Note: Descriptions are shown in the official language in which they were submitted.
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FILTER RETRIEVAL CATHETER SYSTEM, AND METHODS
This application claims priority of U.S. Provisional Patent Application No.
60/444,320 filed Jan. 31, 2003. This application is a continuation-in-part of
U.S.
patent application Ser. No. 10/540,778 filed Mar. 3, 2006.
BACKGROUND OF THE INVENTION
1. Technical Background
The present invention generally relates to a catheter system to retrieve a
filter which
has been previously implanted in a body passage for medical treatment of a
patient.
2. Discussion
Many different types of filters may be implanted in various body passages for
medical treatment of a patient. The present invention will be described by
using the
specific example of a vascular filter for implantation in a blood vessel, and
an
example of one particular type of filter retrieval system for retrieving a
vascular
filter. However, it should be understood that the present invention is not
limited to
vascular applications, but rather relates to implantable filters for use in
any
medically suitable type of body passage, for example, the vascular system,
biliary
system or pulmonary system, esophagus, etc.
Implantable filters may be of various types and designs, including for example
permanent or retrievable; they may be made of various types of materials, such
as
metals and/or polymers; and they may have any of numerous designs. Some
implantable filters are resilient, having some degree of "spring"
characteristics. This
resilience may be present for example along a longitudinal axis of the filter,
and/or
for example may allow resilient bending along one or more axes of the filter,
and/or
for example may allow resilient compression of the filter. This latter type of
"compressible" filter may be delivered to a desired site for treatment through
a
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R
catheter system having a passage or lumen containing the filter. When the
filter is
released from the catheter, it thus tends to resilient expand to a larger size
suitable
for the size of the body passage at the desired site for treatment.
Permanent filters are not intended for removal, and retrievable filters are
intended to
be removable for a period of time after being implanted. In other words, a
physician
has a period of time in which to choose whether to remove a retrievable filter
or not.
In the specific case of a vascular filter, it may be desirable to have the
option to
retrieve a filter, for example a filter that has been placed in the inferior
vena cava. It
may also be desirable to retrieve such vascular filters with a catheter-based
retrieval
system, from an access point into an artery, for example. Such a catheter-
based
retrieval system enables the physician to retrieve the filter percutaneously,
without
performing surgery. In some situations, the desired access point may be into
the
jugular artery or the femoral artery.
Regarding the filter itself, it may be desirable to provide a medical
implantable filter
with features(s) for resisting movement of the filter within the body
passageway.
These features for resisting movement of the filter may be for example one or
more
resilient anchors, hooks, or barbs, etc. Such movement resistors may be one-
directional, resisting displacement in one direction and allowing for removal
of the
filter in the other direction.
BACKGROUND OF THE INVENTION
In the example of a vascular filter, the filter may be designed to resist
movement
from the desired site for treatment in a cranial direction, defined as being
opposite a
caudal direction. These types of filters are often resilient, and can be
radially
compressed into a smaller size, and may be removed by a catheter system that
is
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inserted into the femoral artery, has a hook or loop member that passes
through a
passage or lumen through the catheter which catches the filter, and pulls the
filter
into the catheter lumen in the caudal direction. The catheter system and
captured
filter may then be removed from the patient.
It may also be desirable to remove a filter in the cranial direction, by
introducing a
catheter retrieval system through the jugular artery or brachial artery, and
approaching the filter from the cranial direction. However, this approach may
not be
desirable, if the particular filter is designed to resist movement in the
cranial
direction.
The retrieval system of the present invention is capable of retrieving a
filter when
approaching from either direction. In other words, the present catheter-based
retrieval system can be inserted through the femoral artery and approach the
filter
from the caudal direction to retrieve the filter, or through the jugular or
brachial
artery and approach the filter from the cranial direction, to retrieve the
filter. This
versatility is provided for approaching the filter from either direction, but
enables the
movement of the filter during retrieval to be in either direction.
