Endovascular electrolytically detachable wire for thrombus formation

BACKGROUND OF THE INVENTION

1. Field of the Invention a thrombus apparatus

<img file="PT101162A_D0001.tif" />

Patent Application Description of REGENTS OF THE

American UNIVERSITY, scientific superior Lakeside Oakland,

States

OF CALIFORNIA, North Educational and Research Institution established in 300

Drive, 22nd floor, California 94612-3550

States of America (inventors: Guido Guglielmi and Ivan Sepetka, residing in the United States of America) for DEVICE FOR FORMATION OF A CAVITY

VASCULAR

DESCRIPTION process and the endovascular vascular malformations and

The present invention relates to one for electrothrombotic formation in arteries, veins, aneurysms, anteriovenous fistulas.

2. Technique Description

Previous

Approximately 25,000 aneurysm ruptures

-1 intracranial rismas take place in North America each year. The first treatment proposal for intracranial aneurysm xoturas is to prevent further bleeding. There are currently three general treatment processes, called extravascular, endovascular, and extra-endovascular management.

The extravascular approach includes surgery or microsurgery of the aneurysm or local treatment to preserve the original artery. This treatment is common to intracranial berry aneurysms. The methodology comprises the phase of clamping the aneurysm neck by performing a suture connection to the neck, or involving the entire aneurysm. Each of these surgical procedures is performed by intrusive invasion into the body and is performed outside the aneurysm or target site. General anesthesia, craniotomy, brain retraction, and arachnoid dissection around the aneurysm neck and clip placement are typically required in such surgical procedures. 0 Surgical treatment of vascular intracranial aneurysms has an expected mortality rate of 4 to 8% with a morbidity ratio of 18 to 20%. Due to the expected mortality and morbidity ratio, the surgical procedure is often postponed while waiting for the best surgical time with the result that an additional percentage of patients will die from the disease or latent defect before surgery. For this reason the prior art has attempted alternative means of treatment.

At endovascular access, the interior of the aneurysm is penetrated using a microcatheter. Newly developed microcatheters, such as those presented by Engelson, Catheter Guidewire, US Patent 4,884,579, and as described in Engelson, Catheter for Guide wire Tracing, US Patent 4,739,768 (1988), allow navigating the cerebral arteries and entering the brain. cranial aneurysm.

In such procedures a balloon is typically attached to the end of the microcatheter and it is possible to insert the balloon into the aneurysm, dilate and detach it, allowing it to occlude the sac and neck with preservation of the original artery. While endovascular balloon embolization of

<img file="PT101162A_D0002.tif" />

Berry aneurysms are an attractive process in situations where extravascular surgical access is difficult, dilation of a balloon within the aneurysm carries some risk of aneurysm rupture due to the possible greater distension of portions of the blood and due to traction produced when highlights the balloon.

Although there are remedial procedures for treating aneurysm rupture during classic extravascular surgery, there is no satisfactory methodology if the aneurysm ruptures during an endovascular balloon embolization.

In addition, an ideal embolizing agent should itself adapt to the irregular shape of the inner walls of the aneurysm. Instead, in a balloon embolization, the aneurysm wall should conform to the shape of the balloon. This may not lead to a satisfactory result and further increases the risk of rupture.

Moreover, balloon embolization is not always possible. If the diameter of the empty balloon is too large to enter the intracerebral arteries, especially in cases of vasospasm, complications may occur with ruptured intracranial aneurysms. The procedure should then be deferred until the spasm is resolved and then favors the risk of further bleeding.

At extra-intravascular access, an aneurysm is surgically exposed or reached by stereotaxis with a probe. The aneurysm wall is then punctured from the outside, and various techniques are used to occlude the interior to prevent further bleeding.

These prior art processes include electrothrombosis, isobutyl cyanoacrylate embolization, pig bristle embolization, and ferromagnetic thrombosis.

In the use of electrothrombosis for extra-intravascular treatment, the tip of a positively charged electrode is surgically inserted into the aneurysm. A positive charge application attracts white blood cells, red blood cells, platelets and fibrinogen which are normally negatively charged to normal blood pH. The thrombus mass is thus formed in the aneurysm around the tip. Then the tip is removed from. See Mullan, Experiments with Surgical Thrombosis of intracranial Berry Aneurisms and Carotid Cavernous Fistulas, J. Neu rosurg., Vol. 41, December 1974; Hosobuchi, Electrotxombosis Carotid-Cavernous Fistula, J. Neurosurg., Vol. 42, January 1975; Araki et al., Electrically Induced Thrombosis for the Treatment of Intracranial Aneurisms and Angiomas, Excerpt Medical International Congress Series, Amsterdam 1965, Vol. 110, 651-654; Sawyer et al., Bio-Electric Phenomenon as an Etiological Factor in Intravascular Thrombosis, Am. J. Physiol., Vol. 175, 103-107 (1953); J. Piton et al., Selective Vascular Thromosis Induced by a Direct Electrical Current; Animal Experiments, J. Neuroradiology, Vol. 5, pages 139-152 (1978). However, each of these techniques includes some kind of intrusive procedure for accessing the aneurysm from the posterior body.

