Patent ID: 12232750

DETAILED DESCRIPTION

A catheter system10may be introduced for example into a patient suffering from an ischemic stroke in order to restore blood flow to an occluded area of a cerebral blood vessel. Generally, the catheter system10, as shown inFIG.1, consists of a single barrel arrangement (FIG.1a) having a tubular member13or a double barrel arrangement (FIG.1b) of tubular members13and14. In one embodiment, the catheter system10includes an outer catheter12, a bypass microcatheter23, at least one flow-arresting balloon24a, and a guidewire11. In another embodiment the catheter system10includes an outer catheter12, a first bypass microcatheter23, a second bypass microcatheter25, two inflatable flow-arresting balloons24aand24b, and at least one guidewire11a(shown inFIGS.1band2). The catheter system10may be introduced into a vessel of a patient via an extracranial guide catheter (ECGC)5having a proximal end4, a distal end3, a single lumen8, an inflation lumen7disposed marginally and at least a single flow-arresting balloon6capable of arresting forward flow of blood in the extracranial carotid or vertebral or other source artery.

The outer catheter12is generally tubular in shape and includes a first tubular barrel13, a second tubular barrel14, a proximal end21, a transition portion (not shown), and a distal end22. The first tubular barrel13and the second tubular barrel14may be formed integrally with, or affixed separately to, the outer catheter12. Each of tubular barrel13and14include proximal open ends16and17and distal open ends19and20, respectively. The outer catheter12may also include at least one inflatable flow-arresting balloon24adisposed on its proximal end21, and at least one perforation18on the sidewall of the proximal end21. Preferably, the sidewall portion of the proximal end21of outer catheter12may include plurality of perforations to form a substantially ‘perforated segment region45that may cover the proximal end21and/or distal end22and/or transition portions (FIG.2). Radiographic markers46aand46bmay be disposed on either side of the perforated segment45of the outer catheter12(shown inFIGS.2and5).

Similar to the outer catheter12, as shown inFIG.1, the first bypass microcatheter23and second bypass microcatheter25may also include generally tubular bodies having proximal ends26and27, respectively, transition portions (not shown), and distal ends28and29, respectively. The outer catheter12, first bypass microcatheter23and the second bypass catheter25each may include at least one lumen15,13′ and14′ therein extending from the distal ends22,28, and29of the tubular bodies to the proximal ends21,26, and27of the tubular bodies (shown inFIG.1b). However, only the lumen13′ and14′ of the first and second bypass microcatheters have open ends at both the proximal ends26and27and the distal ends28and29, while the lumen15of the outer catheter12is open only at the proximal end21and may be closed at its distal end22.

The first bypass catheter23and second bypass catheter25disposed within the first barrel13and the second barrel14of the outer catheter12are movable, rotatable in a clockwise/counterclockwise direction, or slidable in a forward/backward direction within the outer catheter112along a horizontal axis A. An inflation lumen7may be disposed marginally on at least the outer catheter12or one or both of the bypass microcatheters23and25respectively (shown inFIGS.1d-g). The inflation lumen when filled with standard inflation fluid, such as saline or sterile water, may help to inflate one or more balloons present on the proximal portion of the outer catheter12. To aid in the visualization of the first bypass microcatheter23and second bypass microcatheter25as they are navigated into the main vessel lumen30, or within the lumen of the distal branches31(M1) and32(M2) (shown inFIG.4), radiopaque markers36a,36bmay be disposed on the distal portion of the first bypass microcatheter23and second bypass microcatheter25respectively (shown inFIG.7).

