U.S. patent application number 10/354831 was filed with the patent office on 2004-08-05 for embolic filters with a distal loop or no loop.
Invention is credited to Kusleika, Richard S., Oslund, John C...
Application Number | 20040153119 10/354831 |
Document ID | / |
Family ID | 32770431 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040153119 |
Kind Code |
A1 |
Kusleika, Richard S. ; et
al. |
August 5, 2004 |
Embolic filters with a distal loop or no loop
Abstract
The invention provides a device for filtering emboli from blood
flowing through a lumen defined by the walls of a vessel in a
patient's body, comprising a filter element and a self-expanding
radial element associated with the filter element. The filter
element is expandable from a collapsed configuration when the
filter element is restrained to an expanded configuration when the
filter element is unrestrained. The filter element comprises a
self-expanding material having pores. The filter element has
proximal and distal portions and a central portion, and has a shape
in the expanded configuration which defines a cavity having a
proximal facing opening. The self-expanding radial element is
distal of the filter element, and the self-expanding radial element
is adapted to maintain the filter element centered in the
lumen.
Inventors: |
Kusleika, Richard S.; (Eden
Prairie, MN) ; Oslund, John C..; (Blaine,
MN) |
Correspondence
Address: |
POPOVICH, WILES & O'CONNELL, PA
650 THIRD AVENUE SOUTH
SUITE 600
MINNEAPOLIS
MN
55402
US
|
Family ID: |
32770431 |
Appl. No.: |
10/354831 |
Filed: |
January 30, 2003 |
Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2230/0008 20130101;
A61F 2230/0067 20130101; A61F 2/011 20200501; A61F 2/01 20130101;
A61F 2002/018 20130101; A61F 2002/015 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A device for filtering emboli from blood flowing through a lumen
defined by the walls of a vessel in a patient's body, comprising: a
filter element being expandable from a collapsed configuration when
the filter element is restrained to an expanded configuration when
the filter element is unrestrained, wherein the filter element
comprises a self-expanding material having pores, wherein the
filter element has proximal and distal portions and a central
portion, the filter element having a shape in the expanded
configuration which defines a cavity having a proximal facing
opening; and a self-expanding radial element associated with the
filter element, wherein the self-expanding radial element is distal
of the filter element, and the self-expanding radial element is
adapted to maintain the filter element centered in the lumen.
2. A device of claim 1, wherein the self-expanding radial element
comprises a loop, and wherein the loop is generally circular in
shape.
3. A device of claim 2, wherein the self-expanding radial element
has one loop.
4. A device of claim 2, wherein the self-expanding radial element
comprises two or more loops.
5. A device of claim 4, wherein the self-expanding radial element
has two loops.
6. A device of claim 1, wherein the filter element is attached to
the self-expanding radial element by a fixed or sliding
element.
7. A device of claim 6, wherein the fixed or sliding element is a
sliding element.
8. A device of claim 1, further comprising an elongate support
member and wherein the filter element is carried on a portion of
the elongate support member.
9. A device of claim 8, wherein the filter element is attached to
the elongate support member at the distal portion of the filter
element.
10. A device of claim 9, wherein the filter element is attached to
the elongate support member at the distal portion of the filter
element by a fixed or sliding element.
11. A device of claim 10, wherein the fixed or sliding element is a
sliding element.
12. A device of claim 9, wherein the elongate support member is
attached to the filter element at the proximal portion of the
filter element.
13. A device of claim 10, wherein the elongate support member is
attached to the filter element at the proximal portion of the
filter element.
14. A device of claim 13, wherein the elongate support member is
attached to the filter element at the proximal portion of the
filter element by a sliding element.
15. A device of claim 13, wherein the elongate support member is
attached to the filter element at the proximal portion of the
filter element by a single flexible tether.
16. A device of claim 1, wherein the self-expanding radial element
is adapted to not significantly impede the flow of blood through
the lumen.
17. A device of claim 1, wherein the device does not comprise any
other self-expanding elements other than the self-expanding
material having pores and the self-expanding radial element.
18. A device of claim 1, wherein the self-expanding radial element
is made of nitinol wire.
19. A device of claim 1, wherein when the self-expanding radial
element is in its expanded configuration, the self-expanding radial
element generally defines a plane substantially perpendicular to
the elongate support member.
20. A device of claim 1, wherein when the filter element is in the
expanded configuration, the average pore size is from 30 to 300
microns and the standard deviation of the pore size is less than 20
percent of the average pore size.
21. A device of claim 1, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 50 percent.
22. A device of claim 1, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 60 percent.
23. A device of claim 1, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 70 percent.
24. A device of claim 1, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 80 percent.
25. A device of claim 1, wherein the self-expanding material having
pores has a tensile strength greater than 70,000 psi.
26. A device of claim 1, wherein the self-expanding material having
pores has a tensile strength greater than 100,000 psi.
27. A device of claim 1, wherein the self-expanding material having
pores has a tensile strength greater than 200,000 psi.
28. A device of claim 1, wherein the self-expanding material having
pores is made of metal.
29. A device of claim 1, wherein the self-expanding material having
pores is made of nitinol.
30. A device of claim 1, wherein the self-expanding material having
pores comprises wires braided to form diamond-shaped pores.
