Abstract:
The devices and methods described herein relate to clearing of blockages within body lumens, such as the vasculature, by addressing the frictional resistance on the obstruction prior to attempting to translate and/or mobilize the obstruction within the body lumen.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 11/684,546 filed Mar. 9, 2007, which is a continuation of U.S. application Ser. No. 11/671,450 filed Feb. 5, 2007, now abandoned, which is a non-provisional of U.S. Provisional Application No. 60/765,496 filed Feb. 3, 2006, each of which are incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The devices and methods described herein relate to clearing of blockages within body lumens, such as the vasculature, by addressing the frictional resistance on the obstruction prior to attempting to translate the obstruction within the body lumen. In one variation, the devices and methods described below may treat conditions of ischemic stroke by remove blockages within arteries leading to the brain. Accordingly, variations of such methods and devices must navigate tortuous anatomy and vasculature without causing unacceptable damage to the anatomy. Also, the devices and methods first secure and surround the obstruction (such as a clot) prior to significantly moving the clot within the anatomy. 
       BACKGROUND OF THE INVENTION 
       [0003]    Ischemic stroke occurs when a blockage in an artery leading to the brain causes a lack of supply of oxygen and nutrients to the brain tissue. The brain relies on its arteries to supply oxygenated blood from the heart and lungs. The blood returning from the brain carries carbon dioxide and cellular waste. Blockages that interfere with this supply eventually cause the brain tissue to stop functioning. If the disruption in supply occurs for a sufficient amount of time, the continued lack of nutrients and oxygen causes irreversible cell death (infarction). Accordingly, immediate medical treatment of an ischemic stroke is critical for the recovery of a patient. 
         [0004]    The infarction may not develop or may be greatly limited, given a rapid clearing of the blockage to reestablish the flow of blood. However, if left untreated, ischemic stroke may lead to the permanent loss of brain tissue, and can be marked by full or partial paralysis, loss of motor control, memory loss, or death. 
         [0005]    Several different diseases may lead to an ischemic stroke. Typically, deposition of cholesterol (artheroselerosis), formation of blood clots, or other objects in the vessels may disrupt blood flow and lead to ischemic stroke. Furthermore, the substances that cause the blockages may break free from larger vessels outside the brain and become lodged within narrower arteries closer to the brain embolism). 
         [0006]    Ischemic stroke may be divided into thrombotic strokes and embolic strokes. A thrombotic stroke occurs when the building and rupturing of atheromatous plaque within the brain blocks cerebral arteries. Clinically referred to as cerebral thrombosis or cerebral infarction, this condition represents approximately 10% of all strokes. An embolic stroke occurs when a clot or emboli forms somewhere other than in the brain, such as in the cervical carotid artery or in the heart, and travels in the bloodstream until the clot becomes lodged and can not travel any further. When such a condition occurs in the arteries supplying the brain, the condition results in almost immediate physical and neurological effects. 
         [0007]    While these are the most common causes of ischemic stroke, there are many other possible causes. Examples include use of drugs, trauma to the blood vessels of the neck, or blood clotting disorders. 
         [0008]    Apart from surgical techniques, medical practitioners could address such blockages with the use of Tissue Plasminogen Activator (t-PA). However, t-PA must be used within the first three hours of the onset of stroke symptoms and may take hours or even days to successfully restore flow. In addition, t-PA carries an increased risk of intracerebral hemorrhage. It is currently believed that the use of t-PA results in a 30% success rate as well as a 6% major complication rate. In view of these limitations, the majority of stroke patients in the U.S. do not receive t-PA treatment. 
         [0009]    In addition, there are a number of surgical techniques used to remove blockages. For example, an embolectomy, involves incising a blood vessel and introducing a balloon tipped device (such as the Fogarty catheter) to the location of the occlusion. The balloon is then inflated at a point beyond the clot and used to translate the obstructing material back to the point of incision. The obstructing material is then removed by the surgeon. Concentric Medical, Inc. of Mountain View, Calif. supplies devices for an interventional approach to the removal of obstructions. Concentric supplies a Merci® Retriever system as a device based approach for the removal of clots. This system engages and ensnares a clot. Once captured, a balloon catheter inflates to temporarily halt forward blood flow while the clot is withdrawn. The clot, is then pulled into the catheter and out of the body. 
         [0010]    Typically, the existing means to remove obstructions do not address the frictional forces that act on the obstruction during removal of the obstruction. For example, some conventional devices engage the clot from the distal (or downstream) side. As the device is pulled proximally (or upstream), the device attempts to either engulf or ensnare the clot. However, due to the consistency of the clot and because the clot is typically well lodged, within the vessel, the act of pulling, the clot in a proximal direction cause the clot to also compress in an axial direction. This axial compression (when viewed along the axis of the vessel) causes a contemporaneous radial expansion of the clot (when viewed relative to the vessel). As a result, the increase in diameter of the clot causes an increase in the frictional forces applied against the arterial wall. Thus, by not addressing the frictional forces acting on the obstruction, the process of removing the clot may actually increase the static force that would otherwise be required to remove or translate the clot within the vessel. Unfortunately, increasing the amount of force applied upon one side of the clot also increases the probability of complications during the procedure (e.g., fragmenting the clot, failing to remove the clot, failure to fully engulf/ensnare the clot, and/or device failure) and can cause potential damage to the surrounding vessel. 
         [0011]    While there are other drugs and suppliers of devices for removal of blockages, there remains a need for methods and devices that improve the success rate and/or reduce the complication rate in restoring flow and thereby limit the damage from an ischemic stroke. 
       SUMMARY OF THE INVENTION 
       [0012]    It should be noted that the present methods and devices may be used to treat blockages leading to ischemic stroke as well as to treat blockages (caused by “obstructions”) within other parts of the body (i.e., unless specifically noted, the devices and methods are not simply limited to the cerebral vasculature). The term obstructions may include blood clot, plaque, cholesterol, thrombus, naturally occurring, foreign bodies (i.e., a part of the body that is lodged within the lumen), a non-naturally occurring foreign body (i.e., a portion of a medical device or other non-naturally occurring substance lodged within the lumen.) 
