U.S. patent application number 13/569405 was filed with the patent office on 2013-03-21 for electrostatic vascular filters.
The applicant listed for this patent is Rogelio Moncada, M. Bret Schneider. Invention is credited to Rogelio Moncada, M. Bret Schneider.
Application Number | 20130072960 13/569405 |
Document ID | / |
Family ID | 41118307 |
Filed Date | 2013-03-21 |
United States Patent
Application |
20130072960 |
Kind Code |
A1 |
Schneider; M. Bret ; et
al. |
March 21, 2013 |
Electrostatic Vascular Filters
Abstract
An intravascular filter is constructed to electrostatically
capture and retain particles of a targeted type (for example fat or
methacrylate emboli), even if those particles are physically small
enough to slip through the filter in the absence of electrostatic
attraction. Specific types of targeted particles are thereby
captured and retained with improved efficiency, while permitting
free flow of non-targeted particles. This improvement permits
intravascular filters to be constructed with low-resistance, widely
spaced filter elements. Accordingly, more targeted particles are
captured, less thrombosis occurs, less pressure drop occurs across
the filter, and perfusion or blood collection in downstream areas
is maintained.
Inventors: |
Schneider; M. Bret; (Portola
Valley, CA) ; Moncada; Rogelio; (New Orleans,
LA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schneider; M. Bret
Moncada; Rogelio |
Portola Valley
New Orleans |
CA
LA |
US
US |
|
|
Family ID: |
41118307 |
Appl. No.: |
13/569405 |
Filed: |
August 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12383094 |
Mar 18, 2009 |
8246649 |
|
|
13569405 |
|
|
|
|
61037983 |
Mar 19, 2008 |
|
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2230/0093 20130101;
A61F 2250/0001 20130101; A61F 2002/018 20130101; A61F 2/01
20130101; A61F 2230/0006 20130101; A61F 2230/008 20130101; A61F
2/013 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61F 2/01 20060101
A61F002/01 |
Claims
1. A method for filtering embolic material with an electrostatic
charge from a vessel of a subject, the method comprising the steps
of: providing a filter system comprising a first filtration element
configured to carry a stable electrostatic charge; delivering said
filter system to a treatment site within a vessel of a subject;
deploying said filter system by expanding the filter system from a
low-profile insertion configuration to an expanded-profile filter
configuration within the vessel; electrostatically trapping
oppositely charged electrostatic particles in the vessel to the
first filtration element with the electrostatic charge.
2. (canceled)
3. The method according to claim 1 wherein said first filtration
element is delivered to the vessel in a lumen of an elongate
catheter in the low-profile configuration.
4. (canceled)
5. The method of claim 1, wherein the first filtration element
comprises a filtration mesh configured to collapse to prevent the
escape of electrostatically trapped particles during removal of
said filter system from the vessel.
6. The method of claim 5 further comprising, removing the filter
system from the vessel by withdrawing the filter system into a
lumen of an elongate catheter and wherein a purse string is
configured to collapse the first filtration element to a delivery
configuration so as to facilitate the withdrawing of the filter
system into the lumen.
7. The method of claim 1 wherein the first filtration element is
configured to carry a negative electrostatic charge such that
positive charged electrostatic particles may be electrostatically
trapped and removed from the vessel and negative charged
electrostatic particles may be repelled from the first filtration
element to remain in the vessel.
8. The method of claim 1 wherein the first filtration element is
configured to carry a positive electrostatic charge such that
negative charged electrostatic particles may be electrostatically
trapped and removed from the vessel.
9. The method of claim 1 wherein the first filtration element
comprises a filtration mesh having perforations and wherein a
portion of the electrostatically trapped particles are smaller than
the perforations of the filtration mesh.
10. The method of claim 1 wherein the first filtration element is
elongate and configured such that the blood flows parallel to the
filtration element with low resistance when the filter system is
deployed.
11. The method of claim 1, wherein the filter system further
comprises a second filtration element adjacent to the first
filtration element, the second filtration element configured to
carry a stable electrostatic charge opposite the electrostatic
charge of the first filtration element; and the method further
comprising electrostatically trapping oppositely charged
electrostatic particles in the vessel to the second filtration
element with the electrostatic charge.
