U.S. patent application number 10/080770 was filed with the patent office on 2002-07-18 for guidewire filter and methods of use.
This patent application is currently assigned to SCIMED LIFE SYSTEMS, INC.. Invention is credited to Chang, Jean, Tsugita, Ross.
Application Number | 20020095174 10/080770 |
Document ID | / |
Family ID | 23747863 |
Filed Date | 2002-07-18 |
United States Patent
Application |
20020095174 |
Kind Code |
A1 |
Tsugita, Ross ; et
al. |
July 18, 2002 |
Guidewire filter and methods of use
Abstract
A filter system for temporary placement of a filter in an artery
or vein. The filter system includes a guidewire that is first
positioned across a lesion within a vessel. The guidewire may
include a distal stop. A slideable filter is then advanced along
the guidewire using an advancing mechanism, typically an elongate
member slideable over the guidewire and contacting the filter. A
capture sheath may be disposed about the filter during advancement.
Once the filter is positioned downstream of the lesion, the capture
sheath is withdrawn, allowing the filter to expand. Further distal
advancement of the filter is prohibited by the stop. After
expansion of the filter, the capture sheath and the advancing
mechanism are withdrawn from the region of interest, and removed
from the patient's vessel. The filter may then be retrieved using a
capture sheath or exchanged for a second filter after removing the
first filter.
Inventors: |
Tsugita, Ross; (Mountain
View, CA) ; Chang, Jean; (Mountain View, CA) |
Correspondence
Address: |
LYON & LYON LLP
633 WEST FIFTH STREET
SUITE 4700
LOS ANGELES
CA
90071
US
|
Assignee: |
SCIMED LIFE SYSTEMS, INC.
One Scimed Plaza
Maple Grove
MN
55311
|
Family ID: |
23747863 |
Appl. No.: |
10/080770 |
Filed: |
February 22, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10080770 |
Feb 22, 2002 |
|
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09560360 |
Apr 28, 2000 |
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6371971 |
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09560360 |
Apr 28, 2000 |
|
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09440204 |
Nov 15, 1999 |
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2002/015 20130101;
A61F 2/0108 20200501; A61F 2230/008 20130101; A61F 2002/018
20130101; A61F 2230/0006 20130101; A61F 2230/0067 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A removable vascular filter system comprising: an elongate wire
having distal and proximal ends; a filter membrane having a distal
portion and a proximal free end portion, wherein said distal
portion is pivotably attached to the elongate wire near said distal
end of the elongate wire and wherein the proximal free end portion
is substantially parallel to the elongate wire in its collapsed
state and wherein said free end portion has a generally scalloped
shape; and deploying means for causing the filter to assume a
position substantially normal to the longitudinal axis of the
elongate wire;
2. The vascular filter system of claim 1, whereby the deploying
means comprises a control mechanism operable from the proximal end
of the elongate wire and operatively connected to the filter
membrane.
3. The vascular filter system of claim 1, wherein the filter
membrane is comprised of a porous mesh, and the scalloped shape is
comprised of rounded sections.
4. The vascular system of claim 3, wherein the pore size of the
porous mesh is about 50-300 microns.
5. The vascular system of claim 3, wherein the pore size of the
porous mesh is about 20-500 microns.
6. A method for protecting a patient during an endoluminal
procedure, comprising the steps of: providing a filter comprising
an elongate wire having distal and proximal ends, and a filter
membrane having a distal portion and a proximal free end portion,
wherein said distal portion is pivotably attached to the elongate
wire near said distal end of the elongate wire and wherein the
proximal free end portion is substantially parallel to the elongate
wire in its collapsed state and wherein said free end portion has a
generally scalloped shape; advancing the filter to a region of
interest within a vessel; expanding the filter membrane within the
region of interest; and performing an endoluminal procedure at the
region of interest, wherein released embolic material is captured
by the filter.
7. The method of claim 6, wherein the filter membrane is expanded
downstream of the region of interest.
8. The method of claim 6, wherein the filter further comprises a
deploying means to hold the filter membrane in a collapsed
condition.
9. The method of claim 8, wherein the deploying means is a
sleeve.
10. The method of claim 9, wherein the step of expanding the filter
further comprises the step of proximally displacing the sleeve from
the filter.
11. The method of claim 6, wherein the vessel is a carotid
artery.
12. The method of claim 6, wherein the vessel is a coronary
artery.
13. The method of claim 6, wherein the step of performing an
endoluminal procedure comprises the step of performing
angioplasty.
14. The method of claim 6, wherein the step of performing an
endoluminal procedure comprises the step of placing a stent within
the region of interest.
Description
[0001] This is a continuation of U.S. application Ser. No.
09/560,360, filed Apr. 28, 2000, which is a continuation of U.S.
application Ser. No. 09/440,204, filed Nov. 15, 1999, both of which
are expressly incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION FIELD OF THE INVENTION
[0002] The present invention relates generally to devices and
methods for providing temporary placement of a filter in a blood
vessel. More particularly, the invention provides a filter
cartridge system for entrapment of embolic material in an artery or
vein during an endovascular procedure. The system permits the
replacement of the filter cartridge without requiring the removal
of the guidewire during the endovascular procedure.
BACKGROUND OF THE INVENTION
[0003] Treatment of thrombotic or atherosclerotic lesions in blood
vessels using an endovascular approach has recently proven to be an
effective and reliable alternative to surgical intervention in
selected patients. For example, directional atherectomy and
percutaneous translumenal coronary angioplasty (PTCA) with or
without stent deployment are useful in treating patients with
coronary occlusion. Atherectomy physically removes plaque by
cutting, pulverizing, or shaving in atherosclerotic arteries using
a catheter-deliverable endarterectomy device. Angioplasty enlarges
the diameter of a stenotic vessel by exerting mechanical force on
the vascular walls. In addition to using angioplasty, stenting,
and/or atherectomy on the coronary vasculature, these endovascular
techniques have also proven useful in treating other vascular
lesions in, for example, carotid artery stenosis, peripheral
arterial occlusive disease (especially the aorta, the iliac artery,
and the femoral artery), renal artery stenosis caused by
atherosclerosis or fibromuscular disease, superior vena cava
syndrome, and occlusive iliac vein thrombosis resistant to
thrombolysis.
