U.S. patent application number 12/463296 was filed with the patent office on 2009-11-05 for embolic filtering method and apparatus.
This patent application is currently assigned to STOUT MEDICAL GROUP, L.P.. Invention is credited to Stephen J. KLESHINSKI, Scott M. RUSSELL.
Application Number | 20090275976 12/463296 |
Document ID | / |
Family ID | 33476857 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090275976 |
Kind Code |
A1 |
KLESHINSKI; Stephen J. ; et
al. |
November 5, 2009 |
EMBOLIC FILTERING METHOD AND APPARATUS
Abstract
The present invention relates generally to a device and method
for preventing the undesired passage of emboli from a venous blood
pool to an arterial blood pool. The invention relates especially to
a device and method for treating certain cardiac defects,
especially patent foramen ovales and other septal defects, through
the use of an embolic filtering device capable of instantaneously
deterring the passage of emboli from the moment of implantation.
The device consists of a frame, and a braided mesh of sufficient
dimensions to prevent passage of emboli through the mesh. The
device is preferably composed of shape memory allow, such as
nitinol, which conforms to the shape and dimension of the defect to
be treated.
Inventors: |
KLESHINSKI; Stephen J.; (San
Jose, CA) ; RUSSELL; Scott M.; (San Jose,
CA) |
Correspondence
Address: |
LEVINE BAGADE HAN LLP
2400 GENG ROAD, SUITE 120
PALO ALTO
CA
94303
US
|
Assignee: |
STOUT MEDICAL GROUP, L.P.
Perkasie
PA
|
Family ID: |
33476857 |
Appl. No.: |
12/463296 |
Filed: |
May 8, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11184069 |
Jul 19, 2005 |
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12463296 |
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10847909 |
May 19, 2004 |
7122043 |
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11184069 |
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60471555 |
May 19, 2003 |
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61B 2017/00601
20130101; A61F 2230/0067 20130101; A61B 17/0057 20130101; A61B
17/12113 20130101; A61B 17/12122 20130101; A61F 2230/0006 20130101;
A61F 2/2445 20130101; A61B 2017/00597 20130101; A61B 2017/00575
20130101; A61F 2002/018 20130101; A61F 2220/0016 20130101; A61F
2250/0039 20130101; A61B 2017/00783 20130101; A61B 2017/00579
20130101; A61F 2/01 20130101; A61B 2017/4233 20130101; A61B
2017/00592 20130101; A61B 17/12168 20130101; A61B 17/12022
20130101; A61B 2017/00632 20130101; A61B 17/12172 20130101; A61F
2/2475 20130101; A61B 2017/00862 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61F 2/01 20060101
A61F002/01 |
Claims
1. A device positionable within a body opening, comprising: a
frame, wherein the frame comprises at least two arms, and further
wherein each of the at least two arms comprise at least one anchor
extending laterally from the arms; and a mesh, wherein the mesh is
coupled to the frame.
2. The device of claim 1, wherein the frame further comprises at
least one base, wherein the at least two arms are coupled to the
base.
3. The device of claim 2, comprising a first base and a second
base, wherein the at least two arms connect the first base to the
second base.
4. The device of claim 1, wherein the at least two arms are
positioned opposite one another and biased apart from another.
5. The device of claim 1, wherein the length of the frame is
elongated when the at least two arms are compressed perpendicularly
to the longitudinal axis of the frame.
6. The device of claim 1, wherein the at least one anchor is
arcuate.
7. The device of claim 1, wherein at least one anchor is
linear.
8. The device of claim 1, wherein at least a portion of the frame
is comprised of a radiopaque material.
9. The device of claim 1, wherein the device is collapsible into a
catheter and capable of expanding to a relaxed state as the device
is released from the catheter.
10. The device of claim 1, wherein the mesh comprises a foam.
11. A device positionable within a body opening, comprising: a
frame comprising a first base, a first arm and a second arm,
wherein the first and second arms are coupled to the first base,
and wherein the first arm comprises a first anchor extending
laterally away from the first base, and wherein the second arm
comprises a second anchor extending laterally away from the first
base, and wherein the first arm is positioned substantially
opposite the second arm, and wherein the first arm and the second
arm are resiliently flexible, wherein the first arm further
comprises a third anchor, and wherein the second arm further
comprises a fourth anchor, and wherein the first anchor and third
anchor are configured to anchor the device to tissue between the
first and third anchors, and wherein the second anchor and the
fourth anchor are configured to anchor the device to tissue between
the second and fourth anchors; and a mesh coupled to the frame.
12. The device of claim 11, wherein the frame is substantially
planar, and wherein the mesh extends out of the plane of the
frame.
13. The device of claim 11, further comprising a second base,
wherein the first arm connects the first base to the second
base.
14. The device of claim 11, wherein the first arm is biased away
from the second arm.
15. The device of claim 11, wherein the mesh comprises a metal.
16. The device of claim 11, wherein the mesh is configured to act
as a scaffold for new tissue growth.
17. The device of claim 11, wherein the mesh comprises a material
configured to promote tissue growth.
18. The device of claim 11, wherein the first anchor and second
anchor are arcuate.
19. The device of claim 11, wherein the first anchor and second
anchor are linear.
