Clot capture coil

Regents of The University ofCalifornia C.112451 ο*τ TObii

Clot capture coil 125612/3

Field of the Invention

The present invention relates to medical devices that are useful in treatingthromboembolic disorders and for removal of foreign bodies in the vascular system.

Background of the Invention

Thromboembolic disorders, such as stroke, pulmonary embolism, peripheral thrombosis,atherosclerosis, and the like, affect many people. These disorders are a major cause of morbidityand mortality in the United States.

Thromboembolic events are characterized by an occlusion of a blood vessel. Theocclusion is caused by a clot which is viscoelastic (jelly like) and is comprised of platelets,fibrinogen and other clotting proteins.

When an arteiy is occluded by a clot, tissue ischemia (lack of oxygen and nutrients)develops. The ischemia will progress to tissue infarction (cell death) if the occlusion persists.Infarction does not develop or is greatly limited if the flow of blood is reestablished rapidly.Failure to reestablish blood-flow can lead to the loss of limb, angina pectoris, myocardialinfarction, stroke or even death.

Occlusion of the venous circulation by thrombi leads to blood stasis which can causenumerous problems. The majority of pulmonary embolisms are caused by emboli that originatein the peripheral venous system. Reestablishing blood flow and removal of the thrombus ishighly desirable.

There are many existing techniques employed to reestablish blood flow in an occludedvessel. One common surgical technique, an embolectomy, involves incising a blood vessel andintroducing a balloon-tipped device (such as the Fogarty catheter) to the location of theocclusion. The balloon is then inflated at a point beyond the clot and used to translate theobstructing material back to the point of incision. The obstructing material is then removed bythe surgeon. While such surgical techniques have been useful, exposing a patient to surgery maybe traumatic and best avoided when possible. Additionally, the use of a Fogarty catheter isproblematic because of the great risk of damaging the interior lining of the vessel as the catheteris being withdrawn. -1- WO 97/27808 PCT/US97/01807

Percutaneous methods are also utilized for reestablishing blood flow. A commonpercutaneous technique is referred to as balloon angioplasty where a balloon-tipped catheter isintroduced to a blood vessel, typically through an introducing catheter. The balloon-tippedcatheter is then advanced to the point of the occlusion and inflated in order to dilate the stenosis.Balloon angioplasty is appropriate for treating vessel stenosis but is not effective for treatingacute thromboembolisms.

Another percutaneous technique is to place a microcatheter near the clot and infusestreptokinase, urokinase or other thrombolytic agents to dissolve the clot. Unfortunately,thrombolysis typically takes hours to days to be successful. Additionally, thrombolytic agentscan cause severe hemorrhage and in many patients the agents cannot be used at all. U.S. Patent Nos. 4,706,671 and 5,011,488 both describe the use of a coiled section for theremoval of thromboembolic material. However, neither patent describes a device that ismarketed. U.S. Patent No. 4,706,671 teaches the use of a hollow flexible elastomeric materialto form the shape of the coiled section. The coiled section is hollow to allow for the insertionof a liquid into the hollow center such that the coils become stiff. U.S. Patent No. 5,011,488teaches the use of a coiled section that is fixed on both the proximal and distal ends such that theoperator of the device can change the shape and size of the coils. However, this device may beimpossible to manufacture and is impossible to use in small vessels.

Another problematic area is the removal of foreign bodies. Foreign bodies introduced intothe circulation can be fragments of catheters, pace-maker electrodes, guide wires, anderroneously placed embolic material such as thrombogenic coils. The only available retrievaldevices for the removal of foreign bodies are devices which form a loop that can ensnare theforeign material by decreasing the size of the diameter of the loop around the foreign body. Theuse of such removal devices is difficult and sometimes unsuccessful.

