U.S. patent application number 12/781268 was filed with the patent office on 2010-09-09 for endovascular prosthesis.
Invention is credited to THOMAS R. MAROTTA, DONALD R. RICCI.
Application Number | 20100223776 12/781268 |
Document ID | / |
Family ID | 34549761 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100223776 |
Kind Code |
A1 |
MAROTTA; THOMAS R. ; et
al. |
September 9, 2010 |
ENDOVASCULAR PROSTHESIS
Abstract
An expandable endovascular prosthesis comprising: body having a
proximal end and a distal end; a first expandable portion disposed
between the proximal end and the distal end, the tubular first
expandable portion being expandable from a first, unexpanded state
to a second, expanded state with a radially outward force thereon
to urge the first expandable portion against a vascular lumen; and
a second expandable portion attached to the first tubular
expandable portion; the second expandable portion being expandable
upon expansion of the tubular first expandable portion. The
endovascular prosthesis is particularly useful in the treatment of
aneurysms, particularly saccular aneurysms. Thus, the first
expandable portion serves the general purpose of fixing the
endovascular prosthesis in place at a target vascular lumen or body
passageway in the vicinity at which the aneurysm is located and,
upon expansion of the first expandable portion, the second
expandable portion expands to block the aneurysmal opening thereby
leading to obliteration of the aneurysm. A method of delivering and
implanting the endovascular prosthesis is also described.
Inventors: |
MAROTTA; THOMAS R.; (North
Vancouver, CA) ; RICCI; DONALD R.; (Vancouver,
CA) |
Correspondence
Address: |
KATTEN MUCHIN ROSENMAN LLP;(C/O PATENT ADMINISTRATOR)
2900 K STREET NW, SUITE 200
WASHINGTON
DC
20007-5118
US
|
Family ID: |
34549761 |
Appl. No.: |
12/781268 |
Filed: |
May 17, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11003644 |
Dec 6, 2004 |
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12781268 |
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09640750 |
Aug 18, 2000 |
6969401 |
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11003644 |
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Current U.S.
Class: |
29/446 |
Current CPC
Class: |
A61F 2/844 20130101;
A61F 2002/065 20130101; A61F 2002/825 20130101; A61F 2/915
20130101; A61F 2/91 20130101; A61F 2/856 20130101; Y10T 29/49863
20150115; A61F 2002/91525 20130101; A61F 2/958 20130101; A61F
2002/91575 20130101; A61F 2002/823 20130101; A61F 2002/91533
20130101; A61F 2230/0095 20130101 |
Class at
Publication: |
29/446 |
International
Class: |
B23P 11/02 20060101
B23P011/02 |
Claims
1. A method of compressing a partially pre-expanded endovascular
prosthesis to a pre-determined diameter, the method comprising the
steps of: (i) inserting a mandrel element in the partially
pre-expanded endovascular prosthesis, (ii) disposing the partially
pre-expanded endovascular prosthesis between a first plate element
and a second plate element; (iii) moving the first plate element
with respect to the second plate; and (iv) causing the partially
pre-expanding endovascular prosthesis to compress toward the
mandrel element until the pre-determined diameter is reached.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 11/003,644, filed Dec. 6, 2004, which is a continuation of
U.S. patent application Ser. No. 09/640,750, filed Aug. 18, 2000,
now U.S. Pat. No. 6,969,401, issued Nov. 29, 2005, the contents of
all incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] In one of its aspects, the present invention relates to an
endovascular prosthesis. In another of its aspects, the present
invention relates to a method of treating an aneurysm in a
patient.
[0004] 2. Description of the Prior Art
[0005] As is known in the art, an aneurysm is an abnormal bulging
outward in the wall of an artery. In some cases, the bulging may be
in the form of a smooth bulge outward in all directions from the
artery--this is known as a "fusiform aneurysm". In other cases, the
bulging may be in the form of a sac arising from an arterial
branching point or from one side of the artery--this is known as a
"saccular aneurysm".
[0006] While aneurysms can occur in any artery of the body, it is
usually those which occur in the brain which lead to the occurrence
of a stroke. Most saccular aneurysms which occur in the brain have
a neck which extends from the cerebral blood vessel and broadens
into a pouch which projects away from the vessel.
[0007] The problems caused by such aneurysms can occur in several
different ways. For example, if the aneurysm ruptures, blood enters
the brain or the subarachnoid space (i.e., the space closely
surrounding the brain)--the latter is known as aneurysmal
subarachnoid hemorrhage. This followed by one or more of the
following symptoms: nausea, vomiting, double vision, neck stiffness
and loss of consciousness. Aneurysmal subarachnoid hemorrhage is an
emergency medical condition requiring immediate treatment. Indeed,
10-15% of patients with the condition die before reaching the
hospital for treatment. More than 50% of patients with the
condition will die within the first thirty days after the
hemorrhage. Of those patients who survive, approximately half will
suffer a permanent stroke. Some of these strokes occur one to two
weeks after the hemorrhage itself from vasospasm in cerebral
vessels induced by the subarachnoid hemorrhage. Aneurysms also can
cause problems which are not related to bleeding although this is
less common. For example, an aneurysm can form a blood clot within
itself which can break away from the aneurysm and be carried
downstream where it has the potential to obstruct an arterial
branch causing a stroke. Further, the aneurysm can also press
against nerves (this has the potential of resulting in paralysis or
abnormal sensation of one eye or of the face) or the adjacent brain
(this has the potential of resulting in seizures).
[0008] Given the potentially fatal consequences of the aneurysms,
particularly brain aneurysms, the art has addressed treatment of
aneurysms using various approaches.
[0009] Generally, aneurysms may be treated from outside the blood
vessels using surgical techniques or from the inside using
endovascular techniques (the latter falls under the broad heading
of interventional (i.e., non-surgical) techniques).
