U.S. patent application number 12/336572 was filed with the patent office on 2009-04-16 for embolic protection device.
This patent application is currently assigned to Salviac Limited. Invention is credited to Eamon Brady, Paul GILSON, Padraig Maher, Charles Taylor, David Vale.
Application Number | 20090099593 12/336572 |
Document ID | / |
Family ID | 26320116 |
Filed Date | 2009-04-16 |
United States Patent
Application |
20090099593 |
Kind Code |
A1 |
GILSON; Paul ; et
al. |
April 16, 2009 |
EMBOLIC PROTECTION DEVICE
Abstract
An embolic protection device has a collapsible filter element
(105) mounted on a carrier such as a guidewire (101). The filter
element (105) collapses into the outer end of a catheter (118) for
deployment and retrieval through a vascular system of a patient.
The filter element (105) has a collapsible filter body with a
proximal inlet end and a distal outlet end. The proximal inlet end
has inlet openings sized to allow blood and embolic material enter
the filter body. The outlet end has outlet openings which allow
through passage of blood but retain embolic material within the
filter body. After use, the catheter (118) is movable along the
guidewire (101) to engage the proximal end of the filter element
and close the inlet openings before sliding over the filter element
from the proximal end to the distal end to progressively collapse
the filter body on the guidewire (101) for retrieval. The filter
element (105) may conveniently be mounted on a tubular sleeve (104)
which is slidable and rotatable on the guidewire (101) between
spaced-apart stops (106, 120) on the guidewire (101) which allows
some manipulation of the guidewire independently of the filter when
the filter is in use.
Inventors: |
GILSON; Paul; (Uggool,
IE) ; Brady; Eamon; (Elphin, IE) ; Maher;
Padraig; (Gloster, IE) ; Vale; David;
(Clontarf, IE) ; Taylor; Charles; (Warninglid,
GB) |
Correspondence
Address: |
Sughrue Mion-ABBOTT LABS
2100 Pennsylvania Avenue, N.W.
Washington
DC
20037
US
|
Assignee: |
Salviac Limited
Dublin
IE
|
Family ID: |
26320116 |
Appl. No.: |
12/336572 |
Filed: |
December 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11610144 |
Dec 13, 2006 |
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12336572 |
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11325480 |
Jan 5, 2006 |
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11610144 |
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10442259 |
May 21, 2003 |
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11325480 |
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10058828 |
Jan 30, 2002 |
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10442259 |
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09921596 |
Aug 6, 2001 |
6432122 |
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10058828 |
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09188472 |
Nov 9, 1998 |
6336934 |
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09921596 |
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2230/0093 20130101;
A61F 2/01 20130101; A61F 2/013 20130101; A61F 2230/0067 20130101;
A61F 2230/0006 20130101; A61F 2002/018 20130101; A61F 2002/016
20130101; A61F 2230/0097 20130101; A61F 2230/0069 20130101; A61B
2017/22051 20130101; A61F 2002/015 20130101; A61F 2/011 20200501;
A61B 2017/22067 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61F 2/01 20060101
A61F002/01 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 1997 |
IE |
97 0789 |
Apr 8, 1998 |
IE |
98 0267 |
Claims
1. A method for providing embolic protection, comprising: advancing
a support element through a vascular system of a patient, wherein a
filter element is associated with the support element, the filter
element being movable between a collapsed stored position for
movement through the vascular system and an expanded position for
occluding a blood vessel such that blood passing through the blood
vessel is delivered through the filter element but embolic material
is retained in the filter element, the filter element comprising a
mesh member defined by a plurality of slots, the slots configured
to allow the mesh member to move between the stored collapsed
position and the expanded position; and engaging the filter element
with at least a portion of a wall of the blood vessel.
2. The method of claim 1, further comprising removing a sheath from
about a portion of the filter element, thereby allowing the filter
element to move from the collapsed stored position to the expanded
position.
3. The method of claim 1, further comprising using at least a
proximal section of the filter element as a platform for a balloon
catheter or a stent.
4. The method of claim 3, wherein an outside diameter dimension of
the proximal section is sized to allow free movement of the balloon
catheter or stent over the proximal section.
5. The method of claim 4, wherein the outside dimension of the
proximal section is 0.35 inches or less.
6. The method of claim 5, wherein the outside dimension of the
proximal section is 0.18 inches or less.
7. The method of claim 6, wherein the outside dimension of the
proximal section is 0.14 inches or less.
Description
[0001] This application is a divisional of pending U.S. application
Ser. No. 11/610,144 filed Dec. 13, 2006, which is a continuation of
application Ser. No. 11/325,480 filed Jan. 5, 2006, which is a
continuation of application Ser. No. 10/442,259 filed May 21, 2003,
which is a continuation of application Ser. No. 10/058,828 filed
Jan. 30, 2002, which is a continuation of application Ser. No.
09/921,596 filed Aug. 6, 2001, now U.S. Pat. No. 6,432,122, which
is a continuation of application Ser. No. 09/188,472 filed Nov. 9,
1998, now U.S. Pat. No. 6,336,934, all of which claim priority from
Irish Patent Application No. 97/0789 filed Nov. 7, 1997, and Irish
Patent Application No. 98/0267 filed Apr. 8, 1998. The entire
disclosures of the prior applications, are considered part of the
disclosure of the accompanying continuation application and are
hereby incorporated by reference.
INTRODUCTION
[0002] The invention relates to an embolic protection device.
[0003] The term "STROKE" is used to describe a medical event
whereby blood supply to the brain or specific areas of the brain is
restricted or blocked to the extent that the supply is inadequate
to provide the required flow of oxygenated blood to maintain
function. The brain will be impaired either temporarily or
permanently, with the patient experiencing a loss of function such
as sight, speech or control of limbs. There are two distinct types
of stroke, hemorrhagic and embolic. This invention addresses
embolic stroke.
[0004] Medical literature describes carotid artery disease as a
significant source of embolic material. Typically, an
atherosclerotic plaque builds up in the carotid arteries. The
nature of the plaque varies considerably, but in a significant
number of cases pieces of the plaque can break away and flow
distally and block blood flow to specific areas of the brain and
cause neurological impairment. Treatment of the disease is
classically by way of surgical carotid endarterectomy whereby, the
carotid artery is cut and the plaque is physically removed from the
vessel. The procedure has broad acceptance with neurological
complication rates quoted as being low, somewhere in the order of
5% although claims vary widely on this.