For intracranial applications, such as an acute stroke, the outer catheter12may be made of flexible materials, including but not limited to, hypoallergenic silicone rubber, nitinol, nylon, polyurethane, polyethylene terephthalate (PETE), polyvinyl chloride (PVC), latex, titanium, stainless steel or thermoplastic elastomers or combinations thereof. Other suitable materials are also contemplated. The first bypass microcatheter23and the second bypass microcatheter25may be made of the same material as the outer catheter12or can be made from different material. The outer catheter12and the first bypass microcatheter23and second bypass microcatheter25may all have a hydrophilic surface coating. The first bypass microcatheter23and second bypass microcatheter25may have a length from about 150 cm to about 300 cm and may have an external diameter from about 0.62 mm to about 0.95 mm. In general, the internal diameter of outer catheter12is larger than the external diameter of first bypass microcatheter23and second bypass microcatheter25. Ideally, the outer catheter12may have an internal diameter from about 0.10 mm to about 0.50 mm larger than the external diameter of the first and second bypass microcatheters23and25respectively.

The outer catheter12, the first bypass microcatheter23, and second bypass microcatheter25may all be color-coded or numerically coded to form a matching system. All catheters that can be used together should be similarly coded to avoid any mismatch.

The catheter system10may also include one or more guidewires (shown inFIGS.1-3). The primary guidewire11may be coated with a hydrophilic substance and may be used for initial placement of the catheter system10. The primary guidewire11may have a length from about 180 cm to about 190 cm. A second and a third guidewire11aand11b, shown inFIGS.6,7and11-13, may also be used for navigating the first bypass microcatheter23or the second bypass microcatheter25and may be similarly constructed and have a length of about 300 cm.

As shown inFIG.1g, the catheter system10may be introduced into a patient's body by inserting a bi-lumen sheath (not shown) into the patient's femoral artery. The sheath may also include an extra channel for withdrawing arterialized blood. The catheter system10, including the outer catheter12, a bypass microcatheter23may then be, in the case of a stroke patient, navigated through the first lumen of the sheath into the femoral artery, up and around the arch of the aorta, into the carotid or vertebral artery, to the skull base, and deployed at the site of the arterial occlusion in the cerebral arteries. An intermediate guide catheter (ECGC)5that remains extracranial may also be deployed into the extracranial vertebral or carotid artery, serving then as the unmoving guide for the device, which then passes intracranially. The ECGC may be anchored in position by inflating the balloon6which may additionally serve to arrest blood flow in the vessel. A guidewire11may then be used to deploy the bypass microcatheter23which may then be extended through and beyond the occlusion as shown inFIG.6a. Subsequently the physician may inflate a single balloon as shown inFIG.6aor two balloons as shown inFIG.6b, or a single balloon with a dumbbell shape, to arrest any trickling blood flow in the vessel beyond the flow arresting balloon6on the ECGC and proximal to occlusion. This flow arresting step may be performed prior to initiating the bypass mechanism and/or thrombolysis treatment.

It should be noted that while the outer catheter12and first bypass microcatheter23and second bypass microcatheter25are navigated through the body and positioned at the site of the occlusion as shown inFIG.6b, pressurized (at approximately 300 mm Hg) and/or heparinized saline may be pumped from the proximal end21into the central lumen15and out through the perforations18of the outer catheter12at the site of occlusion40. The heparinized saline may also be delivered beyond the occlusion40into distal branches M131and M232from the proximal ends26and27through lumen13′ and14′ of the first bypass microcatheter23and second bypass microcatheter25and out through the distal open ends28and29, respectively. The influx of the heparinized saline through the catheters12,23and25prevent blood and other potential debris, such as emboli, from entering and clogging the catheters. In one embodiment the first bypass microcatheter23and second bypass microcatheter25can be used to deliver other treatment solutions such as arterialized or oxygenated blood, thrombolytic agents, cold plasma, cooled plasma, saline, etc. Generally, the medicated treatment solution is selected from a solution of arterialized blood, cooled saline, thrombolytic agents, vasodilators, cooled plasma, or a combination thereof.

