U.S. patent application number 11/956990 was filed with the patent office on 2008-04-17 for expandable cages for embolic filtering devices.
This patent application is currently assigned to ADVANCED CARDIOVASCULAR SYSTEMS, INC.. Invention is credited to William J. Boyle, William J. Harrison, Benjamin C. Huter, Scott J. Huter, Paul F. Muller, John E. Papp.
Application Number | 20080091231 11/956990 |
Document ID | / |
Family ID | 27610468 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080091231 |
Kind Code |
A1 |
Boyle; William J. ; et
al. |
April 17, 2008 |
EXPANDABLE CAGES FOR EMBOLIC FILTERING DEVICES
Abstract
A self-expanding cage for use in conjunction with an embolic
filtering device includes a circumferential member adapted to
expand from an unexpanded position to a expanded position within
the patient's body vessel. A proximal strut and distal strut are
attached to the circumferential member to form the cage. A
plurality of proximal and distal struts may be attached the
circumferential member. Additionally, a second circumferential
member can be attached to the first circumferential member. Each
circumferential member can be connected by a single or a plurality
of connecting struts. One embodiment of the cage utilizes a single
wire to form to the cage. A delivery system attached to the single
wire cage moves the cage and its associated filter element between
the expanded and unexpanded positions through relative movement of
the distal delivery system. This can be accomplished by either
torquing the guide wire onto which the expandable cage is mounted
or by longitudinally moving a tubular member which forms part of
the delivery system longitudinally in relation to the guide
wire.
Inventors: |
Boyle; William J.;
(Fallbrook, CA) ; Harrison; William J.; (Signal
Mountain, TN) ; Huter; Benjamin C.; (Murrieta,
CA) ; Huter; Scott J.; (Temecula, CA) ;
Muller; Paul F.; (San Carlos, CA) ; Papp; John
E.; (Temecula, CA) |
Correspondence
Address: |
FULWIDER PATTON LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE, TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
ADVANCED CARDIOVASCULAR SYSTEMS,
INC.
3200 Lakeside Drive
Santa Clara
CA
95054-2807
|
Family ID: |
27610468 |
Appl. No.: |
11/956990 |
Filed: |
December 14, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10066314 |
Jan 31, 2002 |
|
|
|
11956990 |
Dec 14, 2007 |
|
|
|
Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2230/0067 20130101;
A61F 2002/018 20130101; A61F 2230/008 20130101; A61F 2230/0006
20130101; A61F 2/013 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 29/00 20060101
A61M029/00 |
Claims
1-28. (canceled)
29. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a guide wire; a filter assembly disposed
on the guide wire, the filter assembly including an expandable cage
and filtering element attached to the cage, the cage being movable
between an unexpanded and expanded position and rotatable mounted
on the guide wire, the cage including a circumferential member
which forms an inlet opening for the filtering element when placed
in the expanded position, the guide wire extending through the
inlet opening of the circumferential member and the circumferential
member being positioned at a slant with respect to the body vessel
when placed in the expanded position; and means for maintaining the
guide wire substantially centered through the circumferential
member when the cage is placed in the expanded position, wherein
the circumferential member is adapted to sealingly contact the body
vessel when placed in the expanded position to form a single inlet
opening for capturing embolic debris.
30. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a guide wire; and a filter assembly
disposed on the guide wire, the filter assembly including an
expandable cage and filtering element attached to the cage, the
cage being movable between an expanded position and a collapsed
position, the cage including a single circumferential member
forming an inlet opening when placed in the expanded position, a
single proximal strut having a first end attached to the
circumferential member and a second end disposed on the guide wire,
wherein the guide wire extends through the inlet opening of the
circumferential member the circumferential member is adapted to
sealingly contact the body vessel when placed in the expanded
position to form a single inlet opening for capturing embolic
debris in the filtering element.
31. The embolic filtering device of claim 30, wherein the proximal
strut is configured to maintain the guide wire substantially
centered in the inlet opening of the circumferential member when
the cage is placed in the expanded position.
32. The embolic filtering device of claim 30, wherein the cage is
rotatably mounted to the guide wire.
33. The embolic filtering device of claim 30, wherein the second
end of the proximal strut is rotatably mounted to the guide
wire.
34. The embolic filtering device of claim 30, wherein the
circumferential member defines a plane when placed in the expanded
position and the plane of the circumferential member is maintained
at angle which is not perpendicular to the axis of the portion of
the guide wire that extends through the circumferential member.
35. The embolic filtering device of claim 30, further including a
distal strut having a first end attached to the circumferential
member and a second end disposed on the guide wire.
36. The embolic filtering device of claim 35, wherein both the
proximal strut and the distal strut cooperate to maintain the guide
wire substantially centered in the circumferential member when the
cage is placed in the expanded position.
37. The embolic filtering device of claim 35, wherein the second
end of the proximal strut and the second end of the distal strut
are rotatably mounted to the guide wire.
38. The embolic filtering device of claim 30, further including a
plurality of distal struts attached to circumferential member, each
distal strut having a first end attached to the circumferential
member and a second end disposed on the guide wire.
39. The embolic filtering device of claim 38, wherein the second
ends of the distal struts are rotatably mounted to the guide
wire.
40. The embolic filtering device of claim 30, wherein the
circumferential ring is oval shaped.
41. The embolic filtering device of claim 30, wherein the second
end of the proximal strut is attached to a collar which is
rotatably mounted to the guide wire.
42. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a guide wire; and a filter assembly
disposed on the guide wire, the filter assembly including an
expandable cage and filtering element attached to the cage, the
cage being movable between expanded and collapsed positions, the
cage including a single circumferential member forming an inlet
opening placed in the expanded position, the circumferential member
having a proximal bending region and a distal bending region formed
thereon, a proximal strut having a first end attached to proximal
bending region and a second end disposed on the guide wire, wherein
the guide wire extends through the inlet opening formed by the
circumferential member and is adapted to sealingly contact the body
vessel when placed in the expanded position to form a single inlet
opening for capturing embolic debris in the filtering element.
43. The embolic filtering device of claim 42, wherein the second
end of the proximal strut is rotatably mounted to the guide
wire.
44. The embolic filtering device of claim 42, wherein the proximal
strut help to maintain the guide wire substantially centered in the
circumferential member when the cage is placed in the expanded
position.
45. The embolic filtering device of claim 42, wherein the second
end of the proximal strut is rotatably attached to the guide
wire.
46. The embolic filtering device of claim 42, wherein the second
end of the proximal strut is attached to a collar which is
rotatably mounted to the guide wire.
47. The embolic filtering device of claim 42, further including a
distal strut having a first end attached to distal bending region
and a second end disposed on the guide wire.