[0004] It is well recognized that one of the complications
associated with endovascular techniques is the dislodgment of
embolic materials generated during manipulation of the vessel,
thereby causing occlusion of the narrower vessels downstream and
ischemia or infarct of the organ that the vessel supplies. In 1995,
Waksman et al. disclosed that distal embolization is common after
directional atherectomy in coronary arteries and saphenous vein
grafts. See Waksman et al., American Heart Journal 129(3):430-5
(1995), (this and all other references cited herein are expressly
incorporated by reference as if fully set forth in their entirety
herein). This study found that distal embolization occurs in 28%
(31 out of 111) of the patients undergoing atherectomy. In January
1999, Jordan, Jr. et al. disclosed that treatment of carotid
stenosis using percutaneous angioplasty with stenting is associated
with more than eight times the rate of microemboli seen using
carotid endarterectomy. See Jordan, Jr. et al. Cardiovascular
Surgery 7(1):33-8 (1999), incorporated herein by reference.
Microemboli, as detected by transcranial Doppler monitoring in this
study, have been shown to be a potential cause of stroke. The
embolic materials include calcium, intimal debris, atheromatous
plaque, thrombi, and/or air.
[0005] There are a number of devices designed to provide blood
filtering for entrapment of vascular emboli. The vast majority of
these devices are designed for permanent placement in veins to
prevent pulmonary embolism. A temporary venous filter device is
disclosed in Bajaj, U.S. Pat. No. 5,053,008, incorporated herein by
reference. The Bajaj device is an intracardiac catheter for
temporary placement in the pulmonary trunk of a patient predisposed
to pulmonary embolism due to, e.g., hip surgery, major trauma,
major abdominal or pelvic surgery, or immobilization. The Bajaj
device includes an umbrella made from meshwork that traps venous
emboli before they reach the lungs. This device is designed for
venous filtration and is not suitable for arterial use because of
the hemodynamic differences between arteries and veins.
[0006] There are very few intravascular devices designed for
arterial use. Arteries are much more flexible and elastic than
veins and, in the arteries, blood flow is pulsatile with large
pressure variations between systolic and diastolic flow. These
pressure variations cause the artery walls to expand and contract.
Blood flow rates in the arteries vary from about 0.1 to 5 L/min.
Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial filtering
system, which includes a catheter with a strainer device at its
distal end. This device is inserted into the vessel downstream from
the treatment site and, after treatment, the strainer is collapsed
around the entrapped emboli and removed from the body. The Ginsburg
device, however, is integral with the catheter, unlike the devices
described later herein. Ing. Walter Hengst GmbH & Co, German
Patent DE 34 17 738, discloses another arterial filter having a
folding linkage system that converts the filter from the collapsed
to the expanded state.
[0007] Filters mounted to the distal end of guidewires have been
proposed for intravascular blood filtration. A majority of these
devices include a filter that is attached to a guidewire and is
mechanically actuated via struts or a pre-shaped basket that
deploys in the vessel. These filters are typically mesh
"parachutes" that are attached to the shaft of the wire at the
distal end and to wire struts that extend outward in a radial
direction at their proximal end. The radial struts open the
proximal end of the filter to the wall of the vessel. Blood flowing
through the vessel is forced through the mesh thereby capturing
embolic material in the filter.
[0008] Gilson et al., International Publication No. WO 99/23976
describes a guidewire with a filter slideably mounted thereon.
Although the filter is not fixed to the guidewire at a single
point, the filter is limited in its range of movement by two stops
at the distal end of the guidewire, the stops being relatively
closely spaced. Thus, unlike the present invention, in Gilson et
al. the filter cannot be removed unless the entire guidewire is
removed.
[0009] The useful in vivo time of a guidewire filter will vary,
depending upon the type of procedure, the patient, and the blood
flow. These factors may contribute to relatively short use time
because of, for example, blood coagulation or excessive emboli
clogging the filter mesh. Because for existing devices, the
guidewire and the filter are integrated into one inseparable
device, changing the filter after its useful in vivo deployment
time has been completed requires the removal and replacement of the
guidewire. This change requires time consuming and costly
fluoroscopic guidance to reposition the new guidewire and
filter.
[0010] There is a need in the art for a device that will not
require removal and replacement of the guidewire should the in vivo
useful life of a blood filter be exceeded. The present invention
addresses that need by providing a blood cartridge filter that may
be used and replaced without requiring the removal of the
guidewire.
SUMMARY OF THE INVENTION
[0011] The present invention provides devices and methods for
directing a blood filter into position using a guidewire wherein
the blood filter may be deployed and replaced independently of the
guidewire. More specifically, a guidewire cartridge filter system
is disclosed for capturing embolic material generated during a
surgical procedure within a region of interest in an artery or
vein.
[0012] In accordance with the present invention, the cartridge
filter system comprises an elongate member that acts as an
advancing mechanism, e.g., a push wire or sheath, having a distal
region attached to a filter, e.g., a parachute, basket, or scroll
filter. In certain embodiments, the filter may be releasably
attached to the elongate member through an interlock, which may
comprise, for example, a mechanical interlock or electromechanical
interlock. The filter may comprise an expansion frame and a filter
material, typically a filter mesh, attached to the expansion frame.
The cartridge filter system includes means for engaging the
guidewire, such as a wire guide that slideably engages a guidewire.
The wire guide may be attached to either or both of the elongate
member and the filter. In certain embodiments, the wire guide
comprises a ring having an aperture adapted to receive the
guidewire. In certain other embodiments, the wire guide comprises a
body portion of the elongate member having a longitudinally
extending groove adapted to slideably engage the guidewire. The
body portion may thus have a C-shaped cross section. Because the
wire guide slideably engages the guidewire, the filter may be
directed into place by the guidewire, but deployed and retracted
independently of the guidewire. The filter can be placed in a
collapsed condition to facilitate entry into a vessel and an
expanded condition to capture embolic material in the vessel. As
used herein, "advancing mechanism" denotes any elongate member or
structure suitable for advancing the filter into position within a
vessel while engaging the guidewire through the wire guide. The
elongate member could thus be either a wire or a catheter wherein
the lumen of the catheter serves as the wire guide. In one
embodiment, the elongate member comprises a sheath wherein the
lumen of the sheath serves as the wire guide.
[0013] Filters suitable for use within the filter system of the
present invention are described, for example, in U.S. Pat. No.
5,910,154, incorporated herein by reference in its entirety. In one
embodiment, the filter is biased to automatically open radially
within a blood vessel. In such filters, the expansion frame may
comprise a plurality of struts or arms attached to and extending
distally from a distal end of the elongate member. The struts are
connected to each other at each end and have an intermediate region
that is biased to expand radially. Filter mesh is attached
typically between the intermediate region such as the midpoint and
the distal ends of the struts, thereby defining a substantially
hemispherical or conical shaped filter assembly. In embodiments of
the invention wherein the elongate member comprises a sheath, a
filter biased to automatically open radially may be releasably
carried in its collapsed condition within the sheath wherein a
mechanical interlock between elongate member and the filter is
formed by the friction between the filter and the lumenal wall of
the sheath.
