U.S. patent application number 09/944668 was filed with the patent office on 2003-03-06 for hybrid balloon expandable/self expanding stent.
Invention is credited to Bashiri, Mehran.
Application Number | 20030045923 09/944668 |
Document ID | / |
Family ID | 25481842 |
Filed Date | 2003-03-06 |
United States Patent
Application |
20030045923 |
Kind Code |
A1 |
Bashiri, Mehran |
March 6, 2003 |
Hybrid balloon expandable/self expanding stent
Abstract
A stent comprises a tubular member having openings therein and
having a plurality of interconnected members and one or more
frangible restraining members. The frangible restraining members
break upon partial expansion of the stent. Thereafter, the stent
self-expands.
Inventors: |
Bashiri, Mehran; (San
Carlos, CA) |
Correspondence
Address: |
VIDAS, ARRETT & STEINKRAUS, P.A.
6109 BLUE CIRCLE DRIVE
SUITE 2000
MINNETONKA
MN
55343-9185
US
|
Family ID: |
25481842 |
Appl. No.: |
09/944668 |
Filed: |
August 31, 2001 |
Current U.S.
Class: |
623/1.12 |
Current CPC
Class: |
A61F 2002/91533
20130101; A61F 2/91 20130101; A61F 2002/91558 20130101; A61F
2220/0058 20130101; A61F 2220/005 20130101; A61F 2/915 20130101;
A61F 2250/0071 20130101; A61F 2230/0013 20130101; A61F 2250/0048
20130101 |
Class at
Publication: |
623/1.12 |
International
Class: |
A61F 002/06 |
Claims
1. A stent comprising: a non-woven tubular element having a
plurality of openings therein, the tubular element comprising a
plurality of interconnected members and at least one frangible
restraining member which connects at least two interconnected
members and is disposed between and not about the at least two
interconnected members, at least a portion of the stent constructed
and arranged to self-expand upon breaking of the at least one
frangible restraining member.
2. The stent of claim 1 wherein the portion of the stent which is
constructed and arranged to self-expand upon breaking of the
frangible restraining member is made of a shape-memory
material.
3. The stent of claim 2 wherein the shape memory material is from
the group consisting of shape-memory metals and shape-memory
plastics.
4. The stent of claim 1 wherein the entirety of the stent is
constructed and arranged to self-expand upon breaking of the
frangible restraining member.
5. The stent of claim 1 wherein the plurality of interconnected
members and the at least one frangible restraining member are
constructed from the same material.
6. The stent of claim 1 wherein the at least one frangible
restraining member is constructed from a different material than
the interconnected members.
7. The stent of claim 1 comprising a plurality of frangible
restraining members, each of which extends between at least two
adjacent interconnected members.
8. The stent of claim 7 wherein the frangible restraining members
are selected from at least one member of the group consisting of:
frangible welds, frangible glues, frangible solder, and any
combination thereof.
9. The stent of claim 7 wherein the frangible restraining members
are distributed uniformly throughout the stent.
10. The stent of claim 7 wherein the frangible restraining members
are distributed about at least one end of the stent.
11. The stent of claim 7 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 2
atmospheres without breakage of the frangible restraining
members.
12. The stent of claim 7 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 5
atmospheres without breakage of the frangible restraining
members.
13. The stent of claim 7 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 12
atmospheres without breakage of the frangible restraining
members.
14. The stent of claim 1 wherein the frangible restraining members
includes a circumferential extending component.
15. The stent of claim 1 wherein the frangible restraining member
includes a curved portion.
16. The stent of claim 7 wherein the plurality of frangible
restraining member are arranged to form one or more helical
bands.
17. A stent comprising a generally tubular body of non-woven
elements and at least one frangible restraining member disposed
about at least a portion of the tubular body, the at least one
frangible restraining member made of the same material as the
tubular body, at least a portion of the stent capable of
self-expanding upon breaking of the at least one frangible
restraining member.
18. The stent of claim 17 wherein the generally tubular body and
the at least one frangible restraining member are made of the same
material.
19. The stent of claim 18 wherein the generally tubular body and
the at least one frangible restraining member are made of the same
metals.
20. The stent of claim 17 wherein the generally tubular body and
the at least one frangible restraining member are made of different
materials.
21. The stent of claim 17 wherein the generally tubular body and
the at least one frangible restraining member are made of different
metals.
22. The stent of claim 17 wherein the at least one frangible
restraining member is helical wound about the tubular body.