48. The embolic filtering device of claim 47, further including a
second distal strut having a first end attached to the
circumferential member and a second end disposed on the guide wire.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to filtering devices
used when an interventional procedure is being performed in a
stenosed or occluded region of a body vessel to capture embolic
material that may be created and released into the vessel during
the procedure. The present invention is more particularly directed
to an embolic filtering device made with an expandable cage or
basket having good flexibility and bendability.
[0002] Numerous procedures have been developed for treating
occluded blood vessels to allow blood to flow without obstruction.
Such procedures usually involve the percutaneous introduction of an
interventional device into the lumen of the artery, usually by a
catheter. One widely known and medically accepted procedure is
balloon angioplasty in which an inflatable balloon is introduced
within the stenosed region of the blood vessel to dilate the
occluded vessel. The balloon dilatation catheter is initially
inserted into the patient's arterial system and is advanced and
manipulated into the area of stenosis in the artery. The balloon is
inflated to compress the plaque and press the vessel wall radially
outward to increase the diameter of the blood vessel, resulting in
increased blood flow. The balloon is then deflated to a small
profile so that the dilatation catheter can be withdrawn from the
patient's vasculature and the blood flow resumed through the
dilated artery. As should be appreciated by those skilled in the
art, while the above-described procedure is typical, it is not the
only method used in angioplasty.
[0003] Another procedure is laser angioplasty which utilizes a
laser to ablate the stenosis by super heating and vaporizing the
deposited plaque. Atherectomy is yet another method of treating a
stenosed body vessel in which cutting blades are rotated to shave
the deposited plaque from the arterial wall. A vacuum catheter is
usually used to capture the shaved plaque or thrombus from the
blood stream during this procedure.
[0004] In the procedures of the kind referenced above, abrupt
reclosure may occur or restenosis of the artery may develop over
time, which may require another angioplasty procedure, a surgical
bypass operation, or some other method of repairing or
strengthening the area. To reduce the likelihood of the occurrence
of abrupt reclosure and to strengthen the area, a physician can
implant an intravascular prosthesis for maintaining vascular
patency, commonly known as a stent, inside the artery across the
lesion. The stent can be crimped tightly onto the balloon portion
of the catheter and transported in its delivery diameter through
the patient's vasculature. At the deployment site, the stent is
expanded to a larger diameter, often by inflating the balloon
portion of the catheter.
[0005] The above non-surgical interventional procedures, when
successful, avoid the necessity of major surgical operations.
However, there is one common problem which can become associated
with all of these non-surgical procedures, namely, the potential
release of embolic debris into the bloodstream that can occlude
distal vasculature and cause significant health problems to the
patient. For example, during deployment of a stent, it is possible
that the metal struts of the stent can cut into the stenosis and
shear off pieces of plaque that can travel downstream and lodge
somewhere in the patient's vascular system. Pieces of plaque
material are sometimes generated during a balloon angioplasty
procedure and become released into the bloodstream. Additionally,
while complete vaporization of plaque is the intended goal during
laser angioplasty, sometimes particles are not fully vaporized and
enter the bloodstream. Likewise, not all of the emboli created
during an atherectomy procedure may be drawn into the vacuum
catheter and, as a result, enter the bloodstream as well.
[0006] When any of the above-described procedures are performed in
the carotid arteries, the release of emboli into the circulatory
system can be extremely dangerous and sometimes fatal to the
patient. Debris carried by the bloodstream to distal vessels of the
brain can cause cerebral vessels to occlude, resulting in a stroke,
and in some cases, death. Therefore, although cerebral percutaneous
transluminal angioplasty has been performed in the past, the number
of procedures performed has been somewhat limited due to the
justifiable fear of an embolic stroke occurring should embolic
debris enter the bloodstream and block vital downstream blood
passages.
[0007] Medical devices have been developed to attempt to deal with
the problem created when debris or fragments enter the circulatory
system following vessel treatment utilizing any one of the
above-identified procedures. One approach which has been attempted
is the cutting of any debris into minute sizes which pose little
chance of becoming occluded in major vessels within the patient's
vasculature. However, it is often difficult to control the size of
the fragments which are formed, and the potential risk of vessel
occlusion still exists, making such a procedure in the carotid
arteries a high-risk proposition.
[0008] Other techniques include the use of catheters with a vacuum
source which provides temporary suction to remove embolic debris
from the bloodstream. However, as mentioned above, there can be
complications associated with such systems if the catheter does not
remove all of the embolic material from the bloodstream. Also, a
powerful suction could cause trauma to the patient's
vasculature.
[0009] Another technique which has had some success utilizes a
filter or trap downstream from the treatment site to capture
embolic debris before it reaches the smaller blood vessels
downstream. The placement of a filter in the patient's vasculature
during treatment of the vascular lesion can reduce the presence of
the embolic debris in the bloodstream. Such embolic filters are
usually delivered in a collapsed position through the patient's
vasculature and then expanded to trap the embolic debris. Some of
these embolic filters are self expanding and utilize a restraining
sheath which maintains the expandable filter in a collapsed
position until it is ready to be expanded within the patient's
vasculature. The physician can retract the proximal end of the
restraining sheath to expose the expandable filter, causing the
filter to expand at the desired location. Once the procedure is
completed, the filter can be collapsed, and the filter (with the
trapped embolic debris) can then be removed from the vessel. While
a filter can be effective in capturing embolic material, the filter
still needs to be collapsed and removed from the vessel. During
this step, there is a possibility that trapped embolic debris can
backflow through the inlet opening of the filter and enter the
bloodstream as the filtering system is being collapsed and removed
from the patient. Therefore, it is important that any captured
embolic debris remain trapped within this filter so that particles
are not released back into the body vessel.
[0010] Some prior art expandable filters vessel are attached to the
distal end of a guide wire or guide wire-like member which allows
the filtering device to be steered in the patient's vasculature as
the guide wire is positioned by the physician. Once the guide wire
is in proper position in the vasculature, the embolic filter can be
deployed to capture embolic debris. The guide wire can then be used
by the physician to deliver interventional devices, such as a
balloon angioplasty dilatation catheter or a stent delivery
catheter, to perform the interventional procedure in the area of
treatment. After the procedure is completed, a recovery sheath can
be delivered over the guide wire using over-the-wire techniques to
collapse the expanded filter for removal from the patient's
vasculature.
[0011] When a combination of an expandable filter and guide wire is
utilized, it is important that the expandable filter portion
remains flexible in order to negotiate the often tortuous anatomy
through which it is being delivered. An expandable filter which is
too stiff could prevent the device from reaching the desired
deployment position within the patient's vasculature. As a result,
there is a need to increase the flexibility of the expandable
filter without compromising its structural integrity once in
position within the patient's body vessel. Also, while it is
beneficial if the area of treatment is located in a substantially
straight portion of the patient's vasculature, sometimes the area
of treatment is at a curved portion of the body vessel which can be
problematic to the physician when implanting the expandable filter.
