U.S. patent application number 10/241426 was filed with the patent office on 2003-01-16 for fast detaching electrically isolated implant.
This patent application is currently assigned to SCIMED Life Systems, Inc.. Invention is credited to Bashiri, Mehran, Eder, Joseph C., Engelson, Erik T., Pham, Pete Phong, Roue, Chad C., Thach, Cong, Wallace, Michael P..
Application Number | 20030014073 10/241426 |
Document ID | / |
Family ID | 27129819 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030014073 |
Kind Code |
A1 |
Bashiri, Mehran ; et
al. |
January 16, 2003 |
Fast detaching electrically isolated implant
Abstract
This is an implant for placement in the human body and an
assembly for so placing that implant. Most desirably, it is an
implant for use in the vasculature of the human body and is used to
occlude some space in that vasculature as a portion of a treatment
regimen. The implant itself is preferably a component of a
deployment device using an electrolytically severable joint. The
implant is electrically isolated from the electrolytically
severable joint by a highly resistive or insulative layer. Such
isolation and minimization of the conductive pathway from the
placement apparatus to the body's fluids appears to enhance the
susceptibility of the electrolytic joint to quick erosion and
detachment of the implant from the deployment media. Although the
implant itself is preferably a vaso-occlusive device, it may
instead be a stent, a vena cava filter, or other implant which may
be installed in this manner.
Inventors: |
Bashiri, Mehran; (San
Carlos, CA) ; Wallace, Michael P.; (Pleasanton,
CA) ; Pham, Pete Phong; (Fremont, CA) ; Thach,
Cong; (Fremont, CA) ; Roue, Chad C.; (Fremont,
CA) ; Eder, Joseph C.; (Los Altos Hills, CA) ;
Engelson, Erik T.; (Menlo Park, CA) |
Correspondence
Address: |
Bingham McCutchen, LLP
Suite 1800
Three Embarcadero
San Francisco
CA
94111-4067
US
|
Assignee: |
SCIMED Life Systems, Inc.
Maple Grove
MN
|
Family ID: |
27129819 |
Appl. No.: |
10/241426 |
Filed: |
September 10, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10241426 |
Sep 10, 2002 |
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09644244 |
Aug 22, 2000 |
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6468266 |
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09644244 |
Aug 22, 2000 |
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09144950 |
Sep 1, 1998 |
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6165178 |
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09144950 |
Sep 1, 1998 |
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08941458 |
Sep 30, 1997 |
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5984929 |
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08941458 |
Sep 30, 1997 |
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08921407 |
Aug 29, 1997 |
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Current U.S.
Class: |
606/200 |
Current CPC
Class: |
A61F 2002/016 20130101;
A61F 2230/0091 20130101; A61B 17/1215 20130101; A61F 2230/0069
20130101; A61F 2/0105 20200501; A61B 17/12113 20130101; A61F
2230/0006 20130101; A61B 2017/12063 20130101; A61B 17/12022
20130101; A61F 2/011 20200501; A61F 2/95 20130101; A61B 17/12154
20130101; A61F 2002/9505 20130101; A61F 2230/005 20130101; A61B
17/12145 20130101 |
Class at
Publication: |
606/200 |
International
Class: |
A61M 029/00 |
Claims
We claim as our invention:
1. An implant assembly for placement of an implant in the human
body comprising: an implant, a wire having an electrolytically
severable joint, the wire attached to a proximal end of the
implant, the electrolytically severable joint being relatively more
susceptible to electrolysis in an ionic solution than is the
implant, and an anchoring member disposed distally of the joint and
attached to the implant, wherein the implant is electrically
isolated from the electrolytically severable joint.
2. The implant assembly of claim 1 wherein the electrical isolation
is due to an insulative or highly resistive layer interposed
between the implant and the electrolytically severable joint.
3. The implant assembly of claim 2 wherein the insulative or highly
resistive layer comprises a polymer.
4. The implant assembly of claim 2 wherein the insulative or highly
resistive layer comprises an oxide forming material.
5. The implant assembly of claim 1 wherein the implant comprises a
helically wound coil.
6. The implant assembly of claim 5 wherein the helically wound coil
is further wound into a secondary shape.
7. The implant assembly of claim 6 wherein the secondary shape is
helical.
8. The implant assembly of claim 7 wherein the secondary shape is
conical.
9. The implant assembly of claim 6 wherein the helically wound coil
self-forms into the secondary shape when unconstrained.
10. The implant assembly of claim 5 wherein the helically wound
coil is further wound into two secondary shapes having differing
secondary shape diameters.