Accordingly, the
filter can be pulled in the direction of movement that the filter does not
resist,
regardless of the direction from which the catheter-based retrieval system
approaches the filter.
One example of a retrieval catheter system according to the present invention
thus
allows a filter to be designed to resist movement in the cranial direction,
while still
permitting retrieval by approaching the filter with a catheter-based retrieval
system
from either the cranial direction or the caudal direction.
In operation of a vascular filter retrieval system, the system may provide for
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"pulling" the filter a slight distance in the caudal direction to retract the
filter
anchors or barbs from engagement with the vessel, before "capturing" the
filter
within the catheter system, and then retrieving the catheter system and
captured filter
from whichever access point was selected, and thus in whichever direction is
desired. This flexibility of approach may provide greater therapeutic options
for
treatment of patients.
Accordingly, a general possible object of the present invention is to provide
filter
retrieval systems for retrieving a previously implanted medical filter, and
methods
for using the retrieval systems.
Another possible object of this invention is to provide an improved filter
retrieval
system capable of retrieving a filter in either a proximal or a distal
direction, as may
be preferred by a physician.
These and other possible objects, features and advantages of the present
invention
will be apparent from and clearly understood through a consideration of the
following detailed description of the preferred embodiment. [0017]Many
catheter
systems are used with a flexible guidewire. The guidewire is often metal, and
is
slidably inserted along the desired body passage. The catheter system is then
advanced over the guidewire by "back-loading" or inserting the proximal end of
the
guidewire into a distal guidewire port leading to a guidewire lumen defined by
the
catheter system. Such a guidewire lumen may extend along the entire length or
only
part of the catheter.
It is desirable to provide a balloon catheter having an optimum combination of
various performance characteristics, which may be selected among: flexibility,
lubricity, pushability, trackability, crossability, low profile, pull
strength,
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inflation/deflation times, inflation pressures, and others. Flexibility may
relate to
bending stiffness of a medical device (balloon catheter and/or stent, for
example) in
a particular region or over its entire length, or may relate to the material
hardness of
the components. Lubricity may refer to reducing friction by using low-friction
materials or coatings. Pushability may relate to the column strength of a
device or
system along a selected path. Trackability may refer to a capability of a
device to
successfully follow a desired path, for example without prolapse. Crossability
may
be clarified by understanding that physicians prefer to reach the desired site
with the
balloon catheter while encountering little or no friction or resistance.
Profile may
refer to a maximum lateral dimension of the balloon catheter, at any point
along its
length.
The balloon catheter of the present invention provides various advantages,
which
may include: pushability, optimized flexibility along the catheter length,
torsional
strength, pull strength, low profile, etc. Some embodiments of the present
invention
may also provide additional benefits, including smooth transitions in
flexibility,
lubricious guidewire lumen, etc.
Structurally, catheters may have a flexible shaft extending between a proximal
end
and a distal end, and define one or more tubular passages or "lumens"
extending
through part or all of the catheter shaft. Such lumens often have one or more
openings, referred to as "ports."
When a lumen is adapted to slidingly receive a guidewire, it is referred to as
a
"guidewire lumen," and it will generally have a proximal and distal "guidewire
port." The distal guidewire port is often at or near the catheter shaft distal
end.
A hub is often affixed to the catheter shaft proximal end. The hub may serve a
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variety of functions, including providing a handle for manipulating the
catheter,
and/or defining proximal port(s) communicating with lumen(s) defined by the
catheter shaft. When the catheter has a guidewire lumen, a proximal guidewire
port
may be located at some point along the sidewall of the catheter shaft, or a
hub may
define the proximal guidewire port.
A guidewire has a flexible wire-like structure extending from a proximal end
to a
distal end. The guidewire will usually be of a size selected to fit into and
slide within
a corresponding guidewire lumen of a catheter.
The terms "tube" and "tubular" are used in their broadest sense, to encompass
any
structure arranged at a radial distance around a longitudinal axis.
