U.S. patent number RE41,029 [Application Number 11/377,895] was granted by the patent office on 2009-12-01 for endovascular electrolytically detachable wire and tip for the formation of thrombus in arteries, veins, aneurysms, vascular malformations and arteriovenous fistulas.
This patent grant is currently assigned to The Regents of the University of California. Invention is credited to Guido Guglielmi, Ivan Sepetka.
United States Patent |
RE41,029 |
Guglielmi , et al. |
December 1, 2009 |
Endovascular electrolytically detachable wire and tip for the
formation of thrombus in arteries, veins, aneurysms, vascular
malformations and arteriovenous fistulas
Abstract
An artery, vein, aneurysms vascular malformation or arterial
fistula is occluded through endovascular occlusion by the
endovascular insertion of a platinum wire and/or tip into the
vascular cavity. The vascular cavity is packed with the tip to
obstruct blood flow or access of blood in the cavity such that the
blood clots in the cavity and an occlusion if formed. The tip may
be elongate and flexible so that it packs the cavity by being
folded upon itself a multiple number of times, or may pack the
cavity by virtue of a filamentary or fuzzy structure of the tip.
The tip is then separated from the wire mechanically or by
electrolytic separation of the tip from the wire. The wire and the
microcatheter are thereafter removed leaving the tip embedded in
the thrombus formed within the vascular cavity. Movement of wire in
the microcatheter is more easily tracked by providing a radioopaque
proximal marker on the microcatheter and a corresponding indicator
marker on the wire. Electrothrombosis is facilitate by placing the
ground electrode on the distal end of the microcatheter and flowing
current between the microcatheter electrode and the tip.
REEAXMINATION RESULTS The questions raised in reexamination request
90/007,231, filed Oct. 4, 2004 have been considered and the results
thereof are reflected in this reissue patent which constitutes the
reexamination certificate required by 35 U.S.C. 307 as provided in
37 CFR 1.570(e), for ex parte reexaminations, or the reexamination
certificate required by 35 U.S.C. 316 as provided in 37 CFR 1.99(e)
for inter partes reexaminations.
Inventors: |
Guglielmi; Guido (Rome,
IT), Sepetka; Ivan (Los Altos, CA) |
Assignee: |
The Regents of the University of
California (Oakland, CA)
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Family
ID: |
27502012 |
Appl.
No.: |
11/377,895 |
Filed: |
March 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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08801795 |
Feb 14, 1997 |
5855578 |
|
|
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08485821 |
Jun 6, 1995 |
|
|
|
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08311508 |
Sep 23, 1994 |
5540680 |
|
|
|
07840211 |
Feb 24, 1992 |
5354295 |
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07492717 |
Mar 13, 1990 |
5122136 |
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Reissue of: |
08944827 |
Nov 6, 1997 |
05895385 |
Apr 20, 1999 |
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Current U.S.
Class: |
606/32; 606/108;
606/191; 606/41 |
Current CPC
Class: |
A61B
17/12022 (20130101); A61B 17/1214 (20130101); A61B
17/12145 (20130101); A61B 17/1215 (20130101); A61B
17/12172 (20130101); A61B 18/1492 (20130101); A61M
25/09 (20130101); A61B 17/12113 (20130101); A61B
2090/3966 (20160201); A61B 18/1402 (20130101); A61B
2017/00292 (20130101); A61B 2017/12063 (20130101); A61B
2017/22038 (20130101); A61B 2018/00678 (20130101); A61B
2018/00761 (20130101); A61B 2018/00875 (20130101); A61B
2018/00886 (20130101); A61B 2018/1226 (20130101); A61B
2018/1253 (20130101); A61B 2018/126 (20130101); A61B
2018/1266 (20130101); A61B 2018/1435 (20130101); A61B
2018/1495 (20130101); A61M 2025/09175 (20130101); A61B
2017/12054 (20130101); A61B 2017/12095 (20130101); A61B
90/39 (20160201) |
Current International
Class: |
A61B
18/04 (20060101); A61B 17/00 (20060101); A61B
17/12 (20060101); A61B 18/12 (20060101); A61B
18/14 (20060101) |
References Cited
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WO |
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WO |
|
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|
Primary Examiner: Peffley; Michael
Attorney, Agent or Firm: Fenwick & West LLP
Parent Case Text
This application is a continuation of application Ser. No.
08/801,795 filed Feb. 14, 1997, issued as U.S. Pat. No. 5,885,578,
which in turn .[.was.]. .Iadd.is .Iaddend.a continuation of
application Ser. No. 08/485,821, field Jun. 6, 1995, now
abandoned.Iadd., which is a divisional of application Ser. No.
08/311,508, filed on Sep. 23, 1994, issued as U.S. Pat. No.
5,540,680, which is a continuation application of application Ser.
No. 07/840,211 filed on Feb. 24, 1992, issued as U.S. Pat. No.
5,354,295.Iaddend., and which in its turn .[.was.]. .Iadd.is
.Iaddend.a continuation-in-part application of application Ser. No.
07/492,717, filed Mar. 13, 1990, issued as U.S. Pat. No. 5,122,136.
Claims
We claim:
1. An apparatus adapted to form an occlusion within a body cavity
having fluid disposed therein comprising: a wire; and a separable
distal tip section adapted to be disposed into said body cavity to
substantially space occupy said body cavity to mechanically form
said occlusion within said body cavity about and separable distal
tip section wherein mechanically forming an occlusion is defined as
forming an occlusion so that fluid flow is substantially inhibited,
said separable distal tip being adapted to be nonthermally
separated from said wire to leave said separable distal tip section
within said body cavity, wherein nonthermal separation is defined
as a detachment without substantially increasing the temperature of
said distal tip section, wherein said separable distal tip section
is separated from said wire without necessarily displacing said
distal tip section therefrom, wherein said separable distal tip
section has no memory of its predisposed shape other than at most a
relaxed simple helical shape. whereby said body cavity is occluded
by said distal tip section, and any thrombus formed by used of said
distal tip section.
2. The apparatus of claim 1 wherein said separable distal tip
section is mechanically detachable from said wire.
3. The apparatus of claim 1 further comprising a catheter and where
said wire and distal tip section are longitudinally displaced
within said catheter, said catheter having a radioopaque proximal
marker, said wire and distal tip section having collectively a
single radioopaque marker, said displacement of said wire and
distal tip section moving said single radioopaque marker to the
proximity of said proximal marker on said catheter when said distal
tip section is fully deployed in said cavity.
4. The apparatus of claim 1 where said distal tip section comprises
a long flexible distal tip section having a plurality of filaments
extending therefrom to pack said body cavity.
5. The apparatus of claim 1 where said distal tip section is
sufficiently long and flexible to fold upon itself a multiple
number of times to occupy said body cavity to substantially impede
fluid flow therein.