20. The device of claim 11, wherein the device is collapsible into
a catheter and capable of expanding to a relaxed state as the
device is released from the catheter, and wherein the length of the
frame is elongated when the first arm and the second arm are
compressed perpendicularly to the longitudinal axis of the frame.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is divisional of U.S. patent application
Ser. No. 11/184,069 filed Jul. 19, 2005 which is a
continuation-in-part of U.S. patent application Ser. No. 10/847,909
filed May 19, 2004, now U.S. Pat. No. 7,122,043 issued Oct. 17,
2006, which is based on and claims priority to U.S. Provisional
Patent Application No. 60/471,555 filed May 19, 2003, the entire
disclosures of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a device and
method for preventing the undesired passage of emboli from a venous
blood pool to an arterial blood pool. The invention relates
especially to a device and method for treating certain cardiac
defects, especially patent foramen ovales and other septal defects
through the use of an embolic filtering device capable of
instantaneously deterring the passage of emboli from the moment of
implantation.
[0004] 2. Description of Related Art
[0005] The fetal circulation is vastly different than the normal
adult circulation. The blood circulating in a fetus is oxygenated
by the placenta, not the developing lungs. Therefore, the fetal
circulation directs only a small percentage of the circulating
blood to the fetal lungs. Most of the circulating blood is shunted
away from the lungs to the peripheral tissues through specialized
vessels and foramens that are open ("patent" during fetal life. In
most people these specialized structures quickly close after birth.
Unfortunately, they sometimes fail to close and create hemodynamic
problems that can be fatal if left untreated.
[0006] A diagram showing the blood circulation of a human fetus is
illustrated in FIG. 1. The umbilical arteries branch off of the
iliac arteries and deliver unoxygenated blood to the placenta. The
fetal blood travels through the capillary bed in the placenta and
transfers carbon dioxide to the maternal blood and takes oxygen and
other nutrients from the maternal blood. The umbilical vein returns
oxygenated blood to the fetus. Most of the oxygenated blood from
the umbilical vein bypasses the developing liver and travels
through a specialized vessel called the ductus venosus to die
inferior vena cava and then into the right atrium. A good portion
of the oxygenated blood from the inferior vena cava is directed
across the right atrium and into the left atrium through a
specialized curtain like opening in the heart called the foramen
ovale. The blood from the left atrium then enters the left
ventricle and then into the aorta where it travels to the head and
other body tissues delivering the needed oxygen and nutrients.
[0007] The small amount of blood entering the right atrium that
does not pass through the foramen ovale, most of which comes from
the superior vena cava, flows into the right ventricle and then
gets pumped into the pulmonary trunk and pulmonary arteries. Some
of this blood is pumped into the developing lungs. However, the
fetal lungs are collapsed which causes a high resistance to blood
flow. Another specialized vessel, called the ductus arteriosus, is
a vessel that connects the high pressure pulmonary artery to the
lower pressure aorta. Therefore, most of the blood in the pulmonary
artery flows into the lower pressure aorta through this specialized
vessel.
[0008] Upon birth, the circulatory system goes through profound
changes. The flow through the umbilical arteries and umbilical vein
stops and consequently the flow through the musculature around the
ductus venosus, constricts and the blood flow through the ductus
venosus stops. The lungs fill with air and the resistance to blood
flow into the lungs drastically decreases. The corresponding
pressure in the right atrium, right ventricle, and pulmonary
arteries also decrease. The decrease in pressure in the right
atrium causes the curtain like opening of the foramen ovale to
close, driving more blood into the right ventricle and then to the
lungs for oxygenation. Over time, the foramen ovale is replaced
with a membrane called the fossa ovalis. Similarly, the decrease in
pressure in the pulmonary arteries reduced the pulmonary arterial
pressure to the same as or slightly less than the pressure in the
aorta, which stops or reverses the flow through the ductus
arteriosus. Once the muscular tissue of the ductus arteriosus is
perfused with well oxygenated blood, the muscle begins to constrict
and close the ductus arteriosus. The ductus arteriosus normally
closes within about one week of life.
[0009] Usually over time, the unique openings of the fetal
circulation become obliterated and a solid mass of tissue forms
where these opening once were. However, in some people the opening
remain. A patent ductus venosus after birth is very rare and almost
always fatal. A patent ductus arteriosus occurs in about 1 out of
every 5000 births. The patent ductus arteriosus once diagnosed is
either medically treated or surgically ligated to close the ductus.
In about one of four people, the foramen ovale does not seal shut,
instead it remains patent. Such defects usually measure 10 mm or
more in diameter and occupy one third or more of the length of the
atrial septum in echocardiographic four chamber sections. Since the
pressure in the left atrium is about two to four mm Hg greater than
the pressure in the right atrium, the curtain like opening usually
remains shut. However, if the pressure in the right atrium
increases, such as upon heavy lifting or while performing a
Valsalva type maneuver, the curtain like fold of tissue opens and
the blood flows from the right atrium to the left atrium.
[0010] Studies have shown that adults with strokes of unknown
origin, i.e., cryptogenic strokes, have about twice the normal rate
of patent foramen ovales than the normal population. Although there
is a correlation between strokes and patent foramen ovales, it is
currently unknown why this correlation exists. It is theorized that
blood clots and plaque that have formed in the peripheral venous
circulation (in the legs for example) break off and travel to the
heart. Normally, the clots and plaque get delivered to the lungs
where it is trapped and usually cause no harm to the patient.