11. An implant assembly for placement of an implant in the human
body comprising: a vaso-occlusive implant, a wire having an
electrolytically severable joint, the wire attached to a proximal
end of the implant, the electrolytically severable joint being
relatively more susceptible to electrolysis in an ionic solution
than is the implant, an anchoring member disposed distally of the
joint and attached to the implant via a stretch resistant member,
wherein the implant is electrically isolated from the
electrolytically severable joint.
12. The implant assembly of claim 11 wherein the stretch resistant
member comprises a material selected from the group consisting of
polyethylene, polypropylene, polyamides, and
polyethyleneterephthalate.
13. The implant assembly of claim 11 wherein the vaso-occlusive
implant comprises a helical coil.
14. The implant assembly of claim 11 wherein a distal end of the
wire is covered with a first insulative or highly resistive layer
and the wire distal end is attached to the implant member proximal
end by a second insulative or highly resistive layer.
15. The implant assembly of claim 1 wherein the electrical
isolation is due to an insulative or highly resistive layer
interposed between the implant and the electrolytically severable
joint.
16. An implant assembly for placement of an implant in the human
body comprising: a vaso-occlusive coil, a wire having an
electrolytically severable joint, the wire affixed to a proximal
end of the coil, the electrolytically severable joint being
relatively more susceptible to electrolysis in an ionic solution
than is the coil, and an anchoring member disposed distally of the
joint and affixed to the coil, the anchoring member comprising a
loop affixed to a stretch resistant member, the stretch resistant
member affixed to the coil, wherein the coil is electrically
isolated from the electrolytically severable joint.
17. The implant assembly of claim 16 additionally comprising a
polymeric region disposed (a) distally of the anchoring member and
(b) at least partially in a proximal portion of the coil.
18. The implant assembly of claim 16 wherein the anchoring member
has a diameter that is larger than a diameter of a lumen of the
coil so that a portion of the anchoring member is prevented from
passing through the coil lumen upon application of force on the
coil.
19. The implant assembly of claim 16 additionally comprising a
radiopaque coil disposed on the wire distal of the electrolytically
severable joint.
20. The implant assembly of claim 19 wherein a distal portion of
the wire and at least a portion of the radiopaque coil is attached
to the anchoring member and the coil via an insulative or highly
resistive member disposed distal to the joint.
Description
RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
09/144,950, filed Sep. 1, 1998, now pending, which is a
continuation-in-part of U.S. Pat. No. 5,984,929, which is a
continuation-in-part of U.S. patent application Ser. No.
08/921,407, filed Aug. 29, 1997, now abandoned; the entirety of
each is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention is an implant for placement in the human body
and an assembly for so placing that implant. Most desirably, it is
an implant for use in the vasculature of the human body and is used
to occlude some space in that vasculature as a portion of a
treatment regimen. The implant itself is preferably a component of
a deployment device or assembly using an electrolytically severable
joint. The implant is electrically isolated from the
electrolytically severable joint by a highly resistive or
insulative layer. Such isolation and minimization of the conductive
pathway from the placement apparatus to the body's fluids appears
to enhance the susceptibility of the electrolytic joint to quick
erosion and detachment of the implant from the deployment media.
Although the implant itself is preferably a vasoocclusive device,
it may instead be a stent, a vena cava filter, or other implant
which may be installed in this manner.
BACKGROUND OF THE INVENTION
[0003] Implants may be placed in the human body for a wide variety
of reasons. For instance, stents are placed in a number of
different lumens in the body. They may be placed in arteries to
cover vascular lesions or to provide patency to the vessel. Stents
are also placed in biliary ducts to prevent them from kinking or
collapsing. Grafts may be used with stents to promote growth of
endothelial tissue within those vessels.
[0004] Vena cava filters are implanted in the body, typically in
the vena cava, to catch thrombus which are sloughed off from other
sites within the body and which may be in the blood passing through
the chosen site.
[0005] Vaso-occlusive devices or implants are used for a wide
variety of reasons. They are often used for treatment of
intra-vascular aneurysms. This is to say that the treatment
involves the placement of a vaso-occlusive device in an aneurysm to
cause the formation of a clot and eventually of a collagenous mass
containing the vasoocclusive device. These occlusions seal and fill
the aneurysm thereby preventing the weakened wall of the aneurysm
from being exposed to the pulsing blood pressure of the open
vascular lumen.
[0006] Treatment of aneurysms in this fashion is a significant
improvement over the surgical method typically involved. The
surgical or extravascular approach is a common treatment of
intra-cranial berry aneurysm; it is straightforward but fairly
traumatic. The method involves removing of portion of the cranium
and locating the aneurysm. The neck of the aneurysm is closed
typically by applying a specially sized clip to the neck of the
aneurysm. The surgeon may choose to perform a suture ligation of
the neck or wrap the entire aneurysm. Each of these procedures is
performed by an very intrusive invasion into the body and is
performed from the outside of the aneurysm or target site. General
anesthesia, craniotomy, brain retraction, and a placement of clip
around the neck of the aneurysm all are traumatic. The surgical
procedure is often delayed while waiting for the patient to
stabilize medically. For this reason, many patients die from the
underlying disease prior to the initiation of the surgical
procedure.
