USRE42662E1 - Endovascular electrolytically detachable wire and tip for the formation of thrombus in arteries, veins, aneurysms, vascular malformations and arteriovenous fistulas - Google Patents

Abstract

An artery, vein, aneurysm, 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.

Description

This application is a divisional of application Ser. No. 08/485,821 filed Jun. 6, 1995, now abandoned, 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 in turn was is a continuation of application Ser. No. 07/840,211, filed on Feb. 24, 1992, now issued as U.S. Pat. No. 5,354,295, and which in its turn was is 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.

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 Tracking”, U.S. Pat. No. 4,739,768 (1988), allow navigation into the cerebral arteries and entry into a 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 increases 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 perforated from the outside and various techniques are used to occlude the interior in order to prevent it from rebleeding. These prior art techniques include electrothrombosis, 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 Sugical 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; Araki et al., “Electrically Induced Thrombosis for the Treatment of Intracranial Aneurysms 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 a 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 or 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 thrombic 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 aneurysm by an injecting needle of iron microspheres. Aggregation of the microspheres through the extravascular magnet is followed by interneuysmatic thrombus. 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 Arteies, 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 to 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 an 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 disposed 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 separation. The tip marker 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 microcatheter 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 microcatheter has a pair of radioopaque markers disposed thereon and the core wire has a radioopaque marker 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 body 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 both 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

FIGS. 1 and 1A are enlarged partially cross-sectioned side views of a first embodiment of the distal end of the guidewire and tip of the invention.

FIGS. 2 and 2A are enlarged longitudinal cross sections 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 ofFIG. 3 shown disposed within a simple cranial aneurysm.

FIG. 5 is a depiction of the wire ofFIG. 4 shown after electrolytic detachment of the tip.

FIG. 6 is a 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 insulatedstainless steel wire10 is disposed within a protective microcatheter (not shown).Stainless steel wire10 is approximately 0.010-0.020 inch (0.254-0.508 mm) in diameter. In the illustrated embodiment,wire10 is tapered at its distal end to form aconical section12 which joins asection14 of reduced diameter which extends longitudinally along alength16 ofwire10.Section16 then narrows gradually down to a thinthreadlike portion18 beginning at afirst bonding location20 and ending at asecond bonding location22.

Thestainless steel wire10, comprised of that portion disposed within the microcatheter body, taperedsection12, reduceddiameter section16 andthreadlike section18, 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 taperedsection12 tosecond bonding location22 is collectively referred to as the grinding length and may typically be between 20 and 50 cm. in length.

Reduceddiameter portion14 and at least part ofsections12 andfirst bonding location20 may be covered with an insulatingTeflon laminate24 which encapsulates the underlying portion ofwire10 to prevent contact with the blood.

Astainless steel coil26 is soldered to the proximate end ofthreadlike portion18 ofwire10 atfirst bonding location20.Stainless steel coil26 is typically 3 to 10 cm. in length and likewire10 has a diameter typically between 0.010 to 0.020 inch (0.254-0.508 mm).

The distal end ofstainless steel coil26 is soldered to the distal end ofthreadlike portion18 ofwire10 and to the proximal end of a platinumsecondary coil28 atsecond bonding location22.Secondary coil28 itself forms a spiral or helix typically between 2 to 10 mm. in diameter. The helical envelope formed bysecondary coil28 may be cylindrical or conical. Likewire10 andstainless steel coil26,secondary coil28 is between approximately 0.010 and 0.020 inch (0.254-0.508 mm) in diameter. The diameter of the wire itself formingstainless steel coil26 andcoil28 is approximately between 0.001-0.005 inch.

The distal end ofsecondary coil28 is provided with a platinum solderedtip30 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 coil28 is extremely soft and its overall shape is easily deformed. When inserted within the microcatheter (not shown),secondary coil28 is easily straightened to lie axially within the microcatheter. Once disposed out of the tip of the microcatheter,secondary coil28 forms the shape shown inFIG. 1 and may similarly be loosely deformed to the interior shape of the aneurysm.

As will be described below in greater detail in connection with the third embodiment ofFIG. 3, after placement ofsecondary coil28 within the interior of the aneurysm a direct current is applied to wire10 from a voltage source exterior to the body. The positive charge onsecondary coil28 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 theportion18 is exposed to blood; or (2) by movement of the wire to exposeportion18 to blood followed by continued current application for a predetermined time. Ultimately, both threadlike portion andstainless steel coil26 will be completely disintegrated at least at one point, thereby allowingwire10 to be withdrawn from the vascular space while leavingsecondary coil28 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 core32 terminates in a conicaldistal portion34.Stainless steel coil36, shown in cross-sectional view, is soldered todistal portion34 ofwire32 atbonding location38. The opposing end of thestainless steel coil36 is provided with a soldered,rounded platinum tip40. In the illustrated embodiment, stainlesssteel core wire32 is approximately 0.010 inch in diameter with the length ofstainless steel coil36 being approximately 8 cm. with the longitudinal length ofplatinum tip40 being between 3 and 10 mm. The total length ofwire32 fromtip40 to the proximate end is approximately 150 cm.