[0005] Not all patients are candidates for surgery. A number of
reasons may exist such that the patients could not tolerate
surgical intervention. In these cases and an increasing number of
candidates that are surgical candidates are being treated using
transcatheter techniques. In this case, the evolving approach uses
devices inserted in the femoral artery and manipulated to the site
of the stenosis. A balloon angioplasty catheter is inflated to open
the artery and an intravascular stent is sometimes deployed at the
site of the stenosis. The action of these devices as with surgery
can dislodge embolic material which will flow with the arterial
blood and if large enough, eventually block a blood vessel and
cause a stroke.
[0006] It is known to permanently implant a filter in human
vasculature to catch embolic material. It is also known to use a
removable filter for this purpose. Such removable filters typically
comprise umbrella type filters comprising a filter membrane
supported on a collapsible frame on a guidewire for movement of the
filter membrane between a collapsed position against the guidewire
and a laterally extending position occluding a vessel. Examples of
such filters are shown in U.S. Pat. No. 4,723,549, U.S. Pat. No.
5,053,008, U.S. Pat. No. 5,108,419 and WO 98/33443. Various
deployment and/or collapsing arrangements are provided for the
umbrella filter. However, as the filter collapses, the captured
embolic material tends to be squeezed outwardly towards an open end
of the filter and pieces of embolic material may escape from the
filter with potentially catastrophic results. More usually, the
filter umbrella is collapsed against the guidewire before removal
through a catheter or the like. Again, as the filter membrane is
collapsed, it will tend to squeeze out the embolic material.
Further, the umbrella filter is generally fixed to the guidewire
and any inadvertent movement of the guidewire during an
interventional procedure can dislodge the filter.
[0007] The present invention is directed towards overcoming these
problems.
[0008] There is a need for an embolic protection device which will
overcome this problem.
STATEMENTS OF INVENTION
[0009] According to the invention, there is provided an embolic
protection device comprising: [0010] a collapsible filter element
mounted on a filter carrier for delivery through a vascular system
of a patient, [0011] the filter element being movable between a
collapsed stored position against the filter carrier for movement
through the vascular system, and an expanded position for occluding
a blood vessel such that blood passing through the blood vessel is
delivered through the filter element, [0012] the filter element
comprising a collapsible filter body having an inlet end and an
outlet end, [0013] the inlet end of the filter body having one or
more inlet openings sized to allow blood and embolic material enter
the filter body, [0014] the outlet end of the filter body having a
plurality of outlet openings sized to allow through passage of
blood but to retain undesired embolic material within the filter
body, [0015] means for closing the inlet openings at the inlet end
of the filter body, and [0016] means for collapsing the filter body
on the support.
[0017] Advantageously, the inlet openings in the filter are closed
before the fitter is collapsed ensuring retention of all embolic
material within the filter element.
[0018] In a particularly preferred embodiment of the invention, the
means for closing the inlet comprises: [0019] a tubular filter
retrieval device having an open distal end for reception of the
filter element, [0020] said distal end being engagable with a
proximal inlet end of the filter body to close the inlet openings
and being slidable over the filter body from the inlet end to the
outlet end to progressively collapse the filter body on the filter
carrier and receive the filter body within the retrieval
device.
[0021] Conveniently, the retrieval device which may be a catheter
or pod or the like which engages and collapses the filter element
firstly closing the inlet openings to prevent any escape of embolic
material and then collapsing the remainder of the filter being slid
from the proximal end over the filter to the distal end of the
filter.
[0022] In a particularly preferred embodiment, the collapsible
filter element is slidably mounted on the filter carrier between
the a pair of spaced-apart stops on the filter carrier for axial
movement of the filter element along the filter carrier between the
stops.
[0023] Advantageously, the filter carrier which may for example be
a guidewire can be moved independently of the filter element and
thus accidental movement of the guidewire is accommodated without
unintentionally moving the filter, for example, during exchange of
medical devices.
[0024] In a further embodiment, the filter element is rotatably
mounted on the filter carrier.
[0025] In a preferred embodiment, a sleeve is slidably mounted on
the filter carrier between the stops, the length of the sleeve
being less than the distance between the stops, the filter element
being mounted on the sleeve.
[0026] In a particularly preferred embodiment, the filter element
comprises:-- [0027] a collapsible filter net mounted on the filter
carrier, [0028] the filter net being movable between a collapsed
stored position against the filter carrier and an expanded position
extending outwardly of the filter carrier for deployment across a
blood vessel.
[0029] Preferably, the tubular filter retrieval device comprising a
catheter slidable along the filter carrier, an open distal end of
the catheter forming a housing for reception of the filter
element.
[0030] In another embodiment, a proximal inlet end of the filter
body is fixed to the filter carrier and a distal end of the filter
body is slidably mounted on the filter carrier, although this
arrangement may be reversed.
[0031] In a further embodiment, the distal end of the filter body
is attached to a collar which is slidable along the filter
carrier.
[0032] In a preferred embodiment, a filter support frame is mounted
on the filter carrier, the support frame being movable between a
collapsed position along the filter carrier and an extended
outwardly projecting position to support the filter body in the
expanded position.
[0033] In another embodiment, the filter support frame is fixed on
the filter carrier at a proximal end of the filter body.
[0034] Preferably, the filter support frame slidably engages the
filter carrier at a distal end of the filter body. Ideally, the
filter support frame is biased into a normally extended
position.
[0035] In a further embodiment, a circumferential groove is
provided in the filter body intermediate the ends of the filter
body.
[0036] In another embodiment, a guide olive is provided on the
filter carrier distally of the filter body, the guide olive having
a cylindrical body with a tapered distal end, the cylindrical body
being engagable within a distal end of a deployment catheter, said
tapered distal end projecting outwardly of the deployment catheter
to provide a smooth transition between the catheter and the filter
carrier.
[0037] In a further embodiment, the net is gathered into the filter
carrier at each end of the net.
[0038] In another embodiment of the invention, there is provided an
embolic protection device comprising a filter element for placing
in a desired position, the filter element providing a pathway for
blood and having means for capturing, retaining and removing
undesired embolic material.
[0039] In one embodiment of the invention, the pathway has means
for constricting flow to capture undesired embolic material.
[0040] In another embodiment of the invention, the filter has a
proximal end and a distal end openings in the proximal end being
larger than openings in the distal end, the proximal end openings
being sized to allow the flow of blood and embolic material to
enter the filter element and the distal end openings being sized to
allow the flow of blood while capturing undesired emboli within the
filter element.