Patients with a patent foramen ovale, however, have a potential
opening that the clots or plaque can pass through the venous
circulation and into the arterial circulation and then into the
brain or other tissues to cause a thromboembolic event like a
stroke. The clots may pass to the arterial side when there is an
increase in the pressure in the right atrium. Then the clots travel
through the left side of the heart, to the aorta, and then to the
brain via the carotid arteries where they cause a stroke and the
associated neurological deficits.
[0011] A number of atrial septal defects (ASD) closure devices have
been developed and investigated in an attempt to develop a
nonsurgical, transvenous method of occlusion of ASD. These include
the Sideris Buttoned device, the Angel Wing Das device, the atrial
septum defect occlusion system (ASDOS) device, the Amplatz Septal
Occluder, the CardioSEAL/StarFlex devices, and the Gore/Helix
devices. Unfortunately, each of these devices have distinct
disadvantages and limitations ranging from the size of the device
delivery sheath, ease of implantation, feasibility, safety and
effectiveness. The Sideris buttoned device is made of a
polyurethane foam occluder with a Teflon coated wire skeleton,
which is positioned within the left atrium, and a polyurethane foam
rhomboid shaped counteroccluder with a Teflon coated wire skeleton,
which is positioned in the right atrium. The major disadvantage
with this device is the lack of a centering mechanism. For this
reason, use of the devices at least two times the size of the
stretched ASD is required. (Sievert H. Koppeler P. Rux S:
Percutaneous closure of 176 interarterial defects in adults with
different occlusion devices-6 years of experience [abstract], J.
Am. Coll. Cardiol 1999, 33:51 9A.) Consequently, closure of defects
may become difficult because the required size may be too large for
the atrial septum to accommodate, or the device may impinge
critical structures. There are also reports that the retrieval of
the Sideris button device after incorrect deployment is difficult.
(See, e.g., Rigby, Michael L., The Era of Transcatheter Closure of
Atrial Septal Defects, Heart; 81:227-228 (1999)).
[0012] The "Angel Wings" device comprises two square frames made of
superelastic Nitinol wire, each square frame having four legs that
are interconnected by flexible islets at the corners. The wire
frames are covered by polyester fibers. There is a conjoint suture
ring of the right and atrial discs, which allow self centering on
deployment. The device is delivered through an 11-13 F Mullins
sheath. The major disadvantage of using this device is the
attendant risk of aortic perforation cause by its sharp eyelet
corners. In fact, the Angel Wings device was withdrawn from further
clinical trials because of this problem. (Syamaxundar Rao, P., M.
D., Summary and Comparison of Atrial Septal Defect Closure Devices,
Current Interventional Cardiology Reports 2000, 2:367-376 (2000)).
The device is also ill-suited for treating fenestrated defects.
[0013] The atrial septal defect occlusion system (ASDOS) prosthesis
(Microvena Corp., White Bear Lake, Minn.) consists of two umbrellas
made of Nitinol and a patch of porous polyurethane attached to the
left and right atrial devices. The device is introduced
transvenously over a long veno-arterial guidewire and through an 11
F venous transeptal sheath. While the device is retrievable in the
event of malpositioning before release of the device, it requires a
complex procedure to implant, and the components are known to have
high incidences of thrombosis. It is also reported that frame
fractures have been detected in 20% of the patients treated with
this device.
[0014] The Amplatzer device is the subject of U.S. Pat. No.
5,944,738 to Amplatzer, et al. This device is a saucer-shaped
device formed from a mesh of fine Nitinol wires with a central
connecting cylinder having a diameter similar to that of the
stretched diameter of the defect. Thrombosis following implantation
of the device is induced by three polyester patches. The device is
delivered through a 6-10 F Mullins sheath. The primary disadvantage
with this device is that it is ill-suited for closing fenestrated
defects. Moreover, the device is a thick, bulky profile which
dramatically increases the chances that the device will interfere
with the heart's operation. Another disadvantage is its known
capacity for incomplete endothelialisation with thrombus
formation.
[0015] The CardioSEAL.RTM. device (NMT Medical, Inc.) is the
subject of U.S. Pat. No. 6,206,907 to Marino, et al. This occlusion
device is comprised of a center section to which stranded wire
elastic shape memory fixation devices are attached. The fixation
devices hold the occlusion devices in place once it is inserted
into an aperture. Attached to the fixation devices are polyvinyl
foam sheets which occlude the aperture. While the CardioSEAL is
deemed to be relative easy to use, it is reported that, of all the
devices, the CardioSEAL device has the highest incidence of arm
fractures, which has raised serious issues concerning its safety.
Moreover, the CardioSEAL device, like the Amplatzer device is
relatively large, and requiring at least a 10 F or 11 F delivery
systems, and an undue amount of hardware within the heart. These
characteristics increase the chance that the device will interfere
with the heart's operation, lend to residual shunting and/or
embolization. The size of the CardioSEAL device also renders it
less suitable for small children.
[0016] The STARflex.RTM. device (NMT Medical, Inc.) is an updated
version of the CardioSEAL device, which includes a self-centering
mechanism consisting of four flexible springs which pass between
the two fabric disks. While this added feature may reduce the
instances of residual shunting, the aforementioned defects and
disadvantages of the CardioSEAL are still a concern.