23. The stent of claim 17 wherein the at least one frangible
restraining member is in the form of a band disposed at least
partially about the circumference of the tubular member.
24. The stent of claim 17 comprising a plurality of frangible
restraining members.
25. The stent of claim 17 wherein the at least one frangible
restraining member is interweaved through the tubular body.
26. The stent of claim 17 where the entirety of the stent is
capable of self-expanding upon breaking of the at least one
frangible restraining member.
27. The stent of claim 17 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 2
atmospheres without breakage of the at least one frangible
restraining member.
28. The stent of claim 17 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 5
atmospheres without breakage of the at least one frangible
restraining member.
29. The stent of claim 17 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 12
atmospheres without breakage of the at least one frangible
restraining member.
30. A stent comprising a generally tubular body and a frangible
restraining member disposed about at least a portion of the tubular
body, at least a portion of the stent capable of self-expanding
upon breaking of the frangible restraining member, the frangible
restraining member at least partially constructed from metal,
plastic or a combination thereof.
31. The stent of claim 30 wherein the frangible restraining member
is helical wound about the tubular body.
32. The stent of claim 30 wherein the frangible restraining member
is in the form of a band disposed about the circumference of the
tubular member.
33. The stent of claim 30 comprising a plurality of frangible
restraining members.
34. The stent of claim 30 where the entirety of the stent is
capable of self-expanding upon breaking of the frangible
restraining member.
35. The stent of claim 30 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 2
atmospheres without breakage of the frangible restraining
member.
36. The stent of claim 30 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 5
atmospheres without breakage of the frangible restraining
member.
37. The stent of claim 30 wherein the stent is capable of
withstanding radially and/or axially outward pressures of up to 12
atmospheres without breakage of the frangible restraining
member.
38. A stent formed of a plurality of interconnected struts, the
interconnected struts including temporary struts and permanent
struts, the temporary struts but not the permanent struts breaking
upon the application of a predetermined radially and/or axially
outward pressure to the stent.
39. The stent of claim 38 wherein the predetermined radially and/or
axially outward pressure is in excess of 2 atmospheres.
40. The stent of claim 38 wherein the predetermined radially and/or
axially outward pressure is in excess of 12 atmospheres.
41. A method of delivering a stent to a desired bodily location
comprising the steps of: (a) providing a catheter with an
expandable member and a stent as in claim 1 disposed thereabout;
(b) inserting the stent and catheter in a bodily vessel and
delivering the stent to the desired bodily location; (c) expanding
the expandable member to break the at least one frangible
restraining member; and thereafter (d) allowing the stent to
self-expand.
42. The method of claim 41 further comprising the step of: (e)
seating the stent into the desired body location.
43. A method of delivering a stent to a desired bodily location
comprising the steps of: (a) providing a catheter with an
expandable member and a stent as in claim 17 disposed thereabout;
(b) inserting the stent and catheter in a bodily vessel and
delivering the stent to the desired bodily location; (c) expanding
the expandable member to break the at least one frangible
restraining member; and thereafter (d) allowing the stent to
self-expand.
44. A method of delivering a stent to a desired bodily location
comprising the steps of: (a) providing a catheter with an
expandable member and a stent as in claim 30 disposed thereabout;
(b) inserting the stent and catheter in a bodily vessel and
delivering the stent to the desired bodily location; (c) expanding
the expandable member to break the at least one frangible
restraining member; and thereafter (d) allowing the stent to
self-expand.
45. A method of delivering a stent to a desired bodily location
comprising the steps of: (a) providing a catheter with an
expandable member and a stent as in claim 38 disposed thereabout;
(b) inserting the stent and catheter in a bodily vessel and
delivering the stent to the desired bodily location; (c) expanding
the expandable member to break the at least one frangible
restraining member; and thereafter (d) allowing the stent to
self-expand.
Description
BACKGROUND OF THE INVENTION
[0001] The use of endoprostheses such as stents, stent-grafts and
grafts is well known in maintaining the patency of bodily vessels
including blood vessels and biliary ducts. When the term `stent` is
used herein, it is to be understood in a general sense as including
all such expandable prostheses, unless otherwise indicated.
Typically, a stent is implanted in a vessel which has been
occluded, which is subject to an aneurysm, which has a lesion
present or is otherwise damaged. Often, during the implantation of
the stent, the vessel will suffer from trauma. The trauma may be as
a result of the dilation prior to the implantation of the stent,
the presence of a foreign body (the stent) in the bodily vessel or
as a result of other causes. Although it is desirable to maintain
the vessel at as large a diameter as possible to minimize the
possibility of restenosis, the weakening of the vessel resulting
from trauma may limit the extent to which the vessel can be
dilated.