[0041] In a further embodiment of the invention, the filter element
includes storage means to store captured undesired embolic material
in the filter element. Preferably, the storage means comprises
additional storage pathways within the filter element. Preferably,
the filter element defines a three dimensional matrix.
[0042] In another embodiment of the invention, the filter element
is of a polymeric porous structure. In a further embodiment of the
invention, the matrix comprises a porous structure dimensioned to
entrap embolic material which typically ranges in size from about
100 microns to 3500 microns. In a still further embodiment of the
invention, the filter element is compressible and/or foldable for
loading into a delivery device to deliver the filter element to a
desired location in the compressed or folded state.
[0043] In one embodiment of the invention, the filter element has
material removed from its structure to aid compressibility.
[0044] In another embodiment of the invention, the filter element
has material removed from its structure to provide specific sizing
in relation to the size of embolic material to be trapped.
[0045] In a further embodiment of the invention, the filter element
has pathways through the filter body that are inter-linked such
that the flow rate through the filter may be tailored.
[0046] In another embodiment of the invention, the filter element
has a distal end which is tapered such that there is a smooth
transition in lateral stiffness to improve the maneuverability of
the filter element in the vascular system.
[0047] In a further embodiment of the invention, the filter element
has a soft distal portion to aid in atraumatic transport through
the vascular system. Preferably, the filter element has
circumferential grooves to reduce the lateral flexibility of the
filter element.
[0048] In one embodiment of the invention, the filter element has a
tapered proximal end to facilitate retrieval by a removal
catheter.
[0049] In another embodiment of the invention, the filter element
has inlet holes that close on pulling back into a retrieval
catheter to ensure retention of any collected emboli.
[0050] In a further embodiment of the invention, the filter element
has outlet openings sized to capture embolic material of a size
large enough to impair the function of the organ receiving the
blood downstream of the filter body element. Preferably, the filter
element is sized to capture embolic material of a size greater than
100 microns. Most preferably, the filter element is sized to
capture embolic material of a size greater than 200 microns. Most
preferably, the filter element is sized to capture embolic material
of a size greater than 500 microns.
[0051] In one embodiment of the invention, the filter element is
sized for complete coverage of a vessel cross-section that allows
passage of blood and blood components.
[0052] In a still further embodiment of the invention, there is
provided a device having means for placing over a medical
guidewire.
[0053] In another embodiment of the invention, there is provided a
device which may be placed under a balloon or stent delivery
catheter.
[0054] In a further embodiment of the invention, there is provided
a device having means for insertion through, femoral, brachial,
radial, subclavian or other arterial puncture by means of a
transcatheter approach.
[0055] In one embodiment of the invention, there is provided a
device for protection of neurological function which is inserted
for the duration of a surgical intervention at or near the site of
surgical opening.
[0056] It is envisaged that two devices could to used bi-laterally
in left and right cartoid arteries allowing sufficient cerebral
blood flow to maintain neurological function during procedures with
a high risk of generating clot such as electrophysiological
treatment of coronary arrhythmias.
[0057] In a further embodiment of the invention, there is provided
a device including a delivery catheter in which an external sheath
is engagable with the filter element or filter carrier to provide
push during delivery and is removable to allow maximum space in the
vascular cross-section during an interventional procedure.
[0058] In one embodiment of the invention, the external sheath is
joined to the filter element or filter carrier by a joining means.
The joining means may be a removable shrink tube or a removable
clip. Preferably the joining means is a compression connector such
as a Tuohy Borst adapter.
[0059] In another embodiment of the invention, the delivery
catheter has a central lumen for at least part of its length to
allow it to track over a steerable guidewire.
[0060] In a further embodiment of the invention, the external
sheath is sufficiently long to extend to the outside of the
vasculature and is movable proximally to release the filter element
from the catheter.
[0061] In one embodiment of the invention, the delivery catheter
has an external covering which extends beyond the push element to
define a filter retention sleeve.
[0062] In another embodiment of the invention, the delivery
catheter has a spring component with a localised stepwise
increasing pitch to alter stiffness characteristics to suit the
target vasculature.
[0063] In a further embodiment of the invention, the delivery
catheter has a strong component with a localised gradually
increasing pitch to alter stiffness characteristics to suit the
target vasculature.
[0064] In one embodiment of the invention, the filter element is
mounted on a collapsible support structure which is movable between
a collapsed position for deployment and an extended in-use
position, means being provided for retaining the support structure
in the collapsed position. Preferably, the support structure
comprises support arms. Preferably, the support arms are formed
from a shape memory or elastic memory material. Most preferably,
the support arms are formed from Nitinol.
[0065] In one embodiment of the invention, the support arms are
configured to open co-axially with the filter carrier such that
they may be restrained for removal by pulling the filter element
proximally into an appropriately dimensioned sheath.
[0066] In another embodiment of the invention, the filter element
has an associated support structure with a pre-shaped spiral
arrangement such that it provides radial support to the filter
element.
[0067] In a further embodiment of the invention, the filter support
structure is adapted to fold into the collapsed position when
pulled into a retrieval catheter.
[0068] In one embodiment of the invention, the filter element
comprises a flexible shaped polymeric component.
[0069] In another embodiment of the invention, the shaped polymeric
component is constructed such that fluid flow through the component
assists in opening the component from the collapsed position.
[0070] In a further embodiment of the invention, the shaped
polymeric component is flexible and opens to make circumferential
contact with the vessel wall by way of using the pressure drop
across the exit filter face.
[0071] In a further embodiment of the invention, the filter element
is mounted on a guidewire such that the guidewire has freedom to
rotate and/or move axially independently of the filter. More
preferably the wire has complete freedom to rotate independently of
the filter and has limited axial movement. The limit of axial
movement is determined by stops mounted on or connected to the
wire. Ideally the wire can move 100 mm in the axial direction
independent of the filter. More ideally the wire can move less than
50 mm independently of the filter. This embodiment facilitates the
maintenance of filter position during the exchange of catheters and
permits the steering of the wire independent of the filter.
[0072] In a further embodiment of this invention the filter element
is bonded to the filter mount at its proximal end and its distal
end is free to move relative to the filter mount and proximal bond
so as to aid the collapse of the filter for deployment.