[0017] In view of these drawbacks and related-risks, the method of
choice to close a patent foramen ovale is still open heart surgery
and ligation of the foramen ovale to close it. Surgery, however, is
obviously associated with the usually risks of general anesthesia,
open heart procedures, infections, etc. Thus, there is a need for a
safe, cost-effective, and easily implantable device and method for
preventing the passage of emboli from an arterial blood pool and a
venous blood pool which is not subject to the defects and
disadvantages of known devices.
SUMMARY OF THE INVENTION
[0018] The present invention is a directed to an embolic filtering
apparatus for treating septal defects, including patent foramen
ovales. In one preferred embodiment particularly suited for
treating patent foramen ovales, the embolic filtering device
comprises an embolic filter, composed of metal, fiber, and/or
polymer, for preventing the passage of emboli through the septal
defect, and a frame which allows the device to be secured within
and or adjacent to the lumen of the septal defect.
[0019] The embolic filter is made by, for example, (1) swaging one
end of a piece of tubular mesh at a first end with a first fastener
(2) pulling the free end of the mesh over the first fastened end so
that it overlaps the first portion; (3) swaging a second, center
section of the tubular section to form a 3-dimensional ball-like
structure having a first diameter portion with a second fastener;
(4) extending the remaining free end of the tubular mesh back over
the 3 dimensional ball-like structure of the first and second
portions of the tubular mesh; and (4) swaging the free end of the
tubular mesh with a third fastener to form an exterior
3-dimensional ball-like structure having a second diameter portion,
within which the 3-dimensional ball-like structure of first
diameter portion is disposed.
[0020] The mesh is removably secured to at least one or more bases
of the frame, and positioned between the arms thereof. In a
preferred embodiment, the bases of the frame and the fasteners
which secure the tubular mesh are collars, having central lumens.
The aforementioned third-fastener is insertable into the lumen of
at least one of the bases of the frame in order to secure the mesh
to the frame. The lumens of the fasteners and bases are aligned
along a common axis in order that the embolic filtering device can
be loaded onto a guide wire.
[0021] In an exemplary embodiment, the frame, preferably composed
of metal, fabric and/or a polymer, includes at least one base and
at least two arms which extend therefrom, between which the mesh is
at least partially disposed. The arms are positioned opposite one
another and, in their resting state, are spaced apart from one
another. When, as in a preferred embodiment, the device is composed
of a shape memory metal, such as nitinol, the device can is be
collapsed into a catheter tube by compressing the arms of the frame
toward one another, causing the length of the device to increase,
and the width to decrease. As the device is released from the
catheter tube, it reverts to its functional, relaxed state. The
embolic filtering device may also be composed of non-shape memory
metals, such as elgiloy, cobalt chromium, and stainless steel, for
example. Each arm includes at least one anchor positioned on the
arms of the frames. The anchors can either be arcuate or linear in
formation, depending on the shape of the patent foramen ovale to be
treated, and are of sufficient rigidity to secure the device within
the lumen of a septal defect.
[0022] To allow for non-invasive visualization of the device within
a subject at least a portion of the frame or mesh is composed of or
coated with a radiopaque material, such as tantalum. The device may
also be treated with thrombin, collagen, hyluron, or a host growth
factor to encourage and facilitate growth of tissue onto the device
so as to further secure the device within the septal defect. The
device can also be coated with an anticoagulant to deter formation
of blood clots on the surface of the device.
[0023] In an exemplary embodiment, the mesh is composed of at least
96 strands of 0.002'' diameter wire braided such that the wires are
situated at an angle of 35.degree relative to the longitudinal axis
of the device. The interstices created by the braided wires are
small enough such as to effectively filter emboli, thereby
preventing emboli from passing through the patent foramen ovate, or
other septal defect.
[0024] In another aspect of the invention, provided is a method of
preventing the passage of emboli between a venous blood pool and an
arterial blood pool by delivering the embolic filtering device to
within, proximate to and/or adjacent to a passage between a venous
blood pool and an arterial blood pool; and securing the device
within, proximate to, and/or adjacent to said passage. The delivery
of the device is preferably delivered by means of a catheter to
within and/or adjacent to the passage between the venous blood pool
and the arterial blood pool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic diagram of the fetal circulation;
[0026] FIG. 2A illustrates a preferred embolic filtering
device;
[0027] FIG. 2B illustrates another preferred embolic filtering
device;
[0028] FIG. 2C illustrates a top view of the embolic filtering
device illustrated in FIG. 2B;
[0029] FIG. 2D illustrates a preferred frame of the embolic
filtering having two bases;
[0030] FIG. 3 illustrates another preferred embolic filtering
device with a frame having one base;
[0031] FIG. 4 illustrates a preferred embolic filtering device and
delivery mechanism;
[0032] FIG. 5A illustrates another preferred embolic filtering
device;
[0033] FIGS. 5B and 5C illustrate a preferred embolic filtering
device within a patent foramen ovale;
[0034] FIGS. 6A and 6B illustrate another preferred embolic filter
device; and
[0035] FIGS. 7A and 7B illustrated another preferred embolic filter
device.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The present invention is directed generally to methods and
apparatus for preventing the passage of emboli between a venous
blood pool and an arterial blood pools using devices for creating a
barrier to the conducting of emboli at a passage between a venous
blood pool and an arterial blood pool. The device is particularly
suitable for treating cardiac defects, such as patent foramen ovale
or other atrium septal defects. In a preferred embodiment,
exemplified at FIG. 2A, provided is a embolic filtering device 10
comprising a frame 12 and an embolic filter 14 comprising a mesh of
stranded fabric, wire, or polymer. FIG. 2D illustrates one
embodiment of frame 12 without embolic filter 14 attached. In this
embodiment, frame 12 consists of a first base 16 and a second base
18. Each end of arms 20 and 22 are connected to first base 16 and
second base 18, such that the lumens of first base 16 and second
base 18 are in line with longitudinal axis 25 of frame 12. Arms 20
and 22 are preferably formed of a shape memory metal, e.g.,
nitinol, and formed such that, in the resting state, they are
spaced apart from one another.