If the expandable filter portion is too stiff, it is possible that
the filter may not fully deploy within the curved portion of the
body vessel. As a result, gaps between the filter and vessel wall
can be formed which may permit some embolic debris to pass
therethrough. Therefore, the filtering device should be
sufficiently flexible to be deployed in, and to conform to, a
tortuous section of the patient's vasculature, when needed.
[0012] What has been needed is an expandable filter assembly having
high flexibility and bendability with sufficient strength and
radiopacity to be successfully deployed within a patient's
vasculature to collect embolic debris which may be released into
the patient's vasculature.
SUMMARY OF THE INVENTION
[0013] The present invention provides a highly flexible cage (also
referred to as a "basket") for use with an embolic filtering device
designed to capture embolic debris created during the performance
of a therapeutic interventional procedure, such as a balloon
angioplasty or stenting procedure, in a body vessel. The present
invention provides the physician with an embolic filtering device
having high flexibility to be steered through tortuous anatomy, but
yet possessing sufficient strength to hold open a filtering element
against the wall of the body vessel for capturing embolic debris.
An embolic filtering device made in accordance with the present
invention is relatively easy to deploy, has good visibility under
fluoroscopy, and has good flexibility and is conformable to the
patient's anatomy.
[0014] An embolic filtering device made in accordance with the
present invention utilizes an expandable cage made from a
self-expanding material, for example, nickel-titanium (NiTi), and
includes struts capable of expanding from a collapsed position or
configuration having a first delivery diameter to an expanded or
deployed position or configuration having a second implanted
diameter. A filter element made from an embolic-capturing material
is attached to the expandable cage to move between an expanded
position and a deployed position.
[0015] In one aspect of the present invention, the enhanced
flexibility and bendability of the embolic filtering device is
achieved through the utilization of a unique cage design having a
highly flexible and conformable circumferential member which is
adapted to expand and conform to the size and shape of the body
vessel. The expandable cage includes a proximal strut having an end
connected to a guide wire and the other end attached to the
circumferential member. A distal strut is attached to the
circumferential member and has its other end attached to the guide
wire. The filter element is attached to the circumferential member
and will open and close as the expandable cage moves between its
expanded, deployed position and its unexpanded, delivery position.
The circumferential member is self-expanding and is made from a
highly flexible material which allows it to conform to the
particular size and shape of the body vessel. This high flexibility
and conformability of the circumferential member allows the
composite device to be deployed in curved sections of the patient's
anatomy and other eccentric vessel locations having non-circular
shaped lumens. This allows an embolic filtering device made in
accordance with the present invention to be deployed in locations
in the patient's anatomy which might not be otherwise suitable for
stiffer filtering devices.
[0016] In another aspect of the present invention, bending regions
formed on the circumferential member help to actuate the
circumferential member between its unexpanded and expanded
positions. In one aspect of the present invention, these bending
regions are substantially U-shaped bends formed on the
circumferential member at various locations along the member. While
the circumferential member itself is self-expanding and capable of
moving between these positions, the bending regions further enhance
the actuation of the circumferential member between these
positions. In one particular aspect of the present invention, the
proximal strut is attached directly to this bending region.
Likewise, a distal strut can be attached to a second bend section.
In this fashion, a highly bendable and conformable cage can be
produced which should conform to the particular shape of the body
vessel once deployed.
[0017] In other aspects of the present invention, a pair of
circumferential members can be utilized to create the expandable
cage which maintains a high degree of bendability and
conformability, but yet is sufficiently rigid enough to maintain
the filtering element in an expanded position once the filtering
device is fully deployed. The pair of circumferential members
provides additional support to the filter element to help maintain
the filter in the expanded configuration. Other aspects of the
present invention utilize sets of three or four proximal struts and
distal struts to form a larger expandable cage which still retains
good bendability and conformability, yet possesses sufficiently
radial strength when deployed to maintain proper wall apposition
between the filter element and the body vessel.
[0018] In another aspect of the present invention, the expandable
cage is made from a single, self-expanding wire adapted to open a
filter element. The wire forms at least one loop in its expanded
position to create an opening and helps to maintain the filter
element in proper contact with the wall of the body vessel.
Alternatively, a number of spirals can be formed on the wire cage
to create a helical-type expandable cage capable of moving between
an unexpanded and expanded position. In one form of the invention,
the expandable cage can be utilized in conjunction with a delivery
sheath which maintains the cage in its unexpanded position for
delivery through the patient's vasculature. In another aspect of
the invention, a delivery system which includes an actuating member
is connected to the expandable cage to allow the cage to move
between the expanded and collapsed positions by either rotation of
the guide wire onto which the expandable cage is mounted or by
moving the actuating member longitudinally along the guide wire.
Accordingly, this can be accomplished by the physician at location
outside of the patient.
[0019] The struts of the expandable cage can be set to remain in
the expanded, deployed position until an external force is placed
over the struts to collapse and move the struts to the collapsed
position. One way of accomplishing this is through the use of a
restraining sheath, for example, which can be placed over the
filtering device in a coaxial fashion to contact the cage and move
the cage into the collapsed position. The embolic filtering device
can be placed in the patient's vasculature and remain there for a
period of time. The filtering device can be attached to the distal
end of an elongated member, such as a guide wire, for temporary
placement in the vasculature to capture emboli created during an
interventional procedure. A guide wire may be used in conjunction
with the embolic filtering device when debris is to be filtered
during an interventional procedure such as an angioplasty procedure
or stenting procedure. The guide wire and filtering assembly, with
the restraining sheath placed over the filter assembly, can be
delivered through the patient's vasculature to the target location.
Once the physician properly manipulates the guide wire into the
target area, the restraining sheath can be retracted to deploy the
basket into the expanded position. This can be easily performed by
the physician by simply retracting the proximal end of the
restraining sheath (located outside of the patient). Once the
restraining sheath is retracted, the self-expanding properties of
the cage cause the struts and circumferential members to move in a
outward, radial fashion away from the guide wire to contact the
wall of the body vessel. As the struts and circumferential
member(s) expand radially, so does the filter element which will
now be maintained in place to collect embolic debris that may be
released into the bloodstream as the physician performs the
interventional procedure. The guide wire can be used by the
physician to deliver the necessary interventional device into the
area of treatment. The deployed filter element captures embolic
debris created and released into the body vessel during the
interventional procedure. A retrieval sheath can be delivered over
the guide wire to collapse the filter assembly for removal from the
patient.
