Patent Publication Number: US-2018042623-A1

Title: Blood Clot Aspiration Catheter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 62/373,846 which was filed on Aug. 11, 2016; U.S. Provisional Application No. 62/416,612 which was filed on Nov. 2, 2016; U.S. Provisional Application No. 62/420,425 which was filed on Nov. 10, 2016; U.S. Provisional Application No. 62/426,111 which was filed on Nov. 23, 2016; and U.S. Provisional Application No. 62/472,474 which was filed on Mar. 16, 2017. The contents of each of the above applications are incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     The disclosed embodiments relate to thrombectomy catheters which are used in the human vascular system to aspirate blood clots. 
     2. Related Art 
     Deep vein thrombosis (DVT) is a common problem and causes significant morbidity and mortality in the United States and throughout the world. DVT is caused when a blood clot forms in the deep veins of the legs. These blood clots typically occur due to slow or reduced blood flow through the deep veins such as when the patient cannot ambulate or otherwise efficiently circulate their blood. Another cause of inefficient circulation may be due to structural damage to the veins such as general trauma or subsequent to surgical procedures. Additionally, a blood clot may form in a deep vein due to a particular medical condition or a propensity for the patient to have a hypercoagulability state. For example, a woman on birth control who smokes has an increased risk of forming blood clots and is thus predisposed to DVT. 
     The result and clinical significance of DVT is when the clot breaks free from its location in the deep vein of the leg, the clot travels through the circulatory system and may eventually lodge in a location that is adverse to the patient&#39;s health. For example, the clot may dislodge from a location in the deep vein of the patient&#39;s leg and migrate through the heart and come to rest in the patient&#39;s lung causing a pulmonary embolism (PE) resulting in restricted circulation and can cause sudden death for the patient. 
     DVT &amp; PE are currently prevented in several ways including anticoagulation therapy, thrombectomy, thrombolysis, and inferior vena cava filter (IVC filter) placement. Anticoagulation therapy utilizes various medications that reduce the patient&#39;s propensity for forming blood clots. 
     Thrombolysis is a medical technique that is performed for treatment of a DVT, in which various medicines are infused into the region of the clot that subsequently causes the clot to dissolve. This form of treatment has the disadvantage that the medication may cause bleeding at other sites such as within the brain. For example, if a patient has previously had a minute non-clinical stroke, the medication used in a thrombolysis may cause a previously healed vessel to bleed within the patient&#39;s head. 
     Thrombectomy is a procedure generally performed for treatment of a DVT, in which a blood clot is extracted from the vein using a surgical procedure or by way of an intravenous catheter using a mechanical aspiration or extraction method. This form of treatment can be technically challenging because the catheter must be steered or navigated to a specific location in order to extract the clot. Currently, there are many different types of mechanical thrombectomy devices using several different means of clot removal. Extraction devices use expanding, removal stents and net/filter types of devices that trap clots which are then pulled out through the original vascular entry point. With aspiration devices, usually either a means of creating low pressure and suction through a catheter is used. A second type of aspiration catheter utilizes a high velocity jet directed back into the catheter to create low pressure and suction using the Bernoulli principle. Both aspiration methods can remove clots out of vessels but are limited because once most of the clot is removed, blood replaces the space resulting in the catheters aspirating mainly blood which makes it hard to get the remaining clot out. These challenges with blood loss during aspiration limits that amount of clot that can be removed and is the genesis of the new clot aspiration catheter in the embodiments described below. 
     SUMMARY 
     Deep vein thrombosis (DVT) is a common problem and causes significant morbidity and mortality in the United States and throughout the world. DVT is caused when a blood clot forms in the deep veins of the legs. Currently therapy involves using pharmacological and/or mechanical means of removing the clot from the vessels. With mechanical thrombectomy, clot is removed by several means including aspiration of the clot via suction through a catheter. 
     Although this can be effective in clot removal, a large portion of the clot may be left behind due to the limitation of non-clotted blood aspiration. Once the clot is removed it is replaced within the vessel by non-clotted blood which are then aspirated together. With more chronic clot there is even greater limitation as the clot is adherent to the vessel wall, and therefore the procedure will take more time, generally yielding more non-clotted blood. 
     In the typical therapy environment of an angiography lab, the clot is not visible while the thrombectomy is being performed making it an even more difficult task. The ideal thrombectomy catheter for the best clot aspiration is one of a large caliber. However, large caliber catheters are not ideal once non-clotted blood has replaced the aspirated clot within the vein. This is because, as explained above, the large-caliber catheter will begin to aspirate a large amount of non-clotted blood. 
     There are systems that have addressed this by capturing the clot by means of filtration outside the body and then having a second venous access for blood return. While operable, this method requires that there is a second entry into an additional vessel and also requires, in most setting, that a blood perfusion specialist be involved. With these systems (AngioVac by AngioDynamics), clot is aspirated with large amounts of non-clotted blood, the aspirated clot and blood are filtered, and the non-clotted blood is returned to the body via a second access site. The systems that do not allow filtration and reinfusion of blood (Indigo by Penumbra) are limited because once significant non-clotted blood is removed from the patient, the therapy must be terminated for obvious health reasons. 