[0037] Referring to FIG. 2A, extending laterally from each of arms
20 and 22 proximate to first base 16 are right anchors 24. Right
anchors 24 can be of any shape or formation suitable for delivering
embolic filtering device 10 to the desired location and securing it
in place. In a preferred embodiment, right anchors 24 are
preferably linear or arcuate, and extend outward from frame 12 and
away from first base 16, in the direction of second base 18, at an
acute angle relative to longitudinal axis 25. The desired length of
right anchors 24 and the position from which they extend from arms
20 and 22 will depend primarily on the size of the passage or
defect to be treated. In any event, the right anchors 24 are of
sufficient length to securely engage tissue within and/or adjacent
to the septal defect. For example, when treating a patent foramen
ovale, right anchors 26 preferably engage tissue within and/or
adjacent to the right-atrial opening of the patent foramen ovale.
Extending arcuately and/or laterally from the portion of arms 20
and 22 proximate second base 18 are left anchors 26. Left anchors
26 can be of any shape or formation suitable for delivering embolic
filtering device 10 to the desired location and securing it in
place; however, it has been found that arcuate or coiled anchors
are most suitable for effectively securing the device within the
area of interest. As with right anchors 24, left anchors 26 are of
sufficient length to securely engage tissue within and/or adjacent
to the septal defect to be treated. For example, when treating a
patent foramen ovale, left anchors 26 preferably engage tissue
within and/or adjacent to the left-atrial opening patent foramen
ovale. In a preferred embodiment, right anchor 24 and left anchor
26 are covered with tantalum coil 28, or other radiopaque material,
to allow for visualization of the position and location of embolic
filtering device 10 after implantation in a subject. First base 16
and second base 18 and, for that matter, any portion of device 10
can likewise be compromised of radiopaque materials to provide even
more visual points of reference in the imagery of embolic filtering
device 10.
[0038] In another embodiment illustrated in FIG. 3, provided is a
frame 12 having first base 16, but without second base 18, and
shortened arms 20 and 22. By eliminating second base 18, the amount
of hardware implanted in the passage to be treated is minimized.
Since, as discussed below, second base 18 resides closest to the
left atrium of the heart when embolic filtering device 10 is used
to treat a patent foramen ovale, eliminating second base 18
minimizes the amount of hardware adjacent to or within the left
atrium, decreasing the chance the operation of the left atrium will
be comprised, and reducing the surface area upon which blood clots
can form.
[0039] Embolic filter 14 is removably coupled to frame 12, and is
preferably comprised of plurality of braided wire strands having a
predetermined relative orientation and interstitial space between
the strands. Those skilled in the art will appreciate that the
number and diameter of the wires used may be varied to achieve the
desired density and stiffness of the fabric, and the known size of
the emboli sought to be filtered. In a preferred embodiment, the
wire mesh consists of at least 96 strands of 0.002'' diameter wire,
situated at an angle of approximate 35.degree. relative to the
longitudinal axis 25. Suitable wire strand materials may be
selected from a group consisting of a cobalt-based low thermal
expansion alloy referred to in the field as "Elgiloy," nickel-based
high temperature high-strength "superalloys" (including nitinol),
nickel-based treatable alloys, a number of different grades of
stainless steel, and polymers, including polyester, nylon,
polytetrafluoroethylene (PTFE), polyurethane,
polyaryletheretherketone (PEEK), and polyglycolic acid (PGA),
polylactide (PLA), polyepsilon-caprolactone, polyethylacrylate
(PEA). Platinum and alloys of platinum can also be co-braided,
co-knitted or co-woven into mesh 14 to assist in determining where
mesh is positioned within the patent foramen ovale. In a preferred
embodiment, the wire strands are made from a shape memory alloy,
NiTi (known as nitinol) which is an approximately stoichiometric
alloy of nickel and titanium and may also include minor amounts of
other metals to achieve desired properties. The frame 12 of device
10, and its components, including base 16, base 18, right arms 20
and left arms 22, are also preferably manufactured from so-called
shape memory alloys. Such alloys tend to have a temperature induced
phase change which will cause the material to have a preferred
configuration which can be fixed by heating the material above a
certain transition temperature to induce a phase change in the
material. When the alloy is cooled, the alloy will "remember" the
shape it was in during the heat treatment and will tend to assume
that configuration, unless constrained from doing so.
[0040] Handling requirements and variations of NiTi alloy
compositions are known in the art. For example, U.S. Pat. No.