Thus, there exists a need for the development of a device that can be easily deployed intothe circulatory system for the removal of viscoelastic clots and foreign bodies. There is also aneed for a device which could be used as a temporary arterial or venous filter to capture andremove thromboemboli formed during endovascular procedures. -2- !' ' O’ k-/ WO 97/27808 PCT/US97/01807

Summary of the Invention

The present invention is a coil type device that is useful in removing clots and foreign 5 bodies in vessels. The invention comprises a catheter with at least one lumen. Located withinthe catheter is a clot capture coil that is connected to an insertion mandril. The clot capture coilis made out of a solid elastic or superelastic material which has shape memory. The elasticityor superelasticity of the coil allows it to be deformed within the catheter and to then reform itsoriginal coil configuration when the coil is moved outside of the catheter lumen. 10 In an alternate embodiment, the coil is made out of a biphasic material which changes shape upon heating or the passage of electrical current. The coil is straight initially, and thenafter passing electrical current or heat the coil changes to its coil configuration.

Once the coil configuration has been established, the coil can be used to ensnare andcorkscrew a clot in a vessel. The clot is extracted from the vessel by moving the clot capture coil 15 and catheter proximally until the clot can be removed or released into a different vessel that does not perfuse a critical organ. The coil can also be used a temporary arterial or venous filter tocapture and remove thromboemboli formed during endovascular procedures. Foreign bodies arecaptured by deploying the coil distal to the foreign body and moving the clot capture coilproximally until the foreign body is trapped within the coil. By removing the device from the 20 body, the foreign material is also removed. 25 30 35 -3- WO 97/27808 PCT/US97/01807 10 15 20 25 30 35

Brief Description of the Drawings

Embodiments of the invention will now be described with reference to the following drawings which: FIG. la is a schematic illustration of an occluded artery with a microcatheter and the clot capture coil of the present invention; FIG. lb is a schematic illustration of an occluded artery with a microcatheter and a clotcapture coil inserted through an occlusion; FIG. lc is a schematic illustration of the deployment of the clot capture coil within anoccluded artery; FIG. Id is a schematic illustration of the clot capture coil of the present inventionencountering a clot in an occluded artery; FIG. le is a schematic illustration of the clot capture coil ensnaring the clot in an occluded artery; FIG. If is a schematic illustration of the clot of FIG. le being moved within an occludedartery via the clot capture coil; FIG. lg is a cross section of the artery and the catheter of FIG. le along line lg-lg. FIG. 2a is a schematic illustration of an occluded artery and an alternate embodiment of the clot capture coil; FIG. 2b is a schematic illustration of a microcatheter passed through a clot within anoccluded artery and the extended coil of the clot capture coil within the catheter ; FIG. 2c is a schematic illustration of the deployment of the clot capture coil in anoccluded artery; FIG. 2d is a schematic illustration of a clot capture coil ensnaring a clot within anoccluded artery; FIG. 2e is a schematic illustration of the removal of a clot via a clot capture coilillustrating the corkscrewing and ensnaring effect of the coil within the viscoelastic clot; FIG. 2f is a cross section of the artery and catheter of FIG. 2d at line 2f-2f. FIG. 3 is an alternate coil configuration; FIG. 4 is an alternate coil configuration; FIG. 5 is a further coil configuration; FIG. 6 is an additional coil configuration; FIG. 7 is a further coil configuration; FIG. 8 is a double helix coil configuration and a single lumen catheter; FIG. 9 is a double helix coil configuration and a double lumen catheter; FIG. 10a is a schematic illustration of the clot capture coil and an introducer; FIG. 10b is a schematic illustration of a clot capture coil straightened within the inner -4- WO 97/27808 PCT/US97/01807 10 lumen of the introducer of FIG. 10a; FIG. 11 is a plan view of the present invention being deployed within an introducingcatheter with a side suction port; FIG. 12 is a schematic view of the present invention being deployed within an introducingcatheter such that the coil section is within the inferior vena cava of a patient; FIG. 13 is an alternate coil configuration that is particularly useful for removing clots ina surgically created arteriovenous fistula of a hemodialysis patient; FIG. 14 is a further coil configuration; andFIG. 15 is another coil configuration. 15 20 25 30 35 -5- WO 97/27808 PCT/US97/01807 10 15 20 25 30

Description of the Preferred Embodiments

Turning now to FIGS, la-lg, a clot capture coil device 10, is generally illustrated withinan artery 20 with a clot 22. The device comprises a catheter 12 with at least one lumen 14, a clotcapture coil 18, and an insertion mandril 16.

