Patent Publication Number: US-2020297365-A1

Title: Obstruction Removal System

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. application Ser. No. 15/821,409 filed Nov. 22, 2017 entitled Obstruction Removal System, which claims benefit of and priority to U.S. Provisional Application Ser. No. 62/426,113 filed Nov. 23, 2016 entitled Obstruction Removal System, which is hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to devices used to capture and remove obstructions, such as clots or other matter, from the vascular system, and delivery of these devices to a target area within the vascular system. 
     The buildup of thrombi in vasculature can lead to formation of blood clots. The formation of clots can result in restricted blood supply to downstream areas of the vasculature. When located in the neurovascular system, these clots can lead to stroke. 
     Recent technologies to remove clots utilize devices designed to hold and capture the clot, followed by withdrawal of the device to physically remove the captured clots from the body. Several of these devices may fail to capture the clot in its entirety, or may promote clot fragmentation which may allow thrombi to dislodge and accumulate at another site, thus continuing the risk of stroke. In addition, several of these devices may promote endothelial denudation due to high friction between the device and the vessel wall. 
     There is need for an obstruction removal device which reduces the likelihood of fragmented thrombi staying in the vasculature while maximizing the chance of mechanically capturing the clot, and limiting the risk of endothelial denudation. 
     SUMMARY OF THE INVENTION 
     In one embodiment according to the present invention, an obstruction removal device is described having a proximal axial core structure, a distal bumper structure and one or more engaging members mounted to the distal bumper structure. 
     In another embodiment according to the present invention, an obstruction removal device is described having a proximal structure, distal structure, and one or more connected engaging members between the two structures. 
     In another embodiment according to the present invention, an obstruction removal device is described having a proximal structure, distal structure, and one or more connected engaging members between the two structures, where at least one of the engaging members acts as a filter. 
     In one example of the previously described embodiments, the plural engaging members are substantially similar to each other. 
     In another example of the previously described embodiments, some of the plural engaging members are not substantially similar to the other engaging members. 
     In another example of the previously described embodiments, some of the plural engaging members actively engage the clot while one or more of the remaining engaging members do not engage the clot. 
     In one embodiment, the obstruction removal device is sheathed within a delivery device and delivered through a catheter. 
     In another embodiment, the obstruction removal device is delivered directly through the catheter. 
     In another embodiment, the device is used to retrieve foreign objects. 
     In one embodiment, the obstruction removal device comprises a plurality of obstruction engaging members linked together with individual linkages. The linkages link a pair of engaging members together. 
     In one embodiment, the obstruction removal device comprises one or more engaging members where the engaging members include some struts spanning the entire length of the elements and some struts that do not span the entire length of the elements. Some of these struts have radiopaque markers to augment imaging of the obstruction removal device. 
     In one embodiment, the obstruction removal device comprises one or more engaging members where the engaging members include twisted struts. The twisted struts provide a non-parallel surface which contacts the blood vessel wall, better enabling the twisted struts to scrape the vessel walls and remove hard or calcified clot. 
     In one embodiment, the obstruction removal device comprises one or more catch elements and one or more engaging members which engage the clot. In one embodiment, the catch elements and engaging members sit on a common core wire. In one embodiment, the catch elements can slide on or over the core wire while the engaging members are fixed to the core wire. 
     In one embodiment, the obstruction removal device comprises a plurality of fixed non-rotating engaging members which are rotatably offset from each other a certain number of degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which 
         FIG. 1  is an engaging member used in an obstruction removal device. 
         FIG. 2  is another view of the engaging member used in an obstruction removal device. 
         FIG. 3  is an obstruction removal device according to one embodiment of the present invention; 
         FIG. 4  is an obstruction removal device according to another embodiment of the present invention; 
         FIG. 5  is an exploded view of the obstruction removal device shown in  FIG. 4 ; 
         FIG. 6  is a magnified view of the proximal engaging member of the obstruction removal device of  FIGS. 4 and 5 . 
         FIG. 7  is an obstruction removal device according to another embodiment of the present invention; 
         FIG. 8  is an exploded view of the obstruction removal device shown in  FIG. 7 ; 
         FIG. 9  is one of the distal engaging members used in the device shown in  FIGS. 7 and 8 . 
         FIGS. 10-12  illustrate a method of deploying the obstruction removal device described in the previous embodiments. 
         FIG. 13  illustrates a hypotube used to create an engaging member 
         FIGS. 14-16  illustrate a process used to help set the final shape of an engaging member 
         FIG. 17  illustrates an obstruction removal device comprising engaging members where the engaging members include some struts than span the length of the engaging member and some struts that do not span the length of the engaging member. 
         FIGS. 18 a , 18 b , 18 c , and 18 d    illustrate various views of the obstruction removal device of  FIG. 17 . 
         FIG. 19  illustrates a marker coil used on the engaging member struts of  FIGS. 17-18   d.    
         FIG. 20  illustrates an engaging member used in an obstruction removal device where the engaging member has a twisted strut pattern. 
         FIG. 21  illustrates a hypotube used to create the twisted strut pattern engaging member of  FIG. 20 . 
         FIGS. 22-24  illustrate an obstruction removal device comprising a catch element and an engaging member. 
         FIG. 25  illustrates an obstruction removal device comprising multiple catch elements and multiple engaging members. 
         FIG. 26  illustrates a linkage system used between engaging members of an obstruction removal system, where the engaging members are capable of independent rotation. 
         FIG. 27  illustrates an obstruction removal device with fixed engaging members. 
         FIG. 28 a    illustrates a first embodiment of an obstruction removal device&#39;s interaction with thrombus against a vessel wall. 
         FIG. 28 b    illustrates a second embodiment of an obstruction removal device&#39;s interaction with thrombus against a vessel wall. 
         FIG. 29  illustrates an engaging member composed of drawn filled tube wires. 
         FIG. 30  illustrates an engaging member in which half of its structure is composed of drawn filled tube wires and its other half is composed of laser cut struts. 
         FIG. 31  illustrates an engaging member in which half of its structure is composed of drawn filled tube wires and its other half is composed of braided wires forming a mesh concave filter. 
         FIGS. 32 and 33  illustrate an engaging member that has a radially offset shape with a flat/straight side and a curved side. 
         FIG. 34  illustrates a clot retrieval device having two flowering petal engaging members that open in a distal direction. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     For the purposes of the terminology described below, the terms clot, thrombus, embolus, and obstruction can be used synonymously. Though an obstruction removal device is described, the device can also be used to capture clots, thrombi, emboli, foreign bodies, or other matter. Engaging members on the device can engage clot, thrombus, embolus, foreign bodies, obstructions, or other matter. 
