Abstract:
An embolectomy device includes an elongated shaft positionable in and movable within a catheter. The elongated shaft having a distal end portion. An expander portion having proximal and distal ends. The expander portion having a first plurality of legs connecting the proximal end of the expander portion to the distal end portion of the elongated shaft and a second plurality of legs connecting the distal end of the expander portion to the proximal end of the intermediate elongated shaft. The expander portion being biased to expand laterally outward from the long axis of the embolectomy device when the expander portion has been moved out of the catheter to engage a clot. A retrieval portion can be provided proximally of the expander portion. A retrieval net can be fixed to the retrieval portion. The expander portion can be at least partially covered by a net. A method for removing clots and other occlusions for body canals is also provided.

Description:
FILED OF THE INVENTION 
       [0001]    The present invention relates generally to embolectomy, and more particularly, relating to a mechanical embolectomy device including a clot expander and a clot particle retriever, and method of using the same. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are currently in excess of 700,000 new or recurrent strokes every year in the United States. It is the third leading cause of death in the United States after coronary artery disease and cancer. Approximately 40% (&gt;250,000) of strokes are due to large vessel occlusion, potentially requiring a device for treatment. 
         [0003]    Treatment must begin with an evaluation of the patient. Diagnostic neuroimaging is used to obtain noninvasive real-time information about the patient. The goal of therapy is to restore perfusion to the ischemic but potentially salvageable brain tissue rather than to the irreversibly damaged brain tissue, since re-establishing blood flow to such damaged tissue can cause complications such as hemorrhage. Determining the cause and location of the blockage is critical to planning the treatment approach. The most common cause of ischemic stroke is acute embolic occlusion. Most patients with acute ischemic stroke have thromboembolic material occluding large cerebral vessels and hence disruption of cerebral blood flow. Removal of the arterial occlusion in a timely manner can provide a substantial reduction in the size and severity of the cerebral infarction, and improvement in the level of disability among survivors. Treatment varies depending on whether the lesion is proximal or distal, whether there is underlying atherosclerotic stenosis at the occlusion site, and whether the proximal extracranial vessel is opened or closed. Where there are proximal arterial occlusions, the physician may attempt clot retrieval, supplemented by direct catheter-directed thrombolysis. Severe stenosis proximal to the occlusion will usually require treatment of the stenosois before or immediately after restoring intracranial flow. 
         [0004]    A current treatment for acute ischemic stroke is intravenous thrombolysis using tissue-type plasminogen activator (TPA). TPA is a naturally occurring enzyme that activates plasminogen into active plasmin, which dissolves fibrin. The dissolution of fibrin in a clot causes thrombolysis. This treatment is suitable for smaller clots, but has limited utility for patients with large clots, such as are often present in acute occlusions of the internal carotid artery (ICA), proximal middle cerebral artery (MCA), and basilar artery (BA). Also, TPA therapy has significant time constraints, and is generally effective only if given within 3-6 hours of stroke symptom onset. Contraindications to TPA and these time constraints led to mechanical embolectomy. 
         [0005]    Mechanical removal of the thrombus is the goal of mechanical embolectomy. Lytic therapy is necessary for non-accessible locations. Mechanical embolectomy is the process by which a mechanical device is inserted into the body, moved through the affected body canal to the site of the occlusion, and then used to mechanically remove the occlusion from the canal to restore blood flow. One such device is the Mechanical Embolus Removal in Cerebral Ischemia (Merci) retrieval device (Concentric Medical, Mountain View, Calif.), which is currently available for routine clinical use in acute ischemic stroke within 9 hours of onset. This device is a flexible and tapered nickel titanium wire with a helically shaped distal tip that can be deployed intra-arterially to entrap and retrieve large vessel intracerebral clots. Other devices are in various stages of development. 
