U.S. patent application number 10/180706 was filed with the patent office on 2004-01-01 for sacrificial anode stent system.
This patent application is currently assigned to SCIMED LIFE SYSTEMS, INC.. Invention is credited to Gerberding, Brent C., Griffin, Stephen.
Application Number | 20040002752 10/180706 |
Document ID | / |
Family ID | 29778980 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040002752 |
Kind Code |
A1 |
Griffin, Stephen ; et
al. |
January 1, 2004 |
Sacrificial anode stent system
Abstract
A sacrificial anode stent system comprises a stent having at
least one sacrificial anode portion and a vaso-occlusive device.
The vaso-occlusive device has at least one portion with a potential
different from that of the sacrificial anode portion of the
stent.
Inventors: |
Griffin, Stephen;
(Sunnyvale, CA) ; Gerberding, Brent C.;
(Sunnyvale, CA) |
Correspondence
Address: |
VIDAS, ARRETT & STEINKRAUS, P.A.
6109 BLUE CIRCLE DRIVE
SUITE 2000
MINNETONKA
MN
55343-9185
US
|
Assignee: |
SCIMED LIFE SYSTEMS, INC.
Maple Grove
MN
|
Family ID: |
29778980 |
Appl. No.: |
10/180706 |
Filed: |
June 26, 2002 |
Current U.S.
Class: |
623/1.15 |
Current CPC
Class: |
A61F 2002/823 20130101;
A61F 2220/0058 20130101; A61F 2/915 20130101; A61F 2002/91558
20130101; A61F 2/91 20130101; A61F 2250/0098 20130101; A61F
2002/3008 20130101; A61F 2250/0054 20130101; A61B 17/1214 20130101;
A61B 2017/12063 20130101; A61B 17/12022 20130101; A61B 17/12036
20130101; A61B 17/12118 20130101; A61F 2002/91541 20130101; A61F
2220/005 20130101; Y10S 623/903 20130101; A61F 2220/0041
20130101 |
Class at
Publication: |
623/1.15 |
International
Class: |
A61F 002/06 |
Claims
1. A sacrificial anode stent system comprising: a) a stent having
at least one sacrificial anode portion and b) a vaso-occlusive
device, the vaso-occlusive device having at least one portion with
a potential different from that of the sacrificial anode portion of
the stent.
2. The sacrificial anode stent system of claim 1 wherein said
sacrificial anode portion is at a proximal or distal end of the
stent.
3. The sacrificial anode stent system of claim 1 further comprising
a plurality of sacrificial anode portions.
4. The sacrificial anode stent system of claim 1 comprising a
plurality of sacrificial anode portions wherein said sacrificial
anode portions are at a proximal and/or distal end of the
stent.
5. The sacrificial anode stent system of claim 1 comprising a
plurality of sacrificial anode portions, the sacrificial anode
portions provided in the form of tabs extending from or both ends
of the stent.
6. The sacrificial anode stent system of claim 1 wherein the stent
further comprises radiopaque portions.
7. The sacrificial anode stent system of claim 6 comprising a
plurality of sacrificial anode portions, the sacrificial anode
portions and the radiopaque portions provided in the form of tabs
extending from or both ends of the stent.
8. The sacrificial anode stent system of claim 1 wherein the
vaso-occlusive device is in the form of a coil.
9. The sacrificial anode stent system of claim 1 wherein the
vaso-occlusive device is in the form of a GDC coil.
10. The medical device of claim 8 wherein the coil includes
platinum and the non-sacrificial portion of the stent includes
stainless steel.
11. The medical device of claim 10 wherein the sacrificial portion
is selected from the group consisting of magnesium, zinc, aluminum,
mild steel, low alloy steel, and iron or any combination
thereof.
12. A sacrificial anode stent system comprising: a) a stent and b)
a medical device, the stent and the medical device each having at
least one metal portion, the metal portion of the stent having a
potential different from that of the medical device, wherein one of
the stent and the medical device includes a sacrificial portion of
a different potential from that of the remainder of the stent or
medical device, the potential of the sacrificial portion such that
corrosion occurs preferentially at the sacrificial portion.
13. The sacrificial anode stent system of claim 12 wherein the
medical device is a coil and the sacrificial portion is part of the
stent.
14. The sacrificial anode stent system of claim 13 wherein the coil
includes platinum and the non-sacrificial portion of the stent
includes stainless steel.
15. The sacrificial anode stent system of claim 14 wherein the
sacrificial portion is selected from the group consisting of
magnesium, zinc, aluminum, mild steel, low alloy steel, and iron or
any combination thereof.
16. A stent including at least one sacrificial anode portion.
17. The stent of claim 16, wherein said sacrificial anode portion
is connected to said stent proximate to said proximal end.
18. The stent of claim 16, wherein said sacrificial anode portion
is connected to said stent proximate to said distal end.
19. The stent of claim 16, further comprising a plurality of
sacrificial anode portions connected to said stent.
20. The stent of claim 19, wherein said sacrificial anode portions
are connected to said stent proximate to said proximal end.
21. The stent of claim 19, wherein said sacrificial anode portions
are connected to said stent proximate to said distal end.
22. The stent of claim 16, wherein or more regions of the stent are
radiopaque.
23. The stent of claim 16 wherein the sacrificial anode portions
are characterized by a higher potential than that of the remainder
of the stent.
24. The stent of claim 16 wherein the sacrificial anode portion is
in the form of one or more tabs extending from a proximal or distal
end of the stent.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to implantable
devices and methods for the non-invasive treatment of vascular
defects such as an aneurysm.
