U.S. patent application number 10/216356 was filed with the patent office on 2003-05-29 for implantable intraluminal device and method of using same in treating aneurysms.
This patent application is currently assigned to MindGuard Ltd.. Invention is credited to Grad, Ygael, Lieber, Baruch, Nishri, Boaz, Yodfat, Ofer.
Application Number | 20030100945 10/216356 |
Document ID | / |
Family ID | 26910931 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030100945 |
Kind Code |
A1 |
Yodfat, Ofer ; et
al. |
May 29, 2003 |
Implantable intraluminal device and method of using same in
treating aneurysms
Abstract
An intraluminal device implantable in a blood vessel having an
aneurysm therein in the vicinity of a perforating vessel and/or of
a bifurcation leading to a branch vessel. The intraluminal device
includes a mesh-like tube of bio-compatible material having an
expanded condition in which the tube diameter is slightly larger
than the diameter of the blood vessel in which it is to be
implanted, and the tube length is sufficient to straddle the
aneurysm and to be anchored to the blood vessel on the opposite
sides of the aneurysm. The mesh-like tube also has a contracted
condition wherein it is sufficiently flexible so as to be easily
manipulatable through the blood vessel to straddle the aneurysm. In
its expanded condition, the mesh-like tube has a porosity index of
55%-80% such as to reduce the flow of blood through its wall to the
aneurysm sufficiently to decrease the possibility of rupture of the
aneurysm but not to unduly reduce the blood flow to a perforating
or branch vessel to the degree likely to cause significant damage
to tissues supplied with blood by such perforating or branch
vessel.
Inventors: |
Yodfat, Ofer; (Modi'in,
IL) ; Lieber, Baruch; (Coral Gables, FL) ;
Grad, Ygael; (Tel Aviv, IL) ; Nishri, Boaz;
(Maagan Michael, IL) |
Correspondence
Address: |
G.E. EHRLICH (1995) LTD.
c/o ANTHONY CASTORINA
SUITE 207
2001 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
MindGuard Ltd.
|
Family ID: |
26910931 |
Appl. No.: |
10/216356 |
Filed: |
August 12, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60332013 |
Nov 23, 2001 |
|
|
|
Current U.S.
Class: |
623/1.53 ;
623/1.15; 623/903 |
Current CPC
Class: |
A61F 2/82 20130101; A61F
2/90 20130101; A61F 2002/821 20130101; A61F 2002/823 20130101; A61F
2/07 20130101; A61F 2002/068 20130101; A61F 2250/0023 20130101;
Y10S 623/909 20130101; A61F 2002/065 20130101 |
Class at
Publication: |
623/1.53 ;
623/1.15; 623/903 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. An intraluminal device implantable in a blood vessel having an
aneurysm therein in the vicinity of a perforating vessel, and/or of
a bifurcation leading to a branch vessel, said device comprising: a
mesh-like tube of bio-compatible material having an expanded
condition in which the tube diameter is slightly larger than the
diameter of the blood vessel in which it is to be implanted, and
the tube length is sufficient to straddle said aneurysm and to be
anchored to the blood vessel on the opposite sides of said
aneurysm; said mesh-like tube also having a contracted condition
wherein it is sufficiently flexible so as to be easily
manipulatable through the blood vessel to straddle the aneurysm;
said mesh-like tube, in its expanded condition, having a porosity
index of 50%-85% such as to reduce the flow of blood through a wall
of the mesh-like tube to the aneurysm sufficiently to decrease the
possibility of rupture of the aneurysm but not to unduly reduce the
blood flow to a perforating or branch vessel to the degree likely
to cause significant damage to tissues supplied with blood by such
perforating or branch vessel.
2. The device according to claim 1, wherein said mesh-like tube
includes windows having an inscribed diameter of 30-480 .mu.m in
the expanded condition of the mesh-like tube.
3. The device according to claim 2, wherein said inscribed diameter
is 50-320 .mu.m in the expanded condition of the mesh-like
tube.
4. The device according to claim 1, wherein the length of said
mesh-like tube in its expanded condition is 5-60 mm.
5. The device according to claim 1, wherein said mesh-like tube
includes a plurality of filaments of bio-compatible material
extending helically in an interlaced manner in opposite directions
so as to form a braided tube.
6. The device according to claim 5, wherein said filaments define
windows producing a porosity index of 60-75% in the expanded
condition of said braided tube.
7. The device according to claim 5, wherein at least most of said
filaments are of circular cross-section and have a diameter of less
than 60 .mu.m.
8. The device according to claim 2, wherein at least most of said
filaments have a diameter of 20-40 .mu.m.