The catheter 12 can be any commercially available catheter that is made out of anyappropriate biologically compatible material. Typically, the catheter will have a single lumen14 and is constructed out of a flexible elastomeric materials such as silicone, rubber,polyvinylchloride, polyurethanes, polyesters, polytetrafluoroethylene, and the like. The catheterhas to be flexible enough and long enough to navigate through blood vessels to the occludedvessel 20 where clot 22 is located. Typically the catheter will range in length from about 20 toabout 175 cm.

The outer diameter of the catheter can also vary. Typically the outer diameter will rangefrom about 2 to about 10 French (one French = 0.013 inch). The inner diameter will range fromabout 1 to about 9 French.

The insertion mandril 16 has to be relatively stiff to support the coil 18. In the preferredembodiment, the insertion mandril is made out of stainless steel and is a solid wire of from about0.006 to about 0.038 inches in diameter. Other materials could be used such as a hard plastic,nitinol, and the like to make the insertion mandril. The insertion mandril is 10 to 20 cm longerthan the catheter such that the operator of the device (typically a physician) can control theinsertion mandril by gripping the proximal end which extends from the proximal end of thecatheter.

Connected to the insertion mandril is the clot capture coil 18. In one embodiment, the coilis made from a flexible solid elastic or superelastic material which has shape memory, i.e., it candeform to a straighten position and then return to a resting coil configuration. In a preferredembodiment, the coil is made out of a solid nitinol wire with a diameter of about 0.001 to about0.038 inches. The use of nitinol in medical devices is well known in the art. Nitinol is preferredbecause of its superelasticity and its shape memory. However, other solid materials that are alsoelastic or superelastic and have shape memory could also be used such as some synthetic plastics,metallic alloys, and the like. To make the coil, the nitinol wire is wrapped around a mandrel intothe coil configuration. The nitinol is then heated to an appropriate temperature such that thenitinol wire adopts the coil configuration as its resting shape upon cooling. The diameter of thecoils can vary depending on the size of the vessel occluded. The diameter can range from about1 mm for small vessels to about 30 mm for large vessels such as the pulmonary arteries orinferior vena cava. The length of the coil can also vary but typically ranges from about 3 toabout 100 mm in the proximal to distal direction. Because the nitinol coil is superelastic, the coilcan be extended to a completely straight configuration with the use of minimal force and then 35 -6- WO 97/27808 PCT/US97/01807 k· 10 15 20 25 30 reform to its natural resting configuration when the force is removed. In use, the coil is extendedby using the insertion mandril to insert the coil and the mandril into the narrow lumen of thecatheter.

In an other embodiment, the coil is made out of a solid biphasic material which changesshape upon heating or the passage of electric current. A presently preferred material is biphasicnitinol which has a straight configuration initially, and changes to a coiled configuration uponthe passage of electric current or heating. The use of biphasic nitinol is well known in themedical arts for other purposes. The biphasic nitinol coil would be made using ordinary skill inthe art such that the nitinol coil is straight initially and then forms the appropriate coilconfiguration. As would be apparent to a person skilled in the art, the biphasic coil could alsobe constructed such that the initial coil configuration is the normal shape and that the biphasiccoil straightens upon passing electric current or heating. The coil dimensions would be similarto the dimension detailed above for the shape memory coil.

