U.S. patent application number 10/850995 was filed with the patent office on 2004-11-04 for implantable devices with polymeric detachment junction.
This patent application is currently assigned to Scimed Life Systems, Inc.. Invention is credited to Eder, Joseph C..
Application Number | 20040220563 10/850995 |
Document ID | / |
Family ID | 24868540 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040220563 |
Kind Code |
A1 |
Eder, Joseph C. |
November 4, 2004 |
Implantable devices with polymeric detachment junction
Abstract
The invention includes implantable devices, such as
vaso-occlusive coils and stents, comprising a junction member
linking the device to a delivery mechanism. The junction member is
melted or severed from the implantable using low frequency energy
or direct current (DC).
Inventors: |
Eder, Joseph C.; (Los Altos
Hills, CA) |
Correspondence
Address: |
ROBINS & PASTERNAK
1731 EMBARCADERO ROAD
SUITE 230
PALO ALTO
CA
94303
US
|
Assignee: |
Scimed Life Systems, Inc.
|
Family ID: |
24868540 |
Appl. No.: |
10/850995 |
Filed: |
May 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10850995 |
May 20, 2004 |
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09714038 |
Nov 15, 2000 |
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6743251 |
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Current U.S.
Class: |
606/41 ;
606/1 |
Current CPC
Class: |
A61B 2017/12068
20130101; A61B 17/12022 20130101; A61B 17/1214 20130101 |
Class at
Publication: |
606/041 ;
606/001 |
International
Class: |
A61B 017/00 |
Claims
1. An assembly comprising: (a) an implantable device; (b) a
deployment mechanism; and (c) a junction member linking the
implantable device and deployment mechanism, wherein the junction
member is detached from the implantable device by application of
direct current.
2. The assembly of claim 1, wherein the junction member comprises a
thermoplastic polymer.
3. The assembly of claim 2, wherein the thermoplastic polymer is
PVA.
4. to 5. (canceled).
6. The assembly of claim 1, wherein the deployment mechanism
comprises a conductive wire.
7. The assembly of claim 1, wherein the implantable device
comprises a vasoocclusive coil.
8. The assembly of claim 1, wherein the implantable device
comprises a stent.
9. The assembly of claim 1, further comprising (d) a source of
direct current attached to the delivery mechanism.
10. The assembly of claim 1, further comprising: (d) a conductive
member in operable contact with the junction member.
11. The assembly of claim 10, further comprising (e) a source of
direct current attached to the conductive member.
12. The assembly of claim 1, further comprising a catheter, said
assembly being disposed within the catheter.
13. The assembly of claim 12, further comprising a negative
electrode at the distal tip of the catheter.
14. A method of introducing an implantable device into a subject,
the method comprising: (a) introducing an assembly according to
claim 1 into the subject; and (b) detaching the implantable device
by applying direct current.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the field of implantable devices.
More particularly, it relates to detaching the implantable device
from the delivery mechanism using low frequency energy or direct
current (DC) to melt or sever the polymeric junction between the
device and delivery mechanism.
BACKGROUND
[0002] There are a variety of implantable devices that require
precise placement within the vasculature of the human body. Such
devices include vaso-occlusive coils, stents and other
three-dimensional devices. Vaso-occlusive coils are described, for
example, in U.S. Pat. No. 4,994,069, to Ritchart et al.; U.S. Pat.
No. 5,624,461 to Mariant; U.S. Pat. No. 5,639,277 to Mariant et al.
and U.S. Pat. No. 5,649,949 to Wallace et al. describes variable
cross-section conical vaso-occlusive coils. Stents are described,
for example, in U.S. Pat. No. 4,655,771 to Wallsten; U.S. Pat. No.
4,954,126 to Wallsten and U.S. Pat. No. 5,061,275 to Wallsten et
al.