     The disclosed embodiments solve the noted issues by filtering the blood within the patient&#39;s body by means of a filtration catheter in a closed system using a cycle of positive and negative pressures. The designs allow an operator to ultimately acquire only clot from the vessel and retuning non-clotted blood, allowing long working times and complete clot removal. The embodiments include a set of unidirectional valves and filters that separate and direct clot and non-clotted blood. 
     Catheters according to a first embodiment are placed in a vessel like other catheters and may have similar proximal attachments like standard vascular catheters. Within the distal tip, there is an entry valve that, with suction applied to the proximal catheter lumen, will aspirate both clot and non-clotted blood into the catheter lumen. The catheter is then advanced by the operator deeper into the clot and aspiration is again applied acquiring both clot and non-clotted blood. 
     Once there is substantial blood and clot within the catheter, positive pressure is applied to the proximal end of the lumen increasing the pressure within the lumen. This increase pressure forces non-clotted blood through a series of micro-filter valves on the wall of the catheter. With constant positive pressure, the non-clotted blood will be separated and return to the patient&#39;s vein, and the clot will remain in the catheter. The negative pressure cycle then repeats with the operator moving the catheter deeper into the clot and again both clot and non-clotted blood are removed. The positive pressure cycle is then repeated filtering the non-clotted blood back into the body. These cycles are then repeated until there is complete clot removal. When finished, the catheter is then removed. 
     A second embodiment of the design employs a parallel flush catheter alongside of the aspiration catheter to allow the operator to apply a fluid flush that is under pressure creating retrograde flow in aspiration catheter clearing out the clot. This eliminates clot from the catheter without having to remove the catheter from its position in the vessel. 
     In another embodiment, a standard thrombectomy type balloon such as a Fogerty catheter is used remove the clot from the catheter. The balloon is advanced in an ante grade fashion through the catheter in an un-inflated state, and is then inflated and pulled back through the catheter dragging the clot in front of it. 
     The clot then can be collected in a holding container with can be mounted on the aspiration catheter. Clot can also be collected directly out of the proximal end of the catheter. 
     There are many methods to increase and decrease pressures in a catheter with the most common using a syringe. Numerous others including suction pumps and vacuum bottles with regulators may also be used. 
     A third embodiment of the aspiration catheter filters the blood outside of the body by keeping the clot inside the catheter and allowing non-clotted blood to pass through small filters. Instead of having the non-clotted blood return directly into the vessel when filtered outside the blood is first collected in an external cylinder surrounding the catheter with return tubing that leads to the distal aspect of the primary catheter. The captured clot then can be directed by way of valves into a holding container. 
     A forth embodiment of the design uses a parallel convergence of the catheters at the mid-point where there are microvalves to filter the clotted and non-clotted blood. The filtration is helped by a small resistance valve creating back-pressure to separate the blood elements. When the resistance is overcome by pressure the valve allows passage of the filtered clotted blood. 
     A fifth embodiment of the design employs the use of a filter mechanism directly within the syringe or vessel attached to the syringe to separate the blood clot from the normal, non-clotted blood. When the clot is aspirated into the syringe the valve opens allowing flow distal to the filter. Once forward pressure on the plunger of the syringe cause the forward flow to close the valve with then acts as the filter. The clot is filtered and then can be separately eliminated from the syringe by means of a second outflow attached to the syringe constricted more proximal within the syringe with respect to the filter valve. 
     Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a segmented view of a blood clot aspiration catheter showing a proximal end and a distal end, according to an exemplary embodiment. 
         FIG. 2A  shows the distal portion of the catheter of  FIG. 1  with low pressure and flow toward the proximal end with the end valve open, and  FIG. 2B  shows the distal portion of the catheter of  FIG. 1  with high pressure and flow directed toward the distal end with the end valve closed and flow through the micro-valves. 
         FIG. 3A  shows embodiments of the end valve open, and  FIG. 3B  shows embodiments of the end valve closed. 
         FIG. 4A  shows an enlarged view of a single micro-valve, and  FIG. 4B  shows a perimeter of the microvalve shown in  FIG. 4A . 
         FIG. 5A ,  FIG. 5B , and  FIG. 5C  show views of the distal portion of the catheter with enlarged views of micro-valve function with various flow directions. 
         FIG. 6A  shows an aspiration filter with micropores with the flow direction with aspiration, and  FIG. 6B  shows the flow direction with flushing with filtered fluid exiting the catheter through the micropores, according to an exemplary embodiment. 