[0007] Another procedure--the extra--intravascular
approach--involves surgically exposing or stereotaxically reaching
an aneurysm with a probe. The wall of the aneurysm is perforated
from the outside and various techniques are used to occlude the
interior of the aneurysm to prevent its rebleeding. The techniques
used to occlude the aneurysm include electro-thrombosis, adhesive
embolization, hoghair embolization, and ferromagnetic thrombosis.
These procedures are discussed in U.S. Pat. No. 5,122,136 to
Guglielmi et al., the entirety of which is incorporated by
reference.
[0008] Guglielmi et al. further describes an endovascular procedure
which is at once the most elegant and least invasive. The procedure
described in that patent includes a step in which the interior of
the aneurysm is entered by the use of guidewire such as those in
Engelson, U.S. Pat. No. 4,884,579 and a catheter as in Engelson,
U.S. Pat. No. 4,739,768. These patents described devices utilizing
guidewires and catheters which allow access to aneurysms from
remote parts of the body. Typically, these catheters enter the
vasculature through the femoral artery in the groin. The Guglielmi
et al. system uses catheters and corewires which have a very
flexible distal regions and supporting midsections which allow the
combinations to be steerable to the region of the aneurysm. That is
to say that the guidewire is first steered for a portion of the
route to the aneurysm and the catheter is slid up over that
guidewire until it reaches a point near the distal end of the
guidewire. By steps, the catheter and guidewire are then placed at
the mouth of the aneurysm. The catheter is introduced into the
aneurysm and vaso-occlusive or embolism-forming devices may be
delivered through the lumen.
[0009] Various vaso-occlusive devices are introduced through the
noted microcatheters to close the aneurysm site. In some instances,
a small balloon may be introduced into the aneurysm where it is
inflated, detached, and left to occlude the--aneurysm. Balloons are
becoming less in favor because of the difficulty in introducing the
balloon into the aneurysm sac, the possibility of aneurysm rupture
due to over-inflation of the balloon within the aneurysm, and the
inherent risk associated with the traction produced when detaching
the balloon.
[0010] Another desirable embolism-fortning device which may be
introduced into aneurysm using end of vascular placement procedure
is found in U.S. Pat. No. 4,994,069 to Ritchart et al. In that
patent are described various devices--typically platinum/tungsten
alloy coils having very small diameters--which may be introduced
into the aneurysm through a catheter such as those described in the
Engelson patents above. These coils are often made of wire having a
diameter of 2-6 mils. The coil diameter is often 10-30 mils. These
soft, flexible coils, may be of any length desirable and
appropriate for the site to be occluded. After these vasoocclusive
coils are placed in, e.g., a berry aneurysm, they first cause a
formation of an embolic mass. This initial mass is shortly
thereafter complemented with a collagenous material which
significantly lessens the potential for aneurysm rupture.
[0011] There are variety of other vaso-occlusive devices, typically
coils which may be delivered to the vascular site in a variety of
ways, e.g., by mechanically detaching them from the delivery
device. A significant number of these devices are described in
patents owned by Target Therapeutics, Inc. For instance:
[0012] U.S. Pat. No. 5,234,437 to Sepetka shows a method of
unscrewing a helically wound coil from a pusher having interlocking
surfaces.
[0013] U.S. Pat. No. 5,250,071 to Palermo shows an embolic coil
assembly using interlocking clasps both on the pusher and on the
embolic coil.
[0014] U.S. Pat. No. 5,261,916 to Engelson shows a combination
pusher/vasoocclusive coil assembly joined by an interlocking ball
and keyway type coupling.
[0015] U.S. Pat. No. 5,304,195 to Twyford et al., shows a
pusher/vaso-occlusive coil assembly having a fixed proximally
extending wire carrying a ball on its proximal end and a pusher
having a similar end which two tips are interlocked and disengaged
when expelled from the distal tip of the catheter.
[0016] U.S. Pat. No. 5,312,415, to Palermo shows a method for
discharging numerous coils from a single pusher by using a
guidewire which has a section capable of interconnecting with the
interior of a helically wound coil.
[0017] 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 throat holds onto the end of an embolic coil and
releases that coil upon pushing the axially placed pusher wire
against member found on the proximal end of the vaso-occlusive
coil.
[0018] Other mechanically detachable embolism forming devices are
known in the art.