       SUMMARY OF THE INVENTION 
       [0006]    In general, in one aspect, an embolectomy device is provided. The embolectomy device includes an elongated shaft positionable in and movable within a catheter. The elongated shaft having a distal end portion. An intermediate elongated shaft positionable in an movable with the catheter. The intermediate elongated shaft having proximal and distal ends. An expander portion having proximal and distal ends. The expander portion having a first plurality of legs connecting the proximal end of the expander portion to the distal end portion of the elongated shaft and a second plurality of legs connecting the distal end of the expander portion to the proximal end of the intermediate elongated shaft. A retrieval portion having a plurality of legs having proximal and distal portions. The proximal portion being attached to the distal end of the intermediate elongated shaft at the proximal portion of the of plurality of legs of the retrieval portion. The plurality of legs of the retrieval portion being movable laterally outward from a long axis of embolectomy device when the retrieval portion has been moved out of the catheter. The expander portion being biased to expand laterally outward from the long axis of the embolectomy device when the expander portion has been moved out of the catheter to engage a clot. 
         [0007]    An atraumatic distal portion can extend distally from the distal end portion of the plurality of legs of the of retrieval portion. A retrieval net can be fixed to the retrieval portion. The net can be constructed from a polymeric material. The expander portion can be at least partially covered by a net. The net can comprises a biocompatible or non-thrombegenic material. The embolectomy device can further include the catheter. 
         [0008]    In general, in another aspect, an embolectomy device is provided. The embolectomy device includes an elongated shaft positionable in and movable within a catheter. The elongated shaft having a distal end portion. An intermediate elongated shaft positionable in an movable with the catheter. The intermediate elongated shaft having proximal and distal ends. An expander portion having proximal and distal ends, and having a first plurality of legs connecting the proximal end of the expander portion to the distal end portion of the elongated shaft and a second plurality of legs connecting the distal end of the expander portion to the proximal end of the intermediate elongated shaft. A retrieval portion having a plurality of legs having proximal and distal ends and a mid-portion between the proximal and distal ends, and the proximal end being attached to the distal end of the intermediate elongated shaft at the proximal end of the of plurality of legs of the retrieval portion. The mid-portion of the legs being movable laterally outward from a long axis of the embolectomy device when the retrieval portion has been moved out of the catheter. The expander portion being biased to expand laterally outward from the long axis of the embolectomy device when the expander portion has been moved out of the catheter to engage a clot. 
         [0009]    A retrieval net can be fixed to the plurality of legs of the retrieval portion between the mid-portion and the distal end thereof. The plurality of legs of the retrieval portion can be spring arms. The spring arms can comprise a bend at the mid-portion defining proximal and distal portions, the bend biasing the spring arms to a lateral outward position. An atraumatic distal portion can extend distally from the distal end portion of the plurality of legs of the of retrieval portion. The expander portion can be at least partially covered by a net. The net can comprises a biocompatible or non-thrombegenic material. The embolectomy device can further include the catheter. The spring arms can be integral with the intermediate elongated shaft. The spring arms can be attached to the intermediate elongated shaft. 
         [0010]    In general, in another aspect, an embolectomy device is provided. The embolectomy device includes an elongated shaft positionable in and movable within a catheter. The elongated shaft having a distal end portion. An expander portion having proximal and distal ends. The expander portion having a first plurality of legs connecting the proximal end of the expander portion to the distal end portion of the elongated shaft and a second plurality of legs connecting the distal end of the expander portion to the proximal end of the intermediate elongated shaft. The expander portion being biased to expand laterally outward from the long axis of the embolectomy device when the expander portion has been moved out of the catheter to engage a clot. 
         [0011]    An atraumatic distal portion can extend distally from the distal end of the expander portion. The expander portion can be at least partially covered by a net. The net can comprises a biocompatible or non-thrombegenic material. The embolectomy device can further include the catheter. 