[0073] In a further embodiment of the invention the filter element
is tapered over part or all of its length such that it is
accurately sized to the vessel over some portion of its length.
[0074] In a further embodiment of the invention the shaped
polymeric component contains one or more circumferential grooves
along its body to maintain the circular shape of the filter element
in an under sized artery.
[0075] In one embodiment of the invention, the filter element is
directly bonded onto a steerable medical guide wire incorporating a
slidable sheath that is movable to deploy the filter.
[0076] In another embodiment of the invention, there is provided a
device incorporating a medical guidewire with a flexible segment of
wire distal to the filter so as to provide steerability of the wire
particularly prior to it being deployed.
[0077] In a further embodiment of the invention, there is provided
a device incorporating a medical guide wire with a soft distal
segment so as to provide a tip section that will be atraumatic.
[0078] In a still further embodiment of the invention, there is
provided a device with a porous coating on a distal end of the
filter element only with a means for opening and closing the filter
by slidable motion.
[0079] In one embodiment of the invention, the filter element
incorporates proximal tapering such that it may be pulled
proximally into a sheath for removal in order that such pulling
action will effectively reduce the diameter of the filter and
assist retrieval.
[0080] In another embodiment of the invention, the filter element
has a porous structure that can be deployed and closed by way of a
slidable motion, the closure thereof caused by way of snap-fit to a
protruding rim that allows the support elements be pulled
proximally, thus closing the structure with the filter membrane
attached.
[0081] In a further embodiment of the invention, there is provided
a device having a filter element which permits the incorporation of
a medical guide wire in the outer wall of the filter element to
facilitate the incorporation of large inlet holes on the proximal
inlet end of the filter element.
[0082] In one embodiment of the invention, the filter element
comprises a mesh work structure with large proximal inlet holes and
small distal outlet holes wherein the mesh structure is collapsible
into a small diameter delivery catheter and is expandable upon
deployment to a shape which is remembered by the mesh structure
either through shape memory characteristics or elastic memory
characteristics.
[0083] In another embodiment of the invention, the filter element
comprises a mesh work structure wherein the expansion of the filter
element within the vessel causes blood flowing through the vessel
to flow through the filter element due to the filter element
engaging with the wall of the vessel to conform to the shape of the
vessel bore.
[0084] In another embodiment, the filter element comprises a
braided fibrous mesh work. Preferably, distal outlet openings are
defined by an area enclosed by a series of crossing interwoven
fibres. Larger proximal inlet holes are provided by the convergence
of the fibres of the braid into a few bundles which are mounted to
the filter carrier. Preferably, the fibrous meshwork material is an
elastic or shape memory material such that it can be collapsed into
a delivery catheter and recover its enlarged shape upon deployment.
The fibres of the meshwork are bonded at the points where they
cross one another. The fibres may be made from either a polymer or
metal or a composite material.
[0085] In a further embodiment, the distal end of the filter
element has the facility to move in the axial direction relative to
the proximal end of the filter element so as to take up the exact
shape of the blood vessel.
[0086] In a further embodiment, the device has a porous coating on
a distal end of the filter element only with means for opening and
closing the filter element by slidable motion. Preferably, the
filter element comprises a collapsible wire frame having a
plurality of wires, outer ends of the wires being hingedly mounted
on the filter carrier, the wires being hinged intermediate their
ends, at one end the wires being fixed on the filter carrier and at
the other end the wires being mounted on a collar which is slidable
along the filter carrier, a porous filter mesh being mounted on the
wire frame. An actuating sleeve is slidable over the filter carrier
to push the collar towards the fixed end of the filter element, and
a collapsing device is engagable with the collar to pull back the
collar away from the fixed end of the filter element to collapse
the wire frame against the filter carrier for retrieval of the
filter element.
[0087] In a still further embodiment of the invention, there is
provided a filter retrieval system for use with the device
comprising a longitudinal catheter with a radically deformable or
elastic tip to assist the pull back of the filter into the tip.
[0088] In another embodiment of the invention, there is provided a
system incorporating a filter, a delivery catheter and a retrieval
catheter for temporary filtration of the vascular system during an
interventional procedure.
[0089] In another aspect the invention provides an embolic
protection device comprising: [0090] a collapsible filter element
mounted on a filter carrier for delivery through a vascular system
of a patient. [0091] the filter element being movable between a
collapsed stored position against the filter carrier for movement
through the vascular system, and an expanded position for occluding
a blood vessel such that blood passing through the blood vessel is
delivered through the filter element, a pair of spaced-apart stops
on the filter carrier, the collapsible filter element being
slidably mounted on the filter carrier for axial movement along the
filter carrier between the stops, and means for collapsing the
filter element on the filter carrier.
BRIEF DESCRIPTION OF THE DRAWINGS
[0092] The invention will be more clearly understood from the
following description thereof given by way of example only with
reference to the accompanying drawings in which:--
[0093] FIG. 1 is a side view of an embolic protection device
according to the invention in use;
[0094] FIG. 2 is a side view of the device of FIG. 1 in a
pre-loaded position for insertion;
[0095] FIG. 3A is a side view illustrating one method of fixing the
device to catheter;
[0096] FIG. 3B is a side view of an embolic protection device
incorporating the fixing of FIG. 3A;
[0097] FIG. 4 is a side view illustrating another method of
fixing;
[0098] FIG. 5 is an end view of a split collar used in the fixing
of FIG. 4;
[0099] FIG. 6 is a side view illustrating a further method of
fixing;
[0100] FIG. 7 is an end view of a jubilee clip used in the fixing
of FIG. 6;
[0101] FIG. 8 is a side view of one filter element used in the
device of the invention;
[0102] FIG. 9 is a side view of another filter element;
[0103] FIG. 10 is a side view of the filter element of FIG. 8 being
removed;
[0104] FIG. 11 is an isometric view of another filter element in an
in-use placed configuration;
[0105] FIG. 12 is a side view of the filter element of FIG. 11 in a
retracted position for insertion and withdrawal;
[0106] FIGS. 13 to 15 are side views of another filter element in
different positions;
[0107] FIGS. 16 and 17 are side views of part of a further filter
element with a snap fit retrieval arrangement;
[0108] FIG. 18 is a perspective, partially cross-sectional view of
another embolic protection device shown mounted in a vessel;
[0109] FIGS. 19a to 19c are perspective views illustrating the
formation of a collapsible filter support for use in the device of
FIG. 18;
[0110] FIGS. 20 to 22 are perspective views of other filter
elements;
[0111] FIG. 23 is an elevational view of another filter
element;
[0112] FIG. 24 is a sectional view taken along the line XXIV-XXIV
of FIG. 23;
[0113] FIG. 25 is a sectional view taken along the line XXV-XXV of
FIG. 23;
[0114] FIG. 26 is an enlarged detail view of portion of the
filter,
[0115] FIG. 27 is an expanded view of the filter element of FIG.