[0014] Other filters suitable for the present invention are not
biased to automatically open radially within a blood vessel. In
such filters, the elongate member may comprise a sheath containing
an inner wire, and the expansion frame includes a plurality of
struts attached to the distal end of the sheath. The struts extend
distally from the sheath and attach to the distal end of the inner
wire that is exposed distally beyond the sheath. At an intermediate
region, the struts are notched or otherwise biased to fold out
radially. Filter mesh is attached to the struts between the
intermediate region and the distal end of the inner wire. With the
sheath fixed, the inner wire is proximally displaced, compressing
the struts and causing them to bend or buckle at the intermediate
region and move radially outwardly, expanding the filter mesh
across the blood vessel. As used herein, "inner wire" means any
structure suitable to be slideably disposed within the sheath and
stiff enough to compress the struts as the inner wire is proximally
displaced with respect to the sheath. The inner wire may thus
comprise an inner sheath within which the guidewire is slideably
disposed.
[0015] In certain other embodiments, the filter may comprise a
fluid operated filter wherein the expansion frame includes a
balloon that inflates to expand the filter into an enlarged
condition for use. The construction and use of expansion frames and
associated filter mesh have been thoroughly discussed in earlier
applications including Barbut et al., U.S. application Ser. No.
08/533,137, filed Nov. 7, 1995, Barbut et al., U.S. application
Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S.
application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al.,
U.S. Pat. No. 5,769,816, Barbut et al., U.S. application Ser. No.
08/645,762, filed May 14, 1996, and Barbut et al., U.S. Pat. No.
5,662,671, and the contents of each of these prior applications are
expressly incorporated herein by reference.
[0016] The methods of the present invention include prevention of
distal embolization during an endovascular procedure to remove
emboli and/or foreign bodies such as gas bubbles from blood
vessels. The vessels include the coronary artery, aorta, common
carotid artery, external and internal carotid arteries,
brachiocephalic trunk, middle cerebral artery, basilar artery,
subclavian artery, brachial artery, axillary artery, iliac artery,
renal artery, femoral artery, popliteal artery, celiac artery,
superior mesenteric artery, inferior mesenteric artery, anterior
tibial artery, posterior tibial artery, and all other arteries
carrying oxygenated blood. Suitable venous vessels include the
superior vena cava, inferior vena cava, external and internal
jugular veins, brachiocephalic vein, pulmonary artery, subclavian
vein, brachial vein, axillary vein, iliac vein, renal vein, femoral
vein, profunda femoris vein, great saphenous vein, portal vein,
splenic vein, hepatic vein, and azygous vein.
[0017] In a method of using the cartridge filter system, the distal
end of the guidewire is inserted through an artery or vein and
advanced into or beyond a region of interest, typically a stenotic
lesion caused by buildup of atherosclerotic plaque and/or thrombi.
The guidewire may be inserted percutaneously, laparoscopically, or
through an open surgical incision. In a collapsed condition, the
filter and the elongate member are advanced over the guidewire,
having the wire guide of the filter cartridge system engaging the
guidewire. In one embodiment, the wire guide engages the elongate
member at a single discrete location in a monorail fashion such as
through a ring structure. If the wire guide includes a body portion
of the elongate member having a longitudinally extending groove
adapted to slideably engage the guidewire, the body portion engages
the guidewire in an over-the-wire fashion wherein the guidewire is
slideably disposed within the groove of the body portion.
Alternatively, the elongate member may comprise a sheath wherein
the guidewire is slideably disposed within the lumen of the sheath
in an over-the-wire fashion such that the lumen serves as the wire
guide. Regardless of whether the wire guide engages the guidewire
in a monorail or an over-the-wire fashion, the filter is then
expanded downstream of the vascular occlusion. If the wire guide
engages the guidewire in an over-the-wire fashion, the elongate
member may be left in the vessel during the in vivo deployment time
of the filter because the elongate member and the guidewire are
then integrated into a single unit, limiting the interference with
further deployment of therapy devices in the vessel. If, however,
the wire guide engages the guidewire in a monorail fashion, the
elongate member is preferably removed from the filter during the in
vivo deployment time of the filter to prevent a clinician from
having to contend with the independent movement of both the
guidewire and the elongate member during the surgical procedure.
Preferably, in such embodiments, the elongate member releasably
attaches to the filter through a mechanical interlock. After
deploying the filter, the mechanical interlock is released to allow
the removal of the elongate member.
[0018] Should the in vivo deployment time of the filter be
exceeded, the used filter is retracted from the body and the
guidewire. If the filter and elongate member were separated by
releasing an interlock, the wire guide on the elongate member must
be engaged with the guidewire so that the elongate member may be
displaced distally on the guidewire towards the used filter. The
interlock would then be re-engaged to connect the elongate member
and the used filter together whereupon the elongate member may be
retracted to remove the used filter. If the elongate member and the
used filter were permanently attached, the elongate member may
simply be retracted to remove the used filter. An additional filter
and elongate member may then be advanced over the guidewire as
described herein. Because the present invention allows the removal
and replacement of filters without requiring the removal of the
guidewire, the filter system may be denoted a "cartridge filter"
system in that the filter is akin to, for example, a printer
cartridge, readily replaceable within the printer. After the
stenotic lesion is removed or otherwise treated and an adequate
lumenal diameter is established, the filter is collapsed and
removed, together with the captured embolic debris, from the vessel
by withdrawing another elongate member used for retrieval.
Alternatively, the filter could be removed by withdrawing the
guidewire to remove the entire filter system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1A depicts an embodiment of an elongate member having a
filter in a collapsed condition according to the present
invention.
[0020] FIG. 1B depicts the elongate member of FIG. 1A having the
filter in an expanded condition.
[0021] FIG. 1C depicts a cross-sectional view through section line
C-C of the elongate member depicted in FIG. 1B.
[0022] FIG. 1D depicts the elongate member of FIG. 1C having a
guidewire received through the wire guide.
[0023] FIG. 2A depicts an embodiment of a distal end of the
guidewire.
[0024] FIG. 2B depicts an alternative embodiment of the distal end
of the guidewire.
[0025] FIG. 2C depicts another alternative embodiment of the distal
end of the guidewire.
[0026] FIG. 3A depicts another embodiment of the filter shaped as a
parachute.
[0027] FIG. 3B depicts another embodiment of the filter shaped as
an eggbeater.