BACKGROUND OF THE INVENTION
[0002] An aneurysm may generally be described as a weakening in the
wall of an artery or vein resulting in a bulge or bubble protruding
in a radial direction relative to the adjacent vessel wall.
[0003] In the past, aneurysms have been treated through a procedure
which surgically clips an aneurysm shut with a metal clip.
Alternatively, the neck of the aneurysm may be clipped followed by
a suture ligation of the neck of the aneurysm or the wrapping of
the entire aneurysm. Each of these surgical procedures constitutes
an intrusive invasion into the body for which certain areas of the
body such as the brain have little tolerance. An aneurysm left
untreated may rupture and hemorrhage resulting in a hemorrhagic
stroke.
[0004] In the past, it has been very difficult to treat a patient
having a high risk wide-neck brain aneurysm condition. In the past,
a surgical procedure to treat a brain aneurysm generally involved
opening the skull and the clipping of the aneurysm shut. Surgical
treatments available for a brain aneurysm are frequently quite
limited. In addition, brain aneurysms may be located within areas
of the brain where surgical procedures will likely result in severe
complications for a patient. It is therefore desirable to provide
the least intrusive procedure available for treatment of a brain
aneurysm which utilizes the manipulation of a catheter into the
aneurysm site for occluding the aneurysm without the necessity for
surgery. In the past, balloons have been used to occlude an
aneurysm site or sack. A problem with the use of balloons is the
risk of over-inflation which may result in the rupture of the
aneurysm.
[0005] Generally, a non-intrusive treatment of an aneurysm site
involves the blockage of blood flow to the aneurysm. Devices which
may be referred to as vaso-occlusive devices are commonly deployed
to the aneurysm site through the use of a catheter delivery
apparatus or introducer. One example of an implantable
vaso-occlusive device is a wire coil identified as a Guglielmi
electrolytically detachable coil (GDC coil) which may be formed of
platinum and/or nickel-titanium alloy. Devices of this nature may
be found in U.S. Pat. No. 4,994,069; 6,059,779; 5,643,254;
5,423,829; 6,024,754; and 5,522,822 for example.
[0006] A Platinum coil may be delivered to a treatment site by a
catheter or introducer. Following release of the coil from the
catheter, the coil may assume a randomly shaped mass which
substantially fills the body lumen and/or aneurysm. The coil may
also be coated with fibers or include a braided fibrous element to
promote clotting of the blood flow proximate to the treatment
site.
[0007] Alternatively, the coil may typically be formed of a
platinum/tungsten alloy coil. The coils may be formed of wire
having a diameter of 2 to 30 mils and is preferably flexible and
soft to minimize risk of herniation of an aneurysm to be
treated.
[0008] Generally, following the placement of a coil within an
aneurysm a thrombus forms in the aneurysm and is followed by a
collagenous material reducing the risk of aneurysm rupture.
[0009] Alternatively, a predominately platinum coil may be placed
within a wide-neck aneurysm where the coil may be severed from the
insertion catheter by the application of a desired and relatively
small level of electrical current. In this embodiment, the coil is
engaged to a guidewire through an electrolytically detachable
and/or dissolvable joint. Upon exposure to the small level of
current the electrolytically dissolvable joint corrodes and fails
separating the platinum coil from the delivery catheter. The
guidewire and/or catheter is preferably formed of a steel material
and therefore functions as an anode when exposed to electrical
current. The coil is generally an effective cathode when in
electric contact with most metals to facilitate galvanic
electrolysis at the location of the dissolvable joint.
[0010] A potential complication to be addressed during the
non-intrusive treatment of a wide-neck aneurysm is the prevention
of migration of a coil from the interior of the aneurysm and into a
parent vessel. A need therefore exists for a stent to be positioned
adjacent to the neck of an aneurysm where the stent functions to
block the coil from migration out of a vessel defect. In addition,
a need also exists for a stent which may remain in contact with any
size of platinum coil or platinum coil mass for prevention of
migration while the stent simultaneously is immune from
electrolytic corrosion.
[0011] A need therefore exists for a sacrificial anode stent system
which partially occludes a wide-neck aneurysm while simultaneously
stenting a blood vessel adjacent to an aneurysm which is
susceptible to herniation and/or rupture. Further, a need exists
for a sacrificial anode stent system which facilitates the
retention of an implant such as a platinum coil within the interior
of the wide-neck aneurysm to occlude a desired portion of a body
lumen.
BRIEF DESCRIPTION OF THE INVENTION
[0012] The sacrificial anode stent system generally includes a
vaso-occlusive device for use during interventional therapy and
vascular surgery where the sacrificial anode stent system is
adapted to be inserted into a portion of a vasculature for
treatment of a body vessel such as an aneurysm. The vaso-occlusive
device of the present invention is generally employed in
combination with a support structure such as a stent, stent-graft,
graft, and the like, all of which will henceforth be referred to by
the term `stent`. The vaso-occlusive device is designed in such
away that it may be readily anchored at the site of the vascular
defect in combination with the support structure to minimize the
migration of the device from a desired location. The support
structure generally includes designated sacrificial anode portions
utilized to minimize support structure degradation or corrosion
during electrolytic detachment of the vaso-occlusive device from a
delivery apparatus such as a catheter or introducer and thereafter
when the device and the stent reside in the body.
[0013] The vaso-occlusive device of the present invention may
include an occlusive member such as a platinum coil for positioning
within a wide-neck aneurysm.
