Abstract:
An extension catheter is introduced through the guide catheter and inserted into the treatment area, The extension catheter may have an expandable tip. A suction pump is coupled to the proximal end of the guide catheter to aspirate blood clots or other issue from the treatment location outside the body.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0001]    The present invention relates to methods and devices for removing thromboembolic materials and other tissue from human body. 
       2. Description of the Prior Art 
       [0002]    Aspiration has been used to remove thromboembolic blockages and other tissue from endovascular and non-endovascular locations in the human body. Single-lumen catheters are employed to aspirate a clot from a cerebral vessel, coronary vessels and peripheral vessels. Such procedure in most cases includes placing a distal end/tip of a catheter at the proximal face of the clot and applying vacuum to the clot via a proximal port of the catheter. Fresh and soft clot usually are easily aspirated, while harder, more organized clot tends to clog the catheter. In such cases, the catheter with trapped clot and under suction is removed outside the patient. Then, the removed catheter is cleaned and introduced again to the treatment location to continue the clot removal process if necessary. However, in some cases, the clot is broken up in pieces by mechanical means during catheter removal and multiple introductions, causing a distal embolization and often dangerous clinical complications. 
         [0003]    The latest development of aspiration devices has significantly improved recanalization rates. A direct aspiration, the ADAPT technique for stroke thrombectomy, was recently shown to be an effective and rapid way to achieve cerebral revascularization. This technique focuses on engaging and removing a clot without the use of ancillary devices and solely relying on aspiration forces generated by the suction pump through the catheter. While the use of aspiration alone to remove blood clots has significantly improved in the last several years, a single pass/use success rate still remains below 75%. Therefore, there is a need for better aspiration devices which are simple to use, and can quickly and safely remove thromboembolic material. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    There are three approaches to improve efficacy of removing blood clots using aspiration with a single lumen aspiration catheter: use of stronger vacuum pumps to aid in aspiration of the clot through the catheter, use of larger aspiration catheters; and use of aspiration catheters with expandable tips. 
         [0005]    Currently used aspiration pumps are reaching almost absolute vacuum of approximately 29 in-Hg (&gt;14 psi) and there is very little or no room for improvement with pumps. The other option is to increase the size (e.g., inner lumen) of the aspiration catheters. Increasing the size of aspiration catheters is still possible in coronary and peripheral vessels, but is challenging in applications involving cerebral circulation. Another option is to use a catheter with a larger frontal aperture during blood clot removal. 
         [0006]    Cerebral vessels have a complex vessel pattern and extensive catheter manipulations with a larger size catheter when accessing and navigating these vessels may be risky and cause vessel dissections, perforations and stroke. However, neuro-interventionists would benefit from the availability of catheters that can be easily, quickly and safely delivered through a standard guide catheter, providing a more effective vehicle to aspirate blood clots. 
         [0007]    Increasing the inner lumen size of the aspiration catheters is in most cases related to enlarging the outer size of the catheter, and such approach carries challenges to access the treatment sites, potential clinical complications, and longer procedural time. It is especially risky with a continuous exodus of neuro surgeons to the interventional Neuro-Radiology Field whose manual skills are not always sufficient for such tasks. Therefore, use of aspiration catheters which are easier to navigate and locate at the treatment site with expandable tips may present attractive and desirable clinical alternative to improve blood clot removal. 
         [0008]    The present invention provides alternative options to increase efficacy of clot removal by increasing the flow of removed clots. Increasing the flow within the aspiration catheter may be accomplished by enlarging at least partially the aspiration lumen by combining two catheters that are always an integral part of interventional procedures together: the aspiration catheter and a guide catheter or sheath. Merging these two catheters may be accomplished by placing a modified aspiration catheter having a smaller and shorter tubular body within a larger and longer guide catheter, while providing a suitable seal between them for aspiration. Such approach will increase flow within two combined catheters and result in more efficient clot aspiration. 
         [0009]    Furthermore, such modified extension catheters comprising a short tube attached to a long pushing/pulling wire may have a larger inner lumen compared with longer conventional aspiration catheters. Thus, such short extension catheters may considerably minimize challenges with navigating aspiration catheters to the treatment sites and maneuvering the catheter during clot-removal. 
         [0010]    Additionally, it is also beneficial to provide a larger catheter opening surface on the distal end of the extension catheter. For example, instead of using a conventional circular aperture on the distal end of the aspiration catheter, applying an oval or angulated aperture may improve clot removal. A larger opening lumen of the aspiration catheter may also be achieved by using an expandable tip on the distal end of aspiration catheter. Such expandable tip may be suitable not only when implemented with an extension catheter of the present invention but also with any conventional aspiration catheter currently in clinical use. 
