U.S. patent application number 12/319255 was filed with the patent office on 2009-07-09 for detachment mechanisms for implantable devices.
This patent application is currently assigned to Boston Scientific Scimed, Inc.. Invention is credited to James M. Anderson, Benjamin Arcand, Kirsten Carroll, Gregory E. Mirigian, Jay Rassat, Derek Sutermeister, Clifford Teoh, Michael Williams.
Application Number | 20090177261 12/319255 |
Document ID | / |
Family ID | 40579107 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090177261 |
Kind Code |
A1 |
Teoh; Clifford ; et
al. |
July 9, 2009 |
Detachment mechanisms for implantable devices
Abstract
Disclosed herein are detachment mechanisms for vaso-occlusive
devices that allow for rapid operator-controlled release of the
vaso-occlusive device into the selected site. Also disclosed are
vaso-occlusive assemblies comprising these detachment mechanisms
and methods of using these detachment mechanisms and vaso-occlusive
assemblies.
Inventors: |
Teoh; Clifford; (Los Altos,
CA) ; Williams; Michael; (Oakland, CA) ;
Mirigian; Gregory E.; (Dublin, CA) ; Carroll;
Kirsten; (San Francisco, CA) ; Anderson; James
M.; (Fridley, MN) ; Rassat; Jay; (Buffalo,
MN) ; Arcand; Benjamin; (Minneapolis, MN) ;
Sutermeister; Derek; (Eden Prairie, MN) |
Correspondence
Address: |
ROBINS & PASTERNAK
1731 EMBARCADERO ROAD, SUITE 230
PALO ALTO
CA
94303
US
|
Assignee: |
Boston Scientific Scimed,
Inc.
|
Family ID: |
40579107 |
Appl. No.: |
12/319255 |
Filed: |
January 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61010048 |
Jan 4, 2008 |
|
|
|
Current U.S.
Class: |
623/1.11 ;
128/898; 606/200; 623/1.12; 623/1.15 |
Current CPC
Class: |
A61B 2017/1209 20130101;
A61B 17/1214 20130101; A61B 17/12113 20130101; A61B 17/12022
20130101; A61B 17/12109 20130101; A61B 2017/12077 20130101; A61B
17/12145 20130101; A61B 2017/12068 20130101 |
Class at
Publication: |
623/1.11 ;
606/200; 623/1.15; 623/1.12; 128/898 |
International
Class: |
A61M 29/00 20060101
A61M029/00; A61F 2/06 20060101 A61F002/06; A61B 19/00 20060101
A61B019/00 |
Claims
1. A detachment mechanism for an implantable device, the detachment
mechanism comprising: at least one material that changes
configuration upon application of heat or electrical energy,
wherein the change in configuration releases the implantable
device, and further wherein if the material extends into a lumen of
the implantable device, the material directly contacts at least a
portion the implantable device.
2. The detachment mechanism of claim 1, wherein the change in
configuration comprises a reduction in diameter and/or volume of
the material.
3. The detachment mechanism of claim 1, wherein the change in
configuration comprises an expansion in diameter and/or volume of
the material.
4. The detachment mechanism of claim 1, wherein the change in
configuration comprises a deflection of the detachment
mechanism.
5. The detachment mechanism of claim 1, wherein the detachment
mechanism comprises an electroactive polymer.
6. The detachment mechanism of claim 5, wherein the detachment
mechanism further comprises a metal or polymer and wherein the
electroactive polymer is layered onto the metal or polymer.
7. The detachment mechanism of claim 1, wherein the detachment
mechanism comprises a layered strip of two or more metals of
dissimilar thermal coefficients.
8. The detachment mechanism of claim 7, wherein the layered strip
is wound into a spiral shape.
9. The detachment mechanism of claim 1, wherein the at least one
material that changes configuration directly contacts a source of
electric or heat energy.
10. The detachment mechanism of claim 1, wherein the detachment
mechanism directly engages the vaso-occlusive device.
11. The detachment mechanism of claim 1, wherein the detachment
mechanism contacts a structure attached to the implantable
device.
12. A detachment mechanism adapted to detachably engage a
vaso-occlusive device, the detachment mechanism comprising an
element that changes configuration upon application of electrical
current or heat; and means for applying electrical current or heat
to the change the configuration of the element.
13. A vaso-occlusive assembly comprising a vaso-occlusive device; a
detachment mechanism according to claim 1; and a source of
electrical current or a heat source in contact with the detachment
mechanism.
14. The vaso-occlusive assembly of claim 13, wherein the
vaso-occlusive device comprises a helically wound vaso-occlusive
coil.
15. The vaso-occlusive assembly of claim 13, further comprising a
delivery mechanism.
16. The vaso-occlusive assembly of claim 15, wherein the delivery
mechanism comprises a stopper element.
17. A vaso-occlusive assembly comprising a vaso-occlusive device; a
detachment mechanism according to claim 12; and a source of
electrical current or a heat source in contact with the detachment
mechanism.
18. A method of at least partially occluding an aneurysm, the
method comprising the steps of introducing a vaso-occlusive
assembly according to claim 13, into the aneurysm, wherein the
detachment mechanism engages the vaso-occlusive device; and
changing the configuration of the detachment mechanism by applying
or removing electrical current or thermal energy such that the
detaching mechanism releases the vaso-occlusive device into the
aneurysm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Application No. 61/010,048, filed Jan. 4, 2008, the
disclosure of which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] Compositions and methods for implanting devices are
described. In particular, detachment mechanisms that change
configuration to deploy an implantable device such as an embolic
device and assemblies comprising these detachment mechanisms are
described.
BACKGROUND
[0003] Implantable devices are used for many indications including
in the reproductive tract (e.g., uterine artery, fallopian
occlusion), billiary implants and/or for peripheral and
neurovasculature indications. For example, an aneurysm is a
dilation of a blood vessel that poses a risk to health from the
potential for rupture, clotting, or dissecting. Rupture of an
aneurysm in the brain causes stroke, and rupture of an aneurysm in
the abdomen causes shock. Cerebral aneurysms are usually detected
in patients as the result of a seizure or hemorrhage and can result
in significant morbidity or mortality.
[0004] There are a variety of materials and devices which have been
used for treatment of peripheral and neurovascular aneurysms,
including platinum and stainless steel microcoils, polyvinyl
alcohol sponges (Ivalone), and other mechanical devices. For
example, vaso-occlusion devices are surgical implements or implants
that are placed within the vasculature of the human body, typically
via a catheter, either to block the flow of blood through a vessel
making up that portion of the vasculature through the formation of
an embolus or to form such an embolus within an aneurysm stemming
from the vessel. One widely used vaso-occlusive device is a helical
wire coil having windings that may be dimensioned to engage the
walls of the vessels. (See, e.g., U.S. Pat. No. 4,994,069 to
Ritchart et al.). Variations of such devices include polymeric
coatings or attached polymeric filaments have also been described.
See, e.g., U.S. Pat. Nos. 5,226,911; 5,935,145; 6,033,423;
6,280,457; 6,287,318; and 6,299,627. In addition, coil designs
including stretch-resistant members that run through the lumen of
the helical vaso-occlusive coil have also been described. See,
e.g., U.S. Pat. Nos. 5,582,619; 5,833,705; 5,853,418; 6,004,338;
6,013,084; 6,179,857; and 6,193,728.
[0005] Coils have typically been placed at the desired site within
the vasculature using a catheter and a pusher. The site is first
accessed by the catheter (e.g., small diameter catheters such as
those shown in U.S. Pat. Nos. 4,739,768 and 4,813,934). The
catheter may be guided to the site through the use of guidewires
(see U.S. Pat. No. 4,884,579) or by flow-directed means such as
balloons placed at the distal end of the catheter.