6. An apparatus for forming an occlusion in a body cavity
comprising: a microcatheter having a distal electrode; a wire
having a distal tip; a distal tip electrode on said wire, said
distal tip of said wire for substantially space filling said cavity
to form said occlusion about said distal tip by application of a
current between said distal tip electrode on said wire and said
distal electrode on said microcatheter; and a nonthermal detachment
coupling between said distal tip of said wire and a remaining
portion of said wire, wherein nonthermal detachment is defined as a
detachment without substantially increasing the temperature of said
detachment coupling. whereby said cavity is occluded by said distal
tip and a thrombus formed thereby.
7. An apparatus for use in occluding a body cavity comprising: a
wire; and a detachable elongate distal tip coupled to said wire,
said elongate distal tip being a relaxed coil capable of being
multiply folded upon itself.
8. The improvement of claim 7 wherein said elongate distal tip is a
long and substantially pliable segment adapted to be multiply
folded upon itself to sufficiently occupy said body cavity to
impede the fluid flow therein.
9. The improvement of claim 7 wherein said elongate tip is a
segment adapted to be disposed in said body cavity and has a
plurality of filaments extending therefrom to sufficiently occupy
said body cavity to impede fluid flow therein.
10. The improvement of claim 7 further comprising a catheter having
a pair of radioopaque markers disposed thereon and having a distal
end, said wire having a radioopaque marker disposed thereon, said
marker on said wire being positioned in the proximity of one of
said pair of markers on said catheter when said wire is fully
deployed in said body cavity, said other marker of said pair of
markers on said catheter indicating said distal end of said
catheter.
11. The improvement of claim 7 wherein said distal tip is coupled
to said wire by a polymeric bead.
12. The improvement of claim 11 wherein said bead is polyester.
13. The apparatus of claim 7 wherein said detectable elongate tip
is a coil having a length between 1 and 50 cm.
14. An apparatus for forming an occlusion within a body cavity
having fluid disposed therein comprising: a catheter having a
distal end for disposition in proximity to said cavity and having
an electrode disposed therein; a conductive wire disposed in said
catheter and longitudinally displaceable therein, said wire
comprising: a core wire having a distal portion; and an elongate
tip portion extending from said core wire for a predetermined
lineal extent and adapted to being packed into said cavity and
coupled to said distal portion of said core wire, said occlusion
being formed by means of application of a current between said
elongate tip portion and said electrode on said catheter when said
elongate tip portion is disposed in said cavity, said elongate tip
portion being a relaxed coil having no substantial memory of its
predisposed shape other than at most a relaxed simple helical
shape, wherein occlusion of said cavity is performed.
15. In an apparatus having a wire for forming an occlusion in a
body cavity having a fluid flowing therein, the improvement
comprising: a deformable object temporarily coupled to said wire
for disposition into said cavity having no preferred geometric form
when disposed into said cavity, said deformable object capable of
being multiply folded upon itself, said deformable object
substantially impeding movement of said fluid in said cavity to
thereby form said occlusion, whereby said cavity is occluded by
said object.
16. The improvement of claim 15 where said deformable object is
adapted to being packed into said body cavity to substantially
obstruct said cavity.
17. The improvement of claim 16 where said object comprises a
detachable, elongate, coil wire tip which is capable of being
multiply folded upon itself in said body cavity.
18. The improvement of claim 16 wherein said deformable object has
a multiplicity of flexible filaments extending therefrom.
19. The improvement of claim 15 wherein said deformable object
comprises a means for slowing fluid movement in said cavity to
initiate formation of said occlusion in said cavity.
20. The improvement of claim 15 further comprising a source of
electrical current coupling to said deformable object and wherein
said occlusion is formed by application of current to said
deformable object.
21. The improvement of claim 20 further comprising a catheter and a
proximal electrode on said catheter used to dispose said deformable
object into said cavity, said current being applied by said means
between said deformable object and said proximal electrode.
22. The improvement of claim 15 where said deformable object is
adapted to mechanically form said occlusion within said cavity.
23. The improvement of claim 15 further comprising a source of
electrical current coupling to said deformable object, wherein said
occlusion is simultaneously formed by application of current to
said deformable object and wherein said occlusion is mechanically
formed by said deformable object within said cavity.
24. An apparatus adapted to form an occlusion within a body cavity
used in combination with a catheter comprising: a wire; a
detachable elongate distal tip portion coupled to and extending
from said wire for a predetermined lineal extent, said detachable
elongate distal tip portion being adapted to being packed into said
body cavity to form said occlusion in said body cavity, said
elongate distal tip portion including a first flexible, shapeless
segment having substantially no memory of its predisposition shape
other than at most a relaxed, simple helical shape for disposing
into said cavity and a second segment for coupling said first
segment to said wire, said second segment being adapted to be
electrolyzed upon application of current; and an insulating coating
disposed on said first segment, said second segment being left
exposed to permit selective electrolysis thereof, whereby occlusion
of said body cavity is achieved.
25. An apparatus adapted to form an occlusion within a body cavity
having fluid disposed therein comprising: a wire adapted for
disposition near an opening into said body cavity; a distal tip
coupled to said wire adapted to substantially occupy said body
cavity to form said occlusion within said body cavity about said
distal tip, said distal tip being characterized by being adapted to
carry electrical current therethrough to form an electrothrombosis
in said body cavity, and being mechanically detachable from said
wire to leave said distal tip within said body cavity, whereby said
body cavity is occluded by said distal tip, and any thrombus formed
by use of said distal tip.
26. A method for forming an occlusion within a body cavity having
fluid disposed therein comprising the steps of: disposing a relaxed
wire into said body cavity, said relaxed wire having no substantial
memory of its predisposed shape other than at most a relaxed,
simple helical shape; disposing a separable distal tip of said
relaxed wire to substantially space occupy said body cavity to
mechanically form said occlusion within said body cavity about said
separable distal tip; and nonthermally detaching said separable
distal tip from said wire without necessarily displacing said
distal tip from said wire in order to detach said distal tip from
said wire, wherein nonthermal detachment is defined as a detachment
without substantially increasing the temperature of a coupling
between said distal tip and wire, whereby said body cavity is
occluded by said distal tip, and a thrombus formed by use of said
tip.
27. The method of claim 26 wherein said step of detaching a
separate distal tip of said relaxed wire mechanically detaches said
distal tip from said wire.
28. The method of claim 26 where said wire and tip are used with a
catheter, and were in said step of nonthermally detaching said
distal tip from said wire, said wire and tip are longitudinally
displaced within said catheter, said catheter having a radioopaque
proximal marker, said wire and tip having collectively a single
radioopaque marker, said displacement of said wire and tip moving
said single radioopaque marker to the proximity of said proximal
marker on said catheter when said tip is fully deployed in said
cavity.
29. The method of claim 26 where said step of disposing said top
comprises disposing a long flexible tip having a plurality of
filaments extending therefrom to pack said body cavity.
30. The method of claim 26 where said step of disposing a relaxed
wire into said body cavity disposes a long and flexible coil which
folds upon itself a multiple number of times to occupy said body
cavity to substantially impede fluid flow therein.