[0002] The endoprostheses that are currently available include
mechanically expandable stents such as balloon expandable stents,
and self-expanding devices. Mechanically expandable stents are
typically expanded to a desired diameter by a radially outward
force to the stent with an expansion device such as a balloon.
Balloon expanded stents typically are incapable of further
expansion unless a balloon is reinserted in the stent and expanded.
Self-expanding stents are typically made of a shape memory material
or a resilient material such as spring steel. The stent is
typically constrained by a sheath or other containing device which
adds to the profile of the delivery catheter. Upon removal of the
sheath the stent self-expands. Self-expanding stents continually
exert an outward force as they try to attain their maximum possible
diameter. "Hybrid" endoprostheses which have aspects of a balloon
expandable stent as well as aspects of a self-expanding stent are
known. An example of a hybrid stent is described in U.S. Pat. No.
6,168,621 B1 to Vrba. Self-expanding stents which are temporarily
restrained from self-expanding are also known. An example of a
self-expanding stent which is restrained from self-expanding by a
coating is disclosed in U.S. Pat. No. 5,899,935. An example of a
stent which is restrained from self-expanding by restraining bands
which are constructed to fail is disclosed in WO 00/41649.
[0003] It would be desirable to provide an endoprosthesis which has
some of the characteristics of balloon expandable stents prior to
deployment thereby allowing the stent to be useable with a
relatively low profile balloon catheter, but which is also capable
of self-expanding following an initial balloon expansion of the
stent. It is further desirable to provide an endoprosthesis which
is temporarily restrained from self-expanding, which does not rely
on the use of a coating for such a restraint. It is also desirable
to provide an endoprosthesis requiring a force in excess of that
which the endoprosthesis experiences in the body in order to break
the restraining members.
[0004] The entire content of all U.S. and foreign patents, patent
applications and publications listed herein are incorporated herein
by reference.
[0005] The invention in various of its embodiment is summarized
below. Additional details of the invention and/or additional
embodiments of the invention may be found in the Detailed
Description of the Invention below.
BRIEF SUMMARY OF THE INVENTION
[0006] In one embodiment, the invention is directed to a stent
comprising a non-woven tubular element having a plurality of
interconnected members and at least one frangible restraining
member which connects at least two interconnected members and is
disposed between and not about the at least two interconnected
members. Alternatively, one or more frangible restraining member
may form one or more of the interconnected members or a portion
thereof.
[0007] At least a portion and, optionally, the entirety of the
stent is constructed and arranged to self-expand upon breaking of
the frangible restraining member. The tubular element has a
plurality of openings therein. Typically, the portion of the stent
which is constructed and arranged to self-expand upon breaking of
the frangible restraining member is made of a shape-memory
material. The plurality of interconnected members and the at least
one frangible restraining member may be constructed of the same
material or of different materials.
[0008] The frangible restraining members may be provided in a
variety of forms including in the form of frangible welds and in
the form of temporary struts. The frangible restraining members may
be straight, may include one or more straight portions, may be
curved or may include one or more curved portions. They may be
distributed helically about the stent, circumferentially about the
stent, or longitudinally along the stent. Also, the frangible
restraining members may be distributed uniformly throughout the
stent or non-uniformly.
[0009] In another embodiment, the invention is directed to a stent
comprising a generally tubular body and one or more frangible
restraining members disposed about at least a portion of the
tubular body. The frangible restraining member is made of the same
material as the tubular body. At least a portion of the stent is
capable of self-expanding upon breaking of the frangible
restraining member. The generally tubular body and the frangible
restraining member may be made of the same metal or polymeric
material. The generally tubular body and/or the frangible members
may be constructed from a material or materials having super
elastic properties.
[0010] In yet another embodiment, the invention is directed to a
stent comprising a generally tubular body and a metal frangible
restraining member disposed about at least a portion of the tubular
body. At least a portion of the stent is capable of self-expanding
upon breaking of the frangible restraining member.
[0011] In those embodiments of the invention where the frangible
restraining member is disposed about at least a portion of the
generally tubular body, the frangible restraining member may be
disposed helically about the tubular body, may be in the form of a
band disposed about the circumference of the tubular member, may be
in the form of longitudinal members or may be in any other suitable
arrangement. The frangible restraining member may be interwoven
through the tubular body or may be partially or entirely embedded
therein.
