U.S. patent application number 10/285322 was filed with the patent office on 2004-05-06 for single-wire expandable cages for embolic filtering devices.
Invention is credited to Muller, Paul F..
Application Number | 20040088000 10/285322 |
Document ID | / |
Family ID | 32175159 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040088000 |
Kind Code |
A1 |
Muller, Paul F. |
May 6, 2004 |
Single-wire expandable cages for embolic filtering devices
Abstract
A single-wire expandable cage for an embolic filtering device
includes a single cage wire coupled to an elongated member, such as
a guide wire, and adapted to expand from an unexpanded position to
an expanded position in a patient's body vessel. The wire includes
a first end and a second end which are coupled to the guide wire. A
filter element is attached to the single-wire cage. The single-wire
cage may be rotatably mounted to the guide wire or may be slidably
disposed on the guide wire to allow the composite cage and filter
element to be slid over the guide wire in an over-the-wire fashion
once the guide wire is delivered to the target location in the
patient's vasculature. One embodiment of the single-wire cage
utilizes an offset arrangement in which the guide wire remains
extended along the wall of the body vessel once the single-wire
cage is deployed. Another embodiment of the device centers the
guide wire within the body vessel.
Inventors: |
Muller, Paul F.; (San
Carlos, CA) |
Correspondence
Address: |
FULWIDER PATTON LEE & UTECHT, LLP
HOWARD HUGHES CENTER
6060 CENTER DRIVE
TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Family ID: |
32175159 |
Appl. No.: |
10/285322 |
Filed: |
October 31, 2002 |
Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2002/018 20130101;
A61F 2230/008 20130101; A61F 2/01 20130101; A61F 2230/0015
20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. An embolic filtering device used to capture embolic debris in a
body vessel, comprising: a filter assembly including an expandable
cage adapted to move between an unexpanded position and an expanded
position and a filter element attached to the expandable cage, the
cage forming an structure capable of opening the filter element and
maintaining the filter element open until the cage is placed in the
unexpanded position; and an elongated member having a distal end
and a proximal end, the expandable cage being coupled to the guide
wire near the distal end, wherein the cage is made from a
continuous wire having a first end coupled to the guide wire and a
second end coupled to the guide wire, the first end and second end
being spaced apart along the longitudinal axis of the guide
wire.
2. The filtering device of claim 1, wherein the cage forms a spiral
shape when placed in the expanded position.
3. The filtering device of claim 1, wherein the elongated member is
a steerable guide wire.
4. The filtering device of claim 1, wherein the wire is made from a
material which is self expanding.
5. The filtering device of claim 1, wherein the first end and
second end of the expandable cage are rotatably mounted to the
elongated member.
6. The filtering device of claim 1, further including a pair of
stop fittings mounted onto the elongated member, the first end of
the expandable cage being mounted between the pair of stop
fittings.
7. The filtering device of claim 6, wherein the pair of stop
fittings are positioned on the guide wire to allow the first end of
the expandable cage to move longitudinally between the pair of stop
fittings.
8. The filtering device of claim 1, wherein the elongated member is
centered in the body vessel when the expandable cage is deployed
into the expanded position.
9. The filtering device of claim 1, wherein the elongated member is
deployed near the wall of the body vessel when the expandable cage
is deployed.
10. The filtering device of claim 1, wherein the wire forming the
expandable basket is a wire ribbon.
11. The filtering device of claim 10, wherein the wire ribbon is
made from a nickel-titanium alloy.
12. The filtering device of claim 11, wherein the expandable cage
forms a spiral when placed in the expanded position.
13. The filtering device of claim 1, wherein the expandable cage is
slidably mounted to the elongated member to allow the filtering
assembly to be moved along the length of the elongated member.
14. The filtering device of claim 1, further including an obturator
attached to the filtering element.
15. The filtering device of claim 1, wherein the second elongated
member is a tubular member.