[0019] Each of the patents listed herein is specifically
incorporated by reference.
[0020] Guglielmi et al. shows an embolism forming device and
procedure for using that device which, instead of a mechanical
joint, uses an electrolytically severable joint. Specifically,
Guglielmi et al. desirably places a finely wound platinum coil into
a vascular cavity such as an aneurysm. The coil is delivered
endovascularly using a catheter such as those described above.
After placement in the aneurysm, the coil is severed from its
insertion core wire by the application of a small electric current
to that core wire. The deliverable coils are said to be made of a
platinum material. They may be 1-50 cm or longer as is necessary.
Proximal of the embolic coil, as noted above, is a core wire which
is typically stainless steel. The core wire is used to push the
platinum embolic coil into vascular site to be occluded.
[0021] Other variations of the Guglielmi et al. technology are
found in U.S. Pat. No. 5,354,295.
[0022] None of the references described above teaches or suggest an
implant assembly having a highly resistive or insulative joint
between that implant and a cooperating electrolytically severable
delivery joint.
SUMMARY OF THE INVENTION
[0023] This invention is an implant assembly in which an implant is
placed in the human body using an electrolytically severable joint.
The implant is isolated from the electrical circuit within the body
by an insulative or high resistance member. The implant may be a
vaso-occlusive device, stent, vena cava filter, or any other
implant which may be delivered via a catheter. Desirably, the
device includes a core wire having a distal tip, which distal tip
or implant may be introduced into the selected site. The core wire
is attached to the distal tip or implant in such a way that the
implant may be electrolytically detached by application of a
current to the core wire.
[0024] The improvement involves the use of an insulative or highly
resistive member proximal of the implant. The resistive or
insulating member may be any suitable material such as inorganic
oxides, glues, polymeric inserts, polymeric coverings, etc. This
insulative or highly resistive layer or joint appears to focus the
current flow through the sacrificial electrolytic joint and thereby
improves the rate at which detachment of the implant occurs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 shows the overall layout of delivery system showing
the typical major parts for delivering an implant using the
improvement of this invention.
[0026] FIGS. 2-11 show respectively cross sections depicting
various insulating or resistive joints which electrically isolate
implants.
[0027] FIG. 12 shows a partial cross section of an electrolytic
joint and a vaso-occlusive braid all made according to this
invention.
[0028] FIGS. 13 and 14 show helically wound vaso-occlusive coils
having secondary shapes which may be deployed using the procedures
described herein.
[0029] FIG. 15 shows a stent implant using the improvements of this
invention.
[0030] FIG. 16 shows a vena cava filter which may be deployed using
the improvements of this invention.
[0031] FIGS. 17A and 17B show, in schematic form, a procedure for
deploying the inventive vaso-occlusive device of this
invention.
[0032] FIG. 18 is a graph of detachment times for a comparative
commercial GDC device.
[0033] FIGS. 19 and 20 are graphs of detachment times for
variations of the GDC device made according to the invention.
DESCRIPTION OF THE INVENTION
[0034] As noted above, the Guglielmi et al. system for deploying an
implant into the human body uses a core wire, an electrolytic
sacrificial joint, and the implant to be deployed. A power supply
is needed to provide power for electrolysis of the joint. The core
wire is typically insulated on its outer surface from near the
proximal end of the wire and along the wire to the electrolytic
sacrificial joint. The implant typically forms a portion of the
circuit through the body. This invention substantially removes the
implant itself from that circuit thereby apparently focusing the
current flow at the electrolytic joint where it is needed for
electrolysis.
[0035] FIG. 1 shows a system for introducing and deploying the
implant made according to the invention. The system (100) includes
a catheter (102) which is made up of an elongate tubular member,
typically made from a polymeric material and often reinforced with
a coil or braid to provide strength or obviate kinking
propensities. Catheter (102) is shown with a pair of radiopaque
markers (106). The radiopaque markers (106) allow visualization of
the distal end (104) of the catheter so to compare it with the
coincidence of the implant. Catheter (102) is also shown with a
proximal fitting (108) for introduction of dyes or treatment
materials. Within the lumen of catheter (102) is a core wire (110)
extending both proximally of catheter (102) and distally. On the
distal end of core wire (110) may be seen the electrolytic joint
(112) and the implant (114). In this instance, implant (114) is
shown to be a helically wound vaso-occlusive coil. Generally, all
of core wire (110) is electrically insulated from a point near the
proximal end of core wire (110) continuously to electrolytically
severable joint (112). Electrolytically severable joint (112) is
bare and is relatively more susceptible to electrolysis in an ionic
solution such as blood or most other bodily fluids than is the
implant (114).