[0028] FIG. 4A depicts a guidewire inserted across a vascular
occlusion.
[0029] FIG. 4B depicts a monorail cartridge filter system being
deployed across a vascular occlusion.
[0030] FIG. 4C depicts a monorail cartridge filter system wherein
the mechanical interlock connecting the elongate member and the
filter has been released.
[0031] FIG. 4D depicts an over-the-wire cartridge filter system
deployed across a vascular occlusion.
[0032] FIG. 5A depicts a cartridge filter system wherein the system
operate as either an over-the-wire or a monorail system
[0033] FIG. 5B depicts a cross-sectional view through section line
B-B of the elongate member depicted in FIG. 5A.
[0034] FIG. 6 depicts a cartridge filter system wherein the
elongate member comprises an inner sleeve and wherein the system
further includes a capture sheath.
[0035] FIG. 7A depicts a guidewire with a distal stop positioned
across a vascular lesion.
[0036] FIG. 7B depicts a slideable filter, an advancing mechanism,
and a capture sheath disposed over the guidewire of FIG. 7A.
[0037] FIG. 7C depicts the capture sheath crossing the lesion with
a filter expanded downstream.
[0038] FIG. 7D depicts the guidewire and slideable filter after
removal of the capture sheath and advancing mechanism.
[0039] FIG. 8 depicts an advancing mechanism connected to a
slideable filter through a flush contact.
[0040] FIG. 9A depicts an advancing mechanism connected to a
slideable filter through pivoting claws.
[0041] FIG. 9B depicts the opening of the pivoting claws of FIG.
9A.
[0042] FIG. 10A depicts an advancing mechanism connected to a
slideable filter through a threaded interlock.
[0043] FIG. 10B depicts the opening of the threaded interlock of
FIG. 10A.
[0044] FIG. 11A depicts the slideable filter connected to an
advancing mechanism through a mechanical interlock.
[0045] FIG. 11B depicts the assembly of FIG. 11A after removal of a
capture sheath.
[0046] FIG. 11C depicts the assembly of FIG. 11B after rotation of
the mechanical interlock.
[0047] FIG. 11D depicts the assembly of FIG. 11C after removal of
the sheath and advancing mechanism.
[0048] FIG. 12A depicts an actuatable stop comprising off-center
tubes disposed along a guidewire.
[0049] FIG. 12B depicts a distal view of the stop of FIG. 12A.
[0050] FIG. 12C depicts insertion of a slideable filter and the
stop of FIG. 12A into a vessel.
[0051] FIG. 12D depicts the slideable filter and stop of FIG. 12C
after removal of the capture sleeve.
[0052] FIG. 12E depicts the slideable filter and stop of FIG. 12C
before advancement of the alignment sheath.
[0053] FIG. 13A depicts another embodiment of an actuatable stop
having a slideable filter bearing proximally against the stop.
[0054] FIG. 13B depicts a capture sheath disposed about and
aligning the actuatable stop and filter of FIG. 13A.
[0055] FIG. 13C depicts the filter withdrawn proximally over the
actuatable stop of FIG. 13B.
[0056] FIG. 14A depicts another embodiment of an actuatable stop
comprising a slip stop.
[0057] FIG. 14B depicts a capture sheath disposed about and
aligning the actuatable stop and filter of FIG. 14A.
[0058] FIG. 15A depicts a guidewire having a single distal
stop.
[0059] FIG. 15B depicts a guidewire having proximal and distal
stops, wherein the stops are pivoting barbs.
[0060] FIG. 15C depicts a guidewire having a distal stop and two
proximal stops, wherein the proximal stops comprise pivoting
cleats.
[0061] FIG. 15D depicts a capture sheath disposed about and
aligning the cleats with a filter.
[0062] FIG. 15E depicts another embodiment of a capture sheath
disposed about and aligning the cleats with a filter.
[0063] FIG. 16A depicts an open carriage filter structure.
[0064] FIG. 16B depicts a continuous carriage filter structure.
DETAILED DESCRIPTION
[0065] In a first embodiment, a cartridge filter system for
temporary placement in a vessel, either an artery or vein, is
provided as depicted in FIGS. 1A, 1B, 1C, and 1D. The filter system
includes an elongate member 10 having a proximal end, distal region
11, and expandable filter 20 mounted at the distal region. The
filter 20 comprises expansion frame 22 and mesh 25 that is welded,
adhesive bonded, or otherwise disposed about struts 28 of the
expansion frame. Alternatively, the filter comprises a membrane
extending from a proximal end to a distal end and having an
expandable intermediate region. the proximal end includes segments
that extend to the intermediate region and that have gaps or
windows in between to allow blood to flow inside the structure. the
distal end is a continuous membrane having holes drilled therein to
create a filter membrane. Anticoagulants, such as heparin and
heparinoids, may be applied to the mesh 25 to reduce thrombi
formation. The filter 20 can be collapsed as shown in FIG. 1A to
facilitate insertion into a vessel, and thereafter expanded as
shown in FIG. 1B. Wire guide 26, which is adapted to slideably
engage a guidewire 30, may be included in distal region 11 of the
elongate member 10. Alternatively, the wire guide 26 may be
integral with the filter or with both the filter and the elongate
member. In certain embodiments, the wire guide 26 may comprise a
ring-shaped structure. A cross-sectional view of the elongate
member 10 through section line C-C is depicted in FIG. 1C. The
design and construction of a variety of expandable filters suitable
for use within the filter cartridge system of the present invention
is described in detail in Tsugita et al., U.S. Pat. No.
5,910,154.
[0066] The filter may be biased to automatically open radially
within a blood vessel. In such filters, the struts of the expansion
frame may be connected to each other at each end and have an
intermediate region that is biased to expand radially as
illustrated in FIGS. 1A and 1B. Other filters suitable for the
present invention are not biased to automatically open radially
within a blood vessel. One embodiment of such a filter, as
illustrated in FIG. 6, the struts 28 are notched or otherwise
biased to fold out radially. At a distal end of the filter, the
struts attach to an inner wire 55 whereas the proximal end of the
struts attach to an outer sheath 55. Proximal displacement of the
inner wire 55 with respect to the outer sheath 55 causes the struts
to fold out radially, thereby expanding the filter mesh 25 across a
blood vessel lumen. Alternatively, the filter may be fluid operated
as discussed previously.
[0067] It is to be noted that if the blood filter is biased to
automatically open radially within a blood vessel, a restraint is
needed to collapse the filter before it is inserted into a vessel
lumen. In one embodiment, a sleeve 5 acts as the restraint to
collapse the filter 20 as illustrated in FIG. 1A. To release the
restraint, the sleeve 5 may be retracted from the filter 20 by
proximally displacing a wire 6 as illustrated in FIG. 1B.