23;
[0116] FIG. 28 is a side view illustrating one method in which the
substrate tubing that the filter element is attached to can run
over the primary crossing guidewire;
[0117] FIG. 29 is a side view illustrating the position in which
the "olive" component will sit in order to provide a smooth
transition between the primary crossing guidewire and the loading
pod;
[0118] FIG. 30 is a perspective view of the filter element in its
most distal position;
[0119] FIG. 31 is a perspective view of the filter element in its
most proximal position;
[0120] FIG. 32 is a perspective view of the filter element when the
distal end of the filter is not bonded to the substrate tubing;
[0121] FIG. 33 is a side view of a concertina shaped filter; A
being when the filter is deployed and B when the filter is in its
loaded shape;
[0122] FIG. 34 is a perspective view of the floating distal tip
design with a spring element incorporated distal to the floating
tip;
[0123] FIG. 35 is a side view of another floating distal tip design
with a spring incorporated into the distal tip;
[0124] FIG. 36 is a side view of the floating distal tip design
with the shape memory alloy extending from the proximal end to the
distal end;
[0125] FIG. 37 is a perspective view of the mesh design
incorporating a floating distal tip;
[0126] FIG. 38 illustrates perspective views of filter
geometries;
[0127] FIG. 39 shows a fibrous mesh filter design with fibres woven
at the distal end and converging into a number of bundles at the
proximal end;
[0128] FIG. 40 is partially sectioned elevational view an embolic
protection device according to the invention;
[0129] FIG. 41 is a schematic sectional elevational view of the
embolic protection device of FIG. 40; and
[0130] FIG. 42 is a detail sectional view of portion of the device
of FIG. 40.
DETAILED DESCRIPTION
[0131] Referring to the drawings there are illustrated various
embolic protection devices according to the invention. The devices,
in general, comprise a filter element for temporary placing in a
desired position during a surgical or interventional procedure
typically using a guidewire and catheter. The filter element
provides a pathway for blood and has means for capturing and
retaining undesired embolic material released during the surgical
procedure. The filter element containing the retained embolic
material is removed when the interventional procedure is completed.
In this way the patient is protected against the risk of stroke or
other complications caused by the release of undesired embolic
material during the procedure.
[0132] In one embodiment of the device it will be used in an over
the wire transcatheter configuration. The clinician will cross the
lesion with a steerable guidewire. The cerebral protection device
will then be threaded over the guidewire and will be placed distal
to the site of the lesion being treated. By means of actuation, or
other means, the filter is deployed into the vessel and will
capture emboli that are generated or dislodged during balloon
inflation and stent placement. The device consists of a filter
attached to a shaft that can run over the primary crossing
guidewire.
[0133] Referring initially to FIGS. 1 and 2 in this case the filter
element consists of a compressible porous structure polymeric foam
filter element 1 overmoulded onto or joined to a polymeric or
metallic tube or spring or other hollow support element 2. The foam
filter element 1 is compressed into a housing or pod 3 at a distal
end of a catheter 6 to advance it to the required location. Once in
situ the housing 3 is withdrawn or the filter element 1 is
advanced. This action allows the compressed filter element 1 to
expand to the required size and occlude a blood vessel 4 except for
the path or paths provided through the filter element 1. The filter
element 1 is designed to provide a pathway or multiple pathways
through for blood cells and other blood constituents but to capture
emboli of a size greater than the filter pore size. Blood flow rate
is maintained by forming the filter element such that a local
pressure drop across the filter is minimised. The filter element 1
has a proximal inlet end 7 and a distal outlet end 8. The inlet end
7 has a plurality of inlet openings sized to allow blood and
embolic material enter the filter element. The outlet end 8 has a
plurality of outlet openings sized to allow through passage of
blood but to retain undesired embolic material within the body of
the filter element 1.
[0134] The filter element 1 in this case is of a porous structure
or polymeric foam which has a open cell structure with a typical
density less than 400 kg per cubic meter. Preferably the density
will be less than 100 kg per cubic meter and ideally will be less
than 50 kg per cubic meter. The filter properties may be achieved
through appropriately sizing the pores of the foam body or
additionally by removing material to create appropriately sized
pathways for blood to flow through and means of capturing larger
sized particles. A number of configurations for this will be
described that can tailor both the sizing and flow rate
characteristics of the filter element 1 either independently or
simultaneously. The actuation and deployment of the filter element
1 are achieved by providing relative motion between the filter
element 1 and the covering housing 3.
[0135] It is not desirable that the catheter moves relative to the
support element 2 during manipulation. Motion may be prevented by
fixing the inner support element 2 to the catheter 6 in a number of
different ways. In the embodiment described this is achieved by way
of having a catheter 6 covering the support element 2 and filter
element 1 to which it is fixed. As illustrated in FIGS. 3A and 3B
the fixing may be achieved by means of a shrink wrap tube 5 that is
shrunk to capture both the covering catheter 6 and the inner
support element 2. Once the fitter element 1 is in the desired
position, the shrink-wrap joint is broken using the peel-away tab 7
to allow the outer catheter 6 to be removed proximally and leave
the support element 2 and filter element 1 in place.
[0136] A number of other workable arrangements could be used to
join the support element 2 and catheter 6. A split collar
arrangement 10 (FIGS. 4 & 5) could be used that was removable
by means of unlocking a screw or a number of screws or an
arrangement such as a jubilee clip 11 (FIGS. 6 & 7) which could
be loosened to free the bond between the components.
[0137] Another method that could be used to temporarily fix the
inner support element 2 to the outer sheath or catheter 6 is a
Hemostasis High Pressure Touhy Borst Y adapter. This commercially
available adapter is needed to enable the physician to flush the
sheath before being inserted into the artery. The outer sheath or
catheter may be permanently attached to this adapter. The inner
tubular support element 2 runs through the Touhy Borst section of
the adapter and thus through the center of the sheath. Tightening
the Touhy Borst section releases this grip, thus allowing the inner
tubular support element 2 and the outer sheath to move relative to
each other once again.