9. The device according to claim 5, wherein at least most of said
filaments are of non-circular cross-section and have a
circumference of 40-180 .mu.m.
10. The device according to claim 5, wherein said braided tube is
formed of 24-144 of said filaments.
11. The device according to claim 5, wherein said braided tube is
formed of 62-120 of said filaments.
12. The device according to claim 5, wherein said braided tube has
a braiding angle in the range of 20.degree.-150.degree. in the
expanded condition of the braided tube.
13. The device according to claim 5, wherein said filaments are of
circular cross-section, have a diameter of 20-40 .mu.m, define
windows having an inscribed diameter of 30-480 .mu.m in the
expanded condition of the braided tube, and number 24-144 to form
the braided tube.
14. The device according to claim 5, wherein said filaments are of
circular cross-section, define windows having an inscribed diameter
of 50-320 .mu.m and a braiding angle of 20.degree.-150.degree. in
the expanded condition of the braided tube, and number 62-120 to
form the braided tube.
15. A method of treating an aneurysm in a blood vessel which may
also have in the vicinity of the aneurysm, one or more perforating
vessel and/or a bifurcation leading to a branch vessel, comprising:
deploying in the blood vessel an intraluminal device according to
claim 1 of a diameter and length such that, when in its expanded
condition, it is anchored to said blood vessel and straddles said
aneurysm.
Description
RELATED APPLICATION
[0001] The present invention is related to Provisional Application
No. 60/332,013 filed 23 Nov. 2001, the contents of which are
incorporated herein by reference, and claims the priority date of
that application.
FIELD OF THE INVENTION
[0002] The present invention relates to intraluminal devices
implantable in a blood vessel for the treatment of aneurysms
especially brain aneurysms. The invention also relates to methods
of treating aneurysms using such intraluminal devices.
BACKGROUND OF THE INVENTION
[0003] A number of publications as listed at the end of this
specification are incorporated herein by reference in their
entireties for background information and are numerically
referenced in the following text:
[0004] Intracranial aneurysms are the main cause of nontraumatic
subarachnoid hemorrhage and are responsible for about 25% of all
deaths relating to cerebrovascular events. Autopsy studies show
that the overall frequency of intracranial aneurysms in the general
population is approximately 5 percent and suggest that 10 to 15
million persons in the United States have or will have intracranial
aneurysms [1]. In approximately 15,000 cases (6 cases per 100,000
persons per year), intracranial aneurysms rupture every year in
North America [2]. Rupture of intracranial aneurysms leads to
subarachnoid aneurysmal hemorrhage (SAH) which has a 30-day
mortality rate of 45%, and results in approximately half the
survivors sustaining irreversible brain damage [1, 2].
[0005] The primary goal of treatments for intracranial aneurysm is
prevention of the rupture of the aneurysms, thereby preventing
bleeding or rebleeding. At the present time, three general methods
of treatment exist. These can be grouped according to their
approach: extravascular, endovascular, and extra-endovascular.
[0006] The extravascular approach involves surgery or microsurgery
of the aneurysm. One surgical procedure is to apply a metallic clip
or a suture-ligation across the artery feeding the aneurysm (neck),
thereby allowing the aneurysm to clot off and hopefully shrink.
Another surgical procedure is to "surgically reconstruct" the
aneurysmal portion of the artery, by surgically cut out the
aneurysm and repairing the vessel by using a natural or synthetic
vessel graft. Both of these surgical procedures typically require
general anesthesia, craniotomy, brain retraction, and dissection of
the arachnoid around the neck of the aneurysm.
[0007] Surgical treatment of vascular intracranial aneurysm is
accompanied by a mortality rate of 3.8% and a morbidity rate of
10.9% [3]. Because of the high mortality and morbidity rates, and
because the condition of many patients does not permit them to
undergo an open operation, the surgical procedure is often delayed
or not practical. For this reason the prior art has sought
alternative means of treatment.
[0008] The development of microcatheters made possible the use of
endovascular (catheter-based) procedures. The major advantage of
the endovascular procedures is that they do not require the use of
open surgery. They are generally more beneficial and have much
lower mortality and morbidity rates than the extravascular
procedures.
[0009] Many variations of endovascular procedures exist of which
some of the more important are the following:
[0010] 1. Placement of embolic material, such as metallic
microcoils or spherical beads, inside the aneurysm sac in order to
form a mass within this sac which will slow the blood flow and
generally encourage the aneurysm to clot off and to shrink. To
accomplish this procedure, a microcatheter is guided through the
cerebral arteries until the site of the aneurysm is reached. The
distal tip of the microcatheter is than placed within the sac of
the aneurysm, and the embolic material is injected into the sac of
the aneurysm. Typical microcatheters suitable for this procedure
are disclosed in U.S. Pat. Nos. 5,853,418; 6,066,133; 6,165,198 and
6,168,592.
