U.S. patent application number 10/954532 was filed with the patent office on 2005-04-07 for offset proximal cage for embolic filtering devices.
Invention is credited to Boyle, William J., Papp, John E..
Application Number | 20050075663 10/954532 |
Document ID | / |
Family ID | 25543798 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050075663 |
Kind Code |
A1 |
Boyle, William J. ; et
al. |
April 7, 2005 |
Offset proximal cage for embolic filtering devices
Abstract
An expandable cage used in conjunction with an embolic filtering
device has a strut configuration including a proximal strut
assembly coupled to a distal strut assembly. A filter can be
attached to the distal strut assembly which has an inlet opening.
The proximal strut assembly is "offset" from the distal strut
assembly in that these proximal struts extend substantially along
the vessel wall of the patient, rather than being "centered" in the
body vessel.,when the cage is expanded in a body vessel. As a
result, there is little cage structure directly in front of the
opening of the filter, resulting in a virtually unobstructed
opening for the filter.
Inventors: |
Boyle, William J.;
(Fallbrook, CA) ; Papp, John E.; (Temecula,
CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
25543798 |
Appl. No.: |
10/954532 |
Filed: |
September 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10954532 |
Sep 30, 2004 |
|
|
|
09997254 |
Nov 27, 2001 |
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2230/0006 20130101;
A61F 2230/0076 20130101; A61F 2230/008 20130101; B82Y 30/00
20130101; B82Y 20/00 20130101; A61F 2230/005 20130101; A61F
2002/018 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A cage for an embolic filtering device used to filter embolic
particles from a body vessel, comprising: a proximal strut assembly
connected to a distal strut assembly which are movable between an
unexpanded position and an expanded position, the distal strut 5
assembly having an inlet opening which expands and conforms to the
wall of the body vessel when placed in the expanded position;
wherein the proximal strut assembly is adapted to extend
substantially along the wall of the body vessel when placed in the
expanded position.
2. The cage of claim 1, wherein the proximal strut assembly is
adapted to be attached to an elongated member.
3. The cage of claim 1, wherein the proximal strut assembly is
adapted to be rotatably attached to an elongated member.
4. The cage of claim 1, wherein a filter member is attachable to
the distal strut assembly.
5. The cage of claim 1, wherein the proximal strut assembly
includes a plurality of expandable struts each having a first end
and a second end, the second ends of the struts being attached to
the distal strut assembly and the first ends being adapted for
attachment to an elongated member.
6. The cage of claim 5, wherein the distal strut assembly includes
a plurality of expandable struts, wherein struts of the distal
strut assembly are arranged to form the inlet opening of the distal
strut assembly.
7. The cage of claim 1, wherein the proximal strut assembly
includes a pair of self-expanding struts.
8. The cage of claim 7, wherein each strut of the proximal strut
assembly has a first end and a second end, the second ends of the
struts being attached to the distal strut assembly and the first
ends being adapted for attachment to an elongated member
9. The cage of claim 8, wherein the struts forming the proximal
strut assembly is made from a different material than the distal
strut assembly.
10. An embolic filtering device used to filter embolic particles
from a body vessel, comprising: an elongated member; a filtering
assembly attached to the elongated member and movable 5 between an
unexpanded position and an expanded position, the filtering
assembly including an expandable cage and a filter member attached
to the expandable cage, the expandable cage including a proximal
strut assembly connected to a distal strut assembly, the filter
member being attached to the distal strut assembly, wherein the
distal strut assembly has an inlet opening which expands and
conforms to the wall of 10 the body vessel to allow embolic
particles to enter the filter member and the proximal strut
assembly is adapted to extend substantially along the wall of the
body vessel when placed in the expanded position.
11. The embolic filtering device of claim 10, further including
means for rotatably attaching the proximal strut assembly to the
elongated member.
12. The embolic filtering device of claim 10, wherein the elongated
member is a guide wire.
13. The embolic filtering device of claim 10, wherein the proximal
strut assembly includes a plurality of expandable struts each
having a first end and a second end, the second ends of the struts
being attached to the distal strut assembly and the first ends
being adapted for attachment to an elongated member.
14. The embolic filtering device of claim 13, wherein the distal
strut assembly includes a plurality of expandable struts, wherein
struts of the distal strut assembly are arranged to form the inlet
opening of the distal strut assembly.