       FIGS. 1 and 2  show an engaging member  100  used with the obstruction removal device of the present invention. One or more engaging members are used as part of an obstruction removal device in order to engage thrombus which can accumulate within a vascular system. General engaging member shapes can include, but are not limited to, round, oval, elliptical, hourglass, spherical, basket, stent, countered, rectangular, prismatic, cage. Each engaging member  100  has a number of struts  101  which define a number of cells, or openings  102 , and a pair of opposing holes  103  and  104 . For the sake of convention, hole  103  is a distal hole and hole  104  is a proximal hole. 
     Each engaging member may be uniquely configured with different struts, cells, cell sizes, materials, and/or shapes. The strut design can have a linear, wave, sinusoidal, or zig-zag pattern, or can have a non-symmetrical design (i.e. where struts on one side of the engaging member are not mirrored on the other side of said engaging member). The non-symmetrical strut design may help facilitate a rotational component on the member as it travels through a vessel, by shifting the center of gravity from the geometric center of the engaging member. This ease of rotation makes it easier for the engaging members, and therefore the obstruction removal device, to move more easily through the anatomy, especially after the clot has been engaged and the device is being pulled back through the vasculature. This ease of rotation can also limit the amount of damage to the vessel wall due to excessive contact friction by limiting the damage to a particular section of the wall. The engaging members may have either identical or unique designs on each end of the engaging member. This may be done by varying shape of the struts and/or cells, and/or varying the cell density of each end, thus—for example—allowing for large cell sizes on one end and smaller cell sizes on the opposing end. This variability may allow for different properties to allow for enhanced ability to engage the clot, or enhanced ability to track the obstruction removal device and deployed engaging members through the vessel. 
       FIG. 2  shows an engaging member  100  having a plurality of struts  101  having different thicknesses. More specifically, a plurality of end struts  101   a  branch out from the material defining proximal hole  104 , and one or more of these struts  101   a  split to form struts  101   b . Struts  101   b  are shown with features  105  protruding therefrom. Features  105  may be any interruption in the otherwise continuous surface of the strut  101 . Non-limiting examples include barbs, bumps, protrusions, spikes, branches, nubs, and the like. The struts  101   b  are then shown as joining an adjacent struts  101   b  to form thicker struts  101   c , which then split again to form additional struts  101   d , also shown as having features  105 . These struts  101   d  then join together again to form thicker struts  101   e , which are connected to define distal hole  103 . As such, it is seen that, in this particular embodiment, the struts interconnect to form a web of struts that span from the proximal hole  104  to the distal hole  103 . 
     Another strut configuration could utilize a single strut pattern. An example includes a contiguous, helical strut configuration running between the proximal and distal ends of the engaging member, or running between a portion of the length spanning the proximal and distal ends of the engaging member. 
     Each engaging member has a collapsed configuration when sheathed within a delivery device, and takes on an expanded configuration as shown in  FIGS. 1 and 2  when unsheathed. Each engaging member can be self-collapsible and self-expandable based on whether an external force is applied to constrain it (as would be the case when sheathed in a delivery device), or no constraining force is present (as would be the case when unsheathed). 
     The engaging member may be formed from nitinol, or a similar material, and may be laser cut to achieve the profile shape. Other materials and other cutting and/or machining processes would fit within the scope of the invention. 
     The distal and proximal holes,  103  and  104 , on respective distal and proximal end of the engaging member, may facilitate placement of a common rod on which each engaging member sits, or they may fit separate connection pieces to connect multiple components of the obstruction removal device with the respective engaging members. 
       FIG. 3  illustrates an obstruction removal device  200  according to one embodiment of the present invention. The obstruction removal device comprises a proximal core structure  201  at one end of the device, a distal bumper structure  202  connected to the proximal core structure  201 , and one or more engaging members  203  mounted to the distal bumper structure  202 . In one example, the device is pushed and/or pulled from the core structure  201  end. A pusher may sit under the core structure, or the core structure itself may act as a pusher. 
     Core structure  201  may be made of a variety of materials, including, but not limited to, nitinol, stainless steel, cobalt chromium, or a polymeric material such as PTFE, Pebax, TPE, Engage, polyethylene, or other similar materials. Core structure configurations can include, but are not limited to, a coil, a braid, or a coil/braid combination. 
     The bumper structure  202  may be made of a radiopaque material, including, but not limited to, platinum, tantalum, palladium, or other similar material. A radiopaque material is preferred to make imaging of the device easier during the device insertion procedure, although non-radiopaque materials may also be used. The engaging members being mounted to the bumper structure, where the bumper structure is made of a radiopaque material, aids in imaging the device during the clot removal procedure. The engaging members may be mounted to the bumper structure in several ways. For example, the bumper structure may have a threaded outer profile, where the holes of the engaging members have a corresponding receiving structure to rotatably mate to the threaded bumper structure profile. Alternatively, the bumper structure may have a non-threaded outer configuration, and the engaging members may be affixed to the bumper structure by a heat treatment procedure, such as welding. Other mechanical means or other heat treatment procedures can also be used to affix the engaging members to bumper structure. 
       FIG. 4  illustrates an obstruction removal device  300  according to another embodiment of the present invention. The obstruction removal device  300  includes a proximal structure  301  connected to one or more engaging members  303 . There may be a distal structure  302  attached to a distal-most engaging member (labeled as  306  for clarity, though it may be structurally the same or different as the other engaging members  303 ). The one or more engaging members  303  are connected to the proximal structure in such a way as to allow the one or more engaging members  303  to rotate independently of the proximal structure  301 . The one or more engaging members  303  may be linked together to allow the engaging members  303  to rotate independently of each other as well, as discussed in more detail below. The obstruction removal device  300  is preferably pushed/pulled from one end of the proximal structure  301 , thus the terms proximal portion structure and distal structure are used relative to the pushing/pulling end. Although five engaging members are illustrated in the figure, fewer or more engaging members can be used. Like all of the embodiments described herein, the engaging members  303  are constructed with one or more struts  101 , as described above. 
