U.S. patent application number 10/290426 was filed with the patent office on 2003-06-12 for distal protection device with local drug delivery to maintain patency.
This patent application is currently assigned to Microvena Corporation. Invention is credited to Anderson, Kent D., Baden, Jeannine B., Kusleika, Richard S., Pavlovic, Jennifer L., Thill, Gary A., Volk, Chad J..
Application Number | 20030109824 10/290426 |
Document ID | / |
Family ID | 27403979 |
Filed Date | 2003-06-12 |
United States Patent
Application |
20030109824 |
Kind Code |
A1 |
Anderson, Kent D. ; et
al. |
June 12, 2003 |
Distal protection device with local drug delivery to maintain
patency
Abstract
The present invention provides for a drug delivery mechanism for
use with a protection device. The protection device has an
expandable filter. The drug delivery mechanism automatically
delivers a drug to the filter without requiring the intervention of
the operator of the protection device. The drug delivered to the
filter facilitates continued filter patency during the medical
procedure.
Inventors: |
Anderson, Kent D.;
(Champlin, MN) ; Kusleika, Richard S.; (Eden
Prairie, MN) ; Pavlovic, Jennifer L.; (Afton, MN)
; Volk, Chad J.; (West Fargo, ND) ; Thill, Gary
A.; (Vadnais Heights, MN) ; Baden, Jeannine B.;
(Long Lake, MN) |
Correspondence
Address: |
Lawrence M. Nawrocki
NAWROCKI, ROONEY & SIVERTSON, P.A.
Broadway Place East, Suite 401
3433 Broadway Street Northeast
Minneapolis
MN
55413
US
|
Assignee: |
Microvena Corporation
|
Family ID: |
27403979 |
Appl. No.: |
10/290426 |
Filed: |
November 7, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60337664 |
Nov 7, 2001 |
|
|
|
60337936 |
Nov 7, 2001 |
|
|
|
Current U.S.
Class: |
604/104 ;
606/200 |
Current CPC
Class: |
A61F 2230/0008 20130101;
A61F 2230/0067 20130101; A61F 2250/0068 20130101; A61F 2/011
20200501; A61F 2002/018 20130101 |
Class at
Publication: |
604/104 ;
606/200 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A medical device for insertion into the vasculature of a
patient, comprising: a distal member for allowing passage of a
fluid, and a self-activating drug delivery mechanism proximate said
distal member for delivering a drug to said distal member to induce
continued patency to said distal member.
2. The medical device of claim 1, wherein said self-activating drug
delivery mechanism includes a plurality of beads.
3. The medical device of claim 2, wherein said self-activating drug
delivery mechanism is activated by piercing of said beads upon
deployment of said medical device.
4. The medical device of claim 2, wherein said self-activating drug
delivery mechanism is activated by dissolving a coating applied to
said beads.
5. The medical device of claim 1, wherein said distal member is a
filter.
6. The medical device of claim 5, wherein said filter is expandable
about a hostwire.
7. The medical device of claim 6, wherein said self-activating drug
delivery mechanism is a plurality of beads.
8. The medical device of claim 7, wherein said plurality of beads
are carried by said hostwire.
9. The medical device of claim 8, wherein said plurality of beads
are activated by releasing said beads from said hostwire and
impacting said beads against said filter.
10. The medical device of claim 7, wherein said plurality of beads
are positioned on said filter.
11. The medical device of claim 1, wherein said self-activating
drug delivery mechanism is a micro-electro mechanical system
(MEMS).
12. The medical device of claim 11, wherein said MEMS dispenses
said drug at predetermined intervals.
13. The medical device of claim 11, wherein said MEMS is located on
a hostwire extending proximate said distal member of said medical
device.
14. The medical device of claim 13, wherein a second MEMS is
located proximate said distal member of said medical device.
15. The medical device of claim 1, wherein a hostwire on which said
distal member is mounted passes through a lumen.
16. The medical device of claim 15, wherein said self-activating
drug delivery mechanism is located within said lumen.
17. The medical device of claim 16, wherein said lumen houses an
expandable bladder.
18. The medical device of claim 17, wherein said expandable bladder
expands in response to a change in environmental conditions.
19. The medical device according to claim 1, wherein
self-activating drug delivery mechanism is activated by expansion
of an expandable bladder.
20. A vascular device, comprising: a hostwire having a distal
portion, the hostwire interposable in the vasculature of a patient;
a filter expandable outwardly from said distal portion of said
hostwire, said filter normally allowing passage of fluid
therethrough; and a drug eluting bead for facilitating patency of
said filter by releasing a drug upflow of said filter.
21. The vascular device according to claim 20, wherein said drug
eluting bead releases said drug upon impact with said filter.
22. The vascular device according to claim 21, wherein said drug
eluting bead impacts said filter upon expansion of said filter.