[0036] The most proximal end of core wire (110) is also left bare
so that power supply (116) may be attached. The other pole of the
power supply (116) is typically attached to a patch (118). The
patch is placed on the skin to complete the circuit from the power
supply (116), through the core wire (110), through electrolytic
joint (112), through the ionic solution in the body, and back to a
patch (118) to the power supply (116). Other return routes may be
used as the designer sees fit.
[0037] Central to this invention is electrical isolation of implant
(114) from core wire (110) and electrolytically severable joint
(112). Without wishing to be bound by theory, it is believed that
isolation of the implant (114) prevents or lessens current flow
through the implant (114) itself and concentrates the current flow
through the electrolytic joint (112).
[0038] FIG. 2 shows a close-up of the more distal portion of one
variation of the invention. This variation includes the core wire
(110) and the attached implant (120). Typically, core wire (110)
will be conductive but covered with a insulative layer (111) both
proximal and distal of electrolytically severable joint (112). The
interior of core wire (110) is physically attached to implant
(120). In this variation of the invention, implant (120) is a
helically wound coil.
[0039] In this invention, a highly resistive or insulative layer or
member electrically isolates implant (120) from core wire (110). In
this variation of the invention, the insulating layer (111) on the
core wire (110) is simply continued to the end of the core wire
(110). An optional bushing (114) is placed on the core wire (110)
to further separate it from implant (120). Optional bushing (114)
may be of any suitable material since it operates merely as a
spacer. Insulating layer (111) may be polytetrafluoroethylene
(e.g., Teflon), polyparaxylylene (e.g., parylene),
polyethyleneterephthalate (PET), polybutyleneterephthalate (PBT),
cyanoacrylate adhesives, or other suitable insulating layer, but
preferably is polymeric and most preferably is PET.
[0040] The coil making up this variation (and other coil-based
variations) of the invention is generally of a diameter in the
range of 0.025 inches and 0.006 inches. Wire of such diameter is
wound into a primary form having a diameter of between 0.003 and
0.025 inches. For most neurovascular indications, the preferable
primary coil diameter is preferably between 0.008 and 0.018
inches.
[0041] The axial length of the primary coil will usually fall in
the range of 0.5 to 100 cm, more usually 2.0 to 40 cm. Depending
upon usage, the coil may well have 10-75 turns per centimeter,
preferably 10-40 turns per centimeter. All of the dimensions here
are provided only as guidelines and are not critical to the
invention. However, only dimensions suitable for use in occluding
sites within the human body are included in the scope of this
invention.
[0042] FIG. 3 shows a close-up of another variation of the
invention including the more distal portion of the core wire (110)
and the attached implant (120). In this variation of the invention,
implant (120) is a helically wound coil having a stretchresistant
member (134) through its center lumen. The anti-stretch member
(134) may be of any suitable material, e.g., metallic wire or
polymeric threads. Preferred are polymeric threads comprised of a
member selected from the group consisting of polyethylene,
polypropylene, polyamides, and polyethyleneterephthalate although
almost any polymeric material which is formable into a fiber is
quite suitable. The stretch-resistant member is simply designed to
prevent the coil (120) from stretching in the event that core wire
(110) must be withdrawn or repositioned to change the position of
the implant (120).
[0043] The stretch-resistant member (134) is attached to an
interior anchor coil (136) having a distal hook (138) to which the
stretch-resistant member (134) is attached. An optional bushing
(140) is present and attached to the metallic center of the core
wire (110). In this variation of the invention, either or both of
the optional bushing (140) or interior anchor coil (136) may be of
an oxide-forming material such as tantalum and the like. We have
found that when tantalum or other such refractory forming materials
are subjected to welding operations as may be found when assembling
this device, an apparently oxidic, but highly electrically
resistive layer is formed at the junction of the tantalum and its
neighbor.
[0044] FIG. 4 shows another variation (150) of the inventive
implant assembly. In this variation, bushing (152) is formed of an
oxidic or insulative-forming material and is included to form such
a resistive layer during operations to weld the metallic center
(154) to bushing (152).
[0045] FIG. 5 shows another variation (158) of the inventive
implant assembly. In this variation, the implant (120) is attached
to the core wire (110) and at the same time is electrically
insulated from the metallic center (154) of core wire (110) by the
use of a glue or thermopolymer (156) made from a suitable polymer,
e.g., a thermoplastic, preferably comprising a member selected from
the group consisting of polyethylene, polypropylene, polyamides,
and polyethyleneterephthalate.
[0046] An "oxide forming material" or "insulator-forming material"
as those terms are used herein are materials which, under the
imposition of an appropriate electrical current or other such
excitation, will form an insulating, preferably oxide, layer. One
such material is the metal tantalum and certain of its alloys.
Other insulation forming materials or oxide forming materials
include zirconium.