[0012] In accordance with the invention, any of the inventive
stents disclosed herein may be provided in embodiments in which
only a portion of the stent is capable of self-expanding upon
breaking of the frangible restraining member and in embodiments in
which the entirety of the stent is capable of self-expanding upon
breaking of the frangible restraining member.
[0013] Desirably, the inventive stents disclosed herein are capable
of withstanding radially outward pressures of up to about 2
atmospheres or the equivalent force, more desirably, up to about 5
atmospheres or the equivalent force and most desirably, up to about
12 atmospheres or the equivalent force without breakage of the
frangible restraining members.
[0014] The invention is also directed to a stent formed of a
plurality of interconnected struts, the interconnected struts
including temporary struts and permanent struts, where the
temporary struts but not the permanent struts break upon the
application of a predetermined radially and/or axially outward
pressure to the stent.
[0015] The invention is also directed to methods of delivering a
stent to a desired bodily location. In accordance with the
inventive methods, a catheter with an expandable member such as a
balloon is provided with any of the inventive stents disclosed
herein disposed about the expandable member. The catheter is
inserted in a bodily vessel and delivered to the desired bodily
location. The expandable member is then expanded to break the
frangible restraining member(s). Where the expandable member is in
the form of a balloon, an inflation fluid is delivered to the
balloon to expand it. Thereafter, the stent is allowed to
self-expand. Subsequent to self-expansion of the stent a balloon or
other device may be used to seat the stent into place at the
desired location.
[0016] In some embodiments of the invention the stent may be
constructed to achieve a memorized shape after the frangible
members have been broken by applying energy, such as for example,
heat, to cause the stent to expand and/or contact to the memorized
shape.
[0017] Additional details and/or embodiments of the invention are
discussed below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] A detailed description of the invention is hereafter
described with specific reference being made to the drawings.
[0019] FIG. 1 is a side view of an embodiment of the invention in a
reduced configuration mounted upon a balloon catheter.
[0020] FIG. 2 is a side view of the embodiment of the invention
shown in FIG. 1, following partial balloon expansion, some of the
frangible restraining members having been broken.
[0021] FIG. 3 is a side view of the embodiment shown in FIG. 1
immediately prior to self-expansion, all the of the frangible
restraining members having been broken.
[0022] FIG. 4 is a side view of the stent shown in FIG. 1 following
self-expansion of the stent.
[0023] FIG. 5 is a side view of an alternative embodiment of the
invention.
[0024] FIG. 6 is a side view of an alternative embodiment of the
invention.
[0025] FIG. 7 is a perspective view of an alternative embodiment of
the invention.
[0026] FIG. 8 is a perspective view of the embodiment shown in FIG.
7, shown subsequent to mechanical expansion of the stent.
[0027] FIG. 9 is a cross-sectional view of an inventive stent prior
with the frangible retaining members intact.
[0028] FIG. 10 is a cross-sectional view of the stent of FIG. 9
following expansion of the stent and breakage of the frangible
retaining members.
[0029] FIG. 11 is a schematic illustration of a stent comprising
frangible restraining members disposed about the tubular body of
the stent.
[0030] FIG. 12 is a schematic illustration of the stent of FIG. 11
following breakage of the frangible restraining members.
[0031] FIG. 13 is a schematic illustration of a stent comprising
temporary struts in a serpentine portion of the stent.
DETAILED DESCRIPTION OF THE INVENTION
[0032] While this invention may be embodied in many different
forms, there are described in detail herein specific preferred
embodiments of the invention. This description is an
exemplification of the principles of the invention and is not
intended to limit the invention to the particular embodiments
illustrated.
[0033] For the purposes of this disclosure, like reference numerals
in the figures shall refer to like features unless otherwise
indicated.
[0034] The present invention, in one embodiment, is directed to a
stent which includes features of a balloon expandable stent as well
as features of a self-expanding stent. At least a portion of the
stent is capable of self-expansion but is restrained via one or
more frangible restraining members. The frangible restraining
members are designed to be able to withstand the forces associated
with delivery of the stent through tortuous bodily vessels and yet
break when a sufficient radially and/or axially outward force is
applied to the stent. Desirably, the stent is delivered on a
balloon based stent delivery catheter and the frangible restraining
members broken upon expansion of the balloon or other application
of force. Thereafter, the stent may expand to a predetermined
shape.