         [0013]    In one variation of the devices described herein, the device allows for surrounding the obstruction prior to attempting to translate or move the obstruction within the vessel. It should be noted that although minimal axial movement of the obstruction may take place, the device surrounds the obstruction before such movement causes significant distortion to the geometry of the obstruction resulting in an increase in the static force required to remove the obstruction from the vessel. 
         [0014]    In another variation of the device, the device may include a low friction mode (such as a set of parallel wires, or wires extending axially along the lumen or vessel) that converts to an increased friction mode (such as a compressed set of wires acting on the obstruction or a twisted set of wires acting on the obstruction). The increase in friction is an increase in the friction between the obstruction and the device (as opposed to the vessel wall. In some cases, the low friction modes is a low surface area mode and the high friction mode is a high surface area mode. When configured in the low friction mode, the device is better suited to engage the obstruction without the undesirable effect of prematurely mobilizing the obstruction or compacting the obstruction (e.g., when wires are slid across the obstruction in a transverse motion). Upon engaging the obstruction, the device will conform to a high friction mode with respect to the obstruction (in some cases the device will have an increased surface area mode). This high friction mode permits the device to better grip the obstruction for ultimate removal of the obstruction. 
         [0015]    The operation of the devices and method described herein secure the obstruction, overcome the elastic forces of the obstruction, then remove the obstruction from the anatomy without losing or fractionating the obstruction. In one variation of the invention, this is accomplished by the obstruction removal device interacting with the obstruction in the following manner: (1) the traversing filaments traverse the obstruction by passing either through the obstruction or between the obstruction and the vascular wall; (2) the traversing portion is pulled proximally to engage the surrounding portion of the device around the obstruction, the surrounding portion engaging the obstruction without causing significant mobilization of the obstruction; (3) the obstruction removal device is pulled further proximally and the surrounding portion now mobilizes the obstruction. 
         [0016]    As shown below, variations of the devices have a configuration that provides a path for a portion of the device to surround the obstruction. The paths are made using traversing filaments that allow for low frictional translation of a surrounding portion of the device over the obstruction without causing axial translation of the obstruction. This mechanism is described in more detail below. 
         [0017]    Once in the proper position, a portion of the device (e.g., a surrounding portion) increases the frictional contact with the obstruction to disperse the pulling force more evenly across the obstruction. The increase points of contact allow for removal of the obstruction through tortuous anatomy while ensuring that the obstruction will not escape the encapsulation. 
         [0018]    The surrounding portion may be fabricated in a variety of ways. For example, the surrounding portion may comprise one or more filaments. The surrounding portion may comprise a filter/bag, a coil, helical filament, a mesh structure, corrugated sheet, braided filaments, single wound or crossing filaments, tubes, membranes, films, solid wires, filled tubes, castings. Furthermore, the surrounding portion may have one or more ports, openings, slits, and/or holes. The surrounding portion may be made by photochemical etching, mechanical drilling, weaving, braiding, laser cutting, or other means. 
         [0019]    It should be noted that reference to surrounding or securing the obstruction includes partially and/or fully surrounding, engulfing, encapsulating, and/or securing the obstruction. In any case, the surrounding portion engages the obstruction prior to translation of the obstruction within the lumen. As noted herein, a porn on of the device may convert into a surrounding section (e.g., when traversing wires reorient to increase the friction acting on the obstruction). Accordingly, the traversing section converts into a surrounding section. 
         [0020]    The various devices described herein rely on a reduced profile for delivery and an expanded profile for ultimate removal of the clot. The devices, or components of the devices, may expand when released from a constraint, which allows the device, or component, to assume a predetermined shape. Alternatively, or in combination, the devices may be actuated to assume the expanded profiles. For example, the devices may be shape memory alloys that assume a profile when reaching a predetermined temperature (e.g., body temperature, or another temperature via delivery of energy to the shape memory alloy to trigger a phase change). Actuation may also include use any expandable member (such as a coiled spring, balloon, wedge, etc.) that mechanically or fluidly forces expansion of the device. These modes are well known by those skilled in the art and are intended to be within the scope of the disclosure. When combined with the inventive concepts disclosed herein, such combinations fall within the inventive scope of this disclosure. 
         [0021]    As noted above, the filaments of the invention may be used to translate the device or may be used to form the surrounding; section. Accordingly, the filaments may be single wound or crossing filaments, tubes, membranes, films, solid wires, filled tubes, castings or any similar structure. Moreover, the cross section of such filaments may vary as required (e.g., circular, oval, rectangular, square, or any such shape.) The filaments may be constructed from metals, polymers, composites, hydrogels, membranes, shape memory metals, shape memory polymers, or shape memory alloys, superelastic metals, superelastic polymers, or superelastic alloys, or combinations thereof. The filaments may have uniform diameters or varying diameters. The characteristics of the filament may be selected to better suit their required function. For example, they can be stiff, floppy, or even have different zones of flexibility. Moreover, the filaments may be braided or woven members, or the construction may provide that the filaments cross at one or many points in an overlapping, interwoven, criss-crossing or similar manner. 
         [0022]    It should be noted that in some variations of the invention, all or some of the filaments (used in the surrounding portion of the device) can be designed to increase their ability to adhere to the obstruction. For example, the filaments of the surrounding portion may be coupled to an energy source (e.g., RF, ultrasonic, or thermal energy) to “weld” to the obstruction. Application of energy to the filaments may allow the surrounding portion to deform into the obstruction and “embed” within the obstruction. Alternatively, the filaments may impart a positive charge to the obstruction to partially liquefy the obstruction sufficiently to allow for easier removal. Alternatively, a negative charge could be applied to further build thombus and nest the device for better pulling force. The filaments may be made stickier by use of a hydrophilic substance(s), or by chemicals that would generate a chemical bond to the surface of the obstruction. Alternatively, the filaments may reduce the temperature of the obstruction to congeal or adhere to the obstruction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Each of the following figures diagrammatically illustrates aspects of the invention. Variation of the invention from the aspects shown in the figures is contemplated. 