[0006] Once the site has been reached, the catheter lumen is
cleared by removing the guidewire (if a guidewire has been used),
and one or more coils are placed into the proximal open end of the
catheter and advanced through the catheter with a pusher. Once the
coil reaches the distal end of the catheter, it is discharged from
the catheter by the pusher into the vascular site. However, there
are concerns when discharging the coil from the distal end of the
catheter. For example, the plunging action of the pusher and the
coil can make it difficult to position the coil at the site in a
controlled manner and with a fine degree of accuracy. Inaccurate
placement of the coil can be problematic because once the coil has
left the catheter, it is difficult to reposition or retrieve the
coil.
[0007] Several techniques involving Interlocking Detachable Coils
(IDCs), which incorporate mechanical release mechanisms and
Guglielmi Detachable Coils (GDCs), which utilize electrolytically
actuated release mechanisms, have been developed to enable more
accurate placement of coils within a vessel.
[0008] Electrolytic coil detachment is disclosed in U.S. Pat. Nos.
5,122,136; 5,354,295; 6,620,152; 6,425,893; and 5,976,131, all to
Guglielmi et al., describe electrolytically detachable embolic
devices. U.S. Pat. No. 6,623,493 describes vaso-occlusive member
assembly with multiple detaching points. U.S. Pat. Nos. 6,589,236
and 6,409,721 describe assemblies containing an electrolytically
severable joint. The coil is bonded via a metal-to-metal joint to
the distal end of the pusher. The pusher and coil are made of
dissimilar metals. The coil-carrying pusher is advanced through the
catheter to the site and a small electrical current is passed
through the pusher-coil assembly. The current causes the joint
between the pusher and the coil to be severed via electrolysis. The
pusher may then be retracted leaving the detached coil at an exact
position within the vessel. Since no significant mechanical force
is applied to the coil during electrolytic detachment, highly
accurate coil placement is readily achieved. In addition, the
electric current may facilitate thrombus formation at the coil
site. The disadvantage of this method is that the electrolytic
release of the coil may require a period of time that may inhibit
rapid detachment of the coil from the pusher.
[0009] There is a need to provide alternative mechanisms for
delivering implants, such as embolic coils, that allow for both
accurate positioning of the implantable device and rapid detachment
from the delivery device.
SUMMARY
[0010] Disclosed herein are detachment mechanisms for implantable
devices, as well as assemblies comprising the detachment mechanisms
and implantable devices. Methods of making and using these
detachment mechanisms and assemblies are also provided.
[0011] In one aspect, provided herein is a detachment mechanism for
an implantable device, the implantable device optionally having a
lumen therein, the detachment mechanism comprising: at least one
material that changes configuration upon application of heat or
electrical energy, wherein the change in configuration releases the
implantable device, and further wherein if the material extends
into the optional lumen of the implantable device, the material
directly contacts at least a portion the implantable device
defining the lumen. Thus, if the material extends into the lumen of
the device, the material is in direct contact with the interior
surface of the implantable device. In certain embodiments, the
change in configuration comprises a reduction in diameter and/or
volume of the material. In other embodiments, the change in
configuration comprises an expansion in diameter and/or volume of
the material. In still other embodiments, the change in
configuration comprises a deflection of the detachment
mechanism.
[0012] In certain aspects, the detachment mechanisms described
herein comprise an electroactive polymer and/or a metal or polymer,
for example the electroactive polymer may be layered onto the metal
or polymer.
[0013] In other aspects, the detachment mechanisms described herein
comprise a layered strip of two or more metals of dissimilar
thermal coefficients. In certain embodiments, the layered strip is
wound into a spiral shape.
[0014] In any of the detachment mechanisms described herein, the
material may directly contacts a source of electric or heat energy.
Furthermore, any of the detachment mechanisms described herein may
directly engage the vaso-occlusive device. In addition, the
detachment mechanism may contacts a structure attached to the
implantable device.
[0015] In another aspect, described herein is a detachment
mechanism adapted to detachably engage a vaso-occlusive device, the
detachment mechanism comprising an element that changes
configuration upon application of electrical current or heat; and
means for applying electrical current or heat to the change the
configuration of the element.
[0016] In yet another aspect, provided herein is a vaso-occlusive
assembly comprising a vaso-occlusive device; any of the detachment
mechanisms described herein; and a source of electrical current or
a heat source in contact with the detachment mechanism. In certain
embodiments, the vaso-occlusive device comprises a helically wound
vaso-occlusive coil. In still further embodiments, the
vaso-occlusive assembly may further comprise a delivery mechanism,
for example, a delivery mechanism comprising a stopper element.
[0017] In a still further aspect, described herein is a method of
at least partially occluding an aneurysm, the method comprising the
steps of introducing any of the vaso-occlusive assemblies described
herein into the aneurysm, wherein the detachment mechanism engages
the vaso-occlusive device; and changing the configuration of the
detachment mechanism by applying or removing electrical current or
thermal energy such that the detaching mechanism releases the
vaso-occlusive device into the aneurysm.
[0018] These and other embodiments will readily occur to those of
skill in the art in light of the disclosure herein.
BRIEF DESCRIPTION OF THE FIGURES
[0019] FIG. 1 is a partial cross-section, side view depicting an
exemplary vaso-occlusive assembly as described herein. The
electroactive polymer is shown in the configuration in which it
engages the vaso-occlusive device to be delivered.
[0020] FIG. 2 is a partial cross-section, side view depicting the
exemplary vaso-occlusive assembly of FIG. 1 and showing the
electroactive polymer detachment mechanism in the configuration
that does not engage the vaso-occlusive device.
[0021] FIG. 3, panels A, B and C, are partial cross-section, side
views depicting another exemplary vaso-occlusive as described
herein, in which the electroactive polymer extends beyond the
distal end of the delivery device. FIG. 3A shows such an assembly
when the electroactive polymer engages the vaso-occlusive device.
FIG. 3B shows the assembly of FIG. 3A upon changing the
configuration of the polymer to increase the length and reduce
thickness of the polymer. FIG. 3C shows an intermediate
de-energized state, which allows the delivery device to function as
a coil pusher.
[0022] FIG. 4 is a cross-section, side-view of yet another
exemplary assembly as described herein and shows a variation in
which a structural element is attached to the distal end of the
vaso-occlusive device to engage the electroactive polymer in one
configuration and which, in the second configuration, releases the
structure and, accordingly, the vaso-occlusive device.
[0023] FIG. 5 is a cross-section, side-view of yet another
exemplary assembly as described herein and shows a design having
two (inner and outer) layers of electroactive polymer.
[0024] FIG. 6, panels A to F, are cross-sections of exemplary
configurations showing layering of electroactive polymer, filler
material and core material, with or without slots.
[0025] FIG. 7 is a cross-section, side-view of an exemplary
assembly as described herein including a delivery device with one
or more apertures in the sidewalls.
[0026] FIG. 8 is a cross-section view of an exemplary electroactive
polymer configuration that includes apertures (pores) in the
electroactive polymer.
[0027] FIGS. 9A and 9B are cross-section views of additional
exemplary electroactive polymer configurations. FIG. 9A shows an
embodiment that includes slots in the electroactive polymer. FIG.
9B shows a ring shaped electroactive polymer with channels in the
outer layer.
[0028] FIG. 10, panels A and B, are partial cross-section, side
views depicting an exemplary assembly as described herein
comprising an electroactive polymer that contracts upon activation
with electrical current. FIG. 10A shows the assembly when electric
current is applied to the electroactive polymer, which contracts to
release the embolic coil. FIG. 10B shows the assembly in the
un-activated in which the electroactive polymer is in an expanded
configuration that engages the embolic coil.
[0029] FIG. 11, panels A and B, are partial cross-section, side
views of another exemplary embodiment in which the electroactive
polymer is in an expanded configuration upon activation with
electrical current. FIG. 11A shows the assembly in the activated
(engaged) configuration and FIG. 11B shows contraction of the
electroactive polymer in the un-activated configuration (when
electrical current is removed).