The prior art also envisioned the use of an adhesive liquid, isobutyl cyanoacrylate (IBCA), which polymerizes rapidly in contact with blood to form a firm mass. Adhesive fluid is injected into the aneurysm by pricking the bag with a small needle. In order to avoid der. In order to enter the original artery during IBCA injection, the blood flow through the original artery should be shortened or interrupted. Alternatively, a full balloon should be placed in the artery at the neck of the aneurysm to be injected. In addition to the risks caused by temporary blockage in the original artery, there is a risk of infiltration of the polymerizing adhesive into the original artery if it is not completely blocked with consequent occlusion of the artery.

Moreover, the prior art has used an air gun to inject pig bristles through the aneurysm wall to induce internal thrombosis. The success of this procedure involves exposing the aneurysm sufficiently to allow injection of the air gun and has not been convincingly shown to be successful for thrombotic formations.

Ferromagnetic thrombosis in the prior art comprises stereotactic placement of a magnetic probe against the aneurysm sac followed by injection into the aneurysm by means of an iron microsphere injection needle. The aggregation of the microspheres towards the extravascular magnet is followed by the formation of an interneurysmal thrombus. This treatment has not been entirely successful because of the risk of metal thrombus fragmentation when the extravascular magnet is removed. An iron powder suspension in methyl methyl methacrylate has been used to prevent fragmentation. Treatment has not been preferred by those skilled in the art because of the need to prick the aneurysm, the iris. As a result of occlusion of the original artery, the use of expensive and unusual equipment, the need for a craniectomy and general anesthesia and the need to penetrate brain tissue to reach the aneurysm.

Endovascular blood coagulation is also well known in the art and O'Reilly, Optical Fiber with Attachable Metallic Tip for Intravascular Laser Coagulation of Arteries, Veins, Aneurysms, Vascular Malformation and Arteriove nous Fistulas, US Patent 4,735,201 (1988) discloses a instrument using optically heat-generated laser. See also O'Reilly et al., Laser Induced Thermal Occlusion of Berry Aneurysms: Initial Experimental Results, Radiology, Vol. 171, NQ. 2, pages 471-74 (1989). O'Reilly places a tip inside an aneurysm by means of an endovascular microcatheter. The tip is attached by an adhesive to an optical fiber located along the microcatheter. Optical energy is transmitted along the optical fiber from a laser placed near the end of the microcatheter. Optical energy warms the tip to cauterize the tissue surrounding the aneurysm neck or other vascular opening to be occluded. The catheter is provided with a balloon located at or adjacent to its peripheral end to interrupt the blood flow at the site to be cauterized and occluded. Normally the blood flow will dissipate heat from the catheter tip, thus avoiding cauterization. Heat at the tip also serves to fuse the adhesive used to secure the tip to the peripheral end of the optical fiber. If all goes well, the tip can be detached from the fiber optic and left in place on the aneurysm neck as long as the cauterization is complete while melting the hot melt adhesive.

<img file="PT101162A_D0003.tif" />

No thrombus is formed from the heated tip. Instead, there is coagulation of the blood tissue surrounding the tip. Coagulation is a protein denaturation to form a connective binding tissue similar to what occurs when an egg's albumin is heated and coagulates from a clear liquid to a white opaque solid. The characteristics of the tissue and the composition of the coagulated tissue are however substantially different from those of the thrombus, which is formed by thrombotic aggregation of white and red blood cells, platelets and fibrinogen. The coagulative tissue is substantially softer than a thrombotic mass and can therefore be more easily dislodged.

O'Reilly's instrument depends at least in part on the success of the cauterization calculated not to occur later than the separation of the heated tip from the optical fiber. The heated tip should also be proportionally sized to the aneurysm neck to effectively coagulate the surrounding tissue to form a blockage in the neck. Tissue within the aneurysm is believed to remain substantially uncoagulated. In addition, the heat-fused adhesive that adheres to the tip in the optical fiber melts and is dispersed in the adjacent blood tissue where free particles resolidify into the intracranial blood stream with many of the same disadvantages that result from the fragmentation of ferromagnetic electrothrombosis.