         [0011]    The present invention comprises a coaxial catheter assembly including a guide catheter or sheath, and a shorter aspiration catheter or an extension catheter for use to remove thromboembolic material from the human body. The treatment site may include but is not limited to endovascular locations such as coronary circulation, cerebral and other peripheral circulation, but may also include non-endovascular locations. The guide catheter is delivered into the body through a standard introducer with a hemostatic valve utilizing a conventional 0.025″-0.038″ guidewire. After the guide catheter or sheath is placed inside the body, a 0.025″-0.038″ guidewire is removed and a smaller guidewire in sizes between 0.008″-0.018″ is placed at the treatment location. All these activities are performed under fluoroscopy or using other imaging techniques. Once the smaller guidewire is positioned at or through the treatment site, the extension catheter is introduced over a smaller guidewire into the guide catheter or sheath to the proximal part of the clot or other tissue to be removed. The distal part of the extension catheter is placed outside the guide catheter while the proximal part of the extension catheter remains inside the guide catheter. The clot/tissue removal process begins when a suction pump attached to the proximal end of the guide catheter is activated. Upon activation of suction, a seal between the guide catheter and the extension catheter is activated and blood clots are aspirated from the treatment site outside the body, 
         [0012]    In one aspect of the present invention, a catheter assembly for blood clots and other tissue removal comprises a guide catheter having a distal end, a proximal end and a lumen extending longitudinally, and an extension catheter positioned at least partway inside the guide catheter. The extension catheter includes a distal tubular portion or member and has an open distal end and an open proximal end. The proximal open end of the extension catheter is attached to a pushing/pulling wire that is extended along the inner lumen of the guide catheter and outside the proximal end of the guide catheter. The extension catheter may freely move inside and outside of the guide catheter. 
         [0013]    In one embodiment, the extension catheter has a variable flexibility, being more flexible on the distal end and less flexible on the proximal end. 
         [0014]    In another embodiment, the pushing wire is further attached to the distal end of the extension catheter. The pushing wire may be located in one of the following locations: extended along the main lumen of the extension catheter, placed in a separate lumen within the extension catheter, or partially located in both. 
         [0015]    The distal tubular portion/member of the extension catheter is configured to be extended beyond the distal end of the guide catheter while the proximal portion of the tubular member of the extension catheter remains within the lumen of the guide catheter. The extension catheter portion that remains inside the guide catheter includes at least partially the tubular member and the attached pushing wire. 
         [0016]    The inner lumen of the guide catheter and inner lumen of the extension catheter are aligned accordingly to allow contrast injection and aspiration of blood clots and other tissue. 
         [0017]    In yet another embodiment, the tubular portion/member of the extension catheter may have one of the following openings on the distal and proximal ends, including but not limited to, circular, oval, irregular or any other shape. 
         [0018]    In another embodiment, the extension catheter is adopted for insertion into the proximal end of the guide catheter, can be moved along the entire length of the guide catheter, and may also be at least partially positioned outside of the distal end of the guide catheter. 
         [0019]    The guide catheter and the extension catheter may be provided in separate packages, or in one package with two separate devices. 
         [0020]    In yet another embodiment, the inner diameter of the guide catheter is at least 0.002″ larger than the outer diameter of the extension catheter. 
         [0021]    In another embodiment, the extension catheter has a hydrophilic coating on the outside surface, or a hydrophobic coating on the outside surface, or combination of both coatings. 
         [0022]    In yet another embodiment, a conventional metal pushing/pulling wire is attached to the distal end of the extension catheter, and such wire may have a variety of sizes and configurations, including circular, oval, square, flat, irregular and combination of all. 
         [0023]    In another embodiment, the extension catheter is at least partially made of one of the following materials, including but not limited to polymers, reinforced polymers, metals, or combination thereof. 
         [0024]    In yet another embodiment, an aspiration feature is attached to the proximal end of the guide catheter and may include any suitable vacuum device or machinery attached to the proximal end of the guide catheter, including a hospital line suction, a reusable pump, a disposable pump, syringes and combination of all. 
         [0025]    In another embodiment, a seal between the guide catheter and the extension catheter is achieved by using a soft tip mounted on the distal end of the guide catheter. When the guide catheter/extension catheter is under vacuum, the soft tip collapses and squeezes around the extension catheter providing a suitable seal for aspiration of blood clots. 
         [0026]    In yet another embodiment, a hydrophilic coating is applied on the external surface of the extension catheter to further reduce friction between the extension catheter and the guide catheter and to provide a seal between the guide catheter and the extension catheter. 