[0035] Turning to the figures, in one embodiment, as shown in FIGS.
1-3, the present invention is directed to stent which includes a
self-expanding tubular member 110 having a plurality of openings
111 therein and having a plurality of interconnected members 112.
Interconnected members 112 intersect with one another but do not
cross one another as is the case with braided stents. The stent
further includes members 114 which are structurally weaker than
other nearby members 112. These weaker members are hereinafter
referred to as frangible restraining members 114. Frangible
restraining members 114 prevent the stent from self-expanding. When
frangible restraining members 114 are broken, the stent may
self-expand.
[0036] The frangible restraining members 114 may be in the form of
frangible welds between two or more adjacent interconnecting
members 112, or may be in the form of struts which have been
weakened in some manner, such as by laser etching, chemical
treatment, or abrading. The interconnected members 112 and the
frangible restraining members 114 may be constructed of the same or
different materials.
[0037] Each frangible restraining member 114 includes two ends 116
and one or more relatively weak portions 120. Each end 116 is
connected to an interconnected member 112. Frangible restraining
members 114 must be strong enough to withstand any frictional
forces associated with delivery of the stent and any other forces
experienced by the stent during delivery of the stent through the
tortuous vessels of the body. The weak region 120 is designed to
fail when the stent is expanded, via balloon expansion or other
expansion means. Desirably, the stent is capable of withstanding
radially and/or axially outward pressures of up to 2 atmospheres,
or the equivalent force, more desirably, up to 5 atmospheres or the
equivalent force and most desirably, up to 12 atmospheres or the
equivalent force or more without breakage of the frangible
restraining members. In one embodiment of the invention, an
inflation pressure of at least 20 atmospheres or the equivalent
force is required to break the frangible restraining members.
[0038] When stent 110 is initially subjected to an outward force,
such at that supplied by balloon 122 of balloon catheter 124 as
shown in FIG. 2, or by any other suitable expanding members,
interconnecting members 112 reorient relative to one another to
accommodate expansion of the stent. As part of the reorientation,
the spacing between those interconnected members 112 which are also
connected by a frangible restraining member 114 increases, thereby
placing the frangible restraining member in tension. and breaking
at least some of the frangible restraining members. In FIG. 2, the
stent 110 is shown just prior to being fully balloon expanded and
not all of the frangible members have been broken.
[0039] In FIG. 3, stent 110 is shown fully balloon expanded. All of
the frangible restraining members 114 have broken apart and the
stent is free to self-expand. In FIG. 4, stent 110 is shown having
self-expanded to its fully expanded state. Stent 110 is capable of
self-expanding as a result of the tubular member being constructed
in whole, or in part, from super elastic materials.
[0040] The term "super elastic" or "superelasticity" is used to
describe the property of certain shape memory alloys to return to
their original shape upon unloading after a substantially
deformation while in their austenitic state. Super elastic alloys
can be strained while in their austenitic state more than ordinary
spring materials without being plastically deformed. This unusually
large elasticity in the austenitic state is also called
pseudoelasticity, because the mechanism is nonconventional in
nature, or transformational superelasticity because it is caused by
a stress induced phase transformation. Alloys that show
superelasticity also undergo a thermoelastic martensitic
transformation which is also the prerequisite for the shape memory
effect. Superelasticity and shape memory effect are therefore
closely related. Superelasticity can even be considered part of the
shape memory effect.
[0041] The shape memory and superelasticity effect are particularly
pronounced in Ni--Ti alloys and is know in other materials as well.
Suitable materials include shape memory metals such as nitinol and
shape memory polymers such as those disclosed in U.S. Pat. No.
5,954,744. Any super elastic material however, may be suitable for
use in constructing the stent 110 and/or components thereof.
[0042] In certain embodiments of the invention, following
self-expansion of the stent, portions or the entirety of the stent
may be further expanded via the use of a balloon or other expansion
member to seat the stent in the vessel. Alternatively, the stent
may be provided with a memorized shape which may be attained
through the application of energy, such as by applying heat
transmitted by the delivery catheter. The ability of a stent or
other implantable medical device to achieve such a memorized state
is described in U.S. application Ser. No. 09/172,590, filed Oct.
14, 1998, the entire content of which is incorporated herein by
reference.