FIGS.6-8show the stroke catheter system10in successive positions in relation to an occlusion40lodged close to the junction of bifurcating branches in a main artery or vessel30.FIGS.6aand6bshow the outer catheter12positioned proximal to the occlusion40and guidewires11aand11bextended beyond the occlusion40and towards the distal branches M131and M232. The radiopaque markers36aand36bdisposed at the distal ends of the first bypass microcatheter23and the second bypass microcatheter25may further aid the physician to navigate both bypass microcatheters23and25towards the distal branches M131and M232(FIG.7). This maneuver around or through the occlusion40as shown inFIG.6is possible due to the distensible nature of the vasculature tissue wall. Further, inflation of the balloon24aand/or24ballows the physician to not only lock the outer catheter12in position, it importantly serves to arrest blood flow in the vessel proximal to the occlusion (FIG.8). Generally, the balloons6,24aand24b, when fully inflated, can be at least about 3 mm in diameter and about 5 mm in length and are designed to sufficiently prevent the movement of the ECGC5and/or outer catheter12within the vessel wall and arrest blood flow at the site of occlusion40. Design of the balloon may also be such as to enable inflation of two dumbbell ends separated by a more linear interposed section, through a single inflation channel. While all balloons are inflatable and capable of arresting forward flow of blood, the physician may choose to inflate only balloon, for example balloon6on the ECGC. In some instances the physician may opt to inflate two balloons,6and24aor24bor all the balloons disposed on the ECGC and outer catheter12to arrest forward flow of blood. Depending on the nature or fragility of the vessel wall the physician may also choose to inflate the balloons at different pressures in order to arrest blood flow.

Further, as shown inFIG.8, since both bypass microcatheters23and25are movable within the outer catheter12, the physician may choose to partially withdraw one of the bypass microcatheters. In doing so, the partially withdrawn bypass microcatheter can be positioned proximal to the occlusion40(as shown inFIG.8) and may be used to deliver a thrombolytic agent at the occlusion40in addition to delivering the same thrombolytic agent through the perforated segment45of the outer catheter12to initiate the thrombolysis of the occlusion40. Simultaneously, the other bypass microcatheter which is disposed within one of the distal branches M131or M232may be used to deliver arterialized blood, cooled plasma, or cold plasma to the portion of the brain (bypass mechanism) that has been deprived of oxygen due to the ischemic event thus restoring blood flow at least in one of the branches (FIG.8).

Delivery of arterialized blood beyond the offending occlusion not only restores the life of at least one of the oxygen starved branching vessel even before the occlusion is removed, it importantly increases the amount of time the physician has to disintegrate the occlusion and reestablish the normal blood flow to the patient's ischemic brain. For example, the time taken to restore blood flow in the region distal to the occlusion using the catheter system10may be within 15 minutes, and preferably within 8 and 10 minutes after the procedure is initiated. Alternatively, an injection of arterialized blood with heparinized pressurized saline may be administered through the bypass microcatheter that extends into one of the branching vessels (second bypass microcatheter25inFIG.8) by withdrawing the patient's own blood from the femoral artery into a syringe (not shown) and mixing the blood with heparinized saline.

After one of the bypass microcatheters is positioned to restore blood flow into one of the vessel branch M131, M232(as shown inFIG.8), the physician may begin the thrombolysis treatment by pumping a thrombolytic agent through the partially withdrawn bypass microcatheter that is positioned proximal to the offending occlusion40(as shown by first bypass microcatheter23inFIG.8). Delivery of thrombolytic agent at the occlusion may help to dissolve or disintegrate the occlusion40. In addition, negative pressure may be applied via the central lumen15of the outer catheter12. The pressure may be imparted by a negative-pressure pump or by the operator, using a syringe with a flow-limiting valve. The negative pressure generated will generally be less than the pressure required to collapse the walls of the involved blood vessel.

The negative pressure created in the central lumen15of the outer catheter can further help to aspirate the smaller clot debris via the perforations18of the outer catheter12. The applied pressure also helps the larger debris that cannot pass through the perforations18to stick to the surface of the outer catheter12. After the offending occlusion40is completely disintegrated, the delivery of the thrombolytic agent via the partially withdrawn bypass microcatheter23may be discontinued and the outer catheter12may be withdrawn with the clot debris adhered to its surface. Meanwhile, the second bypass microcatheter25, as shown inFIG.8, is allowed to deliver arterialized blood for an additional time of about 5 to 10 minutes before it may be removed.