         [0027]    In another embodiment, a hydrophobic coating is applied on the external surface of the extension catheter to further reduce friction between the extension catheter and the guide catheter and to provide a seal between the guide catheter and the extension catheter. 
         [0028]    In another aspect of the present invention, a catheter assembly for blood clots and other tissue removal comprises a guide catheter with at least one longitudinal lumen, and an extension catheter having a tubular member with a pushing wire attached and positioned through the guide catheter. The distal end of the tubular member is located outside the guide catheter and the proximal end of the tubular member is located inside the guide catheter. A suction source is attached to the proximal end of the guide catheter and provides more than 20 in-Hg aspiration pressure at the distal end of the extension catheter. The extension catheter may freely move within the guide catheter when aspiration is applied. 
         [0029]    In another embodiment, the outer surface of the extension catheter has a texture to further enable and support the seal space between the outer catheter and the guide catheter during aspiration. Such textured surface may be coated with a hydrophilic coating or hydrophobic coating, or both. The surface texture may comprise a small local deviation of a surface from the perfectly flat or smooth surface, and include surface roughness or waviness. 
         [0030]    In another aspect, a catheter assembly for blood clots and other tissue removal comprises a guide catheter and an extension catheter. The guide catheter has a distal end, a proximal end and at least one lumen extending longitudinally. A soft tip is provided on the distal end of the guide catheter. The extension catheter is positioned through and distally to the guide catheter such that the proximal end of the extension catheter is located inside the guide catheter. A suction source is attached to the proximal end of the guide catheter and provides aspiration pressure along the guide catheter and the extension catheter. During aspiration, a soft tip of the distal end of the guide catheter collapses around, embraces or surrounds the extension catheter, providing a sufficient seal for aspiration of clots. 
         [0031]    In another aspect of the present invention, the presence of blood, saline or contrast may surround the area of the soft tip and further provide a seal between the extension catheter and the guide catheter when under aspiration. 
         [0032]    In another aspect of the present invention, a catheter assembly for blood clots and tissue removal comprises a guide catheter having at least one lumen extending longitudinally and an extension catheter positioned through and distally to the guide catheter. The distal end of the extension catheter is outside the guide catheter and the proximal end of the extension catheter remains inside the guide catheter. There is a seal between the extension catheter and guide catheter. A suction source attached to the proximal end of the guide catheter provides aspiration pressure along the guide catheter and the extension catheter. The inner lumen along the extension catheter is smaller than the inner lumen within the guide catheter to facilitate the flow of clots. 
         [0033]    In yet another aspect of the present invention, a catheter assembly for blood clots and tissue removal comprises a guide catheter having an inner lumen extending longitudinally and an extension catheter having an inner lumen extending longitudinally and at least partially placed through the guide catheter. The catheter assembly further includes means for sealing space between the extension catheter and the guide catheter. The inner lumen along the guide catheter is larger than the inner lumen along the extension catheter to increase the flow of blood clots. 
         [0034]    In another aspect of the present invention, a catheter assembly for blood clots and tissue removal comprises a guide catheter having an inner lumen extending longitudinally, an extension catheter having a tubular portion, and a pushing wire attached to the proximal end of the tubular portion. An expandable tip is located on the distal end of the tubular portion, and the tubular portion of the extension catheter is positioned at least partially inside of the guide catheter. 
         [0035]    In one embodiment, the expandable tip comprises a tubular braid having a proximal end attached to the distal end of the tubular portion of the extension catheter. Such tubular braid is coated with a silicone to secure a shielded tubular configuration. 
         [0036]    In another embodiment, the catheter assembly further includes means for sealing space between the tubular member of the extension catheter and the guide catheter. 
         [0037]    In yet another embodiment, the distal expandable tip opens to a larger size upon release from the guide catheter than its size inside the guiding catheter. 
         [0038]    In another embodiment, the tubular member of the extension catheter is configured to be pushed through and out of the guide catheter and retrieved back into the guide catheter using the pushing wire. 
         [0039]    In yet another embodiment the pushing/pulling wire may be attached to the tubular braid. 
         [0040]    In another embodiment, the tubular braid is configured to have a pre-set expanded shape when released from the guide catheter and such pre-set expanded shape may include the following configurations: tubular, funneled, syphoned, coned, tapered or other similar shape that provides at least partial tip expansion of the tubular braid when pushed outside the guide catheter. 
         [0041]    In another aspect of the present invention, a method for removing blood clots from a treatment location in patient comprises placing a guide catheter inside the patient, positioning a guide wire through the guide catheter at the treatment location, and introducing an extension catheter over the guide wire into the guide catheter to the treatment location. The extension catheter comprises a distal tubular portion/member, and a wire attached to the proximal end of the distal tubular portion/member, wherein the distal end of the extension catheter is partially extended beyond the guide catheter while the proximal end of extension catheter is located inside the guide catheter. Finally, blood clots are aspirated outside the patient using suction attached to the proximal end of the guide catheter. 