5,067,489 (Lind) and U.S. Pat. No. 4,991,602 (Amplatz et al.), the
entire teachings of which are herein incorporated by reference,
discuss the use of shape memory NiTi alloys in guide wires. Such
NiTi alloys are preferred, at least in part, because they are
commercially available and more is known about handling such alloys
than other known shape memory alloys. NiTi alloys are also very
elastic and are said to be "superelastic" or "pseudoelastic." This
elasticity allows device 10 to return to a preset configuration
after deployment from a catheter or other delivery device. The
relaxed configuration is generally defined by the shape of the
fabric when it is deformed to generally conform to the molding
surface of the mold in which it was created. The wire stands are
manufactured by standard braiding processes and equipment.
[0041] Embolic filter 14 of the present invention is preferably in
the shape of a three-dimensional ball or sphere, as exemplified in
FIGS. 2A and 2C. Starting with a tubular piece of braided mesh or
the like, the three-dimensional ball or sphere, as exemplified in
FIG. 2A, is, for example, made by swaging a first end of the mesh
with a first fastener 30, and pushing said first fastener 30
upwards into the lumen of the tubular mesh, to create interior
lobes 29. A center portion of the mesh is then swaged with a second
fastener 32, creating an interior embolic filter portion 34. The
remaining mesh is then extended back over said first fastener 30
and interior embolic filter portion 34, and the second end of the
braided tubular mesh is swaged with a third fastener 36. First
fastener 30, second fastener 32, and interior embolic filter
portion 34 are in effect situated within exterior embolic filter
portion 38. Third fastener 36 is situated outside of said exterior
embolic portion 38. In a preferred embodiment, fasteners 30, 32 and
36 are collars having a central lumen. The lumens of the collars
are substantially aligned along a common longitudinal axis 24, and
dimensioned to receive a guide wire 40. Embolic filter 14 is
preferably secured to frame 12 by inserting third fastener 36 into
the lumen of first base 16 of frame 12. To reduce the chance of
third fastener 36 from disengaging from first base 16, third
fastener 36 and first base 16 can be coupled together, either by a
mechanical locking means such as that created by a press fit, a
melted polymer interlock, or hot melt adhesive, or by plasma
welding. Plasma welding is the preferred coupling method, as it
allows first base 16 to be shorter, since no portal is required on
the base. When coupled to frame 12, embolic filter 14 resides at
least partially between arms 20 and 22, such that the lumens of
fasteners 30, 32, and 36 are substantially aligned with the lumens
of first base 16 and second base 18 (if employing a frame with
second base 18), along longitudinal axis 25. A plug composed of
collagen, fabric, an adhesive, polymer or foam, for example, may be
disposed within the aforementioned sphere to further deter the
passage of embolic through the mesh.
[0042] In another preferred embodiment, illustrated in FIG. 2A,
provided is an embolic filter 14 which, instead of having a
spherical shape as exemplified in FIGS. 2B and 3, has a first end
comprising at least one lobe-like formation and a second end which
tapers inward therefrom. To make this embodiment, a piece of
tubular mesh of suitable length, for example, is swaged at a first
end by a first fastener 30. This first fastened end is then pushed
into the lumen of the tubular mesh to form lobes 29. The second end
of the mesh is then swaged by a second fastener 32. This embodiment
is attached to frame 12 by securing first fastener in the lumen of
base 16, and securing second fastener 32 in the lumen of base 18.
As discussed above, fasteners 30 and 32 are collars having central
lumens. The lumens of the collars are substantially aligned along a
common longitudinal axis, and dimensioned to receive a guide wire
40.
[0043] In another preferred embodiment, illustrated in FIG. 5A,
provided is an embolic filtering device 10, similar to those
embodiments described above, but having right anchors 24 which are
specifically designed to engage the perimeter of the tissue
defining the right-atrial opening 23 of the patent foramen ovate,
as illustrated in FIG. 5B. Contrary to right anchors 24 discussed
in the aforementioned figures, the ends of right anchors 24 of this
embodiment reside against or adjacent to the outside of the tissue
wall defining the patent foramen ovale. Right anchors 24 are,
therefore, preferably of slightly longer dimension and at least
slightly arcuate in shape to facilitate this methodology. The ends
of right anchors 24 in this embodiment, include protective caps 27
at their distal ends. Caps 27 can be composed of rubber, plastic,
or any other suitable material for covering the ends of anchors 24
and 26, and may also comprise radiopaque materials, for example, in
order to allow post-implant visualization of the location and
positioning of anchors 24 after implant.
[0044] It will be recognized by those of ordinary skill that the
manner in mesh 14 can be manufactured in a variety of ways without
departing from the scope of the invention. For example, it will be
recognized that mesh 14 does not necessarily need to be spherical,
or have both an interior and exterior embolic portion as discussed
above. Mesh 14 can be of any shape and dimension suitable to deter
the passage of embolic material between a venous blood pool and an
arterial blood pool, and can include any number of layers, so long
as the interstices between the strands forming mesh 14 are of
sufficient area to filter emboli.
[0045] The design and dimensions of frame 12 can also be
manufactured in a variety of ways without departing from the scope
of the invention. FIGS. 6A and 6b illustrate yet a further
embodiment of the invention, wherein arms 20 and 22 are effectively
decoupled from one another, such that the tissue distension
function of embolic filtering device 10 is provided separately by
each individual legs of the device. This allows embolic filtering
device 10 to be more compact, and to better fill gaps and meet the
contours of the patent foramen ovale. Particularly with respect to
the embodiments shown in FIGS. 6A and 6B, should be recognized that
the size of mesh 14 need not be large, but can cover only arms 20
and 22 and still be effective in treating patent foramen
ovales.