           [0024]      FIG. 1  illustrates a system for removing obstructions from body lumens. 
           [0025]      FIG. 2A  illustrates an example of an obstruction lodged within a body lumen. 
           [0026]      FIGS. 2B to 2F  illustrate advancement of a catheter beyond an obstruction and placement of traversing wires around the obstruction. 
           [0027]      FIG. 3A  illustrates an obstruction removal device once converted to a high friction mode. 
           [0028]      FIGS. 3B to 3E , show variations of a device having filaments that do not cross one another over the length of the obstruction when converted to a high friction mode. 
           [0029]      FIG. 3F to 3G  illustrate positioning a surrounding portion and translating the surrounding portion over the obstruction. 
           [0030]      FIGS. 3H to 3I  illustrate an obstruction removal device deployed distally to an obstruction and then translated proximally over the obstruction. 
           [0031]      FIGS. 4A to 4E  illustrate various additional configurations of devices able to assume a high friction mode covering over an obstruction. 
           [0032]      FIG. 4F  illustrates a variation of a device using an end of a catheter for converting the device to a high friction mode. 
           [0033]      FIG. 5A to 5B  illustrate another variation of a portion of an obstruction removal device configured to convert from a low friction mode to a high friction mode. 
           [0034]      FIGS. 6A to 6G  illustrate various configurations of connectors for use with obstruction removal devices. 
           [0035]      FIGS. 6H to 6I  illustrate a variation of a leading wire and connector having an unconstrained shape that is selected to be larger or simply different than the intended vessel to provide increased, stability upon deployment. 
           [0036]      FIG. 7A to 7D  illustrates variations in which the connector is offset 
           [0037]      FIGS. 8A to 8B  illustrate hooks, fibers, and/or barbs for increasing the ability of the device to remove obstructions. 
           [0038]      FIGS. 9A to 9C  illustrate additional variations of obstruction removal devices. 
           [0039]      FIGS. 10A to 10H  also illustrate additional variations of obstruction removal devices, focusing mainly on variations of the surrounding portion. 
           [0040]      FIGS. 11A to 11C  illustrate a variation where use of mechanical expansion distends the vessel wall and loosens the obstruction from the vessel. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    It is understood that the examples below discuss uses in the cerebral vasculature (namely the arteries). However, unless specifically noted, variations of the device and method are not limited to use in the cerebral vasculature. Instead, the invention may have applicability in various parts of the body. Moreover, the invention may be used in various procedures where the benefits of the method and/or device are desired. 
         [0042]      FIG. 1  illustrates a system  10  for removing obstructions from body lumens as described herein. In the illustrated example, this variation of the system  10  is suited for removal of an obstruction in the cerebral vasculature. Typically, the system  10  includes a catheter  12  microcatheter, sheath, guide-catheter, or simple tube/sheath configuration for delivery of the obstruction removal device to the target anatomy. The catheter should be sufficient to deliver the device as discussed below. The catheter  12  may optionally include an inflatable balloon  18  for temporarily blocking blood flow or for expanding the vessel to release the obstruction 
         [0043]    It is noted that any number of catheters or microcatheters maybe used to locate the catheter/microcatheter  12  carrying the obstruction removal device (not illustrated) at the desired target site. Such techniques are well understood standard interventional catheterization techniques. Furthermore, the catheter  12  may be coupled to auxiliary or support components  14 ,  16  (e.g., energy controllers, power supplies, actuators for movement of the device(s), vacuum sources, inflation sources, sources for therapeutic substances, pressure monitoring, flow monitoring, various bio-chemical sensors, bio-chemical substance, etc.) Again, such components are within the scope of the system  10  described herein. 
         [0044]    In addition, devices of the present invention may be packaged in kits including the components discussed above along with guiding catheters, various devices that assist in the stabilization or removal of the obstruction (e.g., proximal-assist devices that holds the proximal end of the obstruction in place preventing it from straying during removal or assisting in the removal of the obstruction), balloon-tipped guide catheters, dilators, etc. 
         [0045]      FIGS. 2A to 2F  show one example of the deployment of the basic structure of connectors and traversing filaments about an obstruction in a vessel. The figures are intended to demonstrate the initial placement of the connectors and filaments immediately prior to removal of the obstruction either using a filter or by torquing, rotating and/or twisting the near connector relative to the far connector. This action converts the device from a low friction device to a high friction device (where the low/high friction is the friction between the device and the obstruction). This action may also be referred to as a low surface area mode converting to a high surface area mode (in cases where the device extends beyond the obstruction and relative motion between ends of the device causes the device to shrink in axial length as it is twisted.) In addition, the number of connectors used, the shape of the connectors, as well as the number of filaments is intended to be for illustrative purposes only. It is contemplated that any variation of connector and/or filament may be deployed in a similar manner. 
         [0046]      FIG. 2A  illustrates an example of an obstruction  2  lodged within a body lumen or vessel  6 . In the case where the vessel is a cerebral artery, the obstruction may result in an ischemic stroke. Using standard interventional catheterization techniques, a microcatheter  102  and guidewire  104  traverse the obstruction. The microcatheter  102  may be advanced through the obstruction  2 . Alternatively, the microcatheter  102  may “push” aside the obstruction and is advanced around the obstruction. In any case, the microcatheter  102  travels from the near end  3  (or proximal side) of the obstruction  2  to the far end  4  (or distal side) of the obstruction  2 . It is noted that the catheter  102  may be centered or off-center with respect to the obstruction  2 . Furthermore, the device may or may not be used with a guidewire to navigate to the site and traverse the obstruction. 
         [0047]      FIG. 2B  shows another variation where a microcatheter  102  traverses the obstruction  2  between the wall of the vessel  6  and the obstruction  2 . As shown, the open end of the microcatheter  102  is distal to the obstruction  2  and is now positioned to deploy devices for removal of the obstruction  2 . This variation shows the device after removal of any guidewire. However, some variations of the device may be placed without an accompanying guidewire. Moreover, the structures discussed herein may be directly incorporated into a guidewire assembly where deployment may require a sheath or other covering to release the components from constraint. 