Therefore, what is needed is an apparatus and methodology that avoids the various shortcomings and limitations of the prior art discussed above.

SUMMARY OF THE INVENTION

The present invention relates to a method of occluding within a retained blood vessel vascular cavity which comprises the steps of endovascularly positioning a wire and / or tip in the vicinity of an endovascular opening into the cavity. vascular. The metal wire may include a distinct structure at its peripheral end, which is called a point, in

<img file="PT101162A_D0004.tif" />

<img file="PT101162A_D0005.tif" />

in which case the remaining portion of the wire may be referred to as guide wire. The term metal wire is to be understood collectively to include both guide wire and spike and single wire without distinct spike structures. However, the point may also simply be the extension of the wire itself without substantial distinction in nature. A distal end of the metal wire is positioned within the vascular cavity to fill the cavity to mechanically occlude within the vascular cavity near the distal tip. The distal tip is detached from the guidewire (or wire) within the vascular cavity. As a result, the vascular cavity is occluded by the distal tip, and any thrombus formed by using the tip.

In one embodiment, the step of detaching the distal end of the guide wire (or the wire) comprises the step of mechanically detaching the distal end of the guide wire (or metal wire).

In another embodiment, the guide wire and tip (or metal wire) are used within a microcatheter and in the phase of detaching the distal tip of the guide wire (or metal wire), the guide wire and the tip (or wire) are displaced longitudinally within the microca teter. The microcatheter has a proximal radiopaque marking and / or tip. The guide wire and the tip (or wire) collectively have a unique radio-opaque marking. Moving the guidewire and tip (or wire) moves the single radiopaque marking to the proximity of the proximal marking on the microcatheter. At this point the tip will be completely inserted into the vascular cavity and the tip may be separated. It is therefore not necessary in this embodiment to be able to see the actual insertion of the tip prior to separation. Tip marking allows and enhances direct observation of the correct placement of the catheter tip within the opening of the vascular cavity.

In one embodiment the step of positioning the tip (or wire) in the vascular cavity to fill the cavity comprises the step of positioning a tip (or wire) having a plurality of expanding filaments. from it to fill the cavity.

<img file="PT101162A_D0006.tif" />

In another embodiment the step of positioning the tip (or wire) within the vascular cavity to fill the cavity comprises the step of positioning a long flexible tip (or wire) folded over itself a number of times to fill the cavity.

The present invention may also be characterized as a process for occlusion within a blood-containing vascular cavity therein comprising the steps of endovascularly positioning a metallic wire within a microcatheter near the endovascular opening for vascular cavity. The microcatheter has a distal tip electrode. The distal end of the metal wire is positioned within the vascular cavity to fill the cavity to form occlusion within the vascular cavity near the distal end of the metal wire by applying a current between the distal tip electrode and the distal end of the metal wire that fills the interior of the cavity. The distal end of the metal wire is detached from the metal wire to leave the distal end of the metal wire within the vascular cavity. As a result, the vascular cavity is occluded by the distal tip and any thrombus formed by using the tip.

The present invention also relates to a metal wire for use in forming an occlusion within a vascular cavity used in combination with a microcatheter comprising a metal wire core and a detachable elongate tip portion extending the core. metal wire over a predetermined linear length. The tip portion is adapted to fill the interior of the vascular cavity to form occlusion in the vascular cavity and is coupled to the distal portion of the core of the metal wire. As a result endovascular occlusion of the vascular cavity may be performed.

In one embodiment, the elongate tip portion is a substantially long, foldable segment adapted to be folded over itself a plurality of times to substantially fill said vascular cavity.

In another embodiment, the elongate tip portion is a segment adapted to be positioned in said vascular cavity and having a plurality of filaments extending therefrom to substantially fill said vascular cavity when positioned in its position. inside.

In yet another embodiment, the microcatheter has a pair of radio-opaque markings positioned above it and the metal wire core has a radio-opaque marking positioned on it. The marking on the wire core is positioned close to one of the pairs of markings on the micro catheter when the wire core is fully inserted. The other marking on the core of the wire marks the position of the catheter tip.

The present invention is further further characterized as a microcatheter system for use in forming an occlusion within a vascular cavity comprising a microcatheter having a distal end adapted for positioning near the vascular cavity. The distal end has an electrode positioned over it. A conductive guide wire is positioned within the microcatheter and longitudinally displaceable within it. 0 The guidewire comprises a core of metallic thread and an elongated tip portion extending the core of metallic thread during a predetermined linear extent. The tip portion is adapted to fill the interior of the vascular cavity to form occlusion in the vascular cavity. The tip portion is coupled to the distal portion of the wire core. Occlusion is formed by applying current between the tip portion and the electrode to the microcatheter when the tip portion is positioned in the vascular cavity. As a result, endovascular occlusion of the vascular cavity may be performed.