Generally, both the first bypass microcatheter23and second bypass microcatheter25may extend up to 10 cm farther beyond the distal end of the outer catheter12in order to effectuate the bypass method and access the distal bifurcating branches of a vessel. In addition to the arterialized blood, thrombolytic agents, cold plasma, cooled plasma, and saline may be administered past the occlusion in the manner described above. The cold plasma or cooled plasma may be used to create regionalized hypothermia, extending the time the surgeon may have to effectively remove the obstructing clot.

Although in this embodiment the first bypass microcatheter23is shown to be partially withdrawn, and the second bypass microcatheter25is shown to deliver the arterialized blood to branch M232, it may be appreciated by one of ordinary skill in the art that the physician can choose to use either of the bypass microcatheters23and25as desired to deliver thrombolytic agent and arterialized blood. The physician may also choose to deliver medication directly to and within the thrombus by injecting it through the perforations now lodged within the occlusion.

In another embodiment, as shown inFIGS.9-12, an offending occlusion lodged in the main vessel30at a certain distance from the junction of the bifurcating branches may be treated by an occlusion trapping mechanism that is effectuated by two inflated balloons.

In this embodiment, the outer catheter12is first navigated through and beyond the occlusion40, as shown inFIG.11, using one or two guidewires11aand11buntil at least one of the balloons on the outer catheter12, for example, balloon24ainFIG.12, is positioned beyond the occlusion40, while the second balloon24bis positioned proximal to the occlusion40. The two balloons24aand24bare spaced on the outer catheter12in such a way that the distance between them is sufficient to arrest blood flow at the site of occlusion and trap occlusions that range in size from about 0.5 cm to about 3.0 cm in most cases of ischemia. The radiopaque markers46aand46bon either side of the perforated segment45on the outer catheter12(shown inFIG.5) and/or the markers35-aand35-bon the balloons may further help the physician to visualize this maneuver. Once the occlusion40is positioned between the two balloons24aand24b, the balloons24aand24bmay be inflated by delivering inflation fluid through an inflation lumen to create a segmental trap and/or a blood free zone. The inflated balloons24aand24bmay also help to lock the outer catheter12in place. Importantly, inflating the balloons24aand24bon the outer catheter12stops blood flow in the vessel proximal to the occlusion so that a medicated solution can be delivered through the perforated region45on the outer catheter12to initiate thrombolysis of the occlusion40within the segmented region. Concurrently, the bypass mechanism may be initiated by extending the first bypass microcatheter23and second bypass microcatheter25into the distal branches M131and M232of the main vessel30with the help of the radiopaque markers36aand36b. In doing so the physician may pump a therapeutic solution, such as arterialized blood, cooled plasma or cold plasma, through one or both of the bypass microcatheters23and25to restore blood flow in the regions of the brain beyond the occlusion40that is deprived of oxygen due to the ischemic event.

In this embodiment, the medicated solution includes, but not limited to, a thrombolytic agent or a platelet antagonist medication and may be delivered via the central lumen15and out through the perforated segment45of the outer catheter12. Because the occlusion40is segmentally trapped and free of blood, the local concentration of the medication is sufficient to disintegrate the occlusion40in much less time than is required for an occlusion40when it is not segmentally trapped because of the localization of the medication and absence of dilution or washout effect. Once the occlusion is sufficiently disintegrated, the delivery of the medicated solution via the central lumen15of the outer catheter12is discontinued and a negative pressure is applied. The pressure applied helps to aspirate the smaller clot debris through the lumen15and allows larger debris to adhere to the surface of the outer catheter12.