         [0012]    In general, in another aspect, a method of performing an embolectomy is provided. The method includes the steps of providing an embolectomy device comprising an elongated shaft positionable in and movable within a catheter, the elongated shaft having a distal end portion, an intermediate elongated shaft positionable in an movable with the catheter, the intermediate elongated shaft having proximal and distal ends, an expander portion having proximal and distal ends, the expander portion having a first plurality of legs connecting the proximal end of the expander portion to the distal end portion of the elongated shaft and a second plurality of legs connecting the distal end of the expander portion to the proximal end of the intermediate elongated shaft, a retrieval portion having a plurality of legs having proximal and distal portions, the proximal portion being attached to the distal end of the intermediate elongated shaft at the proximal portion of the of plurality of legs of the retrieval portion, the plurality of legs of the retrieval portion being movable laterally outward from a long axis of the elongated shaft when the retrieval portion has been moved out of the catheter, the expander portion being biased to expand laterally outward from the long axis of the embolectomy device when the expander portion has been moved out of the catheter to engage an occlusion, and a retrieval net fixed to the retrieval portion. The embolectomy device is manipulated within a catheter to position the expander portion across an occlusion in a body canal. The expander portion is expanded to move the occlusion toward the body canal, thereby creating a lumen. The expander portion is retracted. The retrieval portion is moved proximally so as to engage the occlusion with the retrieval net. The catheter and embolectomy device are removed from the body canal as one with portions of the occlusion contained by the catheter and retrieval portion of the embolectomy device. 
         [0013]    In general, in another aspect, a method of performing an embolectomy is provided. The method includes the steps of providing an embolectomy device including an elongated shaft positionable in and movable within a catheter, the elongated shaft having a distal end portion, an expander portion having proximal and distal ends, the expander portion having a first plurality of legs connecting the proximal end of the expander portion to the distal end portion of the elongated shaft and a second plurality of legs connecting the distal end of the expander portion to the proximal end of the intermediate elongated shaft, the expander portion being biased to expand laterally outward from the long axis of the embolectomy device when the expander portion has been moved out of the catheter to engage an occlusion. The embolectomy device is manipulated within a catheter to position the expander portion across an occlusion in a body canal. The expander portion is expanded to move the occlusion toward the body canal, thereby creating a lumen. The expander portion is retracted, and the catheter and embolectomy device are removed from the body canal leaving the lumen open. 
         [0014]    There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
         [0015]    Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting. 
         [0016]    As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
         [0017]    For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the description serve to explain the principles of the invention, in which: 
           [0019]      FIG. 1  is a side elevation of an embolectomy device in accordance with the principles of the present invention shown fully extended from the microcatheter; 
           [0020]      FIGS. 2-5  are side elevation views of the embolectomy device in accordance with the principles of the present invention shown partially extended from the microcatheter in various stages; 
           [0021]      FIGS. 6-11  are side elevation views of the embolectomy device in accordance with the principles of the present invention shown at various stages of operation removing a clot from a body canal; 
           [0022]      FIG. 12  is a side elevation of an alternative embodiment; 
           [0023]      FIG. 13  is a side elevation of an alternative embodiment; and 
           [0024]      FIGS. 14-17  are side elevation views of the embolectomy device of  FIG. 13  at various stages of operation creating a lumen through in a clot in a body canal 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    There is shown in  FIGS. 1-5  an embolectomy device  10  according to the invention. In  FIG. 1 , the embolectomy device  10  is shown fully extended. In  FIGS. 2-5 , the embolectomy device  10  is shown partially extended in various stages. The embolectomy device  10  is positionable in and movable within a catheter  14 , such as a microcatheter. The embolectomy device  10  includes an elongated shaft such as proximal wire  18  extending through an opening in the microcatheter  14 , an expander portion  16 , and a retrieval portion  12 . The proximal wire  18  can have a proximal end (not shown) and distal end  24 . The expander portion  16  can be provided at the distal end  24  of the proximal wire  18 . The retrieval portion  12  can be provided distally at a spaced distance from the expander portion  16 , and can be connected to the expander portion by an intermediate elongated shaft or intermediate connecting wire  20 . 
         [0026]    The retrieval portion  12  may be formed from or attached to the intermediate connecting wire  20 . The retrieval portion  12  can have a plurality of legs such as spring arms  22  that are connected to the intermediate connecting wire  20 . The spring arms  22  are disposed about a long axis A of the embolectomy device  10 . The spring arms  22  are biased or otherwise moveable to extend partially outwardly ( FIG. 3 ) when not constrained entirely by the microcatheter  14 . When unconstrained by the microcatheter  14  ( FIG. 4 ) the spring arms  22  can extend laterally outward a maximum distance. Movement of the spring arms  22  relative to the microcatheter  14  can thereby be used to control the lateral extension of the spring arms  22  within a range of possible distances between full extension and full retraction. 