         FIG. 7A  shows an aspiration catheter pre-engaged with suction and proximal flow,  FIG. 7B  shows the catheter engaged in the clot with unit clot removal,  FIG. 7C ,  FIG. 7D , and  FIG. 7E  show further clot removal,  FIG. 7F  shows reversal of flow with expulsion of non-clotted blood and compaction of the clot units, and  FIG. 7G  shows reversal of flow and clot aspiration through the distal end valve. 
         FIG. 8A  shows a blood clot aspiration catheter with a small parallel catheter, according to an exemplary embodiment,  FIG. 8B  shows an enlarged distal portion of the catheter of  FIG. 8A ,  FIG. 8C  shows an end view of the catheter of  FIG. 8A ,  FIG. 8D  shows fluid pressure forced through the small parallel catheter,  FIG. 8E  shows an aspirated clot within the catheter of  FIG. 8A , and  FIG. 8F  shows clot removal from the catheter. 
         FIG. 9  shows a blood clot aspiration catheter with multiple aspiration valves along the catheter length, according to one exemplary embodiment. 
         FIG. 10A  shows a catheter with multiple microvalves along the catheter length and an accompanying catheter cover, according to one exemplary embodiment, and  FIG. 10B  shows the catheter of  FIG. 10A  with the cover attached. 
         FIG. 11A  shows an aspiration catheter with a central aspiration lumen with numerous outflow valves into a return catheter channel which continues to an outflow lumen, according to an exemplary embodiment, and  FIG. 11B  shows an enlarged view of the distal end of the catheter shown in  FIG. 11A . 
         FIG. 12A  shows an aspiration catheter with a central aspiration lumen with numerous outflow valves into a return catheter channel which continues to the outflow lumen, according to an exemplary embodiment, and  FIG. 12B  shows an enlarged view of the distal end of the catheter shown in  FIG. 12A . 
         FIG. 13A  shows an enlarged view of a distal end of an aspiration catheter with an internal filtration catheter,  FIG. 13B  shows a distal portion of the aspiration catheter of  FIG. 13A  during an aspiration phase,  FIG. 13C  shows the aspiration catheter of  FIG. 13A  during a flushing phase, and  FIG. 13D  shows an enlarged view of the distal end of the aspiration catheter of  FIG. 13A  during the flushing phase, according to one exemplary embodiment. 
         FIG. 14  shows an aspiration catheter that employs a port with a valve that directs clot to a holding container, according to an exemplary embodiment. 
         FIG. 15A  shows a distal end and an enlarged section view of an aspiration catheter with slits creating the micro-valves, according to one exemplary embodiment,  FIG. 15B  is an enlarged view of the slit in an open state,  FIG. 15C  shows an internal filter to be inserted within the aspiration catheter of  FIG. 15A , and  FIG. 15D  shows an enlarged view of the slit in an open state with the internal filter. 
         FIG. 16  illustrates a graph showing a possible cycle of aspiration and flushing over time, according to an exemplary embodiment. 
         FIG. 17A  shows a deflated balloon advanced through the clot,  FIG. 17B  show inflation of the balloon, and  FIG. 17C  shows the balloon pulled pack through the catheter to remove the clot. 
         FIG. 18A  shows a motor driven cylinder creating an aspiration and a flush cycle, and  FIG. 18B  shows a hand operated syringe to create an aspiration and a flush cycle. 
         FIG. 19A  shows a blood clot aspiration catheter facilitating blood filtration outside of a patient, according to an exemplary embodiment,  FIG. 19B  shows a clot aspirated into the filter of  FIG. 19A ,  FIG. 19C  shows a proximal portion of the catheter of  FIG. 19A  with the clot aspirated into the proximal portion,  FIG. 19D  shows positive pressure into the proximal portion of the catheter of  FIG. 19A , and  FIG. 19E  shows clot collection and filtered blood return using the catheter shown in  FIG. 19A . 
         FIG. 20A  shows a removable aspiration filter for an aspiration catheter, according to one exemplary embodiment, and  FIG. 20B  shows the filter in a removed state. 
         FIG. 21A  shows a removable aspiration filter with a blind end filtration unit,  FIG. 21  B shows a blind end filtration unit with microvalves and a mesh filtration system, and  FIG. 21C  shows the filter in a removed state. 
         FIG. 22A  shows another embodiment of a blood clot aspiration catheter,  FIG. 22B  shows an aspiration phase of the catheter in  FIG. 22A ,  FIG. 22C  shows a flush state of the catheter in  FIG. 22A , and  FIG. 22D  shows a clot disposal phase of the catheter in  FIG. 22A . 
         FIG. 23A  shows another embodiment of a blood clot aspiration catheter with a parallel guidewire lumen, and  FIG. 23B  shows a guidewire inserted into the lumen. 