12. The method of claim 1 further comprising imparting an
electrostatic charge on the first filtration element with a direct
current.
13. The method of claim 12 wherein the direct current is supplied
by a battery.
14. The method of claim 12 wherein the electrostatic charge is
imparted on the first filtration element by coupling an anode or
cathode to the first filtration element.
15. The method of claim 12 wherein the electrostatic charge is
imparted on the first filtration element by coupling a anode or
cathode to the first filtration element and an oppositely
corresponding anode or cathode is coupled to an intravascular
location.
16. A method for filtering electrostatically charged particles from
blood flow in a blood vessel, the method comprising: delivering an
intravascular filter comprising one or more filtration elements to
a treatment site in the blood vessel; deploying the intravascular
filter by expanding the filter from a low-profile insertion
configuration to an expanded-profile filter configuration within
the blood vessel; imparting a stable electrostatic charge on the
one or more filtration elements; maintaining the stable
electrostatic charge on the one or more filtration elements while
the one or more filtration elements are in the blood vessel; and
electrostatically trapping particles in the blood vessel which have
an opposite electrostatic charge to the one or more filtration
elements using the imparted electrostatic charge.
17. The method of claim 16, wherein the one or more filtration
elements comprise elongate filtration elements and wherein the
blood flows parallel to the one or more filtration elements with
low resistance.
18. The method of claim 17, wherein the intravascular filter
comprises at least two elongate filtration elements adjacent to one
another.
19. The method of claim 16, wherein the filtration element
comprises a filtration mesh with pore sizes larger than a targeted
electrostatic particle size.
20. A method for removing positive charged particles from blood
flow in a blood vessel, the method comprising: delivering an
intravascular filter comprising a filtration element to a treatment
site in the blood vessel; imparting a stable negative electrostatic
charge on the filtration element; maintaining the stable negative
electrostatic charge on the filtration element while the filtration
element is in the blood vessel; electrostatically trapping
particles in blood flowing in the blood vessel which have a
positive electrostatic charge to the filtration element using the
imparted negative electrostatic charge; and withdrawing the
intravascular filter from the treatment site so as to remove the
electrostatically trapped particles.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a Divisional of U.S. Pat. No.
12/383,094 filed Mar. 18, 2009 (Allowed), which application claims
the benefit of priority of U.S. Provisional Appln. No. 61/037,983
filed Mar. 19, 2008. The full disclosures, each of which are
incorporated herein by reference in their entirety for all
purposes.
FIELD OF THE INVENTION
[0002] The invention described herein relates to medical devices
and methods of use thereof. More particularly, the invention
relates to a retrievable intravascular filter and methods for
filtering embolic material within a vessel of a subject.
REFERENCES
[0003] Berger, US Patent Application Publication No. US2007/0225644
A1, Embolic Removal for Orthopedic Procedures, Sep. 27, 2007.
[0004] Clubb et al., U.S. Pat. No. 7,220,271 82, Embolic Filters
Having Multiple Layers and Controlled Pore Size.
[0005] McGuckin et al., U.S. Pat. No. 6,623,506, Vein Filter.
[0006] Sutton, U.S. Pat. No. 7,229,462, Vascular Filter System for
Carotid Endarterectomy
[0007] Kimmell, U.S. Pat. No. 3,952,747, Filter and Filter
Insertion Element
[0008] Kimura, U.S. Pat. No. 5,935,303, Electrostatic Filter
[0009] Ye et al., U.S. Pat. No. 6,241,999, Method for Producing
Liposomes with Increased Percent of Compound Encapsulated.