[0047] Although the use of solid insulation forming material is
shown in FIGS. 3 and 4, the use of an insulation forming material
in a layer is also contemplated. Such a layer may be plated,
sputtered, painted, heat shrunk, glued, or melted onto the
appropriate part.
[0048] FIG. 6 shows another variation of the invention, in this
case using a polymeric insert between core wire (110) and helical
deployment coil (120). Electrolytically severable joint (112) is
also shown. The polymeric insert (121) typically includes a
radiopaque marker coil (123) and is simply slid over the distal tip
of core wire (110) and into the lumen of helical coil (120). Once
so assembled, this assemblage is heat-treated to cause the various
portions to adhere to each other. As is the case with any of the
other variations shown herein, it may be desirable to place
circumferential ribs on the distal tip of core wire (110) to
provide a more suitable bond for the polymeric insert (121). Care
must be taken, of course, to ensure that polymeric plug (121)
contains no materials (e.g., dyes or opacifiers) which would
enhance the conductivity of the plastic. It is the task of
polymeric insert (121) to insulate core wire (110) from deployable
helical coil (120) so the electrolytic joint (112) is easily and
readily detached. It should be noted, that although the radiopaque
coil (123) is highly desirable, in this invention, it is completely
optional.
[0049] FIG. 6 shows still another variation of the invention. This
variation is a similar concept both to the polymeric plug variation
shown in FIG. 8 and to the variation shown in FIG. 3 involving a
stretch-resistant member.
[0050] In this variation, polymeric plug (125) is again slipped
over the distal portion of core wire (110) and into the proximal
portion of helical coil (120). The assembled joint is heated so to
allow whatever thermoplastic that may be in polymeric insert (125)
to flow and secure the detachable implant (120) to the core wire.
Electrolytically severable joint (112) is also shown.
[0051] The major difference between this variation and others seen
before is in the presence of coil (127) fixedly attached to
stretch-resistant member (129). Of particular interest is the fact
that coil (127) is soldered or preferably welded to detachable
helical coil (120) in the region (131). Coil (127) should be made
from a material similar to that of helical detachable coil (120) to
prevent any untoward--happenings during the severance of
electrolytic joint (112) by provision of voltage couples or the
like.
[0052] FIG. 8 shows still another variation of the invention of the
invention in which a polymeric plug is used to separate the core
wire (103) from the deployable implant (107). Incidentally, core
wire (103) is shown to have an external marker (105) at its
proximal end. Core wire (103) additionally has, adjacent detachment
region (109), a surface (111) which is cut on a bias or at an angle
to the axis of core wire (103). As is discussed in a number of
prior patents assigned to Target Therapeutics Incorporated, this
biased surface (111) enhances the physician's ability to detach the
implantable device (107) from core wire (103) once electrolysis or
electro-erosion is completed. This surface (111) is formed by use
of a plug (113) which is typically polymeric in nature. A series of
coils (115) and (117) are also shown in this variation. Coils (115)
and (117) are typically produced of radiopaque material. They are
positioned to allow easy visualization of the detachment region
(109). The depiction found in FIG. 8 further has a shrink-wrap
coating (119) on the exterior of the device proximal of the
detachment area (109).
[0053] In this instance, the proximal end of the implant (107),
distal of the detachment zone (109) is constructed of a number of
polymeric portions which allow for easy and practical assembly of
the overall device. In particular, radiopaque coil (121) is
surrounded by polymeric region (123). It is often the case that
assembling the device shown in FIG. 8, the bare distal end of core
wire (103) will first be wrapped with coil (121) and then the
so-wrapped coil (121) will then be dipped in molten polymeric
material to form the polymeric region (123). A polymeric plug,
typically thermoplastic (125) is also inserted into the proximal
end of implant (107). A polymeric coating, typically thermoplastic
and typically a shrink-wrap is then placed over the two polymeric
masses (123) and (125). Upon application of appropriate heat, outer
covering (127) serves to attach the distal end of core wire (103)
with the proximal end of implant (107). In many instances, the
polymers used variously in region (123), region (125), and covering
(127) are the same. Desirably, they are miscible with each other
upon application of appropriate heat. It is also appropriate that
they merely bind to each other in a well-defined way.
[0054] This variation of the device is quite easy to assemble and
the radiopaque coil (123) gives the physician-user a well-defined
end point for introduction of the implant (107) into the aneurysm
or other cavity.