[0020] It is to be understood that the present invention is not
limited by the embodiments described herein. The present invention
can be used in arteries, veins, and other body vessels. Other
features and advantages of the present invention will become more
apparent from the following detailed description of the invention,
when taken in conjunction with the accompanying exemplary
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a perspective view of an embolic filtering device
with an expandable cage embodying features of the present
invention.
[0022] FIG. 2 is a perspective view of the expandable cage of FIG.
1 in its expanded configuration with the filter element removed to
better show the expandable cage.
[0023] FIG. 3 is an elevational view, partially in cross section,
of the embolic filtering device of FIG. 1 as it is being delivered
within a body vessel downstream from an area to be treated.
[0024] FIG. 4 is an elevational view, partially in cross section,
similar to that shown in FIG. 3, wherein the embolic filtering
device is deployed in its expanded position within the body vessel
for filtering purposes
[0025] FIG. 5 is a perspective view of the expandable cage of FIGS.
1 and 2 as it is initially formed from a tubular member.
[0026] FIG. 6 is a perspective view of another embodiment of an
expandable cage as formed from a tubular member which embodies
features of the present invention.
[0027] FIG. 7 is a perspective view of another embodiment of an
expandable cage as formed from a tubular member which embodies
features of the present invention.
[0028] FIG. 8 is a perspective view of another embodiment of an
expandable cage as formed from a tubular member which embodies
features of the present invention.
[0029] FIG. 9 is a perspective view of another an embolic filtering
device which uses an expandable cage embodying features of the
present invention.
[0030] FIG. 10 is a side elevational view of a connecting strut
having an S-shaped configuration which joins adjacent
circumferential members together.
[0031] FIG. 11 is a side elevational view, partially in
cross-section, of the distal end of the embolic filter assembly of
FIG. 1.
[0032] FIG. 12 is a side elevational view, partially in
cross-section, of the distal end of the embolic filter assembly of
FIG. 9.
[0033] FIG. 13 is a perspective view of another embodiment of an
expandable cage as formed from a tubular member which embodies
features of the present invention.
[0034] FIG. 14 is a perspective view of an embolic filtering device
which uses the expandable cage of FIG. 9 and embodies features of
the present invention.
[0035] FIG. 15 is a side elevational view of the embolic filtering
device of FIG. 10.
[0036] FIG. 16 is a perspective view of another embodiment of an
embolic filtering device embodying features of the present
invention.
[0037] FIG. 17A is a side elevational view of the filter member
attached to the expandable cage of the embolic filtering device of
FIG. 16.
[0038] FIG. 17B is a side elevational view showing an alternative
method for attaching the filter member to the expandable cage of
the embolic filter device of FIG. 16.
[0039] FIG. 18 is a side elevational view of another embolic
filtering device with an expandable cage embodying features of the
present invention.
[0040] FIG. 19 is a side elevational view of the embolic filtering
device of FIG. 13 showing one particular mechanism for moving the
expandable cage between the unexpanded and expanded positions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0041] Turning now to the drawings, in which like reference
numerals represent like or corresponding elements in the drawings,
FIGS. 1 and 2 illustrate one particular embodiment of an embolic
filtering device 20 incorporating features of the present
invention. This embolic filtering device 20 is designed to capture
embolic debris which may be created and released into a body vessel
during an interventional procedure. The embolic filtering device 20
includes an expandable filter assembly 22 having a self-expanding
basket or cage 24 and a filter element 26 attached thereto. In this
particular embodiment, the expandable filter assembly 22 is
rotatably mounted on the distal end of an elongated (solid or
hollow) cylindrical tubular shaft, such as a guide wire 28. The
expandable filter assembly could also be attached directly onto the
guide wire, so as not to rotate independently of the guide wire.
The guide wire has a proximal end (not shown) which extends outside
the patient and is manipulated by the physician to deliver the
filter assembly into the target area in the patient's vasculature.
A restraining or delivery sheath 30 (FIG. 3) extends coaxially
along the guide wire 28 in order to maintain the expandable filter
assembly 22 in its collapsed position until it is ready to be
deployed within the patient's vasculature. The expandable filter
assembly 22 is deployed by the physician by simply retracting the
restraining sheath 30 proximally to expose the expandable filter
assembly. Once the restraining sheath is retracted, the
self-expanding cage 24 immediately begins to expand within the body
vessel (see FIG. 4), causing the filter element 26 to expand as
well.
[0042] An obturator 32 affixed to the distal end of the filter
assembly 32 can be implemented to prevent possible "snowplowing" of
the embolic filtering device as it is being delivered through the
vasculature. The obturator can be made from a soft polymeric
material, such as Pebax 40D, and has a smooth surface to help the
embolic filtering device travel through the vasculature and cross
lesions while preventing the distal end of the restraining sheath
30 from "digging" or "snowplowing" into the wall of the body
vessel.
[0043] In FIGS. 3 and 4, the embolic filtering device 20 is shown
as it is being delivered within an artery 34 or other body vessel
of the patient. Since the embolic filtering device made in
accordance with the present invention possesses excellent
bendability and flexibility, it will conform well to the shape of
the vasculature while allowing the filter assembly to more easily
negotiate a curved radius in the patient's vasculature.
[0044] Referring now to FIG. 4, the embolic filtering device 20 is
shown in its expanded position within the patient's artery 34. This
portion of the artery (FIG. 3) has an area of treatment 36 in which
atherosclerotic plaque 38 has built up against the inside wall 40
of the artery 34. The filter assembly 22 is to be placed distal to,
and downstream from, the area of treatment 36. For example, the
therapeutic interventional procedure may comprise the implantation
of a stent (not shown) to increase the diameter of an occluded
artery and increase the flow of blood therethrough. It should be
appreciated that the embodiments of the embolic filtering device
described herein are illustrated and described by way of example
only and not by way of limitation. Also, while the present
invention is described in detail as applied to an artery of the
patient, those skilled in the art will appreciate that it can also
be used in other body vessels, such as the coronary arteries,
carotid arteries, renal arteries, saphenous vein grafts and other
peripheral arteries. Additionally, the present invention can be
utilized when a physician performs any one of a number of
interventional procedures, such as balloon angioplasty, laser
angioplasty or atherectomy which generally require an embolic
filtering device to capture embolic debris created during the
procedure.