         FIG. 24A  shows another embodiment of a blood clot aspiration catheter with a conjoined aspiration lumen and filtration lumen attached with a connection having micro filters,  FIG. 24B  shows aspiration using a syringe into the aspiration catheter of  FIG. 24A ,  FIG. 24C  shows further aspiration of a clot into a syringe,  FIG. 24D  shows forward fluid pressure from the syringe moving the clot into the filtration lumen with non-clotted blood forced through microvalves, and  FIG. 24E  shows opening of a flow valve and passage of clot into a holding container. 
         FIG. 25  shows another embodiment of a blood clot aspiration catheter with a valve and filter combined and residing within a syringe 
         FIG. 26A  shows a combination filter/valve with a central axis rod holding valve components through attached hinges that have valve stops extending from the hinges, according to one exemplary embodiment, and  FIG. 26B  shows the combination filter/valve in an open position. 
         FIG. 27  shows the filter/valve motion within a syringe based on neutral conditions, syringe aspiration, and flushing. 
         FIG. 28A  shows a blood clot aspiration catheter using the combination filter valve in an aspiration phase, and  FIG. 28B  shows the aspiration catheter in a flush stage. 
     
    
    
     The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a segmented view of a blood clot aspiration catheter showing a proximal end and a distal end, according to an exemplary embodiment. A blood clot aspiration catheter  100  comprises a distal portion  110  and a proximal portion  120 . The length extending from the distal portion  110  to the proximal portion  120  is not shown in  FIG. 1 , but is of sufficient length to access a blood vessel of a patient. The distal portion  110  comprises a distal end  112  to which a one-way valve  114  is attached. A plurality of micro-valves  116  are disposed on distal portion  110  of the catheter  100 . The proximal portion  120  may comprise, for example a luer lock hub  122  and locking device  124  as is known in the art. 
       FIG. 2A  shows the distal portion of the catheter of  FIG. 1  with low pressure and flow toward the proximal end with the end valve open, and  FIG. 2B  shows the distal portion of the catheter of  FIG. 1  with high pressure and flow directed toward the distal end with the end valve closed and flow through the micro-valves. To aspirate a clot within a blood vessel, the distal end  112  of the catheter  100  is steered to a clot location within the blood vessel. As shown in  FIG. 2A , negative pressure creates a flow towards the proximal end of the catheter  100 , and the one-way valve  114  opens to aspirate clot and blood adjacent to the distal end  112 . When positive pressure is applied and the flow is reversed towards the distal end  112 , the one-way valve  114  closes and non-clotted blood is forced through and is filtered by the micro-valves  116 . In this manner, the non-clotted blood is returned to the blood stream and the aspirated clot is maintained in the catheter  100 . In this way, clot may be aspirated without removing a substantial amount of non-clotted blood and without a second blood vessel access point. 
       FIG. 3A  shows embodiments of the end valve open, and  FIG. 3B  shows embodiments of the end valve closed. The one-way valve  114  at the distal end  114  of the distal portion  110  of the catheter  100  may take on a variety of shapes and design now known or later developed. Examples of designs  114   a,    114   b  are shown in both an open and a closed position. These designs are merely exemplary of possible one-way valves that may be used. Other designs of one-way valves are also possible. 
       FIG. 4A  shows an enlarged view of a single micro-valve, and  FIG. 4B  shows a perimeter of the microvalve shown in  FIG. 4A . In some embodiments, the microvalves  116  may be comprises of a hole  40  within the distal portion  110  of the catheter  100 , a filtration portion  44  and valve portion  42 . The valve portion  42  comprises a perimeter  46  that is mostly sealed to the hole  40 . The perimeter comprises a non-sealed side  48  through which filtered, non-clotted blood may flow under positive pressure. The perimeter  46  and non-sealed side  48  may be shaped as shown in  FIG. 4B , or the non-sealed side  48  may continue in an arced manner. Other shapes are also possible. 
       FIG. 5A ,  FIG. 5B , and  FIG. 5C  show views of the distal portion of the catheter with enlarged views of micro-valve function with various flow directions. As shown in  FIG. 5A  when positive pressure creating flow towards the distal portion  110  of the catheter  100  is provided, the pressure pushes non-clotted blood through an opening  52  of the valve  42  of the micro-filters  116 . Specifically, referring also to  FIG. 4A , the opening  52  is created by unsealed portion  48  of the perimeter  46  lifting away from the distal portion  110  of the catheter  100 . Under neutral conditions shown in  FIG. 5B , the valve  42  remains sealed condition  54 . In  FIG. 5C , under negative pressure, the valve  42  continues to be in a sealed condition  56 . 
       FIG. 6A  shows an aspiration filter with micropores with the flow direction with aspiration, and  FIG. 6B  shows the flow direction with flushing with filtered fluid exiting the catheter through the micropores, according to an exemplary embodiment. In  FIG. 6A , a distal portion  610  of a catheter includes a distal end  612  with the one-way valve  114 . In this embodiment, instead of micro-valves, the distal portion  610  comprises a plurality of micropores  616 . The micropores  616  may range from 150 to 300 microns in diameter and are created within the wall of the distal portion  610  of the catheter. The micropores  616  allow only non-clotted blood to flow outward and back into the patient while thicker, clotted blood will remain in the main lumen of the catheter.  FIG. 6A  shows the flow direction during an aspiration phase where the one-way valve  114  is open allowing blood and clot to continue through the catheter to a syringe, for example. 