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Nonent M, Hoogeveen Y. The 6-F nitinol
[0011] TrapEase inferior vena cava filter: results of a prospective
multicenter trial. J Vasc Intery Radial. 2001 March;
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[0012] Men'shikova Y A, Evseeva T G, Chekina N A, Peretolchin M V,
Skurkis Y O, Ivanchev S S. Synthesis of Monodisperse Polymethyl
Methacrylate particles in Buffered Solutions under the Action of
Carboxyl-Containing Initiator. Russian Journal of Applied
Chemistry, Vol. 75, No 12, 2002 pp 1993-1998
[0013] A J de Vries, Y J Gu and W van Oeveren. The rationale for
fat filtration during cardiac surgery. Perfusion 2002; 17; 29
[0014] De Vries A J, Gu J Y, Douglas Y L, Post W J, Lip H, Oeveren
W V. Clinical evaluation of a new fat removal filter during cardiac
surgery. European Journal of Cardio-thoracic Surgery. 25 (2004)
261-266
[0015] Ramirez G, Romero A, Garcia-Vallejo J J, Munoz M. Detection
and removal of fat particles from postoperative salvaged blood in
orthopaedic surgery. Transfusion. 2002;42:66-75
[0016] Taviloglu K, Yanar H. Fat embolism syndrome. Surg Today.
2007;37(1):5-8. Epub 2007
[0017] Xiong Y L, Noel C, Moody W G Journal of Food Science:
Textural and Sensory Properties of Low-Fat Beef Sausages with Added
Water and Polysaccharides as Affected by pH and Salt. Journal of
Food Science 64 (3), 550-554
[0018] Peng M, Li D, Chen Y, Zheng Q. TI: Electrostatic-Assembly of
Carbon Nanotubes (CNTs) and Polymer Particles in Water: a Facile
Approach to Improve the Dispersion of CNTs in Thermoplastics.
Macromolecular Rapid Communications. Vol 27, No. 11, p 859-864
2006
[0019] Kiely L J, Olson N F. Estimate of Non-Electrostatic
Interaction Free Energy Parameters for Milk Fat Globules. J. Dairy
Sci. 86:3110-3112 (2003)
[0020] Adrianus J. de Vries A J, Gu Y J, Douglas Y L, Post W J, Lip
H, van Oeveren W. Clinical evaluation of a new fat removal filter
during cardiac surgery European Journal of Cardio-Thoracic Surgery
Volume 25, Issue 2, February 2004, Pages 261-266
[0021] Taviloglu K, Yanar H. Fat Embolism Syndrome. Surgery Today.
2007. 37:5-8
[0022] Steinbeck M. J., Robinson J. M, Karnovsky M. J. Activation
of the neutrophil NADPH-oxidase by free fatty acids requires the
ionized carboxyl group and partitioning into membrane lipid. J
Leukoc Biol. 1991 April; 49(4):360-8
[0023] Mastraneglo A. M., Jeitner T. M., Eaton J. W. Oleic acid
increases cell surface expression and activity of CD 11b on human
neutrophils. J Immunol. 1998 Oct. 15; 161 (8):4268-75
[0024] Cnop M., Hannaert J. C., Pipeleers D. G. Troglitazone does
not protect rat pancreatic beta cells against free fatty
acid-induced cytotoxicity. Biochem Pharmacol. 2002 Apr. 1; 63(7):
1281-5.
[0025] Kamijo A, Kimura K., Sugaya T, Yamanaouchi M, Hase H, Kaneko
T, Hirata Y, Goto A, Fujita T., Omata M. Urinary free fatty acids
bound to albumin aggravate tubulointerstitial damage. Kidney Int.