23. The vascular device according to claim 20, wherein said drug
eluting bead releases said drug by dissolving a coating
encapsulating said bead.
24. The vascular device according to claim 23, wherein said coating
is dissolved by an activating agent in the blood of a patient.
25. The vascular device according to claim 25, wherein said bead is
porous.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a regular application filed under 35 U.S.C. .sctn.
111(a) claiming priority, under 35 U.S.C. .sctn. 119(e) (1), of
provisional application Serial No. 60/337,664 and application Ser.
No. 60/337,936, both previously filed Nov. 7, 2001 under 35 U.S.C.
.sctn. 111(b).
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to medical devices
for filtering or removing matter from within a vascular system and
the delivery of drugs to maintain continued filter patency. More
specifically, the present invention relates to a protection device
having a drug delivery system for facilitating patency of the
protection device. This device also relates to any other
interventional applications where patency must be maintained. This
includes such apparatus as stents, grafts, vessel liners, and guide
catheters
[0004] 2. Description of Related Art
[0005] A protection device, generally, is an expandable filter
attached to a hostwire. Protection devices are often employed in
interventional cardiology/radiology applications to allow the flow
of fluid, such as blood, while preventing the passage of
particulate matter, such as emboli. Protection devices are often
referred to as distal protection devices where the term "distal"
refers to the positioning of the protection device distal to a
lesion or treatment site relative to flow in the vessel. The filter
portion of existing protection devices may include such items as
braided meshes, woven fabrics, perforated films, a plurality of
crossing wires, electrospun polymers and any other configuration
suitable for filtering.
[0006] The performance of the protection device requires that the
filter maintain patency. Patency is defined as the ability of the
filter to allow the passage of fluid. Patency may refer to a filter
at a specific point in time and/or the amount of time that a filter
is able to maintain non-occlusiveness. When used in a vascular
system, the patency of the filter typically decreases over a period
of time. As the pore size of the filter decreases, the patency will
decrease relative to that for a greater pore size. For example, in
some filters when the maximum pore size is 100 um there may be
pores ranging in size from 20 um or less. Such a fine pore size may
cause a filter to become occluded by debris. Pores below a crucial
pore size may also become occluded by formation of an impermeable
fibrous sheet that may close off flow through the pore.
[0007] The current art utilizes three different mechanisms for
facilitating patency. A mechanism facilitates patency where the
mechanism allows greater flow-through, when compared to the
performance of a similar filter without the mechanism.
[0008] The first mechanism used in the current art involves the
pre-application of coatings on the filter used to prevent blood
clotting. Such coatings include anti-coagulants,
anti-thrombogenics, anti-platelets or other such drugs. One typical
drug of this nature is heparin. Even with such coatings the patency
of the filter is limited because the drug coating is eventually
overcome by clotting forces in the blood. Such a mechanism results
in the patency beginning to decrease as soon as the coating
contacts the clotting agents of the blood, and it is only a matter
of time before filter patency is reduced or eliminated by the
clotting agents.
[0009] Two other mechanisms in the prior art used to provide for
increased filter patency include dipping the filter in an
anti-coagulant such as heparin solution, or a systemic use of drugs
such as a IIb/IIIa inhibitor. Even with dipping in heparin, the
patency of the filter will deteriorate over a relatively short
period of time. Problems with systemic use of drugs may manifest
themselves as excessive patient bleeding.
SUMMARY OF THE INVENTION
[0010] The present invention is a protection device with a local
drug delivery system. The drug delivery system delivers a drug for
increasing filter patency. The protection device includes a
hostwire to which an expandable filter is mounted, and an
embodiment of an improved drug delivery mechanism for facilitating
filter patency is described herein.
[0011] Local drug infusion helps to maintain patency of the filter
while blood is flowing through the filter. Local drug infusion
provides the effects of the drug in a local concentration where
needed, to maintain filter patency while minimizing the possible
side effects (i.e. excessive bleeding) that the drug could cause if
used systemically. Generally, the drug is delivered upstream of the
filter, proximate the filter, and allowed to flow distally, through
the filter with the blood.
[0012] A first embodiment of the present invention is a drug
delivery mechanism comprising a micro-electro mechanical system
(MEMS) on or in a guide coil. The guide coil is wound about the
hostwire either proximal or distal to the filter or both. The MEMS
is positioned near a first end of the guide coil. The MEMS is able
to automatically advance toward the second end of the guide coil by
ratcheting a predetermined distance along the guide coil. The guide
coil may be a shape memory tubular body containing a drug. As the
MEMS ratchets along a length of the coil, the drug is released from
the guide coil. The drug is then delivered to the filter so as to
induce continued filter patency.