31. A device for filtering emboli from blood flowing through a
lumen defined by the walls of a vessel in a patient's body,
comprising: a filter element being expandable from a collapsed
configuration when the filter element is restrained to an expanded
configuration when the filter element is unrestrained, wherein the
filter element comprises a self-expanding material having pores,
wherein the filter element has proximal and distal portions and a
central portion, the filter element having a shape in the expanded
configuration which defines a cavity having a proximal facing
opening; and an elongate support member, wherein the filter element
is carried on a portion of the elongate support member, wherein the
filter element is attached to the elongate support member at the
distal portion of the filter element, and wherein the elongate
support member is attached to the filter element at the proximal
portion of the filter element by a single flexible tether.
32. A device of claim 31, wherein the single flexible tether is
attached to the elongate support member by a fixed or sliding
element disposed on the elongate support member.
33. A device of claim 31, wherein the fixed or sliding element is a
sliding element.
34. A device of claim 31, wherein the fixed or sliding element is a
fixed element.
35. A device of claim 33, further comprising a stop on the elongate
support member distal of the sliding element.
36. A device of claim 31, wherein the filter element is attached to
the elongate support member at the distal portion of the filter
element by a fixed or sliding element.
37. A device of claim 36, wherein the fixed or sliding element is a
sliding element.
38. A device of claim 33, wherein the filter element is attached to
the elongate support member at the distal portion of the filter
element by a second sliding element.
39. A device of claim 34, wherein the filter element is attached to
the elongate support member at the distal portion of the filter
element by a sliding element.
40. A device of claim 35, wherein the filter element is attached to
the elongate support member at the distal portion of the filter
element by a second sliding element.
41. A device of claim 31, wherein the flexible tether is a metal
wire with a diameter less than 0.30 mm.
42. A device of claim 41, wherein the flexible tether has a
diameter less than 0.20 mm.
43. A device of claim 41, wherein the metal wire is stranded
wire.
44. A device of claim 31, wherein the flexible tether is made of
nitinol wire.
45. A device of claim 31, wherein the flexible tether is made of
stranded nitinol wire.
46. A device of claim 45, wherein the stranded nitinol wire has a
diameter less than 0.30 mm.
47. A device of claim 45, wherein the stranded nitinol wire has a
diameter less than 0.20 mm.
48. A device of claim 31, wherein the device does not comprise any
other self-expanding elements other than the self-expanding
material having pores.
49. A device of claim 31, wherein when the filter element is in the
expanded configuration, the average pore size is from 30 to 300
microns and the standard deviation of the pore size is less than 20
percent of the average pore size.
50. A device of claim 31, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 50 percent.
51. A device of claim 31, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 60 percent.
52. A device of claim 31, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 70 percent.
53. A device of claim 31, wherein when the filter element is in the
expanded configuration, the filter element has a percent open area
greater than 80 percent.
54. A device of claim 31, wherein the self-expanding material
having pores has a tensile strength greater than 70,000 psi.
55. A device of claim 31, wherein the self-expanding material
having pores has a tensile strength greater than 100,000 psi.
56. A device of claim 31, wherein the self-expanding material
having pores has a tensile strength greater than 200,000 psi.
57. A device of claim 31, wherein the self-expanding material
having pores is made of metal.
58. A device of claim 31, wherein the self-expanding material
having pores is made of nitinol.
59. A device of claim 31, wherein the self-expanding material
having pores comprises wires braided to form diamond-shaped pores.
Description
FIELD OF THE INVENTION
[0001] This invention relates to devices used in a blood vessel or
other lumen in a patient's body. In particular, the present
invention relates to devices for capturing emboli and particulate
in a lumen.
BACKGROUND OF THE INVENTION
[0002] During vascular surgery or endovascular treatment of vessels
including thrombectomy, atherectomy, balloon angioplasty, and/or
stent deployment, debris such as plaque and blood clots can move
from the treatment site through a vein or artery and compromise the
flow of blood at a location removed from the treatment site. In
particular, various protection systems have been developed to
prevent such debris from embolizing in the vessel. Distal
protection devices include filters and occlusive devices (e.g.,
balloons) placed distally of the treatment site. Proximal
protection devices include filters and occlusive devices placed
proximally of the treatment site. In the case of filters, emboli
collect within or on the filter. The filter with captured emboli is
typically collapsed into a recovery catheter and the catheter
withdrawn from the patient's body.
[0003] In prior art filters it has been found that incorrect radial
position of the filter within a body conduit can compromise the
performance of the filter. Specifically, if a portion of the filter
abuts a vessel wall, then the area of the filter available for
performing the filtering function is reduced. Further, radial
motion of an elongate member can cause the filter to lose wall
apposition and thereby defeat the intended embolic capture function
of the filter.
[0004] Most filters are mounted onto elongate support members, and
the filters are comparatively flexible as compared to the elongate
support members to which they are mounted. Radial motion of the
elongate support member is often a consequence of back and forth
axial motion of the elongate support member in tortuous body
conduits. Radial motion of the elongate support member can compress
the filter, causing it to lose apposition to the conduit wall and
thereby defeat the intended embolic capture function. Control of
elongate member radial position by use of proximal loops is
discussed in U.S. Ser. No. 09/628,212, filed Jul. 28, 2000,
entitled "Improved Distal Protection Device" and U.S. Ser. No.