[0138] The design of the filter element 1 is shown in a typical
embodiment in FIG. 8, where a foam substrate filter body has
material removed to create a series of channels or pathways 20 for
the blood to flow through but which would cause a restriction for
embolic material to prevent it going through the filter. The
pathways 20 may be machined using a variety of methods such as
laser cutting with excimer, YAG, CO2, or other laser type, freezing
and machining or lost wax machining. A number of arrangements are
possible with the sizing reflective of the requirements. In the
configuration shown, the inlet holes are preferably 0.5 mm or
greater in size to capture large emboli while the outlet holes are
less than 300 microns. These can be easily varied as required to
filter differing sized particles from a variety of fluid media in a
variety of vessel sizes.
[0139] The filter media can be bonded to the tubing substrate by
way of a variety of available technologies such as mechanical,
solvent or adhesive bonding and overmoulding in an arrangement such
that the substrate is placed in the mould and the polymer material
is then shot into the mould and forms a bond at the interface
between the substrate and the polymer element. Additionally, the
foam or porous element could be extruded into or bonded to a
substrate.
[0140] It will be noted that the filter element 1 has a rounded
distal end 21 to facilitate insertion and the proximal end 22 is
tapered to facilitate withdrawal. Alternatively, as illustrated in
FIG. 9 the distal end 23 may be tapered.
[0141] Referring particularly to FIG. 10 at the end of the
interventional procedure, the device can be withdrawn by means of
advancing a large bore catheter 25 to the proximal end 22 of the
filter 1 and pulling the filter 1 into the catheter 25. The filter
1 will compress and seal the proximal filter inlet openings after
the initial taper is drawn into the catheter 25 before collapsing
the rest of the filter body. Once the filter 1 has been withdrawn
fully into the catheter 25 it can then be readily removed from the
patient. The filter 1 will contain the captured emboli.
[0142] In another embodiment of the invention as illustrated in
FIGS. 11 to 15, an arrangement of spokes 30 covered with a membrane
or porous fabric or mesh 31 can be folded down into a delivery
sheath or pod for subsequent deployment in the target vessel. The
design consists of a substrate shaft 33 onto which are radially or
circumferentially bonded a series of pre-shaped wires 30. The wires
30 are joined on the proximal end into a movable collar or tube 32
mounted on the substrate shaft 33 and at the distal end into a
fixed tube 34. The tube 32 can move proximally and distally to the
extent that it will open and close the assembly in a manner similar
to an umbrella and thereby occlude vessel. The spokes 30 may be
fabricated in a range of metallic, polymeric and composite
materials. The frame is covered with a porous material 31, whose
pore size is selected to allow the media through, effectively
creating a screen filter. The covering fabric 31 could be bonded to
the frame 30 by means of casting a material such as a polyurethane
or PET onto the pre-formed shape. The film may then be lazed or
made porous by other means such as mechanical or heat punching or
by chemical etching. Additionally, incorporating a soluble particle
in the polymer matrix, subsequent removal of the particle would
render the polymer porous. Control of porosity is achieved by
tailoring the ratio and distribution of the particulate within the
polymer matrix.
[0143] When the assembly is configured longitudinally a sheath or
pod may be slid over it to cover it. As with the previous
embodiment, the loaded catheter is positioned in the required
location by threading it over the guidewire. Once the desired
location has been reached, the sheath may be moved back and allow
the assembly be exposed in the vessel. A sleeve 35 can then be
moved forward to open or deploy the assembly. The relative sizing
and choice of materials operates such that the sleeve 35 will not
slide on the inner tubing unless an external force is applied to
move it. When deployed, the device will remain open and catch
whatever embolic material is moving towards the brain. At the end
of the procedure, a pre-shaped component advanced over the inner
tube will dock with the movable tube 32 and allow it to be slid
towards the proximal end of the device with the result that the
structure is closed. A larger sheath can then separately be
advanced to the site of the filter and the filter may be pulled or
manipulated proximally into it. When withdrawn into the sheath or
catheter, device may then be removed either over the guidewire or
with it.
[0144] Referring to FIGS. 16 and 17 there is illustrated another
embolic protection device. In this case the filter element has a
design based on a shaped thin film component bonded onto the tubing
substrate. A wide number of shapes could be made to work in the
application. An element which through its preshaped form will open
into a framework 40 when the restraining force is removed is
attached to a tubing substrate 41. The frame element 40 can be
manufactured from a range of metallic or polymeric components such
as a shape memory alloy like Nitinol or a shape memory polymer or a
shaped stainless steel or metal with similar properties that will
recover from deformation sufficiently to cause the film component
to open. Otherwise a mechanical movement or actuation can cause the
device to open. The shaped film component is attached over the
frame 40. The film component can be formed by a number of known
commercial technologies. These include blow-moulding, dip casting,
solution casting, spin casting and film welding as well as adhesive
joining. The object is to produce a formed shape that can be opened
in the vessel to a size and shape to occlude it. Filtration is
achieved by creating a pattern or series of openings in the
proximal and distal ends of the element that allows emboli and
blood to enter the device but having a range of smaller openings in
the distal end to allow the blood to pass through to the distal
vasculature while retaining the emboli.
[0145] While being delivered to the required site, the filter
element is covered or restrained by a sheath. By withdrawing the
sheath or advancing the filter device, the filter is uncovered and
opens to occlude the vessel. During the procedure, the filter acts
to capture all embolic material that attempts to flow distally. At
the end of the procedure, a sheath is advanced to the proximal end
of the device and the filter is pulled proximally into it with the
retained emboli captured. In this design configuration the emboli
can easily be removed for analysis afterwards.
[0146] The invention above is described as it relates to a device
that can be used over a medical guidewire. The opportunity exists
to configure the invention in a manner that it could in itself be
used as the primary crossing device. All of the filter designs
described above could be mounted onto either the over the wire or
the primary crossing device as described hereunder. For a primary
crossing device the wire would be bonded to a solid substrate. Some
benefits would accrue in that the pre-diameter onto which the
filter could be wrapped down would be smaller because it would not
need to move over another instrument. FIG. 18 illustrates the
differences involved. The filter element 1 is mounted on the
substrate shaft 33. A collapsible filter support element 50 is
mounted on the substrate shaft 33 at a proximal end of the filter
1. The support element 50 has a number of foldable arms 51 which
collapse against the shaft 33 for deployment and upon release
extend outwardly to expand the filter 1 in the vessel.