         [0042]    In another embodiment, the extension catheter may be repositioned during the removal of blood clots. 
         [0043]    In yet another embodiment, repositioning of the extension catheter is performed during one of the following steps: when the extension catheter and guide catheter are under vacuum, under no vacuum, and during both steps. 
         [0044]    In another embodiment, placing the guide catheter includes placing a sheath. 
         [0045]    In yet another embodiment, there is a seal between the guide catheter and the extension catheter to secure the suction of blood clots from the treatment location through the extension catheter, through the guide catheter and outside the patient. 
         [0046]    In another embodiment, a seal between the extension catheter and the guide catheter is achieved by a soft tip on the distal end of the guide catheter, by hydrophilic coating of the extension catheter, by hydrophobic coating of the extension catheter, or by a combination thereof. In addition, patient blood, contrast and saline may also aid in securing the seal. 
         [0047]    In yet another embodiment, the guidewire is placed beyond blood clots and remains in place during the removal of blood clots. 
         [0048]    In another embodiment, the guidewire is removed from the patient after placement of the extension catheter at the treatment site and during clots removal. 
         [0049]    In yet another embodiment, the extension catheter and guide catheter are removed from the treatment location when the extension catheter gets clogged. 
         [0050]    In yet another embodiment, cleaning the extension catheter from clots is performed outside the patient, and the extension catheter may be introduced again to the treatment area to continue the removal of blood clots. 
         [0051]    In another embodiment, the guide catheter together with the extension catheter are removed outside the patient, cleaned and reintroduced again to continue clot removal. 
         [0052]    In another aspect of the present invention, a method for removing blood clots from a treatment location in patient comprises placing a guide catheter inside the patient, positioning a guide wire through the guide catheter at the treatment location, and introducing an extension catheter over the guide wire into the guide catheter to the treatment location. The extension catheter comprises a distal tubular portion/member having a distal end and a proximal end, and a pushing/pulling wire attached to the proximal end. The distal end of the extension catheter is partially extended beyond the guide catheter while the proximal end of extension catheter is located inside the guide catheter. Finally, blood clots are aspirated outside the patient using suction attached to the proximal end of the guide catheter, and wherein the clot flow within the distal end of the extension catheter is slower than within the guide catheter. 
         [0053]    In another aspect of the present invention, a method for removing blood clots and other tissue from patient comprises placing a guide catheter having a soft tip inside the patient, positioning a guide wire through the guide catheter at the treatment location, introducing an extension catheter with an expandable tip over the guide wire into the guide catheter to the treatment location, and aspirating blood clots outside the patient using suction attached to the proximal end of the guide catheter. 
         [0054]    In another embodiment, the distal expandable tip opens to a larger inner lumen upon release from the guide catheter than inside the guiding catheter, so as to increase the efficacy of the removal of clots. 
         [0055]    In another embodiment, the tubular member of the extension catheter is configured to be pushed through and out of the guide catheter. and retrieved back into the guide catheter using the pushing wire before blood clots removal, during blood clot removal, and during a combination of both. 
         [0056]    In yet another embodiment, the tubular braid is suitable to assume a pre-set expanded shape having a larger distal inner lumen than the proximal lumen when pushed outside of the guide catheter. 
         [0057]    The following terms: “aspiration”, “vacuum” and “suction” are commonly used in this application, and all are related to using negative pressure that generally pertains to the movement of blood clots and other tissue caused by negative pressure. 
         [0058]    As used herein, “treatment site” refers to any location in the body that has been or to be treated by methods or devices of the present invention. Although “treatment site” often refers to an endovascular area including arteries and veins, the treatment site is not limited to endovascular tissue or blood clots. The treatment site may include tissues and blood clots associated with outside of endovascular location, including but not limited to bodily lumens, organs, ducts or localized tumors. 
         [0059]    The treatment sites of the present invention involve blood vessels in the patient&#39;s vasculature, including veins, arteries, aorta, heart valves and particularly including cerebral, coronary and peripheral arteries, as well as previously implanted grafts, shunts, fistulas and the like. In alternative embodiments, methods and devices to remove blood clots and other tissue described herein may also be applied, but are not limited to, the biliary duct, head, nerves, glands, and the like. 
         [0060]    The scope of the present invention is best defined by drawings, descriptions below and the appended claims. In certain instances, descriptions of vacuum physics, well-known devices, compositions, components, mechanisms and methods are omitted so as to not obscure the description of the present invention with unnecessary details. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0061]      FIG. 1  illustrates an extension catheter according to one embodiment of the present invention. 