[0043] Frangible restraining members 114 may be made of the same or
different material as the tubular member itself. Where the tubular
member is made of metal, frangible restraining members 114 may be
made of the same metal as the stent or of different metals or
materials. Exemplary choices of materials for the frangible
restraining member include nitinol, stainless steel, platinum or
tantalum. Alternatively, the frangible members 114 may be made of
any metal and/or plastic material which may be characterized as
soft and breakable. The frangible member 114 may be secured to the
connecting members via the use of adhesives or any other suitable
attachment method. Desirably, the frangible restraining member is
weakened via chemical etching, laser etching or abrading in or more
locations so that the restraining member is rendered frangible upon
application of a desired force to the stent. The stent including
the frangible members may also be integrally formed with the
tubular member by cutting the stent pattern into a sheet of
material and rolling the sheet to form a tube. Opposing edges of
the tube may then be joined together if desired or the stent may be
provided in the form of a rolled sheet stent which may expand by at
least partially unrolling. An example of a rolled sheet stent is
disclosed in WO 01/01885. The stent including the frangible members
may also be integrally formed with the tubular member by cutting
the stent pattern including the frangible members into a tube.
[0044] Where the stent is made of polymeric material, the frangible
restraining member(s) will be made of the same material as the
tubular member and may be secured thereto via welding, the use of
adhesives or any other suitable attachment method. Desirably, the
restraining member is weakened via chemical etching, laser etching
or abrading in or more locations so that the restraining member is
rendered frangible upon application of a desired force to the
stent.
[0045] The frangible restraining member may be thinned in one or
more regions or the width of the frangible restraining member may
be reduced in one or more regions to render the restraining member
frangible. The restraining member may also be perforated in one or
more regions or may have one notches therein. The extent to which
the restraining member must be weakened will determine, in part,
the threshold force which is required to break the frangible
restraining member. The frangible restraining member is designed
such that a force in excess of the forces experienced by a stent
following implantation in the body must be applied to it for it to
break.
[0046] In accordance with the invention, frangible restraining
members 114 may be distributed throughout the stent 100 in a
variety of different configurations. In the embodiment shown in
FIG. 5 for example, the frangible restraining members 114 are
distributed intermittently about the circumference of the stent 110
in a substantially wavy pattern. In FIG. 6, the frangible
restraining members 114 are distributed helically about stent 100
as shown at 130. The frangible restraining members may also be
arranged circumferentially about the stent or lengthwise along the
stent. Other distributions of restraining members are possible as
well and are considered as being included in the scope of the
present invention.
[0047] Tubular member 110 which forms a portion of the inventive
stents may be of any suitable design including those designs shown
in WO 96/26689, WO 01/01888, WO 99/44543, U.S. Pat. Nos. 5,733,303,
6,231,599, and 6,042,597. Any other design may also be used.
[0048] In FIG. 7, a stent of the type described in WO 96/26689 is
shown in an unexpanded state. Stent 100 includes a plurality of
serpentine sections 115 made up of members 112. Adjacent serpentine
sections are joined by connectors 117. Connectors 117 extend at an
angle relative to the longitudinal axis of the stent. More
generally, the stent may comprise one or more connectors between
adjacent segments. The connectors may be straight or may include
one or more curved portions. The ends of the each connectors may be
longitudinally and/or circumferentially offset from one
another.
[0049] The stent includes serpentine sections 115a with frangible
restraining members 114a that extend between adjacent members 112
in the serpentine section. The stent may be comprised exclusively
of sections such as serpentine section 115a or may further comprise
serpentine section which lack frangible restraining members.
[0050] Further in accordance with the invention, adjacent
serpentine sections may further be connected by one or more
frangible restraining members 114b. The stent may also be provided
in an embodiment in which the only frangible restraining members
present are restraining members 114b which extend between adjacent
serpentine segments.
[0051] In FIG. 8, frangible restraining members 114 have been
broken as a result of mechanical expansion of the stent 110.
[0052] Desirably, when frangible restraining members 114 break,
they either extend inward toward the flow passage of the stent or
they remain within the tubular envelope of the stent. In one
embodiment of the invention, as shown in FIG. 9, frangible
restraining members 114 are in the form of thin connectors
extending between adjacent struts or members 112 of the stent. The
restraining members 114 have a relatively weak portion 120 where
the connector is thinned out. Following balloon expansion of the
stent, as shown in FIG. 10, restraining members 114 have broken,
and the ends 116 of each restraining member 114 extend from struts
or members 112. Ends 116 remain within the envelope defined by
inner surface 121 and outer surface 123 of the stent with ends 116
extending neither into the flow passage of the stent nor outside of
the tubular wall of the stent.