         [0027]    A retrieval net  26  can be provided on the spring arms  22  to assist in engaging and removing a clot or other obstruction from a body canal. The net  26  can be constructed of a flexible, thin-walled material such that when the spring arms  22  are positioned within the microcatheter  14 , the net can also be contained within the microcatheter  14 . The net  26  can also move freely into and out of the microcatheter  14  with the retrieval portion  12 . The net  26  can be constructed from a porous or a substantially non-porous material, such as a flexible plastic net or solid sheet material, and/or a biocompatible or non-thrombogenic polymer. The net  26  can be formed from a polymeric material that is adhered or otherwise securely fixed to the spring arms 
         [0028]    The precise arrangement and construction of the spring arms  22  can be varied. In the embodiment shown, the spring arms  22  are elongated and substantially radially disposed about the long axis A of the embolectomy device  10 . The spring arms  22  can be formed separately and attached to the intermediate guide wire  20 , or the spring arms  22  can be integral with the intermediate guide wire  20  and formed by suitable techniques, such as, but not limited to computer-controlled laser cutting, plastic injection molding, or casting. The spring arms  22  can have a mid-portion  30 , which can have a bend, crimp, curve, or other biasing or moving feature or structure which causes the legs/spring arms  22  to extend laterally outward relative to the long axis A of the embolectomy device  10 . In one embodiment, the spring arms  22  are at least partially made of an elastic material, such as plastic or metal. The mid-portion  30  defines proximal portions  32  and distal portions  34  of the spring arms  22 . The retrieval portion  12  can be attached to a distal end  28  of the intermediate connecting wire  20  at the proximal portion  32  of the spring legs  22 . When the proximal portions  32  are positioned within the microcatheter  14 , the proximal portions  32  are retained in a laterally inward position by the inside wall of the microcatheter ( FIG. 2 ). As the embolectomy device  10  is extended from the microcatheter  14 , the spring arms  22  are permitted under the influence of the biasing to extend laterally outward ( FIG. 3 ). As the embolectomy device  10  is moved further out of the microcatheter  14 , the spring arms  22  are moved by the biasing completely out of the microcatheter  14  and extend a maximum lateral distance from the long axis A of the embolectomy device  10  ( FIG. 4 ). The distal portions  34  extend from a lateral maximum distance at the bend  30  to a lateral minimum distance at the distal end  38  of the spring arms  22 . The lateral outward extension of the legs/spring arms  22  can thereby be controlled by the distance which the proximal portions  32  are moved out of the microcatheter  14 . 
         [0029]    The net  26  is joined to the distal portions  34  of the spring arms  22 , such that when the spring arms  22  are laterally extended, the net  26  is opened to that in one embodiment is a substantially conical configuration and retained in that position by the spring arms  22 , as shown in  FIG. 4 . In this position, the net  26  can engage, capture and retain a clot or other obstruction during an embolectomy. The net  26  also retains debris which otherwise might be left in the body canal. An atraumatic distal portion  40  can be provided at the distal end of the embolectomy device  10  for preventing the embolectomy device from penetrating or piercing a body canal as it is moved therethrough. The distal portion  40  can be part of the intermediate connecting wire  20  or can be a separate structure to which the spring arms  22  are affixed. The distal portion  40  can be flexible and non-rigid. The distal portion  40  can include a blunt atraumatic tip  44 . 
         [0030]    The expander portion  16  may be formed from or attached to the proximal wire  18 . The expander portion  16  is disposed about the long axis A of the embolectomy device  10 , and may be biased or otherwise moveable to extend outwardly when not constrained by the microcatheter  14 . The expander portion  16  may have a plurality of legs  48  that connect a distal end  50  of the expander portion to a proximal end  36  of the intermediate connecting wire  20 , and a plurality of legs  52  that connect a proximal end  54  of the expander portion to the distal end  24  of the proximal wire  18 . Legs  48  and  52  may be spring arms, and biased or otherwise moveable to extend outwardly ( FIG. 5 ) when not constrained by the microcatheter  14 , similarly to that of spring arms  22 . Additionally, as with spring arms  22 , the construction and arrangement of spring arms  48  and  52  can be varied. In the embodiment shown, the spring arms  48  and  52  are elongated and substantially radially disposed about a long axis A of the embolectomy device  10 . Spring arms  48  and  52  can be formed separately and attached to the proximal wire  18  and intermediate connecting wire  20 , respectively. Spring arms  48  and  52  can be integral with the proximal wire  18  and intermediate connecting wire  20 , respectively, and can be formed by suitable techniques, such as, but not limited to, computer-controlled laser cutting, plastic injection molding, or casting. In one embodiment, spring arms  48  and  52  are at least partially made of an elastic material, such as plastic or metal. 