Accordingly, the
terms "tube" and "tubular" include any structure that (i) is cylindrical or
not, such as
for example an elliptical or polygonal cross-section, or any other regular or
irregular
cross-section; (ii) has a different or changing cross-section along its
length; (iii) is
arranged around a straight, curving, bent or discontinuous longitudinal axis;
(iv) has
an imperforate surface, or a periodic or other perforate, irregular or gapped
surface
or cross-section; (v) is spaced uniformly or irregularly, including being
spaced
varying radial distances from the longitudinal axis; or (vi) has any desired
combination of length or cross-sectional size.
Any suitable additional material may also be used to make catheters and hubs
as
described, including polymers and other materials suitable for use with
medical
devices.
It is of course possible to build various kinds and designs of catheters
according to
the present invention, by various techniques and of various materials, to
obtain the
desired features. It should be noted that the present invention also relates
to methods
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for making and using medical devices, during or in preparation for medical
treatment of a patient.
These and various other objects, advantages and features of the invention will
become apparent from the following description and claims, when considered in
conjunction with the appended drawings. The invention will be explained in
greater
detail below with reference to the attached drawings of a number of examples
of
embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the course of this description of preferred embodiments, reference will be
made to
the attached drawings, wherein:
FIG. 1 is a perspective view of a catheter-based filter retrieval system,
arranged
according to the principles of the present invention;
FIG. 2 is a partial perspective view of a portion of the filter retrieval
system of FIG.
1, including a shaft opening and snare loop;
FIG. 3 is a partial cross-section view of the distal end of the filter
retrieval system of
FIG. 1;
FIG. 4 is a partial perspective view of some components of the filter
retrieval system
of FIG. 1, including a handle and actuator wheel;
FIG. 5 is a partial perspective view of some components of the filter
retrieval system
of FIG. 1, including an actuator wheel, wire, and shaft tube;
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FIGS. 6A-61 illustrate a first method of using the system of FIG. 1 to
retrieve a
previously implanted filter in a proximal direction;
FIGS. 7A-7J illustrate a second method of using the system of FIG. 1 to
retrieve a
previous implanted filter in a distal direction;
FIG. 8 is a perspective view of a catheter-based filter retrieval system,
showing the
catheter shaft following a curved path; and
FIG. 9 is a transverse cross-sectional view of a catheter-based filter
retrieval system,
showing a guidewire lumen.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiments of the present
invention is
merely illustrative in nature, and as such it does not limit in any way the
present
invention, its application, or uses. Numerous modifications may be made by
those
skilled in the art without departing from the true spirit and scope of the
invention.
One possible arrangement of a filter retrieval system of the present invention
is
shown in the drawings. Filter retrieval system 10 includes a shaft 12, a
retrieval
element 14, and a handle 16 with an actuator 18. Retrieval element 14 may be a
loop
as shown, or may be a snare, hook or any other desired shape or type of
retrieval
device.
The shaft 12 may be catheter-based, and has a proximal and a distal end 20 and
22.
The shaft 12 has an opening 24 in its sidewall 26 positioned a distance from
the
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shaft distal end 22. In addition, the shaft 12 may define a lumen or passage
28 from
its proximal end 20 to its distal end 22, or at least near its distal end 22.
The shaft
preferably has an optimum selection of characteristics, including flexibility,
column
strength or pushability, torque transmission, steerability, etc.
A first and second internal space 30 and 32 are defined inside the shaft 12,
located
immediately proximal and distal from the side opening 24. The opening 24 or
sidehole or slot is preferably spaced from the distal end 22 of the catheter
shaft 12 a
distance longer or slightly longer than the length of the filter to be
retrieved, so that
the first and second internal spaces 30 and 32 are sufficiently large to hold
the filter
inside one of them after the filter has been captured.