       FIG. 6B  shows the flow towards the distal end where the flushing flow closes the one-way valve  114  and forces non-clotted blood through the micropores  616  back into the patient. 
       FIGS. 7A-7B  show a method of using a blood clot aspiration catheter.  FIG. 7A  shows an aspiration catheter pre-engaged with suction and proximal flow. In  FIG. 7A , the catheter  100  steered within a blood vessel  770  so that a distal end  112  is adjacent to a clot  780 . Negative pressure is applied to open the one-way valve  114  to begin aspirating blood and clot  780 .  FIG. 7B  shows the catheter engaged in the clot with unit clot removal. As the catheter  100  begins to aspirate clot  780 , clot units  782  are pulled into the catheter.  FIG. 7C ,  FIG. 7D , and  FIG. 7E  show further clot removal, where several clot units  782  are aspirated into the catheter  100  proceeding proximally up the catheter. During this process, non-clotted blood is also aspirated into the catheter  100 . 
     Accordingly,  FIG. 7F  shows reversal of flow with expulsion of the non-clotted blood and compaction of the clot units. When positive pressure is applied, the clot units  782  are pushed back distally but are stopped from exiting the distal end  112  of the catheter via the one-way valve  114 . Meanwhile, the non-clotted blood can pass through the micro-valves  116  and back into the patient.  FIG. 7G  shows reversal of flow and clot aspiration through the distal end valve. In  FIG. 7G , negative pressure is again applied to the catheter  100  removing the clot units  782  proximally through the catheter  100  and aspirating further clot units  784  from the clot  780 . These steps can be repeated until the clot is removed. 
       FIG. 8A  shows a blood clot aspiration catheter with a small parallel catheter, according to an exemplary embodiment,  FIG. 8B  shows an enlarged distal portion of the catheter of  FIG. 8A , and  FIG. 8C  shows an end view of the catheter of  FIG. 8A . In this embodiment, fluid from outside the patient may be introduced to the catheter to remove clots from the catheter after the non-clotted blood has been filtered back into the patient. The catheter  800  comprises a distal portion  810 , a proximal portion  820 , and a small, parallel lumen  830  running the length of the catheter  800 . The proximal portion  820  is configured to be outside of the patient and includes a first hub  802  for fluid insertion into the lumen  830 . A second hub  804  is provided to attach a syringe or other device for providing positive and negative pressure the catheter  800 . A proximal end  806  may be provided to connect to a containment device for retaining clots aspirated by the catheter. 
     The distal portion  810  includes a distal end  812  with a one-way valve  114  and micro-valves  116  similar to the catheter  100 . The distal end  812  further comprises an open intersection  832  allowing flow from the lumen  830  to enter the catheter  800  from the distal end  812 . This is shown in  FIG. 8D  where fluid pressure is forced through the small parallel lumen  830  and through the intersection  832  into the catheter  800 . This allows an aspirated clot within the catheter  800  to be cleared.  FIG. 8E  shows an aspirated clot  780  within the catheter  800 . As fluid flows from the lumen  830  and into the catheter  800  from the distal end, the clot  780  moves proximally through the catheter  800 , for example as shown in  FIG. 8F . 
       FIG. 9  shows a blood clot aspiration catheter with multiple aspiration valves along the catheter length, according to one exemplary embodiment. In some instances, a clot in a blood vessel may extend a considerable length along the blood vessel. Accordingly, there may be a catheter  900  with a distal portion  910  that comprises a distal one-way valve  914  at a distal end  912 , and one or more side-wall one-way valves  940  along the length of the distal portion  910 . Several micro-valves  916  are provided between the one-way valves  914 ,  940 . The one-way valves  914 ,  940  and the micro-valves  916  operate similarly to valve  114  and micro-valves  116 , so an explanation of these is omitted. The catheter  900  may also have a parallel lumen  930  similar to lumen  830  described above. The number of one-way valves  940  and micro-valves  116  may vary depending on vessel size, the clot burden, the age of the clot, or other factors known to those skilled in the art. 
       FIG. 10A  shows a catheter with multiple microvalves along the catheter length and an accompanying catheter cover, according to one exemplary embodiment, and  FIG. 10B  shows the catheter of  FIG. 10A  with the cover attached. Here, a catheter  1000  may comprise a distal portion  1010  with a one-way valve  1014  at distal end  1012 . The catheter  1000  also has several micro-valves  1016  to filter non-clotted blood back into the blood stream. The extra micro-valves  1016  may help to facilitate quicker filtration of the non-clotted blood. In some instances, only a portion of the distal portion  1010  may be in the blood vessel, resulting in some of the microvalves  1016  being located outside of the vessel or outside of the patient. To ensure that the filtered blood returns to the blood vessel, a sleeve or cover  1045  is provided. The cover  1045  is sealed at its proximal end  1046  to the catheter  1000  at a location proximal to the micro-valves  1016 . The cover  1045  is open at the distal end  1048  allowing filtered, non-clotted blood to flow out the distal end  1048 , ensuring that the non-clotted blood is returned to the blood vessel. 