[0147] Referring to FIGS. 20 to 22 there is shown alternative
constructions of filter element comprising a compressible filter 1
shown in an expanded position with a larger opening 60 and smaller
outlet openings 61. A collapsible wire support 62 is provided at a
proximal end of the filter 1. The wire support 62 is collapsible
with the filter 1 within a housing or pod for deployment and upon
release expands to support the filter 1 in the vessel 4.
[0148] An alternative filter arrangement is shown in FIGS. 23 to
27. In this case, the filter comprises a Nitinol mesh which is
expandable from a collapsed position shown in FIG. 23 for
deployment to an expanded in use position shown in FIG. 27 to
provide a filter body 55 with proximal inlet 66 and distal outlets
67.
[0149] For a primary crossing device, the distal end of the device
will be flexible and atraumatic. This can be achieved by a number
of means such as fabricating a spring or polymeric element to be
flexible enough to defect when it comes into contact with the walls
of the vessel. The tip section would be mounted distally to the
filter element. An intermediate section of the device will house
the filter 1 which would be covered prior to deployment. A sheath
could be fully the length of the device or attached by an actuator
to a shorter sheath that covers the filter only. The proximal
section of the device will provide a platform for the balloon
dilatation and stent devices. The provision of a platform may be
achieved as shown by removing the proximal covering to expose a
wire or spring assembly. Alternatively, the whole proximal section
could function as the platform. Essentially, to function as the
platform for balloon catheter and stent, the devices should be
sized with an outside diameter dimension that allows free movement
of the catheter systems over it. Typical industry standards for
coronary products permit free movement of devices over a 0.014'' or
0.018'' diameter while peripheral angioplasty applications use a
0.035'' OD.
[0150] Referring to FIG. 28 the tubing substrate 33 onto which the
filter element is bonded can move between two stoppers 63 and 64,
the stoppers are mounted on the primary crossing guidewire 2. The
stoppers can be manufactured from a range of metallic or polymeric
components, which will permit movement of the tubing substrate 33
between them. The stoppers may also be in the form of a step in the
actual medical guidewire. A large variation in distances between
stoppers 63 and 64 could be made to work in this application. The
stoppers are sized to prevent movement of the tubing substrate
either over or under them so that they act as a stop position for
the tubing substrate in both their proximal and distal locations.
The stoppers can be mounted onto the primary crossing guidewire by
a number of known commercial technologies: these include soldering,
welding, braising, crimping and adhesive bonding. The proximal
stopper will be small enough in size to fit into the internal shaft
of the delivery catheter. The filter element can move axially and
rotationally independently of the guidewire. This allows for a good
wire movement and control of filter position. The filter position
will be maintained during the exchange of catheters. Any
commercially known available guidewire can be adapted accordingly
and used with this technique.
[0151] FIG. 29 refers to an "olive" 65; the olive component can be
manufactured from a range of metallic or polymeric components such
as polymeric foams, plastics, stainless steel or metal. The olive
will allow a smooth transition between the guidewire 2 and the pod
3 into which the filter element is loaded and also allows for easy
positioning of the filter element within the pod. The olive can be
directly attached to the guidewire or it may also be attached to a
tubing substrate 33. The olive can be attached to the guidewire or
tubing substrate by a range of known techniques such as adhesive
bonding and soldering. The olive will work as required for a range
of distances distal to the filter element. A wide number of shapes
and sizes could be made to work as the olive component.
[0152] FIG. 30 refers to the filter element 1 when it is positioned
in its most distal position. The filter element may achieve this
position during loading or after deployment. The stopper element 64
prevents the filter element 1 from moving beyond it in the distal
direction.
[0153] FIG. 31 illustrates the filter element in its most proximal
location the filter element may achieve this position when
deploying the device or after deployment. The stopper element 63
prevents the filter element 1 from moving beyond it in the proximal
direction.
[0154] FIG. 32 refers to a floating distal tip in this case a
stopper component 66 is placed proximal to the distal end of the
filter. The most distal end of the filter being fixed to a marker
band 70 or other suitable substrate. The marker band 70 is not
fixed to the substrate tubing 33. This allows the distal end of the
filter freedom of movement in the axial direction beyond the
stopper component. The stopper component can be made to work using
any shape or form so as to prevent movement of the distal end of
the filter in the proximal direction beyond the point of fixturing
of the stopper component. The stopper component may be manufactured
from metals or polymeric material. It can be joined to the tubing
substrate 33 by a number of existing technologies including
adhesive bonding and soldering. The stopper component 66 will work
when placed in any location between 50 and 70. A floating distal
tip on the filter element will facilitate the loading of the filter
element into the loading pod as the filter can now extend in the
axial direction and therefore be wrapped down over a greater
length. This will reduce the loading force required and also reduce
the profile of the loaded filter. The floating distal tip design
will facilitate the loading of a large range of filter designs.
[0155] FIG. 33 refers to a concertina shaped filter with a floating
distal tip. This filter geometry adds to the circumferential
integrity of the filter and thus prevents the formation of creases
along the length of the filter. "A" illustrates the filter as it
will be when in position. "B" illustrates how the distal tip will
extend in the axial direction when the filter element is loaded
into a loading pod. The floating tip design can be used to
accommodate the loading of many filter shape designs. For the
filter design shown a longer pod is needed to accommodate the
increase in axial length of the filter element when loaded.
[0156] FIG. 34 refers to the floating distal tip design with a
spring element 67 incorporated into the design. The spring is
placed distal to the filter element. As previously illustrated in
FIG. 33, the floating distal tip extends in the axial direction
when loaded, the spring acts as a safety device when the filter is
deployed and ensures the return of the floating distal tip to its
primary location. The spring element will be soft enough to allow
the distal tip to extend freely in the distal direction during
loading but stiff enough to push the distal tip back to its primary
location after deployment. The spring element can be manufactured
from either a polymeric or metal component. The spring element can
be mounted onto a substrate 33 and a stopper component used to
prevent axial movement of the spring in the distal direction. Other
methods of keeping the distal end of the spring element stationary
could be used such as bonding, welding, crimping, soldering or
crimping the distal end of the spring onto the substrate 33. This
technique could also be made to work with the spring being part of
the actual guidewire. There are many other configurations by which
a return spring element may be incorporated into the filter as
shown in FIGS. 35 and 36.