           [0062]      FIG. 2  illustrates an extension catheter according to another embodiment of the present invention. 
           [0063]      FIG. 3  is a cross-sectional view of a catheter assembly for removal of clots incorporating the extension catheter of  FIG. 1 . 
           [0064]      FIG. 4  is an enlarged sectional view of the distal portion of a guide catheter and the extension catheter of  FIG. 1 . 
           [0065]      FIG. 5A  illustrates another embodiment of the extension catheter with an expandable tip. 
           [0066]      FIG. 5B  is an enlarged sectional view of the area C in  FIG. 5A . 
           [0067]      FIG. 6A  illustrates the expandable tip of the tubular member of  FIG. 5A  in a compressed configuration inside the distal end of the guiding catheter. 
           [0068]      FIG. 6B  shows the distal end of the tubular member of  FIG. 6A  with the expandable tip expanded and positioned adjacent blood clots that are to be removed. 
           [0069]      FIG. 7A  is an enlarged sectional view of one embodiment of the area A/B in  FIG. 4 . 
           [0070]      FIG. 7B  is an enlarged sectional view of another embodiment the area A/B in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0071]      FIG. 1  illustrates an extension catheter  100  that includes a tubular portion  101  and a pushing/pulling wire  102 . The tubular portion  101  has a distal end  103  and a proximal end  104 . The wire  102  is attached to the proximal end  104  of the tubular portion  101  at a connection point  105 . The extension catheter  100  has an outer lumen  106  and an inner lumen  107 . The tubular portion  101  may also include a reinforced wall  108 . One radiopaque marker  109  is located on the distal end  103  of the tubular portion  101 , and another radiopaque marker  110  is located on the proximal end  104  of the tubular portion  101 . The tubular portion  101  of the extension catheter  100  may be 2-100 cm long, while the attached pushing/pulling wire  102  may have any size and length suitable for interventional procedures. 
         [0072]    The tubular portion  101  may be constructed from any suitable biocompatible plastics and elastomers used in medical devices exhibiting the following characteristics: flexibility, durability, softness, and easily conformable to the shape of the treatment and to minimize risk of harm and trauma. 
         [0073]    The tubular portion  101  may also include an inner liner (not shown). The inner liner may be of a polymeric lubricious composition including but not limited to polytetrafluoroethylene (TFE) polymer to reduce friction. The reinforcement  108  may include but is not limited to braid, coils, knit and combinations thereof. The materials of choice can be stainless steel, polymers and super-elastic alloys such as Nitinol. 
         [0074]    The reinforcement  108  may be partially constructed of polymeric fibers or carbon fibers either replacing a portion of the metallic ribbons/wires or polymeric materials or placed in conjunction with a ribbon or wires in the braid. Other metals (e.g., noble metals such as members of the platinum group or gold) may be used in the braid itself in much the same way to impart radiopacity to the braid. To tailor the stiffness of the braid, the braid may first be wound and portions of the ribbon then removed. Also, the reinforcement  108  may be discontinuous leaving polymer alone without reinforcement. 
         [0075]    Ribbons or wires making up the braid and coils can also contain a minor amount of other materials. Fibrous materials, both synthetic and natural, may also be used. In certain applications, particularly smaller diameter catheter sections, more malleable metals and alloys (e.g., bold, platinum, palladium, rhodium, etc.) may be used. A platinum alloy with a few percent of tungsten is sometimes preferred partially because of its radiopacity. Suitable nonmetallic ribbons or wires include materials such as those made of polyaramides (Kevlar), polyethylene terephthalate (Dacron), or carbon fibers. 
         [0076]    The pushing/pulling wire  102  attached to the tubular portion  101  of the extension catheter  100  may have variety of configurations including but not limited to circular, oval, square, flat and combinations thereof. The wire  102  may be made with any suitable metal, preferably Nitinol, and may have a variety of tapered section(s) to provide a proper flexibility and ability to pull and push the tubular portion  101  back and forth within the body or other catheters. 
         [0077]      FIG. 2  shows an alternative configuration for the extension catheter  200 . The extension catheter  200  includes the tubular portion  201  and the pushing/pulling wire  202 . The tubular portion  201  has a distal end  203  and a proximal end  204 . The wire  202  is connected to the proximal end  204  of the tubular portion  201  at a connection point  205  and also is attached to the distal end  203  of the tubular portion  201  at another connection point  206 . Such connection of the wire  202  to the distal end  206  and the proximal end  205  of the tubular portion  201  provides an additional internal reinforcement within the tubular portion  201 , and provides better pushability of the tubular portion  201  when the extension catheter  200  is introduced into another catheter or navigated inside the body. The extension catheter  200  has an outer lumen  208  and an inner lumen  207 . One radiopaque marker  209  is located on the distal end  203  of the tubular portion  201 , and another radiopaque marker  210  is located on the proximal end  204  of the tubular portion  201 . 
