Retrieval systems

FIELD OF THE INVENTION

0001The devices described herein are intended to retrieve obstructions from the body. Such devices have applicability throughout the body, including clearing of blockages within body lumens and providing passive protection of such, such as the vasculature, by providing a capturing portion that can translate and/or mobilize the obstruction within the body lumen.

BACKGROUND OF THE INVENTION

0002A large number of medical procedures require the use of medical device(s) to remove an obstruction from a body lumen, vessel, or other organ. An inherent risk in such procedures is that mobilizing or otherwise disturbing the obstruction can potentially create further harm if the obstruction or a fragment thereof dislodges from the retrieval device. If a particle or the obstruction breaks free from the device and flows downstream, it is highly likely that the particle or obstruction will become trapped in smaller and more tortuous anatomy. In many cases, the physician will no longer be able to use the same retrieval device to again remove the obstruction because the size of the device may prevent advancing the device to the site of the new obstruction.

0003Even in successful procedures, a physician must proceed with caution to prevent the walls of the vessel or body lumen from imparting undesired forces to shear or dislodge the obstruction as it is translated through the body during removal. These forces have the potential of breaking portions or fragments of the obstruction away. In some cases, the obstruction can simply break free from the retrieval device and can lodge in a new area causing more concern than the original blockage.

0004Procedures for restoring flow within the cerebral vasculature as a result of ischemic stroke are one example of where these issues present a concern. The brain relies on its arteries and veins to supply oxygenated blood from the heart and lungs and to remove carbon dioxide and cellular waste from brain tissue. 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. To access the cerebral vasculature a physician typically advances a catheter from a remote part of the body (typically a leg) through the vasculature and into the cerebral region of the vasculature. Once within the cerebral region, the physician deploys a device for retrieval of the obstruction causing the blockage. Concerns about dislodged obstructions or the migration of dislodged fragments increases the duration of the procedure at time when restoration of blood flow is paramount. Furthermore, a physician might be unaware of one or more fragments that dislodge from the initial obstruction and cause blockage of smaller more distal vessels.

0005Many physicians currently use stents to perform thrombectomy (i.e. clot removal) to resolve ischemic stroke. Typically, the physician deploys the stent into the clot, in an attempt to push the clot to the side of the vessel and re-establish blood to flow. Tissue plasminogen activator ("Tpa") is often injected into the bloodstream through an intravenous line. The TPA must travel in the blood stream until it reaches the clot that is causing the blockage. Once the Tpa contacts the clot, it begins to break up the clot with the hope of restoring blood flow to the affected areas. Tpa is also often administered to supplement the effectiveness of the stent. Yet, if attempts at clot dissolution are ineffective or incomplete, the physician can attempt to remove the stent while it is expanded against or enmeshed within the clot. In doing so, the physician must effectively drag the clot from the vessel, in a proximal direction, into a guide catheter located within vessels in the patients neck (typically the carotid artery). While this procedure has been shown to be effective in the clinic and easy for the physician to perform, there remain some distinct disadvantages using this approach.

0006The stent may not sufficiently hold onto the clot as it drags the clot to the cathter. In such a case, the clot might not move from the vessel. Another risk is that use of the stent might mobilize the clot might from the original blockage site, but the clot might not adhere to the stent during translation toward the catheter. This is a particular risk when translating through bifurcations and tortuous anatomy. Furthermore, blood flow can migrate the clot (or fragments of the clot) into a branching vessel at a bifurcation. If the clot is successfully brought to the guide catheter in the carotid artery, yet another risk is that the clot may be "stripped" or "sheared" from the stent as the stent enters the guide catheter. Regardless, simply dragging an expanded stent (either fully or partially expanded) can result in undesired trauma to the vessel. In most cases, the stent is oversized compared to the vessel. Dragging a fixed metallic (or other) structure can pull the arteries and/or strip the cellular lining from the vessel, causing further trauma such as a hemorrhagic stroke (leakage of blood from a cerebral vessel). Also, the stent can become lodged on plaque on the vessel walls resulting in further vascular damage.

0007In view of the above, there remains a need for improved devices and methods that can remove occlusions from body lumens and/or vessels. While the discussion focuses on applications in the cerebral vasculature, the improved devices and methods described below have applications outside of the area of ischemic stroke.

0008<patcit id="pcit0001" dnum="EP0200688A2"><text>EP 0 200 688 A2</text></patcit> discloses an interventional medical device for securing a retrieval device for removal from a body comprising an inflatable eversible cover.

SUMMARY OF THE INVENTION

0009According to the present invention there is provided the medical device of claim 1. Additional aspects of the invention are set out in the dependent claims.

0010The examples discussed herein show the inventive device in a form that is suitable to retrieve obstructions or clots within the 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.) However, the devices are not limited to such applications and can apply to any number of medical applications where elimination or reduction of the number of connection points is desired.

0011The devices discussed herein include interventional medical devices for retrieving and securing an obstruction within a vessel lumen. In one example the device comprises a shaft having a flexibility to navigate through tortuous anatomy, the shaft a distal portion and a proximal portion; a capturing structure located at a distal portion of the shaft comprising a plurality of struts, the capturing structure having a reduced profile for positioning in or adjacent to the obstruction and an expanded profile, such that when expanded into the obstruction, the struts at least partially enmesh with the obstruction such that subsequent movement of the capturing structure permits dislocation of at least a portion of the obstruction from the lumen; an eversible cover having a fixed section affixed relative to a proximal end of the capturing structure, a free section extending in a proximal direction from the distal section and a cover wall extending from the fixed section to the free section, where the eversible cover is expandable such that at least a portion of the eversible cover has a diameter equal to or greater than the capturing structure, the eversible cover being axially compliant such that when the shaft is moved proximally within the lumen, in some cases friction between the cover wall and the lumen resists proximal movement of the cover wall to cause the eversible cover to evert over the capturing structure allowing for the free section of the cover to be distal to the fixed end of the capturing portion. Evert or eversible generally includes movement of the device within the cover causing the cover to turn inside out as it protects and covers the retrieval device. The covers disclosed herein can be expandable through self-expanding configurations, or via actuated expansion (e.g., a shape memory alloy, spring expansion, or other actuation).