[0055] FIG. 9 shows a variation of the invention similar to that
found in FIG. 8 except that it shows the use of a strain resistant
vaso-occlusive device. For purposes of this description all of the
core wire (103) proximal of detachment zone (109) is the same as is
shown in FIG. 8. Similarly, the distal end of coil wire (103)
includes a radiopaque coil (121) initially covered by a polymeric
covering or region (123). In this instance, the polymeric region
(131) placed within the proximal end of vasoocclusive implant (107)
includes a coil (133) having a distal loop (135) thereon. That
distal loop is, in turn, attached to a stretch-resistant member
(137) of the type discussed at length above with regard to FIG. 3.
Again, this device may be assembled using a thermoplastic or
shrink-wrap covering (139) placed exteriorly about polymeric region
(123) and the proximal end of implant (107).
[0056] FIGS. 10 and 11 show still another variation of the
insulative joint. In particular, FIG. 10 shows a implant (141)
located distally of the region (109). In this instance, the distal
end of the core wire has a radiopaque coil (143) wrapped around.
Central to this variation of the invention is the presence of an
anchoring member (145). Anchoring member (145) typically has a
small loop (147) allowing for connection of the stretch-resistant
member (149). It is desirable to include a polymeric region (151)
distally of anchoring member (145). Polymeric region (151) may be
placed in the implant (141) in such a way that it makes the
stretch-resistant member (149) adhere well to the anchor member
(145). Anchor member (145) should have a diameter which is larger
than that of the interior of the implant (141) so that should the
distal end of implant (141) be pulled strongly, the end of anchor
member (145) not be able to pass through the lumen of implant
member (141). Again, as with the variations shown in FIGS. 8 and 9,
the exterior of the joint region shown in FIG. 10 may be all
assembled using a polymeric tubing, preferably thermoplastic, which
adheres to and joins all of the noted pertinent parts together.
[0057] FIG. 10 shows a similar variation of the anchor member (153)
but is somewhat different in that the loop (155) for attaching to
the strain resisting member (149) is larger and there is no
polymeric region (151) as was shown in FIG. 11.
[0058] The variation shown in FIGS. 8 and 9 and especially those
shown in FIGS. 10 and II are particularly useful when utilizing the
insulating joint of this invention in combination with a very
flexible vaso-occlusive coil as the implant. Such a highly flexible
vaso-occlusive coil is described in U.S. Pat. Nos. 5,669,931
(Kupiecki et al.) and 5,690,666 (Bernstein et al.). The entirety of
these patents is hereby incorporated by reference.
[0059] Although the preferred variation of the invention is that
found in the figures discussed above wherein a helical coil implant
is fixably attached distally of electrolytically severable joint
(112), other implants are suitable. For instance, FIG. 12 shows
another variation of the inventive device (160) in which the
implant is a vaso-occlusive braid (162), either woven or unwoven.
The electrolytically severable joint (164) is shown proximally of
vaso-occlusive braid (162). In this variation, the core wire is
insulated with a tubular member (168) and a bushing (170). A
stabilizing coil (172) is also depicted on the distal end of core
wire (166). Bushing (170) and covering (168) serve to electrically
insulate core wire (166) from the surrounding ionic fluid. These
coverings along with the isolating joint (not shown in cross
section in this Figure) found on vaso-occlusive woven braid (162)
apparently focus the electrolysis process on the electrolytically
severable joint (164).
[0060] When the implant is a vaso-occlusive device, the shape of
the device may be any of a number of suitable overall shapes to
promote occlusion of the selected interior body space. In
particular, when the implant is a helical coil, many shapes are
known for treatment of particular abnormalities. FIGS. 13 and 14
show useful devices for treatment of arterio-venous malformations
(AVM) and aneurysms. Specifically, FIG. 13 shows a vaso-occlusive
coil (180) which has a secondary conical shape. A "secondary" shape
is meant to include any form in which a wire is first formed into a
first helical shape and that first helical shape is wound into a
second shape which is, possibly, but not necessarily, helical.
Secondary forms include generally spherical, ovoid, elongated, and
any other form into which the device will "self-form" upon
relaxation either within a body open region or simply outside the
delivery catheter. As was noted above, vaso-occlusive devices are
introduced through a catheter. Pushing the vaso-occlusive device
through the catheter uses that first linear configuration which
approximates the shape of the interior of the catheter. Secondary
shape such as shown in FIGS. 13 and 14 are formed when the
vaso-occlusive device is allowed to exit the distal end of the
catheter. The secondary shape of the vaso-occlusive device (180)
shown in FIG. 13 is, as noted just above, conical in form.
[0061] FIG. 14 shows a variation (182) of the inventive device in
which two sections of the vaso-occlusive device have different
secondary diameters.
[0062] Each of the vaso-occlusive devices described herein may also
have attached fibrous materials to increase their
thrombogenicity.
[0063] FIG. 15 shows a variation (190) of the inventive device in
which the implant is a stent (192). Core (194) is also is shown
with an electrolytically erodable joint (196).