15. The embolic filtering device of claim 10, wherein the proximal
strut assembly includes a pair of self-expanding struts.
16. The embolic filtering device of claim 15, wherein each strut of
the proximal strut assembly has a first end and a second end, the
second ends of the struts being attached to the distal strut
assembly and the first ends being adapted for attachment to the
elongated member.
17. The embolic filtering device of claim 16, wherein the struts
forming the proximal strut assembly is made from a different
material than the distal strut assembly.
18. The embolic filtering device of claim 16, further including a
segment of coil wire attached to and extending from the distal
strut assembly.
19. The embolic filtering device of claim 18, further including an
obturator attached to and extending from the distal strut
assembly.
20. The embolic filtering device of claim 10, wherein the elongated
member continues and extends through the length of the expandable
cage to the distal end of the assembly and includes a distal tip
coil that extends distally from the expandable cage.
21. A method for implanting an embolic filtering device in a body
vessel of a patient for filtering embolic particles entrained in
the patient's body fluid, comprising: providing a filtering
assembly attached to a guide wire and movable between an unexpanded
position and an expanded position, the filtering assembly including
an expandable cage and a filter member attached to the expandable
cage, the expandable cage including a proximal strut assembly
connected to a distal strut assembly, the filter member being
attached to the distal strut assembly, wherein the distal strut
assembly has an inlet opening which expands and conforms to the
wall of the body vessel to allow embolic particles to enter the
filter member and the proximal strut assembly is adapted to extend
substantially along the wall of the body vessel when placed in the
expanded position; maintaining the filtering assembly in the
unexpanded position; maneuvering the filtering assembly into the
desired location in the patient; and moving the filtering assembly
into the expanded position.
22. The method of claim 21, wherein the guide wire is used to
maneuver the filtering assembly in the patient.
23. The method of claim 21, wherein a retractable sheath is used to
maintain the filtering assembly in the unexpanded position.
24. The method of claim 22, wherein the retractable sheath is
retracted to move the filtering assembly into the expanded
position.
25. The method of claim 24, wherein the proximal strut assembly has
two self-expanding struts which extend along the wall of the body
lumen when placed in the expanded position.
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 catheter is usually
used to capture the shaved plaque or thrombus from the bloodstream
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
successfull, 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 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, there can be complications
associated with such systems if the vacuum 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 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] Another problem presented to a physician utilizing an
embolic filtering device is the possible undesired collection of
embolic debris on the struts or ribs that form the cage onto which
the filter is attached. The exposed surface of proximally located
struts provide a potential area where embolic debris can stick,
never reaching the filter positioned downstream from these struts.
As the embolic filtering device is being collapsed for removal from
the patient, it is possible for embolic debris which has become
stuck to these struts to become dislodged and enter the blood
stream. As a result, the design of the embolic filtering device
itself may pose a danger if too many struts are located proximal to
the filter since increased surface area will be exposed to the
embolic particles. Therefore, it may be beneficial to use thin
struts in the proximal region of the filtering device or to reduce
the number of struts forming the self-expanding cage.
[0013] What has been needed is an expandable filter assembly having
high flexibility with sufficient strength to be successfully
deployed within a patient's vasculature to collect embolic debris
which may be released into the patient's vasculature. Moreover, it
would be beneficial if the design of the filtering device reduces
the chances of embolic debris becoming stuck to the struts of the
device, rather than being trapped within the filter. The present
invention disclosed herein satisfies these and other needs.
SUMMARY OF THE INVENTION
[0014] The present invention provides a flexible cage or 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-good flexibility
to allow it to be steered through tortuous anatomy, but yet
possesses sufficient strength to hold open a filtering element
against the wall of the body vessel for capturing embolic debris.
The present invention creates an embolic filtering device that can
be fully deployed within a body vessel and can provide a virtually
unobstructed opening for the filtering element which captures
embolic particles entrained in the body fluid. An embolic filtering
device made in accordance with the present invention is relatively
easy to deploy, has good visibility under flouroscopy, and has good
flexibility and conformability to the patient's anatomy.
[0015] An embolic filter assembly of the present invention utilizes
an expandable cage made from a self-expanding material, for
example, nickel titanium (NiTi) or spring steel, and includes
a-number of outwardly extending struts capable of expanding from an
unexpanded position having a first delivery diameter to an expanded
or deployed position having a second implanted diameter. A filter
element made from an embolic-capturing material is attached to the
expandable cage to move between the unexpanded position and
deployed position.
