyaminoacids altered), polycyanoacrylates, or
polyphosphazenes.
[0028] As used herein, the term "bio-resorbable" includes a
suitable bio-compatible material, mixture of materials or partial
components of materials being degraded into other generally
non-toxic materials by an agent present in biological tissue (i.e.,
being bio-degradable via a suitable mechanism, such as, for
example, hydrolysis) or being removed by cellular activity (i.e.,
bioresorption, bioabsorption, or bioresorbable), by bulk or surface
degradation (i.e., bioerosion such as, for example, by utilizing a
water insoluble polymer that is soluble in water upon contact with
biological tissue or fluid), or a combination of one or more of the
bio-degradable, bio-erodable, or bio-resorbable material noted
above.
[0029] Referring now to FIG. 1, a stent-graft 10 is shown disposed
over an inflatable member 2 on a distal end of a catheter, such as
a balloon catheter. The stent-graft 10 includes a generally tubular
vascular graft 12 and discrete annular members 14 spaced apart
along a longitudinal axis of the graft 12, the graft 12 providing a
base member or substrate for the annular members 14. The vascular
graft 12 may be made of a polymeric material, such as, for example,
Dacron, nylon, polyester, polyurethane and fluoropolymers, such as
perfluoroelastomers and the like, but in the preferred embodiment
is made of expanded polytetrafluoroethylene (ePTFE). As known in
the art, an ePTFE vascular graft may be manufactured in a number of
ways, including, for example, extrusion of a tube (seamless),
extrusion of a sheet that is subsequently formed into a tube (one
or more seams), helical wrapping of ePTFE tape around a mandrel
(e.g., multiple seams or preferably a single helical seam), etc.
The preferred method used for forming an ePTFE vascular graft in
the present invention is extrusion of a generally tubular member.
Extrusion and expansion of the tubular member may be controlled to
provide a range of internodal distances. In a preferred embodiment,
the average internodal distance is in the range of approximately 10
microns to approximately 110 microns.
[0030] While the discrete annular members 14 may be made of a
self-expanding or balloon expandable material, in the embodiment
shown in FIG. 1, the annular members 14 are made of a balloon
expandable bio-resorbable material, such as any of those discussed
above. In one embodiment, the annular members 14 include a coating
16. The coating 16 may cover substantially the entire surface area
of the annular members or may only cover a portion thereof. In a
preferred embodiment, the annular members 14 include a coating that
covers at least the portion in contact with the vascular graft 12
to assist with attachment of the annular members 14 with the
vascular graft 12. The coating may include a polymer that is
capable of adhering to the vascular graft 12, through the
application of, for example, heat, pressure, solvents, adhesives
(e.g., bio-resorbable adhesives), or combinations thereof. Suitable
polymers for the coating may include, for example,
polytetrafluoroethylene (PTFE), ePTFE, polyurethane, fluorinated
ethylene propylene (FEP), an amorphous fluoropolymer, and
combinations thereof. In a preferred embodiment, the polymer
includes an amorphous fluoropolymer including tetrafluoroethylene
(TEF) and 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole, or a
perfluoroelastomer, as described in U.S. Patent Application
Publication No. 2005/0131527, which is incorporated by reference in
its entirety into this application. The coating may have a
thickness in the range of approximately 1 micron to approximately
100 microns. The coating may be in the form of particles or powder,
and may be applied to the annular members 14 and/or to the vascular
graft 12 by spraying, dip coating, or other methods known to one
skilled in the art. In one embodiment, the coating is a
fluoropolymer including TEF in powdered form which is disposed
directly on a surface of the vascular graft 12 so that when the
annular members 14 are positioned on the surface, the powder is
positioned between the vascular graft 12 and a surface of one or
more annular members 14.
