U.S. patent application number 10/184327 was filed with the patent office on 2002-11-14 for minimally invasive medical device deployment and retrieval system.
This patent application is currently assigned to Microvena Corporation. Invention is credited to Anderson, Kent D., Kusleika, Richard S., Nguyen, Duy.
Application Number | 20020169474 10/184327 |
Document ID | / |
Family ID | 26822266 |
Filed Date | 2002-11-14 |
United States Patent
Application |
20020169474 |
Kind Code |
A1 |
Kusleika, Richard S. ; et
al. |
November 14, 2002 |
Minimally invasive medical device deployment and retrieval
system
Abstract
The present invention provides a medical device retrieval system
comprising a working element carried by a flexible, elongate shaft,
the working element having a proximal profile and the shaft
extending proximally from the working element and a retrieval cover
slidably carried along the shaft of the medical device, the cover
having a deployed configuration and being capable of being
compressed into a compressed configuration for deployment, yet
resiliendy substantially return to the deployed configuration; the
cover in its deployed configuration having a radially reduced
proximal portion, a distally open distal end defining a distal
opening having a maximum dimension at least as great as the maximum
dimension of the proximal profile of the working element of the
medical device, and an elongate internal recess defined between the
proximal portion and the distal end.
Inventors: |
Kusleika, Richard S.; (Eden
Prairie, MN) ; Nguyen, Duy; (Savage, MN) ;
Anderson, Kent D.; (Champlin, MN) |
Correspondence
Address: |
Lawrence M. Nawrocki
NAWROCKI, ROONEY & SIVERTSON, P.A.
Broadway Place East, Suite 401
3433 Broadway Street Northeast
Minneapolis
MN
55413
US
|
Assignee: |
Microvena Corporation
|
Family ID: |
26822266 |
Appl. No.: |
10/184327 |
Filed: |
June 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10184327 |
Jun 27, 2002 |
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09936248 |
Jan 28, 2002 |
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09936248 |
Jan 28, 2002 |
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PCT/US00/06212 |
Mar 8, 2000 |
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60124156 |
Mar 8, 1999 |
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2/013 20130101;
A61B 17/221 20130101; A61F 2230/0006 20130101; A61F 2230/0093
20130101; A61F 2230/0069 20130101; A61F 2/011 20200501; A61F
2230/008 20130101; A61F 2002/018 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A medical device retrieval system, comprising: a) a medical
device comprising a working element carried by a flexible, elongate
shaft, the working element having a proximal profile and the shaft
extending proximally from the working element; and b) a retrieval
cover slidably carried along the shaft of the medical device, the
cover having a deployed configuration and being capable of being
compressed into a compressed configuration for deployment, yet
resiliently substantially return to the deployed configuration; the
cover in its deployed configuration having a radially reduced
proximal portion, a distally open distal end defining a distal
opening having a maximum dimension at least as great as the maximum
dimension of the proximal profile of the working element of the
medical device, and an elongate internal recess defined between the
proximal portion and the distal end; the cover in its compressed
configuration being radially compressed inwardly toward the shaft
and being distally open with the distal end defining the
distal-most portion of the cover.
2. The system of claim 1 further comprising a retrieval sheath, the
retrieval sheath being slidable along the shaft of the medical
device and being positioned distally of the cover when the cover is
in its deployed configuration.
3. The system of claim 2 where in the retrieval sheath has an inner
diameter smaller than an outer diameter of the cover in its
deployed configuration, the sheath being adapted to slide distally
along the cover to compress the cover about the medical device.
4. The system of claim 2 wherein the retrieval sheath has a body
and a distal tip comprising a distal length of the retrieval
sheath, the distal tip being bent at an angle of between about 5
and about 30.degree. with respect to the body.
5. The system of claim 4 wherein the distal tip is between about 1
cm and about 5 cm in length.
6. The system of claim 4 wherein the distal tip further comprises a
radiopaque marker band.
7. A medical device retrieval system, comprising: a) a medical
device comprising a working element carried by a flexible, elongate
shaft having an outer diameter, the working element having a
proximal profile and the shaft extending proximally from the
working element; b) a retrieval sheath being slidable along the
shaft of the medical device, the retrieval sheath having a beveled
distal end with a distal lumen; c) a deployment stylet slidable
along the shaft of the medical device, the deployment stylet having
a distal tip tapering distally from a first diameter approximating
a diameter of the distal lumen of the sheath to a second diameter
more closely approximating the outer diameter of the medical device
shaft, providing a transition between the shaft of the medical
device and the distal end of the retrieval sheath when the
deployment stylet is positioned such that the distal tip extends
distally beyond the distal end of the retrieval sheath; and d) a
retrieval cover slidable along the shaft of the medical device and
being exchangeable for the stylet therealong, the cover having a
deployed configuration and being capable of being compressed into a
compressed configuration for siding within the lumen of the
retrieval sheath yet resiliently substantially return to the
deployed configuration; the cover in its deployed configuration
having a radially reduced proximal portion, a distally open distal
end defining a distal opening having a maximum dimension at least
as great as the maximum dimension of the proximal profile of the
working element of the medical device, and an elongate internal
recess defined between the proximal portion and the distal end; the
cover in its compressed configuration being radially compressed
inwardly toward the shaft and being distally open with the distal
end defining the distal-most portion of the cover.
8. A retractable medical device system, comprising: a) a medical
device comprising a working element carried by a flexible, elongate
shaft; b) a retrieval cover slidable along the shaft of the medical
device, the cover having a radially reduced proximal portion, a
distally open distal end and an elongate tubular wall extending
therebetween and defining a recess; the working element of the
medical device being completely retained within the recess of the
cover such that the tubular wall extends distally beyond the
medical device; and c) a retrieval sheath, the retrieval sheath
having a lumen and being slidable with respect to both the medical
device and the cover, at least a proximal length of the working
element of the medical device and the cover being retained within
the lumen of the retrieval sheath, the retrieval sheath radially
compressing the proximal, length of the cover such that an
intermediate portion of the wall tightly engages a surface of the
medical device.
9. A method of retrieving particulate or other foreign material
within a channel of a patient's body, comprising: a) providing a
medical device having a working element and a flexible, elongate
shaft adapted to follow a path within the channel; a distally open
cover slidable with respect to the shaft; and a retrieval sheath
moveable with respect to the cover and the shaft; b) positioning
the medical device within the vessel to engage a wall of the
channel and trap the material within the channel, the cover and the
retrieval sheath being spaced proximally of the working element
along the shaft of the medical device, the cover being radially
compressed within the lumen of the retrieval sheath such that it
has a distally open distal end and a wall defining a recess, the
wall engaging an inner surface of the retrieval sheath; c) moving
the cover distally with respect to the retrieval sheath, thereby
permitting the cover to radially expand into a deployed
configuration wherein the distal end remains distally open and the
endosure is radially expanded, the cover expanding radially
outwardly into the deployed configuration without having to invert
on itself; d) moving the cover distally with respect to the medical
device and into engagement with a surface of the medical device to
form therebetween an enclosure; e) moving the retrieval sheath
distally with respect to the cover to urge the cover to collapse
about the medical device and tightly engage the surface of the
medical device.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to minimally
invasive surgical procedures, e.g., angioplasty and atherectomy
procedures, and has particular utility in connection with
retrieving a medical device which has already been deployed. In one
embodiment, the invention provides a vascular filter which can be
retrieved with minimal risk of dumping the entrained contents back
into the patient's bloodstream.
BACKGROUND OF THE INVENTION
[0002] In some medical procedures, a minimally invasive medical
device is used to capture or dislodge material from within a
patient's vascular system or other body vessel. For example, in
certain procedures, balloon catheters are positioned such that the
deflated balloon is placed distally of a vascular occlusion.
Typically these vascular occlusions are relatively soft,
uncalcified deposited along the walls of an artery. The balloon
then may be inflated and drawn proximally. This will tend to
dislodge any atheromatous material and withdraw it proximally with
the balloon. In current procedures, an aspiration catheter will be
moved distally into position adjacent the balloon and will be used
to aspirate the dislodged material from the vessel.