More generally, the present invention is directed to a method of occluding within a vascular cavity having blood within it which comprises the steps of positioning a body within the cavity to substantially impede the movement of blood in the cavity. . The body is employed in the cavity to form occlusion within the vascular cavity. As a result the vascular cavity is occluded by the body.

The phase of positioning the body in the vascular cavity comprises the phase of filling the cavity with the body to substantially obstruct the cavity.

In one embodiment, the cavity-filling step with the body comprises the step of obstructing the cavity with a detachable elongated tip of a bent metallic wire about itself a plurality of times in the cavity.

The step of positioning the body in the vascular cavity comprises positioning in the vascular cavity means to slow the movement of blood in the cavity in order to initiate occlusion formation in the cavity.

In another embodiment the body cavity filling step comprises the phase of blocking the cavity with a body having a composite filament shape.

The step of employing the body in the vascular cavity to form the occlusion comprises the step of applying an electric current to the body or mechanically forming the occlusion in the body or simultaneously both.

The present invention also relates to a metal wire for use in forming an occlusion within the vascular cavity used in combination with a microcatheter. The present invention comprises a wire core and a detachable elongate tip portion extending the wire core for a predetermined linear extent. 0 The wire core is adapted to be wound within the vascular cavity to form occlusion in the vascular cavity and is coupled to the distal portion of the wire core. The nose portion includes a first fragment for positioning in the cavity and a second segment for coupling the first portion to the wire core. The second segment is adapted to be electrolyzed by the application of current. Over the first segment is provided an insulating coating is applied. The second segment is left exposed to allow its selective electrolysis. As a result, endovascular occlusion of the vascular cavity may be performed.

The present invention may be better understood by reference to the following drawings in which each element is referenced by the same number.

DESCRIPTION OF DRAWINGS

Figure 1 is an enlarged partial cross-sectional side view of a first embodiment of the distal end of the guidewire and the tip of the present invention.

Figure 2 is an enlarged longitudinal sectional view of a second embodiment of the guidewire and tip of the present invention.

Figure 3 is an enlarged side view of a third embodiment with a portion of a microcatheter in section in a longitudinal view.

Figure 4 is a simplified representation of the metal wire of Figure 3 shown positioned within a simple cranial aneurysm.

Figure 5 is a representation of the metal wire of Figure 4 shown after electrolyte detachment of the tip.

Figure 6 is a plan view of another embodiment of the guidewire and the tip portion in which the tip has a plurality of thin polyester filament yarns.

Figures 7 and 8 are diagrammatic representations of the use of the invention in which position markings are used on the catater and wire to aid proper handling with fluoroscopy.

Figure 9 is a simplified cross-sectional view of the catheter and wire showing a base electrode located at the distal tip of the catheter.

The present invention and its various embodiments should be understood with the aid of the following detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Occlusion of arteries, aneurysm veins, vascular malformations, or arterial fistulas is caused by endovascular occlusion by endovascular insertion of a platinum tip into the vascular cavity. The vascular cavity is filled with the tip to obstruct blood flow or blood access to the cavity such that blood coagulates in the cavity and occlusion forms. The tip may be elongated and flexible such that it fills the cavity by virtue of a filamentous or branched tip structure. The tip is then separated from the wire mechanically or by electrolytic separation from the wire tip. The wire and microcatheter are then removed leaving the tip embedded in the thrombus formed within the vascular cavity. 0 Wire movement on the microcatheter is most easily followed if a proximal radiopaque marking is provided on the microcatheter and a corresponding indicator marking on the wire. Electrothrombosis is facilitated by placing the base electrode at the distal end of the microcatheter and passing a current between the microcatheter electrode and the tip.

When the tip of the wire is separated by electrolytic separation between the tip and the wire, a portion of the wire bonded between the tip and the body of the wire is made of stainless steel and is exposed to the bloodstream such that by By prolonged application of a positive current to the exposed portion, the exposed portion is corrosion-eliminated at at least one location and the tip is separated from the body of the wire.