         [0031]    A mesh or net  58  can cover a portion or all of the expander portion  16  in order to better engage clot material. The net  58  can be constructed from a porous or a substantially non-porous material, such as a flexible plastic net or solid sheet material, and/or a biocompatible or non-thrombogenic polymer. The net  58  can be integral with the expander portion. Expansion of the expander portion  16  is controlled by suitable means, such as the presence of the microcatheter  14 . When the microcatheter  14  is removed or pulled back from the expander portion  16 , the expander is expanded either by a spring force or a suitable motor. 
         [0032]    The expander portion  16  can be of different designs, but can be a mesh metallic or polymeric device similar to a stent in that it is capable of a first position in which it is tightly compacted laterally, and in another position expands laterally. It is important to understand the expander portion  16  is only stent like, and is not intended to be left in place within a body canal. The expander portion  16  uses this lateral expansion force to spread clot material concentrically outwardly toward the walls of the body canal, opening a lumen through the body canal. In the high energy, compacted state the expander portion  16  is contained within a catheter. When moved out of the catheter, the expander portion  16  assumes an expanded, lower energy state. The expander portion  16  can be completely or partially coated with a polymer, and/or with a therapeutic substance. The expander portion  16  can be porous, non-porous, or partially porous. The expander portion can be formed by suitable techniques, such as, but not limited to, computer-controlled laser cutting, plastic injection molding, or casting. 
         [0033]    Operation of the embolectomy device  10  is shown in  FIGS. 6-11 . In  FIG. 6 , the microcatheter  14  shown positioned within the body canal  62  through and beyond clot  60  using a steerable microwire  61  and standard interventional radiology techniques. With the microcatheter  14  in position in the body canal  62  and through the clot  60 , the steerable microwire is removed from the microcatheter. A contrasting agent can be injected into the microcatheter  14  to confirm the microcatheter is correctly positioned through the clot  60 . While maintaining the position of microcatheter  14  the embolectomy device  10  is inserted into the microcatheter to position the expander portion  16  across the clot  60  ( FIG. 7 ). The embolectomy device  10  is extended from the microcatheter  14  by withdrawing the microcatheter  14  proximally while maintaining the positioning of the embolectomy device. As the proximal portions  32  of the retrieval portion  16  emerge from the microcatheter  14  ( FIG. 8 ), the spring arms  22  begin to extend laterally outward, which extends the mid-portions  30  laterally outward. As the spring arms  22  are moved completely out of the microcatheter  14  ( FIG. 9 and 10 ), the spring arms  22  extend outward a maximum lateral distance relative to the long axis A of the embolectomy device  10 . Continued withdrawal of the microcatheter  14  exposes the expander portion  16 , which is expanded by either spring force or a suitable motor, pressing the clot  60  against the body canal  62  ( FIG. 9 ) and creating a lumen. The expander portion  16  can then be collapsed and retracted into the microcatheter  14  by moving the microcatheter distally over the expander portion. With the expander portion  16  contained within the microcatheter  14 , the embolectomy device  10  can be further retracted, by either moving the microcatheter distally over the embolectomy device  10 , moving the embolectomy device proximally into the microcatheter, or a combination of both such that clot  60  will be engaged by the net  26  ( FIG. 10 ) of the retrieval portion  12  and at least partially pulled into the microcatheter ( FIG. 11 ). The microcatheter  14  and embolectomy device  10  are then removed from canal  62 , as one unit with the retrieval portion  12  and the microcatheter forming a reservoir for containing the clot or emboli  60 . 