2002 November; 62(5): 1628-37
[0026] Grotjohan H. P., van der Heijde R. M., Jansen J. R.,
Wagenvoort C. A., Versprille A. A stable model of respiratory
distress by small injections of oleic acid in pigs. Intensive Care
Med. 1996 April; 22(4):336-44
BACKGROUND OF THE INVENTION
Fat and Fat Embolism
[0027] Lipids may be classified as either "anionic" (e.g. most
phospholipids), "cationic" (e.g. milk fat globules (Kiely and Olson
2003)), or "neutral". Human fat tissue is an example of a lipid
which in its living, unperturbed form, is electrically neutral. But
once it is surgically or metabolically disrupted, human fat begins
a breakdown into several lipid fractions, some positive, some
negative, and some neutral. For example, free fatty acids (FFAs)
are highly polarized molecules (de Vries et al 2004). The trans
form free fatty acids (FFAs) carry a negative charge (Steinbeck et
al 1991). FFAs are particularly harmful in the circulation. FFAs
cause vasoconstriction and granulocytes activation through surface
expression and activity of CD11b (Mastraneglo et al 1998). FFAs
have been implicated in b-cell damage in the pancreas (Cnop et al
2002), tubulointerstitial damage in the kidney (Kamijo et al 2002),
and acute respiratory distress syndrome in the lungs (Grotjohan et
al .1996). Fortunately, because a FFA molecule is a highly
polarized structure, filtration as a means to remove FFAs from the
blood stream holds some promise. In fact, extracorporeal, (i.e.,
outside the human body) mechanical blood filtration targeting fat
has been demonstrated in blood from orthopedic patients (Ramirez et
al 2002). Similar extracorporeal mechanical filtration during
cardiac surgery has shown that FFAs are retained by the filter
particularly well, a phenomenon that is thought likely to be
related to the polarity of the FFA molecule (de Vries et al
2004).
[0028] The embolization of fat particles into organs including the
lung and brain is an important cause of medical morbidity,
particularly following orthopedic trauma. When a bone is fractured,
there is usually some fat released into the venous circulation.
These particles are distributed downstream, particularly into the
lung, but in most cases do not cause an obvious medical syndrome.
Following orthopedic surgical procedures, however, the escaped fat
particle load becomes very large, and a fat embolism syndrome may
occur in a third of patients undergoing these procedures. Symptoms
may range from mild respiratory distress with skin and eye
symptoms, to severe pulmonary edema and death (Taviloglu et. al.
2007).
Methacrylate and Methacrylate Embolism
[0029] Methacrylate is frequently used in orthopedic surgery to
affix implants and to remodel lost bone. Methyl methacrylate (MMA)
polymerizes and thereby hardens into polymethyl methacrylate
(PMMA). The polymer PMMA is a lipophilic molecule of varying chain
length, with the molecular formula (C.sub.5O.sub.2H.sub.8)n. It is
Sold under a variety of medical and non-medical trade-names
including the familiar "Plexiglas". The two hydroxyl groups carry a
negative electrostatic propensity, while the hydrogens impart
positive charges. Consequently, the molecule has intrinsic
electrostatic properties which become manifest under various
polymerization and ambient pH conditions. Additionally,
methacrylate molecules may be purposefully made to bear either a
positive or a negative charge by means known in the art. For
example, Peng et al. describe "a facile and organic-solvent-free
method" involving the production of positively charged PMMA by
emulsion polymerization, in which a cationic element such as the
monomer methacryloyloxyethyltrimethylammonium chloride (METAC) is
copolymerized with methacrylate. Likewise, negatively charged PMMA
is produced using anionic comonomer sodium
2-acrylamido-2-methylpropanesulphonate (NaAMPS) (Peng. et al.
2006). Particles of these materials, however, are frequently taken
away from the operative site by nearby veins. When the particles
are brought into the fine capillaries of the lung or other regions
of the body, circulatory blockages and tissue damage may
result.
Intravascular Filter Usage and Design Considerations
[0030] The engineering of vascular filters is complicated by the
need to make the particle-capturing mesh tight enough to capture
the targeted particles, but not so tight so as to impede
circulation, or otherwise cause thrombus formation on the mesh. An
excessively loose mesh (in which the spaces between the filter
elements are too distant) results in failure to capture smaller
emboli. Conversely, a mesh that is too tight (in which filter
elements are too close to one another) increases the resistance to
blood flow, and may trap particles indiscriminately, leading to
early thrombosis and occlusion of paths through the filter.
Electrostatic Filters
[0031] Electrostatic filters are known principally for use in water
filtration, cleaning of fabric, air/allergen filtration, and in
food processing, but have not been adapted to the unique
environment and demands of intravascular use.