[0003] A number of other minimally invasive surgical procedures are
being used to treat vascular occlusions. These procedures include
rotational atherectomy and balloon angioplasty. With the increasing
use of vascular stents, it has been discovered that tissue or other
material may build up inside a stent, reducing the patency of the
vessel through the stent. In the course of improving the patency of
the blood vessel utilizing these techniques, there is a risk that
the material which was formally causing the obstruction within the
vessel can simply float downstream with the flow of blood to the
vessel. Accordingly, there is an increasing recognition of the
value of taking steps to capture the dislodged material.
[0004] A number of researchers have proposed various traps or
filters for capturing the particulate matter or other embolic
particles let loose in such procedures. Some filters are
permanently implanted within the vessel. Emboli trapped within the
filter are either aspirated out of the interior of the filter or
are dissolved using drugs. Other filters are intended to be
temporary in nature, typically being removed after the angioplasty,
atherectomy or other procedure is complete. Generally, the goal is
to retract the filter with the thrombi trapped therein.
Unfortunately, many designs of such temporary filters may get
relatively difficult or complex to retract the trap back in to the
catheter through which it was delivered without simply dumping the
trapped thrombi back in to the bloodstream.
[0005] One particularly advantageous vascular filter is shown in
co-pending U.S. patent application Ser. No. 08/272,425, and
International Patent Application No. PCT/US95/08613, which was
published as International Publication No. WO 96101591, the
teachings of which are specifically incorporated herein by
reference.
[0006] FIGS. 11-16 of WO 96/01591 are attached hereto as FIGS. 1-6
of the present application. FIG. 1 is a vascular trap which is
suitable for use in temporarily filtering embolic particles and the
like from blood passing through a patient's vascular system. This
device would most frequently be used to filter emboli from a
patient's blood when another medical procedure is being performed,
such as by using the trap in conjunction with a rotating cutting
blade during an atherectomy, with a balloon catheter during
angioplasty, or with a device used to clear the lumen of a stent
during a stent cleaning procedure. It is to be understood, though,
that the trap could also be used in other similar applications,
such as in channels in patient's bodies other than their vascular
systems.
[0007] The vascular trap 250 of FIGS. 1A and 1B comprises a
generally umbrella-shaped basket 270 carried adjacent a distal end
of a guidewire 260. The guidewire in this embodiment includes a
tapered distal section 262 with a spirally wound coil 264 extending
a distal length of the wire. Guidewires having such a distal end
are conventional in the art. The basket 270 is positioned generally
distally of the coil 264, and is desirably attached to the
guidewire approximately with the proximal end of the tapered
section as shown in these drawings.
[0008] The basket 270 of the device shown in WO 96/01591 (shown in
its collapsed configuration in FIG. 1A) includes a distal band 272
and a proximal band 274. The distal band may be made of a
radiopaque material, such as gold, platinum or tungsten, and is
affixed directly to the shaft of the guidewire 260. This attachment
may be made by any suitable means, such as by welding, brazing or
soldering. Alternatively, the distal band 272 may comprise a bead
of a biocompatible cementitious material, such as a curable organic
resin. WO 96/01591 teaches that a radiopaque metal or the like can
be imbedded in the cementitious material to increase the visibility
of the band for fluoroscopic observation. The proximal band 274 may
be formed of a hypotube sized to permit the tube to slide along the
guidewire during deployment. The inventors of that prior
application suggest that the hypotube be made of a metallic
material; a thin-walled tube of a NiTi alloy should suffice. If so
desired, the proximal band may be formed of a more radiopaque
metal, or a NiTi alloy band can have a radiopaque coating applied
to its surface.
[0009] As taught in some detail in WO 96/01591, the basket 270
taught therein is formed of a metal fabric. The metal fabric of
this embodiment is optimally initially formed as a tubular braid
and the ends of the wires forming the braid can be attached
together by means of the bands 272, 274 before the fabric is cut to
length. These bands 272, 274 will help prevent the metal fabric
from unraveling during the forming process. (The method of forming
the basket 270 is described in great detail in WO 96/01591 and this
process is still believed to provide a suitable means for creating
such a basket. The process is also discussed briefly below in
connection with FIG. 6.)
[0010] When the device is in its collapsed state for deployment in
a patient's vessel (as illustrated in FIG. 1A), the basket 270 of
this device is said to be collapsed toward the axis of the
guidewire 260. The distal 272 and proximal 274 bands are spaced
away from one another along the length of the guidewire, with the
fabric of the device extending therebetween. This publication
teaches it is preferred that the basket is in its collapsed engages
the outer surface of the guidewire to permit the device to be
deployed through a relatively small lumen of a catheter or another
medical device.
[0011] When the device is deployed in a patient's vascular system,
the basket will take on an expanded configuration wherein it
extends outwardly of the outer surface of the guidewire. As best
seen in FIG. 1B, the shape of the basket 270 when deployed may
generally resemble a conventional umbrella or parachute, having a
dome-like structure curving radially outwardly from the guidewire
moving proximally from the distal band 272. It is to be understood
that other suitable shapes could easily perform the desired
filtering function, such as a conical shape wherein the slope of
the device changes more linearly than the smooth, rounded version
shown in FIG. 1B. A relatively flat, disc shape may also suffice,
but it is preferred that the device have a cavity or recess
(discussed below) to better retain emboli or other material
captured thereby. In this expanded configuration, the two bands
272, 274 are closer together, with the distal band 272 optimally
being spaced only a short distance from the proximal band 274, as
illustrated.
[0012] In moving from its collapsed state (FIG. 1A) to its expanded
state (FIG. 1B), the metal fabric of this device turns in on
itself, with a proximal portion 282 of the collapsed basket being
received within the interior of a distal portion 284 of the
collapsed basket. This produces a two-layered structure having a
proximal lip 286 spaced radially outwardly of the guidewire,
defining a proximally-facing cup-shaped cavity 288 of the basket.
When blood (or any other fluid) flows through the basket in a
distal direction, any particulate matter in the blood, e.g. emboli
released into the bloodstream during atherectomy or angioplasty
procedures, will tend to be trapped in the cavity 288 of the
basket.
[0013] WO 96/01591 teaches that the precise dimensions of the metal
fabric can be varied as desired for various applications. If the
device 250 is to be used as a vascular filter to trap emboli
released into the blood, for example, this reference teaches that
the pores (i.e. the openings between the crossing metal strands) of
the fabric are desirably on the order of about 1.0 mm. These
inventors deemed this to be the minimum size of any particles which
are likely to cause any adverse side effects if they are allowed to
float freely within a blood vessel. They teach that the pores
should not be too small, though, because the blood (or other fluid)
should be free to pass through the wall of the basket 270. If so
desired, the basket may be coated with a suitable anti-thrombogenic
coating to prevent the basket from occluding a blood vessel in
which it is deployed.
[0014] When a fabric having 1.0 mm pores is used to form this
basket 270, the forming process reorients the wires relative to one
another and in some areas (e.g. adjacent the proximal lip 286) the
pores tend to be larger than 1.0 mm. However, because the basket's
walls are formed of essentially two thicknesses 282, 284 of the
fabric, the effective pore size of the device may be significantly
reduced even at these locations.
[0015] The device 250 of FIGS. 11 is also provided with tethers 290
for collapsing the basket 270 during retraction. The basket may
include four independent tether wires, each of which extends
proximally from the proximal lip 286 of the deployed basket. The
authors suggested, though, that the four tether wires illustrated
in the drawings be formed of two longer wires, with each wire
extending peripherally about a portion of the proximal lip of the
basket. These tether wires may be intertwined with the wires of the
metal fabric to keep the tethers in place during use. When such
tethers are retracted or drawn down toward the guidewire, the wires
extending along the proximal lip of the basket will tend to act as
drawstrings, drawing the proximal end of the basket radially
inwardly toward the guidewire. This tends to dose the basket and
entrap any material caught in the cavity 288 of the basket during
use so that the basket can be retracted without the use of a
cover.
[0016] The tether wires 290 may extend along much of the length of
the guidewire so that they will extend outside the patient's body
during use of the device 250. When it is desired to collapse the
basket for retrieval, the operator can simply hold the guidewire
260 steady and retract the tethers with respect to the guidewire.