         [0048]      FIG. 2C  illustrates deployment of a far connector  110  from within the microcatheter  102  distal to the obstruction  2 . The far connector  110  can be self-expanding such that it assumes, or moves towards, the expanded profile as shown) upon deployment from the constraint of the microcatheter  102 . 
         [0049]    The connectors  108 ,  110  and/or traversing filaments  112  are designed to expand to the wall of the vessel when released from the catheter. This action allows the device  100  to surround the obstruction  2  prior to attempting to dislodge it. The components of the obstruction removal device  100  (e.g., the leading wires  106 , the connectors  108   110 , the traversing filaments  112 , and/or the surrounding portion  114 , may be fabricated from any biocompatible material that permits the function as described herein. In sonic variations, the material may comprise a shape memory or super-elastic alloy such as nitinol. 
         [0050]      FIG. 2D  shows withdrawal of the microcatheter  102  to the proximal side  3  of the obstruction  2 . The spacing between the far connector  110  and the obstruction  2  may vary. In some cases, the far connector  110  will move closer towards the obstruction  2  during spacing of the traversing; filaments  112  as discussed below. The far connector  110  remains in place either using the inherent friction of the connector against the vessels and/or obstruction  2 . Alternatively, or in combination, a wire-type member (not shown) may provide an opposing, force against the connector  110  as the catheter  102  moves proximal to the obstruction  2 . 
         [0051]    As discussed herein, the obstruction removal devices include a plurality of filaments affixed between connectors. Since the far connector  110  is deployed at the distal side  4  of the obstruction  2 , withdrawal of the microcatheter  102  results in the plurality of filaments  112  spanning across the obstruction  2  as shown. 
         [0052]      FIG. 2E  illustrates deployment of a near connector  108 . Although the illustrated variation depicts the near connector  108  as being deployed from within the microcatheter  102 , alternative variations of the device include a near connector  108  that is located about the exterior of the microcatheter  102  or that is located about another delivery device (not shown) that is external to the microcatheter  102 . In this case, the near connector  108  is similar in profile and design to the far connector  110 . Accordingly, the near connector  108  self expands within the vessel  6  upon deployment from the microcatheter  1 . 02 . In some variations of the device, the near and far connectors  108 ,  110  may have different shapes or profiles. In any case, the profile of the connectors should be sufficient to expand the traversing wires sufficiently within the vessel to prepare for ensnaring or encapsulation of the obstruction  2 . 
         [0053]      FIG. 2E  also illustrates a connecting or leading wire/member  106  that couples the microcatheter  102  to the near connector  108 . The term leading wire, leading member, lead wire, etc. is intended to encompass a wire, tube, or any other structure that organizes and sometimes houses the smaller traversing filaments and/or near connectors described herein. Naturally, variations of the device include a leading wire  106  that is affixed to the far connector or the traversing wires. Moreover, the illustration depicts a single leading wire  106 . However, as noted below, the device can include a number of traversing wire  106  affixed to the near and/or far connectors  108 ,  110 . 
         [0054]      FIG. 2F  illustrates spacing the traversing filaments/wires  112  from simply spanning the obstruction  2  (as depicted in  FIG. 2E ). This action causes the filaments  112  to span the obstruction  2  while reorienting towards an exterior of the obstruction  2 . As noted herein, the traversing filaments  112  may remain partially or fully within the obstruction  2 . However, given that the filaments are spaced about the connectors, the filaments shall separate radially over the obstruction allowing for the subsequent ensnaring and removal. 
         [0055]    Spacing the filaments may occur via a number of modes such as tensioning, expanding, spreading separating and/or withdrawing the filaments. In certain variations of the device, the filaments are moveable relative to a near connector and/or a far connector. Such a feature allows application of tension to the filaments while keeping the connector in place. This causes the filament to enter a state of tension for spacing about the wall of the vessel. Alternatively, the filaments may be fixed relative to the connectors. Upon deployment, the filaments either self expand or are actuated to space about the vessel wall for eventual translation of the device over the obstruction. Regardless of the mode used, the filaments are intended to be positioned at or near a surface of the obstruction so that they can reduce the effects of any friction between the obstruction and the lumen or vessel wall. 
         [0056]      FIGS. 3A to 3I  provide illustrations of device variations that ensnare the obstruction  2  after the device is in the configuration demonstrated by  FIG. 2F  above.  FIGS. 3A ,  3 C, and  3 E represent variations of the device  100  after transforming from a low friction mode to a higher friction mode for removal of the obstruction.  FIGS. 3F and 3G  illustrate a variation Where a surrounding portion or filter covers the obstruction for its ultimate removal from the body. 
         [0057]      FIG. 3A  illustrates rotation of the near connector  108  relative to the far connector  110  to ensnare the obstruction  2  within the traversing wires  112 . As noted herein, either connector may rotate while another connector remains stationary. Alternatively, each connector may rotate with the rate of rotation for one connector being, slower than another. In yet another variation, each connector may be rotated in opposite directions. 
         [0058]    Although the variation shows only four traversing, wires  112  any number of wires may be used so long as the rotation converts the traversing wires  112  into a relatively increased friction mode as compared to the low friction mode (when the traversing wires are in a parallel configuration). The low friction mode is represented by  FIG. 2F .  FIG. 3A  illustrates the obstruction removal device  100  after rotation of the sets of traversing filaments and connectors. The result is that the obstruction  2  becomes ensnared (and/or encapsulated) and may be removed from the body. It should be noted that the same effect may be achieved by only rotating one connector or set of wires while keeping the other connector or set of wires stationary. 
         [0059]    The rotation of the connector  108  can be performed in any number of ways as known to those skilled in the art. However, as shown in  FIG. 3A , the lead wire  106  may comprise additional secondary wires attached to the connector  108 . So rotation of the connector  108  may occur via rotation of the lead wire and/or microcatheter. In any case, once the device assumes the increased friction mode condition, the obstruction  2  can he moved laterally within the vessel for removal. 