[0013] Another embodiment of the present invention utilizes a MEMS
on a guide wherein packets or beads containing a drug are on the
surface of the guide. As the MEMS ratchets along the surface of the
guide, the packets or beads are pierced, thus causing the release
of the drug.
[0014] Still another embodiment of the present invention utilizes a
drug delivery system comprising drug eluting beads. The beads may
be located on the hostwire, within the filter, electrospun to the
filter, distal to the filter and/or proximal to the filter or a
combination thereof. The beads are solid forms of variable shape
that allow a drug to be harbored on or within the bead such as in a
crevice, pore, surface, underneath or within a coating, dissolved
into the bulk of the bead, or any other such means of harboring a
drug. The beads may release the drug on deployment of the
protection device or under predetermined environmental or
biological conditions that induce the release of the drug. The drug
may be released such as by piercing of the beads, dissolving of a
coating on the beads, or any other suitable method of activating
the delivery of a drug. The beads may be activated by piercing
where the beads are released from the hostwire and allowed to
impact the filter causing the beads to be pierced. The drug would
then be released on the filter so as to automatically induce
increased filter patency without physician or operator
intervention. The beads may also have a coating or a shape or form
that regulates or controls the release of the drug and deliver the
drug to the filter such as by a stimuli sensitive polymers or other
such coatings.
[0015] Another embodiment of the present invention comprises a
hydrogel or a gel conjugate that is used to coat the filter and/or
hostwire. The gel acts as a drug delivery system wherein the gel
may be activated by environmental or biological agents or variables
such as ph, temperature, pressure differential, precursors to
fibrin formation, and the like.
[0016] Another embodiment of the present invention has a drug
delivery mechanism received within a lumen of a tubular member for
providing local drug infusion such as through a plurality of weep
holes at a distal portion of the tubular member. An expandable
bladder is located within the hollow portion. The bladder expands
upon the occurrence of a predetermined environmental condition such
as temperature or pressure differential or inflation with a
syringe. The drug occupies the lumen with the tubular member. As
the bladder expands the drug is released through weep holes through
a wall defining the tubular member and delivered to the filter.
[0017] The present invention thereby provides for a local drug
delivery mechanism for providing a drug to a protection device such
as a filter for inducing and facilitating filter patency frequently
without requiring interaction from a physician or operator.
DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a side view of a protection device with a
micro-electro mechanical system for providing drug delivery;
[0019] FIG. 2 is a side view of a protection device with a
plurality of electro mechanical systems for providing drug
delivery;
[0020] FIG. 3 is a magnified side view of an electro mechanical
system and guide member;
[0021] FIG. 4 is a side view of a protection device with drug
eluting beads on the hostwire;
[0022] FIG. 5 is a side view of a protection device with drug
eluting beads spun about the expandable filter;
[0023] FIG. 6 is a side view of a protection device with drug
eluting beads positioned within the expandable filter;
[0024] FIG. 7 is a side view of a protection device having a drug
coating;
[0025] FIG. 8 is side view of a protection device with a hollowed
portion with an expandable bladder for drug delivery;
[0026] FIG. 9 is a side view of a protection device with a fluted
hollow portion;
[0027] FIG. 10 is a side view of a protection device having
adjacent lumens for drug delivery; and
[0028] FIG. 11 is a side view of a protection device having coaxial
lumens for drug delivery.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0029] FIG. 1 illustrates a first embodiment of a protection device
10 with a drug delivery mechanism 15 for automatically delivering a
drug without operator or physician input. The protection device 10
is shown having a filter 12 that can be expanded or collapsed about
a hostwire 14. The drug delivery mechanism 15 includes a coiled
tube 32 helically wound with respect to an axis of elongation
defined by the hostwire 14. Also shown, is a proximal marker band
16 and a distal marker band 17.
[0030] FIG. 1 depicts only the distal portion 13 of the hostwire
14, wherein the term `distal` refers to the downstream end of the
hostwire 14 with respect to flow in the body vessel, and the term
`proximal` refers to the upstream end with respect to flow in the
vessel.
[0031] Use of the protection device 10 includes advancing the
protection device 10 within a lumen and expanding the protection
device to engage a wall of the lumen. Once expanded, the filter 12
is able to filter fluid flowing through the lumen so as to prevent
particulate matter from passing distal to the filter 12. Most
commonly, the protection device 10 is used to filter particulate
matter entrained in blood such as in a blood vessel of a patient's
vascular system.
[0032] The drug delivery mechanism 15 is configured to deliver the
drug to the device 10 such as by leaching or metered methods that
occur automatically without physician input once the protection
device 10 and/or filter 12 is deployed. When used in the vascular
system, the filter 12 may become at least partially occluded as a
result of blood coagulation and/or clotting. Upon delivery of the
drug to the protection device 10 by the drug delivery mechanism 15,
the drug is able to induce or facilitate continued filter
patency.