[0003] Typically, implantable devices include a detachment
mechanism in order to be released from the deployment mechanism
(e.g., attached wire). Several classes of techniques have been
developed to enable more accurate placement of implantable devices
within a vessel. One class involves the use of electrolytic means
to detach the vasoocclusive member from the pusher. In one
technique (U.S. Pat. No. 5,122,136 to Guglielmi et al.) the
vasoocclusive member is bonded via a metal-to-metal joint to the
distal end of the pusher. The pusher and vasoocclusive member are
made of dissimilar metals. The vasoocclusive member-carrying pusher
is advanced through the catheter to the site and a low electrical
current is passed through the pusher-vasoocclusive member assembly.
The current causes the joint between the pusher and the
vasoocclusive member to be severed via electrolysis. The pusher may
then be retracted leaving the detached vasoocclusive member at an
exact position within the vessel. In addition to enabling more
accurate vasoocclusive member placement, the electric current may
facilitate thrombus formation at the vasoocclusive member site. The
only perceived disadvantage of this method is that the electrolytic
release of the vasoocclusive member requires a period of time so
that rapid detachment of the vasoocclusive member from the pusher
does not occur. Other examples of this technique can be found in
U.S. Pat. No. 5,423,829 to Pham et al. and U.S. Pat. No. 5,522,836
to Palermo.
[0004] Other forms of energy are also used to sever sacrificial
joints that connect pusher and vasoocclusive member apparatus. An
example is that shown in Japanese Laid-Open Patent Application No.
7-265431 or corresponding U.S. Pat. No. 5,759,161 and U.S. Pat. No.
5,846,210 to Ogawa et al. A sacrificial connection member,
preferably made from polyvinylacetate (PVA), resins, or shape
memory alloys, joins a conductive wire to a detention member. Upon
heating by a monopolar high frequency current, the sacrificial
connection member melts, severing the wire from the detention
member. U.S. Pat. No. 5,944,733 to Engelson describes application
of radiofrequency energy to sever a themoplastic joint.
[0005] In U.S. Pat. No. 4,735,201 to O'Reilly, an optical fiber is
enclosed within a catheter and connected to a metallic tip on its
distal end by a layer of hot-melt adhesive. The proximal end of the
optical fiber is connected to a laser energy source. When
endovascularly introduced into an aneurysm, laser energy is applied
to the optical fiber, heating the metallic tip so as to cauterize
the immediately surrounding tissue. The layer of hot-melt adhesive
serving as the bonding material for the optical fiber and metallic
tip is melted during this lasing, but the integrity of the
interface is maintained by application of back pressure on the
catheter by the physician. When it is apparent that the proper
therapeutic effect has been accomplished, another pulse of laser
energy is then applied to once again melt the hot-melt adhesive,
but upon this reheating the optical fiber and catheter are
withdrawn by the physician, leaving the metallic tip in the
aneurysm as a permanent plug.
[0006] Other methods for placing implantable devices within the
vasculature utilize heat releasable bonds that can be detached by
using laser energy (see, U.S. Pat. No. 5,108,407). EP 0 992 220
describes an embolic coil placement system which includes
conductive wires running through the delivery member. When these
wires generate sufficient heat, they are able to sever the link
between the embolic coil and the delivery wires. Further, U.S. Ser.
No. 09/177,848 describes the use of fluid pressure (e.g.,
hydraulics) to detach an embolic coil.
[0007] A variety of mechanically detachable devices are also known.
For instance, U.S. Pat. No. 5,234,437, to Sepetka, shows a method
of unscrewing a helically wound coil from a pusher having
interlocking surfaces. U.S. Pat. No. 5,250,071, to Palermo, shows
an embolic coil assembly using interlocking clasps mounted both on
the pusher and on the embolic coil. U.S. Pat. No. 5,261,916, to
Engelson, shows a detachable pusher-vaso-occlusive coil assembly
having an interlocking ball and keyway-type coupling. U.S. Pat. No.