[0030] FIG. 12, panels A and B, are overviews of a bi-layered strip
of materials where each layer responds differently to the
application of electrical current or heat. FIG. 12A shows an
exemplary strip prior to application of heat or electrical current.
FIG. 12B shows dissimilar expansion of the disparate layers upon
application of heat or electrical current.
[0031] FIG. 13, panels A and B, are overviews of a bi-layered strip
used in detachment mechanisms as described herein. FIG. 13A shows
the bi-layer strip prior to application of heat or electrical
current. FIG. 13B shows deflection of the strip upon application of
heat or electrical current due to the dissimilar thermal and/or
electrical response characteristics of the layers.
[0032] FIG. 14, panels A and B are cross-section views of an
exemplary detachment mechanism comprising a bilayer strip as shown
in FIGS. 12 and 13 wound into a spiral shape and inserted into the
lumen of an implantable device. FIG. 14A shows the strip in the
unengaged position. FIG. 14B shows the strip when engaged with the
inner surface of the lumen of the implantable device.
[0033] FIG. 15 is a cross-section view of an exemplary detachment
mechanism comprising bilayer strips extending into the lumen of the
implantable embolic coil and contacting the inner surface of the
embolic coil. The strips are shown in the configuration in which
they engage spaces in the winds of the embolic coil.
[0034] FIG. 16 is a cross-section view of the exemplary detachment
mechanism of FIG. 15 shown in the configuration in which they
deflect toward each other and no longer engage the coil.
[0035] FIG. 17 is a cross-section, side-view of an exemplary
assembly as described herein including a delivery device.
[0036] FIG. 18 is a cross-section, side-view of an exemplary
assembly as described herein including a delivery device with one
or more apertures in the sidewalls.
[0037] FIG. 19 is a partial cross-section, side view depicting an
exemplary vaso-occlusive assembly comprising an electroactive
polymer plug in the delivery device. The electroactive polymer plug
is shown in the reduced configuration in which the distal boundary
of the plug is proximal to the distal end of the delivery
device.
[0038] FIG. 20 is a partial cross-section, side view depicting the
exemplary vaso-occlusive assembly of FIG. 19 and shows the
electroactive polymer plug in the expanded configuration in which
the distal boundary of the plug is at or near the distal end of the
delivery device, thereby extruding the vaso-occlusive device into
the selected site.
[0039] FIG. 21 is a partial cross-section, side view depicting an
exemplary vaso-occlusive assembly as described herein. The delivery
device includes a collar that is sized to allow for the passage of
the vaso-occlusive device. The electroactive polymer plug is shown
in the reduced configuration in which the distal boundary of the
electroactive polymer plug is proximal to the distal end of the
delivery device and collar.
[0040] FIG. 22 is a partial cross-section, side view of the
assembly shown in FIG. 21 with the electroactive polymer plug in
the expanded configuration which causes the plug to extend into the
collar and extrude the vaso-occlusive device from the delivery
mechanism.
[0041] FIG. 23 is a cross-section, side-view of another exemplary
assembly as described herein and shows a design having apertures in
the proximal stopper to allow flow of electrolytes to the
electroactive polymer.
[0042] FIG. 24 is a cross-section, side-view of the exemplary
assembly shown in FIG. 23 and further depicting a delivery device
with one or more apertures in the sidewalls.
[0043] FIG. 25, panels A to C, are side-views showing an exemplary
variation in which a detachment mechanism comprising an
electroactive polymer is attached to a structure on the proximal
end of the implantable device. In the unexpanded configuration, the
electroactive polymer engages the structure and in the expanded
configuration releases the structure and deploys the implantable
device.
[0044] FIG. 26, panels A and B, are cross-section, side-views
showing an exemplary variation in which the implantable device
engages a pusher element when the electroactive polymer is in the
contracted position. FIG. 26B depicts how, upon expansion of the
electroactive polymer, the implantable device is released.
[0045] FIG. 27, panels A to D, are cross-section showing an
exemplary variation in which the implantable device engages a
pusher element via a ring shaped electroactive polymer. FIG. 27A
shows the electroactive polymer ring in the engaged (unexpanded)
configuration and FIG. 27B shows linear expansion of the
electroactive polymer ring which releases the ring from the pusher
element. FIG. 27C shows an electroactive polymer ring structure
made of multiple linearly-expanding elements in an unexpanded
configuration and FIG. 27D shows the ring of FIG. 27C after linear
expansion of the electroactive polymer elements.
[0046] FIG. 28, panels A and B, are cross-section, side-views
showing another exemplary variation in which the implantable device
engages a pusher element via a ball joint when the electroactive
polymer is in the contracted position (FIG. 28A). Upon expansion of
the electroactive polymer, the implantable device is released (FIG.
28B).
[0047] FIG. 29, panels A and B, are cross-section, side-views
showing another exemplary variation in which the implantable device
engages a pusher element via arms through a ring structure when the
electroactive polymer is in the contracted position. Upon expansion
of the electroactive polymer, implantable device is released.
[0048] FIGS. 30, panels A to D, show an embodiment where the
unexpanded electroactive polymer engages an implantable coil and
pusher element via a structure extending from the proximal end of
the coil. FIG. 30A is a cross-section side-view of the assembly
with the electroactive polymer in the unexpanded position. FIG. 30B
is a cross-section, side-view of the assembly with the
electroactive polymer in the expanded position. FIG. 30C is a top
view of the structure extending from the implantable coil and
electroactive polymer in unexpanded configuration. FIG. 30D is a
top view of the structure shown in FIG. 30C with the electroactive
polymer in the expanded configuration.
[0049] FIG. 31, panels A and B, show a variation including an
electroactive polymer coupling receiver in which the structure
extending from the implantable device is engaged in the coupling
receiver when the electroactive polymer is in the expanded
configuration (FIG. 31A) and which releases the implantable device
when the electroactive polymer is in the unexpanded configuration
(FIG. 31B).
[0050] FIG. 32, panels A and B, show an electroactive polymer
activated compression (e.g., hydraulic) detachment mechanism. FIG.
32A shows the assembly when the electroactive polymer is in the
unexpanded configuration and FIG. 32B shows the same assembly after
expansion of the electroactive polymer.
[0051] FIG. 33, panels A and B, are cross-section, side-views
showing another exemplary variation in which the implantable device
engages a T-bar structure when the electroactive polymer is in the
contracted position (FIG. 33A). Upon expansion of the electroactive
polymer, the implantable device is released (FIG. 33B).
[0052] FIG. 34, panels A and B, are cross-section, side-views
showing another exemplary variation in which the implantable device
engages a T-bar structure when the electroactive polymer is in the
contracted position (FIG. 34A). Upon expansion of the electroactive
polymer, the implantable device is released (FIG. 34B).
[0053] FIG. 35, panels A and B, are cross-section, side-views
showing another exemplary variation in which the implantable device
includes a proximal ball structure which is engaged in the delivery
device by the electroactive polymer in an expanded position (FIG.
35A). Upon contraction of the electroactive polymer, the
implantable device is released (FIG. 35B).
DETAILED DESCRIPTION
[0054] Detachment mechanisms for implantable devices, including
occlusive (e.g., embolic) devices, and assemblies are described.
The detachment mechanisms described herein can be utilized in
devices useful in vascular and neurovascular indications and are
useful in delivering embolic devices to aneurysms, for example
small-diameter, curved or otherwise difficult to access
vasculature, for example aneurysms, such as cerebral aneurysms.
Methods of making and using these detachments and assemblies
comprising these detachments are also aspects of this
disclosure.
[0055] Currently, the gold-standard method of delivering
implantable vaso-occlusive devices is via electrolytic detachment
(e.g., GDC coils). While electrolytic detachment solves the
drawbacks of earlier mechanical detachments (e.g., the need for the
mechanism to be fully inside the catheter in order to remain
engaged), electrolytically detachable coils typically require
approximately 20-30 seconds detachment times.