[0033] The drug delivery system embodied in FIG. 1 is a
micro-electro mechanical device (MEMS) 30. The MEMS 30 is
positioned proximal the filter 12. The MEMS 30 is positioned on a
guide 32 such as a coiled tube 32. The guide 32 is positioned about
an axis of elongation defined by the hostwire 14. The MEMS 30 is
able to ratchet along the length of the guide 32. The drug is
dispensed and delivered by the MEMS 30 as the MEMS 30 advances at
predetermined intervals along the length of the guide 32. It is
contemplated that the MEMS 30 begin at or near a first end of a
corresponding guide 32 and ratchet in the direction of a second end
of the corresponding guide 32. Alternatively, the guide could be
straight wire or tube running parallel to the hostwire, or could be
the hostwire itself.
[0034] FIG. 2 illustrates a plurality of MEMS 30 utilized as a drug
delivery mechanism 15. A first MEMS 30 may be positioned proximal
to the filter 12 and a second MEMS 30 may be positioned distal to
the filter 12. As illustrated, each MEMS 30 is positioned on a
guide 32 such as a coiled tube 32. Each MEMS 30 is able to ratchet
along the length of the guide 32. The drug is dispensed and
delivered by each MEMS 30 at predetermined intervals.
[0035] It is further contemplated that the drug delivery mechanism
15 may, instead, comprise only a single MEMS 30 and guide 32 such
that the guide 32 and MEMS 30 are positioned distal to the filter
12.
[0036] FIG. 3 illustrates a magnified view of a MEMS and coil drug
delivery system 15. The function of the drug delivery system 15 is
to deliver a drug to the filter to facilitate patency of the filter
12. The drug is released by the movement of the MEMS 30 along the
length of the guide 32. For example, the drug may be located within
a lumen 52 or other such compartment within the guide 32. As the
MEMS 30 ratchets along the length of the guide 32 from a first end
54 toward a second end 56, the drug is forced or induced out the
second end 56 of the guide 32 and released into the blood stream or
onto the protection device 10 and/or filter 12. It is beneficial,
but not necessary, that the second end 56 of the guide 32 be the
end nearest the filter 12 for greatest benefit toward facilitating
filter patency.
[0037] The guide 32 may be a coil made of a shape memory material
such as an alloy or from a drug-loaded shape-memory polymer
material. The MEMS 30 may be positioned over the guide 32 or marker
band 16 or hostwire 14, and may have a shape such as a donut shape
that slides along the delivery guide 32.
[0038] Alternatively, the coiled tube 32 could be made of a shape
memory polymer and drug loaded such that the drug is released upon
a reaction to pressure, temperature, flow characteristics such that
the drug may be released from a storage portion 52 within the tube
without the use of the MEMS.
[0039] Another method for drug delivery using the MEMS 30 and guide
32 utilizes drug packets and/or beads 50. For example, packets of
the drug may be located on the surface 58 of the guide 32. As the
MEMS 30 advances from the first end 54 toward the second end 56 of
the guide 32, over the packets 50, the packets 50 are pierced or
broken causing the packets to dispense or release the drug. For
this drug delivery system 15 it is beneficial, but not necessary,
that the first end 54 of the guide 32 be nearest the filter 12 with
respect to the second end 56. The reason being that the drug is
released after the MEMS 30 ratchets over the packet 50.
[0040] The drug delivery system comprising the MEMS 30 and guide 32
may be positioned proximate or adjacent to the filter 12. The drug
may be released or delivered directly onto the filter 12, marker
band 16, and/or hostwire 14. Alternatively, the drug may be
released or delivered into the bloodstream of a patient and allowed
or directed to flow to the filter 12.
[0041] The initiation of the drug delivery system may occur upon
deployment of the protection device 10. Prior to deployment of the
protection device 10, the filter 12 is collapsed toward the
hostwire 14. In this collapsed configuration, the coil 32 may be
deformed or maintained in a predetermined position on the guide 32
so as to prevent the MEMS 30 from advancing. Once the filter 12 is
expanded, the coil 32 can resume its preformed state that allows
the MEMS 30 to become self-activated and begin dispensing the drugs
for inducing continued patency of the filter 12. Self-activation of
the drug delivery mechanism may occur by any such method wherein
deployment of the filter 12 functions to remove any restriction on
the MEMS 30 from advancing along the guide 32.
[0042] The drug released by the drug delivery mechanism 15 may be
any such drug that prevents clotting of the blood or otherwise
induces or facilitates continued filter patency, such as heparin,
Integrilin, Aggrastat, or fibrinolytic drugs Such drugs may react
with blood platelets, blood clotting agents, precursors to the
formation of blood clots, and any other agents having a role in the
formation of blood clots, coagulation, and reversal of same.