     Other methods of ensuring that the filtered, non-clotted blood returns to the blood vessel are also contemplated.  FIG. 11A  shows an aspiration catheter with a central aspiration lumen with numerous outflow valves into a return catheter channel which continues to an outflow lumen, according to an exemplary embodiment, and  FIG. 11B  shows an enlarged view of the distal end of the catheter shown in  FIG. 11A . In  FIG. 11A , a catheter  1100  comprises several microvalves  1116  in a row on one side of the catheter. A cover  1150  is formed over the catheter  1100  and sealed on both sides of the row of microvalves  1116  creating a channel having an open distal end  1152 . This allows flow to go through the micro-valves  1116  and out the distal end  1152  of the cover  1150 , filtering blood aspirated through the distal end  1112  of the catheter  1100  via the one-way valve  1114 . 
       FIG. 12A  shows an aspiration catheter with a central aspiration lumen with numerous outflow valves into a return catheter channel which continues to the outflow lumen, according to an exemplary embodiment, and  FIG. 12B  shows an enlarged view of the distal end of the catheter shown in  FIG. 12A . In  FIG. 12A , a catheter  1200  comprises several microvalves  1216  in a row on one side of the catheter. The catheter  1200  is formed inside an outer cover  1250  creating a channel between the cover  1250  and catheter  1200 . A distal aperture  1252  is provided at a distal end of the catheter  1200 . The one-way valve  1214  is formed at a distal end of the cover  1250 . This allows flow to go through the micro-valves  1216  and out the aperture  1252  of the cover  1250 , filtering blood aspirated through the one-way valve  1114 . 
       FIG. 13A  shows an enlarged view of a distal end of an aspiration catheter with an internal filtration catheter. In  FIG. 13A , a catheter  1300  comprises an internal filtering catheter  1350  that comprises micro-valves  1316 . A distal end of the filtering catheter  1350  is attached to a wall of the catheter  1300  and includes a port  1352 . 
       FIG. 13B  shows a distal portion of the aspiration catheter of  FIG. 13A  during an aspiration phase. When negative pressure is applied causing flow towards a proximal end, the one-way valve  1314  at the distal end  1312  is opened to aspirate blood and clot.  FIG. 13C  shows the aspiration catheter of  FIG. 13A  during a flushing phase, and  FIG. 13D  shows an enlarged view of the distal end of the aspiration catheter of  FIG. 13A  during the flushing phase. When positive pressure is applied causing flow towards the distal end  1312 , the one-way valve  1314  is closed and non-clotted blood is filtered through the micro-valves  1316  of the internal filtration catheter  1350 . The non-clotted blood is the pushed out the opening  1352  at the distal end of the internal catheter  1350 . 
       FIG. 14  shows an aspiration catheter that employs a port with a valve that directs clot to a holding container, according to an exemplary embodiment. In  FIG. 14 , a catheter  800  is connected to a containment bin  809 . A port or valve  808  may be operated to allow an aspirated clot to move into the containment bin  809 . Each of the hubs  802  and  804  may also include ports or valves to direct flow within the catheter as needed. 
     Other modifications of the above catheters are also possible. For example, each of the above-described catheters may include the micro-valves or micro-pores described above. Further, slits within the catheter may be used to filter the non-clotted blood out of the catheter.  FIG. 15A  shows a distal end and an enlarged section view of an aspiration catheter with slits creating the micro-valves, according to one exemplary embodiment,  FIG. 15B  is an enlarged view of the slit in an open state. In  FIG. 15A , a catheter  1500  comprises several slits  1516  formed in a wall thereof. The slits  1516  are formed at an oblique angle creating a flap  1518 . Because of the oblique flap  1518 , the slit  1516  remains closed during neutral or negative pressure, and opens on positive pressure. For example, in  FIG. 15B  when positive pressure is applied, the flap  1518  is forced upwards creating an opening  1519  allowing the non-clotted blood to escape out of the catheter  1500 . 
       FIG. 15C  shows an internal filter to be inserted within the aspiration catheter of  FIG. 15A , and  FIG. 15D  shows an enlarged view of the slit in an open state with the internal filter. In some embodiments, to add filtration to the slits  1516 , an internal filter sleeve  1555  is provided that is concentric with the catheter  1500 . When positive pressure is applied to the catheter  1500 , the flap  1518  of the slit  1516  rises creating opening  1519 . The blood is filtered through the sleeve  1555  and out of the opening  1519 . 