16. The filtering device of claim 1, wherein the expandable cage is
movable between its expanded and unexpanded positions through
relative longitudinal movement between the first elongated member
and second elongated member.
17. The filtering device of claim 1, wherein the cage forms a
spiral shape when placed in the expanded position.
18. The filtering device of claim 1, wherein the elongated member
is a steerable guide wire.
19. The filtering device of claim 1, wherein the wire is made from
a material which is self expanding.
20. The filtering device of claim 1, wherein the second elongated
member is a tubular member.
21. The filtering device of claim 6, wherein the expandable cage is
movable between its expanded and unexpanded positions through
relative longitudinal movement between the first elongated member
and second elongated member.
22. The filtering device of claim 1, further including a pair of
stop fittings mounted onto the elongated member, the second end of
the expandable cage being mounted between the pair of stop
fittings.
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 having an expandable cage or basket
made from a single wire that possesses good flexibility and
bendability during delivery.
[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] 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 and bendability 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 NVENTION
[0014] The present invention provides a flexible, single-wire cage
for use with an embolic filtering device designed for capturing,
for example, embolic debris created during the performance of a
therapeutic interventional procedure, such as a balloon angioplasty
or stenting procedure, within a body vessel. The present invention
provides the physician with an embolic filtering device having good
flexibility to be steered through tortuous anatomy while 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 and is easily conformable to the
patient's anatomy.
[0015] An embolic filtering device made in accordance with the
present invention utilizes a single wire to create an expandable
cage. The single-wire cage can be made from a self-expanding
material, for example, nickel-titanium (NiTi), and is 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
single-wire cage to move between the unexpanded position and a
deployed position.
[0016] In one aspect of the present invention, the cage wire is
coupled to the distal end of an elongated member, such as a guide
wire, and is adapted to expand and conform to the size and shape of
the body vessel in which it is deployed. The cage wire has one end
which is coupled to the guide wire and a second end that is
likewise coupled to the guide wire. In one particular aspect of the
invention, the first and second ends of the cage can be rotatably
mounted to the guide wire. The first end and second end of the cage
wire are positioned longitudinally away from each other a certain
distance to allow a spiral configuration to be formed as the wire
unfurls into the expanded position. The spiral created by the cage
wire is adapted to conform within the body vessel of the patient. A
filter element is, in turn, attached to the single-wire cage and
will contact the wall of the body vessel wall once deployed within
the patient. The cage wire can be extremely thin wire, or
alternately, a wire ribbon having an expanded width that provides
additional surface area onto which the filter member can be
attached. The filter member can be attached to the single-wire
cage, for example, by bonding or other attachment techniques
well-known in the art.
[0017] In another aspect of the present invention, the single-wire
cage is not only rotatably mounted onto the guide wire, but has one
end fixed between a pair of stop fittings that limit the
longitudinal travel of the single-wire cage on the guide wire
itself. In this regard, the single-wire cage will be both rotatably
mounted onto the guide wire and will have a limited range of
longitudinal motion along the guide wire as well. In this regard,
if the proximal end of the guide wire is moved or rotated by the
physician, the deployed single-wire cage and filter should remain
stationary within the body vessel and should not move with the
guide wire.
[0018] In another aspect of the present invention, the single-wire
cage is mounted onto the guide wire such that the guide wire
remains substantially centered within the body vessel once the cage
is deployed. In yet another aspect of the present invention, the
single-wire cage remains offset from the center of the body vessel
when deployed. The cage is said to be "offset" in that the guide
wire extends substantially along the vessel wall of the patient,
rather than being "centered" in the body vessel when the
single-wire cage is expanded. In this offset position, there is
little cage structure directly in front of the filter member once
deployed in the open vessel, resulting in a virtually unobstructed
opening for the filter element. The first and second ends of the
single-wire cage can be rotatably connected to the guide wire in
this offset cage arrangement such that the cage wire spirals when
expanded to provide and maintain a satisfactory opening for the
filter member. In this arrangement, the single-wire cage will still
conform to the particular size and shape of the body vessel once
implanted.