[0010] Surgical techniques usually involve a craniotomy requiring
creation of an opening in the skull of the patient through which
the surgeon can insert instruments to operate directly on the
brain. In one approach, the brain is retracted to expose the
vessels from which the aneurysm arises and then the surgeon places
a clip across the neck of the aneurysm thereby preventing arterial
blood from entering the aneurysm. If there is a clot in the
aneurysm, the clip also prevents the clot from entering the artery
and obviates the occurrence of a stroke. Upon correct placement of
the clip the aneurysm will be obliterated in a matter of minutes.
Surgical techniques are the most common treatment for aneurysms.
Unfortunately, surgical techniques for treating these conditions
are regarded as major surgery involving high risk to the patient
and necessitate that the patient have strength even to have a
chance to survive the procedure.
[0011] As discussed above, endovascular techniques are non-surgical
techniques and are typically performed in an angiography suite
using a catheter delivery system. Specifically, known endovascular
techniques involve using the catheter delivery system to pack the
aneurysm with a material which prevents arterial blood from
entering the aneurysm--this technique is broadly known as
embolization. One example of such an approach is the Guglielmi
Detachable Coil which involves intra-aneurysmal occlusion of the
aneurysm via a system which utilizes a platinum coil attached to a
stainless steel delivery wire and electrolytic detachment. Thus,
once the platinum coil has been placed in the aneurysm, it is
detached from the stainless steel delivery wire by electrolytic
dissolution. Specifically, the patient's blood and the saline
infusate act as the conductive solutions. The anode is the
stainless steel delivery wire and the cathode is the ground needle
which is placed in the patient's groin. Once current is transmitted
through the stainless steel delivery wire, electrolytic dissolution
will occur in the uninsulated section of the stainless steel
detachment zone just proximal to the platinum coil (the platinum
coil is of course unaffected by electrolysis). Other approaches
involve the use of materials such as cellulose acetate polymer to
fill the aneurysm sac. While these endovascular approaches are an
advance in the art, they are disadvantageous. Specifically, the
risks of these endovascular approaches include rupturing the
aneurysm during the procedure or causing a stroke due to distal
embolization of the device or clot from the aneurysm. Additionally,
concern exists regarding the long term results of endovascular
aneurysm obliteration using these techniques. Specifically, there
is evidence of intra-aneurysmal rearrangement of the packing
material and reappearance of the aneurysm on follow-up
angiography.
[0012] One particular type of brain aneurysm which has proven to be
very difficult to treat, particularly using the surgical clipping
or endovascular embolization techniques discussed above occurs at
the distal basilar artery. This type of aneurysm is a weak
outpouching, usually located at the terminal bifurcation of the
basilar artery. Successful treatment of this type of aneurysm is
very difficult due, at least in part, to the imperative requirement
that all the brainstem perforating vessels be spared during
surgical clip placement.
[0013] Unfortunately, there are occasions when the size, shape
and/or location of an aneurysm make both surgical clipping and
endovascular embolization not possible for a particular patient.
Generally, the prognosis for such patients is not good.
[0014] In International Publication Number WO 99/40873 [Marotta et
al. (Marotta #1)], published Aug. 19, 1999, there is taught a novel
endovascular approach useful in blocking of an aneurysmal opening,
particularly those in saccular aneurysms, leading to obliteration
of the aneurysm. The approach is truly endovascular in that, with
the endovascular prosthesis taught by Marotta #1, there is no
requirement to pack the aneurysmal sac with a material (e.g., such
is used with the Guglielmi Detachable Coil). Rather, the
endovascular prosthesis taught by Marotta #1 operates on the basis
that it serves to block the opening to the aneurysmal sac thereby
obviating the need for packing material. Thus, the endovascular
prosthesis taught by Marotta #1 is an important advance in the art
since it obviates or mitigates many of the disadvantages of the
prior art. The endovascular prosthesis taught by Marotta #1
comprises a leaf portion capable of being urged against the opening
of the aneurysm thereby closing the aneurysm. In the endovascular
prosthesis taught by Marotta #1, the leaf portion is attached to,
and independently moveable with respect to, a body comprising at
least one expandable portion. The expandable portion is expandable
from a first, unexpanded state to a second, expanded state with a
radially outward force thereon. Thus, the body serves the general
purpose of fixing the endovascular prosthesis in place at a target
body passageway or vascular lumen in the vicinity at which the
aneurysmal opening is located and the leaf portion serves the
purpose of sealing the aneurysmal opening thereby leading to
obliteration of the aneurysm. Thus, as taught by Marotta #1, the
leaf portion functions and is moveable independently of the body of
the endovascular prosthesis.
[0015] While the endovascular prosthesis taught by Marotta #1 is a
significant advance in the art, there is still room for
improvement. Specifically, in the preferred embodiment of the
endovascular prosthesis taught by Marotta #1, once the device is
deployed and the leaf portion is properly positioned, the surface
area of the leaf portion is delimited by the surface area of the
tube from which the leaf portion was cut. While this may not be a
problem in most instances, there are occasions where the aneurysmal
opening is sufficiently large that there exists a real possibility
that the leaf portion will not completely close off the aneurysmal
opening. On the other hand, if one attempts to increase the size of
the leaf portion by cutting it from a larger diameter tube, the
diameter of the prosthesis increases which can make it more
difficult to navigate into the correct position and to use with
conventional delivery devices.
[0016] Thus, it would be highly desirable to have an endovascular
prosthesis having an expandable leaf portion.
SUMMARY OF THE INVENTION
[0017] It is an object of the present invention to provide a novel
endovascular prosthesis which obviates or mitigates at least one of
the above-mentioned disadvantages of the prior art.
[0018] It is another object of the present invention to provide a
novel method for endovascular blocking an aneurysmal opening which
obviates or mitigates at least one of the above-mentioned
disadvantages of the prior art.