0012In one example, the device includes a configuration where the eversible cover, capturing structure, and shaft are a unitary structure. The device can also be configured so that each wire located at an end of the free section loops back to the cover causing the wires at the end of the free section to be continuous.

0013In another variation at least a portion of the cover wall adjacent to the distal end has a set shape that is everted upon expansion. The device can also optionally include a catheter body, where in a delivery configuration, the shaft, capturing structure and eversible cover are located within the catheter body and where the capturing structure is advanceable in and out of a distal end of the catheter body.

0014The device can also be configured so that the fixed section of the eversible cover comprises a pre-set shape to reduce a force required to evert the evertable cover.

0015The retrieval devices can comprise any number of capturing or retrieval device such as a filter, an atherectomy device, a rotational cutter, an aspiration device, stent based retrievers and retrieval baskets.

0016The exemplary methods described herein can include methods of securing an obstruction within a vessel. In one example, the method can comprise: positioning a catheter within a vessel; advancing a shaft having a retrieval device affixed thereto out of the catheter; advancing an eversible cover out of the catheter such that a fixed end of the eversible cover is affixed adjacent to a proximal end of the retrieval device and a free end of the eversible cover is moveable relative to the shaft and retrieval device; expanding a at least a portion of the eversible cover against a portion of a wall of the vessel; manipulating the retrieval device to become at least partially enmeshed with the obstruction; and proximally translating the shaft and retrieval device with at least a portion of the obstruction affixed thereto such that resistance of the eversible cover against the vessel resists movement of the eversible cover causing the free section of the eversible cover to evert over the proximally translated retrieval device.

0017In another variation, the exemplary methods can include further withdrawing the shaft from the vessel such that during withdrawal the eversible cover forms a protective barrier over the obstruction to lessen shearing forces caused by the vessel and reduce dislodging portions of the obstruction from the retrieval device.

0018Another variation of an exemplary method includes a method of preparing a retrieval device comprising: providing a retrieval device having been previously removed from a body of a patient where the retrieval device includes a protective cover where a fixed end of the protective cover is affixed adjacent to a proximal end of the retrieval device and where a free end is located distally to the fixed end covering the retrieval device and is moveable relative to the second end; reversing the protective cover by moving the free end proximally of the fixed while the fixed end remains affixed adjacent to the proximal end of the retrieval device; inserting the retrieval device and cover into a catheter where the free end of the cover is proximal to the fixed end of the cover and retrieval device such that upon deployment from the catheter, the free end of the cover deploys proximally to the fixed end of the cover.

0019In another example, the devices described herein can include medical device retrieval systems for securing an obstruction within a vessel lumen and for use with a catheter configured to be navigated through the vasculature. In one variation, the device comprises an elongated stent comprising a plurality of struts, the stent being collapsible for positioning in the catheter during delivery and having an expanded profile such that when expanded the struts are configured to engage the obstruction; a shaft fixedly attached to the elongated stent and having a flexibility to navigate through tortuous anatomy; a fluid permeable cover having a distal end coupled to a proximal end of the elongated stent a cover wall defining a cavity and extending along the shaft, and a proximal end being moveable relative to the shaft, where the fluid permeable cover is collapsible for positioning in the catheter during delivery and is expandable upon deployment from the catheter such that at least a portion of the fluid permeable cover is expandable; where the fluid permeable cover is axially pliable such that when the device is deployed in the vessel the frictional forces between the vessel and the fluid permeable cover permit proximal movement of the shaft and elongated stent to cause inversion of the fluid permeable cover wall such that the fluid permeable cover wall everts over the elongated stent.

0020Another variation of a device includes an interventional medical device for use with a catheter configured for delivery through vasculature for securing an obstruction within a vessel lumen. For example, the device can comprise a shaft having a flexibility to navigate through tortuous anatomy, the shaft having a distal portion and a proximal portion; a capturing device comprising a sidewall, the capturing device fixedly located at a distal portion of the shaft and having a reduced profile for positioning in the catheter and an expanded profile, such that upon deployment from the catheter, the capturing device expands to force a portion of the sidewall into the obstruction to at least partially attach to the obstruction; a cover having a distal end coupled adjacent to a proximal end of the capturing structure, a proximal end and a cover wall extending therebetween, where the proximal end of the cover is slidable relative to the distal end, where the cover is expandable such that when located in the catheter the cover is in a reduced delivery state and upon advancement from the catheter the cover expands with the proximal end located proximally of the distal end, where the cover wall is compliant such that when deployed from the catheter and the shaft is pulled in a proximal direction frictional forces between the vessel and the cover wall or proximal end cause the cover to invert as the cover wall inverts over the capturing device to surround the capturing device.