This can tend to be relatively cumbersome, though, and may be too
difficult to effectively accomplish without breaking the tethers if
the device is deployed at a selective site reached by a tortuous
path, such as in the brain.
[0017] To address this issue, the authors suggest, as shown in
FIGS. 1A and 1B, that the tethers 290 be attached to the guidewire
260 at a position spaced proximally of the basket. The tethers may,
for example, be attached to a metal strap 292 or the like and this
strap 292 may be affixed to the shaft of the guidewire. When it is
desired to close the proximal end of the basket for retraction,
they suggest urging an external catheter (not shown) distally
toward the basket 270. When the catheter encounters the radially
extending tethers, the distal end of the catheter will tend to draw
the tethers toward the guidewire as the catheter is advanced, which
will, in turn, tend to draw the proximal end of the basket
closed.
[0018] FIGS. 2A and 2B illustrate an alternative embodiment of the
device shown in FIGS. 1A and 1B, also in accordance with the
teachings of WO 96/01591. FIG. 2A shows the device collapsed in a
catheter C for deployment while FIG. 2B shows the device in its
deployed configuration. In FIGS. 2A and 2B, the basket 270 is much
the same as that outlined above in connection with FIGS. 1A and 1B.
In the embodiment of FIGS. 12, though, the distal band 272 is
affixed to the guidewire 260' at the distal tip of the guidewire.
The guidewire 260' is of the type referred to in the art as a
"movable core" guidewire. In such guidewires, a core wire 265 is
received within the lumen of a helically wound wire coil 266 and
the core wire 265 extends distally beyond the distal end of the
coil 266. A thin, elongate safety wire 268 may extend along the
entire lumen of the coil 266 and the distal end of the safety wire
may be attached to the distal end of the coil to prevent loss of a
segment of the coil if the coil should break.
[0019] In the embodiment of FIGS. 1A and 1B, the proximal ends of
the tethers 290 are attached to a metal strap 292 which is itself
attached the shaft of the guidewire 260. In FIGS. 2A and 2B, the
tethers are not attached to the core wire 265 itself. Instead, the
tethers are attached to the coil 266 of the guidewire. The tethers
may be attached to the coil by any suitable means, such as by means
of laser spot welding, soldering or brazing. The tethers 290 may be
attached to the coil 266 at virtually an spot along the length of
the coil. As illustrated in these drawings, for example, the
tethers may be attached to the coil adjacent the coil's distal end.
However, if so desired the tethers may be attached to the coil at a
location space more proximally from the basket 270.
[0020] An external catheter such as that referred to in the
discussion of FIG. 1A, but not shown in that figure, is illustrated
in FIGS. 2A and 2B. Once the basket 270 is deployed in a patient's
vessel to substantially reach the expanded configuration shown in
FIG. 2B and the basket has performed its intended filtration
function, the external catheter C can be urged distally toward the
basket 270. As this catheter is urged forward, the tethers will
tend to be drawn into the distal end of the catheter, which is
substantially narrower than the proximal lip 286 of the basket.
This will tend to draw the tethers down toward the guidewire and
help close the basket, as explained above.
[0021] FIGS. 3-5 illustrate yet another alternative embodiment of a
vascular trap in accordance with WO 96/01591. This vascular trap
300 includes a basket 320 received over a guidewire 310. In most
respects, the basket 320 is directly analogous to the basket 270
illustrated in FIGS. 1-2. The basket 320 includes a proximal band
322 and a distal band 324. As in the device of FIGS. 2A and 2B, the
distal band may be attached to the guidewire adjacent its distal
end. If so desired, though, a structure such as is shown in FIGS.
1A and 1B, wherein the guidewire extends distally beyond the
basket, could instead be used.
[0022] As best seen in its collapsed state (shown in FIG. 3), the
basket includes a distal segment 325 and a proximal segment 326,
with the distal end of the distal segment being attached to the
distal band 324 and the proximal end of the proximal segment being
attached to the proximal band 322. When the basket 320 is in it
expanded configuration (shown in FIG. 4), the proximal segment 326
is received within the distal segment 325, defining a proximal lip
328 at the proximal edge of the device. The wall of the basket thus
formed also includes a cavity 329 for trapping solids entrained in
a fluid, such as emboli in a paient's blood stream.
[0023] The basket 320 of FIGS. 3-5 is also shaped a little bit
differently than the basket 270 of the previous drawings. The
primary difference between these two baskets is that the basket 320
is a little bit shorter along its axis that is the basket 270. This
different basket shape is simply intended to illustrate that the
basket of a vascular trap in accordance with the invention can have
any of a wide variety of shapes and no particular significance
should be attached to the slightly different shapes shown in the
various drawings.
[0024] In the vascular traps 250 and 250' of FIGS. 1 and 2,
respectively, tethers were used to draw down the proximal end of
the basket 270 to close the basket for retraction. In the
embodiment shown in FIGS. 3-5, though, the trap 300 includes a
basket cover 340 positioned proximally of the basket 320. The
basket cover may also be formed of a metallic tubular braid and is
also adapted to be collapsed to lay generally along the outer
surface of the guidewire 310. The cover 340 is not directly affixed
to the guidewire at any point, though, but is instead intended to
be slidably along the guidewire. As best seen in FIGS. 3 and 4
wherein the cover is in its collapsed state, the cover 340 includes
a distal hypotube 342 and a proximal control hypotube 344, with the
distal hypotube being attached to the distal end of the cover 340
and the proximal control hypotube 344 being attached to the
proximal end of the cover.
[0025] The cover 340 is shown in its deployed, expanded
configuration in FIG. 5. As shown in that figure, the cover has a
similar structure to that of the basket 320, but is oriented to be
open distally rather that proximally, as is the basket. As best
seen in FIGS. 3 and 4 wherein the cover is in its collapsed state,
the cover has a distal segment 352 and a proximal segment 354. When
the cover is deployed by urging it distally out of the distal end
of the deployment catheter C, the cover 340 will tend to
resiliently return to its expanded configuration and the distal
hypotube 342 will slide axially proximally along the guidewire
toward the proximal control hypotube 344. This will invert the
collapsed cover so that the distal section 352 is generally
received within the proximal section 354, defining a distal lip 358
of the cover.
[0026] WO 96/01591 teaches that the proximal control hypotube 344
of this cover may extend along a substantial portion of the length
of the catheter 310 so that it extends out of the patient's body
when the device 300 is in place. By grasping the control hypotube
and moving it relative to the guidewire 310, an operator can
control the position of the cover 340 with respect to the basket
320, which is affixed to the guidewires. As explained in more
detail below in connection with the use of the device 300, once the
basket has been deployed and has been used to filter objects
entrained in the fluid (e.g. emboli in blood), the cover 340 may be
deployed and the trap may be drawn proximally toward the cover by
moving the guidewire proximally with respect to the control
hypotube 344.
[0027] The inner diameter of the distal lip 358 of the cover is
desirably slightly larger than the outer diameter of the proximal
lip 328 of the basket. Hence, when the basket is drawn proximally
toward the cover it will be substantially enclosed therein. The
cover will therefore tend to trap any emboli (not shown) or other
particulate matter retained within the cavity 330 of the basket. A
retrieval sheath S may then be urged distally to engage the outer
surface of the cover 340. This will tend to cause the cover to
collapse about the basket, tightly engaging the outer surface of
the basket. This somewhat collapsed structure can then be withdrawn
from the patients channel and removed from the patient's body. By
enclosing the basket within the cover, the likelihood of any
filtered debris within the basket being lost as the basket is
retrieved will be substantially eliminated.
[0028] FIG. 6 illustrates the molding element 370 suggested in WO
96/01591 for use in making a basket 270. Although the basket 320
and cover 340 of the trap 300 are shaped somewhat differently, an
analogous molding element can be used for these portions of the
trap 300 as well by simply modifying some of the dimensions of the
molding element 370, but retaining the basic shape and structure of
the molding element. It also should be understood that the molding
element 370 is merely one possible molding element for forming a
shape such as that of the basket 270 and WO 96/01591 teaches a
variety of different molding elements and notes that other designs
will be apparent to those skilled in the art.