[0046] Device 10 provides distinct advantages and improvements over
known patent-foramen ovale-treatment devices. First, the elasticity
and ball-like structure of mesh 14, enables device 10 to treat a
patent foramen ovales, or other septal defects, of any shape and
dimension with equal effectiveness. This is because mesh 14 is
compressible along its entire length. Thus, it does not matter if
the patent foramen ovale is fenestrated, as the elasticity of mesh
14 will allow it to conform to the substantially exact shape and
dimension of the patent foramen ovale. Mesh 14 can also be annealed
to have a 3-dimensional to help fill any gaps within the patent
foramen ovale space. Thus, the post-implant leakage along the
perimeter of known devices caused by their inability to accommodate
irregular shaped defects is eliminated. Second, device 10 has
substantially less surface compared to known devices, thereby
reducing the risk of dangerous blood clot formation on the exterior
of the device. Third, contrary to known devices which do not
prevent passage of emboli through the defect until tissue growth
onto the device occludes the defect, the interstices between the
stands of braided mesh 14 of the present invention are small enough
to effectively filter emboli as soon as device 10 is implanted.
Thus, device 10 offers immediate protection against the passage of
emboli at the moment of implant.
[0047] The embolic filtering device 10 is particular useful in
preventing the passage of emboli between an venous blood pool and
an arterial blood pool. For purposes of exemplary illustration, the
method of the invention is herein exemplified through discussion of
a method of treating a patent foramen ovale (PFO). However, it
should be recognized that the invention can be used to prevent the
passage of emboli between any septal defect and/or arterial venous
blood pool and arterial blood pool. To deliver the embolic
filtering device 10 of the patent foramen ovale, embolic filtering
device 10 is loaded into a delivery system 41 comprising a catheter
42, exemplified in FIG. 4. In a preferred embodiment, the embolic
filtering device 10 is loaded onto a guide wire 40 by inserting the
guide wire through the lumens of first base 16, the lumens of
fasteners 30, 32, and 36, if employing a frame 12 with second base
18, the lumen of second base 18. A pair of forceps 44, as
exemplified in FIG. 4, or other grasping device, is used to grasp
embolic filtering device 10. In a preferred embodiment, first base
16 has a recess 46 for receiving forceps 44, such that forceps 44
are positioned within recess 46 to more securely grasp embolic
filtering device 10, and to deter embolic filtering device 10 from
detaching from forceps 44. With embolic filtering device 10 secured
by forceps 44 embolic filtering device 10 is pulled into catheter
42. As embolic filtering device 10 is pulled into catheter 42, the
force of the catheter walls against first base 16 of frame 12 will
force side walls 20 and 22, and left anchors 26 and right anchors
24 inward toward one another. Embolic filtering device 10 will
gradually collapse as it is pulled into catheter 42.
[0048] Using catheter 42, embolic filtering device 10 is delivered
to the patent foramen ovale, or other passage between a venous
blood pool or arterial blood pool, to be treated. In particular,
the distal end of catheter 42 is extended through the patent
foramen ovale from the right atrial side to the left atrial side.
With the distal end of catheter 42 positioned in the left atrium
adjacent to the patent foramen ovale, forceps 44 are used to
withdraw embolic filtering device 10 from catheter 42. As embolic
filtering device 10 is withdrawn, embolic filtering device 10 will
gradually expand from its collapsed position and into its memorized
shape and/or in conformance to the shape and dimension of the
patent foramen ovale being treated. With the distal end of catheter
42 positioned in the left atrium, adjacent to the patent foramen
ovale, embolic filtering device 10 is withdrawn from catheter 42,
while catheter 42 is slowly pulled back through the patent foramen
ovale in the direction of the right atrium. Left anchors 26 are
withdrawn first, and as catheter 42 is pulled back, left anchors 26
are caused to securely engage the walls defining the patent foramen
ovale, preferably, the tissue defining the perimeter of the
left-atrial opening 23 of the patent foramen ovale, as shown in
FIG. 5C. As catheter 42 is pulled back further, the engagement of
left anchors 26 onto the tissue defining the perimeter of the
left-atrial opening 23 of arms 20 and 22 will prevent embolic
filter device 10 from being pulled through the patent foramen
ovale, and embolic filter 14 will emerge preferably within the
patent foramen ovale, and will gradually expand apart from one
another in returning to the shape memorized orientation. As arms 20
and 22 expand apart from one another, pressure will be exerted onto
the tissue defining the lumen of the patent foramen ovale, thereby
acting as a tissue distension device. The tissue defining the
patent foramen ovale will naturally press inward against mesh 14,
in effect squeezing the device within the patent foramen ovale. As
catheter 42 is pulled back yet further, right anchors 24 will
emerge and, as they expand to their memorized shape, will also
forcibly engage, for example, the walls defining the patent foramen
ovale, or the perimeter of the tissue defining right atrial opening
31 of the patent foramen ovale. If using the embolic filter device
illustrated in FIG. 5A, for example, right anchors 24 will engage
the tissue defining the outside perimeter defining the right-atrial
opening 31 of the patent-foramen ovale, as illustrated in FIG. 5B.