0021Another variation of the device include an interventional medical device for securing a retrieval device having one or more obstructions located therein for removal from a body. In one such example the medical device includes a sheath having a flexibility to navigate through tortuous anatomy, the sheath a distal portion and a proximal portion and a lumen extending therethrough; an eversible cover having a fixed section affixed to the distal portion of the sheath, a free section extending in a proximal direction from the fixed section and a cover wall extending from the fixed section to the free section, where the eversible cover is expandable, the eversible cover being axially compliant such that when the retrieval device is positioned through the sheath lumen moved in a proximal direction against the eversible cover, the eversible cover everts over the retrieval device allowing for the free section of the cover to be distal to the retrieval device.

0022Another variation of the exemplary method includes advancing a shaft having a retrieval device affixed thereto to the obstruction; advancing a protective device over the shaft, the protective device comprising a sheath having an eversible cover, where a fixed end of the eversible cover is affixed to a distal portion of the sheath and a free end of the eversible cover is located proximal to the fixed end; positioning the fixed end of the eversible cover adjacent to the retrieval device and expanding at least a portion of the eversible cover against a portion of a wall of the vessel; proximally translating the shaft and retrieval device with at least a portion of the obstruction affixed thereto such that resistance of the eversible cover against the vessel resists movement of the eversible cover causing the free section of the eversible cover to evert over the proximally translated retrieval device.

0023The capturing portions described herein can include a stent retrieval device for expanding against one or more occlusive bodies in a vasculature. In one example, the stent retrieval device includes an elongate shaft having a flexibility to navigate through tortuous anatomy, the elongate shaft having a distal portion and a proximal portion; a plurality of filaments that diverge from the distal portion of the elongate shaft to form an expandable elongated stent body having a open distal end and a fluid permeable closed proximal end and a cavity therebetween, where divergence of the filaments at the distal portion of the elongate shaft forms the fluid permeable closed proximal end; where the plurality of filaments extending along the shaft are free of any connection joints in the distal portion to permit increased flexibility of the distal portion as it navigates though tortuous anatomy; and one or more connection joints proximal to the distal portion where the connection joints secure the plurality of filaments to the shaft.

0024The stent retrieval can also include at least one of the plurality of filaments that comprise at least two wires twisted together, the elongated stent body further comprising at least one intersection of filaments, where the wires of each filament are interwoven to provide increased outward radial strength of the elongated stent body and such that the wires slide relative to each other as the elongated stent body expands or compresses in diameter to reduce a force required to linearize the elongated stent body.

0025The stent retrieval device can have an exterior surface of the elongated stent body that comprises an irregular surface formed by intersection of filaments.

0026The stent retrieval device can also have intersection of filaments comprising a barb or knuckle and where a plurality of barbs or knuckles are radially spaced about the elongated stent body. The stent retrieval device can also have an intersection of filaments that comprises a barb or knuckle and where a plurality of barbs or knuckles are aligned with an axis of the elongated stent body.

0027In one variation of the devices described herein, the device comprises a main bundle or group of wires that diverge to form a device having various shapes but few or no connections points or joints (where fabrication of such a construction is referred to as "jointless"). Clearly, the inventive devices described herein are not limited to such a jointless construction. Additional variation includes one or more leading wires that are attached to a capturing portion as described below.

0028Devices of the present invention can incorporate any number of wires of different characteristics including, but not limited to, materials, shapes, sizes and/or diameters. Clearly, the number of permutations of device configurations is significant. Providing devices with such a composite construction allows for the manipulation of the device's properties to suite the intended application.

0029As noted herein, the joint-less construction improves the flexibility and strength of the device by eliminating joints, connection points, or other attachment points. In addition, the joint-less construction improves the ability of the device to be delivered through a small microcatheter. As a result, the device and microcatheter are able to access remote regions of the vasculature.

0030The devices may be fabricated to be self-expanding upon deployment from a catheter. Alternatively, the devices can be constructed from shape-memory alloys such that they automatically deploy upon reaching a pre-determined transition temperature.

0031It should be noted that in some variations of the invention, all or some of the device can be designed to increase their ability to adhere to the obstruction. For example, the wires may be coupled to an energy source (e.g., RF, ultrasonic, or thermal energy) to "weld" to the obstruction. Application of energy to the device can allow the surrounding portion to deform into the obstruction and "embed" within the obstruction. Alternatively, the device can impart a positive charge to the obstruction to partially liquefy the obstruction sufficiently to allow for easier removal. In another variation, a negative charge could be applied to further build thrombus and nest the device for better pulling force. The wires can 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.