31. A method for forming an occlusion in a body cavity comprising:
disposing a microcatheter having a distal electrode near an opening
into said body cavity; disposing a wire having a distal tip
electrode into said body cavity to substantially fill said cavity
to form said occlusion about said distal tip electrode by
application of a current between said distal tip electrode on said
wire and said distal electrode on said microcatheter; and
nonthermally detaching a distal tip of said wire from a remaining
portion of said wire, wherein said distal tip is coupled to said
remaining portion by a detachment coupling and wherein nonthermal
detachment is defined as a detachment without substantially
increasing the temperature of said detachment coupling, whereby
said cavity is occluded by said distal tip and a thrombus formed
thereby.
32. A method of forming an occlusion within a body cavity used in
combination with a wire comprising the step of: packing at least
one detachable elongate distal tip portion coupled to and extending
from said wire for a predetermined lineal extent into said body
cavity to form said occlusion in said body cavity, said elongate
distal tip portion being a relaxed coil capable of being multiply
folded upon itself; and detaching said elongate distal tip portion
from said wire, whereby occlusion of said body cavity is
achieved.
33. The wire of claim 32 where said step of packing at least one
detachable elongate distal tip into said body cavity packs a long
and substantially pliable segment adapted to be multiply folded
upon itself to sufficiently occupy said body cavity to impede fluid
flow therein.
34. The method of claim 32 wherein said step of packing said
elongate tip portion packs a segment in said body cavity having a
plurality of filaments extending therefrom to sufficiently occupy
said body cavity to impede fluid flow therein.
35. The method of claim 32 further comprising the step of disposing
said wire into a catheter having a pair of radioopaque markers
disposed thereon and having a distal end, said wire having a
radioopaque marker disposed thereon, said marker on said wire being
positioned in the proximity of one of said pair of markers on said
catheter when said wire is fully deployed in said body cavity and
said other marker of said pair of markers on said catheter
indicating said distal end of said catheter during said step of
packing.
36. The wire of claim 32 where in said step of packing said distal
tip portion is coupled to said wire by a polyester bead.
37. A method for forming an occlusion within a body cavity having
fluid disposed therein comprising the steps of: disposing a
catheter having an electrode disposed thereon and having a distal
end in proximity to said cavity; disposing a conductive wire in
said catheter and longitudinally displaceable therein, said wire
comprising a core wire having a distal portion; and an elongate tip
portion extending from said core wire for a predetermined lineal
extent and coupled to said distal portion of said core wire;
packing said elongate tip portion into said cavity; forming said
occlusion by means of application of a current between said
elongate tip portion and said electrode on said catheter when said
elongate tip portion is disposed in said cavity, said elongate tip
portion being a relaxed coil having no substantial memory of its
predisposed shape other than at most a relaxed simple helical
shape, whereby occlusion of said cavity is performed.
38. In a method for forming an occlusion in a body cavity having a
fluid flowing therein by disposing a wire at least adjacent to said
body cavity, the improvement comprising: disposing a deformable
object into said cavity having no preferred geometric form when
disposed into said cavity, said deformable object capable of being
multiply folded upon itself, said deformable object substantially
impeding movement of said fluid in said cavity to thereby form said
occlusion, whereby said cavity is occluded by said object.
39. The method of claim 38 where said step of disposing said
deformable object packs said deformable object into said body
cavity to substantially obstruct said cavity.
40. The improvement of claim 39 where said step of disposing said
deformable object packs said object into said cavity by disposition
of a detachable, elongate, coil wire tip which is multiply folded
upon itself in said body cavity.
41. The improvement of claim 39 where said step of disposing said
deformable object packs said deformable object having a
multiplicity of flexible filaments extending therefrom into said
cavity.
42. The improvement of claim 38 where said step of disposing said
deformable object comprises the step of slowing fluid movement in
said cavity to initiate formation of said occlusion in said
cavity.
43. The improvement of claim 38 in combination with a catheter
having a proximal electrode and used to dispose said deformable
object into said cavity, and further comprising the step of
applying electrical current to said deformable object and wherein
said occlusion is formed by application of current between said
deformable object and said proximal electrode.
44. The improvement of claim 38 where disposing a deformable object
into said cavity mechanically forms said occlusion within said
cavity.
45. The improvement of claim 38 further comprising a source of
electrical current coupling to said deformable object, where
disposing a deformable object into said cavity mechanically forms
said occlusion within said cavity and where said occlusion is
simultaneously formed by application of current to said deformable
object from said electrical source.
46. A method for forming an occlusion within a body cavity in
combination with a catheter comprising: packing a detachable
elongate distal tip portion coupled to and extending from a wire
into said body cavity to form said occlusion in said body cavity,
said elongate distal tip portion including a first flexible,
shapeless segment having substantially no memory of its
predisposition shape other than at most a relaxed, simple helical
shape for disposition into said cavity and a second segment for
coupling said first segment to said wire; and electrolytically
disconnecting said second segment from said wire upon application
of current to said second segment, an insulating coating disposed
on said first segment, said second segment being left exposed to
permit selective electrolysis thereof, whereby occlusion of said
body cavity is achieved.
47. A method for forming an occlusion within a body cavity having
fluid disposed therein comprising: disposing a wire near an opening
into said body cavity; disposing a distal tip coupled to said wire
into said body cavity to substantially occupy said body cavity to
form said occlusion within said body cavity about said distal tip;
forming an electrothrombosis in said body cavity about said distal
tip being by applying electrical current said distal tip; and
mechanically detaching said distal tip from said wire to leave said
distal tip within said body cavity, whereby said body cavity is
occluded by said distal tip, and any thrombus formed by use of said
distal tip.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and apparatus for endovascular
electrothrombic formation of thrombi in arteries, veins, aneurysms,
vascular malformations and arteriovenous fistulas.
2. Description of the Prior Art
Approximately 25,000 intracranial aneurysms rupture every year in
North America. The primary purpose of treatment for ruptured
intracranial aneurysm is to prevent rebleeding. At the present
time, three general methods of treatment exist, namely an
extravascular, endovascular and extra-endovascular approach.
The extravascular approach is comprised of surgery or microsurgery
of the aneurysm or treatment site for the purpose of preserving the
parent artery. This treatment is common with intracranial berry
aneurysms. The methodology comprises the step of clipping the neck
of the aneurysm, performing a sutureligation of the neck, or
wrapping the entire aneurysm. Each of these surgical procedures is
performed by intrusive invasion into the body and performed from
outside the aneurysm or target site. General anesthesia,
craniotomy, brain retraction and arachnoid dissection around the
neck of the aneurysm and placement of a clip are typically required
in these surgical procedures. Surgical treatment of vascular
intracranial aneurysm can expect a mortality rate of 4-8% with a
morbidity rate of 18-20%. Because of the mortality and morbidity
rate expected, the surgical procedure is often delayed while
waiting for the best surgical time with the result that an
additional percentage of patients will die from the underlying
disease or defect prior to surgery. For this reason the prior art
has sought alternative means of treatment.