[0043] The drug may be dispensed at predetermined intervals by the
MEMS 30 where the MEMS 30 ratchets a predetermined length along the
guide 32 at predetermined time intervals resulting in the
dispensing of the drug at periodic intervals.
[0044] A hydrogel, or other leachable coating laden with a drug can
be delivered and/or applied to the filter 12, marker bands 16,
and/or the hostwire 14 proximal to the filter 12. This can also be
applied to the inside or outside diameter of a guide catheter used
to deliver the protection device 10 to a location within a
patient's vascular system, for example. Some drug methods common to
those of ordinary skill in the art include pe-dipping with albumin,
heparin or calcium channel blockers. Hydrogels in combination with
drugs can be used alone or in combination with MEMS. The methods
for making a MEMS 30 as described herein are common to those of
ordinary skill in the art as is the use of various drugs that may
be delivered by the MEMS 30 to facilitate patency of the filter 12
and protection device 10.
[0045] The MEMS 30 may have any shape, such as a short-tubular or
donut shape in the preferred embodiment. Any shape may be used that
allows the MEMS 30 to advance along the guide 32 and release drugs
for continued patency of the filter 12. The guide 32 may likewise
have any shape that allows the MEMS 30 to ratchet along the guide
32 so as to provide a drug delivery mechanism 15 to the protection
device 10.
[0046] FIGS. 4-6 illustrate yet another embodiment of the present
invention. As in FIGS. 1-3, a protection device 10 is shown having
an expandable filter 12 attached proximate the distal end of a
hostwire 14. The filter 12 has proximal and distal marker bands 16,
17 on respective sides. The drug delivery mechanism 15 in this
embodiment is a polymer containing structure illustrated in the
figures as drug eluting beads 50. It will be understood, however,
that structures shaped other than as "beads" would be acceptable.
The beads 50 which are shown may be positioned on the hostwire 14
as shown in FIG. 4. Fibers attached to the filter 12 as in FIG. 5,
can have the drug mixed with a polymer. FIG. 6 illustrates a
multiplicity of beads received within a capture space of filter 12.
These examples are illustrative, however, and not limiting as to
the use of drug eluting structures for delivery of a drug to induce
continued patency within a filter 12. Each embodiment illustrated
is discussed separately below.
[0047] FIG. 4 shows an alternative drug delivery apparatus
comprising a hostwire 14 extending through a filter 12, and drug
eluting beads 50 mounted on the hostwire 14. The drug eluting beads
50 may be pierced during deployment resulting in release of the
drug. Alternatively, the drug could be permitted to leach out of
the beads or other polymer containing structure. Piercing of the
drug eluting beads 50, when piercing is utilized, may occur upon
deployment of the filter 12 to the expanded configuration. For
example, the drug eluting beads 50 may be affixed to the hostwire
14 such that when the filter 12 is deployed, the beads 50 will be
pierced by the wires of the filter 12. The beads 50 may
alternatively be pierced where, upon deployment, the beads 50 are
released from the hostwire 14 and allowed to flow, project, or
travel into the filter 12. As the beads 50 impact strands forming
the filter 12, the beads 50 may become pierced by the filter
strands, thus causing the release of the drug for continued filter
12 patency.
[0048] FIG. 5 illustrates the drug eluting beads 50 attached to
strands of the filter 12. The beads 50 may be formed by spinning
polymer strands onto the filter 12 and then post processing the
strands to form beads. Such beads can be formed on the filter or
into the filter. Such beads 50 may be a polymer material intermixed
or absorbed or filled with the drug such that instead of creating a
polymer strand during the forming process, they create a polymer
bead containing the drug for facilitating patency of the filter 12.
Alternatively, the fibers can have the drug mixed immediately with
the polymer.
[0049] FIG. 6 illustrates drug eluting beads 50 positioned within a
capture space of the filter 12. The drug eluting beads 50 would
have a diameter greater than the filter pores so that the beads 50
are maintained within the filter 12.
[0050] The beads 50 are self-activating such that the drug may be
delivered during deployment of the protection device 10 or filter
12. The initiation of the drug release may be activated either by
piercing of the beads 50 or by interaction of the beads 50 and/or
drug with the environment in which the protection device 10 is
deployed, such as agents in blood that may initiate activation of
the drug or the release of the drug, such as by the drug leaching
out of the beads 50.
[0051] The drug eluting beads 50 may be composed of a polymer
material. The drug may be contained within the beads 50 or coated
about the surface of the beads 50 or within pores within the beads,
dissolved in the beads, or a combination thereof. The drug eluting
beads 50 may have a coating thereon, such that the drug is eluted
only after the coating is pierced or activated by leaching out of
the beads 50. Thus, a self-activating coating may be used to
prevent release of the drug until intended activation of the drug
delivery mechanism such as by an activating agent found in blood.