[0031] Referring to FIG. 2, one embodiment of an annular member 20
is illustrated. Annular member 20 includes struts 22 arranged in an
undulating configuration that is preferably closed ended. The
struts 22 intersect at an apex to form a first set of apices 24 and
a second set of apices 26 offset therefrom, such that annular
member 20 includes an equal number of first and second apices 24,
26. Each apex includes a peak P and a trough T. The lengths of the
struts 22 may be uniform, as shown, or may be varied about the
circumference of the annular member. For example, the annular
member could include two or more strut lengths arranged in patterns
about its circumference. Many other annular member configurations
are also possible and are within the scope of the invention, such
as, for example, sinusoidal patterns, meandering curve patterns,
other curvilinear patterns, etc. The struts may be substantially
straight along their lengths, as shown, or may be curved or
wave-like. Any type of pattern and/or strut length or shape can be
combined with other patterns and/or strut lengths or shapes to form
a non-uniform annular member. Moreover, it should be appreciated
that the shape, size, thickness, material and/or other
characteristic of the annular members can be varied along the
length of the stent-graft. Further, the undulations are not limited
to zig-zag patterns but can be wave-like in pattern. The wave-like
pattern can also be generally sinusoidal in that the pattern may
have the general form of a sine wave, whether or not such wave can
be defined by a mathematical function. Alternatively, any wave-like
forms can be employed so long as it has amplitude and displacement.
For example, a square wave, saw tooth wave, or any applicable
wave-like pattern defined by the struts where the struts have
substantially equal lengths or unequal lengths.
[0032] In one embodiment, annular members 20 are positioned along a
surface of a vascular graft 12 so that the peak P of a first
annular member 20 is aligned with a trough T of an adjacent annular
member 20, the adjacent annular members 20 being spaced a
sufficient distance apart to prevent interference between the
annular members 20 upon radial compression of the stent-graft. For
example, the annular members 20 may be attached to a vascular graft
in an expanded configuration defining an expanded perimeter of the
annular members 20 and are subsequently radially compressed for
delivery to a blood vessel to a collapsed configuration, defining a
collapsed perimeter of the annular members 20 smaller than the
expanded perimeter of the annular members 20. The sufficient
distance between adjacent annular members to prevent interference
is dependent on a variety of factors, such as, for example, length,
shape, and/or other characteristics of the struts, but in a
preferred embodiment with annular members 20 having a uniform strut
length of approximately 500 microns to approximately 1500 microns
and having peaks P and troughs T of adjacent annular members 20
aligned, a sufficient distance between adjacent annular members 20
is in the range of approximately 0.1 millimeter to approximately 1
millimeter. In other embodiments, adjacent annular members 20 may
have peaks P and/or troughs T offset circumferentially to each
other.
[0033] Markers M1, M2, M3, M4 . . . Mn can be provided for all of
the embodiments described herein. The marker Mn can be formed from
the same material as the stent as long as the material is
radiographic or radiopaque. The marker material can also be formed,
for example, from gold, tantalum, platinum, and combinations
thereof. One or more markers can be formed from a marker material
different from other markers.
[0034] Attachment of the annular members to the vascular graft may
be accomplished by various methods, which can be facilitated by the
materials chosen for the annular members, vascular graft and/or
coatings, if utilized. In a preferred embodiment illustrated in
FIGS. 3A-C, an ePTFE vascular graft 12 is positioned over a mandrel
4. The ePTFE graft 12 may be sintered, unsintered, or partially
sintered, but in a preferred embodiment, the ePTFE graft 12 is
sintered. Using a loading tool 6, a predetermined number of annular
members 30 with a polyurethane coating are positioned along the
outer (abluminal) surface of the ePTFE graft 12. In a preferred
embodiment, there are approximately 5 to approximately 100 annular
members 30 positioned over an ePTFE graft having a length in the
range of approximately 10 millimeters to approximately 200
millimeters. In one embodiment, the annular members 30 are
pre-dilated (expanded) by the tool 6 for moving into position on an
outer surface of the ePTFE graft 12. Depending on the material
properties of the annular members 30, an additional crimping step
may be required to secure the annular members in position. Once the
annular members are initially positioned on a surface of the graft
12, a laser alignment fixture is optionally utilized to optimally
space the adjacent annular members with respect to one another.