10/093,572, filed Mar. 8, 2002, entitled "Distal Protection Devices
Having Controllable Wire Motion," the contents of each of which are
hereby incorporated by reference herein. Radial motion of the
elongate support member can also press the filter against a conduit
and reduce the area available for filtering emboli.
[0005] A need in the art remains for an embolic protection filter
in which an elongate support member does not cause the filter to
have excessive contact with a body conduit, thereby decreasing the
filter area available for performing the filtering function.
SUMMARY OF THE INVENTION
[0006] The invention provides an embolic protection filter in which
an elongate support member does not cause the filter to have
excessive contact with a body conduit, thereby decreasing the
filter area available for performing the filtering function. The
invention also provides an embolic protection filter in which
radial wire motion does not compromise filter wall apposition
[0007] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1A is a side view and FIG. 1B is a cross sectional view
of a prior art filter deployed in a body conduit.
[0009] FIG. 2A is a side view and FIG. 2B is a cross sectional view
of an embodiment of the invention showing a distal loop.
[0010] FIG. 3 is a side view of an embodiment of the invention
showing a distal loop and a tether.
[0011] FIG. 4 is a side view of an alternate embodiment of a filter
of this invention.
[0012] FIG. 5 is a side view of a no loop filter.
[0013] FIG. 6 is a side view of an alternate embodiment of a no
loop filter.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The terms "distal" and "proximal" as used herein refer to
the relative position of the elongate support member, catheters,
and filter in a lumen. Thus, "proximal" refers to a location
upstream from the "distal" position. That is, the flow of a body
fluid, such as blood, moves from the proximal to the distal
portions of the device.
[0015] The invention encompasses the use of any filtration device
to be deployed in a lumen or vessel of a patient. Although the
examples relate generally to filter protection devices deployed
distal to a treatment site, the device can also be deployed
proximal to a treatment site in connection with interrupting or
reversing flow through the vessel. In the case of a proximally
deployed device, it will be advantageous to construct the device on
a hollow elongate member so as to preserve access to the treatment
site through the hollow member.
[0016] In a preferred embodiment, the distal protection system
comprises a catheter which is loaded with an elongate support
member or guidewire about which is disposed a distal protection
filter. The elongate support member is structurally similar to a
traditional guidewire in some respects. However, it is not used as
a means of navigating the patient's vascular system and, therefore,
does not need to be provided with all of the features of
flexibility and steerability as does a traditional guidewire. With
these differences in mind, the terms elongate support member and
guidewire may be used interchangeably herein. A floppy tip
(described further below) may be at the distal end of the elongate
support member or guidewire. Typically, the filter is introduced
into a blood vessel through an introducing catheter. Methods of
introducing guidewires and catheters and the methods for the
removal of such devices from vessels are well known in the art of
endovascular procedures. In a typical procedure using the device of
this invention, the elongate support member and filter are loaded
into an introducing sheath or catheter and moved into the vessel
and through the catheter to the treatment site. Typically, this is
done by advancing a first, or introduction guidewire, through the
vessel to the region of interest. A catheter is advanced over the
guidewire to the region of interest, and the guidewire removed.
Then the filter or other functional device carried by the elongate
support member is advanced down a catheter sheath to the region of
interest but within the catheter. The catheter sheath is withdrawn
to deploy (expand) the filter at the region of interest.
Alternatively, the filter is preloaded into a catheter and held in
place by an outer sheath of the catheter and they are together
advanced through the vessel to the region of interest without using
an initial guidewire. In this embodiment the catheter/filter
combination will be used to navigate through the vessel to the
region of interest. Then the catheter is withdrawn to deploy the
filter. In a second alternative, an introduction guidewire is
advanced to the region of interest, and the filter (contained in a
catheter) is advanced over the guidewire to the region of interest,
at which point the catheter is removed leaving the deployed filter
near the region of interest on the guidewire. In this embodiment
the filter is not comprised of an elongate support member as
previously defined, and the guidewire and/or filter may be
configured to preserve a spatial relationship between the guidewire
and the filter. For example, the guidewire may be configured to
prevent the filter from advancing beyond the distal end of the
guidewire.
[0017] In other embodiments of the invention, no catheter is
required for filter delivery. For example, the filter may be
stretched axially so as to reduce its diameter to a size suitable
for navigation through a vessel and across a treatment site.
[0018] Typical dimensions of a filter used in the devices of this
invention range from 2 mm to 90 mm in length, and from about 0.5 mm
to 2 mm in diameter before deployment, and from about 2 mm to 30 mm
in diameter after deployment. A typical guidewire is about 0.2 to
1.0 mm in diameter and ranges from 50 cm to 320 cm in length.