[0019] Accordingly, in one of its aspects, the present invention
relates to an expandable endovascular prosthesis comprising:
[0020] a body having a proximal end and a distal end;
[0021] a first expandable portion disposed between the proximal end
and the distal end, the first expandable portion being expandable
from a first, unexpanded state to a first, expanded state with a
radially outward force thereon to urge the first expandable portion
against a vascular lumen;
[0022] a second expandable portion attached to the first expandable
portion, the second expandable portion being expandable from an
second, unexpanded state to a second expanded state upon expansion
of the first expandable portion; and
[0023] a covering material having a first surface area disposed
over a second surface area of the second expandable portion, the
first surface area being greater than the second surface area in
the second unexpanded state of the second expandable portion.
[0024] In yet another of its aspects, the present invention relates
to a method for endovascular blocking of an aneurysmal opening with
a prosthesis comprising: a body having a proximal end and a distal
end, a first expandable portion disposed between the proximal end
and the distal end, the first expandable portion being expandable
from a first, unexpanded state to a first, expanded state with a
radially outward force thereon to urge the first expandable portion
against a vascular lumen, a second expandable portion attached to
the first expandable portion; the second expandable portion being
expandable upon expansion of the first expandable portion, and a
covering material having a first surface area disposed over a
second surface area of the second expandable portion, the first
surface area being greater than the second surface area in the
second unexpanded state of the second expandable portion, the
method comprising the steps of:
[0025] disposing the prosthesis on a catheter;
[0026] inserting the prosthesis and catheter within a body
passageway by catheterization of the body passageway;
[0027] translating the prosthesis and catheter to a target vascular
lumen at which the aneurysm opening is located;
[0028] exerting a radially outward expansive force on the first
expandable portion such that the tubular first expandable portion
is urged against the target body passageway;
[0029] causing expansion of the first expandable portion to expand
the second expandable portion to increase the first surface area;
and
[0030] urging the second expandable portion against the aneurysmal
opening thereby blocking the aneurysmal opening.
[0031] In another of its aspects, the present invention relates to
a method for producing a prosthesis comprising: a body having a
proximal end and a distal end, a first expandable portion disposed
between the proximal end and the distal end, the first expandable
portion being expandable from a first, unexpanded state to a first,
expanded state with a radially outward force thereon to urge the
first expandable portion against a vascular lumen, a second
expandable portion attached to the first expandable portion; the
second expandable portion being expandable from a second,
unexpanded state to a second, expanded state upon expansion of the
first expandable portion, and a covering material having a first
surface area disposed over a second surface area of the second
expandable portion, the first surface area being greater than the
second surface area in the second unexpanded state of the second
expandable portion, the method comprising the steps of:
[0032] (i) expanding the second expandable portion;
[0033] (ii) affixing the covering material to the second expandable
portion; and
[0034] (iii) compressing the second expandable portion.
[0035] Thus, the present inventors have discovered a novel
endovascular prosthesis having the characteristic of a covering
material disposed on the second expandable portion. In the
unexpanded state of the prosthesis, the covering material has a
surface area which is larger than the surface area of the second
expandable portion over which it is disposed. This significantly
facilitates expansion of the second expandable portion compared to
the case where the covering material has a surface area
substantially the same as that of the second expandable portion
over which it is disposed. In most cases, as the second expandable
portion is expanded, the surface area thereof will increase to be
equal to or greater than the surface area of the covering material
in the unexpanded state of the second expandable portion. In the
latter case, it is therefore preferred to use a covering material
which has some elasticity so that it may be stretched further
beyond its original surface area in the unexpanded state of the
second expandable portion.
[0036] In copending International patent application Ser. No.
PCT/CA00/00125 [Marotta et al. (Marotta #2)], filed Feb. 11, 2000,
there is taught a novel endovascular prosthesis having the
characteristic of a first expandable portion which when expanded,
causes a second expandable portion (connected to the first
expandable portion) to expand. For example, if the second
expandable portion is made of a plastically deformable material
(e.g., stainless steel), upon expansion, the first expandable
portion will plastically deform. Such expansion will expand the
second expandable portion. While the endovascular prosthesis taught
by Marotta #2 is a further significant advance in the art, there is
still room for improvement. Specifically, in Marotta #2, the
preferred form of the second expandable (or "leaf") portion is a
porous surface comprising a surface of interconnected struts such
as that illustrated in FIGS. 9-14. With reference to these Figures,
Marotta #2 teaches the use of a covering material which is suitably
to: (i) withstand expansion of the leaf portion, and (ii) block the
aneurysmal opening after deployment. In other words, the leaf
portion is covered with the covering material in the unexpanded
state of the prosthesis. This renders opening of the leaf portion
difficult in some cases since the inherent forces of the covering
material tend to bias the leaf portion against opening upon
expansion of the prosthesis--this is acknowledged in Marotta
#2.
[0037] Thus, the present inventors have discovered an improvement
to the Marotta #2 endovascular prosthesis particularly when applied
using a porous leaf portion such as the one illustrated in FIGS.
9-14. Specifically, the approach involves partially, pre-expanding
the prosthesis thereby partially, pre-expanding the leaf portion
before the cover material is applied to the leaf portion. Once the
covering material has been applied to the leaf portion, the entire
prosthesis is then compressed, preferably to its original
configuration. This results in a cover material having a total
surface area which is larger than the compressed leaf portion.
Those of skill in the art will recognize that, when it is desired
to deploy the endovascular prosthesis by expansion thereof,
expansion of the leaf portion will be greatly facilitated by virtue
of the fact that there is more surface area in the covering
material compared with the leaf portion over which the covering
material is disposed in the unexpanded state of the prosthesis.