[0032] It would be desirable to have a venous filter capable of
capturing small embolic particles, including the most dangerous
fatty acids, without attracting platelets and promoting thrombosis.
It would also be desirable to deploy such a filter via a catheter
prior to a high-embolic-risk procedure; and to be able to retrieve
it at the conclusion of that procedure.
[0033] The invention set forth herein relates to a retrievable
protective mesh which is inserted into a blood vessel which is
deemed at risk for delivering potentially harmful embolic particles
to distal organs. This mesh is deployed via catheter, or by direct
cut-down into the vein, and is of sufficient patency to allow
normal blood cells and small clumps of cellular material through.
In particular, this intravascular filter is constructed to employ
electrostatic forces in a manner that permits adhesive forces to
capture particles of the targeted type (for example fat or
methacrylate emboli), and to retain these particles, even those
which might otherwise be physically small enough to slip through
the filter. Specific types of targeted particles are thereby
captured and retained with improved efficiency, permitting filter
elements to be more widely spaced than would otherwise be
necessary, thereby decreasing both resistance and the propensity
for thrombosis. The device is designed to be retrieved post-op, and
the accumulated debris on the mesh analyzed in the laboratory. The
device provides protection from embolism and stroke resulting from
debris released by sites of tissue trauma. The device provides
protection from embolism and stroke resulting from debris released
by sites of tissue trauma.
BRIEF SUMMARY OF THE INVENTION
[0034] A filter system for removal of embolic particles from a
blood vessel of a subject is disclosed, where the system has a
filtration element deployable within a blood vessel of the subject.
At least a portion of the filtration element is electrically
conductive, and either an anode or a cathode is in electrical
communication with the filtration element. Embolic particles
carrying an electrostatic charge opposite that of said anode or
said cathode are attracted to the filtration element. The embolic
particles may be lipids or methacrylate. The filtration element may
further comprise a mesh, one or more struts, and/or one or more
purse strings. The system may be constructed to entrap emboli
and/or embolic material, some of which may comprise a diameter of
10 microns.
[0035] The filter system may further comprise a delivery
configuration and a deployed configuration whereby said system may
be delivered and deployed in a minimally invasive percutaneous
manner. The system may also be retrieved from the vessel of a
subject in a minimally invasive percutaneous manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1A illustrates the venous systems of the body, which
along with arteries, arterioles, venules and capillaries,
constitute the vascular system.
[0037] FIG. 1B illustrates a plan view of one embodiment according
to the invention in use as it is inserted into the right femoral
vein of a subject, the right femoral vein shown in "see-through"
mode, and a portion of the invention illustrated schematically.
[0038] FIG. 2A illustrates one embodiment according to the
invention in a side view and partial schematic as it is deployed in
a vessel of a subject, the vessel and attendant structures shown in
cross-section.
[0039] FIG. 2B illustrates an alternative embodiment according to
the invention in a side view and partial schematic as it is
deployed in a vessel of a subject, the vessel and attendant
structures shown in cross-section.
[0040] FIG. 2C illustrates yet another embodiment according to the
invention in a side view and partial schematic as it is deployed in
a vessel of a subject, the vessel and attendant structures shown in
cross-section.
[0041] FIG. 3A shows an alternative embodiment according to the
invention in a side view as it is deployed in a vessel of a
subject, the vessel shown in cross-section.
[0042] FIG. 3B shows an alternative embodiment according to the
invention in a side view as it is deployed in a vessel of a
subject, the vessel shown in cross-section.
[0043] FIG. 3C shows an alternative embodiment according to the
invention in a side view as it is deployed in a vessel of a
subject, the vessel shown in cross-section.
[0044] FIG. 4A illustrates an alternative embodiment according to
the invention in a side view during a step of deployment in a
vessel of a subject, the vessel shown in cross-section.
[0045] FIG. 4B illustrates an alternative embodiment according to
the invention in a side view during a step in deployment of the
device in a vessel of a subject, the vessel shown in
cross-section.
[0046] FIG. 4C illustrates an end view of an embodiment according
to the invention during a step in deployment of the device.