Figure 1 is an enlarged side view of a first embodiment of the diaphragm end of the wire and the tip shown as a partial cut. A stainless steel wire 10 conventionally insulated by Teflon or the like is located within a protective microcatheter (not shown). The stainless steel wire has approximately a diameter of 0.254 to 0.508 mm (0.010 to 0.020 inches). In the illustrated embodiment, the wire 10 is thinned at its distal end to form a tapered section 12 which is connected with a small diameter section 14 extending longitudinally along a length 16 of wire 10 Section 16 on

<img file="PT101162A_D0007.tif" />

<img file="PT101162A_D0008.tif" />

It then gradually narrows to a thin filiform portion 18 that begins at a first binding location 20 and ends at a second binding location 22.

stainless steel wire 10 consisting of this portion located within the body of the microcatheter, the thin section 12, the small diameter section 16, and the filiform section 18 is designated together as a core wire or core of the wire and normally has 50 to 300 cm in length.

In the illustrated embodiment the portion of the core yarn extending from the thin section 12 to the second attachment location 22 is referred to as a sharp length and may generally be between 20 and 50 cm in length.

The small diameter portion 14 and at least part of the sections 12 and first bonding location 20 may be coated with Teflon laminate insulation 24 covering the underlying portion of the wire 10 to prevent contact with blood.

A stainless steel helical wire 26 is welded to the nearest end of the filiform portion 18 of the wire 10 at the first connection location 20. The stainless steel helical wire 26 is usually 3 to 10 cm long and, like wire 10 , typically has a diameter of 0.254 to 0.508 mm (0.010 to 0.020 inches).

The distal end of the stainless steel helical wire 26 is welded to the distal end of the filiform portion 18 of the wire 10 and to the proximal end of a secondary platinum helical wire 28 at the second connecting location 22. The secondary helical wire 28 in turn forms a spiral or helix usually 2 to 10 mm in diameter. The helical wrap formed by the secondary helical wire 28 may be either cylindrical or conical. Like wire 10 and stainless steel helical wire 26, secondary helical wire 28 has approximately a diameter of 0.254 to 0.508 mm (0.010 to 0.020 inches). The diameter of the wire itself forming the helical wire 26 and the helical wire 28 is approximately 0.0254 to 0.127 mm (0.001 to 0.005 inches).

The distal end of the secondary helical wire 28 has a welded platinum tip 30 so as to form a smooth rounded end to prevent puncture of the aneurysm or tearing of the tissue.

Although it has been bent to form a cylindrical or conical wrap, the secondary helical wire 28 is extremely soft and its overall shape can be easily deformed. When inserted into the microcatheter (not shown), the secondary helical wire 28 is easily ground so that it is axially disposed relative to the microcatheter. Once located outside the tip of the microcatheter, the secondary helical wire 28 takes the form shown in Figure 1 and can likewise be deformed without difficulty to form the interior of the aneurysm.

As described in more detail below with respect to the third embodiment of Figure 3, after placement of the secondary helical wire 28 within the aneurysm, direct current is applied to wire 10 from an external voltage source. to the body. The positive charge. Secondary coil 28 within the aneurysm cavity causes a thrombus to form within the aneurysm by electrothrombosis. Bridge release occurs: (1) by prolonged application of current for a predetermined period when portion 18 is exposed to blood; or (2) by moving the wire to expose portion 18 to blood followed by the application of prolonged current for a predetermined period. Finally, both the filiform portion and the stainless steel helical wire 26 are completely disintegrated at least at one point, thereby allowing the wire 10 to be withdrawn from the vascular space leaving the secondary helical wire 28 embedded in the thrombus formed within the aneurysm.

Figure 2 illustrates in an enlarged partial sectional view a second embodiment of the present invention. The stainless steel core 32 terminates in a distal conical portion 34. The stainless steel helical wire 36, shown in sectional view, is welded to the distal portion 34 of the wire 32 at the location of the connector 38. The opposite end of the steel helical wire stainless 36 has a round platinum tip

<img file="PT101162A_D0009.tif" />

<img file="PT101162A_D0010.tif" />

given 40 welded. In the illustrated embodiment, the stainless steel core wire 32 has a diameter of approximately 0.254 mm (0.010 inches) with the length of the stainless steel helical wire being between 3 and 10 mm. The total length of wire 32 from tip 40 to the nearest end is approximately 150 cm.

The embodiment of Figure 2 is used in exactly the same manner as previously described in connection with Figure 1 to form a thrombotic mass within the aneurysm or other vascular cavity. The embodiment of Figure 2 differs from that shown in Figure 1 by the absence of extension of the stainless steel core 32 from the helical wire 36 to the tip 40. In the case of the embodiment of Figure 2 there is no inner core or reinforcement within the stainless steel helical wire 36. The filiform portion 18 has in the embodiment of Figure 1 the function of increasing the strength of the wire. However, the degree of flexibility of the yarn is sacrificed by including even the filiform tip 18, such that the embodiment of Figure 2 gives rise to a more flexible tip, at least in the portion of the micro-guide yarn consisting of stainless steel helical wire 36.