Because the bypass microcatheters23and25and the outer catheter12have separate and distinct lumina, the bypass microcatheters23and25may remain in place, while the outer catheter12is used to segmentally engage and remove at least a portion of the occlusion40. As shown inFIGS.8and12, once the catheter system10has been used to remove a portion of the occlusion40, the bypass microcatheters23and25may be used to impart localized fluid-mediated hypothermia by delivering a pressurized cooling solution beyond the occlusion40. The solution may generally include a heparinized pressurized saline and/or a blood/oxygenated compound that is delivered to produce localized regional hypothermia to the brain via the bloodstream. In this embodiment, the heparinized and pressurized saline component of the solution is cooled before it is introduced into the catheter system10, either by itself or in combination with the oxygen-carrying compound (usually blood). It is contemplated that any suitable method of cooling the solution may be used, such as by a thermostat-controlled refrigeration device outside of the patient's body.

As shown inFIGS.2,5,6-8, and10-12, the distal end22of the outer catheter12includes a diffusion portion or perforated segment45having multiple perforations18. The perforations18provide fluid communication from the lumen of the outer catheter12to the vessel wall30. It is also contemplated that the perforations18may extend beyond the distal end22of the outer catheter12and in some embodiments the perforations18may be absent in regions where the balloons are disposed.

The radiographic markers that are disposed on either side of the perforated segment45or on the balloons22and24and in the distal ends of the bypass microcatheters23and25may include radiopaque rings or embedded pellets, among other suitable markers. Although it would be helpful to know a priori the length of the actual occlusion, not knowing the length does not limit the use of the stroke catheter system10, as it can become known simultaneously with visualization of thrombosis using angiography.

Once the perforated segment45of the outer catheter12is positioned within the occlusion40, the negative pressure being applied to the lumen of the outer catheter12can be discontinued so that a medicated treatment solution can be introduced again directly to the remaining occlusion40through the perforated segment45of the outer catheter12. This system of localized, distributed administration of medication through the perforations18in the perforated segment45exposes a greater surface area of the target occlusion40to the medicated treatment solution, such as a thrombolytic agent, antiplatelet agent, or nitro-vasodilator (i.e. a nitric oxide-based medication). The localized delivery of thrombolytic agent, antiplatelet agent, or nitro-vasodilator through the perforated segment45will remove or reduce the size of the occlusion40by dissolution thereof in the case of the 2 former, or by increasing the size of the lumen of the occluded vessel30in the case of the latter, to improve blood flow there through.

In the case of administration of nitric oxide-based vasodilator, the effect is one of distributing vasodilator medication to a segment of occluded vessel, allowing localized vasodilation and helping to liberate the vessel wall from the occlusive thrombus by allowing it to expand away from the latter.

The perforated segment45may also be used to deliver intralesional medication, especially thrombolytic medication for dissolving the lesion, and/or vasodilator medication for increasing the width of the vessel42at the site of obstruction. The perforated segment45also may be used to deliver medication, such as antiplatelet (2B3A glycoprotein receptor blocker) or vasodilator medication, to a chosen segment of a blood vessel.

It is also contemplated that the catheter system100having a single bypass microcatheter can be tapered only at the distal end122as shown inFIG.13aor can have a gradually tapering distal end as shown inFIG.13b. In this embodiment, the outer catheter120has a single lumen150as shown inFIG.13ato accommodate a bypass microcatheter130. The bypass microcatheter130in this embodiment may be formed integrally with, or affixed separately to, the distal end of the distal portion122of the outer catheter120. In some embodiments the distal end of the outer catheter12and/or bypass microcatheter130may include plurality of serrated teeth150that may help the physician to mechanically engage the occlusion40and break it up into smaller pieces (FIGS.13aandb). In this embodiment, the bypass microcatheter130is affixed separately to the outer catheter12so that a rotational and/or clockwise or counter clockwise movement of the bypass microcatheter130will help a physician to mechanically cut through the occlusion40. The serrated teeth may have a length of between 1.0 mm and about 4.0 mm and may also be retractable.