0032Additional devices and methods for treating ischemic stroke are discussed in commonly assigned <patcit id="pcit0002" dnum="US67145007" dnum-type="L"><text>U.S. Patent application nos.: 11/671,450 filed February 5, 2007</text></patcit> (published as <patcit id="pcit0003" dnum="US2007225749A"><text>US2007225749</text></patcit>); ; <patcit id="pcit0004" dnum="US11684521B"><text>11/684,521 filed March 9, 2007</text></patcit> (published as <patcit id="pcit0005" dnum="US2007185500A"><text>US2007185500</text></patcit>); <patcit id="pcit0006" dnum="US11684535B"><text>11/684,535 filed March 9, 2007</text></patcit> (published as <patcit id="pcit0007" dnum="US2007185501A"><text>US2007185501</text></patcit>); <patcit id="pcit0008" dnum="US11684541B"><text>11/684,541 filed March 9, 2007</text></patcit> (published as <patcit id="pcit0009" dnum="US2007197103A"><text>US2007197103</text></patcit>); <patcit id="pcit0010" dnum="US11684546B"><text>11/684,546 filed March 9, 2007</text></patcit> (published as <patcit id="pcit0011" dnum="US2007198029A"><text>US2007198029</text></patcit>); <patcit id="pcit0012" dnum="US11684982B"><text>11/684,982 filed March 12, 2007</text></patcit> (published as <patcit id="pcit0013" dnum="US2007198030A"><text>US2007198030</text></patcit>); <patcit id="pcit0014" dnum="US11736526B"><text>11/736,526 filed April 17, 2007</text></patcit> (published as <patcit id="pcit0015" dnum="US2008262528A"><text>US2008262528</text></patcit>); <patcit id="pcit0016" dnum="US11736537B"><text>11/736,537 filed April 17, 2007</text></patcit> (published as <patcit id="pcit0017" dnum="US2008262532A"><text>US2008262532</text></patcit>); <patcit id="pcit0018" dnum="US11825975B"><text>11/825,975 filed September 10, 2007</text></patcit> (published as <patcit id="pcit0019" dnum="US2008015740A"><text>US2008015740</text></patcit>); <patcit id="pcit0020" dnum="US12344378B"><text>12/344,378 filed 12/26/2008</text></patcit> (published as <patcit id="pcit0021" dnum="US2009299393A"><text>US2009299393</text></patcit>); <patcit id="pcit0022" dnum="US13012727B"><text>13/012,727 filed 1/24/2011</text></patcit> (published as <patcit id="pcit0023" dnum="US2011288572A"><text>US2011288572</text></patcit>); and <patcit id="pcit0024" dnum="US13226222B"><text>13/226,222 filed 9/6/2011</text></patcit> (published as <patcit id="pcit0025" dnum="US2012197285A"><text>US2012197285</text></patcit>). The principles of the invention as discussed herein may be applied to the above referenced cases to produce devices useful in treating ischemic stroke. In other words, the wire-shaped construction of devices according to present invention may assume the shapes disclosed in the above-referenced cases when such a combination is not inconsistent with the features described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

0033<ul id="ul0001" list-style="none" compact="compact"><li>Each of the following figures diagrammatically illustrates aspects of the disclosure. Variation of the invention, as defined by the claims, from the aspects shown in the figures is contemplated.</li><li><figref idref="f0001">Fig. 1</figref> illustrates an example of a device according to the present invention when used in a system for removing obstructions from body lumens.</li><li><figref idref="f0002">Figs. 2A to 2C</figref> illustrate working ends of various coverable retrieval devices.</li><li><figref idref="f0003">Figs. 2D and 2E</figref> show variations of retrieval devices.</li><li><figref idref="f0004">Fig. 2F</figref> shows an independent eversible cover on a delivery sheath.</li><li><figref idref="f0005">Figs. 3A to 3C</figref> illustrates an example of a coverable retrieval device where the cover everts about the retrieval structure.</li><li><figref idref="f0006 f0010">Fig. 4A to 4I</figref> illustrates an example where an improved retrieval device with passive protection retrieves a clot from tortuous anatomy.</li><li><figref idref="f0011">Figs. 4J and 4K</figref> illustrate examples of an obstruction or other material captured within a retrieval device with a cover further protecting the loaded retrieval device.</li><li><figref idref="f0012">Fig. 5A</figref> illustrates a retrieval device having a retrieval structure adjacent to a double layer cover.</li><li><figref idref="f0012">Fig. 5B</figref> shows a funnel with a free end that tapers down about the delivery wire.</li><li><figref idref="f0012">Figs. 5C and 5D</figref> show a fixed end of a cover that is pre-shaped to reduce the force required to evert the cover wall.</li><li><figref idref="f0012">Fig. 5E</figref> shows alternate variation of a passive cover integrated into a retrieval device.</li><li><figref idref="f0013">Fig. 5F</figref> illustrates a cover having a pre-set flattened cover wall at a fixed end of the retrieval structure.</li><li><figref idref="f0013">Figs. 5G to 5I</figref> illustrate various layered covers.</li><li><figref idref="f0013">Fig. 5J</figref> shows a cover that is constructed directly onto the retrieval structure rather than the delivery shaft.</li><li><figref idref="f0014">Figs. 5K and 5L</figref> show a variation of a cover and retrieval device where the cover is first mounted in a distal direction and then inverted in a proximal direction.</li><li><figref idref="f0015 f0016 f0017 f0018">Figs. 6A to 6L</figref> illustrate a variation of covers for use as describe herein.</li><li><figref idref="f0019">Figs. 7A to 7C</figref> show additional variations of covers.</li><li><figref idref="f0020">Fig. 8</figref> illustrates a variation of a proximal and distal end of an additional retrieval device.</li><li><figref idref="f0021">Figs. 9A to 9C</figref> illustrate wires of different constructions within a delivery wire or shaft.</li><li><figref idref="f0022">Figs. 10A to 10E</figref> illustrate additional variations of covers for use as described above.</li><li><figref idref="f0023">Figs. 11A to 11C</figref> illustrate additional variations of covers for use with the devices and methods described herein.</li><li><figref idref="f0024 f0025 f0026">Figs. 12A to 12E</figref> illustrate various stent designs for increasing the ability of a stent to adhere to an occlusion within a vessel.</li><li><figref idref="f0027">Fig. 12G</figref> illustrates a proximal end of the stent structure.</li></ul>

DETALED DESCRIPTION

0034It 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.

0035<figref idref="f0001">Fig. 1</figref> illustrates a system <b>10</b> for removing obstructions from body lumens as described herein. In the illustrated example, this variation of the system <b>10</b> is suited for removal of an obstruction in the cerebral vasculature. As stated herein, the present devices and methods are useful in other regions of the body including the vasculature and other body lumens or organs. For exemplary purposes, the discussion shall focus on uses of these devices and method in the vasculature.