[0038] As will be developed below, it is preferred to construct the
present endovascular prosthesis out of a plastically deformable
material (e.g., stainless steel). In this preferred embodiment, it
is desirable to pre-expand the prosthesis to a point at which the
body portion and leaf portion plastically deform resulting in at
least partial expansion of the leaf portion. At this point, the
leaf portion is covered with a suitable covering material and the
prosthesis is compressed, preferably to its former
configuration.
[0039] Thus, in the present endovascular prosthesis, the body has a
proximal end and distal end. Disposed between the proximal end and
the distal end, there are at least two expandable portions
connected to one another. The first expandable portion is
expandable from a first, unexpanded state to a second, expanded
state with a radially outward force thereon. The second expandable
portion is attached to the first expandable portion and is caused
to expand by the first expandable portion--i.e., expansion of the
second expandable portion is not achieved exclusively by the means
used to expand the first expandable portion.
[0040] The body of the present endovascular prosthesis has a
generally longitudinal axis and is flexible. In a preferred
embodiment, the second expandable portion is independently moveable
between at least a first position and a second position with
respect to the body, expanded or unexpanded. Thus, in the first
position, the distal end and the proximal end of the body
(including the first expandable portion) are aligned with the
second expandable portion. In the second position, while securing
the distal end and the proximal end of the body, the second
expandable portion maintains a degree of independent movement. In
this manner, the second expandable portion is "independently
moveable" with respect to the body. In one embodiment, it is
preferred that this independent movement is achieved by disposing
the second expandable portion such that it may pivot with respect
to the remainder of the endovascular prosthesis. It should be
understood that, while the second expandable portion may be
independently moveable with respect to the body, the final
alignment of the distal end, the proximal end and second expandable
portion (i.e., the alignment after blockage of the aneurysmal
opening) is not particularly restricted and depends on factors such
as the size and location of the aneurysm and the anatomy of the
particular patient. The key point of this preferred embodiment is
that the second expandable portion is capable of being
independently moved with respect to the body.
[0041] As discussed above, the second expandable portion has a
surface area thereof covered with a covering material. The nature
of the covering material is not particularly restricted provided
that it is non-toxic and capable of withstanding expansion of the
second expandable portion. The preferred material will have a
degree of elasticity and sufficient tensile strength to maintain
its integrity when stretched by expansion of the second expandable
(or leaf) portion.
[0042] The present endovascular prosthesis is believed to be
particularly useful in the treatment of aneurysms such as those
described hereinabove and is therefore believed to provide a
significant alternative to the conventional surgical techniques
described hereinabove. Additionally, it is envisaged that the
present endovascular prosthesis may be used in the treatment of
certain aneurysms which are diagnosed as being inoperable. The
present endovascular prosthesis also is believed to provide a
significant advantage of current endovascular approaches such as
the Guglielmi Detachable Coil described hereinabove. Specifically,
since the present endovascular prosthesis does not rely on
insertion into the aneurysm of a metal packing material (e.g.,
platinum coil), the risk of rupturing the aneurysm is mitigated as
is the risk of intra-aneurysmal rearrangement of the metal packing
material and subsequent reappearance of the aneurysm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Embodiments of the present invention will be described with
reference to the accompanying drawings, wherein like reference
numerals denote like elements and in which:
[0044] FIGS. 1-3 illustrate a cross-section of the terminal
bifurcation of the basilar artery into which the present
endovascular prosthesis is being delivered and implanted;
[0045] FIG. 4 is an enlarged sectional view taken along line IV-IV
in FIG. 3;
[0046] FIGS. 5-8 illustrate a perspective view of a preferred
embodiment of the present endovascular prosthesis shown in
schematic;
[0047] FIG. 9 illustrates a perspective view of a particularly
preferred embodiment of the present endovascular prosthesis;
[0048] FIGS. 10-11 illustrate a two-dimensional representation of
one embodiment of the "chevron" effect exhibited in the present
endovascular prosthesis;
[0049] FIGS. 12-13 illustrate a two-dimensional representation of
another embodiment of the "chevron" effect exhibited in the present
endovascular prosthesis;
[0050] FIG. 14 illustrates a first embodiment of an expandable leaf
portion useful in the present endovascular prosthesis;
[0051] FIG. 15 illustrates a second embodiment of an expandable
leaf portion useful in the present endovascular prosthesis; and
[0052] FIGS. 16a and 16b illustrate schematically an embodiment of
steps used to produce an endovascular prosthesis.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] With reference to FIGS. 1-4, a first embodiment of the
present endovascular prosthesis will be described with particular
reference to implantation of same at the terminal bifurcation of
the basilar artery.
[0054] Thus, there is illustrated a basilar artery 10 which
terminates at a junction 15 which bifurcates into pair of secondary
arteries 20,25. Located at junction 15 is an aneurysm 30. Aneurysm
30 has an opening 35 (shown enlarged for illustrative purposes
only) through which blood enters and sustains aneurysm 30.
[0055] An endovascular prosthesis 100 is mounted on a catheter
50.
[0056] Catheter 50 comprises an inflatable balloon 55 and a
guidewire 60. Catheter 50, inflatable balloon 55 and guidewire 60
are conventional. As is known in the art, inflatable balloon 55 is
moveable along guidewire 60.
[0057] Endovascular prosthesis 100 is constructed of a body 105.
Body 105 comprises a proximal end 110 and a distal end 115.
Endovascular prosthesis 100 further comprises an expandable leaf
portion 120 (the second expandable portion) attached to a first
expandable portion 130. As illustrated, leaf portion 120 comprises
a covered portion 125. Endovascular prosthesis 100 further
comprises a third expandable portion 135 connected to the first
expandable portion 130 by a spine 140.
[0058] Body 105 is a generally tubular element and should be
constructed to be sufficiently flexible such that it can be
navigated to the target body passageway yet be sufficiently
expandable such that it can be fixed at the proper location in
target body passageway.