[0019] The components of the distal protection system are made from
biocompatible materials. Materials also may be surface treated to
produce biocompatibility. The elongate support member may be formed
of any material of suitable dimension, and preferably comprises
metal wire. Suitable materials include stainless steel, titanium
and its alloys, cobalt-chromium-nickel-molybdenum-iron alloy
(commercially available under the trade designation Elgiloy.TM.),
carbon fiber and its composites, and engineered polymers such as
liquid crystal polymers, polyetheretherketone (PEEK), polyimide,
polyester, and the like. A shape memory or superelastic metal such
as nitinol is also suitable. The elongate support member may be
solid or may be hollow over some or all of its length.
[0020] The material used to make the filter or filter support
structure is preferably self-expanding. Suitable materials include
metals such as stainless steel, titanium and its alloys,
cobalt-chromium-nickel-molybden- um-iron alloy (commercially
available under the trade designation Elgiloy.TM.), carbon fiber
and its composites, and engineered polymers such as liquid crystal
polymers, polyetheretherketone (PEEK), polyimide, polyester, silk,
and the like. A shape memory or superelastic metal is particularly
suitable for those applications when it is desired for an element,
such as a filter, to assume a pre-determined three-dimensional
shape or for a guidewire to maintain a pre-determined curvature. A
shape memory or superelastic metal comprising nickel and titanium
known as "nitinol" is commercially available in various dimensions
and is suitable for use as both a guidewire and a filter. For
example, nitinol tubular braid can be heat set into a desired
shape, compressed for delivery to a site, and then released to
resume the heat-set shape.
[0021] The filter element has a body defining an interior cavity.
The filter body has a plurality of openings or pores such that,
when the filter element is in its deployed configuration within the
vessel lumen, fluid flows through the filter element and particles
of the desired size are captured inside the interior cavity of the
filter element.
[0022] The filter may comprise any material that is suitably
flexible and resilient, such as a mesh, i.e., a material having
openings or pores. The filter may comprise braided, knitted, woven,
or non-woven fabrics that are capable of filtering particles,
preferably having pore sizes from 30 to 500 microns. Woven or
non-woven fabrics may additionally be treated to fuse some or all
of the fiber intersections. The fabric may be spun or electrospun.
Suitable materials include those formed from sheets, films, or
sponges, polymeric or metallic, with holes formed by mechanical
means such as laser drilling and punching, or by chemical means
such as selective dissolution of one or more components. For
example, a suitable filter material is braided tubular fabric
comprising superelastic nitinol metal. Mesh fabric of nitinol
material can be heat-set to a desired shape in its expanded
configuration.
[0023] The material comprising the filter is preferably at least
partially radiopaque. This material can be made radiopaque by
plating, or by using core wires, tracer wires, or fillers that have
good X-ray absorption characteristics compared to the human body.
Radiopaque filters are described in U.S. patent application Ser.
No. 10/165,803, filed Jun. 7, 2002, entitled "Radiopaque Distal
Embolic Protection Device," the contents of which are hereby
incorporated by reference herein.
[0024] The embodiments of this invention, described in detail below
in connection with the figures, are suitable for use with various
distal protection systems that are known in the art. The filter may
have a windsock type shape. The construction, deployment and
retrieval of a filter having this shape is described, for example,
in U.S. Pat. No. 6,325,815 B1 (Kusleika et al.), the contents of
which are hereby incorporated by reference herein.
[0025] The filter may also be a cup-shaped or basket-shaped device
which forms a proximally facing opening when expanded. The
construction, deployment, and retrieval of such a filter is
described in WO 96/01591 (Mazzocchi et al.). This cup-shaped device
may generally resemble an umbrella or a parachute, having a
dome-like structure curving radially outwardly from the guidewire
or elongate support member. Other shapes may be equally suitable in
performing a filtering function, such as a conical shape, or a
relatively flat disc shape. It will be appreciated that the shape
of these filtration devices shown in various embodiments are merely
illustrative and are not meant to limit the scope of the
invention.
[0026] Regardless of the shape of the filter, the filter preferably
is deployed using an elongate support member. This can be done in
various ways, and one or both of the proximal and distal ends of
the filter may be affixed to the elongate support member (by a
fixed element) or may be slidably disposed about the elongate
support member (by one or more sliding elements).
[0027] One type of sliding element comprises inner and outer
annular rings. The first ring fits within the second ring. The
inner diameter of the first ring is larger than the diameter of the
elongate support member so that the sliding element can slide over
the elongate support member. The sliding element can be affixed to
the filter fabric by placing the fabric between the first and
second rings. However, this is not meant to be limiting, and the
filter fabric can also be affixed to the sliding element by
adhesive, solder, crimping, or other means known in the art. The
sliding element may comprise any stiff material such as metal or
polymer and preferably the slider is radiopaque. Suitable materials
include stainless steel, titanium, platinum, platinum/iridium
alloy, gold alloy, polyimide, polyester, polyetheretherketone
(PEEK), and the like. Movement of a sliding element with respect to
the elongate support member can be facilitated by coating one or
both of the inside of the sliding element and the outside of the
elongate support member with a friction-reducing coating, such as
polytetrafluoroethylene or a lubricious hydrophilic coating.