         [0060]      FIGS. 3A to 3E  illustrate various configurations where relative rotation of the connectors  108 ,  110  convert the device into a high friction mode. In  FIG. 3A , the traversing filaments  112  twist and cross one another over the length of the obstruction  2 . However, as shown in  FIGS. 3B to 3E , variations of the device  100  can have filaments  112  that do not cross one another over the length of the obstruction  2 . Although these variations are depicted to have single connectors on each end and four filaments, the design of the devices may vary as required by the particular application. In addition, the variations shown in  FIGS. 3B to 3E  are shown without any catheter or leading wire for convenience to better illustrate the conversion of the device from a low friction mode to a high friction mode. Naturally, rotation of the catheter and/or lead wire will cause relative rotation between connectors. 
         [0061]    In  FIG. 3B , the device  100  is in a similar position as that shown in  FIG. 2E . However,  FIG. 3B  shows a variation of a device  100  that is is selected to have a length greater than the targeted obstruction  2 . Upon rotation, the traversing filaments  112  remain uncrossed over the length of the obstruction  2 . In some cases, the filaments  112  may experience some twisting and will not remain parallel. However, the filaments  112  twist at twist points  116  that are proximal to and distal to the obstruction  2 . The relative motion of the connectors  108 ,  110  as well as the twist point  116  causes the filaments  112  to exert a compressive force on the obstruction  2  without crossing one another over the length of the construction. Accordingly, while the surface area in contact between the filaments  112  and obstruction  2  remains relatively the same, the compressive action of the filaments  112  onto the obstruction converts the device  100  to a high friction mode on the obstruction. 
         [0062]      FIG. 3D  illustrates another variation of a device in a similar position as that shown in  FIG. 2E . However,  FIG. 3D  shows a variation of a device  100  that extends proximally from the near end of the obstruction  2 . The relative motion between connectors  108 .  110  causes a twist point  116  that is proximal to the obstruction  2 . As with the previous variation, the twist point  116  forces the filaments  112  against the obstruction  2  without crossing one another over the length of the obstruction  2 . As a result, the device  100  is now in high friction mode. In some cases, the filaments  112  may experience some twisting and will not remain parallel. 
         [0063]    The variation of  FIGS. 3D and 3E  also show the device  100  as including a cap or cover  118  about the distal connector  110 . The cap or cover  118  may be a bag, mesh, a continuation of the filaments  112 , and/or a surrounding, portion  114  as discussed herein. The cap or cover  118  reduces the likelihood that the obstruction is driven through the far connector  110  during conversion of the device  100  from a low friction mode to a high friction mode. 
         [0064]      FIG. 3F  illustrates another variation of a device where the far connector  110  includes a filter or surrounding; portion  114 . In variations of the device, the filter  114  is sufficiently permeable to allow blood flow therethrough. As noted above, the surrounding portion  114  may be any structure that covers, encapsulates, engulfs, and/or ensnares the obstruction either fully or partially. Accordingly, although the surrounding portion  114  is illustrated as a filter/bag, the surrounding portion  114  may comprise a coil, helical wire, a plurality of filaments, mesh structure, corrugated sheet, braided filaments, single wound or crossing filaments, tubes, filled tubes, castings, solid wires, membranes, films, capturing sections, (and may include ports, openings, slits, and/or holes made from photochemical etching, mechanical drilling) or any other structure that may translate or remove the obstruction  2  once the frictional component is addressed. 
         [0065]    In this variation, the obstruction removal device  100  includes leading filaments  106  connected to a near connector  108 . In this example, the lead filament  106  may be a single wire or filament. Alternatively, the lead filament may comprise a single wire with a plurality of wires connecting the single wire to the ring. 
         [0066]    As with the above examples, the illustrated variation shows the connector  108  as comprising a loop. However, as described herein, the connectors may also comprise various alternate shapes (e.g., a circle, an arcuate shape, a partial circular shape, a loop, an oval, a square, a rectangle, a polygon, an overlapping loop, a pair of semi-circles, a flower shape, and a  FIG. 8 , other shapes, etc.) The near connector  108  is joined to a far connector  110  via a plurality of filaments  112 . It is noted that the inventive device shall include at least one, but preferably two or more traversing filaments  112 . It is further noted that the obstruction removal device  100  may he part of or integrated with the microcatheter  102 . 
         [0067]      FIG. 3G  illustrates withdrawal of the microcatheter  102  and the proximal translation of device  100  to place the surrounding portion  114  over the obstruction  2 . As the obstruction removal device  100  translates proximally, the traversing filaments  112  locate towards the exterior region of the obstruction  2 . As discussed above, the connectors  108 ,  110  and traversing filaments  112  are designed to expand to (or near to) the perimeter of the wall of the vessel  2  and will usually locate to an exterior of the obstruction  2 . However, variations of the device and method include situations where the filaments locate substantially, but not fully, towards the outer region of the obstruction. In any case, the location of the filaments  112  will sufficiently overcome the frictional forces discussed herein. In the illustrated variation, the traversing filaments  112  substantially span the length of the obstruction  2  by extending across the (proximal)  3  and (distal)  4  sides. These traversing filaments  112  provide paths for movement of the device  100  around the obstruction  2 . These paths allow for the surrounding portion  114  to engulf the entire obstruction  2  so that it may be removed from the vasculature and body. 
         [0068]      FIG. 3H  depicts an obstruction removal device  100  similar to that shown in  FIG. 3F . However, in this variation, the near and far connectors  108 ,  110  are both deployed distally to the obstruction  2  and then translated back over the obstruction  2 . As shown, this deployment allows the traversing filaments  112  and the surrounding portion  114  to separate prior to contacting the occlusion  2 . Next, the entire device  100  is pulled over the occlusion  2  as described above. The variation of the device shown in  FIGS. 3F and 3H  addresses the frictional forces that act between the obstruction and the vessel wall. Conventional devices that provide a bag attached to a wire (such as a vascular filter or distal protection device), are typically unable to remove the obstruction because they cannot overcome these frictional forces that lodge the clot against the vessel wall. Typically, such conventional devices are only designed to “catch” free floating clots. The traversing filaments described herein are configured to be positioned surrounding the obstruction. Their low friction with respect to the clot and the vessel allows for positioning of the filaments without disrupting or further compacting the clot against the vessel wall. Once the filaments surround or are spaced about the obstruction, they reduce the friction between the clot and vessel wall by reducing points of contact. Once these filaments surrounded the clot, they permit translation of the device to permit an encapsulating section  114  to surround the obstruction for removal. 