[0011] Widespread, long-term experience with this technique has
shown several risks and limitations. The method has 4% morbidity
and 1% mortality rate and achieves complete aneurysm occlusion in
only 52% to 78% of the cases in which it is employed. The
relatively low success rate is due to technical limitations (e.g.,
coil flexibility, shape, and dimensions) which prevent tight
packing of the sac of the aneurysm, especially aneurysms with wide
necks [3]. Other difficulties are associated with the presence of
preexisting thrombus within the aneurysm cavity, which may be
sheared off into the parent trunk leading to parent artery
occlusion. Also aneurysm perforation may occur during placement of
coils into the aneurysm. Additionally, occurrence of coil movement
and compaction may foster aneurysm revascularization or growth.
[0012] 2. Another endovascular technique for treating aneurysms
involves inserting a detachable balloon into the sac of the
aneurysm using a microcatheter. The detachable balloon is then
inflated using embolic material, such as a liquid polymer material
or microcoils. The balloon is then detached from the microcatheter
and left within the sac of the aneurysm in an attempt to fill the
sac and to form a thrombotic mass inside the aneurysm.
[0013] One of the disadvantages of this method is that detachable
balloons, when inflated, typically do not conform to the interior
configuration of the aneurysm sac. Instead, the aneurysm sac is
forced to conform to the exterior surface of the detachable
balloon. Thus, there is an increased risk that the detachable
balloon will rupture the sac of the aneurysm.
[0014] 3. Stent technology has been applied to the intracranial
vasculature. The use of this technology has been limited until
recently by the lack of available stents and stent delivery systems
capable of safe and effective navigation through the intercranial
vessels. The use of such stents is particularly difficult with
respect to aneurysms in head blood vessels because of the number of
perforating vessels in such blood vessels, and thereby the
increased danger that one or more perforating vessels may be in the
vicinity of such an aneurysm. The same is true with respect to
bifurcations of a blood vessel splitting into one or more branch
vessels, which may also be in the vicinity of an aneurysm. Where
the blood supply to an aneurysm is to be reduced, it is critical
that the blood supply to such perforating vessel or branch vessels,
in the vicinity of the aneurysm not be unduly reduced to the degree
causing damage to the tissues supplied with blood by such
perforating or branch vessels.
[0015] Thus, there is a serious danger that the placement of a
conventional endovascular stent within the parent artery across the
aneurysm neck to reduce blood flow to the aneurysm, to promote
intra-aneurysm stasis and thrombosis [4,5].
[0016] Stents having portions of different permeabilities are
disclosed, for example, in McCrory U.S. Pat. No. 5,951,599, Brown
et al U.S. Pat. No. 6,093,199, Wallsten U.S. Pat. No. 4,954,126,
and Dubrul U.S. Pat. No. 6,258,115.
[0017] The McCrory patent discloses a braided stent having a first
portion with a relatively high porosity index so as to be highly
permeable to blood flow, and a second portion of lower porosity
index so as to be less permeable to blood flow. When the stent is
deployed, the portion of low permeability is located to overlie the
neck of the aneurysm, and the portion of high permeability is
spaced from the neck of the aneurysm. A braided stent construction
with different porosities is also disclosed in the Dubrul
patent.
[0018] Brown et al, on the other hand, discloses an intraluminal
device or stent comprising a diverter, in the form of a
low-permeability foam pad, to overlie the neck of the aneurysm,
straddled on its opposite sides by a pair of high-permeability coil
elements for anchoring the device in the blood vessel.
[0019] Wallsten U.S. Pat. No. 4,954,126, discloses a braided tube
intraluminal device for use in various applications, one of which
applications is to apply a graft to treat an aneurysm (FIG. 9). In
this case, the complete braided tube would have high permeability
with respect to blood flow therethrough since its function is to
mount the grafts, but the graft would have low-permeability to
decrease the possibility of rupture of the aneurysm.
[0020] Delivery devices for stents for use in the intracranial
vasculature are well known at the art. Typical devices are
disclosed, for example, in the following U.S. Pat. Nos. 5,496,275;
5,676,659; and 6,254,628. The blood vessels in the brain are
frequently as small as several millimeters, requiring that the
catheters have an outside diameter as small as 2-8 French (0.66 mm
to 2.64 mm).