[0035] The mandrel 4 is then removed from the assembly and the
inside surface of the ePTFE graft 12 is sprayed, as depicted in
FIG. 3A, with a solvent, such as tetrahydrofuran (THF), so that the
THF migrates through the wall of the ePTFE graft. The spraying may
be accomplished using different methods known to one skilled in the
art. For example, the graft 12 may be suspended such that a lumen
of the graft 12 is accessible; a spraying mechanism 8 is then
inserted into the lumen and rotated to contact THF with a surface
of the lumen. The entire surface of the lumen may be covered or
select portions thereof. Alternatively, a mandrel with openings may
be inserted into the lumen, the mandrel attached to a source of
THF, where the THF is delivered to the mandrel and through the
openings to contact a surface of the graft 12. Another possibility
includes utilizing a needle device attached to a source of THF and
inserting the needle through the wall of the graft 12 at various
locations, where THF is delivered through the needle at each
location to contact a surface of the lumen. The interaction between
the ePTFE, THF and polyurethane coating on the annular members 30
bonds the annular members 30 to the ePTFE graft 12 (the THF or
other aprotic solvent is believed to dissolve polyurethane, such
that when a small amount contacts the polyurethane coating, a
mechanical bond is developed between the coating and the ePTFE
graft 12).
[0036] In another embodiment, a suitable solvent, such as, for
example, an aprotic solvent including dimethylacetamide (DMSE),
dimethylforamide, THF, or their mixtures, is sprayed or otherwise
disposed over the outside surface of the ePTFE graft 12 after the
annular members 30 have been positioned thereover. Alternatively,
the ePTFE graft 12 with annular members 30 could be dip coated in a
suitable solvent. In another embodiment, the annular members 30 are
positioned over an inner (luminal) surface of the ePTFE graft 12
prior to spraying of the solvent over the outer surface or inner
surface of the ePTFE graft 12. In yet another embodiment, the
annular members 30 are coated with PTFE and the ePTFE graft 12 is
initially unsintered. Following placement of the annular members 30
over the graft 12, the assembly is heated above the crystalline
melt point of PTFE to sinter the annular members 30 to the graft
12. Although the preferred embodiments are directed to single layer
vascular grafts, it is within the scope of the invention to provide
two or more graft layers. For example, the annular members could be
disposed between two generally tubular graft layers, the graft
layers being continuous along their length; the annular members
could be disposed between two generally tubular graft layers, at
least one of the graft layers including openings, as shown and
described in U.S. Pat. Nos. 6,398,803 and 6,770,087 to Layne et
al., which is incorporated by reference in its entirety into this
application; or the annular members could be disposed between a
generally tubular graft layer and strips and bands of covering
material, such as shown and described in U.S. Pat. No. 6,558,414 to
Layne, which is incorporated by reference in its entirety into this
application. Other stent-graft arrangements with respect to
covering material and annular members known to one skilled in the
art are also contemplated herein.