[0016] The struts of the 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 unexpanded 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
unexpanded position. The embolic filtering device can be implanted
in the patient's vasculature and remain implanted for a period of
time or can be attached to the distal end of an elongated member,
such as a guide wire, for temporary placement in the vasculature. A
guide wire may be used in conjunction with the filtering device
when embolic debris is to be filtered during an interventional
procedure. In this manner, the guide wire and filtering assembly,
with the restraining sheath placed over the filter assembly, can be
placed into the patient's vasculature. Once the physician properly
manipulates the guide wire into the target area, the restraining
sheath can be retracted to deploy the cage 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 each strut to move
in a outward, radial fashion away from the guide wire to contact
the wall of the body vessel. As the struts 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 is
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 procedure.
[0017] In one aspect of the present invention, the enhanced
flexibility and bendability of the embolic, filtering device is
achieved by utilizing a unique cage design which includes an offset
proximal strut assembly attached to a distal strut assembly. A
filtering element is attached to the distal strut assembly and is
expandable within the body vessel for filtering purposes. The
proximal strut assembly is said to be "offset" from the distal
strut assembly in that these proximal struts extend substantially
along the vessel wall of the patient, rather than being "centered"
in the body vessel when expanded. As a result, there is little cage
structure directly in front of the filter in the opened vessel,
resulting in a virtually unobstructed opening for the filter.
[0018] In another aspect of the present invention, the offset
proximal strut assembly is made from a pair of self-expanding
struts which expand to contact the wall of the body vessel once
implanted therein. The distal strut assembly also can be made from
self-expanding struts. In this aspect of the invention, the unique
cage design provides a wide entry opening for the emboli to be
captured within the filtering element. This particular cage design
also enhances wall apposition of the filter once deployed in the
body vessel. The use of two offset struts to form the proximal
strut assembly reduces the chances that emboli could stick to a
strut or become lodged between struts forming the cage. Thus, the
exposed surface area of the cage located proximal to the filter is
greatly minimized which again helps to ensure that the embolic
debris is directed through and captured by the filter.
[0019] In another aspect of the present invention, the cage has a
modified distal strut assembly which creates a "wind sock" type of
filter design that possesses good flexibility and bendability, yet
possesses sufficient radial strength to maintain the filtering
element in an open position once deployed in the body vessel.
[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
embodying features of the present invention.
[0022] FIG. 2 is a perspective view of the expandable cage which
forms part of the embolic filtering device of FIG. 1.
[0023] FIG. 3 is an elevational view, partially in cross section,
of an embolic filtering device embodying features of the present
invention as it is initially being delivered within a body
vessel.
[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, implanted position within the
body vessel.
[0025] FIG. 5 is an end view of the embolic filtering device of
FIG. 1 as it is deployed within a body vessel.
[0026] FIG. 6A is a side elevational view, partially in
cross-section, showing the distal end of the embolic filtering
device of FIG. 1.
[0027] FIG. 6B is a side elevational view, partially in
cross-section, showing the distal end of the embolic filtering
device of FIG. 8.
[0028] FIG. 7 is a side elevational view showing the proximal end
of another embodiment of an expandable cage as it is mounted to an
elongated member, such as guide wire.
[0029] FIG. 7A is a side elevational view, partially fragmented,
showing the proximal end of an expandable cage as it is slidably
mounted to an elongated member, such as guide wire.
[0030] FIG. 7B is a side elevational view, partially in
cross-section and fragmented, of the proximal end of the embodiment
of FIG. 7A as it is affixed to the distal fitting mounted on the
guide wire.
[0031] FIG. 8 is a perspective view of another embodiment of an
embolic filtering device made in accordance with the present
invention.
[0032] FIG. 9 is a perspective view of the expandable cage which
forms part of the embolic filtering device of FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] 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 mounted
on the distal end of an elongated tubular shaft, such as a guide
wire 28. A restraining or delivery sheath 30 (FIG. 3) extends
coaxially along the guide wire 28 to maintain the expandable
filter-assembly 22 in its unexpanded 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 becomes uncovered and immediately begins to
expand within the body vessel (see FIG. 4), causing the filter
element 26 to expand as well.