0036It is noted that any number of catheters or microcatheters maybe used to locate the catheter/microcatheter <b>12</b> carrying the obstruction removal device <b>200</b> at the desired target site. Such techniques are well understood standard interventional catheterization techniques. Furthermore, the catheter <b>12</b> may be coupled to auxiliary or support components <b>14</b>, 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 <b>10</b> described herein.

0037In 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.

0038<figref idref="f0002">Fig. 2A</figref> illustrates a working end of a coverable retrieval device <b>100.</b> Typically, the device includes a capturing or retrieval structure <b>200.</b> In the illustrated example, the retrieval structure <b>200</b> comprises an elongated stent structure. However, unless specifically noted, the capturing structure can comprise any number of devices, including but not limited to a filter, an atherectomy device, a rotational cutter, an aspiration catheter.

0039The retrieval structure <b>200</b> is located at a distal end of a delivery wire <b>202.</b> In one variation, the retrieval structure <b>200</b> can be permanently affixed to the delivery wire <b>200</b> by such methods including, but not limited to adhesive bonding, soldering, welding, polymer joining, or any other conventional method. In some variations, the retrieval device <b>200</b> can be formed from one or more wires forming the delivery wire 202 or shaft <b>202.</b> The delivery wire <b>202</b> can have sufficient column strength such that it can axially advance and retract the device <b>100</b> within the vasculature as the physician manipulates a non-working end of the delivery wire <b>202</b> outside of the body. Accordingly, the delivery wire <b>202</b> should have a length that is sufficient to extend from the target area, e.g., the cerebral vasculature, to the entry point on the body. Alternatively, additional variations of the device <b>100</b> can allow for the use of a support member or catheter that positions the retrieval structure <b>200</b> as needed. Additional features of the retrieval structure <b>200</b> can be found in the commonly assigned patents and applications cited herein an incorporated by reference.

0040The coverable retrieval device <b>100</b> further includes a cover <b>300</b> (also referred to as a funnel or sheath) affixed relative to a proximal end <b>206</b> of the retrieval structure <b>200.</b> By being affixed relative to a proximal end <b>206</b>, a distal end <b>204</b> of the retrieval structure <b>200</b> can move relative to the cover <b>300</b> so that the cover <b>300</b> everts over the proximal end <b>206</b> of the structure <b>200</b> when the cover <b>300</b> is expanded within a vessel and as the structure <b>200</b> is withdrawn into the distal end <b>302</b> of the cover <b>300.</b> This mechanism is discussed in detail below.

0041<figref idref="f0002">Figs. 2B and 2C</figref> illustrate alternative variations of a coverable retrieval device <b>100.</b> As shown in <figref idref="f0002">Fig. 2B and 2C</figref>, the distal end <b>302</b> of the cover <b>300</b> can be spaced from the proximal end <b>206</b> of the retrieval structure <b>200.</b> Alternatively, the distal end <b>302</b> of the cover <b>300</b> can extend over a portion of the retrieval structure <b>200.</b> In some variations, at least a section of the cover <b>300</b> expands to a greater diameter than a diameter of the retrieval structure <b>200.</b> This allows the cover <b>300</b> to expand to a vessel wall where the vessel holds the cover stationary while the device is pulled proximally through the cover to evert the cover. In alternate variations, the cover <b>300</b> expands to the same or lesser diameter than the retrieval structure <b>200</b> or other device.

0042<figref idref="f0003">Fig. 2D</figref> shows a retrieval device <b>100</b> with a catheter <b>112</b> (usually a microcatheter). The retrieval device <b>100</b> can comprise a single unitary device of a cover <b>300</b> and retrieval structure <b>200</b> (in this case the retrieval structure is an elongated stent structure). One benefit of a unitary device is that additional devices complicates the procedure and can increase the duration of what is ordinarily a time sensitive procedure. The retrieval device <b>100</b> can be positioned through the catheter <b>112</b> that includes a hub <b>114.</b> As a result, the physician only needs to manipulate the unitary retrieval device <b>100</b> and the catheter/microcatheter <b>112.</b> The retrieval device <b>100</b> is loaded into the catheter <b>112</b> for placement at the target site. In addition, the retrieval device can be reloaded if the procedure must be repeated. The cover <b>300</b> and retrieval structure <b>200</b> described herein can comprise any construction described herein or as known by those skilled in the art.

0043<figref idref="f0003">Fig. 2E</figref> shows a retrieval device <b>100</b> with a cover <b>300</b> and retrieval device <b>200</b> with a radiopaque marker <b>305</b> therebetween. As shown, variations of the device <b>100</b> do not require a catheter or microcatheter.

0044<figref idref="f0004">Fig. 2F</figref> illustrates an eversible cover <b>300</b> located on a sheath <b>330</b> having a lumen <b>332</b> extending therethrough. A separable retrieval device <b>200</b> can be coupled to the cover <b>300</b> and sheath <b>330</b> by inserting the wire <b>202</b> of the cover retrieval device <b>200</b> through the lumen <b>332</b> of the sheath <b>330.</b> In this variation, the eversible cover <b>300</b> can be used with any number of different interventional tools. The separate devices can be assembled prior to delivery into the patient. Alternatively, the devices can be positioned within the body and subsequently joined once the retrieval device <b>200</b> engages the target area.