[0021] Technically it is very difficult to produce and accurately
deploy the stents described in the above McCrory, Brown et al and
Wallsten patents for treating aneurysms by using presently
available delivery systems. The difficulties include not only in
producing such stents of different permeabilities, but also in
deploying them such that the portion of low permeability is exactly
aligned with the aneurysm neck. When the device is to be implanted
in a blood vessel having an aneurysm at or proximate to a
perforating vessel or a bifurcation leading to a branch vessel, the
portion of high permeability must be precisely located at the
perforating or branch vessels in order to maintain patency in the
perforating or branch vessels. Additionally, particularly in
tortuous, ectatic vessels, existing stiff stents are difficult to
introduce and may results in kinking such as to cause the failure
of the deployment process.
[0022] For these reasons it is apparent that there is a need for a
better intraluminal device to treat an aneurysm, particularly an
intracranial aneurysm.
OBJECTS AND BRIEF SUMMARY OF THE INVENTION
[0023] An object of the present invention is to provide an
intraluminal device having advantages in one or more of the above
respects for implantation in a blood vessel having an aneurysm in
order to treat the aneurysm. Another object of the invention is to
provide such an intraluminal device particularly useful for
implantation in a blood vessel having an aneurysms at or proximate
to one or more perforating vessels and/or a bifurcation leading to
a branch vessel such as to reduce the blood flow to the aneurysms
while still maintaining patency in the perforating and/or branch
vessels.
[0024] Another object of the invention is to provide an implantable
intraluminal device for treating aneurysms in the intracranial
vasculature that is sufficiently flexible and pliable so that it
can be delivered easily to an intracranial site, deployed
accurately, and then left in position to accomplish its
purpose.
[0025] A further object of the invention is to provide a method of
treating aneurysms by using intraluminal devices having the above
features.
[0026] According to the present invention, there is provided an
intraluminal device implantable in a blood vessel having an
aneurysm therein in the vicinity of a perforating vessel, and/or of
a bifurcation leading to a branch vessel, the device comprising: a
mesh-like tube of bio-compatible material having an expanded
condition in which the tube diameter is slightly larger than the
diameter of the blood vessel in which it is to be implanted, and
the tube length is sufficient to straddle the aneurysm and to be
anchored to the blood vessel on the opposite sides of the aneurysm;
the mesh-like tube also having a contracted condition wherein it is
sufficiently flexible so as to be easily manipulatable through the
blood vessel to straddle the aneurysm; the mesh-like tube, in its
expanded condition, having a porosity index of 55%-80% such as to
reduce the flow of blood through a wall of the mesh-like tube to
the aneurysm sufficiently to decrease the possibility of rupture of
the aneurysm but not to unduly reduce the blood flow to a
perforating or branch vessel to the degree likely to cause
significant damage to tissues supplied with blood by such
perforating or branch vessel.
[0027] Experimental evidence indicates that patency can be
maintained and ischemia and infarction can be prevented if less
than 50% of the ostial diameter is occluded [6].
[0028] In the described preferred embodiments, the windows in the
mesh-like tube produce a porosity index of 50%-85%, preferably
60%-75%. The porosity index (P.E.) is defined by the relation: 1 P
. E . = 1 - Sm St
[0029] wherein: "Sm" is the actual surface covered by the mesh-like
tube, and "St" is the total surface area of the mesh-like tube. The
porosity index of the existing typical stents is well above 80%. In
the tube devices of the present invention, however, the porosity
index is not more than 85%, preferably 55-80%, more preferably
60-75%.
[0030] In the described preferred embodiments, the mesh-like tube
includes windows having an inscribed diameter of 30-480 .mu.m,
preferably 50-320 .mu.m, in the expanded condition of the mesh-like
tube.
[0031] According to the described preferred embodiments, the
mesh-like tube includes a plurality of filaments of bio-compatible
material extending helically in an interlaced manner in opposite
directions so as to form a braided tube. It is contemplated,
however, that other mesh-like structures could be used, such as
woven or knitted tubes.
[0032] A maximum porosity index is attained when the braiding
angle, in the expanded condition of the braided tube, is
90.degree.. However, decreasing the braiding angle below 90.degree.
increases the radial force applied by the braided tube against the
inner surface of the blood vessel and decreases the P.E. In cases,
where low radial force is needed, the desirable low P.E. can be
achieved by increasing or decreasing the braiding angle, as
described below with respect to specific examples. Preferably, the
braided tube has a braiding angle in the range of 20%-150% in the
expanded condition of the braided tube.