[0028] Fixed elements include annular rings. Also included within
this meaning is an element that is crimped, adhered, soldered, or
otherwise fastened directly to the elongate support member. Also,
the filter fabric may be attached directly to the elongate support
member. In any event, the sliding and fixed elements (or any
attachment point) typically comprise radiopaque material to assist
in the placement of the filter. In addition, one or more radiopaque
markers may be positioned at various locations on the protection
device. These radiopaque markers or marker bands comprise a
material that will be visible to X-rays and they assist in
positioning the device.
[0029] Some distal protection filters include a floppy tip at a
distal portion of the guidewire or elongate support element. The
floppy tip provides an atraumatic and radiopaque terminus for the
device. An atraumatic tip prevents vessel injury during initial
placement or subsequent advancement of the device. A radiopaque tip
helps the physician verify suitable tip placement during
fluoroscopy. The floppy tip preferably comprises a springy or
resilient material, such as a metal (e.g., stainless steel, iron
alloys such as Elgiloy.TM., platinum, gold, tungsten, and shape
memory or superelastic metal such as nitinol) or polymer (e.g.,
polyetheretherketone (PEEK), polyimide, polyester,
polytetrafluoroethylene (PTFE), and the like). Springy materials
are desirable because they tend to retain their shape. The
physician will initially shape the tip, typically with a slight
curve, and then as the device is advanced through the body the tip
will be deflected as it encounters obstacles. It is desirable,
after the inevitable deflections during insertion, that the tip
restore itself to the pre-set shape. Polymeric materials
additionally may be reinforced with metals or other fillers. The
tip may be a monofilament or multifilament (such as a cable). The
floppy tip may be tapered or have a uniform diameter over its
length. The floppy tip may comprise a tube, or could have circular,
flat, or other cross-sections. It may be coiled. The tip may
comprise one or more elements (for example, parallel independent
structures). The tip may be polymer-coated or otherwise treated to
make the surface slippery. The floppy tip can be any desired
length.
[0030] The filter comprises biocompatible materials such as metals
and polymeric materials. Materials such as metals and polymeric
materials can be treated to impart biocompatibility by various
surface treatments, as known in the art. When wire is used, the
wire is selected on the basis of the characteristic desired, i.e.,
stiffness or flexibility, and the properties can depend upon both
the diameter of the wire and its cross-sectional shape. The size,
thickness, and composition of elastic materials are selected for
their ability to perform as desired as well as their
biocompatibility. It is to be understood that these design elements
are known to one of skill in the art.
[0031] Filters are typically constructed as described in U.S. Pat.
No. 6,325,815 B1. See column 3, line 63, to column 4, line 16; and
column 4, line 48, to column 5, line 36. The filter body typically
comprises a length of a braided tubular fabric, preferably made of
nitinol. The filter body is typically made by placing a braided
tubular fabric in contact with a molding surface of a molding
element which defines the shape of the desired filter body. By heat
treating the braided tubular fabric in contact with the molding
surface of the molding element, one can create a filter body having
virtually any desired shape.
[0032] Braiding is a process for producing a tubular interwoven
structure from individual strands. Braids are typically produced in
continuous lengths on commercially available braiding machines.
Some commercial products produced on braiding machines include
rope, shoelaces, and reinforcing jackets for electrical cable.
Medical products produced by braiding include stents, vascular
grafts, and catheter reinforcing layers.
[0033] In a typical braiding process for making a 72 stranded
braid, lengths of strands, such as wire, are wound onto bobbins. In
this example 72 bobbins are wound with wire. Each bobbin is loaded
into the carrier of a 72 carrier braiding machine. Typically
braiding machines for medical use have from 16 to 144 carriers or
more. Each wire is led through a tensioning mechanism in the
carrier and all wire strands are gathered at a common central
elevated position along the (typically vertical) axis of the
braiding machine, where they are fastened to a take-up mechanism.
The take-up mechanism may be a long mandrel arranged along the axis
of the braiding machine and onto which the braid is formed during
the braiding process. Once so configured, the carriers are rotated
relative to the axis of the braiding machine. The carriers are
rotated in a serpentine path, half of them moving clockwise and the
other half moving counterclockwise, so as to interweave the strands
in a programmed pattern. While the carriers are rotating, the
take-up mechanism advances the woven braid in a direction away from
the carriers. The combination of these motions produces a helix of
strands twisting in a clockwise direction along the mandrel,
interwoven with a helix of strands twisting in a counterclockwise
direction along the mandrel. In this manner continuous lengths of
braid are produced with an inside diameter of the braid equal to
the outside diameter of the braiding mandrel. The individual braid
strands, while still on the mandrel, can be twisted together after
the length of the mandrel has been braided. If desired, after
removing the mandrel from the braiding machine, the strands can be
heat-treated. In the case of nitinol strands, heat treatment on the
mandrel at about 525.degree. C. for 10 minutes or so can cause the
nitinol-braided fabric to remember the shape and size of the
mandrel when the nitinol is at rest.
[0034] The average pore sizes of filters of the invention
preferably range from 30 to 300 microns. In another preferred
embodiment, the average pore sizes range from 30 to 150 microns. A
pore size of about 120 microns is preferred for devices intended to
be used in connection with coronary procedures and a pore size of
about 50 microns is preferred for devices intended to be used in
connection with carotid or intracranial procedures. The variation
in pore size within the filter should be minimized. In preferred
embodiments of the invention, the standard deviation of the pore
size is less than 20 percent of the average pore size. In other
preferred embodiments, the standard deviation of the pore size is
less than 15, 10, 5, or 2 percent of the average pore size.