[0045] The cage 24 includes self-expanding struts which, upon
release from the restraining sheath 30, expand the filter element
26 into its deployed position within the artery (FIG. 4). Embolic
particles 27 created during the interventional procedure and
released into the bloodstream are captured within the deployed
filter element 26. The filter may include perfusion openings 29, or
other suitable perfusion means, for allowing blood flow through the
filter 26. The filter element will capture embolic particles which
are larger than the perfusion openings while allowing some blood to
perfuse downstream to vital organs. Although not shown, a balloon
angioplasty catheter can be initially introduced within the
patient's vasculature in a conventional SELDINGER technique through
a guiding catheter (not shown). The guide wire 28 is disposed
through the area of treatment and the dilatation catheter can be
advanced over the guide wire 28 within the artery 34 until the
balloon portion is directly in the area of treatment 36. The
balloon of the dilatation catheter can be expanded, expanding the
plaque 38 against the wall 40 of the artery 34 to expand the artery
and reduce the blockage in the vessel at the position of the plaque
38. After the dilatation catheter is removed from the patient's
vasculature, a stent (not shown) could be implanted in the area of
treatment 36 using over-the-wire techniques to help hold and
maintain this portion of the artery 34 and help prevent restenosis
from occurring in the area of treatment. The stent could be
delivered to the area of treatment on a stent delivery catheter
(not shown) which is advanced from the proximal end of the guide
wire to the area of treatment. Any embolic debris created during
the interventional procedure will be released into the bloodstream
and should enter the filter 26. Once the procedure is completed,
the interventional device may be removed from the guide wire. The
filter assembly 22 can also be collapsed and removed from the
artery 34, taking with it any embolic debris trapped within the
filter element 26. A recovery sheath (not shown) can be delivered
over the guide wire 28 to collapse the filter assembly 22 for
removal from the patient's vasculature.
[0046] Referring again to FIGS. 1 and 2, the expandable cage 24
includes four self-expanding proximal struts 42-48 which help to
deploy the filter element 26 and the remainder of the expandable
cage. These proximal struts 42-48 are coupled to a first
circumferential member 50 which is adapted to move from the
unexpanded delivery position (FIG. 3) to the expanded deployed
position (FIG. 4). A second circumferential member 52 is, in turn,
coupled to the first circumferential member 50. The deployment of
the first and second circumferential members 50 and 52 results in
the filter element 26 being placed against the wall 40 of the
artery or other body vessel, even if the lumen of the body vessel
is non-circular (FIG. 4). Four distal struts 54-60 are connected to
the second circumferential member 52 and extend distally towards
the obturator 32.
[0047] As can be seen in FIGS. 1 and 2, each circumferential member
is formed in a zig-zag pattern which includes eight apexes to which
the proximal and distal struts are attached. These apexes form
eight bending regions 62 which enhance the bending of the
circumferential member as it moves between the unexpanded and
expanded positions. In the particular embodiment shown in FIG. 2,
each bending region 62 is placed on the circumferential member
approximately 45 degrees apart. Each of the proximal struts
includes a first end 64 attached to the collar 65 which is
rotatably mounted to the guide wire 28. The proximal struts may be
attached directly onto the guide wire. Each proximal strut also
includes a second end 66 connected to one of the bending regions of
the first circumferential member 50. The bending regions 62
attached to the proximal struts are spaced approximately 90 degrees
apart from each other along a circular diameter defined by the
expanded circumferential member. Each of the distal struts, in
turn, has a first end 68 connected to, and extending towards, the
obturator 32 and a second end 70 attached to distally located
bending regions on the second circumferential member. These
distally located bending regions, in turn, are spaced approximately
90 degrees apart from each other and are offset 45 degrees from the
proximally located bending regions.
[0048] Each of the bending regions is substantially U-shaped which
help to create a natural bending point on the circumferential
member. While the flexibility of the circumferential members is
already high, these bending regions only help to increase the
ability of the circumferential member to collapse or expand when
needed. In this manner, the shape of the hinge regions creates a
natural hinge that helps to actuate the expandable cage between the
unexpanded and expanded positions. As can be best seen in FIG. 2,
the U-shaped proximally located bending regions are positioned
directly opposite the U-shaped portion of the distally located
bending regions. The positioning of the direction of the U portion
also enhances the ability of the circumferential member to bend.
These circumferential members, while being quite bendable,
nevertheless maintain sufficient radial strength to remain in the
deployed position to hold the filter element 26 open in the body
vessel for collecting embolic particles which may be entrained in
the body fluid.
[0049] The shape of the bending regions are shown as substantially
U-shaped portions, however, any one of a number of different shapes
could also be utilized to create a natural bending point on the
circumferential member. For example, a V-shaped region could also
be formed and would function similarly to a U-shaped portion to
facilitate the collapse and expansion of the circumferential member
as needed. Alternative shapes and sizes of the bending regions also
could be utilized without departing from the spirit and scope of
the invention. Although eight bending regions are shown on each
circumferential member, it should be appreciated that the number of
different bending regions could be increased or decreased as
needed. For example, it is possible to utilize only two bending
regions, as is shown in the embodiment of the expandable cage of
FIGS. 9-11, in order to facilitate bending. Additional bending
regions also could be utilized in the event that additional
proximal or distal struts are used to form the expandable cage.
Moreover, different sizes, shapes and location of the bending
regions can be utilized on any circumferential member.
[0050] Referring now to FIG. 5, the expandable cage 24 is shown as
it appears after it has been cut from a tubular member, the process
of which is disclosed in further detail below. As can be seen, the
free ends of the proximal and distal struts are initially spread
apart after being formed from the tubular member. The free ends of
the struts can be attached to a collar, such as is shown in FIGS. 1
and 2, to allow the expandable cage to be mounted to an elongated
member, such as a guide wire. The free ends of the proximal and
distal struts can be fastened to the collar using known bonding
techniques, including, braising, soldering, welding, as well as
adhesive bonding.
[0051] Referring now to FIG. 6, a similar embodiment of the
expandable cage 24 is shown. It should be appreciated that the
expandable cage of FIG. 6 is also shown as it would be cut from a
tubular member and that the free ends of the proximal and distal
struts are not shown attached to a collar or an obturator. This
design shows how the first and second circumferential members can
be coupled to, and spaced apart, from each other by short
connecting struts 71. These short connecting struts 71 create a
larger basket and may help the circumferential members to expand
since the circumferential members are not spaced as closely as they
are in the embodiment shown in FIGS. 1-2.
[0052] The expandable cage 24 of the present invention is shown
rotatably mounted to the distal end of the guide wire 28 to allow
the entire filter assembly 22 to remain stationary once deployed in
the body vessel. This feature prevents the filtering assembly from
rotating against the wall of the body vessel in the event that the
proximal end of the guide wire should be rotated by the physician
during use. As a result, the possibility that the deployed filter
assembly 22 could be rotated to cause trauma to the wall of the
vessel is minimized. Referring again to FIGS. 1 and 2, a pair of
stop fittings 72 and 74 are placed on the guide wire to maintain
the collar 65, and hence the proximal end of the expandable cage
24, rotatably fixed to the guide wire 28. These stop fittings 72
and 74 allow the expandable cage 24 to spin on the guide wire while
restricting the longitudinal movement of the cage on the guide
wire. This particular mechanism is just one way in which the
expandable cage 24 can be mounted to the guide wire 28.