[0056] The detachment mechanisms described herein that allow for
rapid and precise detachment of an implantable device upon
application of electrical energy and/or heat. Advantages of the
present disclosure include, but are not limited to, (i) the
provision of rapidly detachable vaso-occlusive devices; (ii) the
provision of mechanically detachable implantable devices that can
be extended beyond the catheter tip, thereby allowing for more
precise placement of the devices; and (iii) the provision of
occlusive devices that minimize the mechanical motion needed to
detach the devices.
[0057] All publications, patents and patent applications cited
herein, whether above or below, are hereby incorporated by
reference in their entirety.
[0058] It must be noted that, as used in this specification and the
appended claims, the singular forms "a", "an", and "the" include
plural referents unless the content clearly dictates otherwise.
Thus, for example, reference to a device comprising "an
electroactive polymer" includes devices comprising of two or more
such materials or multiple layers of the same electroactive
polymer.
[0059] The detachment mechanisms described herein allow for rapid
release of the vaso-occlusive device from the delivery mechanism.
By "rapid" release is meant release in less than 30 seconds,
preferably less than 20 seconds and even more preferably between 1
and 15 seconds (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
or 15 seconds).
[0060] The detachment mechanism may take any desired shape. The
detachment mechanism may engage the implantable device by
contacting the exterior of the device, directly (e.g., the exterior
of the device) or indirectly (e.g., via a structure in contact with
the exterior of the device). However, unlike previously described
electroactive detachment mechanisms for implantable devices, when
the detachment extends into the lumen of the implantable device, it
directly engages the interior surface of the device (in either the
activated or inactivated state, depending on the properties of the
selected materials). The detachment mechanism may be shaped into a
ring or spiral structure, for example a spiral wound from a bilayer
strip.
[0061] In certain aspects, the detachment mechanism comprises an
electroactive polymer (EAP) that changes configuration upon the
application to electrical energy. Any electroactive polymer can be
used, so long as it changes configuration sufficiently in response
to application of current. Multiple electroactive polymers may be
used, for example, in layers and/or admixed together. Non-limiting
examples of suitable electroactive polymers include polypyrrole,
nafion, polyanilene, polythiofene and the like. See, e.g., U.S.
Pat. No. 6,933,659 and U.S. Patent Publication 20040182704.
Electroactive polymers may expand or contract upon activation.
[0062] In certain embodiments, the change in configuration of the
electroactive polymer(s) is such that, upon the application of
electrical current, the polymer's diameter is reduced and,
optionally, the axial length is increased. Thus, in the absence of
electrical current, the detachment mechanism engages the
implantable device within the delivery device. This allows that the
delivery-detachment mechanism and vaso-occlusive device to be moved
as a unit, even when the implantable device is secured by the
electroactive polymer such that extends from the distal end of the
delivery mechanism (e.g., delivery catheter or delivery tube). When
electricity is applied, the electroactive polymer changes
configuration (contracts) such that it no longer secures the device
to the delivery device. Accordingly, upon application of
electricity to the device is rapidly released into the selected
site. In these embodiments, the unactivated electroactive polymer
provides a physical compressive grip on the implantable device
(e.g., on the exterior or interior surface and/or on a structure
affixed to the proximal end of the implantable device) until
electrical current is used to active the detachment mechanism.
These "fail safe" embodiments minimize the possibility of false or
premature detachment of the coil and are advantageous in the event
of power failure or accidental interruption so that the embolic
remains attached to the delivery wire.
[0063] Alternatively, the electroactive polymer may be such that
its diameter increases upon application of electrical current. In
these embodiments, electrical energy would be applied during
deployment and release of the implantable device achieved by
stopping the application of electrical current when the implantable
device is in the desired position. In embodiments in which the
electroactive polymer expands upon the application of electrical
energy, the implantable device is positioned within the delivery
device and the electroactive polymer is energized to keep the coil
in the desired position. The device is then introduced into the
access delivery device (e.g., microcatheter). Upon achieving the
desired positioning within the aneurysm, the coil is detached by
de-energizing the electroactive polymer. These embodiments allow
the option of the supplying long lengths of uncut embolic coils to
the surgeon. The surgeon can trim the coils to the desired length
and mount them on the delivery device to deploy the coils. Delivery
devices can be reused multiple times so long as the lumen remains
sufficiently clear for insertion.
[0064] Detachment mechanisms comprising an electroactive polymer
may further comprise metal (e.g., nitinol, stainless steel) and/or
polymeric materials. In certain embodiments, the detachment
mechanism comprises a super-elastic metal alloy such as nitinol
which allows for durability and flexibility. Stainless steel or
other metals or alloys can also be used. A portion or all of the
detachment mechanism may include one or more surface treatments
(coating, machining, microtexturing, etc.). The electroactive
polymer is typically coated onto the surface of the metal and/or
polymeric material.
[0065] In other embodiments, the detachment mechanism comprises two
or more materials (e.g., metals and/or polymers), typically in
layers. Furthermore, in response to thermal or electrical energy,
the two or more materials of the detachment mechanism change
configuration differently. For example, in certain embodiments, the
detachment mechanism comprises a bilayer strip of an electroactive
polymer coated onto a metal or polymer substrate. In other
embodiments, metals or polymers that respond differently when
activated by thermal or electrical energy are employed. The
detachment mechanisms described herein also allow for ready
retrieval and/or repositioning of vaso-occlusive devices.
[0066] Suitable delivery devices include delivery catheters (e.g.,
microcatheters) with or without delivery tubes (hypotubes) therein.
When includes, hypotubes may extend the length of the delivery
catheter or may be only at the distal region. The delivery devices
may include one or more apertures in the side walls that allow for
inflow and outflow of electrolytes. See, also, U.S. Provisional
Patent Application No. 60/930,436, entitled "Catheters for
Electrolytically Detachable Embolic Devices," filed May 16, 2007.
In any of the embodiments described herein, the delivery device may
be slotted or spiral cut to reduce bending stiffness while
maintaining axial controllability.
[0067] In certain embodiments, a braided delivery tube, for example
comprising electrodes or heat conducting elements embedded in the
sidewalls or extending through the lumen of the delivery tube is
employed. Such delivery tubes are adapted to be delivered through
conventional catheters (e.g., microcatheters) and, when extended
from the distal end of the catheter, allow for even more accurate
positioning of the implantable device prior to detachment. In other
embodiments, the electrodes (bi-polar or unipolar) extend through
the part or all of the lumen of the delivery device.
[0068] Furthermore, as noted above, electrical or thermal energy
can be provided to the detachment mechanism in any suitable way.
The energy source can directly contact the detachment mechanism,
for example using a delivery mechanism (e.g., catheter or delivery
tube) comprising electrodes or heat conductors in the side-walls.
See, e.g., U.S. Pat. Nos. 6,059,779 and 7,020,516. In addition, the
electrodes can be attached to a core wire. For example, bi-polar
electrodes and/or anodes alone or twisted with a core wire cathode
can also be used to supply current to the electroactive polymer.
Optionally, the leads may be secured to the core wire, for example
via adhesives or via heat-shrink polymer lamination such as PTFE,
FEP, PET or urethane. The conductive element may include a polymer
jacket/liner to insulate the electrical leads and/or reduce
friction during advancement. Alternatively, the detachment
mechanism can be activated to change configuration indirectly via a
conductive material (e.g., metal) that transmits the electrical or
thermal energy to the detachment junction.
[0069] It will be apparent that one or more of the electrodes
and/or conductive materials that transmit electrical energy to the
electroactive polymer may include insulating coatings (e.g.,
polyimide or the like). For electrical energy, alternating or
direct current may be used. Preferably, direct current is used. The
amount of current applied will vary according to the application
although typically less than 4 volts, preferably around 2 volts is
applied to activate the electroactive polymer of the detachment
mechanism. Likewise, for materials that change configuration in
response to thermal energy, heat can be applied as desired by the
operator to change the configuration of the detachment
mechanism.