In the endovascular approach, the interior of the aneurysm is
entered through the use of a microcatheter. Recently developed
microcatheters, such as those shown by Engelson. "Catheter
Guidewire", U.S. Pat. No. 4,884,579 and as described in Engelson,
"Catheter for Guidewire Trackzng", U.S. Pat. No. 4,739,768 (1998),
allow navigation into the cerebral arteries and entry into cranial
aneurysm.
In such procedures a balloon is typically attached to the end of
the microcatheter and it is possible to introduce the balloon into
the aneurysm, inflate it, and detach it, leaving it to occlude the
sac and neck with preservation of the parent artery. While
endovascular balloon embolization of berry aneurysms is an
attractive method in situations where an extravascular surgical
approach is difficult, inflation of a balloon into the aneurysm
carries some risk of aneurysm rupture due to possible
over-distention of portions of the sac and due to the traction
produced while detaching the balloon.
While remedial procedures exist for treating a ruptured aneurysm
during classical extravascular surgery, no satisfactory methodology
exists if the aneurysm breaks during an endovascular balloon
embolization.
Furthermore, an ideal embolizing agent should adapt itself to the
irregular shape of the internal walls of the aneurysm. On the
contrary, in a balloon embolization the aneurysmal wall must
conform to the shape of the balloon. This may not lead to a
satisfactory result and further increase the risk of rupture.
Still further, balloon embolization is not always possible. If the
diameter of the deflated balloon is too great to enter the
intracerebral arteries, especially in the cases where there is a
vasospasm, complications with ruptured intracranial aneurysms may
occur. The procedure then must be deferred until the spasm is
resolved and this then incurs a risk of rebleeding.
In the extra-intravascular approach, an aneurysm is surgically
exposed or stereotaxically reached with a probe. The wall of the
aneurysm is then performed from the outside and various techniques
are used to occlude the interior in order to prevent it from
rebleeding. These prior art techniques include elecrothrombosis,
isobutyl-cyanoacrylate embolization, hog-hair embolization and
ferromagnetic thrombosis.
In the use of electrothrombosis for extra-intravascular treatment
the tip of a positively charged electrode is inserted surgically
into the interior of the aneurysm An application of the positive
charge attracts white blood cells, red blood cells, platelets and
fibrinogen which are typically negatively charged at the normal pH
of the blood. The thrombic mass is then formed in the aneurysm
about the tip. Thereafter, the tip is removed, See Mullan,
"Experiences with Surgical Thrombosis of Intracranial Berry
Aneurysms and Carotid Cavemous Fistulas": J. Neurosurg., Vol. 41,
December 1974; Hosobuchi, "Electrothrombosis Carotid-Cavemous
Fistula",J. Neurosurg., Vol. 42, January 1975; Afaki et al.,
"Electrically Induced Thrombosis for the Treatment of Intracranial
Anewysms and Angiomas", Excerpta Medica International Congress
Series, Amsterdam 1965, Vol. 110, 651-654; Sawyer et al.,
"Bio-Electric Phenomena as an Etiological Factor in Intravascular
Thrombosis", Am. J. Physiol., Vol. 175, 103-107 (1953); J. Piton et
al., "Selective Vascular Thrombosis Induced by a Direct Electrical
Current; Animal Experiments", J. Neuroradiology. Vol. 5, pages
139-152 (1978). However, each of these techniques involves some
type of intrusive procedure to approach the aneurysm from the
exterior of the body.
The prior art has also devised the use of a liquid adhesive
isobutylcyanoacrylate (IBCA) which polymerizes rapidly on contact
with blood to form it firm mass. The liquid adhesive is injected
into the aneurysm by puncturing the sac with a small needle. In
order to avoid spillage into the parent artery during IBCA
injection, blood flow through the parent artery must be momentarily
reduced of interrupted. Alternatively, an inflated balloon may be
placed in the artery at the level of the neck of the aneurysm for
injection. In addition to the risks caused by temporary blockage of
the parent artery, the risks of seepage of such a polymerizing
adhesive into the parent artery exists, if it is not completely
blocked with consequent occlusion of the artery.
Still further, the prior art has utilized an air gun to inject hog
hair through the aneurysm wall to induce internal thrombosis. The
success of this procedure involves exposing the aneurysm
sufficiently to allow air gun injection and has not been
convincingly shown as successful for throbic formations.
Ferromagnetic thrombosis in the prior art in extraintravascular
treatments comprises the stereotactic placement of a magnetic probe
against the sac of the aneurysm followed by injection into the
anuerysm by an injecting needle of iron microspheres. Aggregation
of the microspheres through the extravascular magnet is followed by
interneuysmatic throbus. This treatment has not been entirely
successful because of the risk of fragmentation of the metallic
thrombus when the extravascular magnet is removed. Suspension of
the iron powder in methyl methymethacrylate has been used to
prevent fragmentation. The treatment has not been favored, because
of the need to puncture the aneurysm, the risk of occlusion of the
parent artery, the use of unusual and expensive equipment, the need
for a craniectomy and general anesthesia, and the necessity to
penetrate cerebral tissue to reach the aneurysm.
Endovascular coagulation of blood is also well known in the art and
a device using laser optically generated heat is shown by O'Reilly,
"Optical Fiber with Attachable Metallic Tip for Intravascular Laser
Coagulation of Arteries, Veins, Aneurysms, Vascular Malformation
and Arteriovenous Fistulas", U.S. Pat. No. 4,735,201 (1988). See
also, O'Reilly et al., "Laser Induced Thermal Occlusion of Berry
Aneurysms: Initial experimental Results", Radiology, Vol. 171, No.
2, pages 471-74 (1989). O'Reilly places a tip into an aneurysm by
means of an endovascular microcatheter. The tip is adhesively
bonded to a optic fiber disposed through the microcatheter. Optical
energy is transmitted along the optic fiber from a remote laser at
the proximal end of the microcatheter. The optical energy heats the
tip of cauterize the tissue surrounding the neck of the aneurysm or
other vascular opening to be occluded. The catheter is provided
with a balloon located on or adjacent to its distal end to cut off
blood flow to the site to be cauterized and occluded. Normally, the
blood flow would carry away the heat at the catheter tip, thereby
preventing cauterization. The heat in the tip also, serves to melt
the adhesive used to secure the tip to the distal end of the
optical fiber, If all goes well, the tip can be separated from the
optical fiber and left in place in the neck of the aneurysm,
provided that the cauterization is complete at the same time as the
hot melt adhesive melts.
A thrombus is not formed from the heated tip. Instead, blood tissue
surrounding the tip is coagulated. Coagulation is a denaturation of
protein to form a connective-like tissue similar to that which
occurs when the albumen of an egg is heated and coagulates from a
clear running liquid to as opaque white solid. The tissue
characteristics and composition of the coagulated tissue is
therefore substantially distinct from the thrombosis which is
formed by the thrombotic aggregation of white and red blood cells,
platelets and fibrinogen. The coagulative tissue is substantially
softer than a thrombic mass and can therefore more easily be
dislodged.