The handle 16 is affixed to the shaft 12 near the proximal end 20 of the shaft
12, has
an interface for an actuator 18, and provides a comfortable way to manipulate,
steer,
and direct the retrieval system 10. The actuator 18 is adapted to manipulate
the
retrieval element 14 by selectively moving the retrieval element 14 in
proximal
and/or distal directions. The particular actuator 18 shown in the drawings is
a wheel
having an axle 34 and 36 extending from each side of the wheel. The wheel may
have finger ridges as shown.
The actuator 18 should be coupled with the retrieval element 14, so that
moving
forces applied to the actuator 18 will be transmitted to the retrieval element
14, and
move it in a corresponding fashion. The particular construction for
transmitting such
forces shown in the drawings is a main fiber or wire loop 38, extending from a
first
and second end 40 and 42 of the main wire loop 38, wound around each of the
axles
34 and 36 in opposing directions, through a lumen 28 defined by the shaft 12
to a
position near the distal end 22 of the shaft 12, where the main wire loop 38
has a
180-degree bend.
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A pin 44, or pulley or bent tube or 180-degree lumen or any other suitable
guide is
provided, causing the main wire loop 38 to move around it. The guide may be
provided if the material of the main fiber or wire loop 38 has no substantial
column
strength, or cannot transmit an effective pushing force from the proximal
handle 16
and actuator 18 to the retrieval element 14. This loop 38 (and/or the
retrieval
element 14) may be formed of a wide variety of materials, including organic
fibers,
polymers, and even some metals.
The main wire loop 38 is affixed to the retrieval element 14, so that rotation
of the
wheel 18 in one direction causes the retrieval element 14 to move in the
proximal
direction, while rotation of the wheel 18 in the opposite direction causes the
retrieval
element 14 to move in the distal direction.
The handle 16 and actuator 18 may of course have any preferred design or shape
suitable for accomplishing their desired functions. For example, the handle
may
have a more ergonomic shape, or the actuator may be shaped like a lever, or a
slider,
etc. The retrieval element may have any shape suitable for grasping, snaring,
snagging or catching a corresponding retrieval feature on whatever type of
filter is to
be retrieved. The filter shown in FIGS. 6A-61 and 7A-7J is one example of
numerous filter designs that the filter retrieval systems of the present
invention can
retrieve. The particular filter 46 depicted in the drawings has a retrieval
feature 48 in
the form of a hook at one end, and a series of anchors or barbs 50 for
resisting
movement of the filter 46 within a body passage (which is not shown for
clarity
purposes).
FIGS. 8 and 9 show possible features of the retrieval system, including the
catheter
shaft following a curved path, a guidewire lumen 52 having a proximal and
distal
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guidewire port 54 and 56, and one or more marker bands 58.
In operation generally, the retrieval system may inserted into a body passage
such as
an artery through a percutaneous access point. For example, the access point
may be
into the femoral, jugular, or brachial arteries. The retrieval system is
advanced until
the side opening in the shaft is positioned near a desired point on a
previously
implanted filter. In an initial configuration, the retrieval element is inside
the shaft.
When the system is suitably positioned, the physician may manipulate the
actuator,
so that the retrieval element is moved to protrude from the shaft opening. As
the
actuator is further operated, the retrieval element can grasp or hook or
otherwise
engage a portion of the filter, and then pull the filter in through the
opening into one
of the internal spaces of the catheter shaft. The captured filter and the
retrieval
system may then be removed from the patient. The retrieval system may be
capable
of retrieving a filter in either a proximal or a distal direction as desired.
In particular, when the catheter system is advanced to position the catheter
sidehole
and snare near a corresponding retrieval element on the filter, the snare is
hooked or
attached to the filter retrieval element by manipulating the catheter and
spool. Once
the snare grabs the filter retrieval element, which may be a hook, loop,
catch, barb,
etc., the snare and filter may be pulled in through the catheter sidehole in
either a
proximal or a distal direction depending upon the orientation of the catheter
to the
filter. The catheter and the captured filter may then be removed from the
patient.