[0014] The support structure of the present invention may include a
member having a first unexpanded configuration and a second
expanded configuration, such as a stent or the like, which assists
in the prevention of migration of the vaso-occlusive device from
the site of the vascular defect while simultaneously stenting a
diseased blood vessel.
[0015] Generally, the vaso-occlusive device is prevented from
migration from a vascular defect due to the positioning of
undulating bands of the stent or the wall structure of the stent in
general across the neck of a vascular aneurysm.
[0016] The vaso-occlusive device may be positioned within a
vascular defect such as an aneurysm by insertion of a catheter
and/or guidewire, the device traversing through an opening in the
sidewall of the stent.
[0017] The fluid flow-occluding device is generally formed of metal
materials which may be platinum based for use as a cathode within
in an electrolytic occluding device separation procedure.
[0018] The support structure may be formed of a variety of
materials including but not necessarily limited to flexible
polymeric materials and metallic materials which may embody shape
memory materials, super elastic materials, as well as other
materials which are bio compatible.
[0019] The sacrificial anode stent system may be employed in a
procedure for treatment of vascular defects where blockage of the
flow of fluid into an aneurysm and/or defective area of a vessel is
desired.
[0020] In one embodiment the sacrificial anode stent system
includes a support structure, namely a stent, which is positioned
within a blood vessel traversing the neck of a vascular defect; a
vaso-occlusive device, desirably in the form in the form of a coil
which is electrolytically detachable from a catheter and/or
guidewire as positioned within the interior of the stent for
traversal through a cell as defined by undulating bands within the
stent; where the support stent includes one or more sacrificial
electrolytically dissolvable sections functioning to prevent
degradation of the undulating bands during electrolytic separation
of the coil from the catheter/guidewire and thereafter as the stent
and the vaso-occlusive reside in the body.
[0021] The support structures such as stents may include radiopaque
markers which may be utilized to assist in the positioning of the
stent proximate to an affected vessel wall. The radiopaque markers
are generally secured to the distal ends of the stent extending
outwardly from one or more peaks or troughs of undulating bands.
One or more portions of sacrificial anode material may be
substituted for one or more of the radiopaque markers proximate to
the distal ends of the stent. It is anticipated that the
sacrificial anode materials will be adjacent to the radiopaque
markers thereby redirecting any electrolytical corrosion of the
sacrificial anode material and/or stent to a location away from the
vascular defect and/or aneurysm. The radiopaque portions may
include platinum, platinum-tungsten, palladium, platinum-iridium,
rhodium, tantalum, or alloys or composites of these metals.
[0022] The coil which may be utilized for positioning within an
aneurysm is desirably compressed within a sheath prior to delivery
to an aneurysm site. The coil is preferably sufficiently compressed
for passing engagement through the interior of the stent for
further traversal of the stent through either the gap between
adjacent peaks and troughs of an undulating band or through an
individual cell as defined by the undulating bands of the stent.
The catheter including the coil may be manipulated for traversal of
the stent into the wide-neck aneurysm site whereupon withdrawal or
retraction of the sheath for release of the compressed coil may
occur. The wide-neck aneurysm is thereby filled with the expanded
coil for the occlusion of the vascular defect. An electrical
current may then be applied to the catheter for corrosion of the
coil at an area defined as the sacrificial catheter/coil joint for
release of the coil from the catheter.
[0023] Prior to the separation of the coil from the catheter it is
anticipated that the coil will be in contact with, and held in a
desired position within a wide-neck aneurysm by, the undulating
bands forming the wall of the stent. An electrical pathway is
likely to occur between the coil and the stent upon the initiation
of electrical current for corrosion of the sacrificial
catheter/coil joint as a result of the probable contact between the
coil and the undulating bands of the stent. An electrical pathway
through the undulating bands to the distal ends of the stent is
provided where the sacrificial anode material is engaged to the
stent adjacent to the radiopaque markers. Corrosion of the
undulating bands of the stent may therefore be redirected to a
non-critical location adjacent to the radiopaque markers and away
from any vascular defect subject to treatment.
[0024] In addition to the effect of occlusion of fluid flow, the
sacrificial anode stent systems exhibits bio-compatibility, is
efficient to manufacture, and may be deployed using known stent
introduction techniques.
[0025] In one embodiment, the invention is directed to a
sacrificial anode stent system comprising a stent having at least
one sacrificial anode portion and a vaso-occlusive device. The
vaso-occlusive device has at least one portion with a potential
different from that of the sacrificial anode portion of the
stent.
[0026] The invention is also directed to a sacrificial anode stent
system comprising a stent and a medical device. The stent and the
medical device each have at least one metal portion. The metal
portion of the stent has a potential different from that of the
medical device. One of the stent and the medical device includes a
sacrificial portion of a different potential from that of the
remainder of the stent or medical device. The potential of the
sacrificial portion is such that corrosion occurs preferentially at
the sacrificial portion.
[0027] The invention is also directed to a stent including at least
one sacrificial anode portion. Typically, the sacrificial anode
portion is connected to the stent proximate to the proximal and/or
distal ends. Optionally, the sacrificial portion may be provided on
one or more tabs extending from an end of the stent.
[0028] All United States patents and applications and other
published documents mentioned anywhere within this application are
incorporated herein by reference in their entirety.
[0029] Without limiting the scope of the invention other aspects
and advantages of the invention will become apparent from the
following detailed description and the accompanying drawings which
illustrate by way of example the features of the invention. A brief
abstract of the technical disclosure and the specification is
provided as well for purposes of complying with 37 C.F.R.