[0059] One approach to achieve this is to construct endovascular
prosthesis 100 from a structure resembling a stent. As is known in
the art, a stent is an expandable prosthesis which is generally
used to obtain and maintain the patency of a body passageway (e.g.,
blood vessels, respiratory ducts, gastrointestinal ducts and the
like). The two general design requirements of a stent are: (i) it
must be sufficiently flexible in the unexpanded state such that it
may be navigated to the target body passageway intact, and (ii) it
must be sufficiently radially rigid in the expanded state to avoid
the occurrence of restenosis and/or stent recoil. The most
preferred embodiment of the present endovascular prosthesis is one
for treating aneurysms and thus, is not a stent, per se, since
design requirement (ii) need not be met--i.e., the aim of the
present endovascular prosthesis is not to maintain patency of
blocked body passageway. Rather, this preferred embodiment of the
present endovascular prosthesis comprises one or more expandable
elements for the purposes of securing the prosthesis in the correct
position. Of course, the novel approach of dual expansion
functionality of the present endovascular prosthesis may be applied
to stents in the appropriate application.
[0060] Thus, in this approach body 105 may be a porous tube having
a porosity defined by a plurality of intersecting members (for
clarity, the porosity of body 105 is not illustrated in FIGS. 1-4).
The precise pattern of the intersecting members is not particularly
restricted and should be chosen to achieve sufficient flexibility
of the porous tube in the unexpanded state while having the
potential to achieve at least some degree of expansion upon the
application of radially outward forces on the tube. Typically, the
plurality of intersecting members will be arranged to define a
regular repeating pattern. See, for example, the various repeating
patterns disclosed in the following copending patent
applications:
[0061] Canadian patent application number 2,134,997 (filed Nov. 3,
1994);
[0062] Canadian patent application number 2,171,047 (filed Mar. 5,
1996);
[0063] Canadian patent application number 2,175,722 (filed May 3,
1996);
[0064] Canadian patent application number 2,185,740 (filed Sep. 17,
1996);
[0065] Canadian patent application number 2,192,520 (Dec. 10,
1996);
[0066] International publication number WO 97/32544 (published Sep.
12, 1997);
[0067] International publication number WO 97/32544 (published Sep.
12, 1997); and
[0068] International publication number WO 97/32545 (published Sep.
12, 1997).
[0069] (hereinafter collectively referred to as the "Divysio patent
applications") and the various references cited therein. While the
repeating patterns disclosed in the Divysio patent applications are
suited for use in stent designs, they may be modified to increase
the flexibility of the tubular structure (e.g., by altering the
polygonal design taught in the Divysio patent application
applications) to be useful in a preferred embodiment of the present
endovascular prosthesis notwithstanding that the resultant tubular
structure may not be advantageously useful as a stent.
[0070] Body 105 may be constructed of any suitable material. In one
preferred embodiment, body 105 is constructed of a plastically
deformable material such as a metal, alloy or polymer. Non-limiting
examples of suitable metals and alloys may be selected from the
group comprising stainless steel, titanium, tantalum and the like.
In this embodiment, the radially outward force used to expand body
105 may be applied by expansion of a catheter-mounted balloon, as
will be discussed in more detail hereinbelow. In another preferred
embodiment, body 105 is constructed of "shape memory" metal alloy
(e.g., nitinol) capable of self-expansion at a temperature of at
least about 30.degree. C., preferably in the range of from about
30.degree. to about 40.degree. C. In this embodiment, it will be
appreciated that an inherent radially outward force causes
expansion of body 105 when it is exposed to an environment at the
programmed self-expansion temperature. In yet another preferred
embodiment, body 105 may be constructed of a biodegradable
material. As is known in the art, a biodegradable material will
degrade upon prolonged contact with body fluids and would be useful
in the present endovascular prosthesis since aneurysm obliteration
may occur within minutes after closing of the aneurysmal
opening.
[0071] The manner by which body 105 is manufactured is not
particularly restricted. Preferably, the body 105 is produced by
laser cutting techniques applied to a tubular starting material.
Thus, the starting material could be a thin-walled tube of a metal,
alloy or polymer as described above which would then have sections
thereof cut out to leave the desired repeating pattern discussed
above. FIGS. 5-8 illustrate how the various elements of
endovascular prosthesis 100 may be cut out of a tubular starting
material (again, for clarity, the specific porosity of body 105 is
not illustrated in FIGS. 5-8).
[0072] In an alternate embodiment, it is possible to construct body
105 having the desired porous repeating pattern from one or more
pre-formed wires. In another alternate embodiment, it is possible
to construct body 105 having the desired porous repeating pattern
using a flat bed laser cutting technique, optionally combined with
a welding technique.
[0073] Endovascular prosthesis 100 may further comprise a coating
material thereon. The coating material may be disposed on the
surface of the prosthesis. Further, the coating may be disposed on
the interior and/or the exterior surface(s) of the prosthesis. The
coating material can be one or more of a biologically inert
material (e.g., to reduce the thrombogenicity of the prosthesis), a
medicinal composition which leaches into the wall of the body
passageway after implantation (e.g., to provide anticoagulant
action, to deliver a pharmaceutical to the body passageway and the
like), and the like.
[0074] Endovascular prosthesis 100 is preferably provided with a
biocompatible coating in order to minimize adverse interaction with
the walls of the body vessel and/or with the liquid, usually blood,
flowing through the vessel. The coating is preferably a polymeric
material, which is generally provided by applying to the prosthesis
a solution or dispersion of preformed polymer in a solvent and
removing the solvent. Non-polymeric coating material may
alternatively be used. Suitable coating materials, for instance
polymers, may be polytetraflouroethylene or silicone rubbers, or
polyurethanes which are known to be biocompatible. Preferably,
however, the polymer has zwitterionic pendant groups, generally
ammonium phosphate ester groups, for instance phosphoryl choline
groups or analogues thereof. Examples of suitable polymers are
described in International Publication Number WO 93/16479. Polymers
described in those specifications are hemo-compatible as well as
generally biocompatible and, in addition, are lubricious. It is
important to ensure that the surfaces of the prosthesis are
completely coated in order to minimize unfavorable interactions,
for instance with blood, which might lead to thrombosis in the
parent vessel.