[0070] In certain embodiments, the conductor and/or electrodes are
distal to the distal end of the delivery mechanism (e.g., tube or
coil stopper). As shown in the Figures, the detachment mechanism
may be disposed over the conductive surfaces, for example by
physical expansion over the electrodes/heat conductors, heat
shrinking, conductive adhesives, or the like.
[0071] The detachment mechanisms described herein can be adapted to
be used with any implantable device, including, but not limited to,
vaso-occlusive devices, fallopian tube occlusive devices, uterine
implantable devices, billiary implantable devices and the like. The
devices may be metal and/or polymeric. Suitable metals and metal
alloys include the Platinum Group metals, especially platinum,
rhodium, palladium, rhenium, as well as tungsten, gold, silver,
tantalum, and alloys of these metals. The core element may also
comprise of any of a wide variety of stainless steels. Very
desirable materials of construction, from a mechanical point of
view, are materials that maintain their shape despite being
subjected to high stress including but not limited to
"super-elastic alloys" such as nickel/titanium alloys (48-58 atomic
% nickel and optionally containing modest amounts of iron);
copper/zinc alloys (38-42 weight % zinc); copper/zinc alloys
containing 1-10 weight % of beryllium, silicon, tin, aluminum, or
gallium; or nickel/aluminum alloys (36-38 atomic % aluminum).
Particularly preferred are the alloys described in U.S. Pat. Nos.
3,174,851; 3,351,463; and 3,753,700. Especially preferred is the
titanium/nickel alloy known as "nitinol."
[0072] The detachment mechanisms described herein may be used with
implantable devices of any structure, for example, devices of
tubular structures, for examples, braids, coils, combination braid
and coils and the like. Thus, although depicted in the Figures
described below as a vaso-occlusive coil, the device may be of a
variety of shapes or configuration including, but not limited to,
braids, knits, woven structures, tubes (e.g., perforated or slotted
tubes), cables, injection-molded devices and the like. See, e.g.,
U.S. Pat. No. 6,533,801 and International Patent Publication WO
02/096273. The implantable device may change shape upon deployment,
for example change from a constrained linear form to a relaxed,
three-dimensional (secondary) configuration. See, also, U.S. Pat.
No. 6,280,457. In a preferred embodiment, the core element
comprises a metal wire wound into a primary helical shape. The core
element may be, but is not necessarily, subjected to a heating step
to set the wire into the primary shape. Methods of making
vaso-occlusive coils having a linear helical shape and/or a
different three-dimensional (secondary) configuration are known in
the art and described in detail in the documents cited above, for
example in U.S. Pat. No. 6,280,457. Thus, it is further within the
scope of this disclosure that the vaso-occlusive device as a whole
or elements thereof comprise secondary shapes or structures that
differ from the linear coil shapes depicted in the Figures, for
examples, spheres, ellipses, spirals, ovoids, figure-8 shapes, etc.
The devices described herein may be self-forming in that they
assume the secondary configuration upon deployment into an
aneurysm. Alternatively, the devices may assume their secondary
configurations under certain conditions (e.g., change in
temperature, application of energy, etc.).
[0073] FIG. 1 shows a partial cross-section, side-view of an
exemplary detachable vaso-occlusive assembly as described herein in
a configuration in which the electroactive polymer engages the
vaso-occlusive device within delivery device. In this position, the
electroactive polymer 20 engages the proximal region of
vaso-occlusive coil 10, namely tip ball 15 of the vaso-occlusive
coil 10. Electrodes 40, 45 extend through sidewall of delivery tube
30 and contact electroactive polymer 20. For electroactive polymers
that contract upon application of electrical current, FIG. 1 shows
the assembly in the un-activated state, where the electroactive
polymer creates a lumen having an inner diameter (ID) smaller than
the outer diameter (OD) of the embolic coil, allowing it to hold
the coil in place. For electroactive polymers that expand upon
application of electrical current, FIG. 1 shows the assembly in the
activated state, again holding the coil in place.
[0074] FIG. 2 is a side and partial cross-section view of the
vaso-occlusive assembly of FIG. 1 after changing configuration of
the electroactive polymer by application or removal of electrical
current. For electroactive polymers that contract upon application
of electrical energy, hydration and ion transport around the
electroactive polymer shrinks the polymer, thereby reducing its
thickness. Likewise, for electroactive polymers that expand upon
application of electrical energy, the polymer will contract when
the electrical current is removed. In either case, the shrunken
polymer 20 releases its hold on the coil 10, and allows withdrawal
of the delivery device 30 while leaving the coil 10 in the
vessel.
[0075] FIG. 3, panels A to C, show another exemplary assembly in
which the electroactive polymer material 20 extends beyond the
delivery device 30. FIG. 3A shows a cross-section of the assembly
in the engaged configuration. FIG. 3B is a cross-section view of
the embodiment of FIG. 3A upon changing the configuration of the
electroactive polymer by application or removal of electrical
energy. The inner diameter of the tube created by the electroactive
polymer 20 increases and, in addition, the axilinear length of the
polymer increases. This minimizes coil movement during detachment.
FIG. 3C shows the detachment mechanism in an intermediate activated
state in which the thickness of the electroactive polymer 20 is
partially shrunk and the polymer can aid in coil 10 positioning
and/or pushing.
[0076] FIG. 4 shows an exemplary embodiment in which a structural
element (e.g. ball) 70 is secured at or near the proximal end of
the coil 10 and extends through the electroactive polymer 20. The
ball 70 is placed inside the delivery tube and held in place by the
electroactive polymer 20. When the configuration of the
electroactive polymer 20 is changed via anode 75 and cathode 77,
the electroactive polymer 20 changes configuration sufficiently to
produce a luminal gap large enough for the delivery tube to be
withdrawn over the ball 70. This design may provide improved
tensile strength because the tensile load surface is loaded
normally instead of in shear.
[0077] It will be apparent that the structure may be secured to the
coil at any location and by any suitable means, for example,
gluing, soldering, welding, etc. Furthermore, any structural
element can be used, including, for example, ball, rings, hooks and
the like.
[0078] FIG. 5 shows yet another design using multiple layers of
electroactive polymer 20. In this design, the inner and outer
surfaces of the proximal end of the coil 10 are surrounded by
electroactive polymer 20. Also shown are delivery tube 30, anodes
75, and cathodes 77.
[0079] FIG. 6A to 6F are cross-section views of detachment
mechanisms comprising an electroactive polymer and additional
materials. Shown in FIG. 6 are configurations in which the
electroactive polymer is layered with other materials that fill
space and/or provide desirable adhesion properties to the delivery
device or coil. Other configurations, for example, mixtures of
materials and overlapping regions of different materials are also
contemplated. Non-limiting examples of other materials include
metal and/or polymers (e.g., PET).
[0080] FIGS. 6A to 6C depict embodiments in which the electroactive
polymer-comprising structure is a ring or tube-like shape. FIG. 6A
shows a cross-section view of an exemplary detachment mechanism
including an inner electroactive polymer inner layer 20, an outer
core (e.g., tube) layer 85 and a middle layer of filler polymer 80
sandwiched between the electroactive polymer 20 and the outer tube
layer 85. FIG. 6B shows a cross-section view of another exemplary
detachment mechanism including an inner filler polymer layer 80, an
outer tube layer 85 and a middle layer of electroactive polymer 20
sandwiched between the filler polymer 80 and the outer core layer
85. FIG. 6C shows a cross-section view of another exemplary
detachment mechanism including an inner electroactive polymer layer
20, an outer core or tube layer 85 and a middle layer of filler
material 85 sandwiched between the electroactive polymer 20 and the
outer core layer 85. FIG. 6C also illustrates how the detachment
mechanism need not be a solid annulus, but can include one or more
slots 87 or other discontinuous formations that may allow for more
uniform and/or facile expansion and contraction of the
electroactive polymer.