The embodiment ofFIG. 2 is utilized in exactly the same manner as described above in connection withFIG. 1 to form a thrombic mass within an aneurysm or other vascular cavity. The embodiment ofFIG. 2 is distinguished from that shown inFIG. 1 by the absence of the extension ofstainless core32 throughcoil36 to tip40. In the case of the embodiment ofFIG. 2 no inner core or reinforcement is provided withinstainless steel coil36.Threadlike portion18 is provided in the embodiment ofFIG. 1 to allow increased tensile strength of the wire. However, a degree of flexibility of the wire is sacrificed by the inclusion even ofthreadlike tip18, so that the embodiment ofFIG. 2 provides a more flexible tip, at least for that portion of the micro-guidewire constituting thestainless steel coil36.

It is expressly understood that the helical secondary coil tip of the embodiment ofFIG. 1 could similarly be attached tostainless steel coil36 of the embodiment ofFIG. 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); Engelson, “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 inFIG. 3.FIG. 3 shows an enlarged side view of a wire, generally denoted byreference numeral42, disposed within amicrocatheter44 shown in cross-sectional view. Like the embodiment ofFIG. 1, astainless steel coil46 is soldered to aconical portion48 ofwire22 at afirst bonding location50. A thinthreadlike extension52 is then longitudinally disposed withinstainless steel coil46 to asecond bonding location54 wherestainless steel wire46 andthreadlike portion52 are soldered to asoft platinum coil56.Platinum coil56 is not prebiased, nor does it contain any internal reinforcement, but is a free and open coil similar in that respect tostainless steel coil36 of the embodiment ofFIG. 2.

However,platinum coil56 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 formplatinum coil56 is approximately 0.001-0.005 inch in diameter. The distal end ofplatinum coil56 is provided with a smooth androunded platinum tip58 similar in that respect totips30 and40 ofFIGS. 1 and 2, respectively.

Whencoil56 is disposed withinmicrocatheter44, it lies along thelongitudinal lumen60 defined bymicrocatheter44. Thedistal end62 ofmicrocatheter60 is then placed into the neck of the aneurysm and thewire42 is advanced, thereby feedingtip58 inplatinum coil56 intoaneurysm64 until bondinglocation50 resides in the neck of the aneurysm as best depicted in the diagrammatic cross-sectional view ofFIG. 4.

FIG. 4 illustrates the insertion of the embodiment ofFIG. 3 within avessel66 with distal tip ofmicrocatheter44 positioned nearneck68 ofaneurysm64.Coil56 is fed intoaneurysm64 until at least a portion ofstainless steel coil46 is exposed beyond thedistal tip62 ofmicrocatheter44. A positive electric current of approximately 0.01 to 2 milliamps at 0.1-6 volts is applied to wire42 to form the thrombus. Typically a thrombus will form within three to five minutes. Thenegative pole72 ofvoltage source70 is typically placed over and in contact with the skin.

After the thrombus has been formed and the aneurysm completely occluded,tip58 andcoil56 are detached fromwire42 by electrolytic disintegration of at least one portion ofstainless steel coil46. In the illustrated embodiment this is accomplished by continued application of current until the total time of current application is almost approximately four minutes.

At least one portion ofstainless steel coil46 will be completely dissolved through by electrolytic action within 3 to 10 minutes, usually about 4 minutes. After separation by electrolytic disintegration,wire42,microcatheter44 and the remaining portion ofcoil46 still attached to wire42 are removed fromvessel66, leavinganeurysm64 completely occluded as diagrammatically depicted inFIG. 5 bythrombus74. 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 onwire42 and/or bymicrocatheter44. Only the exposed portion of thewire46 is affected by the electrolysis.

It has further been discovered thatthrombus74 continues to form even after detachment fromwire42. It is believed that a positive charge is retained on ornear coil56 which therefore continues to attract platelets, white blood cells, red blood cells and fibrinogen withinaneurysm64.

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 inFIG. 6 is an embodiment of the invention wherein such mechanical thrombosis can be achieved.Wire10 has a taperingend portion14 covered with aTeflon laminate24 similar to that described in connection with the embodiment ofFIG. 1.Wire10 is attached by means of amechanical coupling100 to aplatinum coil102 which has a plurality of filaments orfine hairs104 extending therefrom. In the illustrated embodiment,hairs104 have a length as may be determined from the size of the vascular cavity in whichcoil102 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.