[0029] The molding element 370 of FIG. 6 has an outer molding
section 372 defining a curved inner surface 374 and an inner
molding section 376 having an outer surface 378 substantially the
same shape as the curved inner surface 374 of the outer molding
section. The inner molding section 376 should be sized to be
received within the outer molding section, with a piece of the
metal fabric (not shown) being disposed between the inner and outer
molding sections. In a preferred embodiment, the inner surface 374
of the outer molding element and the outer surface 378 of the inner
molding section each include a recess (375 and 379, respectively)
for receiving an end of the braid. The molding surface of this
molding element 370, to which the fabric will generally conform,
can be considered to include both the inner surface 374 of the
outer molding section and the outer surface 378 of the inner
molding section.
[0030] WO 96/01591 teaches that the two molding sections 372, 376
are spaced apart from one another and a length of a tubular braid
of metal fabric (not shown in FIG. 6) is disposed between these
molding sections. Optimally, one end of the fabric is placed in the
recess 375 of the outer molding section and the other end of the
fabric is placed in the recess 379 in the inner molding section. As
noted above, the ends of the tubular fabric can be damped prior to
this molding process to limit the likelihood that the fabric will
unravel. The inner and outer molding sections can then be urged
generally toward one another. As the ends of the wire approach one
another, the tubular braid will tend to invert upon itself and a
surface of the tubular braid will generally conform to either the
inner surface 374 of the outer molding section or the outer surface
378 of the inner molding section, arriving at a shape analogous to
that of the basket 270 of the traps 250, 250'. The two molding
sections can them be locked in place with respect to one another
and the metal fabric may be heat treated to set the wires in this
deformed configuration.
[0031] This published international application also teaches how
one may use the traps 250, 250' and 300 taught therein. It suggests
that these traps be deployed for use in conjunction with another
medical device and that they will most frequently be retracted from
the patient's body after use. WO 96/01591 uses a balloon
angioplasty procedure and an atherectomy procedures as contexts for
illustrating a method of using such traps. In balloon angioplasty,
balloon catheters having inflatable balloons at their ends are
positioned within a blood vessel so that the balloon is positioned
within a stenosis. These balloons are positioned by tracking the
balloon catheter along a guidewire or the like; the balloons
typically have a central bore therethrough. Once the balloon is
properly positioned, it is inflated and urges radially outwardly
against the stenosis. This will tend to squeeze the stenosis
against the walls of the vessel, improving patency of the
vessel.
[0032] When the stenosis is treated in this fashion, though, there
is a risk that some debris will break free and enter the blood
flowing through the vessel. If left unchecked, this embolus can
drift downstream and embolize a distal portion of the vessel.
Depending on where the embolus comes to rest, the embolization can
result in significant tissue or organ damage. In order to prevent,
or at least substantially limit, such embolization, WO 96/01591
suggests the use of a vascular trap 250, 250' or 300 of with the
balloon catheter. The device should be sized to permit it to be
passed through the lumen of the particular balloon catheter to be
used in the angioplasty.
[0033] In one method taught in WO 96/01591, the trap is deployed
first. The basket (270 or 320) of the trap is guided to a position
located downstream of the desired treatment site through an
introduction catheter (e.g. the catheter C in FIGS. 12-15). The
basket is then urged distally beyond the end of the catheter, which
permits the basket to resiliently substantially return to its
expanded configuration from its collapsed configuration within the
catheter. Once the trap is in place, the balloon catheter can be
exchanged for the introduction catheter, and the balloon catheter
can track the guidewire (260 or 310) of the vascular trap. The
balloon can then be positioned within the stenosis and expanded, as
outlined above. Once the angioplasty has been completed, the
balloon can be deflated again and withdrawn proximally out of the
patient.
[0034] WO 96/01591 also explains that the balloon catheter can be
used to perform the same function as performed by the introduction
catheter in the preceding embodiment. In this embodiment, the
balloon catheter is positioned in the patients vessel so that the
distal end of the balloon catheter is located downstream of the
stenosis. The vascular trap (250, 250' or 300) of the invention is
then passed through the lumen of the balloon catheter and the
basket is urged out of the distal end of the catheter. The basket
will resiliently substantially return to its preferred expanded
configuration, whereupon the balloon catheter can be retracted
along the shaft of the device's guidewire until the balloon is
properly positioned within the stenosis.
[0035] If so desired, the balloon catheter can instead be provided
with a length of standard catheter extending distally beyond the
distal end of the balloon. The balloon can then be positioned
within the stenosis and the basket can be urged out of the distal
end of the distal extension of the catheter. In such an embodiment,
the length of the distal extension of the catheter should be
sufficient to properly position the basket with respect to the
balloon when the basket exits the distal end of the catheter. This
will eliminate the need to perform the separate step of retracting
the balloon into position within the stenosis after the basket is
deployed. The balloon can then be expanded, deflated and withdrawn
as described above.
[0036] WO 96/01591 teaches that much the same procedure can be used
to deploy a vascular trap for use in an atherectomy procedure. In
such procedures, a cutting head is positioned at the distal end of
an elongate, hollow shaft and the cutting head has a bore extending
therethrough. The trap can be deployed in either of the methods
outlined above, but it is anticipated that in most instances the
first procedure will be used, i.e. the basket will be deployed with
an introduction catheter, which will be removed so that the cutting
device can be guided over the guidewire of the vascular trap. This
publication also stresses that the device 250, 250' and 300 could
be used in other medical procedures in other bodily channels
besides a patient's vascular system.
[0037] Since the trap is positioned downstream of the stenosis, any
debris released during one of these procedures will tend to drift
distally toward the basket and be caught therein. In order to
prevent any emboli from simply floating past the trap, it is
preferred that the proximal lip (288 or 328) of the basket be at
least as large as the lumen of the vessel. WO 96/01591 suggests
that the natural dimension of the proximal lip (i.e. where the
basket has fully returned to its expanded configuration) be made
somewhat greater than the vessel's inner diameter so the basket
will firmly engage the wall of the vessel.
[0038] The method of retracting the basket will depend on which
embodiment of the vascular trap is used, namely whether or not the
device includes a cover 340. The device 250 or 250' of FIGS. 1 or
2, respectively, do not include such a cover. However, they do
include tethers 290 which extend proximally from the proximal lip
288 of the basket to an attachment to the guidewire. In either of
these embodiments, a retrieval catheter can be introduced over the
guidewire and urged distally toward the basket. As explained above
in connection with FIGS. 1 and 2, this will tend to draw the
tethers down toward the guidewire, effectively closing the proximal
end of the basket 270. Once the basket is sufficiently dosed, such
as when the proximal lip of the basket engages the distal tip of
the retrieval catheter, the catheter and the vascular trap can be
retracted together from the patients body. By substantially closing
the proximal end of the basket in such a fashion, any emboli which
are captured in the basket when it is deployed can be retained
within the basket until it is removed from the patient's body.
[0039] If so desired, a balloon catheter or like device can instead
be used, with the balloon catheter being used to draw down the
tethers 290 and collapse the basket. The vascular trap can then be
withdrawn with the balloon catheter rather than having to
separately introduce a removal catheter to remove the trap.
[0040] In withdrawing the embodiment illustrated in FIGS. 3-5, the
cover 340 is positioned over the proximal lip of the basket before
the vascular trap 300 is retracted. Once the medical procedure is
completed and any debris has been captured in the basket, the cover
340 is allowed to resiliently substantially return to its expanded
configuration. Once it is deployed proximally of the basket, the
basket 320 can be drawn proximally toward the cover 340 until it
engages or is received within the cover, as noted above in
connection with FIG. 5.
[0041] In actuality, the cover 340 of FIGS. 3-5 may be unable to
return to its full expanded configuration due to the confines of
the vessel in which it is deployed. As explained previously, the
cover 340 is desirably larger than the basket 320 so that the
basket can be received within the cover. However, the basket is
optimally sized to engage the walls of the vessel to prevent the
unwanted passage of emboli or other debris around the edges of the
basket. Accordingly, the distal lip 358 of the cover will engage
the wall of the channel before it expands to its full size. The
walls of most bodily channels, such as blood vessels, tend to be
somewhat elastic, though. The cover 340 will therefore tend to urge
harder against the wall of the vessel than the smaller basket and
may stretch the vessel a little bit more than will the basket. In
this fashion, the cover may still be able to expand to a dimension
large enough to permit the basket to be received in the cavity 356
of the cover. If not, the distal lip 358 of the cover can simply be
brought into close engagement with the proximal lip 328 of the
basket to generally seal the basket.