[0068] To deploy the cartridge filter system of the present
invention, the wire guide 26 engages the guidewire 30 having a
proximal end and distal end 33. The guidewire 30 is slideably
received by elongate member 10 through wire guide 26 as depicted,
for example, in FIG. 1D. Different constructions of the distal end
33 of the guidewire 30 are depicted in FIGS. 2A, 2B, and 2C. Distal
end 33 may assume a substantially linear configuration relative to
the proximal end of the guidewire as depicted in FIG. 2A.
Alternatively, distal end 33 may assume an angular configuration
relative to the proximal end of the guidewire as depicted in FIG.
2A. Distal end 33 may be shaped like a fishhook as depicted in FIG.
2C. The distal region of the guidewire may be constructed of a
flexible material to facilitate entry through a region of interest,
and preferably is equipped with an atraumatic tip as is known in
the art. The embodiments in FIGS. 2B and 2C, having a curvilinear
design, are particularly useful in achieving access to a complex
lesion in a tortuous vessel.
[0069] FIGS. 3A and 3B depict alternative embodiments of expandable
filter 20 mounted on the distal region of elongate member 10. In
FIG. 3A, the filter 20 comprises an expansion frame 22 that is
parachute-shaped and mesh 25 that is welded or adhesive bonded to
struts 28 of the expansion frame 22. Wire guide 26 is included in
the distal region of the elongate member and projects distally from
filter 20 for engaging a guidewire. In FIG. 3B, filter 20 comprises
an expansion frame 22 that assumes the shape of an eggbeater in its
expanded state and wherein struts 28 are compressible.
[0070] By way of example, when the cartridge filter system as
disclosed herein is intended for use in the aorta, the area of the
mesh 25 required for the device is calculated from Bernoulli's
equation as described in our earlier applications including Barbut
et al., U.S. Pat. No. 5,662,671, Barbut et al., U.S. application
Ser. No. 08/553,137, filed Nov. 7, 1995, Barbut et al., U.S.
application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et
al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996,
Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr. 30,
1996, and Barbut et al., and U.S. application Ser. No. 08/645,762,
filed May 14, 1996.
[0071] The guidewire and slideable filter disclosed herein may be
used in the carotid arteries, the coronary arteries, the aorta, and
in where temporary filtration is desired. In an embodiment of the
cartridge filter system that is to be used in the aorta, the filter
material is a mesh 25 with dimensions within the following ranges
is desirable: mesh area is 0.004-5 in.sup.2, more preferably
0.007-4 in.sup.2, more preferably 0.010-3 in.sup.2, more preferably
0.015-2 in .sup.2, more preferably 0.020-1 in.sup.2, more
preferably 0.025-0.076 in.sup.2; mesh thickness is 60-280 .mu.m,
more preferably 70-270 .mu.m, more preferably 80-260 .mu.m, more
preferably 90-250 .mu.m, more preferably 100-250 .mu.m, more
preferably 120-230 .mu.m, more preferably 140-210 .mu.m; thread
diameter is 30-145 .mu.m, more preferably 40-135 .mu.m, more
preferably 50-125 .mu.m, more preferably 60-115 .mu.m, more
preferably 70-105 .mu.m, and pore size is 500 .mu.m or less, more
preferably 400 .mu.m or less, more preferably 300 .mu.m or less,
more preferably 200 .mu.m or less, more preferably 100 .mu.m or
less, more preferably 50 .mu.m or less and usually larger than at
least a red blood cell. In a preferred embodiment of the invention,
mesh area is 2-8 in.sup.2, mesh thickness is 60-200 .mu.m, thread
diameter is 30-100 .mu.m, and pore size is 50-300 .mu.m. In a
further preferred embodiment of the invention, mesh area is 3-5
in.sup.2, mesh thickness is 60-150 .mu.m, thread diameter is 50-80
.mu.m, and pore size is 100-250 .mu.m.
[0072] In other embodiments, the filter material comprises a thin
film laser cut with holes to allow blood flow (not illustrated).
Typical dimensions include pore size of 20-500 .mu.m, a thickness
of 0.0005-0.003 inches, and area approximately same as for meshes
described above.
[0073] Once appropriate physical characteristics are determined,
suitable mesh 25 can be found among standard meshes known in the
art. For example, polyester meshes may be used, such as meshes made
by Saati Corporations and Tetko Inc. These are available in sheet
form and can be easily cut and formed into a desired shape. In a
preferred embodiment, the mesh is welded (e.g., sonic or laser) or
sewn into a cone shape. Other meshes known in the art, which have
the desired physical characteristics, are also suitable.
Anticoagulants, such as heparin and heparinoids, may be applied to
the mesh to reduce the chances of blood clotting on the mesh.
Anticoagulants other than heparinoids also may be used, e.g.,
ReoPro (Centocor). The anticoagulant may be painted or sprayed onto
the mesh. A chemical dip comprising the anticoagulant also may be
used. Other methods known in the art for applying chemicals to mesh
may be used.
[0074] The length of the guidewire 30 and the elongate member 10
will generally be between 30 and 300 centimeters, preferably
approximately between 50 and 195 centimeters. The filter will be
capable of expanding to an outer diameter of at least 0.2
centimeters, more preferably at least 0.5 centimeters, more
preferably at least 1.0 centimeters, more preferably at least 1.5
centimeters, more preferably at least 2.0 centimeters, more
preferably at least 2.5 centimeters, more preferably at least 3.0
centimeters, more preferably at least 3.5 centimeters, more
preferably at least 4.0 centimeters, more preferably at least 4.5
centimeters, more preferably at least 5.0 centimeters. These ranges
cover suitable diameters for both pediatric and adult use. The
foregoing ranges are set forth solely for the purpose of
illustrating typical device dimensions. The actual dimensions of a
device constructed according to the principles of the present
invention may obviously vary outside of the listed ranges without
departing from those basic principles.