[0035] The percent open area of the filters of the invention is
preferably greater than 50 percent. In other preferred embodiments,
the percent open area is greater than 60, 70, or 80 percent. A
standard formula is used to calculate the percent open area of a
given design. The percent open area is calculated by dividing the
total pore area by the total filter area (including the pore
area).
[0036] The filters of the invention preferably are made of a
material having a tensile strength of greater than 70,000 psi (7031
kg/cm.sup.2), more preferably greater than 150,000 psi (14,062
kg/cm.sup.2), and more preferably greater than 200,000 psi (17,578
kg/cm.sup.2). Cast polymer films have a maximum tensile strength of
about 10,000 psi (703 kg/cm.sup.2); oriented polymer films have a
tensile strength as high as 50,000 psi (3516 kg/cm.sup.2), and
metal filters typically contain wires having a tensile strength of
from 70,000 to 300,000 psi (7031 kg/cm.sup.2 to 21,093
kg/cm.sup.2).
[0037] The various embodiments of the invention will now be
described in connection with the drawing figures. It should be
understood that for purposes of better describing the invention,
the drawings have not been made to scale. Further, some of the
figures include enlarged or distorted portions for the purpose of
showing features that would not otherwise be apparent. The material
comprising the filter (e.g., mesh or fabric with pores, as
described above) is omitted in the figures for simplicity.
[0038] It is to be understood that the following embodiments are
useful for any shape or type of filter. For example, these
embodiments are useful for any filter deliverable by any manner to
a desired position in a body lumen where control of the desired
characteristics of the filter as set forth above is desired. In
particular, the invention includes both proximal and distal
filters.
[0039] FIG. 1A illustrates a prior art distal protection system in
which windsock-shaped filter 10 is attached to elongate support
member 15 via distal sliding element 18. For clarity, the mesh of
the filter is not drawn in the figure. At the proximal end of the
filter, proximal sliding element 16 is slidably disposed about the
elongate support member and attached to filter 10. Stop 12 is
provided on the elongate support member in order to limit the
relative motion of the filter along the support member. Support
member 15 terminates distally at floppy tip 15b.
[0040] When deployed in a vessel V, filter 10 has wall apposition
regions 11 at the proximal end of the filter and along the vessel
wall. FIG. 1B shows filter 10 and wall apposition regions 11 in
cross section. Fluid flow cannot pass through filter 10 in wall
apposition regions 11 because there is no space between the filter
and the vessel in this region. In the case of a braided structure,
flow cannot pass through distal portion of mesh 17 because the
pores are generally very small. Most flow is confined to passing
through the central portion 13 of filter 10.
[0041] Distal Loop Filters
[0042] FIG. 2A is a side view and FIG. 2B is a cross sectional view
of an embodiment of the present invention. Windsock-shaped filter
20 is attached to elongate support member 25 via distal sliding
element 28. For clarity, the mesh of the filter is not drawn in the
figure. At the proximal end of the filter, proximal sliding element
26 is slidably disposed about the elongate support member and
attached to filter 20. Stop 22 is provided on the elongate support
member in order to limit the relative motion of the filter along
the support member. Stop 22 may be a wire coil or a hypotube,
polymer or metal, solid, or cut to improve its flexibility. Stops
and the use of stops are described in U.S. Ser. No. 10/060,271,
filed Jan. 30, 2002, entitled "Slidable Vascular Filter," the
contents of which are hereby incorporated by reference herein.
Support member 25 terminates distally at floppy tip 25b. Distal
loop 24 attaches to distal sliding element 28 and contacts vessel
wall. Distal loop 24 may be made of elastic material such as metal
or polymer and biased to expand when unconstrained. Suitable
materials include nitinol, stainless steel, ELGILOY.TM., polyimide,
PEEK, liquid crystal polymer, polyester, and the like. If made of
nitinol, the distal loop can be heat set to the desired expanded
shape for example by heating to 525.degree. C. for about two
minutes. When deployed in a vessel V, filter 20 has wall apposition
regions 21 at the proximal end of the filter but not along the
vessel wall distal of the proximal end. FIG. 2B shows filter 20 in
cross section, where it is apparent that wall apposition regions
are not present as they are in FIG. 1B. In the case of a braided
structure, flow cannot pass through distal portion of mesh 27
because the pores are generally very small. Most flow is confined
to passing through the central portion 23 of filter 20, and this
central portion 23 of filter 20 is enlarged compared to prior art
filters due to the effect of distal loop 24.
[0043] In FIG. 2, due to the effects of the distal loop, the wall
apposition region of the filter is reduced compared to prior art
filters. However, the radial motion of the elongate support member
25 wire can compromise the necessary wall apposition of the
proximal end of filter.