[0064] The stent show in FIG. 15 is a variation of a self expanding
stent typically made of a super-elastic alloy material, typically a
nickel-titanium alloy (e.g., nitinol), that is well known in the
art. The device has a zig-zag pattern of a metallic wire which is
maintained in the noted and secondary form by a filament (198)
which is woven through the bends of the stent to maintain the
secondary shape. The primary shape is simply the shape shown but
with a significantly lower diameter. The form of the stent is not
important to the invention but is only illustrative of the form an
implant may take
[0065] FIG. 16 shows the expanded form of an implant (200) which
may be used as a vena cava filter. Vena cava filters are well known
in the art and are used to prevent the flow of blood clots distally
in the vasculature. These blood clots would eventually be the site
of occlusive strokes in the brain if allowed to travel distally. In
any event, implant (200) shows the vena cava filter member (202),
the electrolytically severable joint (204) and the push wire or
core wire (206).
[0066] FIGS. 17A and 17B show placement of the inventive devices,
specifically the vaso-occlusive variations of the invention, within
the human body. FIG. 17A shows the placement within a vessel (200)
with a tip of catheter (202) placed near aneurysm neck (204). The
aneurysm itself is nominated (206). Vaso-occlusive device (208) is
fed into aneurysm (206) at least until the sacrificial link or
joint (210) (hidden within catheter (202) at this step) is exposed
beyond the distal tip of catheter (202). A positive electric
current of approximately 0.01-2 milliamps at 0.1-6 volts as applied
to core wire (212). An embolic mass is then formed within aneurysm
(206). The negative pole (214) of power supply (216) is typically
placed in electrical contact with. the skin so to complete the
circuit. The vaso-occlusive device (208) is detached from core wire
(212) by electrolytic disintegration of sacrificial link (210).
[0067] After sacrificial link (210) is at least mostly dissolved by
electrolytic action, typically in less than two minutes and most
often in less than one minute, the core wire (212), catheter (202),
are removed from vessel (200) leaving aneurysm (206) occluded as
represented by occlusion (218) in FIG. 17B.
[0068] This procedure is typically practiced under fluoroscopic
control with local or general anesthesia. A transfemoral catheter
may be used to treat cerebral aneurysm and is usually introduced at
the groin. When the vaso-occlusive device (208) is isolated by a
highly resistive material as is contemplated this invention, it is
not affected by electrolysis. When the core wire (212) and the
pertinent portions of the supporting coils at the distal tip of the
core wire (when utilized) are adequately coated with insulating
coverings, only the exposed portion of the sacrificial link (210)
is affected by the electrolysis.
EXAMPLE
[0069] We compared detachment times for commercially available
Guglielmi Detachable Coils (GDC) with those for a variation of the
invention similar to that shown in FIG. 3. We constructed three
sets of ten implant assemblies. The first set (FIG. 18) were
commercial GDC assemblies as modified below. The second set (FIG.
19) had tantalum interior anchor coils ((136) in FIG. 3) and a
distal hook (138) to which the stretch-resistant member (134) was
attached. The third set (FIG. 16) were similar to those described
in regard to FIG. 6 incorporating a PET insulator between the
detachable coil and the electrolytic joint. The implants on each
were platinum coils.
[0070] In the second set, the platinum bushing (140) was included
and attached to the metallic center of the core wire (110). The
assembly of tantalum interior anchor coil, platinum bushing, and
core wire (110) was welded together.
[0071] To exaggerate and lengthen the detachment times for each
set, as would be the case when an implant is inserted into an
aneurysm already having a number of platinum coils with vestigal
remaining stainless steel stubs remaining from prior detachments
and having electrical contact with those coils, an additional
stainless steel wire of about one inch length was added to the
detachable coils. The resulting detachment times for the coils were
increased by as much as ten-fold as is sometimes seen
clinically.
[0072] Each of the comparative commercial GDC's and the inventive
variations were placed in a saline bath and subjected to a constant
amperage of 1 ma and a resulting voltage of between 1.5 and 2.0
volts. The time for electrolytic erosion of the joint was measured.
As shown in FIG. 14, the average time for detachment of the
commercial GDC coil was 454.9 seconds. As shown in FIG. 19, the
average time for detachment of the inventive variation GDC coil
using tantalum insulator coils was 125.1 seconds. As shown in FIG.
20, the average time for detachment of the inventive variation GDC
coil using a PET insulator sock was 38 seconds.
[0073] Many alterations and modifications may be made by those
having ordinary skill in this art without departing from the spirit
and scope of the invention. The illustrative embodiments have been
used only for the purposes of clarity and should not be taken as
limiting the invention as defined by the following claims.
* * * * *