5,304,195, to Twyford et al., shows a pusher-vaso-occlusive coil
assembly having an affixed, proximally extending wire carrying a
ball on its proximal end and a pusher having a similar end. The two
ends are interlocked and disengage when expelled from the distal
tip of the catheter. U.S. Pat. No. 5,312,415, to Palermo, also
shows a method for discharging numerous coils from a single pusher
by use of a guidewire which has a section capable of
interconnecting with the interior of the helically wound coil. U.S.
Pat. No. 5,350,397, to Palermo et al., shows a pusher having a
throat at its distal end and a pusher through its axis. The pusher
sheath will hold onto the end of an embolic coil and will then be
released upon pushing the axially placed pusher wire against the
member found on the proximal end of the vaso-occlusive coil.
[0008] None of these documents disclose devices having detachment
junctions that are detachable by applying low frequency or direct
current.
SUMMARY OF THE INVENTION
[0009] The present invention includes compositions and methods for
detaching implantable devices from deployment mechanisms using
low-frequency energy or direct current.
[0010] In one aspect, the invention includes an assembly comprising
(a) an implantable device; (b) a deployment mechanism; and (c) a
junction member linking the implantable device and deployment
mechanism. The junction member is detached from the implantable
device by application of low-frequency energy or direct current,
for example a thermoplastic polymer such as PVA. In certain
embodiments, the low frequency or direct current is less than 100
kHz, preferably less than 80 Hz. The deployment mechanism can
comprise, for example, a conductive wire. The implantable device
can comprise, for example, a vasoocclusive coil or a stent.
[0011] In other aspects, any of the devices and/or assemblies
described herein further include a source of low frequency energy
or direct current attached to the delivery mechanism and/or a
conductive member in operable contact with the junction member. In
other embodiments, the assembly devices described herein further
comprise a catheter, said assembly being disposed within the
catheter. Further, the catheter may include a negative electrode at
the distal tip of the catheter.
[0012] In other aspects, methods of using the assembly devices are
provided, for example introducing an assembly as described herein
into a subject and detaching the implantable device in the desired
location by applying low frequency energy or direct current.
[0013] These and other embodiments of the subject invention will
readily occur to those of skill in the art in light of the
disclosure herein.
DESCRIPTION OF THE INVENTION
[0014] Implantable devices, such as coils or stents, with
detachable junctions to delivery mechanisms are described. Thus,
the devices include junction members which link the device to the
deployment mechanism. The junction members are readily detachable
by the imposition of low frequency energy (or direct current) by
the operator when the device is in the desired position. Methods of
making and using these devices also form an aspect of this
invention.
[0015] Advantages of the present invention include, but are not
limited to, (i) increasing the precision of placement of
implantable devices; (ii) decreasing the time needed for separation
of implant from delivery mechanism; (iii) providing implant
delivery systems that require only one delivery wire; (iii)
providing implant delivery systems that can be used with flexible
catheters; and (iv) providing methods and materials for making
these detachable devices.
[0016] All publications, patents and patent applications cited
herein, whether supra or infra, are hereby incorporated by
reference in their entirety.
[0017] 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 junction member" includes a one
or more junction members on a single device.
[0018] The low-frequency energy or DC severable junctions described
herein can be used in the manufacturing of a wide variety of
implantable devices, including but not limited to stents and
vaso-occlusive devices such as coils. Other implantable devices
will also be advantageously employed with the junctions described
herein.
[0019] A junction member is fixedly attached to the implant and to
the delivery mechanism (e.g., a wire, pusher, etc.). The sites of
attachment can be determined based on the use of the implant and
the desired final, deployed configuration. Thus, in certaine
embodiments, the junction member is attached to just one location
on both the implant and the delivery mechanism, for example, on or
near the proximal end of the implant and on or near the distal end
of the delivery mechanism. For purposes of this invention, the term
"engaged" is herein used to describe any mechanical or physical
attachment, interlocking, mating, binding, coupling, hooking, etc.,
such that members that are said to be "engaged" do not come apart
or detach from one another without some positive effort,
application of energy, or the like.
[0020] The junction member is preferably a thermoplastic member
that melts or sufficiently weakens upon application of low
frequency energy or direct current (DC). As will be apparent to
those of skill in the art, the junction member need not melt
completely in order to be severable from the implantable device.