[0034] An optional obturator 32 affixed to the distal end of the
filter assembly 22 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 preferably 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.
[0035] 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. In FIG. 3, the embolic filtering device 20 is
partially shown as it is being delivered through the patient's
anatomy. This portion of the artery 34 has an area of treatment 36
in which a therosclerotic plaque 38 has built up against the inside
wall 40 of the artery 34. The filter assembly 22 is 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 a variety of arteries or 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.
[0036] The expandable cage 24 of the present invention includes
self-expanding struts which, upon release from the restraining
sheath, expand the filter element 26 into its deployed position
within the artery (FIG. 4). Embolic debris created during the
interventional procedure and released into the bloodstream are
captured within the deployed filter element 26. 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) can be implanted in the area of
treatment 36 using over-the-wire or rapid exchange 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 will 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.
[0037] The expandable cage 24, shown in FIGS. 1-4, includes a
proximal offset strut assembly 42 having a pair of self-expanding
struts 44 that extend radially outward from the unexpanded
position, as shown in FIG. 3, to an expanded, implanted position
shown in FIG. 4. The proximal strut assembly 42 is coupled to a
distal strut assembly 46 which also includes a number of
self-expanding struts 45 that extend radially out once placed in
the expanded position. The filter element 26 is attached to the
distal strut assembly 46 for filtering particles of emboli which
may be released in the artery.
[0038] Referring specifically now to FIGS. 4 and 5, the proximal
strut assembly 42 is shown as it is offset from the center line of
the body vessel and with the distal strut assembly which is
substantially centered within the body vessel. Referring to FIG. 5,
it can be seen that the proximal offset strut assembly 42 extends
from the guide wire 28 outwardly towards the distal strut assembly
46 substantially along the wall 40 of the body vessel. In this
manner, there is little strut surface area located in the front of
the inlet opening 48 of the distal strut assembly/filter where
embolic particles can become lodged. The unique design of the
expandable cage 24 thus allows the distal strut assembly 46-and
filter element 26 to remain centered in the body vessel to provide
proper wall apposition between filter and the body vessel, while
the opening 48 remains virtually unobstructed by proximally located
struts. The design of the expandable cage 24, as shown in FIGS.
1-4, provides an expandable means for deploying a filter element
within the body vessel which is both flexible to reach tortuous
paths in the patient's vasculature and maintains good wall
apposition to prevent the possible discharge of embolic debris past
the deployed filter element 26.
[0039] As is shown in FIG. 4, the filtering assembly 22 is to be
placed-at a downstream location from the area of treatment 36. This
will allow the expandable cage 24 to assume its predetermined shape
once the restraining sheath 30 is retracted from the filtering
assembly 22. It should be appreciated that the guide wire 28, while
shown extending along the vessel wall in FIG. 4, may itself become
centered in the body vessel within the area of treatment once the
medical device is used to perform the interventional procedure is
placed in the area of treatment. However, if the filtering assembly
22 is positioned far enough from the area of treatment (greater
than approximately 2 cm.), this centering of the guide wire within
the area of treatment should not cause the distal most portion of
the guide wire to lift from the vessel wall due to the flexibility
and bendability of the guide wire. As a result, the chances that
the expandable filter assembly 22 can be somewhat dislodged or
misaligned to create a gap between the filter and body vessel after
deployment is minimized.
[0040] As is shown in FIGS. 1 and 2, the expandable basket 24 is
formed as an integral component with the guide wire 28. As such,
the ends 47 of the struts 44 of the offset proximal strut assembly
42 are connected to the distal most end 49 of the guide wire 28.
The distal end of the filter assembly 22 further includes a guide
wire coil 50 which extends from the obturator 32. This guide wire
coil 50 is bendable and allows the physician to maneuver the
composite filtering device 20 into the desired area of the
patient's vasculature. Both the obturator 32 and the guide wire
coil 50 could be made from biocompatible, radiopaque materials to
allow for better visualization under fluoroscopy. This particular
design construction of the guide wire and guide wire coil results
in a cage design which eliminates the presence of a segment of
guide wire which would otherwise extend through the expandable
basket 24. The design of the composite filtering assembly/basket
thus is capable of being collapsed to a small delivery profile. The
unique design of the expandable cage 24 still provides the benefits
of a steerable guide wire while reducing the collapsed profile of
the composite filtering assembly in order to reach tight distal
vessels in the patient's anatomy.