.sctn.1.72.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0030] FIG. 1 shows an inventive sacrificial anode stent
system.
[0031] FIG. 2 shows a flat pattern of an inventive stent.
[0032] FIGS. 3 and 4 show a coil being inserted into an
aneurism.
DETAILED DESCRIPTION OF THE INVENTION
[0033] 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.
[0034] For the purposes of this disclosure, unless otherwise
indicated, identical reference numerals used in different Figures
refer to the same component.
[0035] The sacrificial anode stent system 10 generally includes a
vascular support structure in the form of a stent 100. Non-limiting
examples of stent which may be used in the instant invention are
disclosed in U.S. patent application Ser. No. 09/957,983 which is
incorporated herein by reference in its entirety. The sacrificial
anode stent system 10 also generally utilizes a vaso-occlusive
device such as a platinum coil 200 for positioning in a wide-neck
aneurysm 300 as more fully described in U.S. Pat. Nos. 5,423,829;
5,643,254; 6,059,779; and 6,024,754 as assigned to Target
Therapeutics, Inc., which are incorporated herein by reference in
their entireties.
[0036] In more detail, the vascular support structure of the
present invention, in one embodiment, is in the form of a stents
having a wall surface with a plurality of openings therein. The
stent may have a pattern such as those shown generally at 100 in
FIG. 2 by way of example. Stent 100 has a proximal end 102, a
distal end 104 and a flow path therethrough along a longitudinal
axis 106. Stent 100 comprises a plurality of undulating bands 108.
Each undulating band comprising a series of alternating peaks 110
and troughs 112. Peaks 110 are oriented in a distal direction and
troughs 112 are oriented in a proximal direction. A plurality of
connectors 114 extend between peaks 110 and troughs 112 of
longitudinally adjacent undulating bands.
[0037] Stent 100 is also provided with a sacrificial anode portion
120. The sacrificial anode portion is a portion of the stent with a
higher corrosion potential than the remainder of the stent. As
shown in the embodiment of FIG. 2, the sacrificial anode portion
120 is in the form of tabs of metal at both ends of the stent. More
generally, one or more sacrificial anode portions may be provided
at one or both ends of the stent or at any other suitable location
in the stent. For example, the sacrificial anode portion may be in
the form of additional material provided in the middle of the stent
or anywhere else along the body of the stent. Desirably, however,
the sacrificial anode portion of the stent is not necessary to the
overall structural integrity of the stent and/or to the ability of
the stent to support a vessel.
[0038] The sacrificial anode portion may be affixed to the stent
via the use of adhesives, laser welding techniques or other welding
techniques or swaged onto the stent. Other methods for
incorporating the sacrificial anode portion into the stent include
the use of various coating techniques including plating and vapor
deposition techniques. The sacrificial anode portion may also be
sprayed onto the appropriate portion of the stent or painted
on.
[0039] The sacrificial anode portion may also be provided in the
form of rivets of a higher potential metal which are disposed into
openings in a stent.
[0040] The sacrificial anode stent system 10 also comprises one or
more vaso-occlusive devices 200, as shown in FIG. 1 which may be
utilized to treat a wide-neck aneurysm 300.
[0041] Non-occlusive treatment of a wide-neck aneurysm 300 involves
the positioning of a support structure which may be a stent 100 as
earlier described to longitudinally traverse the neck 302 of the
aneurysm 300.
[0042] The wall surface of the stent 100 may be used to partially
occlude the neck of the aneurysm 302. The wall surface of stent 100
further functions to support a vaso-occlusive device.
[0043] Desirably, the vaso-occlusive device is in the form of a
coil. More desirably, it is in the form of a platinum coil or a
Guglielmi electrolytically detachable coil (GDC coil) 200. A stent
is disposed inside the wide-neck aneurysm 300 to assist in the
prevention of herniation of the aneurysm and/or undesirable
migration of coil 200 out of the aneurysm and into the parent
vessel 400.
[0044] The coil 200 is generally formed of platinum which is an
effective cathode with respect to most metals when exposed to an
electrical charge. Typically, support structure 100 is formed of
stainless steel, in the case of balloon expandable stents or
nitinol in the case of self-expanding stents. Stainless steel and
nitinol stents 100 function as an anode with respect to the coil
200 when in contact with one another in an electrolytic solution,
as is present in the body. This renders the stent susceptible to
electrolytic or galvanic corrosion deteriorating the integrity of
the stent adjacent to a diseased vessel.
[0045] To avoid undesirable corrosion of the stent 100 proximate to
a coil 200 or the like, the stent is provided with sacrificial
anode portions 120 which redirect electrolytic galvanic corrosion
to a desired non-critical location for the stent 100.
[0046] One or more sacrificial anode portions 120 may be provided.
Desirably, the sacrificial anode portions will be positioned at one
or both ends of the stent. In the embodiment of FIG. 2, sacrificial
anode portions 120 are provided at both the proximal and distal
ends of the stent.
[0047] The sacrificial anode portion 120 in another embodiment may
be engaged to the stent 100 at any desired location so long as the
corrosion/disintegration of the sacrificial anode portion 120 does
not adversely affect the structural integrity of the sent 100 and
particularly does not affect the structural integrity of the stent
100 adjacent to a vascular defect such as an aneurysm.
[0048] The sacrificial anode portions may be in the form of a metal
plated or coated onto a portion of the stent, or affixed, attached,
or otherwise engaged to the stent. The sacrificial anode portions
120 are in electrical communication with the remainder of the stent
100 and have a higher corrosion potential than the remainder of
stent 100.