The junction member need only melt sufficiently that the operator
can remove the delivery mechanism.
[0021] The thermoplastic junction member can be made using any
conventional technique, for example by substantially coating the
desired cleavage of a junction of implant and delivery mechanism.
One technique, for example, is dipping or coating the implant and
delivery mechanism in molten or substantially softened
thermoplastic material, but other techniques as known in the art,
such as shrink-wrapping, spraying on in the form of a suspension or
latex, or others may be used as well. Other conventional
techniques, such as line of sight spray deposition, may also be
used. Once a sufficient thickness of the thermoplastic junction
member has been obtained, the implantable device and delivery
mechanism are linked via this junction member. In certain
instances, the entire surface of implant and/or delivery mechanism
is substantially to electrically insulate to limit the heating
effect of the energy applied during deployment of implant.
[0022] In some embodiments, preferably prior to the passing of time
to allow substantial hardening of the thermoplastic material, the
junctions are physically engaged to form the delivery assembly
prior to insertion of the assembly inside a catheter. The delivery
assembly can include implantable member, delivery wire, sleeve,
catheter, etc.
[0023] No limitation is imposed on the material for the junction
member so long as it does not adversely affect the patient's body
and can be severed by application of low frequence energy or DC
current. Thus, any suitable, biologically inert thermoplastic
polymer can be used in the junction members described herein. A
preferred thermoplastic material is polyvinylacetate (PVA). The
polymer also has the proper transition properties (e.g.,
temperature or current at which is becomes severable). Suitable
detachment conditions are any conditions which allow for the safe,
efficient, and reliable detachment of the implantable device from
the delivery mechanism. Examples of such other thermoplastics that
may be used singly or in combination include, but are not limited
to, materials such as polyactide, polyglycolide,
polyactide-co-glycolide polydioxanone, polyethylene,
polyiminocarbonates, polycaprolactone, polyesters and the like.
U.S. Pat. No. 5,292,321 to Lee discusses such suitable
thermoplastic materials.
[0024] The thermoplastic junction member may take on a variety of
thicknesses and coverage configurations depending upon a number of
factors such as the type of implant, the degree of control over the
release of the implantable device into the selected site desired by
the user, the types and combinations of materials used, dimensional
constraints of the catheter and sheath, and so forth. Typically,
the diameter of the junction member is between about 0.1-0.5 mm and
the length anywhere from about 1 to 10 mm. For all configurations,
it is desired that the thermoplastic member have a thickness that
will not prohibit the engaged junctions from freely moving within a
catheter sheath or other associated equipment necessary to
accomplish the desired objective of reliably and safely placing a
implantable device at a selected site.
[0025] An energy source is connected to the junction member, for
example via the delivery wire. The thermoplastic junction member is
sufficiently melted and/or severed by application of a
low-frequency energy or direct current, thereby detaching the
implantable device from the delivery mechanism (e.g., wire). The
low-frequency energy of DC does not adversely affect the subject
and is typically between about 1 and 100 kHz, including any integer
value therebetwen. Preferably, the low-frequency energy or direct
current is below about 100 kHz, more preferably below about 80 kHz
and even more preferably below about 50 kHz.
[0026] As noted above, the implantable member can be any suitable
implantable device. The implant is desirably made up of a
radiopaque, physiologically compatible material. For instance, the
material may be platinum, gold, tungsten, or alloys of these.
Certain polymers are also suitable for use in the implants, either
alone or in conjunction with metallic markers providing
radiopacity. These materials are chosen so that the procedure of
locating the implant within the vessel may be viewed using
radiography. However, it is also contemplated that the implantable
device may be made of various other biologically inert polymers or
of carbon fiber.