The coating may further be dissolved by an activating agent in the
blood such as platelets or other precursors to coagulation. The
drug delivery method using beads 50 may include immediate drug
delivery once the device is deployed, or timed release of the drug
continuing over a 30 to 60 minute, or longer, time period, or a
variable release time depending on the material and
configuration.
[0052] The beads 50 may be porous or non-porous, and take on many
shapes such as that of a rod, sphere, oval, and the like. Further,
the beads 50 may be located on the coil or guide 32 such as for use
with an MEMS 30, as in FIG. 1. The drug may be a smart-release or
passive release. The above examples of drug eluting beads 50 are
illustrative and not limiting as to the use of beads 50 as the drug
delivery mechanism to induce continued patency of the filter
12.
[0053] FIG. 7 illustrates yet another embodiment of the present
invention. A drug coating 110 is placed on protection device 10
proximate the filter 12, illustrated by the areas identified by
reference numeral 110 in FIG. 7. The coating 110 may be positioned
on the hostwire 14, marker bands 16, the filter itself, in
combination or alternatively on surface of the protection device
10. The coating 110 may be a hydrogel or other such coating. The
hydrogel coating may act similar to the beads 50, previously
discussed, wherein the hydrogel contains a drug or is coated with a
drug such that the hydrogel acts as a drug delivery mechanism. The
drug may also be smart released or passively released depending on
the characteristics of the drug, hydrogel, coating, or combination
thereof.
[0054] Drugs can also be incorporated into a gel conjugate located
proximal to the filter 12 such as in conjunction with the other
embodiments of the present invention. The gel conjugate viscosity
could be selected to decrease with body temperature, so as to
induce the release of the drug once placed in the body.
Alternatively, a saturated sponge or patch placed just proximal to
the filter could release the drug.
[0055] While the drug could be released passively by infusion,
dissolution or leaching, as described above, the need for providing
a drug at certain intervals could also be addressed. This could be
accomplished by the use of barrier technologies, (i.e. a film over
the drug) to control the kinetics of the drug release. The
thickness of the film could vary in regions of the device so the
drug would be released in different amounts and/or at different
places at various time intervals.
[0056] Drug release may also be controlled by a change in
environmental conditions such as a pressure drop across the device,
causing increased drug release as the device becomes occluded.
Stimuli sensitive polymers (SSP's) are currently available as
coatings that are capable of responding to their environment and
controlling the delivery of functional substances. The SSP fibers
may be swollen with water so as to entrap an active substance. When
there is an environmental change such as temperature, pH, light,
salt, electrical field or stress, the collapse of the SSP acts as a
self-activating mechanism for releasing the drug. The environmental
change may be a change in viscosity or pressure caused by platelet
activation and aggregation followed by coagulation leading to
fibrin formation in the blood of the patient's vascular system. The
SSP fibers could incorporate the drug eluting beads 50 discussed
above such as by entrapping the beads 50 in the SSP fibers. The
beads 50 may then be released when there is a change in condition
of the bloodstream viscosity or pressure indicating the onset of
filter 12 occlusion. Such a change in conditions would activate the
drug delivery mechanism and release the beads 50 and drugs
therein.
[0057] The formation of thrombus often occurs distal to the filter
12, in the areas of stagnant and/or disrupted blood flow patterns.
Thus, the drug delivery methods discussed herein may be positioned
distal to the filter 12 to address this problem. Additionally, flow
re-directors could be placed distal to the filter 12 so as to
encourage the drug to remain concentrated around the filter 12. An
example of such a flow re-director is a variable size vascular plug
placed distal to the filter 12 to be used as a regulator of flow
and/or pressure across the filter 12. Such control of flow in
combination with a drug delivery system may further facilitate
filter 12 patency.
[0058] FIG. 8 illustrates another embodiment of a drug delivery
device for delivering a drug to a protection device 10 for
maintaining filter 12 patency. In this embodiment, an expandable
bladder 82 is used to infuse the drug from a reservoir or cavity
80, defined by a lumen 72 through hostwire 14, through a plurality
of delivery ports 74. The bladder 82 is expanded within lumen 72 to
force the drug positioned within the reservoir 80 to pass through a
delivery portion where the drug is released through weep holes or
ports 74. Once the drug is delivered through the ports 74 it is
able to be locally delivered to the filter 12 of the protection
device 10 and the area surrounding the filter 12.
[0059] As illustrated, the delivery ports 74 may be a plurality of
apertures 74 spaced about the side wall 76 of the reservoir 80. The
apertures 74 form channels from the interior of the lumen 72 to the
exterior of the side wall 76 for allowing the drug to be delivered
from within the lumen 72 to the exterior of the tubular member 81.