When the distal portion122of the outer catheter120is gradually tapered, the inner diameter of the distal end of the outer catheter120is only slightly larger than the outer diameter of the bypass catheter130. Tapering the distal portion122of the outer catheter prevents fluid from exiting the distal end of the outer catheter120, directing the flow of a medicament through the perforations118.

In another embodiment, the single lumen of the outer catheter200may have a diameter that is large enough to accommodate at least two bypass microcatheters230and240(FIG.14). Other variations of the outer catheter as shown inFIG.14are also contemplated.

In addition, it is contemplated that the catheter system10may be used for both intracranial and peripheral (limb, ischemic bowel, organ ischemia) situations characterized by vascular insufficiency. One such embodiment may be used to treat cardiac ischemia, by insertion into a coronary artery and utilizing endovascular bypass, clot removal and localized medication delivery functions of the system. It may also be used in venous vasculature, for situations of venous obstruction or insufficiency.

Prophetic Example

A patient, a 62 year-old male, with recently diagnosed atrial fibrillation, presents to the emergency department with left-sided paralysis and slurred speech of two hours' duration.

Examination demonstrates an alert cooperative patient unable to move his left side. Cardiac rhythm is atrial fibrillation. Speech is coherent and dysarthric, with left facial droop. CTA demonstrates a right middle cerebral artery occlusion. Intravenous thrombolysis is initiated and a surgical team mobilized for neurointerventional treatment.

The patient is taken to the Interventional Neuroradiology O.R. and placed under general endotracheal anesthesia after informed consent is obtained. He is placed in a supine position on the operating table and scalp and limb electrodes are rapidly placed for intraoperative brain wave potential monitoring. The Micropuncture Seldinger technique is used for placement of the arterial sheath in the right femoral artery. The sheath is equipped with a side port that is in continuity with the lumen of the femoral artery, separate from the sheath aperture that transmits the guiding catheter. This port is utilized to provide arterial blood from the femoral artery for the bypass microcatheter. Interposed between the port and the proximal end of the bypass microcatheter is a means for diluting the femoral arterial blood with heparinized saline, and a means for cooling the arterialized blood in order to effect selective specific hypothermia, if desired.

An extracranial guide catheter of appropriate caliber (e.g., 6 Fr) is navigated over a hydrophilic guidewire (e.g., 0.035) through the femoral arterial sheath and through the descending aorta, thence over the aortic arch. The guide catheter is flushed while in the descending aorta in order to remove any residual air or thrombus before engaging the cerebral vasculature. The guide catheter is then positioned in the right common carotid artery; a roadmap image is then used to selectively deliver it into the Right internal carotid artery. Flow patency is checked and cerebral arterial injection is then performed using the 6 Fr catheter in two planes of view, which demonstrates and confirms the embolic occlusion of the right middle cerebral artery. The occlusion is located at the bifurcation of the vessel.

A catheter system as described above is then deployed into the occluded right middle cerebral artery through the guiding catheter, which is already in position. The system is navigated to the proximal side of the occlusion, which can be clearly visualized on an angiogram, as shown inFIG.15. (FIG.15showing occlusion of the main barrel of the Right middle cerebral artery including the bifurcation).

An inner bypass catheter, slidably disposed within an outer catheter is then guided over the microguidewire into one of the occluded bifurcation branches, using fluoroscopy. The microguidewire is removed and microangiography is then performed through the microcatheter demonstrating the normal angiographic anatomy of that branch of the right middle cerebral artery. This microangiogram demonstrates that the bypass catheter is beyond the site of occlusion. The bypass catheter can now be used to deliver arterialized blood from the femoral artery of the patient, with or without dilution and cooling, or cooled saline alone, to the ischemic brain tissue distal to the occlusion.