[0033] Also in the described preferred embodiments, the filaments,
or at least most of them, are of circular cross-section and have a
diameter of 10-60 .mu.m, preferably 20-40 .mu.m. The filaments
could also be of non-circular cross-section, such as of square or
rectangular cross-section, in which case it is preferred that they
have a circumference of 40-180 .mu.m. It is also possible to use
combination of several filament diameters and filament materials in
one device to achieve structural stability and/or desired
radio-opacity characteristic. Preferably the braid is formed of
24-144 filaments, more preferably 62-120 filaments. The filaments
may be of a suitable bio-compatible material, metal or plastic, and
may include a drug or other biological coating or cladding.
[0034] According to another aspect of the present invention, there
is provided a method of treating an aneurysm in a blood vessel,
which may be proximate to one or more perforating vessels and/or to
a bifurcation leading to a branch vessel, by using intraluminal
devices having the above combination of features.
[0035] As will be described more particularly below, intraluminal
devices constructed in accordance with the foregoing features show
great promise in the treatment of aneurysms in general, and brain
aneurysms in particular, since they are relatively easily
manipulatable through the blood vessel to the implantation site,
and when deployed in their expanded condition in the implantation
site, they reduce the flow of blood to the aneurysm sufficiently to
decrease the possibility of rupture thereof, while maintaining
patency in any perforating or branch vessels in the vicinity of the
aneurysm.
[0036] Further features and advantages of the invention will be
apparent from the description below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The invention is herein described, by way of example only,
with reference to the accompanying drawings, wherein:
[0038] FIGS. 1a and 1b are side and end view, respectively,
illustrating one form of intraluminal device constructed in
accordance with the present invention, the device being shown in
its normal, expanded condition;
[0039] FIGS. 2a and 2b are corresponding views but illustrating the
device in its contracted, stressed condition;
[0040] FIG. 3 more particularly illustrates the braid pattern of
FIGS. 1a, 1b and 2a, 2b in the expanded condition of the braided
tube;
[0041] FIG. 4 illustrates another braid pattern, wherein one
filament extending in one helical direction is interwoven over and
under two filaments extending in the opposite helical
direction;
[0042] FIG. 5 illustrates a further braid pattern in which two (or
more) filaments extending helically in one direction are interwoven
over and under two (or more) filaments extending in the opposite
direction;
[0043] FIG. 6 schematically shows the relationship between the
bending rigidity of the braided tube with respect to the diameter
of the filaments producing the braided tube;
[0044] FIG. 7 schematically illustrates an intraluminal device
implanted in a blood vessel having a plurality of perforating
vessels in the vicinity of an aneurysm; and
[0045] FIGS. 8, 9, and 10 illustrate various manners in which an
intraluminal device constructed in accordance with the present
invention may be implanted in a blood vessel having an aneurysm at
or proximate to a bifurcation leading to one or more branch
vessels.
[0046] It is to be understood that the drawings and the description
below are provided primarily for purposes of facilitating
understanding the conceptual aspects of the invention and various
possible embodiments thereof, including what is presently
considered to be preferred embodiments. In the interest of clarity
and brevity, no attempt is made to provide more details than
necessary to enable one skilled in the art, using routine skill and
design, to understand and practice the described invention. It is
to be further understood that the embodiments described are for
purposes of example only, and that the invention is capable of
being embodied in other forms and applications than described
herein.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0047] FIGS. 1a and 1b illustrate an intraluminal device, therein
generally designated 2, constructed in accordance with the present
invention in its normal or expanded condition which it assumes in a
blood vessel after deployment therein; whereas FIGS. 2a and 2b
illustrate the intraluminal device 2 of FIGS. 1a and 1b in the
contracted or stressed condition of the device which assumes to
facilitate its manipulation through the blood vessel to the
deployment site.
[0048] As shown particularly in FIG. 1, the intraluminal device
includes a plurality of filaments of elastic and non-elastic
bio-compatible material, metal or plastic, extending helically in
an interlaced manner to define a braided tube. Thus, shown in FIG.
1a are a first group of filaments 3 extending helically in one
direction, and a second group of filaments 4 extending helically in
the opposite direction, with the two groups of filaments being
interwoven such that a filament 3 overlies a filament 4 at some
points as shown at 5, and underlies a filament 4 at other points as
shown at 6.
[0049] Filaments 3 and 4 thus define a braided tube having a
plurality of windows 7. The inscribed diameter and the length of
each window are shown at W.sub.d and W.sub.L, respectively, in the
normal, expanded condition of the braided tube. These
characteristics depend on, among other factors, the number of
filaments and the braiding angle ".alpha." at the cross-over points
of the two groups of filaments 3, 4.