         [0034]    The dimensions and construction of the microcatheter  14 , elongated shaft or guide wire  18 , intermediate guide wire  20 , expander portion  16 , retrieval portion  12 , legs/spring arms  22 , and legs  48  and  52  can vary depending on the size of the canal in which the clot is located, the size and position of the clot, and other factors. The dimensions of the retrieval portion  12  can, for example, be between 0.20 mm to 0.45 mm in diameter when collapsed, and between 0.4 mm to 10 mm when open. In one embodiment the retrieval portion  12  can have a length between 2 mm and 22 mm. The dimensions of the guide wire  18  can in one embodiment be 0.35 mm in diameter, and between 0.20 mm to 0.45 mm in diameter. In another embodiment, the dimensions of the guide wire  18  can be 0.25 mm, and between 0.20 mm to 0.36 mm. The dimensions of the penetrating portion  40  can be 0.25 mm in diameter, or between 0.20 mm and 0.45 mm in diameter. The dimensions of the microcatheter  14  can be an outside diameter (OD) 0.60 mm, and an inside diameter (ID) of 0.43 mm, or with an (OD) between 0.40 mm to 1.37 mm, and an (ID) between 0.25 mm to 0.75 mm. The dimensions of the expander portion  16  can, for example, be between 10 mm and 44 mm in length. The length of the intermediate guide wire  20  can be up to 28 mm. Other dimensions are possible. 
         [0035]    The instruments used to position and manipulate the micro catheter  14  and the guide wire  18  can be standard devices or devices specifically designed for use with the invention. Although the legs have been described as spring arms  22 , the invention is also useful when the legs/spring arms  22  are moved laterally outward by a force other than a spring force, as where the legs are driven laterally outward by a motor of some kind, such as an osmotic pump. In other embodiments, the mid-portion  30  of the legs/spring arms  22  can be at least partially elastic or can comprise a hinge structure to permit bending of the legs/spring arms. 
         [0036]    Other embodiments are possible. There is shown in  FIG. 12  an embodiment of the embolectomy device  10  where the intermediate connecting wire  20  is absent, and the retrieval portion  12  is connected directly to the expander portion  16 . Proximal portions  32  of the spring arms  22  can be connected to the legs  48  at the distal end  50  of the expander portion  16 . The remaining aspect can remain as discussed above in the first embodiment shown in  FIGS. 1-11 . 
         [0037]    There is shown in  FIGS. 13-17  an alternative embodiment of an embolectomy device  100  according to the present invention. In  FIG. 13 , the embolectomy device  100  is shown fully extended. In  FIGS. 14-17 , the embolectomy device  100  is shown partially extended in various stages during operation in a body canal. The embolectomy device  100  is positionable in and movable within a catheter  102 , such as a microcatheter. The embolectomy device  100  includes an elongated shaft such as proximal wire  104  extending through an opening in the microcatheter  102  and an expander portion  106 . The proximal wire  104  can have a proximal end (not shown) and distal end  108 . The expander portion  106  can be provided at the distal end  108  of the proximal wire  104 . 
         [0038]    The expander portion  106  may be formed from or attached to the proximal wire  104 . The expander portion  106  is disposed about the long axis A of the embolectomy device  100 , and may be baised or otherwise moveable to extend outwardly when not constrained by the microcatheter  102 . The expander portion  106  may have a plurality of legs  110  at a proximal end  112  of the expander portion, and a plurality of legs  114  at a distal portion end  116  of the expander portion. The proximal end  112  of expander portion  106  can be connected to the distal end  108  of the proximal wire  104 . Legs  110  and  114  may be spring arms, and biased or otherwise moveable to extend outwardly when not constrained by the microcatheter  102 . Additionally, the construction and arrangement of spring arms  110  and  114  can be varied. In the embodiment shown, the spring arms  110  and  114  are elongated and substantially radially disposed about a long axis A of the embolectomy device  100 . Spring arms  110  can be formed separately and attached to the proximal wire  104 . Spring arms  110  can be integral with the proximal wire  104 , and can be formed by suitable techniques, such as, but not limited to, computer-controlled laser cutting, plastic injection molding, or casting.. In one embodiment, spring arms  110  and  114  are at least partially made of an elastic material, such as plastic or metal. 