[0081] FIGS. 6D through 6F depict embodiments in which detachment
mechanism comprises a core wire instead of tube. In particular,
FIG. 6D shows a cross-section view of an exemplary detachment
mechanism comprising a core wire 85 surrounded by a layer of filler
material 80, which in turn is surrounded by an outer layer of
electroactive polymer 20. FIG. 6E shows the detachment mechanism of
FIG. 6D further comprising slots 87 in the electroactive polymer 20
and filler material layers 80. FIG. 6F shows a cross-section view
of an exemplary detachment mechanism comprising a core wire 85
surrounded by a layer of electroactive polymer 20, which in turn is
surrounded by an outer layer of filler material 80. Also shown are
slots 87 in the electroactive polymer 20 and filler material layers
80.
[0082] FIG. 7 shows a cross-section view of an exemplary assembly
described herein in which the deployment tube 30 comprises one or
more apertures 95 in the sidewalls of the delivery tube. Also shown
are electroactive polymer 20, which forms a ring in the inside of
the delivery tube 30, electrodes 90 and implantable device 10. The
apertures in the sidewalls allow for both inflow of electrolytes
(e.g., blood) and outflow of electrolytes that can be infused into
the lumen of the delivery device by the operator. Non-limiting
examples of suitable electrolytes include saline, phosphate
buffered saline and the like.
[0083] FIGS. 8 and 9 show exemplary cross-section views of
electroactive polymer 20 configurations included apertures or slots
97 therein. The use of non-solid electroactive polymers provides
more surface area for the diffusion of electrolytes which further
increases the efficiency of the applied electrical energy in
changing the configuration of the polymer and releasing the
implantable device.
[0084] FIG. 10A is a side, cross-section view of an exemplary
vaso-occlusive assembly in which a detachment mechanism comprising
a ring-shaped electroactive polymer 20 disposed to fit within the
lumen of the implantable embolic coil 10 and mounted on the distal
end of dual conductor electrode 32, with positive 35 negative 37
electrodes within electroactive polymer ring 20. The dual conductor
electrode 32, may be coaxial or a twisted pair of conductors. Also
shown in FIG. 10A is marker coil 50, including radio-opaque (e.g.,
platinum) proximal coil winds 55. The electroactive polymer 20
expands upon application of electrical current and is shown in the
un-activated state in which it has a diameter less than the inner
diameter of the embolic coil 10.
[0085] FIG. 10B shows the assembly of FIG. 10A in the activated
state. The diameter of the electroactive polymer 20 increases upon
application of electrical energy to hold the coil 10 in place, for
example against a stopper and/or marker coil 50.
[0086] When the delivery device comprises a marker or stopper coil,
it can be of the same or different diameter than the implantable
device. In certain embodiments, the stopper coil has a slightly
smaller inner diameter than the implantable coil such that when the
coils are axially aligned they contact each other but create a
ridged area at their junctions. In the engaged position, the
electroactive polymer expands to grip the uneven surface more
firmly than if the coils were of the same diameter.
[0087] In embodiments in which the electroactive polymer expands
upon the application of electrical energy, the implantable device
is positioned within the delivery device and the electroactive
polymer is energized to keep the coil in the desired position. For
example, in the design shown in FIG. 10, the electroactive polymer
ring is inserted into the lumen of the main coil and energized. The
device is then introduced into the access delivery device (e.g.,
microcatheter). Upon achieving the desired positioning within the
aneurysm, the coil is detached by de-energizing the electroactive
polymer. These embodiments, allows the option of the supplying long
lengths of uncut embolic coils to the surgeon. The surgeon can trim
the coils to the desired length and mount them on the delivery
device to deploy the coils. Delivery devices can be reused multiple
times so as the lumen remains sufficiently clear for insertion.
Furthermore, these embodiments minimize the possibility of false or
premature detachment of the coil.
[0088] FIG. 11 shows another embodiment in which the electroactive
polymer shrinks (reduces diameter) upon application of electrical
current. FIG. 11A is a side, cross-section of an exemplary
vaso-occlusive assembly in an un-activated (expanded) state. A
detachment mechanism comprising an electroactive polymer 20 is
disposed to fit within the lumen of the implantable dual diameter
embolic coil 10 and mounted on the distal end of dual conductor
electrode 32, with positive 35 negative 37 electrodes. The dual
conductor electrode 32, may be coaxial or a twisted pair of
conductors. Also shown in FIG. 11A is marker coil 50, including
radiopaque (e.g., platinum) proximal coil winds 55 and stopper
bands 57. FIG. 11B shows the assembly of FIG. 11A in the activated
state. The diameter of the electroactive polymer 20 decreases upon
application of electrical energy to release the embolic coil 10
into the desired location in the vessel.
[0089] FIGS. 12 and 13 show side views of still other exemplary
embodiments in which the detachment mechanism 70 is configured as a
composite (layered) strip 60. FIG. 12A shows the composite strip in
the release position and FIG. 12B shows the mismatch in expansion
of the different layers in the activated position. FIG. 13A shows
the composite strip in the release position and also shows a band
77 which may be used to keep the layers of the strip in contact.
FIG. 13B shows the composite strip of FIG. 13A upon activation
(electrical current or heat) which causes different deflection of
the layers of the strip.
[0090] FIG. 14A is front, cross-section view of a composite strip
as shown in FIGS. 12 and 13 wound into a spiral shape and
positioned within the lumen of an implantable coil 10 in the
released configuration. FIG. 14B shows the assembly of FIG. 14A in
the engaged configuration, namely when the layered strip engages
the inner surface of the implantable device 20.
[0091] The layered strip may include an electroactive polymer which
expands or contracts upon application of electrical energy.
Alternatively, the strip may be comprised of two or more dissimilar
metals having disparate thermal expansion coefficients such that,
upon a change in temperature, they change shape with relation to
the other(s), i.e. deflect, bend, and/or expand. It will be
apparent that when an electroactive polymer is used in these
strips, the detachment mechanism is operably liked to a source of
electrical current. Likewise, is dissimilar metals are used, the
strips are operably connected to a heat source.
[0092] FIG. 15 depicts a design using layered strips 60 as
described above. FIG. 15 depicts a cross-section view of an
embodiment in which composite strips 60 extend through the lumen of
marker coil 50 and into the lumen of the implantable embolic coil
10. In the expanded (engaged) position the strips 60 may engage the
coil 10 directly (e.g., into the winds of the implantable coil) or,
alternatively, may engage orifices (e.g., gaps) or structures 80
positioned at appropriate locations within the coil.
[0093] FIG. 16 shows yet another design using layered strips 60
within the lumen of an embolic coil 10 and which engage each other
via interlocking elements 80 in the released configuration. As
shown in FIG. 16, when multiple strips are used within the lumen of
the implantable device, they may be offset from each other such
that, when they are actuated, they pass each other, which may allow
greater range of movement during positioning and deployment. For
instance, the strips may be spaced equally around the lumen of
implantable device (e.g., 180.degree. apart for two strips;
120.degree. apart for 3 strips, etc.).
[0094] As noted above, in any of the embodiments described herein,
there may be one or more layers of electroactive polymer.
Furthermore, the electroactive polymer can be deposited onto any
substrate, for example a metal (e.g., nitinol) or polymer (e.g.,
urethane). The electroactive polymer can be deposited by any means,
for example by coating, gluing, and the like.
[0095] In certain embodiments, the assemblies described herein
further comprise an element (e.g., band) around the proximal end of
the implantable device and/or delivery mechanism to help maintain
contact with the electroactive polymer. Non-limiting examples of
such elements include thin-walled metal (e.g., stainless steel,
nitinol, and/or platinum alloys) and/or polymer (PEEK, PET,
polyimide) bands. Alternatively, a region of the coil (e.g., winds
of the coil) can be soldered or welded together.
[0096] FIG. 17 is a side, cross-section view of an exemplary
vaso-occlusive assembly in which a detachment mechanism comprising
a ring-shaped electroactive polymer 20 is disposed to fit within
the lumen of the implantable embolic coil 10 and mounted on the
distal end of dual conductor electrode 32, with positive 35 and
negative 37 electrodes within electroactive polymer ring 20. Also
shown in FIG. 17 is marker coil 50, including radio-opaque (e.g.,
platinum) proximal coil winds 55 and delivery device 90.