       FIG. 16  illustrates a graph showing a possible cycle of aspiration and flushing over time, according to an exemplary embodiment. As shown in  FIG. 16 , the cycle may oscillate from a flush phase to an aspiration phase. Any pattern between the flushing and aspiration phases may be used. 
     Other methods may also be used to clear clots that are aspirated into the catheter.  FIG. 17A  shows a deflated balloon advanced through the clot,  FIG. 17B  show inflation of the balloon, and  FIG. 17C  shows the balloon pulled pack through the catheter to remove the clot. A catheter  1700  may be used to aspirate a clot  780  within a blood vessel  770 . A standard thrombectomy type balloon such as a Fogerty catheter  1758  is advanced in an ante grade fashion through the catheter  1700  in an un-inflated state. The balloon  1758  is then inflated and pulled back through the catheter  1700  dragging the clot  780  in front of it. As with the pressure means of clearance previously described the clot can be collected directly out of the back of the catheter or within the holding container. 
       FIG. 18A  shows a motor driven cylinder creating an aspiration and a flush cycle, and  FIG. 18B  shows a hand operated syringe to create an aspiration and a flush cycle. To create the flush and aspiration cycles, both manual and motorized methods may be used. In  FIG. 18A  a catheter  800  is attached to a motorized aspiration device  1864  via a lumen  1862 . The aspiration device includes a motor  1866  that drives, for example, a cylinder to create the positive and negative pressure. The motor  1866  may be driven automatically. For example, it may be controlled via a computer or other device outputting control instructions to the motor  1866 . In  FIG. 18B  a syringe  1868  is attached to the lumen  1862  to manually create positive and negative pressure within the catheter  800 . Variation in the frequency and amplitude of the cycles may vary depending on many factors such as catheter size and clot burden. As previously discussed the low pressure within the catheter draws clot inward and the high pressure filters out the non-clotted blood back into the blood vessel. 
     It is also contemplated that a blood clot aspiration catheter may filter non-clotted blood outside of the patient while still returning the non-clotted blood via a single venous access.  FIG. 19A  shows a blood clot aspiration catheter facilitating blood filtration outside of a patient, according to an exemplary embodiment. A catheter  1900  includes a distal portion  1910  that is inserted into a blood vessel  770  of a patient near a clot  780 . A proximal portion  1920  comprises a fluid collector unit  1922  that houses micro-valves  1924 . A one-way valve  1930  is distally located from the fluid collector unit  1930  to control the flow into and out of the collector unit  1930 . A filtered blood return lumen  1926  is provided with a valve  1928  preventing backflow into the unit  1922 . A collection bin  1932  is also provided proximally from the one-way valve  1930  and distally from the collector unit  1922 . Access to the collection bin  1932  is controlled via port  1934 . 
       FIG. 19B  shows a clot aspirated into the filter of  FIG. 19A . When negative pressure is applied to the catheter  1900  by pulling the plunger  1938  of the syringe  1936 , a clot  780  is aspirated into the catheter  1900 .  FIG. 19C  shows a proximal portion of the catheter of  FIG. 19A  with the clot  780  aspirated into the proximal portion  1920 . In  FIG. 19D , positive pressure is applied into the proximal portion  1920  of the catheter  1900 , closing the one-way valve  1930  and filtering non-clotted blood through the micro-valves  1924  and returning blood to the vessel via the return lumen  1926 .  FIG. 19E  shows clot collection in the bin  1932  when the port  1934  is opened, and continued filtered blood return using the return lumen  1926 . 
       FIG. 20A  shows a removable aspiration filter for an aspiration catheter, according to one exemplary embodiment, and  FIG. 20B  shows the filter in a removed state. In  FIG. 20A , instead of a collection bin, a collector unit  2022  is provided that is removable via couplings  2040 . This allows the operator to accumulate clot in the filter  2040  of the unit  2022 . Once full, the collector unit  2022  is replaced with a clean collector unit  2022 . Specifically, blood and clot are aspirated through the one-way valve  2030  into the collector unit  2022  and syringe  2036  when the plunger  2038  is retracted. When the plunger  2038  is pushed in, non-clotted blood is filtered through the filter  2040  and returned to the vessel via the return lumen  2026  of the catheter  2000  as regulated by valve  2028 . The clots remained trapped within the filter  2040  until the collector unit  2022  is removed and replaced. 
       FIG. 21A  shows a removable aspiration filter with a blind end filtration unit,  FIG. 21  B shows a blind end filtration unit with microvalves and a mesh filtration system, and  FIG. 21C  shows the filter in a removed state. In  FIG. 21A , an alternate collection unit  2122  may be used with a blind filter  2140 . In this case, the filter  2140  filters blood during the aspiration phase as the negative pressure pulls the blood through the filter  2140 . As shown in  FIG. 21B , the filter may be comprised of small valves or holes as shown in filter  2142 , or may be comprised of a mesh with pores of approximately  170  microns to filter blood, as shown in filter  2144 . When the collector unit  2122  fills with clot, the unit  2122  is removed and replaced. 