[0042] Once the cover 340 is brought into engagement with the
basket 320, whether by receiving the basket within the cover or,
less preferably, by engaging the lips 358, 328 of the cover and the
basket, the device can be withdrawn proximally from the patient's
vascular system. The cover will tend to prevent any emboli caught
in the basket during deployment from being inadvertently lost
during withdrawal.
[0043] The vascular traps 250, 250' and 300 shown in FIGS. 1-6
represent a significant advancement over previously available
devices. The embodiment of FIGS. 3-5 shows particular promise in
that the cover permits the user to withdraw the basket with the
emboli entrained therein without having to take any additional
precautions to minimize the chances that these emboli will be
accidentally dumped back into the bloodstream.
SUMMARY OF THE INVENTION
[0044] The present invention provides a medical device retrieval
system and a method of retrieving a medical device. In accordance
with one embodiment of the invention, a medical device retrieval
system includes a medical device and a retrieval cover. The medical
device comprises a working element carried by a flexible, elongate
shaft. The working element has a proximal profile and the shaft
extends proximally from the working element. The retrieval cover is
slidably carried along the shaft of the medical device. The cover
has a deployed configuration and is capable of being compressed in
a compressed configuration for deployment, yet resiliently
substantially returned to the deployed configuration. The cover in
its deployed configuration has a radially reduced proximal portion.
A distally open distal end defining a distal opening having a
maximum dimension at least as great as the maximum dimension on the
proximal profile of the working element of the medical device, and
an elongate internal recess defined between the proximal portion on
the distal end. The cover in its compressed configuration is
radially compressed inwardly toward the shaft and is distally open,
with the distal end defining the distal-most portion of the cover.
Optimally, the retrieval cover is designed to maintain this general
orientation wherein the distal end of the device is always the
distal-most portion of the cover, regardless of the configuration
of the device.
[0045] This medical device retrieval system may further include a
retrieval sheath which is slidable along the shaft of the medical
device. Such a sheath, if included, is desirably positioned
distally on the cover when the cover is in its deployed
configuration. This retrieval sheath may have an inner diameter
smaller than the outer diameter of the cover in its deployed
configuration. This sheath is adapted to slide distally along the
cover to compress the cover about the medical device.
[0046] In accordance with a further embodiment, the present
invention provides a medical device retrieval system which
comprises a medical device, a retrieval sheath, a deployment stylet
and a retrieval cover. The medical device comprises a working
element carried by a flexible, elongate shaft having an outer
diameter. The working element has a proximal profile and the shaft
extends proximally from the working element. The retrieval sheath
is slidable along the shaft of the medical device and optimally has
a beveled distal end with a distal lumen. The deployment stylet is
slidable along the shaft of the medical device and has a distal
tip. This distal tip tapers distally from a first diameter
approximating the diameter of the distal lumen of the sheath to a
second diameter more closely approximating the outer diameter of
the medical device shaft. This provides a transition between the
shaft of the medical device and the distal end of the retrieval
sheath when the deployment stylet is positioned such that a distal
tip extends distally beyond the distal end of the retrieval sheath.
The retrieval cover is slidable along the shaft of the medical
device and is exchangeable for the stylet along that shaft. The
cover has a deployed configuration and is capable of being
compressed into a compressed configuration for sliding within the
lumen of the retrieval sheath yet resiliently substantially return
to the deployed configuration. In its deployed configuration, the
cover has a radially reduced proximal portion, a distally open
distal end, and an elongate internal recess defined between the
proximal portion and the distal end. The distal end defines a
distal opening having a maximum dimension at least as great as the
maximum dimension of the proximal profile of the working element of
the medical device. In its compressed configuration, the cover is
radially compressed inwardly toward the shaft and is distally open,
with the distal end defining the distal-most portion of the
cover.
[0047] Another embodiment of the invention provides a retractable
medical device system including a medical device, a retrieval cover
and a retrieval sheath. The medical device comprises a working
element carried by a flexible, elongate shaft. The retrieval cover
is slidable along the shaft of the medical device. The cover has a
radially reduced proximal portion, a distally open distal end an
elongate tubular wall extending therebetween and defining a recess.
The working element of the medical device is completely retained
within the recess of the cover such that the tubular wall extends
distally beyond the medical device. The retrieval sheath has a
lumen and is slidable with respect to both the medical device and
the cover. At least a proximal length of the working element of the
medical device and the cover are retained within the lumen of the
retrieval sheath, with the retrieval sheath regularly compressing
the proximal length of the cover such that an intermediate portion
of the wall tightly engages the surface of the medical device. This
will tend to effectively trap any emboli or other materials
retained by the medical device.
[0048] As noted above, the present invention contemplates a method.
One such method involves receiving particulate or other form
material within a channel of a patient's body. As a first step in
performing this method, one provides a medical device having a
working element and a flexible, elongate shaft adapted to follow a
path within the channel; a distally open cover slidable with
respect to the shaft; and a retrieval sheath movable with respect
to the cover on the shaft. The medical device is positioned within
the vessel to engage a wall of the channel and trap the material
within the channel. Either during such positioning or after the
medical device has been positioned and while it is trapping
material within the channel, the cover and the retrieval sheath may
be positioned so they are spaced proximally of the working element
along the shaft of the medical device. The cover is radially
compressed within the lumen of the retrieval sheath such that it
has a distally open distal end and a wall defining a recess, the
wall engaging an inner surface of the retrieval sheath. The cover
is moved distally with respect to the retrieval sheath, thereby
permitting the cover to radially expand into a deployed
configuration wherein the distal end remains distally open and the
enclosure is radially expanded. The cover expands radially
outwardly into the deployed configuration without having to invert
on itself. The cover is then moved distally into engagement with a
surface of the medical device to form therebetween an enclosure.
The retrieval sheath may then be moved distally with respect to the
cover to urge to cover to collapse about the medical device and
tightly engage the surface of the medical device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1A is a schematic side view in accordance with WO
96/01591, showing a vascular trap in a collapsed state for
deployment in a patient's vascular system;
[0050] FIG. 1B is a schematic side view of the medical device of
FIG. 1A in an expanded state for deployment in a patient's vascular
system;
[0051] FIG. 2A is a schematic side view in accordance with WO
96/01591, showing an alternative vascular trap in a collapsed state
within a catheter for deployment;
[0052] FIG. 2B is a schematic side view of the device of FIG. 2A,
showing the device deployed distally of the catheter;
[0053] FIG. 3 is a schematic perspective view in accordance with WO
96/01591 showing a vascular trap and a cover, both of which are
collapsed within a catheter for deployment in a channel in a
patient's body;
[0054] FIG. 4 is a schematic side view of the device of FIG. 3 in a
partially deployed state, wherein the vascular trap has been
deployed, but the cover is still collapsed within the catheter;
[0055] FIG. 5 is a schematic side view of the device of FIG. 3 in a
fully deployed state;
[0056] FIG. 6 illustrates one embodiment of a molding element which
may be used in making a portion of the vascular traps shown in
FIGS. 1-5;
[0057] FIG. 7 is a schematic illustration of a retrieval sheath
catching on a vascular obstruction proximally of the desired distal
deployment site;
[0058] FIG. 8 is a schematic side view of a device in accordance
with the present invention with both the trap and the cover fully
deployed;
[0059] FIG. 9 is a schematic cross sectional view showing the
device of FIG. 8 wherein the trap has been deployed but the cover
has retained within the retrieval sheath;
[0060] FIG. 10 is a schematic illustration showing the invention
deployed within a patient's vessel and having emboli retained
therein;
[0061] FIG. 11 is view similar to FIG. 10, but showing the trap
being retracted into the confines of the cover;
[0062] FIG. 12 is a schematic, partially cut away view of the
device of FIGS. 10 and 11 showing the cover being retracted within
the retrieval sheath;
[0063] FIG. 13 is a schematic partial cross sectional view of a
distal portion of a medical device retrieval system of the
invention utilizing a deployment stylet; and
[0064] FIG. 14 is a schematic side view of a distal length of an
alternative retrieval sheath for use with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0065] FIGS. 8-12 schematically illustrate the operation of one
embodiment of the present invention. FIG. 8 illustrates certain
operative portions of the medical device retrieval system 10 of the
invention in a fully deployed state. As noted above, the retrieval
system of the invention is intended to be used in connection with a
medical device having a working element carried by flexible,
elongate shaft. In these drawings, the medical device is typified
as a vascular trap similar to the vascular trap 250 of FIG. 11, but
omitting the tethers 290. The working element of this medical
device is a basket 12, which may be substantially as outlined above
in connection with the description of the basket 270. The shaft in
this design may simply comprise a guidewire 14. While the
construction and operation of the basket 12 may be substantially
the same as that outline for the baskets shown in FIGS. 1-5, it is
generally preferred that the proximal band 13 of this basket be
attached to the guidewire while the distal band 15 be permitted to
slide along the guidewire. Hence, when the basket 12 is released
from a delivery catheter and the basket is allowed to achieve a
radially expanded configuration, the distal end of the collapsed
device (272 in FIG. 1A) will slide approximately toward the
proximal end (274) of the collapsed device.