       FIG. 5  illustrates an exploded view of an embodiment of the obstruction removal device  300  of  FIG. 4 . The proximal structure  301  may include a core wire  307  which sits under a coil  309 , which may sit under a tube  310 . The core wire  307  includes a flared end  308 . The core wire  307  may be made of nitinol, or a similar material, although other materials are within the scope of the invention. The coil  309  may be made of tantalum, or other radiopaque materials, although non-radiopaque materials may also be used. The tube  310  may be made of PET, or other polymeric material, although non-polymeric materials may be used as well. The proximal structure also includes another coil  311  which is preferably more gapped than coil  309 , and can be made of a similar material. Coil  311  sits between core wire  307  and the over-coil  309 , and helps center core wire  307  within coil  309 . Proximal structure  301  is connected to a proximal engaging member  302 , which can in turn be connected to another engaging member if more than one engaging member is used in the obstruction removal device. 
     The distal structure  302  includes a monofilament  315  which sits under a coil  316 . Alternatively, multiple monofilaments can be bonded together to produce a monofilament structure  315 . The monofilament  315  can be made of a stretch-resistant polymer such as Engage, although other materials may be used. The coil  316  may be made of tantalum, or other radiopaque materials, although non-radiopaque materials may also be used. Adhesive, preferably UV curable adhesive,  317  is used at both ends of the coil structure  316  in order to keep the monofilament  315  integral within the coil  316 . In one example, the distal structure can act as a guidewire. 
     A distal structure  302  may be connected to the distal-most engaging member  306 . This distal structure may be radiopaque in order to aid in imaging of the device during deployment. In the embodiment of  FIG. 5 , the coil of the distal structure  302  fits within the hole  103  of the distal-most engaging member  306 , and a retaining piece  312  fits on the other end to keep the distal portion  302  integral with engaging member  306 . The retaining piece is welded within the interior of the structure of hole  103 . The engaging member  306  can still rotate. The retaining piece may be of a tubular construction, and may be made from nitinol, although similar materials can also be used. In order to aid in imaging, the retaining piece may be made from nitinol filled with a radiopaque material. Alternatively, the retaining piece may be coated with a radiopaque material to aid in imaging of the device during the procedure. Alternatively, the retaining piece may be made of a radiopaque material. 
     The connection mechanism used to connect the engaging members together is shown in  FIGS. 5 and 6 .  FIG. 6  illustrates the connection structure of engaging member  303 , which is connected to the proximal structure  301  of the obstruction removal device. 
     The connection mechanism includes a link  313  with two flared ends  314 , and retaining pieces  312 . The link  313  may be made of stainless steel, although similar materials may be used. The flared ends extend within the opposing holes  103 ,  104  of the engaging members being connected, and the retaining piece  312  fits next to the flared end  314  to secure the link  313  within the hole of the engaging member. This connecting structure is used to connect the engaging members together, if more than one engaging member is used in the obstruction removal device. Retaining piece  312  is welded to the hole, and the link can rotate while secured within the hole of the engaging member. The engaging members may independently rotate. 
     Engaging member  303  is also connected to the proximal structure  301 , as shown in  FIGS. 5 and 6 . The flared end  308  of the core wire sits past hole  104  of engaging member  303  and a retaining piece  312  sits over the core wire  307  to secure the proximal structure  301  to engaging member  303 , where retaining piece  312  is welded within hole  104 . A smaller, gapped coil  311  sits within the distal end of coil  309  and serves to help center the core wire  307  within the coil  309 . 
     In one example, the connecting piece  313  is placed within the hole structure, and retaining piece  312  is welded into the hole over the connecting piece. The flared end  313  can subsequently be laser welded on the end of the connecting piece. In another example, the retaining piece  312  is welded into the hole and the connecting piece is placed within, and the flared end is laser welded. Although laser welding is specified, other similar heat treatment techniques can be utilized as well. This procedure can also be utilized at the end of core wire  307  to produce flared end  308 , and to connect proximal-most engaging member  303  to the proximal portion  301  of the device. In one example, this procedure can be utilized at the end of the coil  316  when connecting the distal portion of the device to distal-most engaging member  306 . 
     Each engaging member has a rotational component; this ability to rotate can aid in capturing the thrombus and navigating the vessel. This can also help limit the amount of endothelial denudation that may occur as the device is being pushed and/or pulled through the vessel, by helping to limit any excessive forces that build up due to excessive contact friction between the struts and the vessel wall. The engaging members may also be configured to have a more rounded, smoother profile (as illustrated in the figures) which would eliminate any sharp edges on the engaging members which may otherwise promote denudation due to high contact friction. Furthermore, due to the space between the engaging members, less material physically contacts the vessel than other designs which may utilize, for example, a longer one-piece clot engaging unit. Less material contacting the vessel will also serve to limit endothelial denudation during the clot removal procedure. 
     In one example, the proximal portion  301  of the obstruction removal device can include means to detach the engaging members from the obstruction removal device. The detachment means can be included on the portion of the proximal portion  301  contacting engaging member  303  (the proximal-most engaging member) and can include electrolytic, mechanical, thermal, or other means known in the art to induce severing and/or degradation of a linkage. 
     One or more of the engaging members may actively engage the clot, while other members can sit either distally beyond, or proximally before, the thrombus—depending on the size of the clot and the number of engaging members utilized on the device. Due to the potential variability in the individual shape and/or profile of each engaging member, as well as the number of engaging members used in the obstruction removal device compared to the size of the clot, one or more engaging members may sit distally past the clot and have a denser cell configuration to act as a filter for catching thrombus that may dislodge when capturing the clot utilizing the obstruction removal device. 
     The engaging member(s) which act as a filter may have a mesh configuration; said mesh configuration can be throughout the whole engaging member or be located on one particular side of the engaging member, in order to maximize the chances of catching loose thrombus without the thrombus dislodging. In one example, the engaging member(s) which act as a filter has a denser cell configuration on the more-distal portion of said member in order to catch thrombus dislodged from interaction of the more proximal engaging members with the clot. This arrangement can be useful when the more proximal engaging members interact with the clot and portions of the clot macerate. The more distal engaging members with the filter configuration can catch macerated thrombus that otherwise might accumulate in the bloodstream. The engaging members which act as a filter may be formed from nitinol, stainless steel, or similar materials. 
     Alternatively, they may be formed from laser cut polymers. Alternatively, these engaging members acting as filters may have an inverted braid configuration, or other basket-type configurations, or other configurations known within the embolic protection device art. One or more of the engaging members may also be composed of a thrombogenic material, or may be coated with a thrombogenic material in order to aid in the clot retrieval procedure, by promoting adhesion between the engaging member and the thrombus. Alternatively, an anti-thrombogenic material can be used, or an anti-thrombogenic coasting can be used in order to help dissolve a portion of the clot that is in contact with the engaging members. This can be useful with, for instance, retrieval operations involving a large clot. 