It will be expressly contemplated that the secondary coil tip of the embodiment of Figure 1 could similarly be attached to the stainless steel coil 36 of the embodiment of Figure 3 without departing from the spirit and scope of the present invention.

Thin, threadlike metal guidewires concentrically positioned within helical portions are well known and are described in Antoshkiw, Disposable Guidewire, US Patent 3,789,841 (1974); Sepetka et al., Guidewire Device, US Patent 4,832,047 (1989); Engelson, Catheter Guidewire, US Patent 4,884,579 (1989); Samson et al., Guidewire for Catheters, US Patent 4,538,622 (1985); Samson et al., Catheter Guidewire with Short Spring Tip and Method of Using the Same, US Patent 4,554,929 (1985).

Referring now to the third embodiment of the present invention shown in Figure 3 is an enlarged side view of a metal wire, generally designated by reference to numeral 42, positioned within a microcatheter 44 shown in section. As in the embodiment of Figure 1, a stainless steel helical wire 46 is welded to a conical portion 48 of wire 22 at a first connection location 50. Thereafter a thin filiform extension 52 is longitudinally disposed within the stainless steel helical wire 46 to a second connection location 54 in which the stainless steel wire 46 and the wire portion 52 are welded to a flexible platinum helical wire 56 . The platinum helical wire is not biased and does not contain any internal reinforcement, but is instead a free and open helical wire similar in this respect to the stainless steel helical wire 36 of the embodiment of Figure 2.

However, the platinum helical wire 56 is particularly characterized by its length of approximately 1 to 50 cm and its flexibility. The platinum or platinum alloy used is particularly flexible and the diameter of the wire used to form platinum helical wire 56 is approximately 0.0254 to 0.127 mm (0.001 to 0.005 inches). The distal end of the platinum helical wire 56 has a smooth, rounded platinum tip 58 similar in this respect to tips 30 and 40 of Figures 1 and 2 respectively.

When the helical wire 56 is located within the microcatheter 44, it is disposed along the longitudinal lumen 60 defined by the microcatheter 44. The distal end 62 of the microcatheter 60 is then placed on the aneurysm neck and the wire 42 is advanced thereby penetrating the tip 58 into the platinum helical wire 56 in the aneurysm 64 until the connection location 50 resides in the aneurysm neck, as shown in the section diagram of Figure 4.

Figure 4 illustrates the insertion of the embodiment of Figure 3 into a vessel 66 with the distal tip of microcatheter 44 positioned near neck 68 of aneurysm 64. The helical wire 56 is penetrated into aneurysm 64 to at least one The portion of the stainless steel helical wire 46 is exposed beyond the distal tip 62 of the microcatheter 44. A positive electrical current of approximately 0.01 to 2 mA is applied at a voltage of 0.1 to 6 V to the wire 42 to form a thrombus. Usually a thrombus is formed within three to five minutes. The negative pole 72 of the voltage source 70 is usually placed on and in contact with the skin.

After the thrombus has formed and the aneurysm is completely occluded, the tip 58 and the helical wire 56 are detached from the wire 42 by electrolytically disintegrating at least a portion of the stainless steel helical wire 46. In the illustrated embodiment this operation It is effected by prolonged current application until the total current application time is approximately four minutes.

At least a portion of the stainless steel helical wire 46 dissolves completely by electrolytic action within the range of 3 to 10 minutes, usually about 4 minutes. After electrolytic disintegration separation, wire 42, microcatheter 44, and the remaining portion of helical wire 46 still attached to wire 42 are withdrawn from vessel 66, leaving completion aneurysm 64 occluded as shown schematically in Figure 5 through the thrombus. 74 It should be noted that the disintegration period may be varied by changing the dimensions of the wire portions and / or chain.

The procedure is performed under fluoroscopic control with local groin anesthesia. A transfemoral microca teter is used to treat the cerebral aneurysm. Platinum is not affected by electrolysis and the remaining parts of the microcatheter are isolated by a Teflon laminate directly on wire 42 and / or microcatheter 44. Only the exposed portion of wire 46 is affected by electrolysis.

Thrombus 74 has also been found to continue to form even after it has been detached from wire 42. The positive charge is thought to be retained on or near the helical wire 56 and thus continues to attract platelets, the blood cells. white blood cells, red blood cells and fibrin within the aneurysm 64.