[0066] It should be recognized that the medical device can be
varied as desired. For example, the medical device used in
connection with the present retrieval system could instead by a
balloon catheter, wherein the working element would be the balloon
portion of the catheter and the shaft would comprise the body of
the catheter extending proximally of the balloon.
[0067] The other elements of the retrieval system 10 generally
comprise a retrieval sheath 20 and a cover 30. It is to be
understood that these drawings are intended merely for illustrative
purposes and are not drawn to scale. In actual operation, the
retrieval sheath 20 and the shaft 40 of the cover would likely be
much smaller. These elements are simply drawn larger to make the
various components easier to see in the attached illustrations.
[0068] The cover 30 includes a radially expandable body 31 carried
by a shaft 40. The body has a proximal portion 32 which is radially
compressed into close proximity with the shaft 40 and is desirably
attached directly thereto. A tubular wall 34 extends distally from
the proximal portion and terminates in a distally open end 36. The
body 31 defines a recess 38 within which the working element of the
medical device may be retracted, as explained more fully below. The
majority of the length of this recess is defined by the generally
tubular wall 34.
[0069] This radially expandable body 31 can be formed of any
suitable material. As explained more fully below, it is preferred
that this body be capable of being collapsed within the retrieval
sheath 20 for deployment, radially expand into a deployed
configuration, yet be readily collapsed by the retrieval sheath to
tightly engage the working element of the medical device. Any
material which achieves this function may be used.
[0070] In one embodiment (not shown), the body 31 is formed of a
flexible plastic material, which may be reinforced with one or more
flexible metal hoops or the like to bias the tubular plastic member
into a funnel-like configuration.
[0071] The illustrated embodiment is shown as comprising a series
of flexible metal wires. As explained in some detail in
Intemational Publication No. WO 96/01591, such a radially
expandable device may be made rather conveniently utilizing a metal
fabric having strands formed of a material which is both resilient
and which can be heat treated to substantially set a desired shape.
Materials such as elgiloy, hastelloy, incoloy, certain grades of
stainless steel and shape memory alloys. Of these materials, shape
memory alloy such as nitinol are particularly preferred.
[0072] In one useful embodiment, the radially expandable body 31 is
formed using the techniques outlined in WO 96/01591, starting with
a metal fabric comprising both nitinol and platinum. For example,
the fabric may be a generally tubular fabric formed of 48 wires
having a diameter on the order of about 0.0015 inches and a pic
rate of about 80-100 pics per inch. Of the 48 wires used to form
this metal fabric, a relatively small percentage of the wires (e.g.
4-6 wires) may be formed of platinum or some other relatively
radiopaque material to enhance visibility of the device on a
fluoroscope without unduly affecting the resiliency of the fabric.
If so desired, the wires can be coated with a therapeutic agent or
with an antithrombogenic material. For example, the wires may be
coated with heparin or with a known platelet-deactivating drug,
e.g., a 2B-3A antagonist.
[0073] This radially expandable body 31 is carried by a axially
slidable shaft 40. This shaft may take the form of a metallic
hypotube, such as that discussed in connection with the embodiment
of FIGS. 3-5. More preferably, though, the shaft 40 comprises a
flexible plastic material of the type that is commonly used in
forming medical catheters. If friction of this shaft 40 with the
retrieval sheath 20 and/or the shaft 14 of the medical device is
anticipated to present a problem, this shaft 40 of the cover may be
formed of polytetrafluoroethylene or another suitable low-friction
material.
[0074] The radially expandable body 31 may be attached to the shaft
40 in any suitable manner. Presumably, the ends of the wires
defining the body 31 could be simply cast into the plastic defining
the flexible shaft 40. However, the embodiment shown in the
drawings is somewhat easier to make, utilizing a pair of marker
bands 46 and 48 to attach the body to the shaft by clamping the
proximal end about the exterior of the sheath. Forming these clamps
of a radiopaque material will make it easier to track the position
of the cover 30 as it is deployed. In the illustrated embodiment,
the cover comprises an exterior layer and an interior layer of the
metal fabric, much like the basket 270 described above in
connection with FIGS. 1-5. In this configuration, the proximal
marker band 46 may be used to clamp the exterior layer of the metal
fabric to the exterior of the shaft 40 while the distal marker band
48 is used to clamp the interior layer of the fabric to the shaft,
which the shaft 14 of the medical device is received, thereby
permitting the cover 30 to track that shaft for deployment. The
shaft 40 shown in FIGS. 8 and 9 extends distally beyond the distal
marker band 48 such that the distal tip 42 of the shaft is received
within the recess 38 of the cover. Not only will this make
manufacturing easier, but it will reduce the likelihood that any
guidewire or other device passing through the lumen 44 of the shaft
40 will get caught up in the metal fabric defining the radially
expandable body 31.
[0075] The retrieval sheath 20 may simply take the form of a
standard medical catheter, with a tip as described below. This
sheath has a generally tubular wall defining a lumen 24 within
which the shaft 14 of the medical device and the shaft 40 of the
cover may be slidably received. The differences in the diameters of
these three elements 20, 40 and 14 are exaggerated in FIGS. 8 and 9
to illustrate operation of the device. In reality, these diameters
would likely be substantially closer than those shown.
[0076] The distal tip 22 of the retrieval sheath 20 may be beveled
to produce a smoother tip. (The advantage of this tip construction
will be highlighted below in connection with the discussion of
FIGS. 7, 13 and 14.) If so desired, a marker band 26 may be
incorporated into the wall of the retrieval sheath 20 adjacent the
distal tip 22. This will help an operator visualize the relative
position of the retrieval sheath 20, the cover 30 and the basket 12
during operation.
[0077] FIG. 9 is a schematic cross sectional view of the device
illustrated in FIG. 8 prior to deployment of the cover. In
operation, the medical device will typically be put in place first.
As outlined above in connection with FIGS. 1 and 2, the basket 12
may be positioned distally of a particular treatment site and the
treatment device (e.g. a balloon catheter or an atherectomy device)
can be guided over the shaft 14 of the trap to perform the intended
procedure. In the use of the retrieval system of the invention with
such a trap, one would typically deploy the retrieval sheath 20 and
the cover 30 after the basket 12 has been in place for some time
rather than deploying all three elements at substantially the same
time. It should be understood, though, that simultaneous deployment
may be appropriate in other circumstances, such as when a cover 30
and retrieval sheath 20 are used in connection with a Foley
catheter or the like.
[0078] Whereas FIG. 8 illustrates the cover in its deployed
configuration, FIG. 9 illustrates the cover in a compressed
configuration which is suitable for deployment. Even in its
compressed configuration, it can be seen that the body 31 of the
catheter generally includes a radially reduced proximal portion 32,
an elongate tubular wall 34 and a distally open distal end 36 which
defines the distal-most portion of the cover. This is indirect
contrast to the structure shown in FIGS. 3 and 4, which show the
cover 340 of that device in its collapsed state. In this collapsed
state, the cover 340 has a distal segment 352 and a proximal
segment 354, both of which are generally tubular in shape and lie
proximate the exterior surface of the guide wire 310. Once this
cover is deployed as shown in FIG. 5, though, the cover must invert
on itself to position the distal section 352 generally within the
proximal section 354 to define a distal lip 358 of the cover. This
distal lip 358 is merely an intermediate point along the longer,
axially expanded configuration of the device when it is collapsed,
as shown in FIGS. 3 and 4.