[0053] In another embodiment, the invention is directed to a stent,
at least a portion of which is self-expanding and which is
restrained from self-expanding by one or more frangible restraining
members made of the same material as the stent and which are
disposed about or interspersed with the tubular surface of the
stent.. The frangible restraining member is designed such that a
force in excess of the forces experienced by a stent following
implantation in the body must be applied to it for it to break. As
shown in FIG. 10, stent 110, includes restraining member 114
helically disposed about the tubular body of the stent. When
sufficient outward force is applied to the stent, frangible
restraining member 114 will break and allow the self-expanding
portion of the stent to self-expand.
[0054] In addition to the helical configuration of the frangible
restraining member shown in FIG. 10, the frangible restraining
member may be provided in other configurations as well. For
example, the frangible restraining member may be in the form of one
or more bands which extend about a portion or the entirety of the
circumference of the stent or which weave in and out of a portion
or the entirety the circumference of the stent. The frangible
restraining member may also be provided in the form of one or more
longitudinal strips which prevent the stent from self-expanding.
The frangible restraining members may also be provided in the form
of one or more restraining members which are secured to the tubular
surface of the stent and secure adjacent struts one to the
other.
[0055] In yet another embodiment of the invention, as shown in FIG.
11, the invention is directed to a metal stent, shown generally at
100, comprising a metal tubular member 110, at least a portion of
which is self-expanding and which is restrained from self-expanding
by one or more metal frangible restraining members 114 which are
disposed about or interspersed with the tubular member. In the
embodiment of FIG. 11, frangible restraining member 114 is entirely
disposed about the tubular member. The restraining member may also
be provided in an arrangement in which it is disposed about
portions of the tubular member and intertwined with other portions
of the tubular member.
[0056] The frangible restraining member 114 may be helically
disposed about the tubular as shown in FIG. 11 or may be provided
in the form of one or more circumferential bands disposed about the
circumference of the tubular member. The frangible restraining
members may also be provided in the form of loops which tie
together adjacent struts or connecting members of the tubular.
Examples of such configurations may be found in WO 00/41649.
[0057] Frangible restraining members 114 may be made of the same
metal as the stent or may be made of a different metal than the
stent. The frangible restraining member may be secured to the stent
via welding, adhesively or via any other suitable method.
[0058] Tubular member 110 may be provided with any suitable
configuration including any of the designs disclosed herein or
disclosed in the patents, patent applications and publications
referred to herein. Furthermore, tubular member 110 may be made of
any biocompatible metal including those metals disclosed herein or
disclosed in the patents, patent applications and publications
referred to herein.
[0059] Stent 100 may be expanded to break the frangible members, as
shown in FIG. 12. Stent 100 thereafter may self-expand.
[0060] The invention is also directed to a stent comprising a
generally tubular body and one or more frangible restraining
members disposed about at least a portion of the tubular body. The
frangible restraining member is made of the same material as the
tubular body. At least a portion of the stent is capable of
self-expanding upon breaking of the frangible restraining member.
The generally tubular body and the frangible restraining member may
be made of the same metal or of the same polymeric material. The
generally tubular body and the frangible restraining member may
also be made partially of metal and partially of polymer. Any
biocompatible metals and polymers suitable for use in a stent may
be used including stainless steel, nitinol, tantalum and platinum.
Suitable polymers include PTFE, and other polymers commonly used
for grafts such as polyesters and nylons. Metals and polymers other
than those disclosed herein may also be used in the practice of the
invention.
[0061] The invention is also directed to a stent formed of a
plurality of interconnected struts, the interconnected struts
including temporary struts and permanent struts, where the
temporary struts but not the permanent struts break upon the
application of a predetermined radially and/or axially outward
pressure to the stent. The stent may be made of any of the
materials disclosed herein or of any other suitable stent material.
The stent may be provided in any of the configurations disclosed
herein or in any of the configurations disclosed in the patents,
patent applications and publications disclosed herein or in any
other suitable configuration. The temporary struts may be provided
in the form of frangible restraining members as shown in FIGS.
1-10. The invention also contemplates replacing at least some of
the permanent struts in known stent configurations with temporary
struts. An example of this is shown in FIG. 13 where at least some
of the serpentine segments 115 include temporary struts 114. The
temporary struts may be arranged for a variety of purposes
including for providing improved side branch access. Following
breakage of the temporary struts, the stent may self-expand or may
require additional balloon expansion.