[0075] This good coating can be achieved by suitable selection of
coating conditions, such as coating solution viscosity, coating
technique and/or solvent removal step.
[0076] With further reference to FIG. 1, once it is desired to
implant endovascular prosthesis 100, it is mounted on balloon 55 of
catheter 50. Guidewire 60 is translated through basilar artery 10
in the direction of arrow A.
[0077] With reference to FIG. 2, endovascular prosthesis 100
mounted on balloon 55 of catheter 50 is navigated to the location
of aneurysm 30 using conventional guidewire and fluoroscopy
techniques. In the illustrated embodiment, distal end 115 of body
105 enters secondary artery 20. In practice, the secondary arteries
at the bifurcation of the basilar artery are asymmetric and distal
end 115 of body 105 is preferably navigated into the larger of the
two secondary arteries. Further, in the illustrated embodiment, as
body 105 is flexed on navigation into secondary artery 20, leaf
portion 120 lifts or moves out of alignment with respect to the
tubular plane of body 105 to define an opening 135.
[0078] With reference to FIGS. 3 and 4, once endovascular
prosthesis 100 is in the correct position, balloon 55 is expanded
thereby exerting radially outward forces on first expandable
portion 130 and third expandable portion 135. Initially, this
results in expansion of body 105 such that a portion of it is urged
against the walls of both of basilar artery 10 and secondary artery
20. This results in expansion of leaf portion 120 as will be
described in further detail hereinbelow. In the embodiment
illustrated in FIG. 3, balloon 55 is expanded to a degree whereby
leaf portion 120 expands and is urged against the walls of
secondary arteries 20,25 in a manner which results in blocking of
opening 35 of aneurysm 30.
[0079] With reference to FIG. 4, balloon 55 is deflated and,
together with guidewire 60, withdrawn from endovascular prosthesis
100. In the illustrated embodiment, endovascular prosthesis 100 is
secured in position by first expandable portion 130 and third
expandable portion 135 being urged against the walls of basilar
artery 10 and secondary artery 20. Further, in the illustrated
embodiment, leaf portion 120 is secured in position by a
combination of forces against it by the flow of the blood and the
inherent forces upon flexure of body 105 to navigate distal end 115
into secondary artery 20. Once leaf portion 120 blocks opening 35,
aneurysm 30 is obliterated thereafter.
[0080] With reference to FIGS. 9-11, there is illustrated a
particularly preferred embodiment of present endovascular
prosthesis 100. Endovascular prosthesis 100, as illustrated, is
produced by etching the illustrated design from a thin-walled tube
constructed of a plastically deformable material (e.g., stainless
steel). As shown a single spine 140 is all that interconnects first
expandable region 130 and third expandable region 135.
[0081] With reference to FIGS. 10-11, the "chevron" function of
leaf portion 120 (the second expandable region) is illustrated.
Thus, leaf portion 120 comprises a series of longitudinals 150,
151, 152 which are substantially parallel to one another.
Longitudinals 150, 151, 152 are interconnected by pairs of struts
155a/156a, 155b/156b, 155c/156c, 155d/156d and 155e/156e. As will
be apparent, struts 155/156 meet at an intersection point (at
longitudinal 151) to define an acute angle.
[0082] Longitudinals 150, 151, 152 are connected to a
circumferential strut 131 comprised in first expandable portion
130. As shown, in two dimensions, strut 131 has a sinusoidal (or
wave-like or undulating or meandering) design. As will be apparent
to those of skill in the art, the sinusoidal design of strut 131
defines, in two dimensions, a convex apex 132 and a concave apex
133. As used throughout this specification, the term "concave apex"
is intended to mean an apex which is directed into first expandable
portion 130 and term "convex apex" is intended to mean an apex
which is directed away from first expandable portion 130. In the
illustrated embodiment, strut 131 comprises a plurality of
alternating convex apices 132 and concave apices 133. As shown,
longitudinals 150 and 152 are connected to convex apices 132, and
longitudinal 151 is connected to concave apex 133.
[0083] When first expandable portion 130 is expanded as described
hereinabove, this results in radial expansion of circumferential
strut 131. Thus, as first expandable portion 130 expands
circumferential strut 131 is stretched in the direction of arrows B
resulting in substantial straightening of strut 131. Straightening
of strut 131 results in movement of longitudinals 150 and 152 in
the direction of arrows C (i.e., pulling in toward strut 131) and
in movement of longitudinal 151 in the direction of arrow D (i.e.,
pushing away from strut 131). At the same time, the acute angle
formed between struts 155/156 opens up such, in the optimum case
(FIG. 11), struts 155/156 are collinear.
[0084] As will be apparent to those of skill in the art, the
surface area of expanded leaf portion 120 (FIG. 11) is greater than
that of unexpanded leaf portion 120 (FIG. 10). Thus, it can be
appreciated that the present endovascular prosthesis, having a
given tubular dimension, has a leaf portion which, upon expansion,
will have a surface area greater than the surface area of a leaf
portion having the same tubular dimension but which simply opens
(i.e., it uncurls but does not expand, per se) during
deployment.
[0085] For clarity, the description above with reference to FIGS.