[0097] FIG. 18 is a side, cross-section view of an exemplary
vaso-occlusive assembly as shown in FIG. 17 in which the delivery
device 90 includes apertures 95 in the sidewalls.
[0098] FIG. 19 shows a partial cross-section, side-view of another
exemplary detachable vaso-occlusive assembly as described herein
which includes an electroactive polymer plug 20 in the delivery
tube 30. The electroactive polymer plug 20 is shown in the reduced
volume configuration and contacts the proximal region (tip ball) of
vaso-occlusive coil 10. Electrodes 40, 45 extend through sidewall
of delivery tube 30 and contact electroactive polymer 20. Delivery
tube also comprises a stopper 50 proximal to the electroactive
polymer plug 20. Stopper 50 prevents expansion of the electroactive
polymer proximally within the delivery tube 30. For electroactive
polymers that contract upon application of electrical energy,
hydration, applied voltage from a power supply, and ion transport
around the electroactive polymer shrinks the polymer, thereby
reducing the space it occupies in the delivery tube 30.
[0099] FIG. 20 is a side and partial cross-section view of the
vaso-occlusive assembly of FIG. 19 after the configuration of the
electroactive polymer plug 20 is changed by application or removal
of electrical current to its expanded configuration. The polymer
plug 20 can expand only distally in delivery tube 30 due to stopper
50 and, accordingly, when expanded pushes coil 10 out of the
delivery device and allows withdrawal of the delivery device 30
while leaving the coil 10 in the vessel.
[0100] FIG. 21 shows a partial cross-section, side-view of another
exemplary detachable vaso-occlusive assembly having an
electroactive polymer plug 20 and stopper 50. The electroactive
polymer 20 is shown in the reduced volume configuration and
contacts the proximal region (tip ball) of vaso-occlusive coil 10.
Electrodes 40, 45 extend through sidewall of delivery tube 30 and
contact electroactive polymer 20. Delivery tube also comprises a
stopper 50 proximal to the electroactive polymer 20. Delivery tube
30 includes a collar 35 that is sized to fit the outer diameter of
the vaso-occlusive coil 10.
[0101] FIG. 22 is a side and partial cross-section view of the
vaso-occlusive assembly of FIG. 21 after changing configuration of
the electroactive polymer plug 20 (by application or removal of
electrical current) to its expanded configuration. The expanded
polymer 20 pushes coil 10 out of the collar 35 of delivery device
30 and allows withdrawal of the delivery device 30 while leaving
the coil 10 in the vessel.
[0102] FIG. 23 shows yet another electroactive polymer plug type
assembly as described herein in which the stopper 50 comprises
apertures 55. The apertures allow electrolytes, for example
electrolytic solutions that are infused into the lumen of the
delivery tube by the operator, to contact the electroactive polymer
20.
[0103] FIG. 24 shows a cross-section view of an electroactive
plug-type assembly described herein in which the deployment tube 30
comprises one or more apertures 95 in the sidewalls of the delivery
tube. Also shown are electroactive polymer 20, stopper with
apertures 50, 55, delivery tube 30, electrodes 90 and implantable
device 10. The apertures in the sidewalls allow for both inflow of
electrolytes (e.g., blood) and outflow of electrolytes that can be
infused into the lumen of the delivery device by the operator.
Non-limiting examples of suitable electrolytes include saline,
phosphate buffered saline and the like.
[0104] FIG. 25A shows a side view of another exemplary assembly as
described herein in which an electroactive polymer detachment
mechanism 20 is wound around a structure 72 at the proximal end of
the coil 10. The detachment mechanism 20 may optionally directly
contact the coil 10. FIG. 25A shows the electroactive polymer 20 in
the unexpanded (smaller diameter) configuration in which the coil
10 is engaged by the detachment mechanism 20. FIGS. 25B and 25C
depict the device of FIG. 25A with the electroactive polymer 20 in
the expanded configuration which no longer engages the structure
72, thereby releasing the coil 10. As shown, the structure 72
engaged by the electroactive polymer 20 may be attached to the
proximal end of the coil 10 (FIG. 25B) or to the distal end of a
pusher element, for example a pusher comprising an electrical
conductor 32.
[0105] Although shown in FIG. 25A-C as a coiled structure 72, it
will be apparent that the electroactive polymer 20 may be attached
to any shaped structure, for example, a straight solid or hollow
tube (optionally surfaced roughened, e.g., by mechanical blasting,
grinding or chemical etching). It will also be apparent that the
structure 72 may be made of any material (polymer and/or metal),
for example the same material as the coil (e.g., platinum alloy).
Likewise, the electroactive polymer may take a variety of shapes,
for example a ring shape or a helical (spiral) shape as depicted in
FIG. 25. Optionally, the electroactive polymer may be disposed on a
substrate, for example a thin, flexible polymer such as polyimide
or polyester. In addition, one or more loops of the coil may be
soldered or welded together, which may reduce stretching during
movement of the coil.
[0106] FIG. 26A shows a cross-section, side-view of an embodiment
in which arm-like structures 73 extending from the proximal region
of the coil 10 engage a pusher element 31 in slots containing an
electroactive polymer 20 in an unexpanded configuration. FIG. 26B
shows the assembly when the electroactive polymer 20 expands and
the arms 73 no longer engage the pusher element 31. Pusher element
31 includes an electrical conductor 32 for activation of the
electroactive polymer 20.
[0107] The arms may be made of any material (e.g., polymer and/or
metal) and may be integral or attached to the implantable device.
Although depicted in FIG. 26 with two arms, more than 2 arms may be
employed and may improve tensile strength, for example, 3, 4, 5, 6
or even more arms. The grips may also be of any configuration that
engages the arms and may be built into the tubular pusher or may be
attached to the distal end of pusher. The pusher can be made from
any material, for example nitinol. The pusher body may optionally
comprise a metallic hypotube component that is flexible distally; a
polymer jacket/liner; and/or a metal reinforced polymer structure.
Additional elements, for example, radiopaque markers, may also be
included on the pusher element.
[0108] FIG. 27A shows a cross-section, side-view of an embodiment
in which the electroactive polymer 20 is a ring attached to the
proximal region of the coil 10 and which engages a pusher element
31 in the unexpanded configuration. FIG. 27B shows the assembly
when the electroactive polymer 20 expands and the diameter of the
ring increases so it no longer engages the pusher element 31 and
the coil 10 is detached. Pusher element 31 includes an electrical
conductor 32 for activation of the electroactive polymer 20 and
optionally includes a slot or groove adapted to fit the ring of
electroactive polymer 20. FIG. 27C shows a cross-section of an
exemplary electroactive polymer ring 20 may be made up of multiple
discontinuous electroactive polymer elements in an unexpanded
state. FIG. 27D shows the electroactive polymer ring structure 20
of FIG. 27C after linear expansion of the electroactive polymer
ring.
[0109] FIG. 28 to 30 show cross-section, side-views of additional
embodiments in which the implantable device 10 engages a pusher
element 31 when the electroactive polymer 20 is in a contracted
position. FIG. 287A shows a ball 73 structure on the proximal end
of the coil 10 engaged by arms 74 when the electroactive polymer 20
is contracted. FIG. 28B shows release of the ball joint when the
electroactive polymer 20 is expanded. FIG. 29A shows an assembly
where arms 74 on the pusher element 31 engage a ring structure 73
on the coil 10 when the electroactive polymer 20 is in the
contracted position. FIG. 29B shows the assembly when the
electroactive polymer 20 expands and the arms 74 no longer engage
the ring 73. FIG. 30A shows an assembly where the unexpanded
electroactive polymer 20 engages a structure 73, 73a on the
proximal end of the coil 10 embodiment distal to the enlarged end
73 of the structure. FIG. 30B shows the assembly upon expansion of
the electroactive polymer 20 to release the structure 73, 73a and
attached coil 10. FIG. 30C is a top view of the structure 73, 73a
extending from the implantable coil and electroactive polymer 20 in
unexpanded configuration and shows the polymer 20 can be made into
panels to promote radial expansion. FIG. 30D is a top view of the
structure shown in FIG. 30C with the electroactive polymer panels
in the expanded configuration.