         [0078]    The distal end  203  of the tubular portion  201  and the proximal end  204  of the tubular portion  201  may have one of the following openings, including but not limited to circular, oval, elliptical, angulated, irregular shape or combinations thereof. A largest possible aperture or enlargement of the distal end  203  of the tubular portion  201  and/or on the proximal end  204  of the tubular portion  201  will provide higher suction efficacy and better ability to remove blood clots and other tissue. 
         [0079]    Coating of the external surface  211  of the tubular portion  201  of the extension catheter  200  may also be beneficial to reduce the friction of the extension catheter  200  but also to facilitate a seal between the tubular portion  201  of the extension catheter  200  and a guide catheter (not shown). 
         [0080]    There are two most common coatings that may be used on the surface of the tubular portion  201  of the extension catheter  200 : hydrophobic coating and hydrophilic coating. Hydrophobic coatings offer coefficients of friction in the range of approximately 0.15 to 0.3. In contrast, hydrophilic coatings are much more lubricious and have coefficients of friction in the range of 0.005 to 0.2. Hydrophilic coatings, by their nature, must be wet in order to exhibit lubricity, while low friction hydrophobic coatings do not need to be wet. In most cases, a dry hydrophobic coating is more lubricious than a dry hydrophilic coating. 
         [0081]    A primary purpose of hydrophobic coatings such as polytetrafluoroethylene or polyxylylene is to act as a barrier against liquids. If a device must be sealed so that moisture, contrast, saline, blood do not get inside or between, one of these hydrophobic coatings will work well to prevent liquids from or on the device&#39;s surface and act as a sealant over areas where liquid can penetrate. 
         [0082]    Hydrophilic coatings imbibe water and most of them are in fact comprised of more than 90% water when wet. However, most medical hydrophilic coatings rely on primer coats or base coats for adhesion to a surface, and these primers tend to be relatively hydrophobic, which could cause them to act as liquid barriers and serve a seal between outer surface of the tubular portion  201  of the extension catheter  200  and another device. 
         [0083]    Given the differences in functions, applications for hydrophobic and hydrophilic coatings are different, and some applications overlap. The present invention may be one of the examples where both coatings may be advantageous. 
         [0084]      FIG. 3  shows a cross sectional view of a catheter assembly  300  for removal of clots and other tissue. The catheter assembly  300  comprises an extension catheter  301 , a guide catheter  302  and a seal  303 . The extension catheter  301  can be the same as the extension catheter  101  of  FIG. 1 , and is introduced inside the guide catheter  302  through the Touhy Borst  312 . The extension catheter  301  comprises a tubular portion  304  having a distal end  305  and proximal end  306 . The pushing/pulling wire  307  is attached to the distal end  305  of the tubular member  304  at the attachment area  308 , and in this specific embodiment the wire  307  is attached to the proximal end  306  of the tubular member  304  at the attachment area  309 . The manner in which the wire  307  is attached to the tubular member  304  improves pushability of the tubular member  304  when introduced into the guide catheter  302 , and any other procedural manipulations to and at the treatment site. The distal end  305  of the tubular member  304  is positioned outside the guide catheter  302  while the proximal end  306  of the tubular member  306  is positioned inside the guide catheter  302 . The guide catheter  302  comprises a soft tip  313  located on its distal end, and a Y-connector  310  has an outlet arm  311  that functions for suction attachment and the Touhy Borst  312 . 
         [0085]    The soft tip  313  provides a sealing feature, which under suction from within the guide catheter  302  when suction is applied at the suction port  311  folds around the tubular member  304  (not shown) and secures closure around the guide catheter  302 , thus creating vacuum along the tubular portion  304  of the extension catheter  301  and the guide catheter  302 . The seal area  303  is configured to allow a free movement of the tubular portion  304  of the extension catheter  301  within the guide catheter  302 . One radiopaque marker  314  is located on the distal end  305  of the tubular portion  304  and another radiopaque marker  315  is located on the proximal end  306  of the tubular portion  304 . 
         [0086]    In the spirit of this invention, the tubular portion  304  of the extension catheter  301  is shorter than the length of the guide catheter  302 , The length of the tubular member  304  may be within 2-100 cm long, preferably 15-30 cm long. 