To retrieve a filter in the proximal direction, as shown in FIGS. 6A-6B, the
distal
end 22 of the shaft 12 is advanced to a position near the filter 46 until the
sidehole
24 is aligned with the filter retrieval feature 48, which may be for example
one or
more hooks, barbs, loops, etc.
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The wheel 18 is rotated slightly to move the main wire loop 38 inside the
catheter
shaft 12 to expose the retrieval element or snare 14, shown in FIG. 6C.
The catheter shaft is pushed or advanced toward the filter so that the snare
14 is
advanced over the filter retrieval feature 48 or attachment point, shown in
FIG. 6D.
The wheel 18 is again rotated to pull the main wire loop 38 inside the
catheter shaft
12 in the proximal direction, to draw the filter 46 into the catheter shaft 12
until it is
inside the proximal internal space 30, shown in FIGS. 6E-61. The retrieval
system
and captured filter are then removed from the body.
Likewise, to retrieve a filter in the distal direction, as shown in FIGS. 7A-
7C, the
distal end 22 of the shaft 12 is advanced to a position past the filter 46,
until the
sidehole 24 is aligned with the filter retrieval feature 48, which may be for
example
one or more hooks, barbs, loops, etc.
The wheel 18 is rotated slightly to move the main wire loop 38 inside the
catheter
shaft 12 to expose the retrieval element or snare 14, shown in FIG. 7D.
The catheter shaft is pulled or withdrawn in the proximal direction so the
snare 14
moves toward the filter, so that the snare 14 surrounds the filter retrieval
feature 48
or attachment point, shown in FIG. 7E.
The wheel 18 is again rotated to pull the snare 14 in the distal direction, to
draw the
filter 46 into the catheter shaft 12 until it is inside the distal internal
space 32, shown
in FIGS. 7F-7J. The retrieval system and captured filter are then removed from
the
body.
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The components of the retrieval systems of the present invention may be made
of
any suitable material having the desired performance characteristics,
including
biocompatibility, strength, flexibility, etc. For example, in the particular
retrieval
system shown in the drawings, the handle and wheel may be made of metals,
polymers, or even ceramics, while the shaft may be made of any suitable
polymer,
possibly in combination with a metal component such as a hypotube, and the
retrieval element and main wire loop are preferably made of metal or a
filament
material.
The total length of the catheter may be selected as any appropriate length,
which
may be approximately 50-100 centimeters, to allow access to the desired sites
for
treatment from various insertion points.
Numerous arrangements of and modifications to the present invention will be
readily
apparent to those skilled in the art. For example, the portion of the main
wire loop
inside of the catheter shaft that does not have the snare attached to it may
be
contained inside a separate lumen of the catheter. Also, a separate guide wire
lumen
and a distal guidewire port may be provided in the catheter shaft to allow the
retrieval system to be inserted over a guidewire. Also, the distal end of the
catheter
shaft may be pre-curved or shaped, and/or may be steerable by means of a
separate
wire or filament to improve the alignment of the retrieved filter to the
opening of the
catheter shaft. The actuator may be replaced with any suitable mechanism,
including
for example a slider. Also, instead of using a spool, two ends of the main
wire used
to manipulate the snare may simply pass through the handle or hub so that the
physician may operate them individually. Also, the edges of the sidehole in
the
catheter may be flared or shaped to facilitate entry of the filter. Also, the
shaft or
main wire loop may be provided with radiopaque marker bands, which are visible
on
a fluoroscope or X-ray video screen.
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In addition, the retrieval systems of the present invention may be used to
retrieve
any type of implantable medical device that has a suitable retrieval feature,
and is
radially compressible and capturable within the retrieval system.
It should be understood that an unlimited number of configurations for the
present
invention could be realized. The foregoing discussion describes merely
exemplary
embodiments illustrating the principles of the present invention, the scope of
which
is recited in the following claims. Those skilled in the art will readily
recognize from
the description, claims, and drawings that numerous changes and modifications
can
be made without departing from the spirit and scope of the invention.
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