         [0069]      FIG. 3I  illustrates the device  100  of  FIG. 3H  when translated over the obstruction  2 . Eventually, the device  100  is pulled so that the surrounding portion or blood permeable filter  114  covers the obstruction  2  (as shown in  FIGS. 3F  arid  3 G. 
         [0070]      FIG. 4A  illustrates another variation of a portion of an obstruction removal device  120  that is able to convert from a low friction mode covering to a higher friction mode covering. As noted above, this variation allows the medical practitioner to engage an obstruction with sparse coverage or low friction mode to overcome frictional forces. Upon properly engaging the obstruction, the device configuration allows conversion to a high friction mode for removal of the device and obstruction. 
         [0071]    As shown, this variation of the obstruction removal device  120  includes two sets of traversing filaments  122 ,  124  and accompanying connectors  108 ,  110 , and  126 ,  128 . The first set  122  comprises a first near connector  108  and first far connector  110  with the accompanying traversing filaments. The second set  124  comprises the second near connector  126  and second far connector  128  with the accompanying traversing filaments  124 . The second set  124  is coaxially located over the first set  122 . The materials of the components may be as described above. In any case, the components are designed to expand to the perimeter of the vessel wall upon release from the catheter. 
         [0072]      FIG. 4B  shows the conversion of the obstruction removal device converting from a low friction mode (from  FIG. 4A ) to the high friction mode. For example, the first near connector  108  may be rotated relative to the second near connector  126  (where the second near connector may remain still or it may be rotated in an opposite direction relative to the first near connector as shown by the arrows). As a result, the traversing filaments  122 ,  124  deform in opposite directions to form a braid-type pattern increasing the friction mode over the obstruction. 
         [0073]      FIG. 4C  illustrates another variation of an obstruction removal device  100  in a low friction mode state. In this variation, the device  100  includes a near connector  108 , a far connector  110  with traversing filaments between the connectors  108 ,  110 . The device  100  also includes an additional connector  132  with non-rotating filaments  134  extending to the far connector  110 .  FIG. 4D  illustrates the device  100  of  FIG. 4C  when the near connector  108  is rotated as shown by arrow  136 . However, the additional connector  132  and associated filaments  134  do not rotate. Upon rotation of the near connector  108  and twisting of the filaments  112 , all of the filaments  112  and  134  compress the obstruction over the length of the filaments. Such a feature creates additional friction on the obstruction by the device. 
         [0074]      FIG. 4E  shows another variation of an obstruction removal device  100  configured to move between low and high friction mode states. This variation includes additional support rings  138  located between connectors  108 ,  110  and within the filaments  112 . The support rings keep the device  100  at a relatively constant diameter upon assuming the increased friction mode state. The support rings may be slightly undersized compared to the connectors, allowing the filaments to slightly compress the obstruction when converted to a high friction mode, but limiting the amount of compression by limiting the resulting diameter. The support rings  138  can be freely placed within the traversing filaments  112 . Alternatively, the rings  138  can be attached to one or more than one filament  112  to prevent undesired migration during deployment of the device. 
         [0075]      FIG. 4F  illustrates one example of a microcatheter  102  having a near connector  108  located externally to the catheter  102  with traversing filaments  112  extending out of the catheter and through the connector  108 . In this variation, rotation or torquing of the catheter  102  twists the filaments  112  resulting in increased friction mode of the filaments  112  over an obstruction.  FIG. 4F  illustrates an additional connector  132  having stationary filaments  134 . This variation of the device includes the external connector  108  directly coupled to a far connector not shown.) 
         [0076]      FIG. 5A  illustrates a variation of the device  120  having only connectors  108  at one side of the device  120 . In this variation, the device  120  may still include two sets  108 ,  122  of connectors and two sets of traversing filaments  112 ,  124 .  FIG. 5B  illustrates the variation of  FIG. 5A  after conversion to a high friction mode over the obstruction  2 . As discussed herein, the connectors may be other structures than loops. Moreover, variations of the invention include connectors that may be drawn down to a smaller size to facilitate removal from the body after securing the obstruction. This may be accomplished by torquing: the device or pan thereof, by re-sheathing part or all of the device, or by any mechanical means designed into the features of the device itself. Any of these actions, or combination thereof, may also serve to compress or decrease the diameter of the obstruction itself to facilitate removal from the body. 
         [0077]    In another variation, the devices described herein may be assembled or constructed in-situ. For example, components of the device may include connectors, portions of the connectors, traversing elements, and/or surrounding sections. Any combination of these components can be placed in sequential fashion. Doing so forms a completed structure from deployment of a number of individual components. The end result is the formation of a device as shown in the figures. Accordingly, such components of the device may be separately deployed in a manner that requires “assembly” of the components by a medical practitioner during the procedure. 
         [0078]      FIGS. 6A-6G  illustrate variations of the connectors  108 ,  110 .  FIG. 6A  shows a loop-shaped connector  108 ,  110  having attachment points  140  for the filaments (not shown). As noted above, the connectors can be self-expanding or actuated to expand. The connectors may be fabricated from a polymer, a shape memory metal, polymer, or alloy, a super-elastic metal, polymer, or alloy, or any type of acceptable medical grade alloy, polymer, or composite structure. Also, the devices described herein can be fabricated from solid material, sheet or film, hollow or solid or filled rod or wire, braids, coils, etc. In the case of the polymer, additional strength may be added by constructing a composite layered device. For example, a hydrogel polymer with a hydrophilic fiber net inside that acts as exoskeleton to strengthen underlying polymer. As discussed herein, some variations of the device may include a distal connector having a cap or cover to prevent the obstruction from escaping as the device is removed. Furthermore, the sizing of the connectors within the vessel can assist in controlling relative rotation between connectors. For example, as a connector moves towards its expanded shape and engages a vessel or lumen wall, the rotational friction between the connector and lumen wall may prevent rotation. Accordingly, an adjacent connector may have a smaller expanded profile so that the connector experiences less friction when rotated. 