[0044] FIG. 3 illustrates a windsock-shaped filter 30 attached to
elongate support member 35 via distal sliding element 38. For
clarity, the mesh of the filter is not drawn in the figure. At the
proximal end of the filter, proximal sliding element 36 is slidably
disposed about the elongate support member and attached via tether
36a to point 36b on the filter 30. Stop 32 is provided on the
elongate support member in order to limit the relative motion of
the filter along the support member. Stop 32 may be a wire coil or
a hypotube, polymer or metal, solid, or cut to improve its
flexibility. Support member 35 terminates distally at floppy tip
35b. Distal loop 34 attaches to distal sliding element 38 and
contacts the vessel wall. Distal loop 34 can attach to the proximal
end, distal end, or at any point along distal sliding element 38,
and is configured so as to collapse into a catheter of low profile
by incorporating hinges, zones of preferential bending, and the
like.
[0045] Tether 36a reduces the influence of radial wire motion on
the filter mouth. Tether 36a may be made of any strong
biocompatible flexible strand. Suitable materials include metal,
polymer, monofilament, stranded, or cabled. For example, 0.004 inch
(0.10 mm) diameter nitinol stranded wire made of 7 strands can be
used. More preferably, 0.004 inch (0.10 mm) diameter 49 stranded
nitinol cable can be used. Stranded wire generally has more
flexibility than monofilament wire of the same overall diameter,
and cabled wire generally has more flexibility than stranded wire
of the same overall diameter. Other suitable materials include
KEVLAR.TM. fiber, DACRON.TM. fiber, and other textile fibers.
Stainless steel wires, particularly in stranded or cabled form, may
be preferred in some embodiments due to their high strength.
Further, it is desirable to coat the tethers with thrombosis
reducing materials such as heparin to reduce clot formation on the
tether.
[0046] By positioning elongate support member 35 such that there is
slack in tether 36a, the elongate support member can move laterally
within the filter without compromising filter wall apposition.
Tethers are more effective at accommodating lateral elongate member
motion as compared to the struts commonly used in prior art
designs. It is also expected that proximal sliding element 36 will
slide to relieve tether tension in the event of lateral or radial
elongate member motion, thereby preventing loss of filter
apposition to a vessel wall. Struts, common in prior art designs,
do not afford this degree of freedom for accommodating elongate
member motion. In addition, by locating elongate member 35 within
filter 30, lateral motion of the elongate member will tend to press
filter 30 against the vessel wall because the filter wall is
between the vessel and the elongate member. Further, good wall
apposition of a given filter size is expected over a range of
vessel diameters because there is no stiff hoop at the opening of
filter 30, rather, the filter mesh is gathered at connection 36b.
In contrast, many prior art designs have a stiff hoop at the
proximal end of the filter and such designs have difficulty
accommodating a range of vessel diameters due to the difficulty in
collapsing the stiff hoop while maintaining close contact with the
vessel wall.
[0047] This device can be deployed and used as follows. The
proximal end of elongate member 35 is inserted into the distal end
of catheter C (back loaded into catheter). Elongate member 35 is
withdrawn proximally through catheter C causing stop 32 to contact
slider 36, causing tension to be applied to tether 36a and
resulting in filter 30 being drawn into catheter C due to
attachment of tether 36a to filter 30 at point 36b. Further
proximal motion of the elongate member through catheter C draws the
rest of filter 30, distal loop 34, and optionally floppy tip 35b
into catheter. The catheter with filter assembly therein is
advanced to a region of interest and deployed nearby, generally
distal of the region of treatment in the embodiment shown in FIG.
3. Filter deployment is accomplished by advancing filter 30
distally relative to catheter C. In a preferred embodiment, filter
30 in catheter C is positioned distal to a treatment site, and
catheter C is withdrawn proximally. Filter 30 will remain inside
catheter C due to friction of filter against catheter walls until
distal sliding element 38 contacts stop 32. Catheter C will then
slide relative to filter 30, with reduced friction due to the
tendency of filter 30 to elongate and reduce in diameter due to
action of stop 32 on distal sliding element 38. As catheter C is
withdrawn proximally relative to filter 30, first distal loop 34,
then filter 30 will exit the catheter and expand to contact the
vessel wall. Catheter C can then be withdrawn proximally and
removed from the patient. At this point, treatment and diagnostic
catheters can be introduced over elongate member 35. Excessive
motion of filter 30 against the wall of vessel V during catheter
exchanges is prevented because sliders 36, 38 allow axial and
rotational motion between elongate member 35 and filter 30. During
treatment or diagnosis, emboli may be released from the treated or
diagnosed site and may be collected in the filter.
[0048] Alternatively, filter 30 can be front loaded into catheter C
by introducing floppy tip 35b into the proximal end of catheter C
and pushing elongate member 35 distally. Stop 32 will push against
distal sliding element 38 and cause distal loop 34, filter 30,
tether 36a, and proximal sliding element 36 to enter into catheter
C and advance distally through catheter C. In this alternative,
catheter C can be advanced to a region of interest with the filter
contained within. More preferably, a guidewire can be advanced to a
region of interest, catheter C advanced to the region of interest
over the guidewire, the guidewire withdrawn from catheter C, and
filter 30 front loaded to the region of interest and deployed as
described above.