         [0087]    Other options to seal the space between the tubular portion  304  of the extension catheter  302  and the guide catheter  302  may include additional member(s) either provided on the outer surface of the tubular portion  304 , within the lumen of the guide catheter  302 , or both. Although the seal options have been described above with respect to certain embodiments, it will be appreciated that various changes, modifications and alterations may be made to such above-described seal embodiments without departing from the spirit and scope of the present invention. 
         [0088]      FIG. 4  shows the catheter assembly  400  with an enlarged distal view inside the blood vessel  401 . The catheter assembly  400  comprises an extension catheter  402  can be the same as the extension catheter  101 of  FIG. 1 . The extension catheter  402  is positioned within the distal end of the guide catheter  403 . The extension catheter  402  comprises a tubular member  404  and a pushing/pulling wire  405  attached to the tubular member  404  at a proximal attachment area  406  and a distal attachment area  407 . A lubricious coating  408  is formed on the outer surface of the tubular member  404 . Such coating facilitates movement of the tubular member  404  within the guide catheter  403  and outside of the guide catheter  403  when within the vessel  401 . The guide catheter  403  has a soft tip  409  on its distal end which provides a less traumatic interface against vessels and other tissue during introduction of the guide catheter into the body. During the placement of the catheter assembly  400  at the treatment side, when there is no aspiration applied, the soft tip  409  is in an “open” position, as shown in  FIG. 7A . 
         [0089]    When aspiration is applied at the proximal end of the guide catheter  403  (at the port  311  as shown in  FIG. 3 ), the aspiration applies to all inner lumen of the catheter assembly  400  along the guide catheter  403  and the tubular portion  404  of the extension catheter  401  as shown by arrows  410 . Aspiration from within the catheter assembly  400  affects the clot  411  surrounding the distal end of the tubular portion  404 . Under aspiration from within the catheter assembly  400 , the clot  411  begins entering the distal end of the tubular portion  404  of the extension catheter  402  as shown by arrow  412 . 
         [0090]    Once aspiration is applied to the proximal end of the guide catheter  403 , the clot  411  starts flowing into the distal end of the tubular portion  404  as shown by the arrow  410 , and creates suction flow resistance. After blood clot(s)  411 / 412  enters the tubular portion  404  of the extension catheter  401 , vacuum pressure increases. The soft tip  409  folds around the tubular portion  404  of the extension catheter  402  and begins acting like a seal, as shown in  FIG. 7B . With higher aspiration pressure within the catheter assembly  400 , a better yielded seal is produced by the soft tip  409  against or around the guide catheter  403 . Also, a blood clot within the seal area (not shown) may aid in providing a better seal. 
         [0091]    In addition, the catheter assembly  400  has a unique configuration for the inner aspiration lumens, with a larger inner lumen  413  within the guide catheter  403  than the inner lumen  414  within the tubular portion  404  of the extension catheter  402 . This unique configuration increases the flow of aspirated clots and improves efficacy of clot removal. 
         [0092]      FIG. 5A  shows an extension catheter  500  according to another embodiment, where the extension catheter  500  comprises a tubular portion  501  and a pushing wire  502 . The tubular portion  501  has an expandable tip  503  attached to the main body  504 . The pushing wire  502  is attached to the main body  504  of the tubular portion  501  at an attachment area  505 . The expandable tip  503  is located on the distal end of the tubular portion  501  and is attached to the tubular portion  501  at an attachment area  506 . The expandable tip  503  has a funneled or conical configuration with the very distal end  507  having a larger inner and outer dimension than the proximal end of the expandable tip  503 . The expandable tip  503  is shown in an expanded configuration in  FIGS. 5A and 5B . 
         [0093]    The expandable tip  503  can be made of a tubular braid  508 , is coated and has its complete surface covered with silicone  509 , as shown in  FIG. 5B . The importance of the expandable tip  503  is the fact that the very distal end  507  has an aperture  510  that has a larger diameter than the diameter of the main body  504 . Such larger aperture on the distal end  507  of the tubular member  501  significantly improves the efficacy of blood clot removal. 
         [0094]    The space or voids within the braid  508  are filled up and covered with silicone  509 , thus creating a shield that prevents penetration and suction of blood clots through the outer surface of the expandable tip  503 . Therefore, it guarantees that the maximum vacuum pressure can be applied at the aperture  510 . 
         [0095]    The tubular braid  508  may be made of a plurality of wires having sizes between 0.0005-0.0030 inches and the same or different inner/outer dimensions, and constructed of wire strands made of metals, alloys, polymers, Nitinol, cobalt-chromium alloys, Platinum, Platinum-Iridium alloys, polymers or combinations thereof. The wire strands may be formed into a tubular circular shape, tubular oval shape or any suitable shapes, and may be made using (but not limited to) circular wires, oval wires, flat wires and combinations thereof. 