[0050] FIG. 3 more particularly illustrates the above-described
braid pattern in the expanded condition of the braided tube. Thus,
as shown in FIG. 3, each filament 3a extending helically in one
direction and is interwoven with one filament 4a extending
helically in the opposite direction. Such a braid pattern is
sometimes called a "one over one" pattern. FIG. 4 illustrates a
"one over two" pattern, in which each filament 3b extending
helically in one direction is interwoven with two filaments 4b
extending helically in the opposite direction. FIG. 5 illustrates a
further braid pattern that may be used, in which two (or more)
filaments 3c extending helically in one direction are interwoven
with two (or more) filaments 4c extending helically in the opposite
direction.
[0051] The braid pattern illustrated in FIG. 3 is of highest
flexibility, whereas that illustrated in FIG. 5 is of lower
flexibility but of higher strength.
[0052] Such braided-tube intraluminal devices are well-known, for
example as described in Wallsten et al, U.S. Pat. No. 5,061,275 and
Wallsten U.S. Pat. No. 4,954,126, the contents of which are
incorporated herein by reference. They are generally used as stents
for providing support to a wall of a blood vessel, for implanting a
graft, e.g., to treat an aneurysm (FIG. 9 of the latter patent), or
for other purposes. As known, the braided tube is normally formed
in an expanded condition (FIGS. 1a, 1b) having a diameter slightly
larger than the diameter of the blood vessel so that when the
device is deployed it becomes firmly embedded in the wall of blood
vessel. However, the braided tube is capable of being stressed into
a contracted condition, as shown in FIGS. 2a and 2b, wherein the
diameter of the braided tube is decreased, and its length
increased, to permit manipulation of the braided tube through the
blood vessel to the site of implantation.
[0053] Further information concerning the construction and
deployment of such braided-tube intraluminal devices is available
in the above-cited patents, and also in Applicant's International
Application PCT/IL01/00624, published 24 Jan. 2002, International
Publication No. WO 02/05729, the contents of which are incorporated
herein by reference.
[0054] When such braided tubes are used as stents within blood
vessels, the filaments forming the braided tube are generally of a
diameter exceeding 50 .mu.m and define windows producing a porosity
index exceeding 80%. Such constructions, however, do not have the
combination of flexibility to enable them to be easily manipulated
through the tortuous blood vessels of the intracranial vascular
system for preventing intracranial aneurysm ruptures, and blood
permeability to enable them to be used for treating aneurysm at or
proximate to perforating vessels, or a bifurcation leading to a
branch vessel. These problems were sought to be overcome in the
above-cited McCrory U.S. Pat. No. 5,951,599, Brown et al U.S. Pat.
No. 6,093,199 and Wallsten U.S. Pat. No. 4,954,126, in producing
braided tubes having a high-permeability portion to be deployed in
the blood vessel and a low-permeability portion aligned with the
aneurysm, but as indicated above such braided tubes constructions
are difficult to produce, difficult to manipulate through the blood
vessel, and difficult to accurately deploy at the site of the
aneurysm.
[0055] According to the present invention, the filaments making up
the braided tube are of a sufficiently small size in cross-section
and define windows of a size such that the braided tube, when in
its contracted condition, is sufficiently flexible so as to be
easily manipulatable through the blood vessel to straddle the
aneurysm; and when in its expanded condition straddling the
aneurysm, reduces the flow of blood through the braided tube to the
aneurysm sufficiently to decrease the possibility of rupture of the
aneurysm. When the device is implantable in a blood vessel having
an aneurysm at or proximate to one or more perforating vessels, or
a bifurcation leading to a branch vessel, the windows defined by
the filaments of the braided tube are such as to reduce the flow of
blood therethrough to the aneurysm to decrease the possibility of
rupturing it, but not to unduly reduce the blood flow to the
perforating or branch vessels to the degree likely to cause damage
to tissues supplied with blood by such vessels. As indicated
earlier, experimental evidence indicates that patency can be
maintained, and ischemia and infarction can be prevented, if less
than 50% of the ostial diameter of the branch vessel is
occluded.
[0056] FIG. 6 schematically illustrates how the bending rigidity or
flexibility of a braided tube varies with the diameter of the
filaments. Region A in FIG. 6 illustrates typical diameters in
conventional stents used for supporting blood vessels, which region
usually starts above 50 .mu.m and extends to several hundred .mu.m.
Region B in FIG. 6 illustrates the region of filament diameters for
use in constructing braided tubes in accordance with the present
invention. The filament diameters in this region would be
significantly smaller than in region A, preferably being 10-60
.mu.m, more preferably 20-40 .mu.m.
[0057] The foregoing dimensions apply to the diameters of filaments
of circular cross-section. Where the filaments are of non-circular
cross-section, such as of rectangular or square cross-section, the
filaments would preferably have a circumference of 40-180 .mu.m.