[0049] To recover the filter, catheter C is advanced over elongate
support member 35 and the elongate support member is withdrawn into
catheter C. Stop 32 will abut proximal slider 36, and slider 36
coupled to tether 36a coupled to filter 30 by way of point 36b will
cause filter 30 to be recovered into catheter C by continued
proximal motion of elongate support member 35 relative to catheter
C. Support member 35 preferably should be withdrawn sufficiently to
at least close the opening of filter 30; alternatively all or part
of filter 30 and distal loop 34 may be withdrawn into catheter C.
It is preferable to draw the distal loop at least partially into
catheter C so as to reduce or eliminate contact of distal loop with
the vessel wall. At this time, the filter/catheter combination can
be withdrawn from the patient.
[0050] FIG. 4 illustrates an alternative embodiment of a filter of
this invention in which windsock-shaped filter 40 is attached to
elongate support member 45 via distal sliding element 48. At the
proximal end of the filter, proximal sliding element 46 is slidably
disposed about the elongate support member and attached via tether
46a to point 46b on the filter. Point 46b can be constructed in a
manner similar to that for sliders 46, 48, or can be a structure
such as a tube into which tether 46a and filter 30 are inserted and
held together by crimping the tube, joining with adhesive, welding,
or the like. Stops 42a and 42b are provided on the elongate support
member in order to limit the relative motion of the filter along
the support member. Stop 42a is shown proximal to the filter
opening and stop 42b is shown within the filter. Alternatively one
stop, such as a wire coil or a hypotube, polymer or metal, solid or
cut to improve its flexibility, can take the place of stops 42a and
42b. Support member 45 terminates distally at floppy tip 45b.
Distal loop 47 is affixed to distal sliding element 48. The distal
loop serves to keep the filter open during movement of the elongate
support member relative to the filter and to prevent the elongate
support member 45 from moving radially and collapsing filter 30.
This is accomplished by keeping the elongate support member, which
slides through the distal sliding element 48, opposed to a vessel
wall. A further advantage of distal loop stabilization of wire
position is that the distal loop does not impede entry of embolic
particles into the filter, unlike prior art approaches where struts
and the like are often placed proximal to the filter. Another
advantage of a distal loop filter is that the mass of the loop and
the comparatively large mass of the proximal filter do not overlap
during collapse of these structures into a delivery catheter, and
as a result the profile of a delivery catheter for the filter can
be made smaller. Filter 40 can comprise metal or polymer braid,
polymer film with holes drilled therethrough, foams, other filter
media as is known in the art, or any of the filter mesh structures
disclosed in the U.S. patent applications filed on the same date as
the present application and entitled "Embolic Filters With
Controlled Pore Size" (Atty Docket: EV31001 US) and "Embolic
Filters Having Multiple Layers and Controlled Pore Size" (Atty
Docket: EV31002US), the contents of each of which are hereby
incorporated by reference herein.
[0051] No Loop Filters
[0052] FIG. 5 illustrates a distal protection system similar to
that shown in FIG. 4, but without the distal loop. Windsock-shaped
filter 50 is attached to elongate support member 55 via distal
sliding element 58. At the proximal end of the filter, proximal
sliding element 56 is slidably disposed about the elongate support
member and attached via tether 56a to point 56b on the filter. Stop
52 is provided on the elongate support member between the distal
and proximal elements. The stop limits the relative motion of the
filter along the support member. Support member 55 terminates
distally at floppy tip 55b which may comprise a coil tip or any of
the embodiments described earlier. Filter 50 is comprised of any of
the filter mesh structures disclosed herein. An advantage of a
filter with no distal loop is that the mass of the filter assembly
is reduced, and as a result the profile of a delivery catheter for
the filter can be smaller. Further, no loop filters have fewer
stiff structures associated with the distal end of the filter.
These attributes allow no loop filters to cross tighter lesions and
to track more easily through tortuous vessels.
[0053] FIG. 6 illustrates a variation of the distal embolic
protection system shown in FIG. 5. Filter 60 is disposed about
elongate support member 65 via distal sliding element 68 and is
comprised of any of the filter mesh structures disclosed herein.
Stop 62 is provided on the support member and tether 66a is
attached to the distal end of the stop (at point 62a) and the
proximal end of the filter (at point 66b), although the tether
could be attached to either end of the stop or at any point
therealong. The stop/tether structure limits the relative motion of
the filter along the support member and provides for radial motion
of the elongate support member. Support member 65 terminates
distally at floppy tip 65b.
[0054] Although we have generally used siding elements to describe
the invention, one or more fixed element could take the place of
the sliding elements.
[0055] While the examples given generally relate to distal embolic
protection filters it is envisioned that the invention can apply to
proximal filters as well.
[0056] While the examples given generally relate to windsock shaped
filters it is envisioned that the invention can apply to filters of
nearly any shape including cups, plates, cylinders, ovoids, and
others. Generally, the invention is best embodied in filters having
an opening facing towards the direction of flow so that emboli have
a tendency to enter the filter.
[0057] The above description and the drawings are provided for the
purpose of describing embodiments of the invention and are not
intended to limit the scope of the invention in any way. It will be
apparent to those skilled in the art that various modifications and
variations can be made without departing from the spirit or scope
of the invention. Thus, it is intended that the present invention
cover the modifications and variations of this invention provided
they come within the scope of the appended claims and their
equivalents.
* * * * *