The coil section of either the shape memory coil or the biphasic coil can have manydifferent configurations. Similar reference numerals are used throughout the figures to indicatedsimilar components of the embodiments. In the embodiment illustrated in FIGS, la-If, the coilis barrel shaped such that the diameter of the coils are relatively small at the distal and proximalends of the coil and is relatively large in the center of the coil. In a typical coil configuration,the diameters of the coils range from 2 mm at the proximal and distal ends and expand to 10 mmin the center. However, other sizes are also useful depending on the relative size of the occludedvessel. At the proximal end of the coil is a small circular loop 26. In the preferred illustratedembodiment, the circular loop is placed around the stainless steel wire and is freely slidable overthe wire. The distal end of the barrel shaped coil is permanently connected to the distal end 24of the insertion mandril. Thus, in this embodiment the coil extends proximally from the distalend of the insertion mandrel. In the preferred embodiment the coil is welded onto the distal endof the insertion mandril. Other means of permanently connecting the coil could also be usedsuch as crimping the coil, gluing the coil, screwing the coil into a screw type mount, and the like. A different coil configuration is illustrated in FIGS. 2a-2f. In this embodiment, the coil30 is connected at its proximal end to the distal end 24 of the insertion mandril 16. Thus, the coilextends distally from the distal end of the insertion mandril. The distal end 32 of the coil is freefloating. The coil is conically shaped with the diameter of the coils decreasing distally to the freeend 32. Embodiments where the coil is connected to the proximal end are preferred for use inremoving clots from small and/or tortuous vessels as will be discussed below.

The size and shape of the coils can vary and different representative embodiments areillustrated in the different figures. FIG. 3 illustrates an alternate embodiment where the coil 34is attached at its proximal end to the distal end of the insertion mandril 16. Thus, the coil extends 35 -7- WO 97/27808 PCT/US97/01807 10 15 20 25 30 distally away from the distal end of the insertion mandril. The coil is shaped like an invertedcone with the diameter of the coils increasing distally. This embodiment is particularly usefulfor retrieving clots from small (1-2 mm diameter) vessels in the cerebral and coronarycirculations. The diameter of the coils in this configuration are typically from about 1 mm toabout 3 mm, could be larger depending on the relative size of the occluded vessel. FIG. 4 illustrates a cone shaped coil 36 where the distal end of the coil is connected to thedistal end of the insertion mandril. FIG. 5 is a similar embodiment to FIG. 4 except that the coil38 is wound tighter such that there are more revolutions per inch. In both FIGS. 4 and 5 the coilsection extends proximally from the distal end of the insertion mandril. FIG. 6 illustrates a different embodiment where the proximal end of the coil 42 isconnected to the insertion mandril's distal end. The coil is shaped like an inverted cup which hasa constant diameter until the coil reaches its most distal end where the diameter decreases. FIG. 7 is a similar embodiment to FIGS, la-lf except that the barrel shaped coil 40 isconnected to the distal end of the insertion mandril such that the coil extends distally instead ofproximally.

The embodiment of FIG. 8 is a double helix coil configuration that is useful for large clotremoval. The configuration is such that one continuous piece of wire is used to form the doublehelix configuration. Both ends of the coil 44 and 46 are connected to the distal end of theinsertion mandril 16. In the preferred embodiment, both ends are welded onto the insertionmandrel 16 at weld lines 45 and 47. The coil has been heat treated such that it forms a restingdouble helix shape. The two helixes 48 and 50 intertwine and are connected at the top of eachhelix at point 52. When the double helix coil is withdrawn into the single lumen catheter bytranslating the insertion mandril, the helixes straighten until the coils are completely withdrawninto the catheter's lumen. By translating the insertion member in the opposite direction, the coilis forced out of the lumen of the catheter and then reforms the double helix configuration. FIG. 9 is an alternate double helix embodiment where the double helix is used inconjunction with a double lumen catheter 56. The lumens 58 and 60 each receive an insertionmandril 16 and 16'. Each insertion mandril in turn is permanently connected to one of the endsof the coil. At the proximal end of the insertion mandrills are optional connecting bars 17 whichkeep the relative spacial relationship of each insertion mandril constant. In this embodiment, asthe helixes are withdrawn into the catheter, each one straightens out and is kept separate withinthe respective lumens. When the helixes are then deployed by translating the insertion mandril,the helixes reform the double helix configuration. The optional connecting bars 17 are used toensure that each helix is being deployed by the translation of the insertion mandrils are in unisonwith each other such that the double helix configuration is always obtained upon fulldeployment. 35 -8- WO 97/27808