9-11 does not include covered portion 125. In practice, it is
preferred that most or all of leaf portion 120 is covered with a
material suitable to: (i) withstand expansion of leaf portion 120,
and (ii) block the opening 35 of aneurysm 30 after deployment. The
nature of the material used for this purpose is not particularly
restricted. Preferably, the material comprises a silicone-based
material from NuSil Technology (Carpenteria, Calif.). A
particularly preferred covering material is derived from a
silicone-based dispersion commercially available from NuSil
Technology under trade name MED-6640. This material is usually
obtained as a liquid dispersion in an organic insolvent such as
xylene. The dispersion may be used as such or the viscosity thereof
may be altered as desired by addition of further solvent.
[0086] When it is desired to coat leaf portion 120, endovascular
prosthesis 100 is partially expanded by an suitable means such as a
balloon, tapered mandrel and the like. If endovascular prosthesis
100 is constructed from a plastically deformable material (e.g.,
stainless steel), it is particularly preferred to only partially
pre-expand endovascular prosthesis 100 since this will facilitate
compression thereof to its original configuration. Practically, the
present inventors have found that the sufficient pre-expansion is
achieved once a point of plastic deformation has been reached (for
more general information on plastic deformation, reference can be
made to International publication number WO 00/07522). In many
cases, this will involve pre-expansion of endovascular prosthesis
100 to greater than 50% of its final expanded, preferably from
about 60% to about 70% of its final expanded state.
[0087] At this point, partially expanded leaf portion 120 is coated
with a covering material such as a silicone-based dispersion
described above. This involves immersing partially expanded leaf
portion 120 in the dispersion followed by carrying of the
dispersion to result in adhesion of the covering material to leaf
portion 120. Once a suitable coating has been disposed over leaf
portion 120, partially pre-expanded prosthesis 100 is compressed,
preferably to its original configuration. This may be achieved, for
example, by the arrangement shown in FIGS. 16a and 16b. Thus, with
reference to FIG. 16a, partially pre-expanded prosthesis 100 is
disposed between a pair of plates 250,255. Disposed within
partially expanded prosthesis 100 is a mandrel 260 having a cross
sectional shape similar to that of prosthesis 100 prior to
pre-expansion thereof.
[0088] At this point, plate 250 is moved in the direction of arrows
G which results in compression of prosthesis 100 in the direction
of arrows H. The net result of the compression is illustrated in
FIG. 16b wherein prosthesis 100 has been compressed substantially
to its original configuration.
[0089] The arrangement in FIGS. 16a and 16b is particularly
advantageous since it results in compression of the partially
expanded prosthesis to a configuration similar to the unexpanded
prosthesis without overlap of the leaf portion with either of the
body portions. The nature of plates 250,255 is not particularly
restricted provided that interaction of the plates with partially
expanded prosthesis 100 create sufficient friction to obviate or
mitigate slippage of the plates over the prosthesis. This can be
achieved by using a silicone coating on the plates and/or by slight
roughening of the surfaces, as appropriate.
[0090] The covered leaf portion 120 may then be sterilized with
ethylene-oxide. For more information about this approach, see "In
Vivo Evaluation of Porous Versus Skinned
Polyurethane-Polydimethylsiloxane Small Diameter Vascular Grafts"
by Okoshi et al., ASAIO Transactions 1991; 37: M480-M481.
[0091] In FIGS. 12 and 13 there is illustrated a variation to leaf
portion 120 illustrated in FIGS. 10 and 11 (Note: like reference
numerals in FIGS. 10-13 are intended to denote like elements and
vice versa). Thus, as illustrated, the variation in FIGS. 12 and 13
comprises an extra pair of longitudinals 153, 154. Longitudinals
150 and 153 are interconnected by a plurality of struts 160a, 160b,
160c, 160d, 160e, etc. Similarly, longitudinals 152 and 154 are
interconnected by a plurality of struts 161a, 161b, 161c, 161d,
161e, etc. As shown longitudinals 153, 154 are not directly
connected to circumferential strut 131. This facilitates
independent movement of leaf portion 120 with respect to first
expandable portion 130 as discussed hereinabove while optimizing
the surface area of leaf portion 120 in the expanded state (FIG.
13). Further, it can be seen that struts 160a, 161a are bent (or
angled) in the unexpanded state of leaf portion 120 (FIG. 12). This
facilitates expansion of leaf portion 120 as shown in FIG. 13.
[0092] In FIG. 14, there is illustrated a variation to leaf portion
120 illustrated in FIGS. 10 and 11 (Note: like reference numerals
in FIGS. 10, 11 and 14 are intended to denote like elements and
vice versa). One variation in the leaf portion illustrated in FIG.
14 is the provision of longitudinal struts 150a and 152a which are
thinner than longitudinals 150 and 152, respectively, and
longitudinal 151. This variation serves to substantially equalize
the stress developed in struts 150a and 152a in the direction of
arrow C with the force applied to longitudinal 151 in the direction
of arrow D. Further, a series of connections 170 between
longitudinals 150, 151, 152 and struts 155(a,b,c,d) and
156(a,b,c,d) have been modified to be thinner and of a larger
internal radius. This variation serves to facilitate bending of
connections 170 and opening or expansion of the leaf portion.
[0093] A covering material may be disposed over the leaf portions
illustrated in FIGS. 12-14 using the procedure set out above in the
description of covering the leaf portion illustrated in FIGS.
9-11.
[0094] With reference to FIG. 15, there is illustrated a variation
to the leaf portion illustrated in FIGS. 10-14.
[0095] As shown, FIG. 15 illustrates a two dimensional
representation of a preferred embodiment of the present
endovascular prosthesis 200. Prosthesis 200 comprises a first
expandable portion 205 and a second expandable portion 210. First
expandable portion 205 and second expandable portion 210 are
interconnected by struts 214,216 and spines 215,217.
[0096] In the illustrated embodiment, first expandable portion 205
and second expandable portion 210 each have a porous surface
defined by a series of interconnected members which form a pattern
similar to the patterns disclosed in the Divysio patent application
referred to hereinabove.