[0047] FIG. 4D illustrates an end view of an embodiment according
to the invention during a later step in deployment of the
device.
DETAILED DESCRIPTION OF THE INVENTION
[0048] FIG. 1A illustrates the major anatomical aspects of the
human venous system. Via this natural system, deoxygenated blood is
returned to heart 100 via inferior vena cava 105, and oxygenated
blood via pulmonary veins 102. Below renal veins 110, inferior vena
cava 105 emerges from the convergence of the left and right common
iliac veins 115. Femoral veins 120 emerge upstream (distally) from
the common iliac veins 115, and long saphenous veins 125 also arise
in this region.
[0049] As shown in FIG. 1B, each of the common iliac veins 151
arises from the confluence of the femoral veins 152 and the long
saphenous veins 170. Interventional catheter 155 may be placed into
this system through femoral vein 152, for example through the lumen
of guide catheter 160 which may contain electrically conductive
wires 161. Through the lumen, catheter 155 may advance to, for
example, the common iliac artery, and may deploy filter mechanism
180. Distal end of catheter 155 may be used to deploy and to
retrieve filtration device 180 as will be described in the pages to
follow. Conductive wires 161 within interventional catheter 155 are
in electrical communication with power unit 170.
[0050] FIGS. 2A, 2B and 2C illustrate use of electrostatic charges
imparted upon an electrically conductive filtration mesh in order
to repel platelets and red blood cells, and to attract particles
and other cells and materials bearing a net positive electrostatic
charge. In FIG. 2A, battery 257 has a negative pole connected to
wire 256, which runs through the core of interventional catheter
210, and through struts 206, which create a conductive contact with
perimeter ring 220 and mesh 207. The positive pole of battery 257
has resister 258 and is attached to an internal or external surface
250 of the body of the patient via electrode 255. Endogenous
insulating tissue 251 generally lies between the vein walls 222 and
electrode 255. As a result of this arrangement, a net negative
charge may be imparted upon filter mesh 207. This results in the
trapping of electropositive particles, such as electropositively
polymerized methacrylate 231, but not in the entrapment of
electronegative particles such as platelets and red blood cells.
Struts 206, perimeter ring 220 and mesh 207 may be made of
conductive materials including, for example; stainless steel,
titanium and chromium or nitinol. Blood flow is shown in this
embodiment in direction 213, although the principles apply to
either flow direction. In an alternative embodiment, the opposite
polarity is used, in which the filtration bears a positive charge
and serves to attract negatively-charged particles, for example,
electronegative fat components or methacrylate that has been
prepared with an anionic polymerization compound. Methods are known
in the art for imparting electrostatic charges on plastics, for
example using techniques similar to those described by Peng et al
2006. Positively charged methacrylate may be prepared by emulsion
polymerization, in which cationic element such as monomer
methacryloyloxyethyltrimethylammonium chloride (METAC) is
copolymerized with methacrylate. Alternatively, negatively charged
PMMA may be produced using an anionic comonomer such as sodium
2-acrylamido-2-methylpropanesulphonate (NaAMPS). Such ionic
copolymerization agents are non-toxic, and may alternatively be
used to impart ionic charges on many thermoplastics, rubbery
polymers, or their copolymers, including PMMA, polystyrene,
polyacrylonitrile, and polybutadiene, and others.
[0051] In FIG. 2B, a similar configuration is shown, in which the
positive pole is placed on filtration mesh 274, while the negative
pole is placed upon the body of the guide catheter 265, thereby
trapping electronegative particles 275. Alternatively, negative
electrode 265 may be placed in another intravascular location, such
as upon interventional catheter 271. FIG. 2C illustrates an
embodiment in which filtration elements 287, 288, 289 and 290 are
each imparted with either a negative or a positive charge.
Filtration element 287 and 289 are positive, while filtration
elements 288 and 290 are negative. Maintaining charge on each of
these elements is accomplished by sending positive wire 282 and
negative wire 283, which pass through interventional catheter 286,
on the interior of guide catheter 285, and originate from battery
280, with positive wire 282 receiving current limited by resistor
281.