       FIGS. 7 and 8  illustrate another embodiment of the obstruction removal device utilizing one or more engaging members which act as a filter in order to catch thrombus that may become dislodged during the clot removal procedure.  FIG. 7  illustrates the obstruction removal device, with a proximal portion  401  and distal portion  402 . The proximal portion includes engaging members  303 . The distal portion includes engaging members  407  and  408 . The distal engaging members  407  and  408  have a denser cell configuration to act as a filter to trap dislodged thrombus which may shear off during the clot removal procedure, the clot removal procedure being generally described above. The denser cell configuration is due to an inner and outer structure used to form the engaging member, as illustrated in  FIG. 8 . 
     As illustrated in  FIG. 8 , the two distal engaging members  407  and  408  are each composed of an inner structure  409  and outer structure  410 , where the inner structure may nest within the outer structure. The inner structure  409  and outer structure  410  which comprise the distal engaging members  407  and  408  may be made from laser cut nitinol, or a similar material. The proximal portion  401  and distal portion  402  are configured the same as the embodiment presented in  FIGS. 4-5 , as are the linkages between each of the engaging members, although this filtering engaging member structure can be applied to any of the engaging members presented in any of the presented obstruction removal device embodiments. 
     The cell pattern may be slightly offset on the inner and outer structure in order to create a denser cell profile when the inner structure is nested within the outer structure. As shown in  FIG. 9 , the distal part  510  of the engaging member  408  has a denser cell profile than the proximal part  511  in order to catch dislocated thrombus which may escape during the clot removal procedure. This arrangement can be useful when the more proximal engaging members interact with the clot and portions of the clot macerate. The more distal engaging members with the filter configuration can catch macerated thrombus that otherwise might accumulate in the bloodstream. Although  FIGS. 7 and 8  illustrate two engaging members having the inner and outer structure to act as a filter, more or fewer engaging members can have this filter structure. 
     In one embodiment for delivery of the device described in the previous embodiments, an obstruction removal device is sheathed within a delivery device, and the delivery device is delivered through a catheter. In one example, the delivery device can be a microcatheter. The delivery device is delivered to the site of the obstruction and then pulled back. Pulling back the delivery device unsheathes the obstruction removal device, such that the engaging members expand upon retraction of the delivery device. 
     Alternatively, the obstruction removal device is pushed out of the delivery device, which subsequently allows the engaging members to expand. Depending on the number of engaging members on the obstruction removal device, the size of the clot, and the location of delivery relative to the obstruction, some members may sit distally past, and/or proximally before, the obstruction. The obstruction removal device may be maneuverable via the core wire. Once the obstruction removal device engages the obstruction, the delivery device can be withdrawn to a point just past the distal end of the catheter, and then the catheter can be withdrawn. Alternatively, the obstruction removal device can be withdrawn from the vasculature by withdrawing the delivery device into the catheter, and subsequently withdrawing the catheter, or withdrawing the delivery device and/or obstruction removal device through the catheter. Alternatively, the catheter can be withdrawn wholly to remove the delivery device and obstruction removal device. In another example, the delivery device can be a hypotube. 
     In an alternative embodiment, the device may be delivered directly through the catheter, without being sheathed in a delivery device. 
       FIGS. 10-12  illustrate an example of a particular method for deploying the obstruction removal device. In this example, the delivery device  602  is delivered through the vasculature  600  to the site of the clot  601 . The obstruction removal device  603  is pushed through the delivery device to the site of the clot. Although this particular example illustrates the obstruction removal device deployed in the middle of the clot, the device may be deployed within the clot, or in a location proximal or distal relative to the clot location. Some engaging members may sit distally past and/or proximally before the clot, depending on the size of the clot and the number of engaging members used on the obstruction removal device. Delivery device  602  is then retracted which allows the engaging members of the obstruction removal device to expand and interact with portions of the clot. The obstruction removal device  603  can be manipulated by the operator from the proximal portion  604  of the device. Once the obstruction removal device has secured the clot, the device can be withdrawn as described above. Aspiration may also be used to aid in the clot/obstruction removal procedure.  FIGS. 10-12  illustrate a particular example for illustrative purposes. Other delivery methods are contemplated within the scope of the invention, such as pushing the obstruction removal device from the delivery device. 
     The engaging members may all be the same size, may all be different sizes, or may have some engaging members sized differently from others. In one example, the diameter range for spherically shaped engaging members may be between 1-12 millimeters. In another example, a diameter range of 3-6 millimeters is used. 
     The engaging members are formed from a hypotube which is laser-cut into a particular pattern based on the shape of the struts  101  and cells  102 . This hypotube  700  is shown in  FIG. 13 . The hypotube is heat treated, in one example the hypotube can be heat set at 530-550 degrees Celsius for 5 minutes. The hypotube is subsequently quenched in water to cool. An expansion plunger  702  is then inserted and used to expand a portion of the hypotube (see  FIG. 14 ). The expanded hypotube is then heat-set to this expanded shape. In one example, it is heat set at 530-550 degrees Celsius for 3 minutes. The expanded hypotube is subsequently quenched in water. Based on the size of the engaging member, the expansion plunger and subsequent heat treatment step can be used on multiple portions of the engaging member, where each section is heat set after expansion. An expansion pin  704  is subsequently inserted within the hypotube to help expand the walls of the hypotube (see  FIG. 15 ). The expanded hypotube  700  is placed in a fixture. The fixture includes two plates  706 ,  708 . Threaded rods connect the plates, and the plates have an external mounted nut. The nut can be tightened to compress the plates together in order to further expand the hypotube. Once the appropriate shape is set, the expanded hypotube can be heat treated (in one example, heat treated at 530-550 degrees Celsius for 5 minutes) and quenched to set the shape of the engaging member. 
     The engaging members are subsequently pickled, etched, and electropolished to set the final shape of the said members. The obstruction removal device is then assembled together with the one or more engaging members. Though the engaging members are heat-set and treated into an expanded shape, they still retain a high degree of shape memory due to factors such as material properties and strut thickness. Thus, the engaging members will adopt an expanded shape when not restrained (i.e. not sheathed in a delivery device) and will adopt a contracted shape similar to the initial hypotube shape when restrained (i.e. sheathed in a delivery device). 