         [0079]      FIG. 6A  also illustrates the connector as having attachment points  140  for coupling the filaments to the connectors. These attachment points may allow for movement of the filaments relative to the connector to tension or separate the connectors (as described above.) The filaments may also be coupled such that they are fixed relative to the connectors. In such a case, pulling of the lead wire will cause the entire assembly (e.g., connectors, filaments, and/o surrounding portion) to translate through the vessel. 
         [0080]      FIGS. 6B through 6G  show various configurations of connectors for use in the present device. The connectors may be cut from sheets, fabricated from wire, molded, stamped, laser cut, photo or chemically etched, or fabricated in any other customary manner. Moreover, the connectors  108 ,  110  shown may be used in the near and/or far ends of the traversing wires Different connector profiles may be incorporated into the device. In most cases, as shown, the connectors will form an arcuate shape so that they can expand against a vessel wall without causing trauma to the vessel. To illustrate the connector configurations,  FIGS. 6B to 6E  are shown without any accompanying traversing filaments. 
         [0081]      FIG. 6B  shows a connector  108 ,  110  that is a loop shape as shown above. However, alternative configurations include a discontinuous profile, as illustrated in  FIG. 6C  and an overlapping profile, as illustrated in  FIG. 6D . Such constructions allows the connector to adjust to varying diameters of body lumens. It is noted that a device may comprise loops of either construction. It should be also noted that although loops are shown, other variations may work equally well. Variations of the invention include connectors that may be drawn down to a smaller size to facilitate removal from the body once the obstruction is secured. This may be accomplished by torquing the device or part thereof, by re-sheathing part or all of the device or by any mechanical means designed into the features of the device itself. Any of these actions, or combination thereof, may also serve to compress or decrease the diameter of the obstruction itself to facilitate removal from the body. In addition, the overlapping connector, as shown in  FIG. 6D , may include a sliding ring type fastener that allows the overlapping connector loop to expand in the same plane. 
         [0082]    In another example, the device may be fabricated from a polymer composite that makes up the fasteners, filaments, bags, etc. where the polymeric composite is very floppy until it is exposed to either the body fluids and or some other delivered activator that causes the polymer to further polymerize or stiffen for strength. Various coatings could protect the polymer from further polymerizing before the device is properly placed. The coatings could provide a specific duration for placement (e.g., 5 minutes) after which the covering degrades or is activated with an agent (that doesn&#39;t affect the surrounding tissues) allowing the device to increase in stiffness so that it doesn&#39;t stretch as the thrombus is pulled out. For example, shape memory polymers would allow the device to increase in stiffness. 
         [0083]      FIG. 6E  shows a connector  108 ,  110  having multiple sections  146 . As noted above, the connector sections  146  are arcuate shaped to minimize trauma to a vessel wall. However, other shapes are also intended to be within the scope of this disclosure. 
         [0084]      FIGS. 6B through 6G  also illustrate various configurations of leading wires  106 . The connectors may have any number of leading wires. In some variations, it may be desirable to space the leading wires about the profile of the connector to aid in uniform movement of the device as it is pulled over the obstruction in the vessel. 
         [0085]      FIG. 6F and 6G  illustrate additional variations of leading wires  106  comprising shaped wire structures that form a “c” portion  142  of the connector. In one variation, when constrained the “c” shaped portions  142  move together to allow for deliver within the catheter. Upon release from the catheter, the portions  142  assume their resting shape and expand within the vessel. The connecting portions  142  can be selected to have a size that is slightly greater than that of the vessel. Sizing the device relative to the target vessel may assist in placing the connecting portions  142  and accompanying traversing wires  112  against the wall of the vessel. 
         [0086]      FIG. 6G  shows an additional variation where a portion  144  of a leading wire  106  also has a “c” or semi-circular shape. In this configuration, the “c” shaped portion  144  of the leading wire  106  can also be sized relative to the target vessel. Accordingly, the portion  144  of the leading wire  106  functions to drive the connecting portion  142  against the vessel wall, while the shape of the connecting portion  142  also drives the traversing wire  112  against the vessel wall. 
         [0087]      FIG. 6H  illustrates another variation of a leading wire  106  having an unconstrained shape that is selected to be larger than the intended vessel or simply different than a cross sectional profile of the intended vessel (i.e., not circular or tubular, but e.g., linear or other different shape). In this variation, the leading wire  106  has portions  144  that extend in opposite directions. This configuration is intended for illustrative purposes only. Variations include connecting portions pointing in an orthogonal direction from the main lead wire  106 , oblique, parallel as shown), or a combination thereof. In any case, the unconstrained shape is intended to have a larger profile or size than the intended vessel. Moreover, the unconstrained shape may have an entirely different profile than the intended vessel. As shown in the figures, the profile of the device extends radially from the vessel. So when the device and leading wire are released, the leading wire attempts to return to the unconstrained shape. In those variations where the unconstrained shape is different from the circular profile of the vessel, the leading, wire assumes a shape that accommodates the vessel but is more rigid and stable since its unconstrained shape is entirely different from that of the vessel. 
         [0088]      FIG. 6I  shows the same device of  FIG. 6H  when released from a microcatheter, sheath, or tube when in the vessel. Once released, the leading wire  106  and accompanying portions  144  attempt to revert to the unconstrained shape (as shown in  FIG. 6H ). However, the vessel  6  restrains the leading wire  106  and portions  144  such that the portions  144  act on the walls of the vessel. This feature allows for improved stability when deploying the leading wires and attached connectors and filaments within the vessel. 