[0075] In use, as depicted in FIG. 4A, guidewire 30 may be inserted
percutaneously through a peripheral artery or vein and advanced
typically in the direction of blood flow. However, guidewire 30 may
be inserted and advanced in a direction opposite the blood flow,
e.g., retrograde through the descending aorta to reach the coronary
artery. Distal end 33 of the guidewire 30 is passed through
occluding lesion 100, typically an atheromatous plaque, and
positioned distal to the occlusion. Elongate member 10 of FIG. 1A
is inserted over the proximal end of guidewire 30 through wire
guide 26, and advanced distally until filter 20 is positioned
distal to plaque 100 as depicted in FIG. 4B. By having wire guide
26 engage the guidewire 30, the filter 20 and the elongate member
10 can be easily steered intravascularly to reach the region of
interest. Filter 20 is expanded to capture embolic material, such
as calcium, thrombi, plaque, and/or tissue debris. The useful in
vivo life of filter 20 depends greatly on the type of medical
procedure being performed, the condition of the patient (such as
whether the patient is receiving an anticoagulant), and volume of
blood flow. Although current filters can be deployed for relatively
long periods (upwards of 60 minutes), it is possible that current
filters will have shorter useful in vivo deployment times for the
reasons noted above. Should the useful in vivo life of filter 20 be
exceeded, filter 20 must be replaced by an unused filter. Unlike
prior art systems in which the filter was integrated with the
guidewire, in the present invention, filter 20 and elongate member
10 may be retracted from the body and guidewire 30 without
requiring the removal of guidewire 30. An unused filter 20 and
elongate member 10 may then be inserted over the proximal end of
guidewire 30 through a wire guide 26, and advanced distally until
filter 20 is positioned distal to plaque 100 similarly as depicted
in FIG. 4B.
[0076] As illustrated in FIG. 4B, the wire guide 26 may engage the
guidewire 30 at a single discrete location. Suitable wire guides 26
that engage the guidewire at a discrete location may comprise, for
example, a ring or similar structure. Such embodiments of the
cartridge filter system may be denoted "partially-threaded" or
monorail systems because, proximal to the wire guide 26, the
guidewire 30 and the elongate member 10 are separate and
independent from one another. Other medical devices having monorail
construction are known in the art. Note that proximal to the wire
guide, a clinician must contend with two separate and independent
structures within the vessel lumen. This can make the insertion of
additional therapy devices into the vessel lumen difficult. For
example, a therapy device, such as an angioplasty balloon, will
typically engage the guidewire to assist positioning the therapy
device in the vessel. As the therapy device is displaced along the
guidewire, it may cause the elongate member to injure the vessel
lumen.
[0077] To prevent such injury, the filter and elongate member may
be releasably attached through an interlock in a monorail
embodiment of the invention. As illustrated in FIG. 4C, the
interlock may comprise a mechanical interlock having a threaded
portion 9 at the distal end of the elongate member 10 adapted to
engage a threaded portion 8 attached to the filter 20. After the
filter 20 has been expanded to cover the vessel lumen, the elongate
member 10 is rotated to release the mechanical interlock by
unthreading the threaded portions 8 and 9. Note that the filter 20
is then retained only by the guidewire 30. To assist the retention
of the filter 20 along the guidewire, the guidewire may have a stop
60 to prevent further distal displacement of the filter. In such an
embodiment, the filter is free, however, to displace proximally.
The pressure from the blood flow and the tension provided by the
expansion of the filter against the walls of the vessel lumen will
tend to prevent proximal displacement. Although such forces will
tend to prevent proximal displacement, it may be beneficial during
some procedures to allow a small amount of proximal displacement
when necessary.
[0078] As used herein, "elongate member" denotes any structure
suitable for advancing filter 20 into position within a vessel
while engaging guidewire 30 through a wire guide 26. Thus elongate
member 10 may comprise, of course, a wire. Alternatively, elongate
member 10 may comprise a catheter such as a balloon catheter
suitable for angioplasty. If elongate member 10 comprises a
catheter, the lumen of the catheter may serve as the wire guide 26.
In such an embodiment, elongate member 10 slideably engages
guidewire 30 in an "over-the-wire" manner similar to, for example,
the manner in which a single lumen catheter is threaded over a
guidewire in neuroradiological procedures. Turning now to FIG. 4D,
an over-the-wire cartridge filter system is illustrated. Elongate
member 10 comprises a catheter or sleeve 35 wherein the lumen 40 of
the catheter 35 serves as the wire guide 26. The expansion frame 22
of filter 20 attaches to the catheter 35 along the catheter wall
portion 42. Unlike the monorail system illustrated in FIG. 4B, a
clinician threading additional devices into the blood vessel in
which an over-the-wire cartridge filter system is deployed will not
have to contend with two independent structures within the blood
vessel lumen. Inspection of the monorail cartridge filter system
illustrated in FIG. 4B reveals that proximal to the filter 20, the
guidewire 30 and elongate member 10 are independent of one another,
potentially hampering the deployment of additional devices within
the blood vessel. Nevertheless, monorail or partially-threaded
systems possess advantages over an over-the-wire system (that may
be denoted as "fully-threaded"). For example, in angioplasty
procedures or the like, the guidewire 30 must be relatively long to
extend from vessels within a patient's leg to the heart. If the
proximal portion of the guidewire 30 that extends outside the
patient's body is relatively short, there comes a point at which,
as the elongate member 10 is retracted from the body, the elongate
member 10 will entirely cover this external proximal portion of the
guidewire 30 (in an over-the-wire cartridge filter system). The
clinician would then no longer be able to maintain the position of
the guidewire 30. Thus, as is known in other medical procedures,
over-the-wire medical devices require relatively long proximal
transfer portions external to a patient's body, causing
inconvenience during catheterization procedures.
[0079] The present invention includes over-the-wire filter
cartridge system embodiments that do not require the relatively
long proximal transfer portions of prior art over-the-wire systems.
For example, in FIG. 5A and 5B, an embodiment of such a filter
cartridge system is illustrated. Elongate member 10 may include a
ring-shaped wire guide 26 that attaches to the expansion frame 22
of filter 20 (filter 20 only partly illustrated). Elongate member
10 also includes a body portion 46 having a longitudinally
extending groove 45 adapted to slideably engage wire guide 30. In
one embodiment, groove 45 is shaped such that body portion 46 has a
C-shaped cross section as illustrated in FIG. 5B. The elongate
member 10 is constructed of a suitably flexible material such that
a clinician may force guidewire 30 into the groove 46 by forcing
apart arms 47 and 48 of the "C" formed by groove 46. The guidewire
30 would then be held within groove 46 by arms 47 and 48. Outside
the body, the elongate member 10 and the guidewire 30 may be kept
separate, eliminating the need for a long proximal transfer portion
outside the patient's body. Within a vessel, however, the system of
FIGS. 5A and 5B will operate as an over-the-wire system. As the
filter 20 and elongate member 10 are retracted from the guidewire
30 and the patient's body, the guidewire 30 may be separated from
the elongate member 10 by pulling apart the already separated
portions of elongate member 10 and guidewire 30. The resulting
tension flexes arms 47 and 48 outwardly, allowing the guidewire 30
to be removed from the groove 45.