[0049] Any suitable material may be selected for the sacrificial
anode portions 120 so long as the material has a higher corrosion
potential than the remainder of the stent or support structure.
Materials utilized for the sacrificial anode portion may include
but are not necessarily limited to magnesium, zinc, aluminum, mild
steel, low alloy steel, and/or iron. Desirably, the sacrificial
anode portion will be made of mild steel, low alloy steel, zinc,
aluminum, and magnesium.
[0050] Stents used in association with the sacrificial anode stent
system are commonly formed of stainless steel. The stainless steel
material for the stent is, in turn, a cathode with respect to the
sacrificial anode portion. The materials selected for the
sacrificial anode portion therefore function as an anode with
respect to the cathotic stainless steel stent.
[0051] The range of materials available for functioning as the
sacrificial anode material 120 is therefore quite large and are not
limited to the materials identified within the specification. It is
anticipated that any suitable metallic material may be utilized as
the sacrificial anode portion 120 provided that the material
selected has a higher corrosion potential than the remainder of the
stent 100.
[0052] Platinum is generally the most cathotic, and has the lowest
corrosion potential for materials selected for a coil 200.
Therefore, platinum is likely to be the most widely used material
as the coil for occlusion of an aneurysm.
[0053] The sacrificial anode portions 120 may generally be any size
as desired for use in a medical procedure. It is anticipated that
the sacrificial anode portions 120 will have size dimensions which
will not exceed 0.016 inches in diameter; 0.003 inches for wall
thickness; and 0.080 inches in length. Generally it is anticipated
that the sacrificial anode portions 120 will be cylindrical in
shape. Alternatively, the sacrificial anode portions 120 may be
solid or have any other geometric shape as desired. The size and
shape of the sacrificial anode portions 120 may vary considerably
dependent upon the area of the body lumen to be non-invasively
treated through the use of the sacrificial anode stent system
10.
[0054] The stent of FIG. 2 also includes optional end tabs which
are utilized to fixedly secure radiopaque markers 124. The
radiopaque markers 124 function to identify the location of the
opposite ends of a stent 100 relative to a body lumen in order to
facilitate desired positioning of the stent 100 adjacent to a
vessel defect such as an aneurysm 300. One or more radiopaque
markers may be replaced by one or more sacrificial anode portions
120. The end tabs of the known stents 100 may then be utilized as
the affixation sites for attachment of the sacrificial anode
portions 120.
[0055] The use of designated sacrificial corrosion portions 120
prevents the stent from deteriorating and/or breaking proximate to
a vascular defect minimizing risk of hemorrhage and/or rupture of
the body lumen or aneurysm 300. The amount of sacrificial anode
material 120 utilized should preferably be sufficient to remain
intact for a desired duration of time to permit complete
endothelialization of the stent. The amount of material utilized as
the sacrificial anode portion 120 may be determined upon
experimentation for identification of worse case corrosion rates
for the combination of a given stent and coil.
[0056] The provision of sacrificial anode portions 120 prevents
premature corrosion of the stent 100 and potential embolization of
a wide-neck aneurysm 300 or vessel defect. The support
structure/stent material and sacrificial anode portions 120 are
therefore required to be selected for the combination of electrical
parameters such that a higher corrosion potential exists for the
sacrificial anode portion 120 following exposure to electrical
current or galvanic electrolysis than the remainder of the stent
100. In addition, the combination materials selected for the
support structure/stent and sacrificial anode portions 120 are
required to be bio-compatible for use in treatment of vascular
defects such as wide-necked aneurysms.
[0057] Electrolytic complications such as corrosion of critical
portions of a stent are avoided by inclusion of sacrificial anode
portions 120 in non-critical portions of the stent. The use of
sacrificial anode portions 120 reduces the likelihood that a
portion of the stent material exposed to corrosion will become
liberated from the stent and enter the vasculature of an
individual. Further, the use of sacrificial anode portions 120
minimizes the liberation of large particles separating from the
stent at multiple electrolysis sites. The health and safety of an
individual is thereby significantly enhanced.
[0058] A potential complication to be addressed by the sacrificial
anode stent system 10 is the size of the diameter of the catheter
relative to the size of the cell opening or gap between adjacent
peaks and troughs of adjacent undulating bands forming the stent
100. In this instance an introducer which may be a catheter having
a sheath or a guidewire within the catheter may be utilized for
extension outwardly from the sheath for insertion of a coil 200
traversly through a cell or gap between the undulating bands of the
stent for insertion into the wide-neck aneurysm.
[0059] In one embodiment, a coil 200 may be compacted and enclosed
within a sheath of a catheter. In this instance the diameter of the
catheter is sufficiently small for passing through an opening in
the wall of the stent for introduction into a wide-neck aneurysm.
Retraction of the sheath relative to the catheter exposes the coil
200 enabling further introduction of the coil 200 and expansion of
the coil 200 within the wide-neck aneurysm to occlude the vascular
defect.
[0060] In an alternative embodiment, a coil 200 may be enclosed
within a sheath for delivery to an aneurysm site through the use of
an introducer or catheter having a sheath. Prior to the
introduction of the coil 200 into a wide-neck aneurysm the sheath
may be retracted where only the coil 200 traverses the stent
through a cell opening or through a gap between adjacent undulating
bands.