         [0096]    The tubular braid  508  angle (angle between two crossing filaments of the braid—not shown) plays an important role of easing the expanding and collapsing braid. An easier-collapsing braid requires less force for pushing the braid through other restrictive tubes when in the collapsed configuration; for example, pushing through the guiding catheter. A small braid angle of less than 30 degrees in the collapsed configuration and less than 70 degrees in the expanded configuration will be more amenable and would create less friction during introduction and manipulations within and outside of the guide catheter. 
         [0097]    The radial size of the overall braid  508  in the expanded configuration may have dimensions in any range between 0.5 mm-50 mm to assure proper fit into the treatment area. The braid  508  of the expandable tip may have between 8 and 144 strands, and a variety of wire configurations including, but not limited, to: one wire on one wire (1/1); one wire on two wires 1/2); two wires on two wires (2/2); two wires on one wire (2/1) and other suitable combinations. 
         [0098]    Silicone or silicone rubbers are synthetic polymers containing silicon together with carbon, hydrogen, oxygen, and are commonly used in medical devices and implants. One of the most unique mechanical properties of silicone rubbers are excellent elongation of 1000% or more, flexibility and a durometer range of 5 to 80 Shore A. Such elongation and durometer ranges will provide the braid  508  with a shield in the expanded and collapsed configurations. It is important to mention that softer forms of silicone have the ability to retain their softness indefinitely. 
         [0099]    The most common assembly methods for joining silicone components include insert molding and bonding. While insert molding process involves injection molding around an existing part, bonding normally entails joining silicone components with other polymers with adhesives. In the present invention, the silicone coat  509  is preferably applied on braid  508  and within the braid  508  strands by dipping. Other silicone covering methods may include but are not limited to tipping and cuffing. 
         [0100]      FIG. 6A  shows an extension catheter  600  having a tubular member  601  comprising an expandable tip  602  connected to a pushing wire  603  at a connection area  604 . The extension catheter  600  is shown inside the guiding catheter  605 , and the extension catheter  600  can be the same as the extension catheter  201  in  FIG. 2 . A soft tip  606  is located on the distal end  607  of the guiding catheter  605 . The tubular member  601  is shown within the guiding catheter  605  before deployment to the treatment site. The expandable tip  602  of the tubular member  601  is in a compressed configuration and exhibits a tubular shape. Once the expandable tip  602  is pushed distally using the pusher wire  603  outside of the guiding catheter  605  and leaves the distal end  607 , the expandable tip  602  will assume its expanded configuration  608  as shown in  FIG. 6B . 
         [0101]      FIG. 68  shows the extension catheter  600  as in  FIG. 6A  but partially outside the distal end  607  of the guiding catheter  605 . The expandable tip  602  is in the expanded configuration and has an enlarged distal aperture  609 . The distal aperture  609  of the expandable tip  602  is positioned at clots  610  to be removed from the vessel  611 . Upon activation of aspiration at the proximal end of the guiding catheter  605  (not shown), suction of clots  610  begins inside the aperture  609  and along the extension catheter  600  and the guide catheter  605 . 
         [0102]    Once suction of the clots  610  starts, vacuum pressure shown by arrows  612  increases inside the extension catheter  600  and the guiding catheter  605 . Suction activation will cause the soft tip  606  of the guiding catheter  605  to encircle the outer surface of the extension catheter  600 , and create a seal. 
         [0103]    The distal expandable tip  602  opens to a larger inner lumen  609  than its normal lumen size upon release from the guide catheter  605  when inside the guiding catheter  605 . The tubular member  601  with a larger lumen  609  of the expandable tip  602  will increase the efficacy of clot removal. 
         [0104]    The tubular member  601  of the extension catheter  600  is configured to be pushed through and out of the guide catheter  605 , and retrieved back into the guide catheter  605  using the pushing wire  603 , before blood clot removal, during blood clot removal, after clot removal and during removal at combinations of these times. 
         [0105]    The expandable tip  602  having a tubular braid and coated with silicone is suitable to assume a pre-set expanded shape of any desired conical configuration when pushed outside of the guide catheter  605 . 
         [0106]    The extension catheter with an expandable tip that is made of a tubular braid and coated with silicone may be embodied in other forms and configurations without departing from the spirit of the present invention. Furthermore, the embodiments of the expandable tip illustrated in the present invention should be considered in all aspects as illustrative and not restrictive and such expandable tip may also be implemented in a conventional catheter and micro-catheter for any suitable use to treat endovascular and outside of endovascular diseases, illnesses or disorders. 
         [0107]    Although this invention has been described with reference to preferred embodiments and examples, those having ordinary skill in this art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention as found in the claims which follow.