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PCT/US97/01807 FIG. 13 illustrates a long coil 140, ranging from about 2 cm to about 10 cm that isespecially useful for removing clots in a surgically created arteriovenous fistula of a 5 hemodialysis patient. The coil could also be used for removing long clots in the venous systemand long clots in a surgically created by-pass graft. The arteriovenous fistulas are normally F surgically created on the forearm of a hemodialysis patient and allows for easy access to theblood stream for hemodialysis treatment. Unfortunately, these fistulas often become cloggedwith long blood clots and have to be surgically repaired or a new fistula created. The long clot 10 capture coil 140 is connected to the insertion mandril 16 at the coil's proximal end. FIGS. 14 and 15 illustrate two further coil configurations. FIG. 14 is a cylindrical coil 150 attached to the distal end of the insertion mandril 16. FIG. 15 is a random tangle coilattached to the insertion mandril 16. The random tangle is manufactured by extruding the coilmaterial in a random fashion. The random tangles made by such a process would vary each time 15 the tangles are manufactured, and thus, the random tangle pictured in FIG. 15 is for illustrationonly. FIGS. 10a and 10b illustrate the use of an introducer 72 with lumen 74. The introduceris a relatively short (10 to 20 mm long) single lumen catheter that is used to straighten the coilsection of a shape memory coil which extends distally, such as the coils in FIGS. 2,3,6, and 7, 20 prior to insertion into the catheter 12 of the present invention. A longer introducer would beused for the arteriovenous fistula coil of FIG. 13. The insertion mandril is inserted into theintroducer in a retrograde direction (indicated by the arrow in FIG. 10a). Once the introducerreaches the shape memory coil section, the coil section straightens out almost to a completestraight line. In coil section that extend distally outward, the inner diameter of the introducer and 25 the catheter are sized to be just slightly larger than the diameter of the insertion mandril and the coil section. That is, if the insertion mandril and the coil are each made from 0.008 inchdiameter wires, then the inner diameter of the introducer is preferably 1 to 2 French. Once thecoil has been straightened out completely, the coil within the introducer is aligned with thecatheter and then advanced in an anterograde direction into the catheter. 30 The above detailed description describes some of the numerous embodiments of the present invention. Below is a discussion of some of the numerous uses of the invention.

In use, a patient presenting with symptoms of a thromboembolic disorder is examinedradiographically using angiography to locate an occlusion and to confirm the diagnosis. A largeintroducing catheter 130 (see FIG. 12) is then inserted into an appropriate vessel (usually the 35 femoral artery or the femoral vein). A small catheter or microcatheter 12 is then introduced into the vessel via the introducing catheter and advanced using a guide wire or the like into the occluded vessel. The catheter 12 is then passed through the viscoelastic clot. Once the catheter is in place and through the viscoelastic clot the clot capture coil is introduced into the catheter -9- WO 97/27808 PCT/US97/01807 using the insertion mandril and advanced to the distal tip of the catheter. For the shape memoryclot capture coils that extend proximally from the insertion mandril (as in FIGS, la-If, the coiland the insertion mandril are inserted directly into the proximal end of the catheter and advancedto the distal end (see FIG. lb). For the shape memory clot capture coils that extend distally fromthe insertion mandril (as in FIGS. 2a-2e), the introducer of FIGS. 10a and 10b is used asdescribed above. For the biphasic coils, the coils are introduced in the straight configuration byeither having the straight configuration the natural configuration or by straightening a naturalcoil configuration by passing electric current or heating the coil.