[0062] Any of the stents disclosed herein may be provided in
embodiments in which the entirety of the stent is self-expanding or
in which only portions of the stent are expanding. As an example of
the latter, the stent may be in the form of a bifurcated stent such
that disclosed in U.S. Pat. No. 6,168,621 where the self-expanding
portions have been modified in accordance with the present
invention. Thus, an inventive bifurcated stent may have a
self-expanding trunk portion which is restrained with frangible
restraining members in accordance with the present invention and/or
one or more self-expanding leg portions which are restrained by
frangible restraining members as disclosed herein. where the stent
has a single flow passage, a portion of the length of the stent may
be self-expanding with frangible restraining members and another
portion may be non-self-expanding.
[0063] The expansion properties of any of the inventive stents
disclosed herein may be modified by providing a plurality of
frangible retaining members which are of different strengths. Thus,
one set of frangible members may be designed to break upon
application of a first pressure to the stent and another set of
frangible members which break upon the application of a second
pressure different from the first pressure may be provided. Two,
three, four or more different strength frangible members may be
provided in any of the inventive stents disclosed herein. Where it
is desirably to expand the first and/seconds end of the stent prior
to the remainder of the stent, the first and/or second ends may be
provided with weaker frangible members than the remainder of the
stent. Where it is desirable to expand the central portion of the
stent first, the weaker frangible members may be provided in the
center of the stent. A similar effect may be achieved by varying
the number of frangible members along the length of the stent.
Weaker regions of the stent will have fewer frangible members than
stronger portions of the stent.
[0064] The inventive stents disclosed herein may be used by
themselves or as the framework for a graft. They may be for a
variety of medical purposes in the body including in the coronary
arteries, the peripheral arteries, arteries of the neck, cerebral
arteries, veins, biliary ducts, urethras, ureters, fallopian tubes,
bronchial tubes, the trachea, the esophagus and the prostate.
Stents are typically placed or implanted within a bodily vessel,
for example, for treating stenoses, strictures or aneurysms
therein. They are implanted to reinforce collapsing, partially
occluded, weakened, or dilated sections of a blood vessel. In such
embodiments the frangible member(s) 114 may be imbedded into the
wall of the stent/graft. The stent may act as one or more segments
which provide expansion force, when the frangible member(s) are
broken. In such embodiments the segments may be comprised of a
super elastic material such as a Nitinol alloy.
[0065] The invention is also directed to methods of delivering a
stent to a desired bodily location. In accordance with the
inventive methods, a catheter with an expandable member such as a
balloon is provided with any of the inventive stents disclosed
herein disposed about the expandable member. The catheter is
inserted in a bodily vessel and delivered to the desired bodily
location. The expandable member is then expanded to break the
frangible restraining member(s). Where the expandable member is in
the form of a balloon, an inflation fluid is delivered to the
balloon to expand it. Thereafter, the stent is allowed to
self-expand.
[0066] The above disclosure is intended to be illustrative and not
exhaustive. This description will suggest many variations and
alternatives to one of ordinary skill in this art. All these
alternatives and variations are intended to be included within the
scope of the claims where the term "comprising" means "including,
but not limited to". Those familiar with the art may recognize
other equivalents to the specific embodiments described herein
which equivalents are also intended to be encompassed by the
claims.
[0067] Further, the particular features presented in the dependent
claims can be combined with each other in other manners within the
scope of the invention such that the invention should be recognized
as also specifically directed to other embodiments having any other
possible combination of the features of the dependent claims. For
instance, for purposes of claim publication, any dependent claim
which follows should be taken as alternatively written in a
multiple dependent form from all prior claims which possess all
antecedents referenced in such dependent claim if such multiple
dependent format is an accepted format within the jurisdiction
(e.g. each claim depending directly from claim 1 should be
alternatively taken as depending from all previous claims). In
jurisdictions where multiple dependent claim formats are
restricted, the following dependent claims should each be also
taken as alternatively written in each singly dependent claim
format which creates a dependency from a prior
antecedent-possessing claim other than the specific claim listed in
such dependent claim below (e.g. claim 4 may be taken as
alternatively dependent from claim 2 or claim 3; claim 5 may be
taken as alternatively dependent on claims 2, 3, 4 or 5; etc.).
[0068] This completes the description of the preferred and
alternate embodiments of the invention. Those skilled in the art
may recognize other equivalents to the specific embodiment
described herein which equivalents are intended to be encompassed
by the claims attached hereto.
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