0045<figref idref="f0005">Fig. 3A</figref> illustrates an example of a coverable retrieval device <b>100</b> where the cover <b>300</b> is in the process of everting about the retrieval structure <b>200.</b> As shown, arrow <b>50</b> illustrates a force applied on the wire <b>202</b> in a proximal direction. Arrows <b>52</b> illustrate a resistance force applied by the friction of the expanded cover <b>300</b> against a vessel or similar wall. This friction force <b>52</b> prevents or resists proximal movement of the free end <b>304</b> of the cover <b>300</b> while the fixed end <b>302</b> moves in a proximal direction with the proximal end <b>206</b> of the retrieval structure <b>200.</b> This action causes a wall <b>306</b> of the cover <b>300</b> to evert over the retrieval structure <b>200.</b> Ultimately, and as shown in <figref idref="f0005">Fig. 3B</figref>, the free end <b>304</b> of the cover <b>300</b> ends up distally over the fixed end <b>302.</b> As shown, the wall of the everted cover <b>300</b> provides a safety type cover for the retrieval device <b>200.</b> In additional variations, the fixed end <b>302</b> of the cover can actually be slidable or moveable along the delivery wire <b>202.</b> However, the similar principle as discussed above shall apply to cause everting of the cover <b>300</b> over the retrieval structure <b>200.</b>

0046<figref idref="f0005">Fig. 3C</figref> illustrates another variation of a coverable retrieval device <b>100</b> after the cover <b>300</b> is everted about the retrieval structure <b>200.</b> In this variation, the free end <b>304</b> of the cover <b>300</b> ends up distally of the fixed end <b>302</b> and tapers or collapses towards the free end <b>304.</b> The cover <b>300</b> can be shape set so that prior to eversion the cover is as shown above where the forces acting on the cover wall <b>306</b> expand outwards, but after eversion the forces on the cover wall <b>306</b> cause the tapering or collapsing as shown in <figref idref="f0005">Fig. 3C</figref>.

0047In accordance with the illustrations discussed above, the cover <b>300</b> can be made so that the cover wall <b>306</b> is atraumatic when dragged across a lumen wall. The cover can be manufactured from any number of materials including a fabric, a reinforced fabric, a braid, weave, or any such material that allows for expansion against a wall of the body lumen or vessel as well as to allow everting of a wall <b>306</b> of the cover over the retrieval device <b>200.</b> The cover wall <b>306</b> can also comprise combinations of these materials such as braids of polymer material with metal fibers, soft braids with coil reinforcements or various other combinations.

0048The cover wall can comprise a mesh that can include any medically acceptable materials such as a Nitinol braid. Furthermore, the mesh allows for flow through the vessel or lumen while expanded. However, additional variations of the device can include a solid layer of material substituted for the mesh. Moreover the cover can comprise any number of configurations. For example, the cover can comprise a single layer wall or a multi layer wall, the open end of the cover could be made to have terminated ends such as by using continuous wire loops formed during the braiding process. Alternatively, the ends can be cut and then terminated by encasing in polymer, laser welds, or by folding inward for a discreet length and then terminating

0049In one example, the cover <b>300</b> comprises a continuous wire construction as described in earlier commonly assigned patent applications incorporated by reference. In one variation the cover <b>300</b> comprises a finely braided wire, such as 48-96 wires of 0.0127mm (.0005") to 0.0508mm (0.002") diameter fine Nitinol wire or similar. Additionally, the wire can comprise cobalt chromium, stainless steel, or similar, or drawn filled tube (dft) with platinum core. In additional variations, a flat wire or oval wire can be used. The wire does not need to be uniform. Instead, a number of different types of wires can be used. Some of the individual wires could be platinum alloys for added radiopacity.

0050<figref idref="f0006 f0010">Fig. 4A to 4I</figref> illustrates an example where an improved retrieval device <b>100</b> with passive protection retrieves a clot <b>2</b> from tortuous anatomy. <figref idref="f0006">Fig. 4A</figref> illustrates a clot <b>2</b> that obstructs blood flow in a vessel <b>6.</b> As noted herein, the vessel <b>6</b> can comprise any vessel in cerebral vasculature, coronary or peripheral vasculature. Alternatively, the device and methods for use are not limited to use in the vasculature . Variations of the principles, concepts, method and devices described herein can be applicable wherever a retrieval device can be used. <figref idref="f0006">Fig. 4A</figref> also illustrates a guide sheath or access catheter <b>108</b> that is advanced within the vessel. During a procedure, the physician will advance the access catheter <b>108</b> as far distally as possible. However, due to the size of the access catheter <b>108</b>, a physician typically positions it a distance away from the obstruction <b>2.</b> As shown, there can be any number of bifurcations <b>8</b> in the vessel <b>6</b> located between the access catheter <b>108</b> and the obstruction <b>2.</b> As discussed herein, in some variations, the access catheter <b>108</b> can be used to remove the obstruction <b>2</b> from the body once the obstruction is captured by a retrieval device. However, the greater the distance between the initial location of the obstruction <b>2</b> and the location of the access catheter <b>108</b>, the greater the risk that the obstruction <b>2</b> can break free from the retrieval device or become dislodged due to anatomic or environmental features, including but not limited to bifurcations, the wall of the lumen, the tortuousity of the anatomy, vessel wall plaque, etc.