O'Reilly's device depends at least in part upon the successful
cauterization timed to occur no later than the detachment of the
heat tip from the optic fiber. The heated tip must also be
proportionally sized to the neck of the aneurysm in order to
effectively coagulate the tissue surrounding it to form a blockage
at the neck. It is believed that the tissue in the interior of the
aneurysm remains substantially uncoagulated. In addition, the hot
melt adhesive attaching the tip to the optic fiber melts and is
dispersed into the adjacent blood tissue where it resolidifies to
form free particles within the intracranial blood stream with much
the same disadvantages which result from fragmentation of a
ferromagnetic electrothrombosis.
Therefore, what is needed is an apparatus and methodology which
avoids each of the shortcomings and limitations of the prior art
discussed above.
BRIEF SUMMARY OF THE INVENTION
The invention is a method for forming an occlusion within a
vascular cavity having blood disposed therein comprising the steps
of endovascularly disposing a wire and/or tip near an endovascular
opening into the vascular cavity. The wire may include a
distinguishable structure at its distal end, which is termed a tip,
in which case the remaining portion of the wire may be termed a
guidewire. The term "wire" should be understood to collectively
include both guidewires and tips and simply wires without distinct
tip structures. However, the tip may also simply be the extension
of the wire itself without substantial distinction in its nature. A
distal tip of the wire is deposited into the vascular cavity to
pack the cavity to mechanically form the occlusion within the
vascular cavity about the distal tip. The distal tip is detached
from the guidewire (or wire) to leave the distal tip within the
vascular cavity. As a result, the vascular cavity is occluded by
the distal tip, and by any thrombus formed by use of the tip.
In one embodiment, the step of detaching the distal tip from the
guidewire (or wire) comprises the step of mechanically detaching
the distal tip from the guidewire (or wire).
In another embodiment, the guidewire and tip (or wire) are used
within a microcatheter and in the step of detaching the distal tip
from the guidewire (or wire), the guidewire and tip (or wire) are
longitudinally displaced within the microcatheter. The
microcatheter has radio-opaque proximal and tip markers. The
guidewire and tip (or wire) have collectively a single radio-opaque
marker. The displacement of the guidewire and tip (or wire) moves
the single radio-opaque marker to the proximity of the proximal
marker on the microcatheter. At this point the tip will be fully
deployed in the vascular cavity and tip separation may proceed. It
is not necessary then in this embodiment to be able to see actual
deployment of the tip before operation. The tip member allows and
enhances direct observation of the correct placement of the
catheter tip into the opening of the vascular cavity.
In one embodiment the step of disposing the tip (or wire) into the
vascular cavity to pack the cavity comprises the step of disposing
a tip (or wire) having a plurality of filaments extending therefrom
to pack the cavity.
In another embodiment the step of disposing the tip (or wire) into
the vascular cavity to pack the cavity comprises the step of
disposing a long flexible tip (or wire) folded upon itself a
multiple number of times to pack the cavity.
The invention can also be characterized as a method for forming an
occlusion within a vascular cavity having blood disposed therein
comprising the steps of endovascularly disposing a wire within a
microcatheter near an endovascular opening into the vascular
cavity. The microcatheter has a distal tip electrode. The distal
tip of the wire is disposed into the vascular cavity to pack the
cavity to form the occlusion within the vascular cavity about the
distal tip of the wire by applying a current between the distal tip
electrode and the distal end of the wire packed into the cavity.
The distal tip of the wire is detached from the wire to leave the
distal tip of the wire within the vascular cavity. As a result, the
vascular cavity is occluded by the distal tip, and by any thrombus
formed by use of the tip.
The invention is also a wire for use in formation of an occlusion
within a vascular cavity used in combination with a microcather
comprising a core wire, and a detachable elongate tip portion
extending the core wire for a predetermined lineal extent. The tip
portion is adapted to be packed into the vascular cavity to form
the occlusion in the vascular cavity and coupled to the distal
portion of the core wire. As a result, endovascular occlusion of
the vascular cavity can be performed.
In one embodiment, the elongate tip portion is a long and
substantially pliable segment adapted to be multiply folded upon
itself to substantially pack said vascular cavity.
In another embodiment, the elongate tip portion is a segment
adapted to be disposed in said vascular cavity and having a
plurality of filaments extending therefrom to substantially pack
said vascular cavity when disposed therein.
In still another embodiment, the microcather has a pair of
radioopaque markers disposed thereon and the core wire has a
radioopaque maker disposed thereon. The marker on the core wire is
positioned in the proximity of one of the pair of markers on the
microcatheter when the core wire is fully deployed. The other
marker on the core wire marks the position of the catheter tip.
The invention is still further characterized as a microcatheter
system for use in formation of an occlusion within a vascular
cavity comprising a microcatheter having a distal end adapted for
disposition in the proximity of the vascular cavity. The distal end
has an electrode disposed thereon. A conductive guidewire is
disposed in the microcatheter and longitudinally displaceable
therein. The guidewire comprises a core wire, and an elongate tip
portion extending the core wire for a predetermined lineal extent.
The tip portion is adapted to be packed into the vascular cavity to
form the occlusion in the vascular cavity. The tip portion is
coupled to the distal portion of the core wire. The occlusion is
formed by means of applying a current between the tip portion and
the electrode on the microcatheter when the tip portion is disposed
into the vascular cavity. As a result, endovascular occlusion of
the vascular cavity can be performed.
More generally speaking, the invention is a method for forming an
occlusion within a vascular cavity having blood disposed therein
comprising the steps of disposing a body into the cavity to
substantially impede movement of blood in the cavity. The body is
employed in the cavity to form the occlusion within the vascular
cavity. As a result, the vascular cavity is occluded by the
body.
The step of disposing the body in the vascular cavity comprises the
step of packing the body to substantially obstruct the cavity.
In one embodiment the step of packing the cavity with the body
comprises the step of obstructing the cavity with a detachable
elongate wire tip multiply folded upon itself in the cavity.
The step of disposing the body into the vascular cavity comprises
disposing in the vascular cavity means for slowing blood movement
in the cavity to initiate formation of the occlusion in the
cavity.
In another embodiment the step of packing the cavity with the body
comprises the step of obstructing the cavity with a body having a
compound filamentary shape.
The step of employing the blood in the vascular cavity to form the
occlusion comprises the step of applying an electrical current to
the body or mechanically forming the occlusion in the body or
simultaneously.
The invention is also wire for use in formation of an occlusion
within a vascular cavity used in combination with a microcatheter.
The invention comprises a core wire and a detachable elongate tip
portion extending the core wire for a predetermined lineal extent.
The core wire is adapted to being packed into the vascular cavity
to form the occlusion in the vascular cavity and is coupled to the
distal portion of the core wire. The tip portion includes a first
segment for disposition into the cavity and a second segment for
coupling the first portion to the core wire. The second segment is
adapted to be electrolysized upon application of current. An
insulating coating is disposed on the first segment. The second
segment is left exposed to permit selective electrolysis thereof.
As a result, endovascular occlusion of the vascular cavity can be
performed.