         [0089]      FIGS. 7A through 7C  illustrate variations of connectors  108 ,  110  where the connector portions are axially spaced by an offset  152 . One benefit of placing the connector portions  142 ,  146  in different planes is that the device may be delivered via a smaller microcatheter because the connector portions may be collapsed to a smaller diameter.  FIG. 7A  illustrates an offset  152  between connector portions  142  where each portion  142  is coupled to leading wires  148 ,  150  of varying lengths.  FIG. 7B  illustrates connector portions  146  spaced axially along a leading wire  106  to provide a gap  152 .  FIG. 7C  illustrates a connector  108 ,  110  having multiple components  146  where one or more components is axially spaced to provide a gap  152 .  FIG. 7D  shows a variation  108 ,  110  having a flower shape where each connector portion  146  is lion-planar such that the gap  152  occurs over the length of the connector portion  146 . 
         [0090]    Another aspect applicable to all variations of the devices is to configure the devices (whether the traversing filament or the surrounding portion) for better adherence to the obstruction. One such mode includes the use of coatings that bond to certain clots (or other materials causing the obstruction.) For example, the traversing filament and/or surrounding portion may be coated with a hydrogel or adhesive that bonds to a thrombus. Accordingly, as the surrounding portion covers the clot, or as the device twists about the clot, the combination of the additive and the mechanical structure of the device may improve the effectiveness of the device in removing the obstruction. 
         [0091]    Such improvements may also be mechanical or structural. For example, as shown in  FIG. 8A , the traversing members may have hooks, fibers, or barbs  154  that grip into the obstruction when the device converts to a high friction mode. The hooks, fibers, or barbs  154  may also be incorporated into the surrounding portion. However, it will be important that such features do not hinder the ability of the practitioner to remove the device from the body. For example,  FIG. 8B  illustrates a magnified view of the area  8 B from  FIG. 8A . As illustrated, the barbs may be configured such that rotation in a particular direction causes the barbs to adhere to the obstruction. Such a configuration could also allow lateral movement, without the barbs interfering with the vessel. 
         [0092]    In addition to additives, the device can be coupled to an RF or other power source such as  14  or  16  in  FIG. 1 ), to allow current, ultrasound or RF energy to transmit through the device and induce clotting or cause additional coagulation of a clot or other the obstruction. 
         [0093]    The methods described herein may also include treating the obstruction prior to attempting to remove the obstruction. Such a treatment can include applying a chemical or pharmaceutical agent with the goal of making the occlusion shrink or to make it more rigid for easier removal. Such agents include, but are not limited to chemotherapy drugs, or solutions, a mild formalin or aldehyde solution. 
         [0094]    Although not illustrated, the devices and methods described herein may also be useful in removing obstructions lodged within bifurcations in the anatomy. Generally, bifurcations greatly increase the frictional forces on the obstructions since the obstruction tends to be lodged in both branching sections of the bifurcation. In such cases, the use of the presently described devices and methods may also include an additional “puller” device that advances beyond the portion of the obstruction partially located in the bifurcated vessel. 
         [0095]    As for other details of the present invention, materials and manufacturing techniques may be employed as within the level of those with skill in the relevant art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts that are commonly or logically employed. In addition, though the invention has been described in reference to several examples, optionally incorporating various features, the invention is not to be limited to that which is described or indicated as contemplated with respect to each variation of the invention. 
         [0096]      FIGS. 9A through 9C  illustrate additional variations of obstruction removal devices. In these variations, the traversing filaments  112  may comprise a mesh of wires or single connector.  FIGS. 9A to 9B  illustrate a variation in which the connector  108  comprises a wire rather than a loop. However, the filaments and connectors should be configured to expand to the perimeter of the vessel wall as described previously. 
         [0097]      FIGS. 10A-10H  illustrate various additional embodiments of obstruction removal devices  130  according to the present invention. In these variations, the connector  108  may form a rigid wire or hard polymer to assist in placement of the device  130 . The surrounding portion  132  may be fabricated from less rigid filaments that increase the point of contact with the obstruction. The surrounding portion may also have filaments that undergo a phase change from non-rigid for less rigid) to rigid. 
         [0098]    It should be noted that any number of traversing filaments  112  or sets may he used in these variations. 
         [0099]    In additional aspect of the invention, as shown in  FIG. 11A to 11C , the methods and or devices may include expansion of the vessel wall adjacent to the obstruction either with a balloon, coil, or similar mechanical expansion means, drugs, fluids, etc. Such an improvement may aid where the obstruction expands part, of the vessel wall thereby increasing the amount of force required for displacement. By distending the vessel wall as described above, the forces on the obstruction may he reduced allowing for ease of removal.  FIG. 11A  illustrates an obstruction  2  embedded within the vessel  6 .  FIGS. 11B to 11C  illustrate variations where use of a coil ( FIG. 11B ) or a non-distensible balloon  162  ( FIG. 11C ) proximal to the obstruction  2  distends the vessel wall to loosen the obstruction  2  from the vessel. Accordingly, devices (whether described, herein or other conventional devices) may then remove the obstruction  2 . 
         [0100]    In those variations with a mechanical expansion means, the expansion means may be located on the delivery catheter of the obstruction removal device, on a wire member of the device, and/or on a separate catheter or wire used in combination with the first delivery catheter. However, variations of such configurations are within the scope of the invention. 
         [0101]    In addition, devices and methods described herein may also use balloons proximal to the obstruction to stop or slow blood flow thereby preventing the blood from dislodging part or all of the obstruction. 
         [0102]    Various changes may be made to the invention described and equivalents (whether recited herein or not included for the sake of some brevity) may be substituted without departing from the true spirit and scope of the invention. Also, any optional feature of the inventive variations may be set forth and claimed independently, or in combination with any one or more of the features described herein. Accordingly, the invention contemplates combinations of various aspects of the embodiments or combinations of the embodiments themselves, where possible. Reference to a singular item, includes the possibility that there are plural of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “and,” “said,” and “the” include plural references unless the context clearly dictates otherwise.