The drug delivery mechanism 15 may deliver the drug by expanding
within the lumen 72 (for example, as a result of increased
temperature) thereby forcing the drug to exit the reservoir 80 and
the delivery ports 74. As the drug is released from the lumen 72 it
is able to be delivered to the filter 12 portion of the protection
device 10. The drug is then able to facilitate continued patency of
the filter 12.
[0060] As illustrated in FIG. 8, the drug delivery mechanism 15 may
be activated by the infusion of the drug delivery portion 80 with
the drug from the expansion of an expandable bladder 82. The
bladder 82 may be an inflatable member such as a balloon that is
pre-inflated and affixed to the interior of the tubular member The
exit ports 74 allow for the drug to be channeled there-through to
the outer surface of the wall of the drug delivery structure. As
the bladder 82 expands due to flow of drug through the apertures,
the pressure within the bladder and within the hollow portion 80
decreases. The rate of expansion of the bladder 82 may be
controlled so as to control the rate at which the drug is delivered
from the device. For example, a bladder pre-inflated at low
pressure will result in a slower release of the drug than a bladder
pre-inflated at high pressure.
[0061] The tubular member 81 is a generally cylindrical tube having
a side wall 76 with an inner lumen 72 extending therewithin. The
tube 81 has a plurality of apertures 74 formed through at the side
wall 76 of the tubular member 81 allowing communication of a
substance within the inner lumen 72 to the exterior of the side
wall 76 The apertures 74 are spaced about the circumference of the
side wall 76 and may have various diameters and be of a size and
number to control the release rate of the drug in cooperation with
bladder pressure. The side wall 76 has an elongate dimension
wherein the plurality of apertures 74 may be spaced along at least
a portion of the elongate dimension. The apertures 74 may be
staggered along the side wall circumference, such as in a spiral
pattern, a ring pattern, or any other such combination random or
ordered, over the side wall 76. A portion of the side wall 76 may
be tapered outwardly.
[0062] Methods of delivering the drug include a pump powered by
induction, a screw-drive, an elastomer drive, or blood flow. The
electromotive force or peristaltic action provided by the heart may
also be used to drive the drug delivery mechanism 15.
Alternatively, osmotic, hypertonic or capillary action could
function as the driving force to pump the drug through the tubular
member. Any mechanism capable of providing a driving force to the
drug may be employed such as the use of temperature or ultrasound
to initiate such driving force.
[0063] The tubular member 81 may allow the drug to be dispensed
into the lumen 72 and/or maintained within the drug delivery
portion of the device and delivered through the weep holes 74 in
the wall 76 of the tubular member 81. The weep holes 74 are spaced
within the wall 76 of the tubular member 81. A plurality of tubes
may be incorporated having a corresponding plurality of sidewalls
and each tubing having a predetermined number of apertures.
[0064] FIG. 9 illustrates a reservoir 80 that has a fluted portion
90 to increase surface area on which coating capacity can be
maximized. It is contemplated that such a fluted lumen could be
employed in the embodiment illustrated in FIG. 7. The fluted
portion 90 can be coated along a length as at reference numeral 110
or a longer or shorter length, as appropriate.
[0065] Turning now to FIGS. 10-11, it is contemplated that the drug
delivery mechanism illustrated in FIG. 8 may have more than a
single lumen 72. For example, FIG. 10 illustrates a first lumen 94
adjacent a second lumen 96. Each lumen 94, 96 may be capable of
delivering a drug therefrom. It is contemplated that each lumen may
be capable of delivering a different drug or that each lumen be
capable of delivering a component of a drug capable of mixing with
the component in the adjacent lumen. It is further contemplated
that any number of adjacent lumens may be incorporated into the
drug delivery portion 80.
[0066] FIG. 11 illustrates a drug delivery mechanism 15 having a
coaxial lumen 100 such that a first lumen 99 extends coaxially
relative to a wall 104 second coaxial lumen 100. Thus, each drug
delivery lumen may have at least a single wall 76 with a plurality
of weep holes 74, wherein the drug delivery mechanism may have a
plurality of side walls 76. The use of more than one lumen for
simultaneous infusion of more than one drug for in situ mixing can
be employed to inhibit reactions during the intrinsic or common
pathway of fibrin clot formation or platelet activation and/or
aggregation. The multiple lumens may be individually, sequentially
or simultaneously infused. The tubular member, guide catheter (not
shown) or an accessory catheter(not shown) could be charged with a
reservoir of drugs.
[0067] The delivery ports 74 may be spaced in a variety of
arrangements on the side wall 76 of the respective tubular members
as illustrated in FIGS. 10-11.