The invention can better be visualized by now turning to the
following drawings wherein like elements are referenced by like
numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged partially cross-sectioned side view of a
first embodiment of the distal end of the guidewire and tip of the
invention
FIG. 2 is an enlarged longitudinal cross section of a second
embodiment of the guidewire and tip of the invention.
FIG. 3 is an enlarged side view of a third embodiment of the
invention with a microcatheter portion cut away in a longitudinal
cross-sectional view.
FIG. 4 is a simplified depiction of the wire of FIG. 3 shown
disposed within a simple cranial aneurysm.
FIG. 5 is a depiction of the wire of FIG. 4 shown after
electrolytic detachment of the tip.
FIG. 6 is plan view of another embodiment of the guidewire and tip
portion wherein the type is provided with a plurality of polyester
filamentary hairs.
FIGS. 7 and 8 are a diagrammatic depictions of the use of the
invention wherein position markers have been provided on the
catheter and wire to assist in proper fluoroscopic
manipulation.
FIG. 9 is a simplified cross-sectional view of the catheter and
wire showing a ground electrode disposed on the distal tip of the
catheter.
The invention and its various embodiments are best understood by
now turning to the following detailed description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An artery, vein, aneurysm, vascular malformation or arterial
fistula is occluded through endovascular occlusion by the
endovascular insertion of a platinum tip into the vascular cavity.
The vascular cavity is packed with the tip to obstruct blood flow
or access of blood in the cavity such that the blood clots in the
cavity and an occlusion if formed. The tip may be elongate and
flexible so that it packs the cavity by being folded upon itself a
multiple number of times, or may pack the cavity by virtue of a
filamentary or fuzzy structure of the tip. The tip is then
separated from the wire mechanically or by electrolytic separation
of the tip from the wire. The wire and the microcatheter are
thereafter removed leaving the tip embedded in the thrombus formed
within the vascular cavity. Movement of wire in the microcatheter
is more easily tracked by providing a radioopaque proximal marker
on the microcatheter and a corresponding indicator marker on the
wire. Electrothrombosis is facilitate by placing the ground
electrode on the distal end of the microcatheter and flowing
current between the microcatheter electrode and the tip.
When the tip is separated from the wire by electrolytic separation
of the tip from the wire, a portion of the wire connected between
the tip and the body of the wire is comprised of stainless steel
and exposed to the bloodstream so that upon continued application
of a positive current to the exposed portion, the exposed portion
is corroded away at least at one location and the tip is separated
from the body of the wire.
FIG. 1 is an enlarged side view of a first embodiment of the distal
end of the wire and tip shown in partial cross-sectional view. A
conventional Teflon laminated or similarly insulated stainless
steel wire 10 is disposed within a protective microcatheter (not
shown). Stainless steel wire 10 is approximately 0.010-0.020 inch
(0.254-0.508 mm) in diameter. In the illustrated embodiment, wire
10 is tapered at its distal end to form a conical section 12 which
joins a section 14 of reduced diameter which extends longitudinally
along a length 16 of wire 10. Section 16 then narrows gradually
down to a thin threadlike portion 18 beginning at a first bonding
location 20 and ending at a second bonding location 22.
The stainless steel wire 10, comprised of that portion disposed
within the microcatheter body, tapered section 12, reduced diameter
section 16 and threadlike section 18, is collectively referred to
as a core wire which typically is 50-300 cm in length.
In the illustrated embodiment the portion of the core wire
extending from tapered section 12 to second bonding location 22 is
collectively referred to as the grinding length and may typically
be between 20 and 50 cm. in length.
Reduced diameter portion 14 and at least part of sections 12 and
first bonding location 20 may be covered with an insulating Teflon
laminate 24 which encapsulates the underlying portion of wire 10 to
prevent contact with the blood.
A stainless steel coil 26 is soldered to the proximate end of
threadlike portion 18 of wire 10 at first bonding location 20.
Stainless steel coil 26 is typically 3 to 10 cm. in length and like
wire 10 has a diameter typically between 0.010 to 0.020 inch
(0.254-0.508 mm).
The distal end of stainless steel coil 26 is soldered to the distal
end of threadlike portion 18 of wire 10 and to the proximal end of
a platinum secondary coil 28 at second bonding location 22.
Secondary coil 28 itself forms a spiral or helix typically between
2 to 10 mm in diameter. The helical envelope formed by secondary
coil 28 may be cylindrical or conical. Like wire 10 and stainless
steel coil 26, a secondary coil 28 is between approximately 0.010
and 0.020 inch (0.254-0.508 mm) in diameter. The diameter of the
wire itself forming stainless steel coil 26 and coil 28 is
approximately between 0.001-0.005 inch.
The distal end of secondary coil 28 is provided with a platinum
soldered tip 30 to form a rounded and smooth termination to avoid
puncturing the aneurysm or tearing tissue.
Although prebiased to form a cylindrical or conical envelope,
secondary coil 28 is extremely soft and its overall shape is easily
deformed. When inserted within the microcatheter (not shown),
secondary coil 28 is easily straightened to lie axially within the
uicrocatheter. Once disposed out of the tip of the microcatheter,
secondary coil 28 formed the shape shown in FIG. 1 and may
similarly be loosely deformed to the interior shape of the
aneurysnm.
As will be described below in greater detail in connection with the
third embodiment of FIG. 3, after placement of secondary coil 28
within the interior of the aneurysm a direct current is applied to
wire 10 from a voltage source exterior to the body. The positive
cleavage on secondary coil 28 within the cavity of the aneurysm
causes a thrombus to form within the aneurysm by electrothrombosis.
Detachment of the tip occurs either: (1) by continued application
of current for a predetermined time when the portion 18 is exposed
to blood; or (2) by movement of the wire to expose portion 18 to
blood followed by continued current application for a predetermined
time. Ultimately, both threadlike portion and stainless steel coil
26 will be completely disintegrated at least at one point, thereby
allowing wire 10 to be withdrawn from the vascular space while
leaving secondary coil 28 embedded within the thrombus formed
within the aneurysm.
FIG. 2 illustrates in enlarged partially cross-sectional view a
second embodiment of the invention. Stainless steel core 32
terminates in a conical distal portion 34. Stainless steel coil 36,
shown in cross-sectional view, is soldered to distal portion 34 of
wire 32 at bonding location 38. The opposing end of the stainless
steel coil 36 is provided with a soldered, rounded platinum tip 40.
In the illustrated embodiment, stainless steel core wire 32 is
approximately 0.010 inch in diameter with the length of stainless
steel coil 36 being approximately 8 cm. with the longitudinal
length of platinum tip 40 being between 3 and 10 mm. The total
length of wire 32 from tip 40 to the proximal end is approximately
150 cm.
The embodiment of FIG. 2 is utilized in exactly the same manner as
described above in connection with FIG. 1 to form a thrombic mass
within an aneurysm or other vascular cavity. The embodiment of FIG.