[0061] In another embodiment, as shown in FIG. 3, a microcatheter
250 may be utilized as a delivery introducer for the coil 200
through the body lumen and stent for introduction into the
wide-neck aneurysm. The microcatheter desirably easily passes
through an opening in the wall surface of the stent for entry of
the coil 200 into the vascular defect.
[0062] As may be seen in FIGS. 3 and 4, an initial treatment of an
aneurysm 300 is shown. The aneurysm 300 includes a neck 302. A
delivery catheter 250 delivers a coil 200, through the an opening
in the sidewall of the stent into an aneurysm 300 Before the
positioning of the catheter 250 as shown in FIG. 3, the catheter
body may be guided by a guidewire that the distal tip of the
catheter is within the aneurysm space. The guidewire may then be
withdrawn to allow introduction of other vaso-occlusive material as
described herein.
[0063] FIG. 4 shows a vaso-occlusive device 200 being ejected from
the distal tip of the catheter. In this instance, the
vaso-occlusive device 200 is shown to be a coil having secondary
form which is generally somewhat random in nature. In this
variation of the invention, the coil 200 may be coated with a
polymeric composition. The coil 200 is generally introduced within
the aneurysm space to substantially fill the space to promote
occlusion.
[0064] Following introduction of the coil 200 within the aneurysm
space, the delivery catheter may be withdrawn from the body lumen
for termination of the non-invasive procedure.
[0065] Additional details of a coil 200 and the delivery thereof
may be found in U.S. Pat. Nos. 4,994,069; 6,059,779; 5,643,254;
5,423,829; 6,024,754; and 5,522,822.
[0066] A platinum or Guglielmi detachable coil (GDC coil) is more
desirable in that the physician may place the coil accurately in a
final position within the selected site prior to releasing the coil
through the use of electrolysis.
[0067] In the case where the vaso-occlusive device is a coil, the
sacrificial anode portion 120 of the stent is desirably
sufficiently large to avoid disintegration and/or detachment from
the stent 100 prior to the disintegration of the coil 200 from an
introducer which occurs at the location of a sacrificial joint in
the delivery system.
[0068] The material selected for the sacrificial anode portion 120
has a higher corrosion potential than the primary support structure
or stent 100. The material selected for the sacrificial anode
portion 120 also has a lower corrosion potential than the
sacrificial joint 706 between a coil 200 and an introducer.
[0069] Exposure of electrical current to the sacrificial anode
stent system 10 thereby initiates corrosion/deterioration at the
sacrificial joint simultaneously to the sacrificial anode portion
120. The material selected for the sacrificial joint corrodes more
rapidly due to the sacrificial joint having a higher corrosion
potential. The complete disintegration of the sacrificial joint
between the coil 200 and an introducer therefore occurs prior to
the complete corrosion and/or deterioration of the sacrificial
anode portion 120.
[0070] An indicator may be utilized to signal the separation of the
coil 200 from an introducer for triggering of a switch to terminate
the application of additional electrical current to the sacrificial
anode stent system 10. Any excess current exposed to the
sacrificial anode stent system 10 following separation of the coil
200 from the introducer thereby primarily affects the sacrificial
anode portion 120 which in turn directs electrolytic corrosion away
from critical areas of the stent 100.
[0071] The electrical current exposed to the support
structure/stent 100 during separation of the coil 200 from the
introducer causes minimal electrolytic or galvanic corrosion of the
stent 100 due to the selection of a material for the stent 100
having a relatively low corrosion potential as compared to the
sacrificial joint 706 and the sacrificial anode portion 120.
[0072] The integrity of the radiopaque markers 124 is generally not
adversely affected by the application of electrical current to the
sacrificial anode stent system 10. In an alternative embodiment
where metallic materials have been utilized within the radiopaque
markers 124, the metallic material selected has a corrosion
potential which is lower than both the sacrificial joint 706 and
sacrificial anode portions 120. Separation of the radiopaque
markers 124 from the stent 100 is therefore prohibited.
[0073] The invention is also directed to a sacrificial anode stent
system comprising a stent and a medical device, the stent and the
medical device each having at least one metal portion, the metal
portion of the stent having a potential different from that of the
medical device, wherein one of the stent and the medical device
includes a sacrificial portion of a different potential from that
of the remainder of the stent or medical device, the potential of
the sacrificial portion such that corrosion occurs preferentially
at the sacrificial portion.
[0074] In one embodiment, the medical device is a coil and the
sacrificial portion is part of the stent. The coil desirably
includes platinum and the non-sacrificial portion of the stent
desirably includes stainless steel although other combinations of
metal may also be used. Most desirably, the sacrificial portion
includes magnesium, zinc, aluminum, mild steel, low alloy steel,
and/or iron.
[0075] In another embodiment, the sacrificial anode portion may be
provided in the vaso-occlusive device. This would be appropriate
where the choice of metals is such that the vaso-occlusive device
would corrode more readily than the stent.
[0076] The invention is directed to the above-described sacrificial
anode system and to methods of using the system in the treatment of
patients as well as to inventive stents such as that shown in FIG.
2 having regions of sacrificial anode material. The design of the
stent may be modified in numerous ways as discussed below.
[0077] Bands of different amplitude and/or wavelength may be
provided, as disclosed for example in U.S. application Ser. No.
09/957,983. Where serpentine bands are provided which are not
characterized as having a wavelength and/or amplitude, different
bands may have different numbers of peaks and troughs, as shown for
example, in U.S. application Ser. No. 09/957,983. Bands of
different longitudinal extent may also be provided as disclosed
therein.