[0110] FIG. 31 shows an embodiment that includes a coupling
receiver 79 extending from a delivery device 30. As shown in FIG.
31A, the coupling receiver 79 comprises an electroactive polymer or
electroactive strip (e.g. electroactive wire) 20 that engages a
coupling device 73 extending from the implantable device 10 when
the electroactive polymer/strip 20 is in an expanded configuration
(e.g., activated). The electroactive polymer 20 releases the
coupling device 73 in the unexpanded (e.g., deactivated). The
coupling receiver 79 and coupling device 73 may be of any
configuration. Similarly, the electroactive polymer 20 may a
ring-like structure with or without channels therein, for example
as shown in FIG. 9B. In other embodiments, the device includes an
electroactive wire, for example a nickel titanium shape memory or
superelastic wire that responds to heat activation via electric
current (see, also, FIGS. 12 and 13). Designs with a coupling
mechanism may enhance the ability of the operator to reposition and
manipulate the device during implantation. For example, the
delivery device and detaching device may be able to rotate as much
as 1 to 1 torque and/or independent of each other.
[0111] FIG. 32 shows a compression (hydraulic) type detachment
mechanism including a tubular pusher element made up of an
incompressible material 31 and an electroactive polymer 20.
Typically, the incompressible material 31 also acts as an
electrolyte. The coil 10 is engaged with the tubular pusher element
when the electroactive polymer is in the unexpanded configuration,
for example by an interference fit. FIG. 32A shows the assembly
when the electroactive polymer 20 is in the unexpanded
configuration. Upon volumetric expansion of the electroactive
polymer 20 the pressure inside the tubular pusher increases until
the coil 10 is released.
[0112] FIG. 33A shows a cross-section, side-view of an embodiment
in which a T-bar structure 84 engages fin-like structures 87
attached to the implantable coil 10. Also shown is an electrical
conductor 32 for activation of the electroactive polymer 20.
Typically, the fin-like structures 87 are attached to the
implantable device (e.g., the interior of a coil) and include
apertures through which the T-bar structure 84 extends. An
electroactive polymer 20 is disposed on the T-bar 84 such that, in
the contracted position, the T-bar 84 engages the fin-like
structures 87 extending from the implantable device 10. FIG. 33B
shows the assembly when the electroactive polymer 20 expands
causing the fin-like structures 87 to extend beyond the ends of the
T-bar 84 so that the T-bar 84 no longer engages the device 10.
[0113] FIGS. 34A and 34B show an alternative embodiment, in which
the T-bar structure 84 is attached to the implantable device 10 and
engages structures 87 proximal to the implantable device 10. As
with the embodiment shown in FIG. 33, expansion of the
electroactive polymer 20 pushes the fins off the T-bar and releases
the implantable device 10 from the pusher element (FIG. 34B).
[0114] The T-bar may not be a single T in that any number of posts
can be used, for example, 1, 2, 3, 4, 5 or even more posts can be
used. In a preferred embodiment, the T-bar includes 2 posts.
[0115] Furthermore, the T-bar and structures (e.g., fin-like
structures) it engages may be made of any material (e.g., polymer
and/or metal). In certain embodiments, the fin-like structures
comprise platinum. In other embodiments, the T-bar comprises
platinum, nitinol, stainless steel and/or polyimide and can be
electrochemically etched or formed by bending segments of wire. The
fin-like structures or T-bar may be attached to the implant by any
suitable means, including but not limited to soldering, welding,
adhesives, etc. An optional collar may be placed around the finds
and/or T-bar to reduce or prevent pivoting of the fins about the
T-bar structure.
[0116] FIG. 35 shows an exemplary embodiment in which a structural
element (e.g. sphere or ovoid ball like structure) is secured at or
near the proximal end of the coil 10 and into delivery device 30
(e.g., hypotube) where it is held in place by electroactive polymer
20 in an expanded configuration. When the polarity of current
applied to the electroactive polymer 20 is reversed via electrodes
32, the polymer expands linearly such that it no longer secures the
device 10 within the delivery device 30. Also shown is optional
groove or slot in the delivery device 37 that provides a seating
location of the proximal coil ball.
[0117] In any of the embodiments described herein, the
electroactive polymer 20 can be disposed directly on the delivery
device or on a flexible substrate 38, for example a flexible
substrate that deflects when the electroactive polymer 20 disposed
therein is activated/unactivated by electrical current (see, e.g.,
description above regarding FIGS. 13A and B).
[0118] The devices described herein are often introduced into a
selected site using the procedure outlined below. This procedure
may be used in treating a variety of maladies. For instance in the
treatment of an aneurysm, the aneurysm itself will be filled
(partially or fully) with the compositions described herein.
[0119] Conventional catheter insertion and navigational techniques
involving guidewires or flow-directed devices may be used to access
the site with a catheter. The mechanism will be such as to be
capable of being advanced entirely through the catheter to place
vaso-occlusive device at the target site but yet with a sufficient
portion of the distal end of the delivery mechanism protruding from
the distal end of the catheter to enable detachment of the
implantable vaso-occlusive device. For use in peripheral or neural
surgeries, the delivery mechanism will normally be about 100-200 cm
in length, more normally 130-180 cm in length. The diameter of the
delivery mechanism is usually in the range of 0.25 to about 0.90
mm. Briefly, occlusive devices (and/or additional components)
described herein are typically loaded into a carrier for
introduction into the delivery catheter and introduced to the
chosen site using the procedure outlined below. This procedure may
be used in treating a variety of maladies. For instance, in
treatment of an aneurysm, the aneurysm itself may be filled with
the embolics (e.g. vaso-occlusive members and/or liquid embolics
and bioactive materials) which cause formation of an emboli and, at
some later time, is at least partially replaced by neovascularized
collagenous material formed around the implanted vaso-occlusive
devices.
[0120] A selected site is reached through the vascular system using
a collection of specifically chosen catheters and/or guide wires.
It is clear that should the site be in a remote site, e.g., in the
brain, methods of reaching this site are somewhat limited. One
widely accepted procedure is found in U.S. Pat. No. 4,994,069 to
Ritchart, et al. It utilizes a fine endovascular catheter such as
is found in U.S. Pat. No. 4,739,768, to Engelson. First of all, a
large catheter is introduced through an entry site in the
vasculature. Typically, this would be through a femoral artery in
the groin. Other entry sites sometimes chosen are found in the neck
and are in general well known by physicians who practice this type
of medicine. Once the introducer is in place, a guiding catheter is
then used to provide a safe passageway from the entry site to a
region near the site to be treated. For instance, in treating a
site in the human brain, a guiding catheter would be chosen which
would extend from the entry site at the femoral artery, up through
the large arteries extending to the heart, around the heart through
the aortic arch, and downstream through one of the arteries
extending from the upper side of the aorta. A guidewire and
neurovascular catheter such as that described in the Engelson
patent are then placed through the guiding catheter. Once the
distal end of the catheter is positioned at the site, often by
locating its distal end through the use of radiopaque marker
material and fluoroscopy, the catheter is cleared and/or flushed
with an electrolyte solution.
[0121] Once the selected site has been reached, the vaso-occlusive
device is extruded using a pusher-detachment mechanism as described
herein and released in the desired position of the selected
site.
[0122] Modifications of the procedure and vaso-occlusive devices
described above, and the methods of using them in keeping with this
disclosure will be apparent to those having skill in this
mechanical and surgical art. These variations are intended to be
within the scope of the claims that follow.
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