Once the catheter and the clot capture coil have transversed the clot, the insertion mandrilis translated distally relative to the catheter. With a shape memory coil, the coil deploys andreform its natural configuration outside the distal end of the catheter. By comparing FIGS, lcand 2c it is apparent that the shape memory coils which extend distally from the insertionmandril immediately start to form the coil configuration once part of the coil is freed from theconfines of the lumen of the catheter. These embodiments are particularly useful for clotremoval in vessels that are small and/or tortuous where there is not much room for theadvancement of the insertion mandril and the coil. In the embodiments where the shape memorycoil extends proximally from the distal end of the insertion mandril, the entire length of the coilneeds to be freed from the confines of the lumen of the catheter before it reforms the coilconfiguration. These embodiments are useful for the removal of large clots in large vesselsbecause the coil is better supported and the coils can collapse upon each other. For example,as illustrated in FIGS, lc-lf the proximal end of the coil which is a slidable loop 26 mountedaround the insertion mandril will encounter the clot material first. The slidable loop then slidesdistally until the coils form a double inverted cone shaped configuration. The coils will overlapand thus give more support for the removal of large clots.

The biphasic coils are deployed similarly except that electric current or heat is used toform the coil configurations if the straight configuration is the natural shape. If the coilconfiguration is the natural shape, then the user stops applying electric current or heat and thecoil configuration will reform.

The clot is then retrieved by translating the insertion mandril along with the catheterproximally. When the clot capture coil is pulled proximally the clot becomes ensnared.Additionally, while pulling proximally on the insertion mandril, the coil is rotated by rotatingthe insertion mandril to transfix the clot by corkscrewing the clot into the coils. The viscoelasticproperties of the clot allow the clot to be captured within the side coils and to be pulled downusing the most distal coils as a capture cup. The clot can then be completely removed or releasedinto a vessel that does not perfuse a critical organ such as an external carotid artery. A particularly useful introducing catheter is illustrated in FIG. 11. The introducing -10- WO 97/27808 PCT/US97/01807 catheter 110 is hollow with a single lumen and has a Y junction towards its proximal end. The introducing catheter is a standard commercially available introducing catheter. The introducing5 catheter has two ports, 112 and 114. Port 112 is in straight communication with the longitudinalaxis of the introducing catheter and is useful for the insertion of the catheter 12, coil 30 and

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insertion mandril 16 of the present invention. The other port which is angled away form the longitudinal axis of the insertion catheter is for the attachment to a suction line from a vacuumsource. Located at the distal end 116 of the introducing catheter is a marker band 118 that can 10 be located via radiographic means while the introducing catheter is being used.

In practice, the introducing catheter 110 is inserted through a large vessel and through thevascular system to a position near a clot in an occluded artery under fluoroscopic guidance. Thecatheter 12, is then inserted through port 112 and through the introducing catheter such that thedistal end of the catheter 12 has passed the distal end 116 of the introducing catheter. The 15 catheter 12 is then translated across the clot. The coil 30 and insertion mandril 16 are theninserted into the catheter 12. The insertion mandril is then translated through the catheter 12until the coil 30 is deployed in the vessel. The insertion mandril is then translated proximallyto ensnare the clot within the coil and then the catheter, coil and clot are translated toward thedistal end 116 of the introducing catheter 110. Once the clot and the coil are at the distal end 20 116, suction is applied via port 114 to suck part of the clot into the distal end 116. The suction helps to keep the clot within the coil. Then the introducing catheter 110, the catheter 12, the clotand the coil 30 are removed from the patient. FIG. 12 illustrates the invention being used as a filter in the inferior vena cava of a patientwith a venous thrombus in a lower limb. A commercially available introducing catheter 130 is 25 advanced into a femoral vein 122 and into the inferior vena cava 128 below the heart 126. Acatheter 12 is then advanced through the introducing catheter. The coil 120 and insertionmandril 16 are then advanced through the catheter 12 and the coil 120 is deployed within theinferior vena cava. The coil 120 has a large diameter, around 20 mm to 30 mm, such that whendeployed it fits snugly within the inferior vena cava. The coil acts as a filter wherein pieces of 30 the thrombus become trapped in the coil instead of being transported to the lungs. Thethrombicmaterial can then be removed from the patient.