       FIG. 22A  shows another embodiment of a blood clot aspiration catheter. In this embodiment, catheter  2000  comprises a large clot reservoir  2262  which houses a blood filtration system  2260  that returns non-clotted, filtered blood back into the patient through the distal portion  2210  of the catheter  2200 .  FIG. 22B  shows an aspiration phase of the catheter  2200 . In the aspiration phase, flow is drawn through inlet lumen  2220 , through one-way valve  2252 , and into the syringe  2036 . When positive pressure is applied in  FIG. 22C  showing a flush state of the catheter  2200 , flow reverses out of the syringe  2036 , through one-way valve  2254 , and into the clot reservoir  2262 . When the clot reservoir is full, the flush state filters the blood through the filter  2260  and returns the blood to the vessel of the patient. In  FIG. 22D , clots are disposed when port  2266  is opened allowing the clot to travel through clot lumen  2263  into bin  2268 . 
       FIG. 23A  shows another embodiment of a blood clot aspiration catheter with a parallel guidewire lumen, and  FIG. 23B  shows a guidewire inserted into the lumen. In  FIG. 23A , a catheter  2300  is provided with a parallel lumen  2350  having a proximal inlet  2354  and a distal outlet  2352  at a distal end  2312  of the catheter  2300 . A guidewire  2360  may be inserted into the lumen  2350  to help maintain vessel access, steer the catheter  2300 , and protect the walls of the vessel. 
       FIG. 24A  shows another embodiment of a blood clot aspiration catheter with a conjoined aspiration lumen and filtration lumen attached with a connection having micro filters. In  FIG. 24A , a catheter  2400  is provided having a distal portion  2410  and a proximal portion  2420 . 
     The distal portion  2410  is steered within a blood vessel  770  to a clot  780 . The proximal portion comprises a one-way valve  2452  and a filter lumen  2456 . In an aspiration phase as shown in  FIG. 24B , a syringe  2036  is used to pull blood and the clot  780  into the syringe  2036 , shown in  FIG. 24C .  FIG. 24D  shows forward fluid pressure from the syringe  2036  moving the clot  780  into the filtration lumen  2456 . Non-clotted blood is forced through micro-valves  2416 . The forward pressure closes the one-way valve  2452  diverting the blood into the filtration lumen  2456 .  FIG. 24E  shows opening of a flow valve  2454  and passage of clot  780  into a holding container  2268 . 
       FIG. 25  shows another embodiment of a blood clot aspiration catheter with a valve and filter combined and residing within a syringe. In  FIG. 25 , a filter/valve combination  2538  is disposed with a syringe  2536 . It is noted that while the filter/valve combination  2538  is shown in the syringe  2536 , the filter valve combination could be outsides of the syringe in series with the catheter  2500 . Located within the syringe  2536  proximal to the filter valve  2538  there is a side tube  2540  with a flow switch  2566  that drains into the collecting container  2568 . 
       FIG. 26A  shows a combination filter/valve with a central axis rod holding valve components through attached hinges that have valve stops extending from the hinges, according to one exemplary embodiment, and  FIG. 26B  shows the combination filter/valve in an open position. The filter valve  2600  is shown where valve hinge  2616  fits over the valve axis rod  2614  allowing for free rotation. Valve stop  2618  limits the motion of the valve  2600  keeping valve components  2610  and  2612  in line at  180  degrees in the closed position.  FIG. 26B  shows the filter/valve  2600  in the open position based on the direction of flow where components  2610 ,  2612  rotate about the center axis  2614 . 
       FIG. 27  shows the filter/valve motion within a syringe based on neutral conditions, syringe aspiration, and flushing. In  FIG. 27 , when the syringe  2700  is in a neutral state, the filter/valve  2600  remains closed. When the plunger  2702  is retracted, the flow causes the filter/valve  2600  to move to the open position. And when the plunger is pushed in, the filter/valve  2600  returns to the closed position. 
       FIG. 28A  shows a blood clot aspiration catheter using the combination filter valve in an aspiration phase, and  FIG. 28B  shows the aspiration catheter in a flush stage. In  FIG. 28A , the syringe plunger  2702  is pulled back creating lower pressure in the syringe  2700  and catheter  2800  opening the filter valve  2600  allowing the clot  780  to enter the syringe  2700 . With forward movement on the syringe plunger  2702  as shown in  FIG. 28B , the pressure in the syringe  2700  increases and the filter valve  2600  closes filtering clotted and non-clotted blood. The clot  780  remains in the syringe  2700 . By opening flow valve  2566  the clot is dropped into the collection container  2568 . 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. In addition, the various features, elements, and embodiments described herein may be claimed or combined in any combination or arrangement.