[0157] In FIG. 35 the spring element 67 is bonded to the substrate
33 at its proximal end and the distal end of the filter element is
bonded to the spring shaft. This design allows the distal end of
the filter element to extend in the distal direction. The extension
length could be determined by either the positioning of a stopper
68 or the stiffness of the spring. When external forces are removed
from the filter the spring will return the filter to its primary
location. In FIG. 38 a shape memory alloy such as nitinol is used
to return the filter to its primary location. The nitinol support
frame 69 is fixed to the substrate 33 at its proximal end 70 and is
floating at the distal end 71. The shape memory properties of the
nitinol will ensure that the filter element returns to its primary
location. This design can facilitate the use of any other
commercially available or known shape memory alloys. This design
could also be made to work using a spring component.
[0158] FIG. 37 again incorporates the floating distal tip design.
The filter body 55 as previously illustrated in FIG. 27 is mounted
onto a substrate 33. At the proximal end the stent is fixed to the
substrate. The floating distal tip design allows the filter body 55
to extend in the distal direction. As the filter body 55 extends
there is a reduction in its outside diameter and an increase in its
overall length. There may or may not be need for a stopper 68 as
the filter body 55 will extend up to its own elastic limit which is
determined by its size and geometry. The shape memory function of
the filter body 55 will cause the distal tip to return to its
primary location when external forces are removed from it. The
proximal end of the filter body 55 may be fixed to the substrate by
a number of known technologies such as bonding, soldering or
crimping.
[0159] FIG. 38 illustrates a number of different filter designs
which could be made to work as embolic protection devices. These
filter designs all work to reduce the longitudinal length of
creases which may occur should the filter be oversized, therefore
acting as crease breakers. Either ends of the filters shown could
act as both proximal and distal ends for the filter. The filter
body may be tubular or frusto-conical.
[0160] Referring to FIGS. 40 to 42 there is illustrated an embolic
protection device according to the invention indicated generally by
the reference number 100. The device 100 has a guidewire 101 with a
proximal end 102 and a distal end 103. A tubular sleeve 104 is
slidably mounted on the guidewire 101. A collapsible filter 105 is
mounted on the sleeve 104, the filter 105 being movable between a
collapsed stored position against the sleeve 104 and an expanded
position as shown in the drawings extended outwardly of the sleeve
104 for deployment in a blood vessel.
[0161] The sleeve 104 is slidable on the guidewire 101 between a
pair of spaced-apart end stops, namely an inner stop 106 and an
outer stop which in this case is formed by a spring tip 107 at the
distal end 103 of the guidewire 101.
[0162] The filter 105 comprises a mesh net 110 mounted over a
collapsible support frame 111. The mesh net 110 is gathered into
the sleeve 104 at each end, the net 110 being rigidly attached to a
proximal end 112 of the sleeve 104 and the net 110 being attached
to a collar 115 which is slidable along a distal end 114 of the
sleeve 104. Thus the distal end of the net 110 is longitudinally
slidable along the sleeve 104. The support frame 111 is also fixed
at the proximal end 112 of the sleeve 104. A distal end 116 of the
support frame 111 is not attached to the sleeve 104 and is thus
also free to move longitudinally along the sleeve 104 to facilitate
collapsing the support frame 111 against the sleeve 104. The
support frame 111 is such that it is naturally expanded as shown in
the drawings and can be collapsed inwardly against the sleeve 104
for loading in a catheter 118 or the like.
[0163] The filter 105 has large proximal inlet openings 117 and
small distal outlet openings 119. The proximal inlet openings 117
allow blood and embolic material to enter the filter body, however,
the distal outlet openings 119 allow through passage of blood but
retain undesired embolic material within the filter body.
[0164] An olive guide 120 is mounted at a distal end of the sleeve
104 and has a cylindrical central portion 121 with tapered ends
122,123. The distal end 122 may be an arrowhead configuration for
smooth transition between the catheter and olive surfaces. The
support frame 111 is shaped to provide a circumferential groove 125
on the filter net 110. If the filter is too large for a vessel, the
net may crease and the groove 125 ensures any crease does not
propagate along the filter.
[0165] Enlarged openings are provided at a proximal end of the
filter net 110 to allow ingress of blood and embolic material into
an interior of the net 110.
[0166] In use, the filter 105 is mounted in a collapsed state
within a distal end of the catheter 118 and delivered to a
deployment site. When the filter is correctly positioned the
catheter 118 is retracted allowing the support frame 111 to expand
inflating the net 110 across the vessel in which the filter is
mounted. Blood and emboli can enter the enlarged openings at a
proximal end of the net 110. The blood will pass through the net
wall, however, the openings or pores in the net are sized so as to
retain embolic material. After use the catheter is delivered along
the guidewire 101 and slid over the filter 105 engaging the
proximal inlet end 112 first to close the openings and then
gradually collapsing the net against the sleeve 104 as the catheter
118 advances over the filter 105. Once the filter 105 is fully
loaded in the catheter 118, it can then be withdrawn.
[0167] It will be noted that a proximal end of the filter is fixed
and a distal end of the filter is longitudinally movable along the
sleeve to facilitate collapsing of the filter net.
[0168] Further, the catheter engages the proximal end of the filter
net first thus closing the filter net inlet and preventing escape
of embolic material from the filter net as the filter net is being
collapsed.
[0169] Conveniently the tip of the catheter which forms a housing
or pod for reception of the filter is of an elastic material which
can radially expand to accommodate the filter with the captured
embolic material. By correct choice of material, the same catheter
or pod can be used to deploy and retrieve the filter. For
deployment, the elastic material holds the filter in a tightly
collapsed position to minimize the size of the catheter tip or pod.
Then, when retrieving the filter, the catheter tip or pod is
sufficiently elastic to accommodate the extra bulk of the filter
due to the embolic material.
[0170] Also, the filter is not fast on the guidewire and thus
accidental movement of the guidewire is accommodated without
unintentionally moving the filter, for example, during exchange of
medical devices or when changing catheters.
[0171] It will also be noted that the filter according to the
invention does not have a sharp outer edge as with many umbrella
type filters. Rather, the generally tubular filter shape is more
accommodating of the interior walls of blood vessels.
[0172] Conveniently also when the filter has been deployed in a
blood vessel, the catheter can be removed leaving a bare guidewire
proximal to the filter for use with known devices such as balloon
catheter and stent devices upstream of the filter.
* * * * *