[0037] In one attachment method, annular members 40, which may or
may not include a coating, are woven into a vascular graft 42. In
one embodiment, shown in FIG. 4, the annular members 40, having a
zig-zag configuration with struts intersecting at first apices and
second apices offset from the first apices, are woven into the
vascular graft 42. In a preferred embodiment, the vascular graft 42
is made of ePTFE. As illustrated, the peaks and troughs of the
annular members 40 are generally aligned, with the first apices of
adjacent annular members 40 disposed on opposite surfaces of the
vascular graft 42. For example, if the first apices of annular
members 40, are disposed on the inside surface of the vascular
graft 42, then the first apices of annular members 402 are disposed
on the inside surface of the vascular graft 42. Bio-resorbable
sutures 44 are utilized in the embodiment of FIG. 4 to attach the
annular members 40 to the vascular graft 42. The sutures 44 may be
positioned around each apex of the annular members 40, every other
apex, every apex of the first apices, every apex of the second
apices, at a mid point of each strut, at a mid-point of every
second, third, fourth, etc. strut, at locations where the strut
passes through the wall of the vascular graft 42, or any other
pattern or arrangement that would prevent pre-mature detachment of
the annular members 40 from the vascular graft 42. In certain
embodiments, additional attachment methods are utilized in
conjunction with the sutures 44, such as, for example, spraying
with a solvent, such as THF (e.g., the annular members 40 include a
coating, such as polyurethane), disposing an adhesive, such as a
bio-resorbable adhesive, over one or more surfaces of the vascular
graft 42 (e.g., at locations of contact with the annular members
40), heating the stent-graft (e.g., the ePTFE is unsintered and the
annular members 40 include a coating, such as PTFE), applying a
uniform pressure to the assembled stent-graft along both inner and
outer surfaces, or any combination thereof.
[0038] Referring back to FIG. 1, the annular members 14 include a
balloon expandable bio-resorbable material and are attached to the
vascular graft 12 in an original or non-expanded configuration with
a original perimeter. In one embodiment of treating a blood vessel,
the stent-graft 10 is positioned over a length of the balloon 2 of
the balloon catheter, which may be a component of a delivery system
(e.g. the balloon catheter may be coaxially disposed in an outer
sheath), and the balloon catheter/delivery system is inserted
intraluminally in a patient to a predetermined region of a blood
vessel. The balloon is then inflated to expand the stent-graft, the
annular members 14 expanding to an expanded configuration with an
expanded perimeter larger than the original perimeter, to bring a
surface of one or more of the annular members in contact with the
blood vessel wall. After positioning is confirmed, the balloon is
deflated and the balloon catheter removed from the blood
vessel.
[0039] In another embodiment, the annular members include a
self-expanding bio-resorbable material and are attached to a
vascular graft in an expanded configuration defining an expanded
perimeter. The stent-graft is then compressed, the annular members
collapsing to a collapsed configuration with a collapsed perimeter
smaller than the expanded perimeter. A constraining sheath, which
may be a component of a delivery system, is positioned over the
stent-graft to maintain the annular members in the collapsed
configuration and the sheath is delivered intraluminally in a
patient to a predetermined region of a blood vessel. The
constraining sheath is then removed from the stent-graft, allowing
the annular members to expand such that one or more annular members
have a surface in contact with the blood vessel wall. A balloon can
optionally be inserted and inflated thereafter to ensure contact
with the blood vessel wall and positioning of the stent-graft in
the blood vessel.
[0040] Following deployment of a stent-graft with bio-resorbable
annular members in a blood vessel, the annular members will begin
to degrade, while the vascular graft is designed to remain
permanently implanted (although slight degradation to the graft may
take place over time). The time for degradation of the annular
members will depend on a number of factors, including, for example,
member material, member thickness, member surface area, the type
and thickness of the coating (if utilized), etc. In the preferred
embodiments, the bioresorption is configured to be from 3 months to
2 years for complete resorption.
[0041] This invention has been described and specific examples have
been portrayed. While the invention has been described in terms of
particular variations and illustrative figures, those of ordinary
skill in the art will recognize that the invention is not limited
to the variations or figures described. In addition, where methods
and steps described above indicate certain events occurring in
certain order, those of ordinary skill in the art will recognize
that the ordering of certain steps may be modified and that such
modifications are in accordance with the variations of the
invention. Additionally, certain of the steps may be performed
concurrently in a parallel process when possible, as well as
performed sequentially as described above. Therefore, to the extent
there are variations of the invention, which are within the spirit
of the disclosure or equivalent to the inventions found in the
claims, it is the intent that this patent will cover those
variations as well. Finally, all publications and patent
applications cited in this specification are herein incorporated by
reference in their entirety as if each individual publication or
patent application were specifically and individually put forth
herein.
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