[0079] There are a number of advantages of the structure of the
present cover 30 over the mechanically more complex design of FIGS.
3-5. In the cover 340 of FIGS. 3-5, the cover must invert on itself
before it can be used to enclose the basket 320. The resilient
nature of the metal fabric used to form the cover 340 will tend to
resiliently draw the distal hypotube 342 proximally toward the
proximal control hypotube 344 once the constraint of the deployment
catheter C has been removed.
[0080] The walls of the vessel can hinder complete inversion of the
cover 340, though. In particular, if the inner diameter of the
vessel within which the cover is to be deployed is significantly
smaller than the outer diameter of the fully deployed cover, the
cover may take on a sausage-like configuration, with the distal and
proximal segments 352, 354 of the cover expanding into engagement
with the wall of the vessel, but being unable to expand
sufficiently to allow the distal hypotube to invert the distal
segment 352 so that it may be received within the proximal section
354. In such a circumstance, the cover will not define a suitable
recess for receiving the basket 320 therein.
[0081] The design shown in FIGS. 8-12 does not require that the
radially expandable body 31 invert on itself to reach its fully
deployed configuration. Instead, the recess 38 will always remain
in place. Deployment of the body 31 distally beyond the distal tip
22 of the retrieval sheath will simply allow this recess to expand
to a size wherein it may readily receive the working element of the
medical device with which the cover is used.
[0082] While FIGS. 8 and 9 schematically illustrate the structure
of the device and its various elements, FIGS. 10-12 are intended to
schematically illustrate the manner in which the cover 30 may be
used to retrieve a basket 12 which is full of emboli or other
particular material. In FIG. 10, the deployment catheter C
(discussed above in connection with FIGS. 1-5) is shown extending
into the lumen of the vessel and terminating proximally of the
position of the basket 12. The cavity of the basket 12 is filled
with emboli E. If one were to simply pull the guidewire 12
proximally, this will tend to evert the generally umbrella-shaped
basket 12, raising the possibility that the emboli E could be
dumped into the bloodstream of the vessel.
[0083] In FIG. 10, the retrieval sheath 20 is positioned proximally
of the basket 12, leaving a space between the distal tip 22 of the
sheath 20 and the basket 12. In this Figure, the cover 30 is still
within the lumen 24 of the retrieval sheath 20, much as in the
configuration shown in cross section in FIG. 9.
[0084] Once the retrieval sheath, with the cover retained therein,
is properly positioned, the shaft 40 of the cover 30 may be
advanced distally with respect to the sheath 20. This may be
accomplished either by holding the sheath 20 stationary and
advancing the shaft 40 of the cover distally or by holding the
shaft 40 of the cover relatively stationary and withdrawing the
retrieval sheath 20 proximally to expose the readily expandable
body 31 beyond the distal tip 22 of the sheath 20.
[0085] When the body 31 of the cover exits the distal end of the
retrieval sheath 20, it will tend to resiliently substantially
return to the configuration schematically illustrated in FIG. 8.
Unlike the cover 340 of FIGS. 3-5, the body 31 of the present
invention will begin to radially expand into its final shape as
soon as the distal end 36 clears the distal tip 22 of the sheath
20. Accordingly, there is no need to deploy the cover 30 so that
even the proximal marker band 46 is positioned distally of the
distal tip 22 of the retrieval sheath as shown in FIG. 8. Instead,
the proximal portion 32 of the body 31 may remain within the lumen
of the retrieval sheath 20, as suggested in FIG. 11, without
compromising operation of the cover 30.
[0086] FIG. 11 illustrates the device wherein the cover has been
sufficiently deployed to define a recess large enough to receive
the body of the basket 12 therein. To achieve the configuration
shown in FIG. 11, the shaft 14 of the vascular trap is withdrawn
proximally, drawing the basket 12 within the enclosure 38.
[0087] As noted above in connection with FIG. 8, the presently
preferred embodiment of such vascular trap employs a proximal band
13 which attaches a proximal end of the metal fabric defining the
basket directly to the shaft of the guidewire 14 while the distal
connector 15 is allowed to slide along the length of the shaft 14.
Accordingly, when the operator pulls proximally on the guidewire
14, this will tend to elongate the trap and cause it to evert. In
the absence of aspiration or a cover 30, this could present some
difficulties.
[0088] Prior to withdrawing the shaft 14 proximally, the distal end
36 of the cover is desirally brought immediately adjacent the
basket 12. In a preferred embodiment, the distal end 36 of the body
31 of the cover defines a distal opening having a maximum dimension
which is at least as great as the maximum dimension of the proximal
profile of the basket 12, i.e., the maximum dimension of the
proximal projection of the deployed basket. If the vessel is large
enough, this would permit the cover to simply slide around the
basket 12 without significantly stressing the basket and causing it
to collapse in any way. More likely than not, though, there will be
insufficient clearance between the basket 12 and the wall of the
vessel to permit the cover to readily slide between the vessel and
the basket. Accordingly, the distal end of the cover will typically
be brought into engagement with a surface of the basket 12. This
will form between the cover and the basket and enclosure that
includes both the cavity of the basket and the recess 38 of the
cover. This movement of the cover distally into engagement with the
medical device may be achieved either by actually physically moving
the cover distally in an absolute sense, or simply withdrawing the
basket 12 toward the cover which will effectively move the cover
distally with respect to the medical device.
[0089] FIG. 11 illustrates the relative positions of the elements
of the invention if the operator continues to withdraw the
guidewire 14 proximally after the cover initially engages the
surface of the basket 12. The basket has started to evert into a
more oblong shape rather than the umbrella-shape shown in FIG. 10.
Nonetheless, the emboli still are retained within the enclosure
defined by the cover and the basket.
[0090] In one preferred embodiment, the body 31 of the cover is at
least as long as the working element of the medical device which is
to be retrieved therewith. This permits the working element to be
entirely enclosed by the cover during the retrieval process,
enhancing the likelihood of a successful retrieval without
inadvertent dumping of the matter captured by the medical device
back into the patient's body. While the cover can be little longer
than the working element of the medical device, it is anticipated
that the cover may be significantly longer than that working
element. This will permit an operator greater flexibility in using
the device without adding unduly to the cost.
[0091] FIG. 12 schematically illustrates the next stage of the
method of removing the medical device from the patients vascular
system. In this view, the retrieval sheath has been moved distally
with respect to the cover. As suggested above, this may be achieve
either by moving the retrieval sheath distally along the cover or
by withdrawing the cover (and, optimally, the medical device)
proximally while holding the retrieval sheath 20 stationary. Urging
the retrieval sheath distally with respect to the cover urges the
cover to collapse about the medical device received therein. This
causes the cover to tightly engage the surface of the medical
device, helping better encase any particular matter received within
the enclosure and limit the likelihood that it may spill back into
the patient's vascular system. It also presents the device with a
radially reduced profile, making it easier to withdraw the device
from the patient's body without undue trauma.
[0092] Looking at the device in FIG. 12, the system has a
particular configuration which is unique to the present invention.
In this configuration, the working element of the medical device is
completely retained within the recess 38 of the body 31 of the
cover such that the distal end 36 of the cover 30 is positioned
distally beyond the distal end of the working element 12. In FIG.
12, at least a proximal length of the basket 12 and the body 31 of
the cover are retained within the lumen of the retrieval sheath 20.
This retrieval sheath radially compresses the proximal length of
the cover such that an intermediate portion of the generally
tubular wall 34 of the body 31 tightly engages a surface of the
basket 12.