[0078] The connections between adjacent bands may be longitudinal
or may be non-longitudinal. Examples of non-longitudinal connectors
are disclosed in U.S. Pat. No. 6,348,065 and U.S. Pat. No.
5,922,021. Non-longitudinal connectors may be linear or may have
one or more curved portions. Depending on the type of
non-longitudinal connector, the ends of the connector may be
circumferentially and longitudinally offset from one another as
disclosed in U.S. Pat. No. 6,348,065 and U.S. Pat. No.
5,922,021.
[0079] Other designs may also be employed with the inventive
stents. For example, a Palmaz design such as those disclosed in
U.S. Pat. No. 4,776,337 may be modified by providing it with
sacrificial anode material. In one embodiment, the sacrificial
anode material would be provided on one or more tabs which extend
from one or both ends of the stent.
[0080] The inventive stents disclosed herein may be off uniform
wall thickness or may have different wall thicknesses in different
portions of the stent. One end or both ends may be thicker than the
middle of the stent or thinner than the middle of the stent. The
thickness of the stent may increase from one end to the other
end.
[0081] Regions of differing rigidity may be achieved by providing
more connectors in one or more portions of the stent than in other
portions. The rigidity may also be affected by changing the nature
of the connectors in differing portions of the stent. For example,
spiral connections between undulating bands or sections of the
stent will result in more flexibility than straight connectors,
given a constant spacing between the bands. Thicker or stronger
material may also be used in one or more portions of the stent to
provide additional rigidity to the stent. The stent may be provided
with one or more ends of increased rigidity compared to the middle
of the stent or with one or more ends of decreased rigidity
compared to the middle of the stent.
[0082] The inventive stent may be of uniform cross-section or may
exhibit a taper in one or both ends of the stent in the unexpanded
and/or expanded configurations.
[0083] The inventive stent may also be in the form of a bifurcated
stent.
[0084] As discussed above, any of the inventive stents disclosed
herein may be provided with one or more radiopaque portions. The
radiopaque portions may be provided in the form of a coating or
plating or may be adhered to the stent mechanically or via welding.
The radiopaque portion may also be swaged to the stent or provided
in the form of a rivet. The ends of the stent may be provided with
the radiopaque portion or any other desirable portion of the stent
including the middle portion.
[0085] The inventive medical devices may also be provided with
various biocompatible coatings to enhance various properties of the
inventive medical devices. For example, the inventive medical
devices may be provided with lubricious coatings or other polymeric
coatings. An example of a suitable polymeric coating is PTFE.
[0086] The inventive stents and/or coils disclosed herein may
include one or more coatings which comprise one or more therapeutic
agents, cellular materials, polymeric agents
[0087] The therapeutic agent may be non-genetic or genetic.
Suitable nongenetic 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 such as D-Phe-Pro-Arg chloromethyl
keton, an RGD peptide-containing compound, heparin, antithrombin
compounds, platelet receptor antagonists, antithrombin antibodies,
anti-platelet receptor antibodies, aspirin, prostaglandin
inhibitors, platelet inhibitors and tick antiplatelet peptides,
vascular cell growth promoters such as growth factor inhibitors,
growth factor receptor antagonists, transcriptional activators, and
translational promoters, vascular cell growth inhibitors such as
growth factor inhibitors, growth factor receptor antagonists,
transcriptional repressors, translational repressors, replication
inhibitors, 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-lowering agents; vasodilating
agents; and agents which interfere with endogenous vascoactive
mechanisms.
[0088] Suitable genetic materials include anti-sense DNA and RNA,
DNA coding for anti-sense RNA, tRNA or rRNA to replace defective or
deficient endogenous molecules, 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 including CD inhibitors,
thymidine kinase ("TK") and other agents useful for interfering
with cell proliferation, 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-11, BMP-12, BMP-13, BMP-14, BMP-15, and
BMP-16. Any of BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 and BMP-7 are
particularly desirable. 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.
[0089] Suitable cellular materials include cells of human origin
(autologous or allogeneic) or from an animal source (xenogeneic),
genetically engineered if desired to deliver proteins of interest
at the transplant site. The delivery media can be formulated as
needed to maintain cell function and viability.
[0090] Suitable polymer coating materials 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,
polyesters including polyethylene terephthalate, polyacrylamides,
polyethers, polyether sulfone, polycarbonate, polyalkylenes
including polypropylene, polyethylene and high molecular weight
polyethylene, halogenated polyalkylenes including
polytetrafluoroethylene, polyurethanes, polyorthoesters, proteins,
polypeptides, silicones, siloxane polymers, polylactic acid,
polyglycolic acid, polycaprolactone, polyhydroxybutyrate valerate
and blends and copolymers thereof, coatings from polymer
dispersions such as polyurethane dispersions (BAYHDROL.RTM., etc.),
fibrin, collagen and derivatives thereof, polysaccharides such as
celluloses, starches, dextrans, alginates and derivatives,
hyaluronic acid, squalene emulsions. Desirably, 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 hereby incorporated herein by reference, may be used. Also
desirably, the polymer may be a copolymer of polylactic acid and
polycaprolactone. Other materials include selected medical-grade
biodegradable materials such as PGA-TMC, Tyrosine-Derived
Polycarbonates and arylates, polycaprolactone co butyl acrylate and
other co polymers, Poly-L-lactic acid blends with DL-Lactic Acid,
Poly(lactic acid-co-glycolic acid), polycaprolactone co PLA,
polycaprolactone co butyl acrylate and other copolymers,
Tyrosine-Derived Polycarbonates and arylate, poly amino acid,
polyphosphazenes, polyiminocarbonates,
polydimethyltrimethylcarbonates, biodegradable CA/PO.sub.4'S,
cyanoacrylate, 50/50 DLPLG, polydioxanone, polypropylene fumarate,
or polydepsipeptides.