Coil102 has sufficient length and flexibility that it can be inserted or coiled loosely into the vascular cavity. The length ofcoil102 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.Hairs104 extending fromcoil102 serve to substantially pack, fill or at least impede blood flow or access in the vascular cavity.Hairs104, which are generally inclined backwardly away fromextreme tip106 when delivered, are thus easily able to slide forward with little friction through restrictions in the vessels and aneurysm. Additionally,hairs104 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 ofhairs104, 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,coil102 is mechanically coupled to thin taperedportion104 ofwire10 by means of a small drop ofpolyester100. 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 portion104 may also be mechanically separated fromwire10 by means other than electrolysis. One method is make the connection betweentip104 andwire10 by means of a spring loaded mechanical clasp (not shown). The clasps are retained ontip104 as long as the clasps remain inside of the catheter, but spring open andrelease tip104 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 anotherembodiment wire10 andtip portion104 screw into each other and can be unscrewed from each other by rotation of the catheter or wire with respect to tip104. An extendable sheath (not shown) in the microcatheter is advanced to seizetip104 to prevent its rotation withwire10 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 detachingtip104 fromwire10 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 oftip104 may be effected by electrolysis. In such situations, the electrolysing current may be concentrated on the sacrificial stainless steel portion oftip104 by disposition of an insulative coating on the remaining platinum portion. For example,tip104 may be provided with a polyethylene coating save at least a portion of the stainless steel 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 thatwire10 andplatinum coil102 in the embodimentFIG. 6 orwire10 andplatinum coil28,36 and56 in the embodiments ofFIGS. 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 ofFIGS. 4 and 5.Microcatheter144 is positioned so that itsdistal end162 withinvessel66 is positioned at theopening aneurysm64.Microcatheter144 is provided withradiopaque marker108 atdistal tip162, a tip marker. Moving toward the proximal end ofmicrocatheter144 is a secondradiopaque marker110, a proximal marker.Radiopaque markers108 and110 are, for example, in the form of radiopaque rings made of platinum, approximately 1-3 mm in longitudinal length along the axis ofmicrocatheter144.Rings110 and108 are typically separated by about 3 cm onmicrocatheter144. Similarly,wire10 has aradiopaque marker112 defined on it such thatmarker112 onwire10 is approximately with aligned withmarker110 onmicrocatheter14 whencoil56 is fully deployed intoaneurysm64. Typically, full deployment will place the solder orconnection point54 of the order of 2-3 mm past opening68 ofaneurysm64.Distal marker108 onmicrocatheter144 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 ofcoil56 may make it difficult to see under standard fluoroscopy and even though the fineness ofwire10 may similarly be obscured or partly obscured,radiopaque markers108,110 and112 are clearly visible. Manipulation ofwire10 toproximal marker110 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 inFIGS. 4 and 5, when electrothrombosis is used to form the occlusion withinvascular aneurysm64,coil56 is used as the electrical anode while the cathode is alarge skin electrode72 typically conductively applied to the groin or scalp.FIG. 9 illustrates an alternative embodiment whereinmicrocatheter144 is supplied with anend electrode114 coupled to anelectrical conductor116 disposed along the length ofmicrocatheter144.Wire116 is ultimately led back tovoltage source70 so thatring electrode114 is used as the cathode during electrothrombosis instead of anexterior skin electrode72. With the embodiment ofFIG. 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 therefore 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.

Claims (10)

1. A wire for use in the formation of an occlusion within a vascular cavity in conjunction with a microcatheter having an interior lumen, said wire comprising:

a metal coil having a first shape which conforms to said microcatheter lumen when within the microcatheter, and said metal coil forming an unbiased, regular cylindrical or unbiased single regular conical envelope when disposed out of said microcatheter.

2. The wire ofclaim 1 wherein the wire comprises platinum.

3. The wire ofclaim 1 wherein the diameter of the coil is approximately 0.001-0.005 inch.

4. The wire ofclaim 1 wherein the diameter of the coil is approximately 0.010-0.020 inch.

5. The wire ofclaim 1 wherein the diameter of the envelope is approximately 2-10 mm.

6. The wire ofclaim 1 wherein the envelope is conical.

7. The wire ofclaim 1 wherein the envelope is cylindrical.

8. The wire ofclaim 1 further comprising a plurality of filaments extending from said first shape.

9. The wire ofclaim 8 wherein the filaments comprise polyester.

10. The wire ofclaim 2 wherein the coil is prebiased to form said cylindrical or conical envelope.

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