[0041] Referring specifically now to FIG. 6A, the distal most end
of the filtering assembly 22 is shown including the segment of
guide wire coil 50 affixed to both the obturator 32 and distal
strut assembly 46. A tubular member 52 extends through the
obturator 32 to provide a stationary member used for mounting
purposes. The end of the distal strut assembly 46 can terminate at
a collar 54 which can be securely attached to the outer surface 51
of the tubular member 52. The filter element 26 is likewise affixed
to the tubular member 52 to insure that no unwanted openings may
develop at the end of the filtering assembly 22. A portion of the
tubular member 52 is likewise bonded to the obturator 32 to create
a composite unit which should not separate during usage. For
example, the coil 50 can be bonded or adhesively secured to the
inner surface 58 of the tubular member 52 as is shown in FIG. 6A.
In this regard, the various components can be bonded utilizing
suitable biocompatible adhesives known in the art or by utilizing
other known fastening techniques known in the art.
[0042] Referring again back to FIGS. 1 and 2, the specific
structure of the expandable cage 24 can be seen which helps to
provide the unobstructed opening for the filter element 26. As can
be seen best in FIG. 2, the distal strut assembly 46 includes an
opening 60 which formed by a number of struts that make up the
distal strut assembly 46. In the particular embodiment shown in
FIGS. 1 and 2, the opening 60 is designed to articulate to its
expanded position within the body vessel and to conform to the wall
so that proper wall apposition will be maintained between the
filter element 26 and the wall of the body vessel. In the disclosed
embodiment, this opening 60 forms a pair of apices 62 to which the
ends 64 of the struts 44 are attached. It should be appreciated
that the proximal strut assembly could be either formed as a
separate element which is attached to the distal strut assembly 46,
which would allow the proximal strut assembly to be made from a
different material from the distal strut assembly. Alternatively,
the two strut assemblies 42 and 44 could also be formed as a
composite unit from a single piece of material.
[0043] The opening 60 includes a pair of-hinge portions 66 which
allow the opening 60 to open and close. These hinge portions 66 act
like mechanical hinges in the opening and closing of the distal
strut assembly 46. As is shown in FIG. 1, the filter element 26 can
be formed in such a manner to allow it to be adhesively bonded or
otherwise secured to the struts forming the distal strut assembly
46. In this manner, the opening 60 of the distal strut assembly 46
creates the inlet opening for the filter element 26. Again, as is
shown in FIG. 5, the location of the proximal strut assembly 42
along the wall of the body vessel creates a virtually unobstructed
opening for embolic particles to enter into the filter element 26.
It should be appreciated that other designs could be utilized in
conjunction with the proximal and distal strut assemblies without
departing from the spirit and scope of the present invention.
[0044] Referring now to FIG. 7, an alternative mechanism for
attaching the proximal end of the guide wire 28 to the proximal
strut assembly 46 is shown. In this particular example, the ends 47
of the struts 44 are joined at a collar 68 which extends over a
portion of the guide wire 28. The use of the collar 68 allows the
guide wire 28 to spin freely allowing the filtering assembly 22 to
remain stationary in the body vessel even if the proximal end of
the guide wire is rotated accidentally by the physician during
usage. As a result, the filtering assembly 22 should not rotate in
the body vessel which will prevent possible trauma to the wall of
the body vessel. The collar 68 is situated between a pair of stop
fittings 65 and 67 located on the guide wire 28 which maintains the
collar 68 in place. This is one way in which the embolic filtering
assembly 22 can be rotatably mounted onto an elongated member, such
as a guide wire.
[0045] Referring now to FIGS. 7A and 7B, an alternative mechanism
for attaching the proximal end of the strut assembly 46 to the
guide wire 28 is shown. In this particular embodiment, the proximal
collar 68 is not initially fixedly mounted to the guide wire 28.