0051<figref idref="f0006">Fig. 4B</figref> illustrates an optional catheter <b>112</b> that advances from the access catheter <b>108</b> to the site of the obstruction <b>2.</b> Once at the site, the catheter <b>112</b> can deploy a retrieval device (not shown in <figref idref="f0006">Fig. 4B</figref>) so that the retrieval device can engage the clot <b>2.</b> Alternatively, the catheter <b>112</b> can traverse the obstruction <b>2</b> as shown in <figref idref="f0007">Fig. 4C</figref> and deploy a portion of the retrieval device <b>100</b> distally to the obstruction <b>2.</b> The physician then manipulates the retrieval device <b>100</b> to secure the obstruction <b>2.</b> For example, the physician can deploy the retrieval structure <b>200</b> distally to the obstruction <b>6</b> and withdraw the retrieval structure <b>200</b> proximally to secure the obstruction <b>2.</b> In another variation, the physician can position the retrieval structure <b>200</b> within the catheter <b>2</b> while the catheter <b>112</b> is through or adjacent to the obstruction <b>2.</b> Then, the physician can withdraw the catheter <b>112</b> to expose the retrieval structure <b>200</b> so that it secures to the obstruction <b>2</b> after expansion. In the illustrated example, the retrieval structure <b>200</b> comprises an elongated stent type structure that expands (or is expanded) to enmesh or secure to the obstruction. Although not illustrated, the system can include a distal capture filter or basket as described in any of the commonly assigned applications incorporated by reference herein.

0052Next, as shown in <figref idref="f0008">Fig. 4E</figref>, the physician can further withdraw the catheter <b>112</b> to expose a cover <b>300</b> as described above. In many cases, the physician exposes the cove <b>300</b> once the retrieval structure <b>200</b> is engaged with the obstruction <b>2.</b> This sequential process allows for easier repositioning of the retrieval structure <b>200</b> if necessary. Alternatively, the cover <b>300</b> can be deployed prior to engaging the retrieval structure <b>200</b> with the obstruction <b>2.</b> If necessary, the physician can apply a proximal force on the delivery wire <b>202</b> while withdrawing the catheter <b>112</b> to prevent inadvertent movement of the obstruction <b>2</b> and retrieval device <b>200.</b>

0053<figref idref="f0008">Fig. 4F</figref> illustrates the stage with a fully exposed the cover <b>300</b> and a catheter <b>112</b> moved closer towards the access sheath <b>108.</b> As shown, the free end <b>304</b> of the cover <b>300</b> is proximal to fixed end <b>302</b> of the cover <b>300.</b> As also noted above, the cover <b>300</b> can be a shape memory alloy that expands against the walls of the vessel 6 upon reaching body temperature. Alternatively, the cover <b>300</b> can be self expanding upon deployment into the vessel <b>6.</b> In some variations, the cover wall <b>306</b> comprises a porous material or construction that allows blood to continue to flow through the cover <b>300.</b>

0054In addition, some variations of the retrieval device <b>100</b> include a cover <b>300</b> that has at least a section that expands to a greater diameter or dimension than the retrieval structure <b>200.</b> This allows for expansion of the cover <b>300</b> against the wall of the vessel <b>6.</b> In most variation, expansion of the cover <b>300</b> provides sufficient friction against the walls of the vessel to overcome column strength of the cover walls <b>306</b> allowing for everting of the cover walls <b>306</b> over the retrieval structure <b>200</b> and obstruction <b>2</b> as discussed herein. As noted above, in alternate variations the cover <b>300</b> can expand a diameter or dimension that is equal to or less than the retrieval structure <b>200.</b>

0055<figref idref="f0009">Figs. 4G</figref> illustrates proximal movement of the delivery wire <b>202</b>, which causes proximal translation of the obstruction <b>2</b> and retrieval structure <b>200.</b> Because the cover <b>300</b> is expanded against the walls of the vessel <b>6</b> the free end <b>304</b> of the cover <b>300</b> does not move or moves less than the fixed end <b>306</b> of the cover <b>300.</b> The fixed end <b>306</b> moves with the obstruction <b>2</b> and retrieval structure <b>200</b> in a proximal direction causing the cover walls <b>306</b> to evert over the obstruction <b>2</b> and retrieval structure <b>200.</b> Unlike a conventional funnel, the everting cover functions similar to a conveyor belt type movement as the obstruction and retrieval structure move together. This action allows for a passive type of protection since cover <b>300</b> does not need to be actuated over the obstruction <b>2</b> and retrieval structure <b>200</b> and can be performed in a quick manner by simply withdrawing the deployed retrieval device <b>100.</b>

0056<figref idref="f0009">Fig. 4H</figref> illustrates a stage where the fixed end <b>306</b> of the cover <b>300</b> is now proximal to the free end <b>304.</b> As shown, the everted cover <b>300</b> forms a protective sheath or cover over the obstruction <b>2</b> and the retrieval structure <b>200.</b><figref idref="f0009">Fig. 4H</figref> also illustrates how the cover <b>300</b> protects the obstruction <b>2</b> and retrieval structure <b>200</b> as they are pulled along the vessel and navigate the tortuous anatomy, walls of the vessel, as well as bifurcations <b>8.</b> The cover <b>300</b> and cover wall <b>306</b> also protects the vasculature from the surface of the retrieval structure <b>200</b> and obstruction <b>2.</b>

0057<figref idref="f0010">Fig. 4I</figref> shows the obstruction <b>2</b> and retrieval structure <b>200</b> protected by the cover <b>300</b> as the retrieval device <b>100</b> is positioned against or within the access catheter <b>108</b> in preparation for removal from the body. The retrieval device <b>100</b> can remain outside of the access catheter <b>108</b> as the physician removes both devices from the body. Alternatively, the cover <b>300</b> can assist in pulling the retrieval device <b>100</b> and obstruction <b>2</b> into the access catheter <b>108</b> by compressing the obstruction <b>2</b> as it is pulled into the access catheter <b>108.</b>

0058<figref idref="f0011">Figs. 4J and 4K</figref> illustrate examples of an obstruction or other material <b>2</b> captured within a retrieval device <b>2</b> with a cover <b>300</b> further protecting the loaded retrieval device <b>200.</b>