Alternatively, the expandable cage can be attached directly onto
the guide wire so as not to rotate independently.
[0053] Referring now to FIGS. 7 and 8, alternative embodiments of
an expandable cage made in accordance with the present invention
are shown. First, referring specifically to FIG. 7, the expandable
cage 80 is shown having only three proximal struts 82-86 and three
distal struts 88-92 attached to first and second circumferential
members 94 and 96. It should be appreciated that this particular
figure shows the expandable cage 80 as it would appear after being
cut from a tubular member since the free ends of the proximal and
distal struts are unconnected to a collar or obturator. Each
circumferential member 94 and 96 has six apexes which form the
bending regions 100 on the circumferential member. Each of the
three proximally located bending regions are spaced approximately
120 degrees apart from each other and, likewise, the distally
located bending regions are spaced approximately 120 degrees apart.
It should be appreciated that this embodiment of the expandable
cage functions in the same manner as the cage shown in FIGS.
1-5.
[0054] FIG. 8 shows a further embodiment of an expandable cage 102
which is similar to the embodiment shown in FIG. 7, except for the
presence of short, connecting struts 104 which connect the first
and second circumferential members 94 and 96 together. Likewise,
this particular cage 102 is shown in its fully expanded position as
it would appear after being cut from a tubular member with the free
ends of the proximal and distal struts remaining unattached. This
particular embodiment, as with the embodiment shown in FIG. 7,
would require the ends of the struts to be attached to a collar, an
obturator or some other structure to fully form the expandable
cage. Alternatively, the ends of the struts of this embodiment, or
any embodiment of the expandable cage, could be directly attached
to the elongated member, such as a guide wire, directly if so
desired. In this manner, the expandable cage would not be rotatably
mounted to the guide wire, but would nevertheless be fixed thereto.
In such an alternative embodiment of the embolic filtering device,
only one end of the expandable cage, usually the proximal struts of
the cage, would be physically and directly attached to the guide
wire. The distal end of the cage would be capable of longitudinal
movement to allow the cage to move between its unexpanded and
expanded configurations.
[0055] An alternative embodiment of the embolic filtering device 20
is shown in FIG. 9. This particular embodiment of the embolic
filtering device 20 includes an expandable filter assembly 22
having a self-expanding cage 24 and a filter element 26 attached
thereto. The expandable filter assembly 22 is shown rotatably
mounted on a distal end of an elongated shaft, such as guide wire
28. In this particular embodiment, the guide wire 28 does not
extend through the expandable cage 24, is as shown in the
embodiment of FIGS. 1 and 2, but rather, terminates at the distal
most fitting 74 connected to the guide wire 28. In this manner, the
filtering assembly 22 remains rotatably fixed to the guide wire 28
to provide the same features described above. The absence of the
short segment of guide wire through the expandable cage may provide
a lower profile to the composite filter assembly, if desired. The
distal most end of the assembly includes a tip coil which allows
the physician to steer the composite embolic filtering
device/delivery sheath as is shown in FIG. 3.
[0056] Referring now to FIGS. 11 and 12, methods in which the ends
of the distal struts of the embodiment of FIGS. 1 and 9 could be
attached to the obturator 32 is shown. As can be seen in FIG. 11,
the distal ends 68 are attached to a tubular member 106 which
extends into the obturator 32. The ends 68 are attached to the
outer surface 108 of the tubular member 106. The filter 26 tapers
to a distal end 107 which is, in turn, bonded or otherwise
adhesively attached to the outer surface 108 of this tubular member
106. Likewise, at least a portion of the tubular member is in
contact with the obturator 32 and is adhesively bonded or otherwise
affixed thereto. The inner surface 110 of the tubular member 106
can slide over the guide wire 28 and tip coil 114. Referring
specifically now to FIG. 12, the method of attaching the distal
struts of the embodiment of FIG. 9 is shown. This particular
construction is very similar to the attachment depicted in FIG. 11.
Since there is no continuous guide wire extending through the
expandable cage 24, a short segment 112 of the guide wire would be
adhesively bonded or otherwise attached to the inner surface 110 of
the tubular member 106. The combination of elements forms an
integral distal end for the filtering assembly which can move
relative to the guide wire during usage.
[0057] The short connecting struts 71 utilized in conjunction with
the different embodiments of the expandable cage can be a
substantially straight segment, as is shown in FIGS. 6 and 8, or
can be a non-linear shape which may help in deploying the embolic
filter in a curved section of the patient's anatomy. Referring
specifically to FIG. 10, an example of a non-linear connecting
strut 71 which connects a first circumferential member 50 to a
second circumferential member 52 is shown. As can be seen in FIG.
10, the non-linear connecting strut has a substantial S-shape
capable of undergoing bending forces to increase the ability of the
cage to bend within the anatomy in which it is deployed. The
non-linear intermediate strut 71 of FIG. 10 is just one particular
shape which could be used in conjunction with the present
invention. It should be appreciated that other sizes and shapes of
the connecting struts could be utilized in accordance with any of
the embodiments of an expandable cage made in accordance with the
present invention.
[0058] Referring now to FIGS. 13-15, an alternative embodiment of
the embolic filter device 120 is shown which includes an expandable
filter assembly 122 with an expandable cage 124. In this particular
embodiment, the expandable cage 124 is a modification of the
expandable cage shown in FIGS. 1-5. The filter assembly 122
includes the filter member (not shown) utilized to filter the
embolic debris in the body vessel and a plurality of openings (not
shown) through which the body fluid flows through while the embolic
particles remain trapped in the pocket formed by the filter member.
The filter member is shown as it would appear on the filter
assembly 122 by the lines 126 which depicts the outer edge of the
filter member. The filter assembly 112 is also shown attached to a
guide wire 128 having a proximal end (not shown) extending outside
of the patient's body which can be manipulated by the physician to
steer the device into the target area in the patient's vasculature.
This particular embodiment is self-expanding, as with the other
embodiment shown in FIGS. 1-5, would be kept in a collapsed
delivery position through the use of a sheath which would extend
over the filter assembly (as is shown in FIG. 3) in order to
deliver the device into the target area.
[0059] The expandable cage includes a single circumferential member
130 and a single proximal strut 132 and a single distal strut 134.