[0097] Endovascular prosthesis 200 comprises a leaf portion 220.
Leaf portion 220 comprises a pair of jaw members 225,230. Jaw
members 225,230 each comprise a surface which has microcuts
disposed therein. Such microcuts may be disposed in jaw members
225,230 by a conventional laser cutting technique or the like.
[0098] Jaw members 225,230 are interconnected to one another at one
end thereof by a connection member 235. Further, jaw member 225 is
connected to spine 215 via a strut 218. Similarly, jaw member 230
is connected to spine 217 via a strut 219. As illustrated, strut
218 also serves to interconnect jaw member 225 and strut 216.
Similarly, strut 219 also serves to interconnect jaw member 230 and
strut 216.
[0099] When second expandable portion 210 is expanded as described
hereinabove, a connection strut 240 interconnecting a junction 241
between jaw members 225,230 and second expandable portion 210
results in movement of connecting strut 240 in the direction of
arrow E (i.e., pushing junction 241 toward connecting member 235).
Concurrently, struts 218,219 pull on jaw members 225,230 in the
direction of arrows F such that jaw members 225,230 pivot about
junction 241 with the result that connection member 235 unfolds or
opens up.
[0100] Attached to jaw members 225,230 is a cover material (not
shown for clarity) which, upon expansion of jaw members 225,230
unfolds to optimize the surface area of leaf portion 220.
[0101] The nature of the coating material is not particularly
restricted provided it is biomedical in nature (i.e., it can be
safely delivered to and retained in a lumen) and may be of the type
of coating material in connection with the embodiments described
hereinabove. The coating material may be stretchable (as described
hereinabove) or non-stretchable. The coating material may be
Dacron.TM., Goretex.TM. and the like. The coating material may be
stitched to jaw members 225,230. Alternatively, the coating
material may be adhered to jaw members 225,230. The particular
method of securing the coating layer to jaw members 225,230 is not
particularly restricted.
[0102] The coating material may be applied to jaw members 225,230
prior to expansion of leaf portion 220. Alternatively, it is
possible to partially or fully pre-expand leaf portion 220, apply
the coating material and thereafter crimp or otherwise return leaf
portion 220 to a suitable predeployment state.
[0103] The preferred embodiment of endovascular prosthesis 200
illustrated in FIG. 15 is particularly advantageous since it allows
expansion of leaf portion 220 without the requirement that a force
necessary to stretch a coating material be applied (contrast this
with the embodiments illustrated in FIGS. 9-14).
[0104] Further, the provision of spines 215,217 in endovascular
prosthesis 200 serve the additional benefit of conferring
"preferential flexibility" to expandable prosthesis 200. This
preferential flexibility tends to maintain leaf portion 220 on the
outside of an arc described by the flexed prosthesis and helps urge
leaf portion 220 into position against the neck of the
aneurysm.
[0105] In the illustrated embodiment of FIG. 15, leaf portion 220
is expanded by the concurrent "pushing" action of connecting strut
240 and "pulling" actions of struts 218,219 described above. Those
of skill in the art will of course appreciate that, in some cases,
it may be possible to modify the illustrated embodiment to achieve
expansion of leaf portion 220 with either "pushing" or "pulling" as
described, or even by some other action.
[0106] In this and the foregoing illustrated embodiments of the
present endovascular prosthesis, it is possible, and even preferred
in some cases, to use tabs or similar devices on the edge of the
leaf portion to obviate lifting of the leaf from the catheter or
other delivery system used to deliver the prosthesis. Such tabs may
increase the circumferential wrap around the balloon allowing the
leaf portion to maintain a low profile along the length of the
balloon during delivery of the device. These tabs may be simply
designed to "break away" or otherwise release the leaf portion from
the balloon (e.g., during deployment of the prosthesis) to achieve
the benefits described above.
[0107] Other variations and modifications of the specific
embodiments described hereinabove which do not depart from the
scope and spirit of the invention will be immediately apparent to
those of skill in the art having this specification in hand. For
example, while in various of the illustrated embodiments, the leaf
portion is shown pointing toward the proximal end of the prosthesis
during delivery, this is not essential and, in some cases, a
reverse orientation may be preferred. Further, while in various of
the illustrated embodiments, an endovascular prosthesis to treat a
brain aneurysms is shown, it will be apparent to those of skill in
the art that the present endovascular prosthesis may be
advantageously used to treat other types of aneurysms and used in
other (non-aneurysm) endovascular applications. Still further,
while in various of the illustrated embodiments, a pair of
expandable, annular rings is shown, it is possible to construct the
prosthesis using a single expandable annular ring or 3 or more
expandable annular rings. Still further, while in various of the
illustrated embodiments, the expansible portion of the body
comprises a pair of rings having a porous structure, it is possible
to use rings having a non-porous structure, for example, by folding
down the rings and maintaining them in this state using a removable
mechanical restraint which, when removed, allows the rings to
unfold into a deployed state (in this embodiment, the rings would
be dimensioned to their final implanted diameter and then folded
down--see for example, International Publication Number WO
95/26695). Other modifications which do not deviated from the
spirit and scope of the invention will be immediately apparent to
those of skill in the art having the present specification in
hand.
[0108] While this invention has been described with reference to
illustrative embodiments and examples, the description is not
intended to be construed in a limiting sense. Thus, various
modifications of the illustrative embodiments, as well as other
embodiments of the invention, will be apparent to persons skilled
in the art upon reference to this description. It is therefore
contemplated that the appended claims will cover any such
modifications or embodiments.
[0109] All publications, patents and patent applications referred
to herein are incorporated by reference in their entirety to the
same extent as if each individual publication, patent or patent
application was specifically and individually indicated to be
incorporated by reference in its entirety.
* * * * *