Rather, the offset cage design could be backloaded over the
proximal end of the guide wire 28 through the inner diameter of the
collar 68. The delivery system could be a rapid exchange device
which could consist of a stiff support structure (not shown) which
allows the physician to advance the collapsed filter assembly over
the guide wire to the intended site within the body. In this
manner, the collapsed filter assembly could be initially kept at
the proximal end of the guide wire until the physician has
maneuvered the distal end of the guide wire into the target in the
patient. Then, the physician would simply slide the rapid exchange
device with the collapsed filter assembly to the distal end of the
guide wire where the cage could be snap-fitted onto the distal
fitting 67. Tabs 69 located on the collar 68 could be
positioned-such that the cage 24 would attach to the distal fitting
67 located on the guide wire 28. As is seen in FIGS. 7A and 7B, the
distal fitting 67 may include an annular recess 71 which receives
one or more of the tabs 69 formed on the collar 68. In this regard,
the physician simply snaps the tabs into the recess 71 by pushing
the rapid exchange device and collapsed filter assembly distally
along the guide wire 28 to contact the fitting 67. As shown in FIG.
7B, the fitting 67 is large enough to abut the collar 68 and
prevent the collar from moving past the fitting during usage. It
should be appreciated that the tab 69 could be formed in other
shapes and sizes, such as an annular ring, which would extend from
the inner surface of the collar 68 and would be adapted to fit
within the annular recess of the distal fitting. It also should be
appreciated that other snap mechanisms could be utilized in order
to attach the proximal collar 68 to the fitting 67. The particular
snap mechanism shown in FIGS. 7A and 7B still allows the expandable
cage 24 to spin freely at the end of the fitting, allowing the cage
to spin freely relative to the guide wire 28.
[0046] An alternative embodiment of an embolic protection device 70
made in accordance with the present invention is shown in FIGS. 8
and 9. In this particular embodiment, the embolic filtering device
70 includes an expandable filter assembly 72 having a modified
version of a self-expanding cage 74 utilized to deploy the filter
assembly 72 from the unexpanded position to the expanded position.
This filter assembly 72 includes a filter element 76 attached to
the self-expanding cage 74. This particular embodiment of the
expandable cage 74 is similar to the embodiment shown in FIGS. 1-5
in that the cage 74 includes an offset proximal strut assembly 78
coupled to a distal strut assembly 80. The proximal strut assembly
78 is offset from the distal strut assembly 80 in a manner that the
struts 82 making up the proximal strut assembly 78 are adapted to
extend along the wall of the body vessel when the filter assembly
72 is deployed in the patient's vasculature. This distal strut
assembly 80 is a modified version of the previously-described
distal strut assembly 46 shown in FIGS. 1-5. In this embodiment,
the distal most struts of this distal strut assembly 80 have been
removed to create a shortened expandable cage 74. The filter
element 76 connected to the struts 84 of the distal strut assembly
80 creates a "windsock" type of filter design since there is a lack
of a strut assembly extending to the obturator 32. As can be seen
in FIG. 8, the filter element 76 takes on somewhat of a tulip-like
shape as it is attached to the struts 84 forming the distal strut
assembly 80. In this regard, the distal strut assembly 80 includes
an opening 86 formed by struts which extend and conform to the wall
of the body vessel once implanted therein. The proximal end of the
filter element 76 is in turn attached to the opening 86 formed by
the distal strut assembly 80 for the collection of embolic
particles which may be entrained in the body fluid. The filter may
have an opening similar to that shown in FIG. 1.
[0047] Additionally, a support wire 85 could be attached to the
guide wire 28 and extend out to the tip coil 50. In this
embodiment, the support wire 85 would be centered in and extend to
the-tip coil 50 once inside the cage 74. This embodiment could
include the proximal connection shown in FIG. 1 along with the
distal connection shown in FIG. 6B. This particular configuration
allows the cage 74 to freely rotate on the guide wire and would
still allow the wire to rotate the coil tip 50 independently from
the cage and delivery sheath. The advantage of this particular
arrangement allows the physician to shape the tip coil and steer
the guide wire through difficult bends and branches of the vessels
by pushing and rotating the guide wire. In this manner, the
physician maintains the steerability of the guide wire from
proximal end to distal coil tip.
[0048] Alternatively, this same support wire 85 could be attached
to the filtering device shown in FIGS. 1 and-2. Again, the
expandable cage would still be rotatably fixed to-the guide wire
but the guide wire would still be steerable to allow the physician
to steer the coil tip to implant the filter assembly into the
desired location in the patient's vasculature.
[0049] It should be appreciated that the support wire is shown as a
separate length of material, which allows it to have a smaller
outer diameter from the guide wire 28 to reduce the profile of the
filter assembly when collapsed. However, the guide wire and support
wire could be made from a continuous piece of wiring, if desired.