In its memorized shape, embolic filter 14 should be sized to engage
the walls defining the patent foramen ovale with sufficient force
to prevent emboli from passing between the exterior of the embolic
filter 14 and die walls of defining the patent foramen ovale.
Further, the force created from blood flowing from the right atrium
to the left atrium against right anchors 24 facilitates the
securing of right anchors 24, and helps prevent embolic filtering
device 10 from becoming dislodged from its intended position.
[0049] It will be recognized by those of ordinary skill, that the
device can further be secured in place by adhesives, sutures,
hooks, barbs, or other such means. To enhance recovery subsequent
to implanting embolic filtering device 10 frame 12 and/or mesh 14
can be coated with known drugs suitable for that purpose.
Non-pharmacological methods can also be used to promote healing,
including ultrasound, radiofrequency, radiation, mechanical
vibration, or any other known non-pharmacological healing
method.
[0050] Prior to disengaging embolic filtering device 10 from
forceps 44 and removing catheter 42 from the subject, known
radiological techniques can be employed to insure that embolic
filtering device 10 is properly positioned and secured within the
patent foramen ovale. If the position of embolic filtering device
10 needs to be altered, forceps 44, while still secured to embolic
filtering device 10, can be used to reposition embolic filtering
device 10; otherwise, forceps 44 are disengaged from embolic
filtering device 10, and forceps 44, catheter 42, and guide wire 40
are withdrawn. Should embolic filter device 10 later become
disengaged, disoriented, damaged or otherwise need to be removed,
forceps 44 can be used to easily reposition or recover embolic
filter device 10, as necessary. To facilitate the ease by which
embolic filter device 10 is repositioned or recovered, base 16 is
preferably coated with a suitable material to deter tissue from
covering recess 46.
[0051] From the moment that embolic filtering device 10 is
inserted, emboli are effectively filtered by embolic filtering
device 10. Since blood travels from the direction of the right
atrium to the left atrium, the portion of embolic filter 14 having
a higher density of mesh, e.g., lobes 29 and/or interior embolic
filter portion 34, are positioned on the right atria side to
decrease the chances that emboli will penetrate into the left
atrium. The design of embolic filtering device 10, however, is such
that if emboli pass through the right side of embolic filter 14,
there is still a significant chance that the portion of embolic
filter 14 positioned on the left atrial side will prevent the
emboli from passing into the left atrium.
[0052] Thus, unlike known devices for treating patent foramen ovale
or atrial septal defects, for example, it is not necessary for
thrombi to collect on the embolic filtering device 10 before the
passage of emboli are effectively deterred. However, if total
occlusion of the passage is desired, embolic filtering device 10
the embolic filter 14 can be treated with materials to promote
thrombrosis, tissue in-growth, or adhesions. Embolic filter 14 can
also be treated with anticoagulants to discourage blood clot
formation on the device 10.
[0053] The primary function of frame 12 is to facilitate the
delivery, positioning and securing of the embolic filter 14 within
and/or adjacent to a passage between a venous blood pool and an
arterial blood pool. It should be appreciated, however, that
embolic filter 14 can be employed by itself, without frame 12, by
securing embolic filter 14 by other means, e.g. sutures, hooks,
etc., to deter the passage of emboli through a passage between a
venous blood pool and an arterial blood pool. Further, embolic
filter 14 can be of virtually any shape, spherical, round, oval or
flat, so long as it retains its ability to filter emboli.
[0054] In another aspect of the invention, as exemplified in FIGS.
6A and 6B, provided is an embolic filter device 110 composed of a
mesh 112 and a frame 114, to which mesh 112 is attached. Mesh 112
can be composed of any suitable material, including fabric, metal
(e.g. shape memory metal or non-shape memory metal), or polymer,
and can be of any shape (e.g., round, oval, or flat) or size
suitable for the opening to be treated. Frame 114 can also be
composed of any suitable material. For example, frame 114 can be
composed of fabric, if rigidity is not required to support the
opening to be treated. Alternatively, frame 114 can be composed of
plastic, metal or the like, so as to act as a stent to give support
to the orifice through which the passage of embolic is to be
deterred. Depending on the particular use, mesh 112 and/or frame
114 can be absorbable or non-absorbable. To deter the passage of
emboli from a passage between a venous blood pool and an arterial
blood pool, embolic filtering device 110 is preferably used to
block the passage between a venous blood pool and an arterial blood
pool. Using the example of a patent foramen ovale, embolic
filtering device 100 can be attached to tissue adjacent to the
patent foramen ovale by for example, sutures, barbs, hooks, glue,
or any other suitable attaching means 116 to, in effect, create a
screen covering the right atrial and/or left atrial openings,
and/or within the lumen of the patent foramen ovate. The attaching
means 116 are preferably on frame 114, but can be placed at any
suitable location on embolic filter device 110. Once in place,
embolic filtering device 110 effectively deters the passage of
emboli from the right atrium to the left atrium via the patent
foramen ovate. Embolic filter device may be delivered either
percutaneously, surgically, or via a catheter, depending on the
area to be treated.
[0055] The invention has been described through a preferred
embodiment. However, those of ordinary skill will recognize that
various modifications can be made without departing from the scope
of the invention as defined by the claims.
* * * * *