[0080] Although the groove 45 slideably engages the guidewire 30,
it is to be noted that (particularly when body portion 46 has a
C-shaped cross section) the guidewire 30 may not be entirely
circumferentially surrounded by elongate member 10 as is the case
in ordinary over-the-wire systems (such as illustrated in FIG. 4c).
To provide full circumferential support around guidewire 30,
elongate member 10 may have one or more spiral portions 47 wherein
the elongate member spirals about guidewire 30 such that spiral
portion 47 resembles coils of a spring. Note that should the
elongate member 10 include the spiral portions 47, as the filter 20
and elongate member 10 are retracted from the guidewire 30, the
clinician will unravel the spring portion 47 to separate it from
the guidewire 30. Conversely, as the elongate member 10 is being
advanced along guidewire 30, the clinician must ravel spiral
portion 47 about the guidewire 30 to continue deployment of a
filter.
[0081] Regardless of whether the cartridge system is an
over-the-wire or a monorail system, one of ordinary skill in the
art will appreciate that there are a number of ways to actuate the
filter of the present invention. For example, if the filter is
biased to automatically open radially within a blood vessel, the
cartridge filter system may be contained within a catheter or
sheath 5 as illustrated in FIG. 1A. As the elongate member and
filter are advanced beyond the sheath 5, the filter will
automatically expand radially within the vessel because of the
pre-existing bias within the filter as illustrated in FIG. 1B.
Alternatively, the filter may be fluid operated wherein the filter
contains a balloon that expands to expand the filter. In addition,
the filter may be mechanically actuated by the clinician.
[0082] Turning now to FIG. 6, a mechanically actuated cartridge
filter system is illustrated. In such filters, the elongate member
10 may comprise a sheath or catheter 50 containing an inner wire 55
wherein the expansion frame 22 includes a plurality of struts 28
attached to the distal end of the sheath 50. The struts 28 extend
distally from the sheath 50 and attach to the distal end of the
inner wire 55 that is distally exposed beyond the sheath. At an
intermediate region, the struts 28 are notched or otherwise biased
to fold out radially. Filter mesh 25 is attached to the struts 28
between the intermediate region and the distal end of the inner
sheath 55. To open the filter 20, the sheath 50 is fixed in
position, and the inner wire 55 is proximally displaced,
compressing the struts 28 and causing them to bend or buckle at the
intermediate region and move radially outwardly, expanding the
filter mesh 25 across the blood vessel. It is to be noted that the
guidewire 30 may have a stop 60 formed to assist the positioning
and deployment of the filter 20 along the guidewire 30.
[0083] As used herein, "inner wire" means any structure suitable to
be slideably disposed within the sheath 50 and stiff enough to
compress the struts 28 as the inner wire 55 is proximally displaced
with respect to the sheath 50. Thus, as illustrated in FIG. 6, the
inner wire 55 may comprise an inner sheath 55 that slideably
contains the guidewire 30 within a lumen of the inner sheath. Note
that the inner sheath 55 and the sheath 50 may each possess a body
portion having a longitudinally extending slit therein (not
illustrated). Within both the inner sheath 55 and the sheath 50,
the combination of the slit and the lumen would therefore comprise
the longitudinally extending groove already described. Therefore,
the cartridge filter system illustrated in FIG. 6 could be advanced
within a blood vessel in an over-the-wire fashion yet not require a
relatively long proximal transfer portion as described with respect
to the embodiment of the cartridge filter system illustrated in
FIGS. 5A and 5B.
[0084] Another method for deploying a slideable filter along a
guidewire is shown in FIGS. 7A-7D. According to this method,
guidewire 30 is first positioned across lesion 100 within vessel
101. Guidewire 30 may include a distal stop 102. Filter 110, having
proximal end 111 and distal end 112, is then advanced along
guidewire 30. This step of advancement is typically performed with
capture sheath 105 disposed about filter 110. Advancement may also
be accomplished using an advancing mechanism 120 having distal end
121 that bears against proximal end 111 of filter 110.
Alternatively, the static friction between filter 110 and sheath
105 may be adequate to advance the filter along guidewire 30, in
which case sheath 105 is the advancing mechanism. Once filter 110
is positioned downstream of lesion 100, capture sheath 105 is
withdrawn, allowing the filter to expand as depicted in FIG. 7C.
Further distal advancement of filter 110 is prohibited by
frictional engagement of filter 110 by the vessel lumen or by stop
102 when present. Alternatively, filter 110 may be equipped with an
actuatable locking mechanism that engages guidewire 30 when the
filter is properly positioned. After expansion of filter 110,
capture sheath 105 and advancing mechanism 120 are withdrawn from
the region of interest as shown in FIG. 7D, and removed from the
patient's vessel.
[0085] In certain embodiments, the advancing mechanism bears
against proximal end 111 of filter 110, but is not otherwise
connected. In other embodiments as shown in FIG. 8, advancing
mechanism 125, having distal end 126, is coupled through flush
contact interlock 127 to proximal end 111 of filter 110. In this
case, the interlock is activated by magnetic or electromagnetic
force and is releasable. FIGS. 9A and 9B show an alternative
mechanical interlock. In FIG. 9A, pivoting claws 130 are mounted at
the distal end of advancing mechanism 125. The distal end of each
claw 130 is adapted to engage recess 131 disposed circumferentially
about proximal end 111 of filter 110. Claws 130 are maintained in
contact with recess 131 by the action of locking sheath 133 that
bears circumferentially against claws 130. When capture sheath 105
and locking sheath 133 are withdrawn as depicted in FIG. 9B, claws
130 pivot out of engagement, thereby releasing filter 110.
[0086] Another mechanical interlock is shown in FIGS. 10A and 10B.
FIG. 10A shows a threaded interlock between threaded screw 136
mounted on proximal end 111 of filter 110. The screw engages
coupling 135 having a threaded portion adapted to receive screw
136. FIG. 10B depicts disengagement of coupling 135 from screw 136
to permit removal of advancing mechanism 125 and capture sheath 105
from the patient's vessel. In order to disengage the coupling from
the screw it may be necessary to have a rotational lock on the
filter, so that the coupling can be rotated while the filter
remains fixed.
[0087] A further mechanical interlock is shown in FIGS. 11A-11D.
FIG. 11A shows first hook 140 mounted at the distal end of
advancing mechanism 125. Second hook 141 is mounted at proximal end
111 of filter 110, and is adapted to engage first hook 140.