     The previous embodiments generally disclosed engaging members in which all of the struts span the length of the engaging members. Alternative embodiments can utilize some struts that do not span the length of the engaging members. For instance, those partially-extending struts can extend only along a proximal end of the engaging member and vary in length relative to each other. These partially-extending struts can help augment clot retention capability of the overall obstruction removal device. 
     Please note, for the sake of the embodiments presented in  FIGS. 17-18   d , unless otherwise indicated, anything on the left side of the figures would be considered proximal or in the direction of where vascular access was obtained while anything on the right side of the figures would be considered distal or in the direction of further placement within the vasculature. 
       FIGS. 17, 18   a ,  18   b ,  18   c , and  18   d  illustrate one example embodiment of an obstruction removal device  800  where some struts (e.g., struts  801 ) connect at proximal and distal ends of the engaging members  812  and other struts (e.g., struts  810 ) only connect at one end of the engaging members  812 , leaving their other end unconnected/freely floating. 
     This strut configuration can be seen best in the side view of  FIG. 18 a   , the proximal end view of  FIG. 18 b   , and the distal end view of  FIG. 18 c   . Specifically, the proximal and distal ends of the engaging members  812  have a plurality of smaller struts  805 ,  807  that generally form a plurality of “flowering” or inclining diamond or loop shapes. These diamond or loop shapes are formed of a number of inner struts  805  that are connected to form a from proximal or distal aperture/hole  800   a / 800   b  and a number of outer struts  807  connected to these inner struts. For example, the proximal end of the engaging member  812  includes five diamond shapes  803   a  and the distal end includes three diamond shapes  803   b . Put another way, the proximal end of the engaging member  812  includes five primary or inner struts  805  radially extending from a distal end of the engaging member. Each of those struts split into a “Y” shape of secondary or outer struts  807 , with the distal ends of each secondary struts  807  merging together with adjacent secondary struts  807  from a different, adjacent primary strut  805 . 
     The five proximal diamond shapes  803   a  connect to either a lateral strut  801  that spans between the distal diamond shapes  803   b , or a partial lateral strut  810  that does not span the full length to the distal diamond shapes. As shown in  FIG. 18 a   , some struts can also terminate right where outer struts  807  merge—shown as smaller retained lateral strut  809 . In this way, some struts  801  span between the proximal diamonds  803   a  and distal diamonds  803   b , and some do not. 
     This configuration can be made in various ways. In one method, the struts are formed from the hypotube in  FIG. 13 , which is used to create the engaging member strut shapes shown, for example, in  FIGS. 7-9 . Once the engaging member is expanded to take on its full shape, some of the struts are then cut to create the shape shown in  FIGS. 17-18 . In another method, the hypotube itself which is used to create the engaging member may have cut-out strut sections so that the finalized engaging member takes on the shape shown in  FIGS. 17-18   d.    
     In one embodiment, one end of the engaging member  812  can have a larger retained strut-section (i.e., more “diamond” shapes) than the other end—as shown in  FIGS. 17-18   d . In  FIGS. 17-18   d , the left side  802  of the engaging member  812  (also known as the proximal side of the engaging member, since the pusher is connected to the left-most engaging member for the purposes of the figures) has a larger number of struts  805 ,  807  than the right (or distal) side  804  of the engaging member  812 . As best seen in  FIGS. 18 a  and 18 d   , this configuration can be made by cutting a preformed lateral strut  801  near the point they would normally merge into secondary struts  807 . On the other side of the engaging member  812 , the strut pairs can be cut at an earlier termination point leaving one end with a larger retained partial lateral strut  810  and the other end with a smaller retained lateral strut  809 . This configuration further enables better proximal gripping of the clot as the device is retracted into the larger guide or access catheter  817  to evacuate the device after clot retrieval is accomplished. 
     In other embodiments, the distal end of the engaging member  812  is attached to the larger retained partial lateral strut  810 . This configuration creates a distal net structure to help ensure the ensnared clot does not travel distally during the clot capture procedure. Alternatively, the individual engaging members can be customized such that some engaging members have a larger proximally-retained strut sections, while other engaging members have larger distally-retained strut sections. In one example, a clot retrieval device can utilize a proximal-most engaging member with a larger proximally-retained strut section and a distal-most engaging member with a larger distally-retained strut section. This configuration would balance the benefits between augmenting clot retention during retraction through a catheter, while further minimizing the risk of distal clot migration during the clot retrieval procedure. 
     As best shown in  FIGS. 18 a  and 18 d   , the retained partial lateral struts  809 ,  810  terminate with a marker coil  808 . The marker coil  808  is separately shown in  FIG. 19  and has a diameter or thickness that is greater than the partial lateral struts  809 ,  810 . The marker coil  808  is used to aid in imaging the clot retrieval device and note the location of the engaging members and whether said engaging members are in an expanded or collapsed shape. The marker coils  801  can be composed of a variety of radiopaque materials including gold, platinum, tantalum, tungsten, or palladium. Additionally, the marker coil can take on a variety of configurations including a braid, band, or tube. In one example, the marker coil  808  is connected onto the struts by using UV glue in the internal diameter of the marker.  FIG. 18 d    shows rounded/ball-like projections  808   a ,  808   b  on the proximal and distal ends of the marker band. In one embodiment, UV glue or laser welding is used in order to create these ball elements which create a secure locking interface between the struts and the marker coil. The marker coil  808  and ball-like projections also provide a larger contact surface interface than the end of the strut sections (as shown in  FIG. 18 d   ) and provide a larger contacting surface to help engage and retain the clot. Note, the marker coil  808  can alternately be located on the lateral strut  801  at a location adjacent to termination of either partial lateral strut  809  or  810 . 
     Please note, though the embodiments of  FIGS. 17-18   d  show individual linkages between each pair of engaging members (similar to the embodiments of  FIGS. 4-8 ), the engaging members may alternatively sit along a common structure (similar to the embodiment of  FIG. 3 ). 
     The following embodiments related to obstruction removal devices in which the engaging members strut shapes are configured to help shear thrombus or clot from a vessel wall and can be useful in scenarios involving calcified thrombus. 
     Earlier embodiments of engaging members, such as those shown in  FIGS. 1-9 , utilize struts  101  comprising a lengthy strut section  101   c  which spans the majority of the length of each engaging member. These struts are aligned in a generally longitudinal orientation in the blood vessel wall thereby mitigating the risk of the struts shearing off the vessel wall surface and damaging the vessel when pushed or pulled. However, in some circumstances it may be desirable to have an obstruction removal device that has higher shearing force; for example, in situations involving calcified thrombus or clot attached to the vessel wall in which it a large amount of force is necessary to remove or scrape the clot or thrombus from the vessel wall. An engaging member utilizing twisted lateral strut elements rather than straight strut elements would provide this higher shearing force. 