[0027] When the implantable member is a coil, its shape and
constituent winding will depend upon the use to which the coil will
be placed. For occluding peripheral or neural sites, the coils will
typically be made of 0.05 to 0.15 mm diameter wire (platinum or
platinum/tungsten alloy) that may be wound to have an inner
diameter of 0.15 to 1.5 mm with a minimum pitch--that is to say
that the pitch is equal to the diameter of the wire used in the
coil. The outer diameter is then typically between 0.25 mm to 1.8
mm. The length of the coil will normally be in the range of 0.5 to
60 cm, preferably 0.5 to 40 cm. A discussion of this variation may
be found, for example, in U.S. Pat. No. 4,994,069 to Ritchart et
al.
[0028] Conventional catheter insertion and navigational techniques
involving guidewires or flow-directed devices may be used to access
the site with a catheter. Briefly, the implantable devices having
polymeric detachable junctions 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 mechanical devices which cause
formation of an emboli and, at some later time, is at least
partially replaced by neovascularized collagenous material formed
around the implanted devices.
[0029] A selected site is reached through the vascular system using
a collection of specifically chosen catheters and 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 as a unit. 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. For instance, if
a guidewire has been used to position the catheter, it is withdrawn
from the catheter and then the assembly, for example including the
implantable device at the distal end, is advanced through the
catheter. The device is advanced past the distal end of the
catheter so that it is free and positioned precisely at the desired
treatment-site.
[0030] The length of delivery mechanism will be such as to be
capable of being advanced entirely through the catheter to place
implantable 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 device. For use in peripheral or neural surgeries, the
delivery mechanism will normally 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.
[0031] Once the implantable device is at the selected site, low
frequency energy or direct current is then supplied by the energy
source and transmitted through the delivery mechanism to polymeric
junction member so to sufficiently melt the thermoplastic polymer
above its transition temperature until it is sufficiently softened
or dissipated to free the junction member from the implantable
device. Alternatively, a component that acts as a conductor (e.g.,
a conductive wire) can be inserted through the catheter alongside
the delivery mechanism and the low frequency energy transmitted
through it to melt the thermoplastic junction. In either case,
following severing of the implantable device, the entire catheter
may then be removed or the delivery mechanism may be withdrawn from
the catheter lumen to provide for installation of other implantable
devices. If additional implants are to be placed at the target
site, the procedure is repeated. After the desired number of
implants have been placed at the site, the catheter is withdrawn
from the vessel.
[0032] Prior to the formation of assembly, it is desired to ensure
that the thermoplastic material forming thermoplastic member coats
substantially the entire surface of the junction member where it
intersects both the implant and delivery mechanism junctions. This
aids in electrically insulating the combination delivery
mechanism-implantable device assembly. Electrical insulation helps
to limit the heating effect of the energy, applied to soften the
thermoplastic member, to the joined implantable device and delivery
mechanism in the immediate vicinity of the thermoplastic member and
to avoid excessive undesirable heating of the delivery mechanism
and the implantable device. This concept is described in a
different context in U.S. Pat. No. 5,743,905 to Eder et al., issued
Apr. 28, 1998.
[0033] Alternatively, if it is desired to further protect the
assembly from heating effects during detachment, an additional
electrical insulating member may be affixed to the proximal section
of delivery mechanism. If such an additional insulating member is
used, it is desired, but not necessary, that it consist of an
electrically insulating polymer material and/or thickness different
from that of the thermoplastic member such that the thermoplastic
member preferentially absorbs the energy applied during detachment
by the energy source. The insulating material can be a polymer such
as polyethylene, polypropylene, polyurethane, polyethylene
terephthalate, polyvinylchloride, and is preferably a polymer from
the class of polymers generally known as parylene. The insulation
may be applied to the proximal end of delivery mechanism by a
number of processes such as shrink-wrapping, dipping in molten
polymer, spraying on in the form of a suspension or latex, or the
like. The axial length of the additional insulating member and its
thickness may vary depending upon the degree of additional
electrical insulation desired, the specific configuration of the
assembly, the application for which assembly is used, etc.
[0034] Modifications of the procedure and device described above,
and the methods of using them in keeping with this invention 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.
* * * * *