2 is distinguished from that shown in FIG. 1 by the absence of the
extension of stainless core 32 through coil 36 to tip 44. In the
case of the embodiment of FIG. 2 no inner core or reinforcement is
provided within stainless steel coil 36. Threadlike portion 18 is
provided in the embodiment of FIG. 1 to allow increased tensile
strength of the wire. However, a degree of flexibility of the wire
is sacrificed by the inclusion even of threadlike tip 18, so that
the embodiment of FIG. 2 provides a more flexible tip, at least for
that portion of micro-guidewire constituting the stainless steel
coil 36.
It is expressly understood that the helical secondary coil tip of
the embodiment of FIG. 1 could similarly be attached to stainless
steel coil 36 of the embodiment of FIG. 2 without departing from
the spirit and scope of the invention.
Thinned and threadlike portion guidewires disposed concentrically
within coiled portions are well known and are shown in Antoshkiw,
"Disposable Guidewire", U.S. Pat. No. 3,789,841 (1974); Sepetka et
al., "Guidewire Device", U.S. Pat. No. 4,832,047 (1989); Engleson,
"Catheter Guidewire", U.S. Pat. No. 4,884,579 (1989); Samson et
al., "Guidewire for Catheters", U.S. Pat. No. 4,538,622 (1985); and
Samson et al., "Catheter Guidewire with Short Spring Tip and Method
of Using the Same". U.S. Pat. No. 4,554,929 (1985).
Turn now to the third embodiment of the invention as shown in FIG.
3. FIG. 3 shows an enlarged side view of a wire, generally denoted
by reference numeral 42, disposed within a microcatheter 44 shown
in cross-sectional view. Like the embodiment of FIG. 1, a stainless
steel coil 46 is soldered to a conical portion 48 of wire 22 at a
first bonding location 50. A thin threadlike extension 52 is then
longitudinally disposed within stainless steel coil 46 to a second
bonding location 54 where stainless steel wire 46 and threadlike
portion 52 are soldered to a soft platinum coil 56. Platinum coil
56 is not prebiased, nor does it contain any internal
reinforcement, but is a free end and open coil similar in that
respect to stainless steel coil 36 of the embodiment of FIG. 2.
However, platinum coil 56 is particularly distinguished by its
length of approximately 1 to 50 cm. and by its flexibility. The
platinum or platinum alloy used is particularly pliable and the
diameter of the wire used to form platinum coil 56 is approximately
0.001-0.005 inch in diameter. The distal end of platinum coil 56 is
provided with a smooth and rounded platinum tip 58 similar in that
respect to tips 30 and 40 of FIGS. 1 and 2, respectively.
When coil 56 is disposed within microcatheter 44, it lies along the
longitudinal lumen 60 defined by microcatheter 44. The distal end
62 of microcather 60 is then placed into the neck of the aneurysm
and the wire 42 is advanced, thereby feeding tip 58 in platinum
coil 56 into aneurysm 64 until bonding location 50 resides in the
neck of the aneurysm as best depicted in the diagrammatic
cross-sectional view of FIG. 4.
FIG. 4 illustrates the insertion of the embodiment of FIG. 3 within
a vessel 66 with distal tip of microcatheter 44 positioned near
neck 68 of aneurysm 64. Coil 56 is fed into aneurysm 64 until at
least a portion of stainless steel coil 46 is exposed beyond the
distal tip 62 of microcatheter 44. A positive electric current of
approximately 0.01 to 2 milliamps at 0.1-6 volts is applied to wire
42 to form the thrombus. Typically a thrombus will form within
three to five minutes. The negative pole 72 of voltage source 70 is
typically placed over and in contact with the skin.
After the thrombus has been formed and the aneurysm completely
occluded, tip 58 and coil 56 are detached from wire 42 by
electrolytic disintegration of at least one portion of stainless
steel coil 46. In the illustrated embodiment this is accomplished
by continued application of current until the total time of current
application is almost approzimately four minutes.
At least one portion of stainless steel coil 46 will be completely
dissolved through by electrolytic action within 3 to 10 minutes,
usually about 4 minutes. After separation by electrolytic
disintegration, wire 42, microcatheter 44 and the remaining portion
of coil 46 still attached to wire 42 are removed from vessel 66,
leaving aneurysm 64 completely occluded as diagrammatically
depicted in FIG. 5 by thrombus 74. It will be appreciated that the
time of disintegration may be varied by altering the dimensions of
the portions of the wire and/or the current
The process is practiced under fluoroscopic control with local
anesthesia at the groin. A transfemoral microcatheter is utilized
to treat the cerebral aneurysm. The platinum is not affected by
electrolysis and the remaining portions of the microcatheter are
insulated either by a Teflon lamination directly on wire 42 and/or
by microcatheter 44. Only the exposed portion of the wire 46 is
affected by the electrolysis.
It has further been discovered that thrombus 74 continues to form
even after detachment from wire 42. It is believed that a positive
charge is retained on or near coil 56 which therefore continues to
attract platelets, white blood cells, red blood cells and
fibrinogen within aneurysm 64.
Although the foregoing embodiment has been described as forming an
occlusion within a blood-filled vascular cavity by means of
electrothrombosis, the above disclosure must be read to expressly
include formation of the occlusion by mechanical mechanisms without
resort to the application of electrical current. A mechanical
mechanism which can be safely disposed into the vascular cavity to
impede, slow or otherwise initiate clotting of the blood or
formation of the occlusion is within the scope of the invention.
The insertion within the vascular cavity and maintenance therein of
an object with an appropriate blood-clotting characteristics can
and does in many cases cause the formation of an occlusion by
itself. Depicted in FIG. 6 is an embodiment of the invention
wherein such mechanical thrombosis can be achieved. Wire 10 has a
tapering end portion 14 covered with a Teflon laminate 24 similar
to that described in connection with the embodiment of FIG. 1. Wire
10 is attached by means of a mechanical coupling 100 to a platinum
coil 102 which has a plurality of filaments or fine hairs 104
extending therefrom. In the illustrated embodiment, hairs 104 have
a length as may be determined from the size of the vascular cavity
in which coil 102 is to be used. For example, in a small vessel
hair lengths of up to 1 mm are contemplated. An example of
polyester filaments or hairs attached to a coil which was not used
in electrothrombosis may be seen in the copending application
entitled Vasoocclusion Coil with Attached Fiberous Elements, filed
Oct. 2, 1991, Ser. No. 07/771,013.
Coil 102 has sufficient length and flexibility that it can be
inserted or coiled loosely into the vascular cavity. The length of
coil 102 need not be so long that the coil itself is capable of
being multiply folded on itself and fill or substantially fill the
vascular cavity. Hairs 104 extending from coil 102 serve to
substantially pack, fill or at least impede blood flow or access in
the vascular cavity. Hairs 104, which are generally inclined
backwardly away from extreme tip 106 when delivered, are thus
easily able to slide forward with little friction through
restrictions in the vessels and aneurysm. Additionally, hairs 104
do not have sufficient length, strength or sharpness to provide any
substantial risk or potential for a puncture of the thin vascular
wall. The plurality of hairs 104, when coiled within the vascular
cavity, provide an extremely large surface for attachment of blood
constituents to encourage and enhance the formation of a mechanical
occlusion within the vascular opening.