     The engaging member  813  shown in  FIG. 20  utilizes several lateral strut elements  811  that are not longitudinally aligned between the proximal and distal ends of the member  813 , but rather are aligned at an angle (e.g., 1-89 degrees, for instance 45 degrees) relative to a proximal-distal axis of the member  813 . This contrasts with the more axially-longitudinal or “straight” strut elements  101   c  shown in  FIGS. 1-9 . These twisted lateral strut elements  811  create greater surface contact between their edges and the vessel wall or clot when pushed or pulled. In this respect, the lateral strut elements  811  can better scrape the vessel walls to remove hard or calcified clot/thrombus which may be attached to the vessel wall. In several embodiments, the engaging members are capable of rotation and independent rotation, so as the engaging members rotate, different parts of the strut contact the vessel further augmenting the scraping effect against clot/thrombus. 
       FIG. 21  shows a hypotube shape (shown flattened for illustrative purposes) with twisted lateral strut elements  811  in the middle which correspond to the twisted strut elements of the engaging member. In one embodiment, a tube is laser-cut to create the strut shapes of  FIG. 21 . In one embodiment, a flat sheet is laser-cut to create the strut shapes shown in  FIG. 21 , then the sheet is rolled around a mandrel and the two ends of the sheet are welded together to create the circular engaging member shape of  FIG. 20 . Compared to the hypotube of  FIG. 13  which utilizes substantially straight primary straight sections  101   c  (i.e., those struts that run the majority of the length of the engaging element), the hypotube of  FIG. 21  utilizes angled strut elements  811  to create the twisted/angled configuration of  FIG. 20 . While in  FIG. 13 , strut elements  101   d  and  101   c  sit along the same plane, in  FIGS. 20-21 , strut elements  811  are angled and do not sit along the same plane as merging strut pairs  801   d.    
     Other embodiments of an obstruction removal device can utilize multiple engaging members which sandwich the clot from either side to engage and retain the clot. Please note for the following figures, unless indicated otherwise, anything to the left would be considered distal or in the direction further downstream within the vasculature while anything to the right is considered proximal or in the direction where vascular access is gained.  FIGS. 22-25  show this obstruction removal device  900 , which utilizes a distal fixed clot disruptor structure  908  which is located distal to a clot  910  and a proximal sliding clot catcher structure  906  which is positioned proximal to the clot  910 . The two structures  906 ,  908  are connected on a distal portion  902  of a pusher or core wire  901 . The distal clot disruptor  908  is fixed or bonded to the distal portion  902  of the core wire  901  and the proximal clot catcher structure  906  can slide along the distal portion  902  of core wire  901 , but is prevented (e.g., via a radially enlarged stop portion) from sliding along the entirety of core wire  901 . This sliding can be enabled in a number of ways, for instance in one embodiment, one end  906   a  of proximal clot catcher structure  906  can be connected to a sleeve or band which is positioned over and can slide relative to the core wire&#39;s distal portion  902 . 
     Various methods can be used to limit the amount that proximal clot catcher structure  906  can slide. In one embodiment, a proximal and/or distal stop  906   a  can project out from the core wire&#39;s distal portion  902  in order to limit the amount that the proximal clot catcher structure  906  can slide. A proximal stop limits the amount the clot catcher structure  906  slides proximally, a distal stop limits the amount the clot catcher structure  906  slides distally. In another embodiment, no stop structure is present, however the proximal clot catcher structure  906  can slide freely solely over core wire&#39;s distal portion  902 . This can be accomplished if the core wire&#39;s distal portion  902  is smaller than the remaining proximal portion of core wire  901  such that the sliding catcher structure  906  has enough clearance to slide over distal core wire section  902  but not the rest of core wire  901 , since said core wire  901  will be oversized compared to distal core wire section  902 . 
     The method of use of the obstruction removal device embodiment  900  of  FIG. 22  is described as follows. The physician typically uses a larger guide or access catheter as a sheath for a smaller microcatheter  912  which contains the obstruction removal device  900 . The physician advances the microcatheter  912  in the vessel  904  and through clot  910  and then retracts the microcatheter  912  to expose the clot/obstruction retrieval device  900 , such that the distal disruptor structure  908  is located distal to clot  910 . The physician then pulls core wire  901 , which causes the distal disruptor structure  908  to engage and push against clot  910 . Proximal catcher structure  906 —which has a degree of sliding movement but is proximally limited in its movement (as discussed above)—may move proximally once it contacts clot  910  but will fully engage the clot once stopped, as shown in  FIG. 23 . Once the clot  910  is retained by the obstruction removal device  900 , the physician can retract core wire/pusher  901  so that the removal device  900  is sheathed inside a larger guide or access catheter  914  and then the whole system is removed from the patient vasculature. 
     The proximal clot catch structure  906  and distal clot disruptor  908  can take on various shapes or designs. One embodiment of an obstruction removal device  900  is illustrated in  FIG. 22  in which the distal clot disruptor  908  is shaped like the engaging member of  FIGS. 1-2 ; however, other embodiments can utilize a distal clot disruptor  908  shaped like any of the engaging members shown and described in other engaging member embodiments presented. In one embodiment, proximal clot catch structure  906  is a mesh of braided wires and the proximal end of catch structure  906  is closed but slidable over the core wire while the other end  906   b  is open to accommodate clot  910 . In other embodiments, proximal clot catch structure  906  is a polymeric structure or even a stent where the proximal end of the stent is secured via a retention means (e.g., a marker band) over the core wire in a slidable manner while the other end of the stent is flared or open to accommodate clot  910 . Mesh and polymeric stents are described in US20130245745 which is hereby incorporated by reference in its entirety and the proximal clot structure can be one of the stents described therein. 