[0093] If so desired, the cover 30 and basket 12 may be further
retracted so that they are both completely enclosed within the
lumen of the retrieval sheath 20 prior to withdrawing the device
from the patient's vessel. This is not necessary for effective
operation of the current device, though, and may be left up to the
physician's choice during the procedure. It should also be noted
that the configuration shown in FIG. 12 may be further collapsed by
withdrawing the basket 12, cover 30 and retrieval sheath 20
proximally into the deployment catheter C, thereby further encasing
the emboli and making it easier to withdraw the device from the
vascular system.
[0094] FIG. 7 illustrates one problem which could be encountered in
deploying a medical device retrieval system 10 of the invention
across a vascular obstruction. The vascular obstruction in FIG. 7
is typified as a stent 4 having a stenotic lesion 6 partially
occluding the lumen thereof, but this is selected merely for
illustration. Much the same problem could also be encountered with
a variety of other vascular obstructions.
[0095] The illustrated deployment sheath 20 has a blunt distal tip
22'. Due to the curvature of the vessel where the stent is located,
the retrieval sheath tends to drift upwardly toward the outside of
the curve rather than easily tracking the shaft 14 of the medical
device through the center of the vessel. This problem becomes even
more pronounced if the retrieval sheath is made stiffer, such as by
incorporating metallic braid into the wall of the sheath, to
improve pushability. In some instances, it can take undue time and
effort to manipulate the distal tip of the retrieval sheath to
clear the obstruction. In addition, use of excess force or movement
of the sheath to clear the obstruction risks displacing the working
element (not shown) of the medical device from the treatment site
where it has been deployed.
[0096] FIGS. 13 and 14 illustrate two proposed solutions to
ameliorate these deployment difficulties. A first solution is
illustrated in FIG. 13 while FIG. 14 illustrates another
improvement which may be used alone or in conjunction with the
device of FIG. 13.
[0097] Turning first to FIG. 13, the retrieval sheath 20 shown
therein includes a deployment stylet 70 slidably received in the
lumen 24 thereof. This stylet has a lumen 75 within which the shaft
14 of the medical device is received, permitting the stylet to
slide along that shaft 15 with the retrieval sheath 20. The stylet
70 is provided with an elongate tubular body 72 and a tapering
distal tip 74. In use, the body 72 of the stylet desirably extends
along the entire length of the retrieval sheath so that the
proximal end of the sheath (not shown) extends proximally beyond
the proximal end of the retrieval sheath so an operator may
selectively control the stylet independently of the guide wire and
of the retrieval sheath.
[0098] The distal tip 74 of the stylet tapers from its proximal end
76 to its distal end 78. At its proximal end, the distal tip has an
outer diameter which approximates the diameter of the lumen 24 of
the retrieval sheath at the distal end 22 thereof. As illustrated,
it is not intended that the stylet 70 completely fill the lumen 24
of the sheath as that would lead to undue friction in moving the
stylet relative to the sheath. The outer diameter of the sheath at
the proximal end 76 of the tip 74 need only be close enough to the
diameter of the distal lumen of the sheath 20 to avoid a sharp,
traumatic change in diameter which would be likely to catch on
vascular obstructions and hinder deployment of the sheath 20 in the
vessel. The transition from the distal tip 74 of the stylet to the
outer diameter of the sheath 20 can be further eased by proving the
distal tip 22 of the sheath 20 with a beveled distal end.
[0099] The distal end 78 of the stylet's distal tip 74 has an outer
diameter which more closely approximates the outer diameter of the
medical device shaft 14. It is not expected that this distal end 78
be infinitely thin and track directly against the surface of the
shaft 14. Again, it is sufficient that the distal end 78 of the
stylet be close enough to the diameter of the shaft 14 of the
medical device to avoid a sharp, traumatic change in diameter which
would be likely to catch on vascular obstructions and hinder
deployment of the sheath 20 in the vessel.
[0100] When the stylet is deployed such that its distal tip 74
extends distally beyond the distal tip 22 of the retrieval sheath,
the stylet provides a transition between the shaft 14 of the
medical device and the distal end of the retrieval sheath 20. This
makes it easier to track the shaft 14 and guide the device into
position across a vascular obstruction. FIG. 13 illustrates the
stylet positioned such that the proximal end 76 of the distal tip
74 is positioned immediately adjacent the distal tip 22 of the
retrieval sheath, but this is not necessary. If the body 72 of the
stylet has a substantially constant diameter over the relevant
length, the stylet can be moved distally relative to the sheath 20
such that the body extends beyond the distal end of the sheath.
This will not case any undue problem as the outer diameter of the
body is desirably substantially the same as the outer diameter of
the proximal end 76 of the distal tip.
[0101] Use of the retrieval sheath 20 with the stylet 70 can be
varied. If so desired, one can use the stylet in each and every
deployment of the retrieval system of the invention. However, as
outlined below, use of the stylet adds an additional step to the
retrieval process and its use may be reserved for those
circumstances where the operator either expects to encounter a
vascular obstruction or has already encountered such an
obstruction.
[0102] In use, the stylet 70 and the cover 30 are exchangeable for
one another, i.e., either the stylet or the cover may track along
the shaft 14 within the lumen 24 of the retrieval sheath, but both
cannot be used at the same time. Instead, one must be removed and
replaced with the other. If the operator anticipates a vascular
obstruction (or he or she wants to avoid exchanging devices twice
if an obstruction is encountered), he or she can initially deploy
the sheath 20 with the stylet. This may be accomplished by
positioning the stylet 70 with respect to the sheath 20 such that
the distal tip 74 of the stylet extends distally beyond the distal
tip 22 of the sheath. Optimally, both the stylet and the sheath are
advanced together along the shaft 14 until the distal tip 22 of the
sheath is in a desired position with respect to the working element
of the medical device. (In most circumstances, this will be at a
location wherein the distal tip of the sheath is near the working
element, but spaced proximally therefrom, as discused above in
connection with FIG. 11.)
[0103] Once the sheath is in position, the stylet 70 may be
exchanged for the cover 30. This may be done in much the same
fashion that catheters are exchanged in a typical balloon
angioplasty procedure or the like. In most circumstances, an
exchange wire will be attached to the proximal end of the shaft 14
of the medical device and the stylet 70 can be retracted proximally
onto the exchange wire. Thereafter, the exchange wire can be
disconnected and the cover may be advanced along the shaft 14
through the lumen 24 of the retrieval sheath. Using the marker band
26 of the retrieval sheath and the marker band 13 of the basket 12
(for example), any final adjustments to the position of the sheath
with respect to the working element of the medical device can be
made prior to deployment of the cover.
[0104] The cover may then be moved distally with respect to the
sheath 20, either by distally advancing the cover or proximally
retracting the sheath. As noted above, this permits the body 31 of
the cover to radially expand into a deployed configuration wherein
the distal end remains distally open and the enclosure is radially
expanded. The cover may then be moved distally with respect to the
working element of the medical device and into engagement with a
surface of the medical device to form therebetween an enclosure.
Optimally (but not necessarily, depending on the configuration of
the medical device and the shape of the cover), the cover is
advanced further with respect to the working element until the
entire working element is effectively received in the recess 38 of
the cover. Thereafter, the retrieval sheath is moved distally with
respect to the cover to urge the cover to collapse about the
working element and tightly engage the surface of the working
element to retain any debris in the enclosure.
[0105] FIG. 14 illustrates another improvement of the sheath 20 of
the invention. In this embodiment, a distal length 21 of the sheath
20 is bent at an angle with respect to the body of the sheath. If a
vascular obstruction is encountered, this distal bend will permit
the operator to clear the obstruction by reorienting the sheath so
that the distal tip 22 thereof is spaced toward the center of the
vessel and away from the obstruction, whereupon the sheath can be
further advanced. An angle of between about 5 and about 30.degree.
is believed to be sufficient for most purposes without unduly
interfering with the proper deployment and retrieval of the cover
30. The length of the distal length 21 can be varied as needed. In
most circumstances, it is envisioned that the distal length 21 will
be 5 cm or less, with a length of 1 cm to 3 cm being most likely.
As noted previously, the sheath 20 of FIG. 14 with its bent distal
length 21 may be used instead of or in conjunction with the stylet
70 shown in FIG. 13.
[0106] While a preferred embodiment of the present invention has
been described, it should be understood that various changes,
adaptations and modifications may be made therein without departing
from the spirit of the invention and the scope of the appended
claims.
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