In the preferred embodiment, coil 102 is mechanically coupled to
thin tapered portion 104 of wire 10 by means of a small drop of
polyester 100. Polyester may be substituted for the gold solder of
the previously described embodiments in order to reduce concern or
risk of toxic reactions in the body.
Tip portion 104 may also be mechanically separated from wire 10 by
means other than electrolysis. One method is make the connection
between tip 104 and wire 10 by means of a spring loaded mechanical
clasp (not shown). The clasps are retained on tip 104 as long as
the clasps remain inside of the catheter, but spring open and
release tip 104 when extended from the catheter. The catheter and
clasps may then be removed from the insertion site. This type of
mechanical connection is described in the copending application
entitled, "Detachable Pusher-Vasoocclusive Coil Assembly with
Interlocking Coupling", filed Dec. 12, 1991 with Ser. No.
07/806,979 which is incorporated herein by reference and assigned
to Target Therapeutics Inc. An alternative nonresilient mechanical
ball and clasp capturing mechanism is described in the copending
application entitled "Detachable Pusher-Vasoocclusive Coil Assembly
with Interlocking Ball and Keyway Coupling", filed Dec. 12, 1991
with Ser. No. 07/806,912 which is also incorporated herein by
reference and assigned to Target Therapeutics Inc.
In another embodiment wire 10 and tip portion 104 screw into each
other and can be unscrewed from each other by rotation of the
catheter or wire with respect to tip 104. An extendable sheath (not
shown) in the microcatheter is advanced to seize tip 104 to prevent
its rotation with wire 10 during the unscrewing process. This type
of mechanical connection is described in the copending application
entitled "Detachable Pusher-Vasoocclusive Coil Assembly with
Threaded Coupling", filed Dec. 12, 1991 with Ser. No. 07/806,898
which is incorporated herein by reference and assigned to Target
Therapeutics Inc.
In any case the specific means disclosed here of mechanically
detaching tip 104 from wire 10 forms no part of the present
invention apart from its combination as a whole with other elements
of the invention. Specific disclosure of the mechanical means of
detachment have been set forth only for the purposes of providing
an enabling disclosure of the best mode presently known for
practicing the claimed invention.
Even where the occlusion is not formed by electrothrombosis,
separation of tip 104 may be effected by electrolysis. In such
situations, the electrolysing current may be concentrated on the
sacrificial stainless steel portion of tip 104 by disposition of an
insulative coating on the remaining platinum portion. For example,
tip 104 may be provided with a polyethylene coating save at least a
portion of the stainless length. This has the effect of decreasing
the time required to electrolytically sufficiently disintegrate the
steel portion to allow detachment of the platinum tip, which is an
advantageous feature in those cases where a large aneurysm must be
treated and a multiple number of coils must be deployed within the
aneurysm.
Notwithstanding the fact that wire 10 and platinum coil 102 in the
embodiment FIG. 6 or wire 10 and platinum coil 28, 36 and 56 in the
embodiments of FIGS. 1-5 are radiopaque, there is still some
difficulty when manipulating the device under fluoroscopy to be
able to determine the exact position or movement of the probe
relative to the aneurysm. This is particularly true when a large
number of coils are deployed and one coil then radiographically
hides another. FIG. 7 illustrates an improvement of, for example,
the embodiment of FIGS. 4 and 5. Microcatheter 144 is positioned so
that its distal end 162 within vessel 66 is positioned at the
opening aneurysm 64. Microcatheter 144 is provided with radiopaque
marker 108 at distal tip 162, a tip marker. Moving toward the
proximal end of microcatheter 144 is a second radiopaque marker
110, a proximal marker. Radiopaque markers 108 and 110 are, for
example, in the form of radiopaque rings made of platinum,
approximately 1-3 mm in longitudinal length along the axis of
microcatheter 144. Rings 110 and 108 are typically separated by
about 3 cm on microcatheter 144. Similarly, wire 10 has a
radiopaque marker 112 defined on it such that marker 112 on wire 10
is approximately with aligned with marker 110 on microcatheter 14
when coil 56 is fully deployed into aneurysm 64. Typically, full
deployment will place the solder or connection point 54 of the
order of 2-3 mm past opening 68 of aneurysm 64. Distal marker 108
on microcatheter 144 is used to facilitate the location of the
microcatheter tip, which can often be obscured by the coils which
have been previously deployed. The coils are a varying lengths
depending on the application or size of the aneurysm or vascular
cavity being treated. Coil lengths of 4-40 cm are common.
Therefore, even though the thinness of coil 56 may make it
difficult to see under standard fluoroscopy and even though the
fineness of wire 10 may similarly be obscured or partly obscured,
radiopaque markers 108, 110 and 112 are clearly visible.
Manipulation of wire 10 to proximal marker 110 can then easily be
observed under conventional fluoroscopy even when there are some
loss of resolution or fluoroscopic visual obstruction of the
coil.
Further, in the previous embodiments, such as that shown in FIGS. 4
and 5, when electrothrombosis is used to form the occlusion within
aneurysm 64, coil 56 is used as the electrical anode while the
cathode is a large skin electrode 72 typically conductively applied
to the groin or scalp. FIG. 9 illustrates an alternative embodiment
wherein microcatheter 144 is supplied with an end electrode 114
coupled to an electrical conductor 116 disposed along the length of
microcatheter 144. Wire 116 is ultimately led back to voltage
source 70 so that ring electrode 114 is used as the cathode during
electrothrombosis instead of an exterior skin electrode 72. With
the embodiment of FIG. 9 the electrical currents and electrical
current paths which are set up during the electrothrombosis
formation are local to the site of application which allows even
smaller currents and voltages to be used to initiate
electrothrombosis than in the situation when an exterior skin
electrode must be utilized. The electrothrombosic current
distributions are also better controlled and localized to the site
of the thrombus formation. The possibility of stray thrombus
formations occurring at unwanted sites or uncontrolled and possibly
unwanted electrical current patterns being established elsewhere in
the brain or body is therefor largely avoided.
Many alterations and modifications may be made by those having
ordinary skill in the art without departing from the spirit and
scope of the invention. Therefore, it must be understood that the
shape of the tip or distal platinum coil used in combination with
the wire according to the invention may be provided with a variety
of shapes and envelopes. In addition thereto, the composition of
the micro-guidewire tip may be made of elements other than platinum
including stainless steel beryllium, copper and various alloys of
the same with or without platinum. Still further, the diameter of
the wire, various of the wire described above and the stainless
steel coil immediately proximal to the detachable tip may be
provided with differing diameters or cross sections to vary the
times and current magnitudes necessary in order to effectuate
electrolytic detachment from the tip. Still further, the invention
may include conventional electronics connected to the proximal end
of the wire for determining the exact instant of detachment of the
distal tip from the wire.
Therefore, the illustrated embodiment has been set forth only for
the purposes of clarity and example and should not be taken as
limiting the invention as defined by the following claims, which
include all equivalent means whether now known or later
devised.
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