Because the bifurcation of the middle cerebral artery is occluded, a single-barrel bypass will have only limited benefit; the branch that is not used to transmit the bypass (inner) catheter will remain occluded. The brain tissue in that distribution cannot be perfused with oxygenated blood and also cannot be treated with selective hypothermic neuroprotection (FIG.2showing partial revascularization of only 1 of 2 branches).

Therefore in this bifurcation embodiment of the stroke catheter a second inner bypass catheter is deployed over a microguidewire, into the second branch at the bifurcation. Microangiography through this second bypass microcatheter demonstrates that the second bypass microcatheter is now beyond the occlusion. Endovascular bypass is implemented as outlined above.

Now that the brain is protected from ischemia, more time may be taken to address the occlusive thrombus. This thrombus is characterized by particularly difficult physical characteristics (hard, organized, clot that had been present in the patient's left atrial chamber for an extended time, and that is resistant to ordinary intravenous thrombolysis) and a problematic physical location (at the bifurcation, it is not amenable to stent-based retrieval, which requires a branch selection, nor to simple aspiration, because it is hard, organized thrombus).

In this situation selective thrombolysis may be implemented by delivering thrombolytic medication to the proximal edge of the occlusion (where the main barrel of the device, and its perforations, is located), and delivering thrombolytic medication through the perforations directly to the clot. In this situation, it is not necessary to inflate the distal balloon, and may be more hazardous to do so because the branch vessels may be significantly smaller than the main trunk of the middle cerebral artery. Because blood flow has been interrupted at this level, however, thrombolytic medication will tend to stay in the area of the clot for a physically concentrated and prolonged impact, similar to having the segment isolated between balloons. These factors contribute to enhanced thrombolytic efficacy.

As the thrombolytic gradually digests the clot, the perforated segment may be moved gradually forward to engage the clot more internally and aggressively, right up to the bifurcation. During selective delivery of thrombolytic medication, the slidably disposed bypass catheter(s) remain in bypass position in order to continue brain protection. In this way the prolonged time exposure and highly concentrated, specifically-directed thrombolytic that are required to dissolve this particularly resistant thrombus are achieved, without compromising the protection of ischemic neurons (death rate approximately 2 million per minute in large vessel occlusion: Saver et al., 2009).

In addition, more thrombolytic agent may be administered within the remaining occlusive clot by retracting either of the two bypass catheters toward the level of the perforations, at variable distances within the remaining thrombus, and delivering thrombolytic agent through the bypass catheter into the clot. During such a maneuver, the bypass function of that particular microcatheter is interrupted. The slidably disposed bypass microcatheter can be returned to distal bypass position at any time.

Effectiveness of the intervention may be monitored by observing return or improvement in intraoperative neurophysiologic monitoring parameters, and periodic microangiography demonstrating bypass patency.

The perforations may also be used to periodically aspirate the proximal portion of the occlusion to which they have access, removing clot debris if possible. The possibility of ultimate escape of smaller clot fragments into the distal branches once the system has been removed remains if thrombolysis is only partially successful, but smaller fragments create lesser occlusions and are also more amenable to subsequent thrombolytic therapy. Since much smaller doses of thrombolytic medication are required using this device (because of specific concentrated delivery and minimized wastage into the general circulation), there remains considerable therapeutic margin for delivery of more medication following the surgical procedure.

Once it has been decided to terminate the intervention (based on time elapsed and demonstration of improved brain electrical potentials, as well as microangiography from the proximal side of the occlusion), the distal perforations may be finally aspirated while withdrawing the device. This will enhance aspiration of lysed particulate material and also entrapment of larger particles against the device wall as the device is withdrawn. Prior to withdrawal of the device, it is helpful to inflate the balloon on the extracranial guide catheter (ECGC). This maneuver halts blood flow in the extracranial carotid or vertebral source artery, and decreases the likelihood that any entrapped clot particles that are being withdrawn are liberated and carried forward into the intracranial circulation.

While example methods and compositions have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, devices, and so on, described herein. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention is not limited to the specific details, the representative revascularization catheter system10, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.