[0068] Alternatively, if a plurality of side walls are present, the
delivery ports 74 may be spaced in alternative configurations on
each side wall 76. For example, the delivery ports 74 may be spaced
circumferentially at various along the length of the wall, the
ports 74 may be arbitrarily patterned along the length of the wall,
the ports 74 may be spaced so as to helically wind about the length
of the wall, and any combination or other such means of spacing,
random or ordered so as to provide a plurality of delivery ports 74
about the side wall of the lumen 72 for delivering of a drug from
the lumen 72.
[0069] The spacing and sizing of the apertures 74 may be configured
to control the rate of diffusion of the drug into the blood vessel.
The apertures 74 may have a predetermined size and spacing that
allows for a slower or faster relative rate of diffusion.
Controlling the rate of diffusion may lessen the shear stresses on
blood flowing toward the filter 12. A lesser shear stress is
preferable over a high pressure drug delivery that may create an
accelerated flow pattern that could be detrimental to flow dynamics
surrounding the filter 12.
[0070] After the drug is delivered through the delivery port 74 it
is able to become infused within the fluid flowing on the outer
surface of the tubular member 81. For example, if the tubular
member 81 is positioned within a blood stream the drug will become
infused within the blood stream. As the blood stream is flowing
toward the filter 12, the filter 12 being downstream, the drug will
likewise be delivered to the filter 12 from a upstream location
thus providing for local drug delivery. Alternatively, the lumen 94
may be located adjacent to another lumen 96. The drug would then be
delivered into the lumen 105 and be able to flow and intermix with
the fluid, such as a drug or component, within the lumen 105. The
combination of the drugs from the first and second lumens 94, 96
may then be delivered into a fluid external to the lumen 105, such
as the blood within a blood vessel.
[0071] In another alternative, the first tubular member 102 may be
coaxial with a second tubular member 104. Thus the drugs within the
first and second tubes 102, 104 may be delivered into the
bloodstream directly without intermixing prior to passage through
ports 74, so as to mix and be delivered externally to the filter
12. As the drug is delivered into a fluid such as blood, it is able
to be delivered with the flow of fluid to distal portions of the
protection device 10, preferably to the filter 12. The drug may
provide for an increased concentration of anti-coagulants, or other
such drugs preventing formation of thrombi and occlusions of the
filter 12. The local concentration of the drug may also cover
portions of the drug delivery mechanism 15 and tubular members and
portions of the protection device 10 that are proximal and distal
to the filter 12. Infusing the drug upstream from the filter 12 and
allowing it to flow to the filter 12 may also deliver the drug to
local stasis areas in the vicinity of the filter 12 where it can
minimize and/or prevent clotting and/or coagulation. This may flush
loose partially adherent emboli, that may otherwise become
dislodged during or after filter 12 removal, into the filter 12
along with the drug delivery medium.
[0072] The shape, size, and workings of the filter 12 are not
critical to the efficacy of the present invention. The filter 12
used in the embodiments of the present invention is contemplated as
a possible type of filter 12 to be used with the present invention.
However, the filter 12 may assume a variety of configurations such
as a basket, a windsock, a flat shape, and elongated shape, the
filter 12 may have a cover or an alternating periphery or diameter.
The filter 12 must merely perform the function of preventing the
passage of particulate material of a predetermined size. The
present invention addresses the delivery of a drug to a filter 12
to facilitate filter patency, and contemplates the drug delivery
system disclosed herein as incorporating a variety of filter sizes,
shapes and configurations. The filter 12 may be attached to the
distal portion of a hostwire 14. The hostwire 14 may extend through
the lumen 72 containing the drug. Alternatively, the hostwire 14
may have a hollow portion 80 for containing and delivering the drug
therefrom.
[0073] Possible drugs to be used in the present invention include
IIb/IIIa inhibitors and any other such anti-platelet agents, or
drugs for preventing occlusions to the filter 12 during a medical
procedure, such as heparin, Aggrastat or Integrilin or fibrinolytic
drugs. The drugs may be precursors or drug agents to be mixed with
other fluids so as to effect the purpose of the present invention.
For example, a drug in a first lumen 72 may not be capable of
preventing occlusion unless or until mixed with a drug in the
second lumen 72 or when mixed with blood, for example. Such drugs
help to maintain filter 12 patency even with reduced filter 12 pore
sizes without negative effects of systemic drug administration such
as excessive bleeding.
[0074] In summary, an advantage of the present invention is
increased patency, such as the length of time patency is maintained
within the filter, or the degree of patency allowed as a result of
drug delivery to the protection device. This gives the operator or
physician additional time to perform a medical procedure, thus
making the procedure safer for the patient.
[0075] It will be understood that this disclosure, in many
respects, is only illustrative. Changes may be made in details,
particularly in matters of shape, size, material, and arrangement
of parts without exceeding the scope of the invention. Accordingly,
the scope of the invention is as defined in the language of the
appended claims.
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