Although the foregoing embodiment has been described as occluding within a blood-filled vascular cavity by electrothrombosis, this description is to be understood as expressly including the formation of occlusion by mechanical mechanisms without recourse. application of an electric current. A mechanical mechanism may be reliably located in the vascular cavity to prevent, retard or otherwise initiate blood coagulation or occlusion formation within the scope of the present invention. Insertion into and storage of the vascular cavity with an object having the appropriate blood coagulation characteristics can and often causes occlusion on its own. Figure 6 shows an embodiment of the invention whereby mechanical thrombosis can be achieved as described. The wire 10 has a tapered end portion 14 covered with a Teflon laminate 24 similar to that described with respect to the embodiment of Figure 1. The wire 10 is coupled by a mechanical coupling 100 to a platinum helical wire 102 having a plurality of thin filaments or threads 104 extending therefrom. In the illustrated embodiment, the thin wires 104 have a length that can be terminated from the size of the vascular cavity in which the helical wire 102 is used. For example, in a small vessel the filament lengths are 1 mm. . An example of thin stranded polyester filaments or yarns that are not used in electrothrombosis can be seen in United States Patent Application pending Vasoocclusion Coil with Attached Fiberous Elements, filed October 2, 1991 , with serial number 07/771 013.

The helical wire 102 is of sufficient length and flexibility that it can be loosely inserted or wound into the vascular cavity. The length of the helical wire need not be so large that the helical wire itself is capable of being folded multiple times over itself and substantially filling or filling the vascular cavity. The thin yarns 104 extending from the helical yarn

<img file="PT101162A_D0011.tif" />

Thus 102 serve to fill, fill or at least prevent blood from flowing or accessing the vascular cavity. The thin wires 104, which are generally angled backwards away from the tip end 106 at the beginning of the operation, are thus easily capable of sliding forward with little friction through vessel and aneurysm restrictions. In addition, the thin wires 104 are not of sufficient length, strength or strength to provide any substantial or potential risk of puncturing the thin vascular wall. The plurality of thin strands 104, when wound within the vascular cavity, provide an extremely large surface for adhesion of the blood constituents to. promote and intensify the formation of a mechanical occlusion within the vascular opening.

In the preferred embodiment, the helical yarn 102 is mechanically coupled to the thin thin portion 104 of the metal yarn 10 by means of a small drop of polyester 100. The polyester may be replaced by gold welding in accordance with the described embodiments. previously to reduce the risk of toxicity reactions in the body.

The tip portion 104 may also be mechanically separated from the metal wire by means other than electrolysis. One method is based on a connection between the tip 104 and the metal wire 10 by means of a spring or spring mechanical hook (not shown). The hooks are retained at tip 104 while inside the Catheter, but the spring opens and releases tip 104 as it exits the catheter. The catheter and hooks can then be removed from the insertion site. This type of mechanical connection is described in United States Patent Application pending Detachable Pusher-Vasoocclusive Coil Assembly with Interlocking Coupling filed December 12, 1991 under serial number 07/806 979, which is given in as reproduced herein by reference, the applicant of which is Target Therapeutics Inc .. In the United States Patent Application pending Detachable Pusher-Vasoocclusive Coil Assembly with. Interlocking Bali and Keyway Coupling filed December 12, 1991 with serial number 07/806 912 which also

<img file="PT101162A_D0012.tif" />

As reproduced herein by reference, the subject of which is Target Therapeutics Inc., an alternative mechanical capture mechanism consisting of a hook and a non-resilient ball is described.

In another embodiment the metallic wire 10 and the tip portion 104 are screwed together and can be separated by unscrewing them by rotation of the catheter or wire with respect to the tip 104. An extendable sheath is advanced ( not shown) on the microcatheter to secure the tip 104 to prevent rotation thereof with the metal wire 10 during the unscrewing process. This type of mechanical connection is described in the United States Patent Application pending Detachable Pusher Vasoocclusive Coil Assembly with Threaded Coupling filed December 12, 1991 under serial number 07/806 898, which is also is as reproduced herein by reference, the applicant of which is Target Therapeutics Inc ..

In any event, the mechanical means described for mechanically separating the tip 104 from the metal wire 10 is part of the present invention in addition to their combination as a whole with other elements of the invention. The specific description of the mechanical release means has been provided solely for the purpose of providing a description which enables the best known method of practicing the present invention to be understood at present.

Even when occlusion is not formed by electrothrombosis, separation of the tip 104 may be effected by electrolysis. In these situations, the electrolysis current may be concentrated on the portion of the stainless steel tip 104 to be sacrificed by arranging an insulating coating on the remaining platinum portion. For example, the tip 104 may have a polyethylene coating except at least a portion of the length of stainless steel. This effect has the effect of decreasing the time required to sufficiently electrolytically disintegrate the steel portion to allow release of the platinum tip, which is an advantageous feature in cases where it is necessary to treat a platelet aneurysm. large and need to penetrate multiple heli20 wires

<img file="PT101162A_D0013.tif" />

in the aneurysm.