[0091] Other suitable coatings include macromolecules such as
chitosan and Hydroxylpropylmethylcellulose. Surface erodible
materials may also be used. Coatings may also comprise maleic
anhydride copolymers, zinc-calcium phosphate and amorphous
polyanhydrides.
[0092] The inventive medical devices may also be provided with a
sugar or more generally a carbohydrate and/or a gelatin to maintain
the inventive medical devices on a balloon during delivery of the
medical device to a desired bodily location. Other suitable
compounds for treating the inventive medical devices include
biodegradable polymers and polymers which are dissolvable in bodily
fluids. Portions of the interior and/or exterior of the inventive
medical devices may be coated or impregnated with the compound.
Mechanical retention devices may also be used to maintain the
inventive medical devices on the balloon during delivery.
[0093] The inventive medical devices may also be provided in whole
or in part with one or more of the above therapeutic agents,
polymeric coatings or the like. Where multiple therapeutic agents
are provided, the different coatings may release the drugs at
different rates. For example, one therapeutic agent may be released
at a fast rate and another therapeutic agent may be released at a
slow rate. Where multiple polymeric coatings are provided, the
coatings may degrade or erode at different rates.
[0094] Desirably, the sacrificial anode portions are not coated to
a greater extent than the non-sacrificial anode portions to
facilitate corrosion of the sacrificial anode portion rather than
the remainder of the stent or other medical device.
[0095] The invention is also directed to other combinations of
medical devices with sacrificial anode portions. For example, where
a stent is used in combination with an implantable filter, for
example, a vena cava filter, and the stent and implantable filter
are made of different metals, one of the devices may be provided
with a sacrificial implant portion, in accordance with the instant
invention. The inventive stents and systems may find use in a
variety of regions in the body including 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, the prostate and bowels, or any
other tubular organs. It is anticipated that the sacrificial anode
stent system may be utilized for treatment of a cranial or brain
aneurysm. The sacrificial anode stent system may also be used in
the treatment of abdominal aortic aneurysms or other aneurysms
within the body lumen.
[0096] In an alternative embodiment, the stent may be formed of
more than one type of material where different portions of the
stent are formed of different materials. In this embodiment, the
sacrificial anode portion's 120 are required to have a higher
corrosion potential than all materials selected for incorporation
into the stent. The sacrificial anode portions 120 therefore
function as anodes to redirect electrolytic corrosion away from the
stent. The two or more materials incorporated into the stent in
this embodiment are required to be in electric communication with
each other to prevent electrical insulation and/or isolation of a
particular material or area of the stent. The electric insulation
and/or isolation within a particular area of the stent requires
that the sacrificial anode portions 120 be in electric
communication with each electrically independent portion of the
stent. The electrical coupling of the sacrificial anode portions
120 to each electrically isolated portion of the stent facilitates
redirection of any electrolytic corrosion away from the stent and
vascular defect.
[0097] In another embodiment, two or more stents may be utilized
within a procedure for treatment of a vessel defect. In this type
of procedure a stent may be positioned within the interior of or
adjacent to one or more additional stents. The material selected
for the one or more additional stents may be identical or may be
formed of different materials as required during a treatment
procedure. In this embodiment, the two or more stents may be in
contact and electrical communication with each other where only one
stent is required to include the sacrificial anode portions 120.
Alternatively, each stent may include one or more sacrificial anode
portion's 120 to redirect electrolytic corrosion to a non-critical
or desired location of the stent. In this embodiment, the
sacrificial anode portions 120 generally have a higher corrosion
potential than any and/or all of the materials selected for the one
or more stents. Sacrificial anode portions 120 therefore function
as sacrificial anodes with respect to the cathode of the stent
and/or coil 200.
[0098] In yet another alternative embodiment a stent may be
bifurcated where one arm or leg section is formed of one material
and an another section or leg is formed of a second material. If
the two materials do not have sufficient electrical communication
therebetween, one or more of the sections may include a sacrificial
anode portion 120 having a higher corrosion potential than the
respective section or leg of the stent. For example, one branch may
be formed of a different metal than the trunk, with the branch or
trunk including a sacrificial anode portion.
[0099] In still another alternative embodiment, an aneurysm may be
treated through the positioning of a coil 200 within the aneurysm
and then the filling of the aneurysm with a liquid polymer mass
which may be loaded with noble metal powder. It is anticipated that
the noble metal powder will be in electric communication within a
coil 200 and will simultaneously be in electric communication with
the stent. The stent assists in the positioning and retention of
the liquid polymer within the aneurysm. The sacrificial anode
portions 120 in this embodiment preferably have a higher corrosion
potential as compared to the stent, noble metal loaded polymer
material, and the coil 200 to redirect electrolytic corrosion to
the sacrificial anode portion's 120 and away from the noble metal
powder, stent, or coil 200.
[0100] 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.
[0101] 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 3 may be taken as
alternatively dependent from claim 2; claim 4 may be taken as
alternatively dependent on claim 2, or on claim 3; claim 5 may be
taken as alternatively dependent on any of claims 2-4; claim 6 may
be taken as alternatively dependent on any of claims 2-5;
etc.).
* * * * *