The circumference is defined in macro scale. The circumference can
be enlarged micro-scale by adding roughness to the wire, in order
to control the neointimal growth and making the circumference in
micro scale longer while keeping the macro scale the same. In this
case the surface cross section of the filament would be in the
range 75-3000 .mu.m.sup.2 preferably 300-1300 .mu.m.sup.2.
[0058] As indicated earlier, the windows formed in the braided tube
would also be preferably within a predetermined range such as to
reduce the blood-flow in the portion of the braided tube applied
over the aneurysm, but maintain sufficient blood flow in any
perforating or branch vessels in the vicinity of the aneurysm.
Preferably the length of the window, i.e., its long dimension as
shown at W.sub.L in FIG. 1a, would be within the range of 50-400
.mu.m, more preferably 80-300 .mu.m, in the expanded condition of
the braided tube. Also, the braid angle (.alpha., FIG. 1a) would
preferably be within the range of 150-20.degree., more preferably
80-40.degree. for high radial force and 100-140.degree. for low
radial force, in the expanded condition of the braided tube.
[0059] The diameter and length of the braided tube in its normal,
expanded condition, will vary according to the location and
anatomical dimensions at the particular site of the implantation.
Preferably, the windows are globally (but not necessary locally)
uniform in size such that any portion of the device can be placed
across the neck of the aneurysm to reduce the blood flow thereto,
while the remaining portions of the device firmly contact the walls
of the blood vessel and securely anchors the device within the
blood vessel.
[0060] The filaments can be made of any suitable material which are
bio-compatible and which can be worked into a braid. Bio-compatible
means any material that can be safely introduced and implanted in
human or animal bodies for indefinite periods of time without
causing any significant physiological damage. Preferably, the
filaments are made of a material selected from among the 316L
stainless steel, tantalum, and super elastic Nitinol, cobalt base
alloy, polymer or any other suitable metal or metal combination.
The filament can be coated with bio-compatible coatings [Ulrich
Sigwart, "Endoluminal Stenting", W. B. Saunders Company Ltd.,
London, 1996]. It is possible to use a combination of several
filament materials in one device and combinations of several
materials in one filament.
[0061] In some situations, it may be desired to implant the device
in a portion of a lumen, e.g., an artery, varying significantly in
diameter along its length. As will be appreciated, if a constant
diameter braided tube device is inserted into such a
variable-diameter lumen, this may result in a defective anchoring
of the device at the larger diameter portion of the lumen, and in a
possible risk of the migration of the device within the lumen. This
problem can be easily overcome in several ways, e.g., by creating
braided devices with variable diameters along their longitudinal
axis, as described in the above-cited International Publication No.
WO 02/05729, the contents of which are incorporated herein by
reference.
[0062] FIG. 7 diagrammatically illustrates the braided tube device,
therein generally designated 20, implanted in a blood vessel 22
having an aneurysm 24 in a region of a blood vessel 22 having a
plurality of perforating vessels 26. The braided tube device 20 is
introduced, in its contracted condition, into the blood vessel 22
and is manipulated to the implantation site by a microcatheter 28
where it is expanded such that it overlies the neck 30 of the
aneurysm sac 24 and the perforating vessels 26. The braided tube is
thus firmly bonded, by its expansion, to the inner surfaces of the
blood vessel 20. As described above, the braided tube device 20 is
constructed such that, in its expanded deployed condition as shown
in FIG. 4, it reduces the flow of blood to the aneurysm sac 24
sufficiently to decrease the possibility of rupture thereof. While
at the same time, it does not unduly reduce the flow of blood to
the perforating vessels 26 to the degree likely to cause damage to
the tissue supplied by the perforating vessels.
[0063] FIGS. 8, 9 and 10 illustrate the use of the braided tube
device, generally designated 30, to treat an aneurysm in a blood
vessel at or proximate to a bifurcation leading to one or more
branch vessels.
[0064] Thus, FIG. 8 illustrates the braided tube device 30
implanted in a blood vessel 32 having an aneurysm 34 at the
bifurcation leading to two branch vessels 36, 38. In the example
illustrated in FIG. 8, the braided tube device 30 is deployed with
one end embedded in the blood vessel 32 and the opposite end
embedded within the branch vessel 38, so as to produce a reduced
blood flow to the aneurysm sac 34, and also to the branch vessel
36. As described earlier, however, while the reduced blood flow to
the aneurysm sac 34 is sufficient to reduce the possibility of
rupture of the sac, the reduced blood flow to the branch 36 is not
sufficient so as to be likely to cause damage to the tissues
supplied by that branch vessel.