     In another embodiment of an obstruction removal device  915 , a mesh or polymeric stent, including those previously incorporated by reference are used for the distal clot disruptor  908 , in which the proximal end of the stent is bonded to the core wire  902 —as shown in  FIG. 24 . In another embodiment, the proximal clot catch structure  906  takes on the configuration of a vessel filter or embolic protection device (EPD). EPD&#39;s are often placed downstream of a stent or balloon in a procedure to open a clogged blood vessel, where the EPD is dispatched downstream prior to the stent or balloon placement in order to catch thrombus dislodged during the procedure. Generally a distal end of the EPD/filter would be bonded to or over the core wire  902  while the proximal end is an open mouth, since the EPD/filter is placed distal to the treatment site. Here, if an EPD/filter is used for the proximal clot catch structure  906 , the proximal rather than distal end of the EPD/filter is bonded in a slidable manner over the core wire since the distal mouth of the filter should be open to help entrap the clot. EPD/vessel filters are described in US2014/0288588, which is hereby incorporated by reference in its entirety. Any of the EPD/vessel filters described therein could be used for proximal catch structure  906 . 
       FIG. 25  shows an embodiment of an obstruction removal device  921  utilizing multiple members along a core wire. An obstruction removal device  921  with multiple members capable of engaging the clot is useful to remove larger clots, or a clot which is hardened or calcified and would be otherwise difficult to remove. In this example, there are two clot catcher structures  916   a ,  916   b  and two clot disruptor structures  918   a ,  918   b  placed in an alternating manner (e.g. from proximal to distal: a proximal clot catcher  916   a , then a first clot disruptor  918   a , then a second clot catcher  916   b , then finally a distal-most second clot disruptor  918   b ). In one example, the proximal clot catcher  916   a  is slidable, the first clot disruptor  918   a  is fixed or has a limited degree of movement, the second clot catcher  916   b  is slidable, and the distal-most second clot disruptor  918   b  is fixed. 
     For embodiments where first clot disruptor  918   a  is capable of some limited degree of motion, there are several ways to allow this. In one example, the proximal and distal ends of the first clot disruptor that sit over the core wire distal section  902  are oversized and the core wire distal section  902  can have built in enlargements so that the first clot disruptor ends will hit the enlargements to limit movement in either direction. In another example shown in  FIG. 25 , the core wire distal section  902  is segmented rather than continuous. A first leg  902   a  of the core wire distal section  902  terminates in a ball or enlarged projection  920  within the first clot disruptor structure  918   a . A second leg  902   b  spans between first clot disruptor  918   a  and second clot disruptor  918   b  and terminates in a ball or enlarged protection  920  within said second clot disruptor  918   b . The enlargements  920  limit the movement of each clot disruptor since the clot disruptors cannot move once the proximal or distal ends of the clot disruptors contact the enlargements. This functions like the obstruction removal device of  FIGS. 4-6 , in which engaging members are separated by individual links  313  with flared ends which limit translation of the engaging members. Please note, even in the absence of any structures limiting movement of the various objects on the core wire, the structures are already limited in movement since each structure cannot move past the neighboring structure. For example, the proximal clot catch  916   a  can move but the end that slides over the core wire cannot move past the proximal end of the first clot disruptor  918   a.    
     Various versions of the embodiment of  FIG. 25  could utilize more clot disruptors and/or more clot catcher structures, or different combinations of clot disruptors and clot catcher structures. The segmented core wire system described above, the single core wire enlargement section described above, or combinations of these two systems can be used to allow limited movement of the various structures on the obstruction removal device. 
     Many of the obstruction removal device embodiments presented thus far have utilized engaging members which are capable of independent rotation. Referring to  FIG. 26  (which offers another view of the linkage elements originally shown in  FIGS. 5-6  connecting the engaging elements), this is possible by utilizing a linkage  1013  between pairs of engaging members. Linkage  1013  includes two flared ends  1003  (e.g., enlarged spherical regions) and a retaining piece  1012  (e.g., a cylinder or sleeve) which operate to limit translation of the engaging elements while allowing said engaging elements to rotate independently of each other. Two marker bands  1012   a  can also optionally be placed at either end of the gap  1015   a  between the engaging elements to further aid in imaging. The marker bands  1012   a  will also minimize this gap  1015   a  which could potentially be a region where thrombus becomes trapped and later be sheared away since the small gap results in a small retaining force. Though the engaging members  1003  are generally capable of independent rotation, in scenarios where the engaging members are deployed in tortuous anatomy or are far oversized compared to the blood vessel, the engaging members can become stuck in a particular orientation limiting their ability to rotate. This rotation is generally advantageous since it allows the engaging elements to self-adjust to the condition of the vessel which maximizes the chances of clot contact and retention. 
       FIG. 27  illustrates an embodiment of an obstruction removal device  1050  that addresses some of these issues. The device  1050  includes a series of engaging members  1052   a - 1052   e  (five are shown, but more engaging members or less engaging members could be used), where each engaging member is rotationally fixed in a particular orientation. Each engaging member has substantially the same strut pattern, however each engaging member is offset a certain number of degrees (i.e. rotated a particular number of degrees) from its neighboring engaging member  1052  and each engaging member is fixed and therefore incapable of independent rotation. As the entire obstruction removal device  1050  is pushed or pulled within a vessel, the fixed, offset arrangement of the engaging members  1052  ensure that all interior surfaces of the vessel are contacted by a strut of the engaging members  1052 . In other words, if all of the engaging members  1052  where aligned in the same rotational orientation, linear gaps of the vessel&#39;s interior may not be contacted by the engaging members  1052 . Hence, the rotational offset configuration helps mitigate this issue, particularly for larger clots that may span several engaging members. 
       FIG. 28 a    shows one example involving a rare situation in which each engaging member is capable of independent rotation but some of the engaging members are stuck in the same or similar rotational orientation (for example, where the engaging members are deployed in a tortuous section of the vessel or are far oversized compared to the vessel and thereby stuck in one orientation). This figure offers a cross-sectional view from an end of one of the engaging members. Each end of each engaging member  1052  has a flowered petal bulb-type shape similar to the one shown in  FIG. 1 , the strut pairs merge into a lengthier strut which spans the majority of the engaging member  1052 , and this lengthier strut then diverges into additional strut pairs at the other end of the engaging element and this flowered-type shape is repeated. Here, clot  406  is lodged against a particular section of the vessel wall  1068 , but the struts  1064  of two or more neighboring engaging members are stuck in a similar position preventing the clot  1066  from being contacted by struts  1064 . Conversely, in  FIG. 28 b   , the fixed but offset strut orientation offers greater cross-sectional strut coverage around the periphery of the blood vessel  1068 , which enhances the chances that the clot  406  is contacted. 