Engagement of hooks 140 and 141 is dependent upon proper rotational
alignment of the hooks. This alignment is maintained so long as
sheath 105 surrounds the interlock. FIG. 11B shows the interlock
after placement within a vessel and removal of sheath 105. As
depicted in FIG. 11C rotation of hook 140 disengages the interlock.
Advancing mechanism 125 and sheath 105 are then removed from the
region of interest and from the patient's vessel as shown in FIG.
11D. In addition to the detachable interlock mechanisms discussed
above, a number of additional mechanisms have been disclosed in
U.S. Pat. Nos. 5,312,415, 5,108,407, 5,891,130, 5,250,071,
5,925,059, 5,800,455, 5,800,543, 5,725,546, 5,350,397, 5,690,671,
5,944,733, 5,814,062, and 5,669,905, all of which are expressly
incorporated herein by reference in their entirety. It will
understood that any of the interlocks disclosed in any of these
patents may be used in the present invention.
[0088] As noted above, one or more distal and/or proximal stops may
be placed along the guidewire. These stops may be pre-mounted,
installed during a procedure, or integral with the filter and
simultaneously inserted therewith. An actuatable stop is shown in
FIGS. 12A-12E. Referring to FIG. 12A, the proximal stop is
comprised of off-centered tubes, shown here as first tube 145,
second tube 146, and biasing element 147 connecting the first and
second tubes. When misaligned as shown in FIG. 12A, first and
second tubes 145 and 146, respectively, pinch and frictionally
engage guidewire 30 as shown in FIG. 12B. In use, this slideable
stop can be employed proximal of the filter as shown in FIG. 12C.
Sheath 105 contains advancing mechanism 125, an actuatable stop
including first and second tubes 145 and 146 coupled through
biasing element 147, and filter 110. Sheath 105 forces first and
second tubes 145 and 146 into near coaxial alignment, thereby
permitting the stop to slide over guidewire 30. This assembly is
advanced across lesion 100 until the filter reaches optional distal
stop 102. The filter and proximal stop are then released from
sheath 105 as depicted in FIG. 12D, the stop engaging the
guidewire. Sheath 105 and advancing mechanism 125 are then removed
from the patient's vessel. After performance of an endoluminal
procedure (e.g., angioplasty, stent deployment, angiography,
atherectomy), the filter and stop are retrieved by sheath 150 as
depicted in FIG. 12E. Sheath 150 first captures first and second
tubes of the stop and forces them into alignment against the action
of biasing element 147. In this manner, the stop is de-actuated and
again slides over guidewire 30. Sheath 150 then captures filter 110
that bears against optional stop 102 during advancement of sheath
150 over filter 110. The entire assembly, including sheath 150,
filter 110, and the proximal stop, are then removed from the
patient's vessel.
[0089] In another embodiment, a pivoting proximal stop is used as
shown in FIGS. 13A-13C. Referring to FIG. 13A, the proximal stop is
comprised of tapered proximal section 156 and flat distal section
155, the tapered proximal section allowing a filter to pass
distally when advanced over the stop. Proximal section 156 has
lumen 157 adapted to receive guidewire 30. Section 155 lies in a
plane substantially perpendicular to the axis of lumen 157. In this
manner, the proximal stop pivots and frictionally engages guidewire
30 when proximal end 111 of filter 110 bears against section 155.
Filter 110 is retrieved and withdrawn over the stop as shown in
FIG. 13B. Sheath 105, optionally a stepped sheath as depicted in
FIG. 15B, aligns the stop with the opening at the proximal end 111
of filter 110, permitting the filter to pass proximally over the
stop as shown in FIG. 13C.
[0090] In another embodiment, a slip stop is used as the proximal
stop as depicted in FIGS. 14A and 14B. Slip stop 160 comprises a
tubular segment having open distal end 162 and tapered proximal end
161. Guidewire 30 passes smoothly through proximal end 161 when
distal end 162 is centered about guidewire 30. However, when stop
160 becomes misaligned, as shown in FIG. 14A, proximal end 161
pinches and frictionally engages guidewire 30, preventing proximal
advancement of filter 110. To retrieve filter 110, sheath 105,
optionally a stepped sheath as shown, is advanced distally over
stop 160 and filter 110, thereby aligning slip stop 160 with the
opening at proximal end 111 of filter 110, as shown in FIG.
14B.
[0091] FIG. 15A shows a guidewire having one distal stop 102. FIG.
15B shows a guidewire having distal stop 102 and proximal stop 165.
Proximal stop 165 may be mounted on a pivot about its mid-point,
thereby allowing a filter to pass proximal to distal, and later be
retrieved distal to proximal, provided sufficient force is applied
to pivot the stop. FIG. 15C shows two proximal stops 166 and 167,
each comprising a plurality of pivoting cleats 168 attached to
housing 169 that engages guidewire 30. It will understood that any
number of proximal and distal stops may be employed, including 1,
2, 3, 4, 5, 6, 7, or any other desired number depending on the
procedure. FIG. 15D shows retrieval of filter 110. Sheath 105
restrains cleats 168 to allow passage of proximal end 111 of filter
110 over the cleats. In certain embodiments, it may desirable for
sheath 105 to include a sharp step, shown as numeral 170 in FIG.
15E. This sheath will maintain closure of cleats 168 until the
cleats are guided within proximal end 111 of filter 110, permitting
removal of the filter over the cleats.
[0092] The sliding filter as disclosed herein may be constructed
with an open carriage as shown in FIG. 16A or a continuous carriage
as shown in FIG. 16B. Referring to FIG. 16A, a plurality of struts
181 join proximal end 111 to distal end 112. Filter 110 is disposed
about a portion of struts 181, either over or under the struts.
Struts 181 buckle radially outward when proximal end 111 and distal
end 112 are forced together. In certain embodiments, distal end 112
will include a tapered edge as shown in FIG. 16A. FIG. 16B depicts
a continuous carriage extending from proximal end 111 to distal end
112, and terminating in a tapered distal edge. Sliding ring 180 may
be incorporated distal or proximal. Struts 181 are connected at a
first end to carriage 182 and at a second end to sliding ring 180.
Struts 181 buckle radially outward when sliding ring 180 and
carriage 182 are forced together.
[0093] Although the foregoing invention has, for the purposes of
clarity and understanding, been described in some detail by way of
illustration and example, it will be obvious that certain changes
and modifications may be practiced that will still fall within the
scope of the appended claims. Moreover, it will be understood that
each and every feature described for any given embodiment or in any
reference incorporated herein, can be combined with any of the
other embodiments described herein.
* * * * *