[0065] FIG. 9 illustrates a variation wherein one end of the
braided tube 30 is bonded within the main blood vessel 32, and the
opposite end is bonded within the branch vessel 36. In this case,
the aneurysm sac 34 will also have a reduced supply of blood such
as to reduce the possibility of its rupture, while the branch
vessel 38 will have its blood supply reduced but not to the point
of causing damage to the tissues supplied by that vessel.
[0066] FIG. 10 illustrates the variation wherein the opposite ends
of the braided tube 30 are embedded in the two branch vessels 36,
38 at the bifurcation. In this case, the blood supply to the
aneurysm sac 34 will also be reduced, but the blood supply to both
branch vessels 36, 38 will be reduced but not sufficient to cause
damage to the tissues supplied by those branch vessels.
EXAMPLES
[0067] Following are a number of examples of intraluminal devices
constructed in accordance with the invention:
Example 1
[0068] Given:
[0069] 1. Artery diameter=3 mm
[0070] 2. Braiding angle .alpha.=90.degree.
[0071] A porosity index of 70% can achieved by changing the
filament diameter and the number of filaments as follows:
1 Windows Artery Braiding Number Filaments Inscribed Porosity
Diameter Angle of Fil- Width Diameter Index # [mm] [deg] aments
[.mu.m] [.mu.m] [%] 1(a) 3 90 108 20 100 70 1(b) 3 90 78 27 140 70
1(c) 3 90 62 35 180 70 Note: For round cross-section filaments, the
bending stiffness of #1(a) in its contracted condition is one-fifth
that of #1(c) due to the smaller diameter filaments in #1(a).
Example 2
[0072] Given:
[0073] 1. Artery diameter=3 mm
[0074] 2. Braiding angle .alpha.=90.degree.
[0075] 3. Filaments diameter=27 .mu.m
[0076] The porosity index can changes by changing the number of
filaments as follows:
2 Windows Artery Braiding Number Filament Inscribed Porosity
Diameter Angle of Fil- Diameter Diameter Index # [mm] [deg] aments
[.mu.m] [.mu.m] [%] 2(a) 3 90 64 27 180 75 2(b) 3 90 108 27 140 70
2(c) 3 90 110 27 80 60 Note: For round cross-section filaments, the
bending stiffness of #2(a) in its contracted condition is 60% of
#2(c) due to the smaller number of filaments in #2(a).
Example 3
[0077] Given:
[0078] 1. Artery diameter=3 mm
[0079] 2. Number of filaments=78
[0080] 3. Filaments diameter=27 .mu.m
[0081] The porosity index can reduced from its maximum value at
.alpha.=90.degree. in # 3(a) by changing, i.e., increasing in #
3(b) or decreasing in # 3(c) the braiding angle .alpha. as
follows:
3 Windows Artery Braiding Number Filament Inscribed Porosity
Diameter Angle of Fil- diameter Diameter Index # [mm] [deg] aments
[.mu.m] [.mu.m] [%] 3(a) 3 90 78 27 140 70 3(b) 3 106 78 27 110 65
3(c) 3 56 78 27 110 65
Example 4
[0082] Given:
[0083] 1. Artery diameter=3 mm
[0084] 2. Number of filaments=78
[0085] 3. Braiding angle .alpha.=90.degree.
[0086] The porosity index can changed by changing the filament
diameter as?follows:
4 Windows Artery Braiding Number Filaments Inscribed Porosity
Diameter Angle of Fil- Diameter Diameter Index # [mm] [deg] aments
[.mu.m] [.mu.m] [%] 4(a) 3 90 78 20 150 77 4(b) 3 90 78 27 140 70
4(c) 3 90 78 35 130 63 Note: For round cross-section filaments, the
bending stiffness of #4(a)in its contracted condition is one-ninth
that of #4(c) due to the smaller diameter filaments in #4(a).
[0087] While the invention has been described with respect to
several preferred embodiments, it will be appreciated that these
are set forth merely for purposes of example, and that many other
variations, modifications and applications of the invention may be
made.
[0088] For example, the device could be composed of multiple
tubular meshes, lying one above the other in layer-like formations.
Also, the device could include a plurality of groups of filaments
in the longitudinal and/or circumferential direction. Further, the
invention could be implemented with respect to many of the other
variations and applications described in the above-cited
International Application PCT IL01/00624 incorporated herein by
reference.
REFERENCES
[0089] 1. An International Study of Unruptured Intracranial
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rupture and risks of surgical intervention.
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[0094] 6. Lanzino G, Wakhloo A K, Fessler R D, Hartney M L,
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[0095] 7. Yu S C, Zhao J B. A steady flow analysis on the stented
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[0096] 8. Marinkovic S, Gibo H, Milisavljevic M, Cetkovic M.
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