[0019] The single-wire cage can be "set" to remain in the expanded,
deployed position until an external force is placed over the cage
wire to collapse and move the cage wire to a 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 single-wire cage and move the
cage into the collapsed position. 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 single-wire cage into the expanded position. This can
be easily performed by the physician by simply retracting the
proximal end of the restraining sheath. Once the restraining sheath
is retracted, the self-expanding properties of the single-wire cage
cause the cage wire to move in an outward, radial fashion away from
the guide wire to contact the wall of the body vessel. As the cage
wire expands radially, so does the filter element which will now be
maintained pressed against the vessel wall 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] In another aspect of the present invention, the single-wire
cage has a "windsock" 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.
[0021] In another aspect of the present invention, the filtering
assembly, which includes the single-wire cage and filter element,
is moveable in a coaxial fashion over the guide wire so as to
permit the guide wire to be first steered into the target area by
the physician, with the filtering assembly being delivered later to
the desired location along the guide wire in an over-the-wire
fashion. In this regard, the filtering assembly is maintained in a
collapsed delivery position by a restraining sheath or other
restraining device so that it may be delivered over the guide wire
to the exact location where the filtering capabilities of the
device is needed. This over-the-wire feature can be implemented
with the embodiment of the single-wire cage in which the guide wire
is centered within the body lumen once the cage is deployed or the
offset version in which the guide wire remains at an offset
location near the side wall of the body lumen.
[0022] 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
[0023] FIG. 1 is a side elevational view of an embolic filtering
device having a single-wire cage embodying features of the present
invention.
[0024] FIG. 2 is a side elevational view of the single-wire cage of
FIG. 1 in its expanded configuration with the filter element
removed to better show the single-wire cage.
[0025] 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 to a location downstream from an area to be
treated.
[0026] 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.
[0027] FIG. 5A is an end view of the single-wire cage of FIG. 1 in
its fully expanded position.
[0028] FIG. 5B is a cross-sectional end view of the single-wire
cage of FIG. 1 in its deployed, expanded position within a body
vessel.
[0029] FIG. 6 is a side elevational view of another embodiment of
an embolic filtering device having a single-wire cage which
embodies features of the present invention.
[0030] FIG. 7 is a side elevational view of an embodiment of an
embolic filtering device having an offset, single-wire cage which
embodies features of the present invention.
[0031] FIG. 8 is an end view of the single-wire cage of FIG. 7 in
its fully expanded position.
[0032] FIG. 9 is a side elevational view of yet another embodiment
of an embolic filtering device having an offset, single-wire cage
which embodies features of the present invention.
[0033] FIG. 10 is cross-sectional view of the guide wire and one
end of the single-wire cage as it is securely fastened to the guide
wire.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] 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,
single-wire 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 also could 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 can be 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
single-wire cage 24 immediately begins to expand within the body
vessel (see FIG. 4), causing the filter element 26 to expand as
well.
[0035] 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.
[0036] 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.
[0037] Referring specifically 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.
[0038] The cage 24 includes a single cage wire 42 which, upon
release from the restraining sheath 30, expands the filter element
26 into its deployed position within the artery (FIG. 4). Embolic
particles 44 created during the interventional procedure and
released into the bloodstream are captured within the deployed
filter element 26. The filter may include perfusion openings 46, or
other suitable perfusion means, for allowing blood flow through the
filter element 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 could 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 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 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.
[0039] Referring again to FIGS. 1 and 2, the single-wire cage 24 is
made from a single-cage wire 42 which has a first end 50 and a
second end 52 attached to the guide wire 28. The cage wire 42 is
shown as a ribbon wire which has additional width that provides an
additional bonding area for attaching the filter element 26
thereto. It should be appreciated that the size of the width of
this cage wire 42 can vary from a very thin width to a width which
is even greater than that shown in FIGS. 1 and 2. The size and
width of the cage wire 42 can accordingly vary as is needed for a
particular application. Additionally, the size and width, and even
thickness of the cage wire 42, can be varied depending upon the
particular material which is utilized in manufacturing of the
wire.