[0052] FIG. 3A illustrates an embodiment of the present invention
in which the filtration mesh 310 is deployed via guide catheter 326
and interventional catheter 325 from upstream of the targeted
filtration site. Note direction of the blood flow 301. Red blood
cells 302 are able to pass through mesh 319, as seen with red blood
cells 304, while large materials such as methacrylate particles 303
are trapped within the mesh as methacrylate particles 327. The same
principle applies for fat cells, which, like methacrylate; are
larger than the red and white blood cells, and are trapped by a 20
micron or less vessel. Lumen margin 300; most often the endothelium
of the vein in which the device is deployed; is shown with
expansible lumen perimeter ring 305 fitting against lumen margin
300. Filtration mesh 310 is delivered by interventional catheter
325, which passes out from guide catheter 326, and is held in place
by flexible; expansible lumen perimeter ring 305, which is held
orthogonal to the flow of blood 301 by flexible cords 328.
Perimeter ring 305 may be made of materials including; as an
example, polytetrafluoroethylene (PTFE). Cords may be made of
materials including for example PTFE, nylon; and suture materials
including Vicryl. Filtration mesh 310 may have perforations of
approximately 10 to 30 microns in size, so as to allow passage of
endogeneous blood cells and very small clumps, but not of fat
cells, nor of methacrylate particles. Mesh 310 may also be made of
materials including nitinol. Purse string 329 serves to collapse
perimeter ring 305, closing off mesh 310 to prevent escape of
trapped particles as the device is received and removed from
intravascular placement, typically at the end of a surgical
procedure.
[0053] FIG. 3B illustrates an embodiment of the present invention
in which filtration mesh 370 is deployed via guide catheter 376 and
interventional catheter 375 from downstream of the targeted
filtration site; by virtue of semi-rigid struts 377 (instead of
flexible cords as seen in FIG. 2A). Note direction of blood flow
351. Following deployment, filtration mesh 370, fixed upon
expansible lumen perimeter ring 355, is held into an extended
position by semi-rigid struts 377. At the convergence of struts
377, a latched or spring-actuated mechanism may be used to assist
with the deployment and retrieval processes. The closure process
may be facilitated via purse string 379:
[0054] FIG. 3C illustrates an embodiment of the present invention
in which semi-rigid struts 387 are used when mesh 351 is deployed
downstream of blood flow 371, (in a manner similar to that
accomplished with flexible cords in FIG. 3A). Use of semi-rigid
struts 387 can permit greater each of deployment and closure of
perimeter ring 385 and mesh 351, optionally without need for a
purse string.
[0055] FIG. 4A illustrates an embodiment of the present invention
in which the collapsed filtration mesh 410 surrounds the tip of
interventional catheter 425, after being pushed forward from the
interior of guide catheter 426. This embodiment also includes
semi-rigid struts 407. FIG. 4B illustrates the closure and
retrieval of filtration mesh 466 in one embodiment of the present
invention. Purse string 461 may be used to assist with the opening
and collapse of struts 460; which differentially move at their
vertex, which extends from interventional catheter 462. Once
collapsed, the apparatus may be withdrawn through guide catheter
476.
[0056] Alternatively, if the mesh 466, ring 465 and struts 460 are
too large; or too full of filtered debris 457, they may be
retracted through the incision following the removal of guide
catheter 476.
[0057] FIG. 4C illustrates mesh 481 and perimeter ring 480 along an
end view; with trapped methacrylate or fat debris 482. FIG. 40
illustrates the same embodiment after purse string 487 has been
pulled, closing perimeter ring 486, and trapping within mesh 485
debris 488.
[0058] The various embodiments described above are provided by way
of illustration only and should not be construed to limit the
invention. Based on the above discussion and illustrations, those
skilled in the art will readily recognize that various
modifications and changes may be made to the present invention
without strictly following the exemplary embodiments and
applications illustrated and described herein. Such modifications
and changes do not depart from the true spirit and scope of the
present invention; which is set forth in the following claims.
* * * * *