The circumferential member 130 includes only a pair of bending
regions 136 and 138 although it is still possible to utilize other
bending regions. The use of a single proximal strut 132 reduces the
amount of surface area of the struts that are placed in front of
the opening of the filter assembly, thus minimizing the chances
that emboli could collect on strut surfaces rather than being
driven into the filter member. The use of a single distal strut
also allows the device to be more flexible in the distal area where
flexibility is needed when negotiating tortuous anatomy. It should
be appreciated that a single circumferential member could be used
in accordance with the present embodiment or additional
circumferential members could be added to create a longer filtering
assembly.
[0060] The proximal strut 132 has one end 140 attached to a collar
142 that is rotatably mounted onto the distal end of the guide
wire. A pair of stop fittings (not shown) maintain the collar
rotatably mounted to the distal end of the guide wire. Also, the
filter can be attached directly onto the guide wire. The other end
144 of the proximal strut is in turn attached to the bending region
136 located on the circumferential member 130. The distal strut 134
includes one end 146 attached to the bending region 138 of the
circumferential member 130 with the other end 148 attached to a
collar 147 or tubular member 149 that extends proximally from the
obturator 145. Alternatively, the method of attaching the distal
strut to the obturator can be similar to the arrangement shown in
FIG. 12.
[0061] Referring now to FIG. 16, an alternative design of the
embolic filter device 120 is shown. This particular embodiment is
similar to the one shown in FIGS. 13-15 except for the additional
distal struts 150 and 152 which extend from the circumferential
member 130 to the collar 147. As can be seen, these additional
distal struts 150 and 152 are attached to the circumferential
members at a point between the two bending regions 136 and 138
which are formed on the circumferential member 130. These
additional distal struts 150 and 152 provide additional rigidity to
the filter assembly 122. It should be appreciated that additional
or less distal struts could be added to the expandable cage 124 to
provide additional support and strength to the cage as needed. The
filter member could be attached as shown in FIG. 17A or 17B.
[0062] Referring now to FIGS. 18 and 19, an alternative embodiment
of the embolic filter device 160 is shown. In this particular
embodiment, the circumferential members have been replaced with a
single, continuous wire 162 which forms the expandable cage 164.
This cage 164 could be made from a lased tubular member in a
manufacturing process similar to that for making the other
embodiments of the expandable cage disclosed herein. The expandable
cage 164 could be attached to the guide wire 166 as shown in FIG.
18. As can be seen in FIGS. 18 and 19, the expandable cage 164
forms at least one loop 168 when placed in the expanded position
which results in a large the opening for the filter member, the
outline of which is depicted by lines 170. This loop 168 remains
substantially perpendicular to the guide wire 166 to enhance vessel
apposition once placed in the body vessel.
[0063] The expandable cage 164 can be made from coldworked
nickel-titanium or similar materials which will result in the wire
162 forming the loop 168 once placed in the expanded position. "X"
marks have been placed on the wire 162 to designate areas which
could be thinned to allow the wire 162 to more easily bend. The
loop 168 formed by the wire 162 can be somewhat beneficial since it
is directly perpendicular to the axis of the wire 166 to enhance
the apposition of the filter assembly within the patient's body
vessel. The proximal end 165 of the wire 162 can be attached to a
collar 167 which is rotatably mounted to the guide wire 166. A pair
of stop fittings (not shown) would be utilized to allow the cage
164 to spin freely on the guide wire in the same manner as the
other embodiments disclosed herein. The other end of the wire 169
could, in turn, be connected to the obturator 171 in a manner
similar to the attachment method described herein and shown in FIG.
15. In this manner, the distal end 169 of the expandable cage 164
would be movable longitudinally over the length of the guide wire
166 to enable it to move between its collapsed and open
position.
[0064] Referring now to FIG. 19, the embolic filtering device 160
is shown as it would be mounted onto a movable actuating device 172
which is shown as a tubular member 174 in the figure. In this
particular embodiment, the end 165 of the wire 162 is attached
directly to the tubular member 174 with the other end 169 of the
wire 162 being attached directly to the guide wire 166. This
particular embodiment of the embolic filtering device 160 has
certain features which allow the physician to manipulate the
filtering assembly, i.e., expand and contract the filter member, as
needed by either rotating the guide wire 166 or moving the tubular
member 174 longitudinally along the length of the guide wire. This
tubular member 174 extends proximally to a location where the
physician can manipulate the proximal end 176 of the tubular member
174 in order to move the end 165 of the wire 162 longitudinally
along the guide wire 166. In this manner, the expandable cage 164
will be capable of expanding or collapsing depending upon the
direction in which the proximal end 176 of the tubular member 174
is manipulated. In use, the physician simply holds onto a torque
device 178 attached to the guide wire 166 and manipulates the
proximal end 176 of the tubular member 174 in order to collapse or
deploy the expandable cage 164. In this manner, the physician moves
the proximal end 176 longitudinally along the length of the guide
wire 166 to either open or collapse the filter member.
Alternatively, the physician can simply rotate the torque device
178, while keeping the proximal end 176 of the tubular member 174
stationary, to cause the end 169 of the wire 162 to turn with the
guide wire 166. This action will cause the expandable cage 164 to
either twist down onto the guide wire to collapse the filter or
will open to the expanded position.
[0065] It should be appreciated that while the particular
embodiments shown in FIGS. 18 and 19 depict a single loop 168
formed by the wire 162 to define the expandable cage 164, a
plurality of loops could be formed to increase the size and the
strength of the expandable cage 164 for a given application.
Moreover, the size of the loop diameter can be progressively
tapered to a smaller diameter as the loops approach the obturator
171 of the device so that a sleek tapered shape (helical) may be
maintained. An alternative method for making this particular
expandable cage 164 would include setting the particular shape of
the loops onto a strand of wire, such as by coldwelding a
nickel-titanium wire, to form the preformed shape of the loops. The
loop would remain "set" in the expanded position until a collapsing
force is placed on the expandable cage. In this manner, loops will
be formed in the wire to define the shape of the cage once
expanded.
[0066] The expandable cage of the present invention can be made in
many ways. One particular method of making the cage is to cut a
thin-walled tubular member, such as nickel-titanium hypotube, to
remove portions of the tubing in the desired pattern for each
strut, leaving relatively untouched the portions of the tubing
which form the structure. The tubing may be cut into the desired
pattern by means of a machine-controlled laser. The tubing used to
make the cage could possible be made of suitable biocompatible
material, such as spring steel. Elgiloy is another material which
could possibly be used to manufacture the cage. Also, very elastic
polymers possibly could be used to manufacture the cage.