[0040] The single-wire 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. In this regard, the first end 50 and second end 52
are shown rotatably mounted to the guide wire 28. 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 movement of the proximal end of the guide wire
could translate to the deployed filter assembly 22 is prevented.
Therefore, trauma to the wall of the body vessel is minimized.
Referring again to FIGS. 1 and 2, a pair of stop fittings 54 and 56
are placed on the guide wire to maintain the first end 50, and
hence the proximal end of the single-wire cage 24, rotatably fixed
to the guide wire 28. These stop fittings 54 and 56 allow the cage
24 to spin on the guide wire while restricting the longitudinal
movement of the cage on the guide wire. As can be seen in FIG. 1,
the first end 50 of the cage wire 42 can move between the stop
fittings 54 and 56 to allow the cage to have at least some
longitudinal movement on the guide wire. Alternatively, stop
fitting 56 can be moved proximally on the guide wire to prevent
longitudinal motion of the first end 50, while still permitting
rotation. It should be appreciated that the second end 52 of the
cage wire 42 is also movable in the longitudinal direction of the
guide wire in order to move between the expanded and unexpanded
positions. Stop fittings could also be used to limit, or prevent,
longitudinal travel of the second end 52 along the guide wire as
well. Accordingly, it may be preferred to have the obturator 32
slidably disposed along the guide wire as well to allow it to
rotate and move longitidinally along the guide wire when moving
between the unexpanded and expanded positions. This particular
mechanism is just one way in which the single-wire cage 24 can be
mounted to the guide wire 28. Other embodiments disclosed herein
can use similar stop fittings as those described above.
Alternatively, the expandable cage can be attached directly onto
the guide wire so as not to rotate independently.
[0041] Referring now to FIGS. 5A and 5B, an end view of the opening
of the filter element 26 is shown. Referring particularly to FIG.
5A, the end view shows the single-wire cage 24 as it extends in its
most radially expanded position outside of a body lumen. As can be
seen in FIG. 5A, the opening created by the single-wire cage 24 is
not perfectly round, but has a somewhat elliptical shape. However,
once implanted within the body lumen, as is schematically shown in
FIG. 5B, the single-wire cage adapts to the size of the body lumen
such that the single-wire cage becomes more circular to ensure that
there are no gaps formed between the filter element and the wall of
the body lumen. In this regard, the first and second ends of the
cage wire 42 rotate on the guide wire which allows the single-wire
cage to assume a more circular shape once implanted in the body
lumen. As a result, there is little chance of gaps being formed
between the filter element and the wall of the body vessel.
[0042] Referring now to FIG. 6, an alternative embodiment of the
filtering device 20 is shown. In this particular embodiment, the
single-wire cage 24 is shown again rotatably mounted to the guide
wire 28, however, this particular embodiment lacks the pair of stop
fittings which were used on the previously described embodiment
shown in FIGS. 1-4. This will allow the entire filter assembly 22
to move along the length of the guide wire and in fact can be
delivered over the guide wire as a separate filtering element after
the guide wire is initially positioned within the patient's
vasculature. In such an arrangement, the guide wire is first
steered into the target area and then the filter assembly can be
delivered over the guide wire as it is maintained in its
unexpanded, delivery position by a delivery sheath or other
restraining device. The distal end of the filter assembly would
have to come in contact with a stop fittings or fastener (not
shown) which could be located at the distal end of the guide wire
which contacts the filter assembly to prevent it from being
delivered past the distal end of the guide wire. In such an
arrangement, an over-the-wire filtering system can be utilized. It
should also be appreciated that the first and second ends of the
single-wire cage could also be permanently attached to the guide
wire 26 to create a permanent filter/guide wire assembly.