     Since the engaging members  10522   a - 10522   e  are fixed, the rotatable linking structure of  FIG. 26 , which includes gap  1015   a , is not needed. In various embodiments, the engaging members can all be welded together or formed from one hypotube which is laser cut into the shape shown in  FIG. 27 . Either configuration will reduce or eliminate the gap between the engaging members which could potentially augment thrombus retention since this gap region potentially represents a region where thrombus could get temporarily stuck but later break free. The engaging members can also be placed over an open tubular lumen which spans all of the engaging members. This open tubular lumen can be used as a conduit for additional devices, including vessel filters placed downstream of the obstruction removal device to catch dislodged thrombus and/or guidewires used to aid in navigating the placement of the obstruction removal device. This design is also considerably simpler than the rotating engaging element embodiments since the paired linkage configurations are omitted. 
     In various examples, five engaging members are used and each engaging member is offset about 36 degrees from the next engaging member. Another example can utilize five engaging members offset about 18 degrees from the next engaging member. Other examples can utilize more or less engaging members with various degrees (e.g., from one degree to 359 degrees) of offset, the offset helps ensure a relatively broad cross section of the vessel will be exposed to at least one strut to aid in contacting the clot, thereby augmenting clot contact and clot retention. In other examples, some engaging members can be offset whereas other engaging members are not offset. In other examples, different offsets can be used between different engaging members (e.g. one pair offset by 20 degrees, another pair offset by 25 degrees). 
     Various embodiments of the obstruction removal device, including various embodiments of the engaging elements comprising the obstruction removal device were presented in the specification herein. Please note, different versions of the obstruction removal device can utilize various engaging element shapes/configurations of different embodiments. By means of example, for the partially spanning strut engaging element configuration of  FIG. 18 , the engaging elements can utilize the twisted strut configuration of  FIG. 20 —alternatively some engaging elements can utilize a twisted strut configuration while others utilize the partially spanning strut configuration. Similarly, for the sliding embodiments of  FIGS. 22-25 , either the catch structures  906  or disruptor structures  908  can utilize partially spanning strut configurations and/or twisted strut configurations presented in various other embodiments. Similarly, in various embodiments (including the partially spanning strut configuration of  FIG. 18 , the twisted strut configuration of  FIG. 20 , or the sliding embodiments of  FIGS. 22-25 ) some or all of the engaging members can be fixed but offset from other engaging members as shown in  FIGS. 27-28   b.    
     In an alternative embodiment, the device mentioned in the previous embodiments can be used to retrieve foreign objects, in addition to clots or other obstructions. Circumstances may arise where foreign objects, such as embolic coils normally used to fill an aneurysm, may break off or otherwise become detached within the vasculature. The device can be used to retrieve the foreign body utilizing a procedure similar to the procedure used during obstruction removal. 
       FIG. 29  illustrates and embodiment of an engaging member  1070  that, instead of being laser cut, is made from NiTi/Platinum drawn filled tube wires. These wires allow the engaging member  1070  to be fully radiopaque under fluoroscopy and therefore allow the physician to better place and control the device during a thrombectomy procedure. The engaging member  1070  is illustrated with primary struts  1075 , secondary struts  1077  and lateral struts  1071 , similar to previous embodiments; through any of the previous shapes/configurations can be used with these drawn filled tubes. Preferably, each of these struts are formed of individual drawn filled tube wires that are twisted together, for example at location  1079  to connect to adjacent struts. The proximal and distal ends of the engaging member  1070  can be laser welded to marker bands. 
       FIG. 30  illustrates an engaging member  1079  in which half of the struts  805 ,  807 , and  801  are formed via laser cutting a metal sheet/tube, and the other half is formed of struts  1072 ,  1075 ,  1077 , and  1078  of drawn filled tube wires. Preferably, the drawn filled tube wires are positioned on the distal end of the engaging member  1079  and the laser cut struts are positioned on the proximal end. The laser cut portion can provide a relatively higher radial expansion force while the drawn filled tube wires can allow for a greater number of wires to be used and therefore can increase the filtering capability of the device. Optionally, the drawn filled tube wires can be laser welded to the laser cut portion. 
       FIG. 31  illustrates another embodiment of an engaging member  1080  having a plurality of drawn filled tube wires  1075 ,  1077 ,  1078  on its proximal half in a configuration similar to those previously described, but also includes a distal half  1082  configured as a concave filter. The distal half  1082  is preferably formed of a plurality of drawn filled tube wires that are braded into the concave shape and welded to the larger drawn filled tube wires on the proximal half. In this respect, the distal half can act as a relatively fine filter and the proximal portion can provide the strength to radially expand the distal portion. 
     During a thrombectomy procedure, the previously described embodiments often much be moved around bends or curves within vessel, which can cause the engaging members to compress, as they seek out the shortest distance around the curves. This compression of the engaging members can cause the clot to dislodge and therefore be lost. The engaging member  1093  shown in  FIGS. 32 and 33  address this issue by having a radially offset shape with a relatively straight/flat side  1093  and a relatively curved side  1098 , all formed from struts  1095 ,  1097 , and  1098 . As seen in  FIG. 33 , as the offset engaging members  1093  are pulled around the curved vessel, their straight/flat side  1093  finds the shortest distance around the curve while the curved portion  1098  remains fully expanded. 
       FIG. 34  illustrates another embodiment of a clot retrieval device  1100  having a proximal and distal “flowering petal” engaging members  1101  that re both connected to a delivery wire  1106 . Similar to previously described embodiments, each engaging member  1101  are composed of a plurality of primary struts  1115  and secondary struts  1117 , forming a plurality of connected diamond or loop shapes  1116  (e.g.,  5  diamond shapes). The diamond shapes  1116  are included or are opened along a distal direction, forming a distally open cup or concave shape that can capture a clot  910 . Each of the diamond shapes can include a radiopaque marker  1103  on its distal tip for use in determining their position during a procedure. Each engaging member  1101  can be fixed in place to the wire  1106 , slideable on the wires  1106 , or a combination of both (e.g., similar to the embodiment of  FIG. 22 ). Preferably, the device  1100  is deployed during a procedure so that one engaging member  1101  is proximal to the clot  910  and the other engaging member  1101  is distal to the clot  910 , trapping the clot  910 . Alternately, the engaging members  1101  can open in the proximal direction or a combination of both (e.g., the proximal engaging member  1101  opens in the distal direction and the distal engaging member  1101  opens in the proximal direction). Additionally, more than two engaging members  1101  are also contemplated (e.g., 3, 4, 5, 6, 7, and 8). 
     Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.