         [0039]    The expander portion  106  can be of different designs, but can be a mesh metallic or polymeric device similar to a stent in that it is capable of a first position in which it is tightly compacted laterally, and in another position expands laterally. It is important to understand the expander portion  106  is only stent like, and is not intended to be left in place within a body canal. The expander portion  106  uses this lateral expansion force to spread clot material concentrically outwardly toward the walls of the body canal, opening a lumen through the body canal. In the high energy, compacted state the expander portion  106  is contained within a catheter. When moved out of the catheter, the expander portion  106  assumes an expanded, lower energy state. The expander portion  106  can be completely or partially coated with a polymer, and/or with a therapeutic substance. The expander portion  106  can be porous, non-porous, or partially porous. The expander portion can be formed by suitable techniques, such as, but not limited to, computer-controlled laser cutting, plastic injection molding, or casting. 
         [0040]    Expansion of the expander portion  106  is controlled by suitable means, such as the presence of the microcatheter  102 . When the microcatheter  102  is removed or pulled back from the expander portion  106 , the expander portion is expanded either by a spring force or a suitable motor. 
         [0041]    An atraumatic distal portion  118  can be provided at the distal end of the embolectomy device  100  for preventing the embolectomy device from penetrating or piercing a body canal as it is moved therethrough. The distal portion  118  can be part of legs  114  or can be a separate structure to which legs  114  are affixed. The distal portion  118  can be flexible and non-rigid. The distal portion  118  can include a blunt atraumatic tip  120 . 
         [0042]    A mesh or net  122  can cover a portion or all of the expander portion  106  in order to better engage clot material. The net  112  can be constructed from a porous or a substantially non-porous material, such as a flexible plastic net or solid sheet material, and/or a biocompatible or non-thrombogenic polymer. The net  122  can be integral with the expander portion  106 . 
         [0043]    Operation of the embolectomy device  100  is shown in  FIGS. 14-17 . In  FIG. 14 , the microcatheter  102  is shown positioned within the body canal  126  through and beyond clot  124  using a steerable microwire  125  and standard interventional radiology techniques. With the microcatheter  14  in position in the body canal  126  and through the clot  124 , the steerable microwire is removed from the microcatheter. A contrasting agent can be injected into the microcatheter  102  to confirm the microcatheter is correctly positioned through the clot  124 . While maintaining the position of microcatheter  102  the embolectomy device  100  is inserted into the microcatheter to position the expander portion  106  across the clot  124  ( FIG. 15 ). The embolectomy device  100  is extended from the microcatheter  102  by withdrawing the microcatheter  102  proximally while maintaining the positioning of the embolectomy device. Continued withdrawal of the microcatheter  102  exposes the expander portion  106 , which is expanded by either spring force or a suitable motor, pressing the clot  124  against the body canal  126  ( FIG. 16 ) and creating a lumen  128 . The expander portion  106  can then be retracted into the microcatheter  102  by inserting the microcatheter distally over the expander portion  106 . With the expander portion  106  contained within the microcatheter  102 , the embolectomy device  100  can be retracted leaving the lumen  128  and at least partially restoring fluid flow through the body canal  126  ( FIG. 17 ). 
         [0044]    The dimensions and construction of the microcatheter  102 , elongated shaft or guide wire  104 , expander portion  106 , retrieval portion  12 , and legs  110  and  114  can vary depending on the size of the canal in which the clot is located, the size and position of the clot, and other factors. The dimensions of the guide wire  104  can in one embodiment be 0.35 mm in diameter, and between 0.20 mm to 0.45 mm in diameter. In another embodiment, the dimensions of the guide wire  104  can be 0.25 mm, and between 0.20 mm to 0.36 mm. The dimensions of the penetrating portion  118  can be 0.25 mm in diameter, or between 0.20 mm and 0.45 mm in diameter. The dimensions of the microcatheter  102  can be an outside diameter (OD) 0.60 mm, and an inside diameter (ID) of 0.43 mm, or with an (OD) between 0.40 mm to 1.37 mm, and an (ID) between 0.25 mm to 0.75 mm. The dimensions of the expander portion  106  can, for example, be between 10 mm and 44 mm in length. Other dimensions are possible. 
         [0045]    A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.