[0067] The strut size is often very small, so the tubing from which
the cage is made may have a small diameter. Typically, the tubing
has an outer diameter on the order of about 0.020-0.040 inches in
the unexpanded condition. Also, the cage can be cut from large
diameter tubing. Fittings are attached to both ends of the lased
tube to form the final cage geometry. The wall thickness of the
tubing is usually about 0.076 mm (0.001-0.010 inches). As can be
appreciated, the strut width and/or depth at the bending points
will be less. For cages deployed in body lumens, such as PTA
applications, the dimensions of the tubing may be correspondingly
larger. While it is preferred that the cage be made from laser cut
tubing, those skilled in the art will realize that the cage can be
laser cut from a flat sheet and then rolled up in a cylindrical
configuration with the longitudinal edges welded to form a
cylindrical member.
[0068] Generally, the tubing is put in a rotatable collet fixture
of a machine-controlled apparatus for positioning the tubing
relative to a laser. According to machine-encoded instructions, the
tubing is then rotated and moved longitudinally relative to the
laser which is also machine-controlled. The laser selectively
removes the material from the tubing by ablation and a pattern is
cut into the tube. The tube is therefore cut into the discrete
pattern of the finished struts. The cage can be laser cut much like
a stent is laser cut. Details on how the tubing can be cut by a
laser are found in U.S. Pat. No. 5,759,192 (Saunders), U.S. Pat.
No. 5,780,807 (Saunders) and U.S. Pat. No. 6,131,266 (Saunders)
which have been assigned to Advanced Cardiovascular Systems,
Inc.
[0069] The process of cutting a pattern for the strut assembly into
the tubing generally is automated except for loading and unloading
the length of tubing. For example, a pattern can be cut in tubing
using a CNC-opposing collet fixture for axial rotation of the
length of tubing, in conjunction with CNC X/Y table to move the
length of tubing axially relative to a machine-controlled laser as
described. The entire space between collets can be patterned using
the CO.sub.2 or Nd:YAG laser set-up. The program for control of the
apparatus is dependent on the particular configuration used and the
pattern to be ablated in the coding.
[0070] A suitable composition of nickel-titanium which can be used
to manufacture the strut assembly of the present invention is
approximately 55% nickel and 45% titanium (by weight) with trace
amounts of other elements making up about 0.5% of the composition.
The austenite transformation temperature is between about 0.degree.
C. and 20.degree. C. in order to achieve superelasticity at human
body temperature. The austenite temperature is measured by the bend
and free recovery tangent method. The upper plateau strength is
about a minimum of 60,000 psi with an ultimate tensile strength of
a minimum of about 155,000 psi. The permanent set (after applying
8% strain and unloading), is less than approximately 0.5%. The
breaking elongation is a minimum of 10%. It should be appreciated
that other compositions of nickel-titanium can be utilized, as can
other self-expanding alloys, to obtain the same features of a
self-expanding cage made in accordance with the present
invention.
[0071] In one example, the cage of the present invention can be
laser cut from a tube of nickel-titanium (Nitinol) whose
transformation temperature is below body temperature. After the
strut pattern is cut into the hypotube, the tubing is expanded and
heat treated to be stable at the desired final diameter. The heat
treatment also controls the transformation temperature of the cage
such that it is super elastic at body temperature. The
transformation temperature is at or below body temperature so that
the cage is superelastic at body temperature. The cage is usually
implanted into the target vessel which is smaller than the diameter
of the cage in the expanded position so that the struts of the cage
apply a force to the vessel wall to maintain the cage in its
expanded position. It should be appreciated that the cage can be
made from either superelastic, stress-induced martensite NiTi or
shape-memory NiTi.
[0072] The cage could also be manufactured by laser cutting a large
diameter tubing of nickel-titanium which would create the cage in
its expanded position. Thereafter, the formed cage could be placed
in its unexpanded position by backloading the cage into a
restraining sheath which will keep the device in the unexpanded
position until it is ready for use. If the cage is formed in this
manner, there would be no need to heat treat the tubing to achieve
the final desired diameter. This process of forming the cage could
be implemented when using superelastic or linear-elastic
nickel-titanium.
[0073] The struts forming the proximal struts can be made from the
same or a different material than the distal struts. In this
manner, more or less flexibility for the proximal struts can be
obtained. When a different material is utilized for the struts of
the proximal struts, the distal struts can be manufactured through
the lazing process described above with the proximal struts being
formed separately and attached. Suitable fastening means such as
adhesive bonding, brazing, soldering, welding and the like can be
utilized in order to connect the struts to the distal assembly.
Suitable materials for the struts include superelastic materials,
such as nickel-titanium, spring steel, Elgiloy, along with
polymeric materials which are sufficiently flexible and
bendable.
[0074] The connecting struts utilized to connect one or more
circumferential members together are shown generally as straight
segments. However, it is possible to utilize non-linear shapes and
sizes which may provide additional flexibility and bendability
within the patient's anatomy. Additionally, it is possible to make
these connecting struts out of materials which are different from
the rest of the expandable cage to further increase flexibility if
needed. As shown in FIG. 10, the connecting strut could be made in
an S-shape which may provide additional flexibility in certain
curved locations in the patient's anatomy. Moreover, the size and
width of the strut could be varied from the remaining strut widths
and thicknesses in order to promote additional flexibility. In a
similar fashion, the bending regions formed on the circumferential
members could also be formed with thinner and narrower strut widths
than the remaining elements of the cage in order to enhance
flexibility at these bending regions.
[0075] The polymeric material which can be utilized to create the
filtering element include, but is not limited to, polyurethane and
Gortex, a commercially available material. Other possible suitable
materials include ePTFE. The material can be elastic or
non-elastic. The wall thickness of the filtering element can be
about 0.00050-0.0050 inches. The wall thickness may vary depending
on the particular material selected. The material can be made into
a cone or similarly sized shape utilizing blow-mold technology or
dip molding technology. The openings can be any different shape or
size. A laser, a heated rod or other process can be utilized to
create to perfusion openings in the filter material. The holes,
would of course be properly sized to catch the particular size of
embolic debris of interest. Holes can be lazed in a spinal pattern
with some similar pattern which will aid in the re-wrapping of the
media during closure of the device. Additionally, the filter
material can have a "set" put in it much like the "set" used in
dilatation balloons to make the filter element re-wrap more easily
when placed in the collapsed position.
[0076] The materials which can be utilized for the restraining
sheath can be made from polymeric material such as cross-linked
HDPE. This sheath can alternatively be made from a material such as
polyolifin which has sufficient strength to hold the compressed
strut assembly and has relatively low frictional characteristics to
minimize any friction between the filtering assembly and the
sheath. Friction can be further reduced by applying a coat of
silicone lubricant, such as Microglide.RTM., to the inside surface
of the restraining sheath before the sheaths are placed over the
filtering assembly.
[0077] Further modifications and improvements may additionally be
made to the device and method disclosed herein without departing
from the scope of the present invention. Accordingly, it is not
intended that the invention be limited, except as by the appended
claims.
* * * * *