Additionally, when a separate length of wiring is used to form the
support wire, a more elastic material than the guide wire could be
used to prevent the filter assembly from becoming too stiff.
[0050] Referring now to FIG. 6B, the connection of the distal end
of the filter element 76 in shown in greater detail. The connection
of the various elements at the distal end of the filtering assembly
72 is similar to the design shown in FIG. 6A. As can be seen in
FIG. 6B, the filter element 76 tapers down to a distal end which is
attached to the outer surface 88 of a mounting member 90 utilized
for mounting the components together. The obturator 32 can be
adhesively bonded to this outer surface 88 as well. A guide wire
coil 50 can likewise extend past the obturator. Since the guide
wire can be rotated by the physician, the wire 85 would not be
bonded to the mounting member 90 in this particular embodiment, but
should remain free to rotate and slide within the mounting member.
In this embodiment, suitable bonding materials known in the art can
be utilized to connect the various elements together.
Alternatively, other fastening techniques known in the art could be
utilized for connecting the components together.
[0051] 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 are to form each strut. The tubing may be cut into the
desired pattern by means of a machine-controlled laser. Prior to
laser cutting the strut pattern, the tubular member could be formed
with varying wall thicknesses which will be used to create the
flexing portions of the cage.
[0052] 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 could be used to manufacture the
cage.
[0053] The strut size is often very small, so the tubing from which
the cage is made must necessarily 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. The wall thickness of the
tubing is usually about 0.076 mm (0.001-0.006 inches). As can be
appreciated, the strut depth at the bending points will be less.
For cages implanted in body lumens, such as PTA applications, the
dimensions of the tubing maybe 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.
[0054] 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. Nos. 5,759,192 (Saunders), U.S. Pat.
Nos. 5,780,807 (Saunders) and U.S. Pat. Nos. 6,131,266 (Saunders)
which have been assigned to Advanced Cardiovascular Systems,
Inc.
[0055] 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.
[0056] A suitable composition of nickel-titanium which can be used
to manufacture the strut assembly of the present invention is
approximately 55% nickel and U.S. Pat. Nos. 45% titanium (by
weight) with trace amounts of other elements making up about U.S.
Pat. Nos. 0.5% of the composition. The austenite transformation
temperature is between about 0.degree. C. and 20.degree. C. in
order to achieve superelasticity. 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 approximately
0.5%. The breaking elongation is a minimum of 10%. It should be 5
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.
[0057] 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.
[0058] Another way of making the cage of the present device is to
utilize a shape-memory material, such as nickel titanium, which has
the struts cut utilizing a machine-controlled laser. A tubular
piece of material could be utilized in this process. The cage could
be manufactured to remain in its open position while at body
temperature and would move to its unexpanded position upon
application of a low temperature. One suitable method to allow the
cage to assume a change phase which would facilitate the strut and
filter assembly being mounted into the restraining sheath include
chilling the filter assembly in a cooling chamber maintained at a
temperature below the martensite finish temperature through the use
of liquid nitrogen. Once the cage is placed in its collapsed state,
the restraining sheath can be placed over the cage to prevent the
cage from expanding once the temperature is brought up to body
temperature. Thereafter, once the filtering device is to be
utilized, the restraining sheath is simply retracted to allow the
cage to move to its expanded position within the patient's
vasculature. If super elastic NiTi is used, the cage/filter
assembly can be simply back loaded into the restraining sheath. The
cage would be "set" to the expanded position.
[0059] 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 nickel-titanium or
shape-memory nickel-titanium.
[0060] The struts forming the struts of the proximal strut assembly
can be made from the same or a different material than the distal
strut assembly. In this manner, the additional or less flexibility
for the proximal strut assembly can be obtained. When a different
material is utilized for the struts of the distal proximal strut,
the distal strut assembly; can be manufactured through the lazing
process described above with the struts of the proximal strut
assembly being formed separately and attached to the distal
assembly. 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. Also,
although two struts are shown forming the proximal strut assembly
in the disclosed embodiments, it will be appreciated by those
skilled in the art that additional struts could also be utilized to
form this assembly without departing from the spirit and scope of
the present invention.
[0061] 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. 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
vice. 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.
[0062] 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.
[0063] 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.
* * * * *