[0043] Referring now to FIGS. 7-9, several alternative embodiments
of the filtering device 20 are shown. Referring initially to FIG.
7, the filtering device 20 is shown as an offset assembly in which
the guide wire 28 will remain close to the wall of the body vessel
once implanted within the patient. This particular embodiment
differs from the one shown in FIGS. 1-6 in that the guide wire 28
would not be centered in the body vessel when implanted. Rather, it
would again remain closer to the side wall of the body vessel. This
particular embodiment has some advantages in that the opening of
the filter element 26 is unimpeded by any portion of the expandable
cage since the expandable cage also remains extended along the
periphery of the vessel wall once implanted. Reference should be
given to FIG. 8 which shows the expanded single-wire cage in its
fully expanded position. As can be seen in FIG. 8, there is
virtually no portion of the single-wire cage that would block the
opening of the filter element. FIG. 8 is similar to FIG. 5A in that
the single-wire cage 24 is shown in its fully expanded position. It
should be appreciated that once implanted into a smaller diameter
body vessel, the single-wire cage will conform to the wall of the
vessel in a manner which is similar to that shown in FIG. 5B.
[0044] FIG. 9 shows another embodiment of the offset filter
assembly of FIG. 7 except that the stop fittings have been removed
from the guide wire to allow the filter assembly to be slidably
disposed on the guide wire. This particular embodiment of the
filtering assembly is again similar to that shown in FIG. 6 in that
the filter assembly could either be permanently attached to the
guide wire or could be slid and delivered across the guide wire in
a coaxial fashion after the guide wire has been steered into the
desired area of the patient's vasculature. This particular
embodiment, as shown in FIG. 9, provides the benefits of an offset
cage with the ability to slide the entire filter assembly over the
guide wire in an over-the-wire fashion.
[0045] Referring now to FIG. 10, the first end 50 of the cage wire
42 is shown as it is attached to the guide wire 28. In this
particular figure, the first end 50 is shown as it extends around
the guide wire 28 and is looped and attached back onto itself, via
a bonding, soldering, braising, or other fastening technique, to
help prevent the end of the cage wire from being accidentally
removed from the guide wire. The previous embodiments of the
filtering assembly show the first and second ends of the cage wire
attached to the guide wire in a loop fashion which helps to
maintain the single-wire cage on the guide wire. The particular
arrangement of the end of the cage wire, as shown in FIG. 10, helps
to prevent the wire from being accidentally removed from the wire
during use. Such a particular arrangement is particularly useful in
the event that the filter assembly is being slid over the guide
wire in a coaxial fashion when used in accordance with the
embodiments shown in FIGS. 6 and 9. Again, this is just one way in
which the ends of the cage wire can be physically attached to the
guide wire.
[0046] 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, leaving
relatively untouched the portions of the tubing which form the
single-wire 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 single-wire
cage.
[0047] The thickness of the wire is often very small, so the tubing
from which the single-wire 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 to form the spiral shape of the cage
wire. The single-wire cage can also be used by just setting a piece
of wire, or wire ribbon, with the desired spiral shape that the
wire makes when attached to the guide wire. In this regard, the
final expanded diameter could be set into the material.
[0048] The single-wire 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.
[0049] Nickel-titanium alloy is yet another material which can be
used to from the single-wire cage due to the self-expanding
properties such a material possesses. A suitable composition of
nickel-titanium which can be used to manufacture the single-wire
cage 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.
[0050] 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
wire 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 its fully expanded position so that the single-wire
cage can apply a force to the vessel wall to maintain the cage and
filter element in its expanded position. It should be appreciated
that the single-wire cage can be made from either superelastic,
stress-induced martensite NiTi or shape-memory NiTi.
[0051] The cage also could 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.
[0052] 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 rewrap more easily
when placed in the collapsed position.
[0053] 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.
[0054] 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.
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