Foreign bodies are removed as described above except that the foreign body becomesensnared in the clot capture coil instead of a clot. Due to the numerous coils, it is much easierto ensnare a foreign body than using a loop type device. 35 The following examples illustrate some of the uses of the invention. The examples are provided for illustration purposes and are not meant to limit the invention to the specific examples. -11- WO 97/27808 PCT/US97/01807 10 15 20 25 30 35 EXAMPLE 1

The clot capture coil was clinically tested in pigs. In the first study a pig's femoral arterywas isolated and a large commercially available introducing catheter was inserted into thefemoral artery. Arterial blood was then withdrawn and allowed to clot in vitro.

An arterial catheter was then inserted through the introducing catheter and into the carotidartery. The coagulated arterial blood was then released into the carotid artery branches via thearterial catheter resulting in the formation of numerous emboli.

Angiography was used to locate the emboli. While preforming angiography amicrocatheter (outer diameter of 3 French and inner diameter of 1 French) was inserted into anoccluded carotid artery using a guide wire for placement and standard microcatheter placementtechniques. The microcatheter was advanced distally past the clot. The guide wire was thenwithdrawn from the microcatheter. A shape memory clot capture coil connected to an insertion mandril was then introducedinto the microcatheter using a small introducer. The coil configuration was the type illustratedin FIG. 2a. Because the coil extends distally from the insertion mandril a small introducingcatheter had to be used to introduce the clot capture coil into the microcatheter. The insertionmandril and the clot capture coil was inserted in a retrograde direction into the introducingcatheter. The inner diameter of the introducing catheter was identical to the microcatheter. Theclot capture coil became straight due to the superelastic properties of the coil and the small innerdiameter of the introducer. Once the coil was completely within the introducer, the introducerwas aligned with the microcatheter and the coil was inserted into the microcatheter in ananterograde direction.

The clot capture coil was slowly advanced to the distal end of the microcatheter bytranslating the insertion mandril. As the insertion mandril was advanced, the coil began to beexpressed from the distal end of the microcatheter. As more and more of the coil was expressed,the coil deployed and returned to its natural resting coiled shape as in FIG. 2c.

The clot capture coil was then pulled proximally to ensnare the clot. While pullingproximally, the coil was rotated by rotating the insertion mandril to transfix the clot bycorkscrewing the clot into the coils. The clot was then completely removed from the pig byremoving the microcatheter, insertion mandril, and the clot within the clot capture coil from thepig's femoral artery. EXAMPLE 2

The procedure of example 1 was repeated using a shape memory clot capture coilconfiguration illustrated in FIG. 3. The clot was successfully corkscrewed and ensnared andremoved from the pig's occluded cerebral artery. -12- u WO 97/27808 PCT/US97/01807 EXAMPLE 3

The procedure of example 1 was repeated using a shape memory clot capture coil as5 illustrated in FIG. 4. Because this embodiment has the coil extending proximally from the distal_ end of the insertion mandril, the clot capture coil was directly inserted into the microcatheter F without the use of a small introducer. A clot in an occluded carotid artery was ensnared in the coil and completely removed.

Thus, a clot capture coil is disclosed which allows for the removal of thromboembolic10 material and foreign bodies from a blood vessel. While embodiments and applications of thisinvention have been shown and described, it would be apparent to those skilled in the art thatmany more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims. 15 20 25 30 35 -13-