Despite the fact that the metal wire and platinum helical wire 102 .. the embodiment of Figure 6 or the metal wire 10 and platinum helical wire 28, 36 and 56 in the embodiments of Figures 1 to 5 are In radio-opaque conditions, there is still some difficulty when manipulating the device with fluoroscopy in order to determine the exact position of probe movement relative to the aneurysm. This is particularly true when many helical wires are penetrated and one helical wire is radiographically slapped on one another. Figure Ί illustrates an improvement of the embodiment of e.g. Figures 4 and 5. Microcatheter 144 is positioned such that its distal end 162 within vessel 66 is positioned at the opening of aneurysm 64. Microcatheter 144 has a radio opaque marking 108 at the distal tip 162, a tip marking. Moving to the proximal end of microcatheter 144 is a second radiopaque marking 110, a proximal marking. Radio-opaque markings 108 and 110 are, for example, in the form of platinum radio-opaque rings, with a longitudinal length of approximately 1 to 3 mm along the axis of microcatheter 144. Rings 110 and 108 are normally separated. about 3 cm over the microcatheter 144. Similarly, the metallic wire 10 has a radiopaque marking 112 defined over it such that the marking 112 on the metallic wire 10 is approximately aligned with the marking 110 on the microcatheter 14 when the helical wire 56 is fully inserted. in the aneurysm 64. Normally, the full insertion places the hard soldering or bonding point 54 at an Oxdem distance of 2 to 3 mm after opening 68 of the aneurysm 64. Distal marking 108 on microcatheter 144 is used to facilitate the tipping of the microcatheter tip, which can often be obscured by previously inserted helical wires. The helical wires are of different lengths depending on the application or size of the aneurysm or vascular cavity to be treated. Helical wire lengths of 4 to 40 cm are common. Therefore, even if the small diameter of the helical wire 56 can make visualization difficult

<img file="PT101162A_D0014.tif" />

in normal fluoroscopy and even if the small diameter of the wire 10 can likewise be obscured in whole or in part, the radiopaque markings 108, 110 and 112 are clearly visible. Any manipulation of the wire 10 along the proximal marking 110 can be easily observed by conventional fluoroscopy even when there is some loss of resolution or visual obstruction in the helical wire fluoroscopy.

In addition, in previous embodiments, such as those shown in Figures 4 and 5, when using electrothrombosis to form occlusion within vascular aneurysm 64, the helical wire 56 is used as an anode while the cathode is an electrode. large on the skin 72 normally applied to the groin or ** the scalp so that the current conducts. Figure 9 illustrates an alternative embodiment in which microcatheter 144 is provided with an end electrode coupled to an electrical conductor.

116 positioned along the length of microcatheter 144. The wire 116 is finally connected to a voltage source 70 such that the ring electrode 114 is used as a cathode during electrothrombosis rather than using an external dermal electrode. 72 With the embodiment of Figure 9, the electrical currents and electrical current pathways established during the formation of electrothrombosis are local at the application site allowing even lower electrical currents and voltages to initiate electrothrombosis than at the electrotrombosis. situation where an external dermal electrode is used. The distributions of electrothrombotic currents are also controlled and located more perfectly at the site of thrombus formation. The possibility of misplaced thrombus formation occurring in undesirable or uncontrolled locations and possibly setting undesirable patterns of electrical currents elsewhere in the brain or body is thus greatly avoided.

Many changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it should be understood that the shape of the platinum distal tip or helical wire used in combination with the metal wire according to the present invention may be of various shapes and various

<img file="PT101162A_D0015.tif" />

<img file="PT101162A_D0016.tif" />

casings. In addition, the micro-guide wire tip composition may be made of elements other than platinum, including stainless steel, beryllium, copper and various alloys of these metals with or without platinum. In addition to the foregoing, the diameters of the wire, the different parts of the wire described and the stainless steel helical wire may have different values ​​or sections to vary the time periods and current values ​​required in order to effect the electrolyte release of the tip. Furthermore, the present invention may include conventional electronic devices connected to the proximal end of the metal wire to determine the exact time to release the distal end of the metal wire.

Accordingly, the illustrated embodiment has been presented for purposes of clarity and example only and should not be construed as limiting the invention in any way as defined in the following claims, which include all equivalent means, whether or not already known or described below.