0059<figref idref="f0012 f0013 f0014">Figs. 5A to 5K</figref> show a variety of cover configurations. <figref idref="f0012">Fig. 5A</figref> illustrates a retrieval device <b>100</b> having a retrieval structure <b>200</b> adjacent to a double layer cover <b>300</b> with an exterior wall <b>306</b> and an interior wall <b>308.</b>

0060<figref idref="f0012">Fig. 5B</figref> shows a cover <b>300</b> with a free end <b>304</b> that tapers down about the delivery wire <b>202</b> where the cover <b>300</b> will eventually form a double wall configuration when the cover <b>300</b> everts over the retrieval structure <b>200.</b> The tapered free end <b>304</b> limits the cover <b>304</b> from moving once the retrieval structure <b>200</b> reaches the free end <b>304</b> thereby forming double wall protection over the retrieval structure <b>200.</b>

0061<figref idref="f0012">Figs. 5C and 5D</figref> show how a fixed end <b>302</b> of a cover <b>300</b> can be pre-shaped to reduce the force required to evert the cover wall <b>306</b> or to lower the threshold to trigger passive covering of the retrieval structure by the cover.

0062<figref idref="f0012">Fig. 5E</figref> shows alternate variation of a passive cover <b>300</b> integrated into a retrieval device <b>100.</b> In this variation, the retrieval device <b>100</b> includes a control shaft or wire <b>202</b> to manipulate the working end of the retrieval device <b>100.</b> The cover <b>300</b> floats along the shaft <b>202</b> between two fixed anchors or nodes <b>220</b>, <b>222.</b> The cover <b>300</b> can float or slide between the fixed nodes <b>220</b>, <b>222.</b> The nodes <b>220</b>, <b>222</b> can comprise radiopaque marker bands, glue joints, or any other mechanical obstructions capable of stopping the translation of cover <b>300.</b> When the device <b>100</b> advances through a microcatheter, the rear or proximal node <b>220</b> limits rearward movement of the cover <b>300.</b> When positioned appropriately, the microcatheter can be withdrawn to expose the retrieval device <b>200</b> and cover <b>300</b> as described herein. When the retrieval structure <b>200</b> engages the obstruction (not shown) the retrieval device <b>100</b> can be withdrawn by pulling on the delivery shaft <b>202.</b> While this occurs, the cover <b>300</b>, being expanded against the vessel remains stationary (or moves at a slower rate than the obstruction and retrieval structure <b>200</b> due to the friction against the vessel wall). The retrieval structure <b>200</b> and clot enter the cover <b>300</b>, causing the distal node <b>222</b> to make contact with the near end <b>320</b> of the cover <b>300.</b> This contact causes the retrieval structure <b>200</b> and cover <b>300</b> to translate as an integrated unit. It should be appreciated that the cover could be a single layer or double layer cover, and could have any of the wire design variables and termination variables described herein.

0063<figref idref="f0013">Fig. 5F</figref> illustrates a cover having a pre-set flattened cover wall <b>304</b> at a fixed end <b>302</b> that is spaced from a proximal end of the retrieval structure <b>200.</b><figref idref="f0013">Figs. 5G to 5I</figref> illustrate various layered covers <b>300.</b> The layered covers allow for shortening the axial length of the cover and therefore shortens the required translation length. Layering of the cover wall <b>306</b> allows for a shortened deployed length of the cover <b>300</b> when deployed in the vessel or body structure. As the cover <b>300</b> everts over the retrieval structure <b>200</b> the layered wall <b>306</b> extends. As a result, shortening the length reduces the length that the cover <b>300</b> extends into the proximal vessels and reduces the length of that the retrieval structure <b>200</b> must travel to become protected by the cover <b>300.</b> This also helps shorten the distance required to move the device <b>100</b> to complete eversion of the cover <b>300.</b>

0064<figref idref="f0013">Fig. 5J</figref> shows a cover <b>300</b> that is constructed directly onto the retrieval structure <b>200</b> rather than the delivery shaft <b>202.</b> This construction also assists in reducing the distance necessary to complete passive protection of the retrieval structure by the cover.

0065<figref idref="f0014">Fig. 5K</figref> show a variation of a cover <b>300</b> that is mounted in a distal direction over the retrieval device <b>200</b> and then everted in a proximal direction over the wires or shaft <b>202</b> as shown by arrows <b>230.</b> Once everted, as shown by <figref idref="f0014">Fig. 5L</figref>, the device <b>100</b> is ready for deployment as discussed herein.

0066<figref idref="f0015">Figs. 6A to 6B</figref> illustrate a variation of a cover <b>350</b> for use as describe herein. Additionally, the cover <b>350</b> can be used with any obstruction retrieval device not limited to the retrieval baskets and stents described herein. The covers <b>350</b> disclosed herein can be used where the physician desires to shield the obstruction being removed from the frictional effects of the arteries or from the local anatomy (e.g., branching vessels, tortuous anatomy, or other substances on the vessel walls). In use, the covers can be sized for use with guide catheters, micro-catheters, and/or distal access catheters. The covers can include any number of radiopaque marker bands to allow non-invasive imaging of the device (see marker <b>390</b> affixed between cover <b>350</b> and shaft <b>212</b> in <figref idref="f0019">Fig. 7B</figref> as one example). In any case, once the retrieval device captures a clot or obstruction, as described above, the device and clot are protected by the cover so that the cover eliminates or reduces direct contact between the interior of the wall of the vessel and the clot.

0067<figref idref="f0015">Figs. 6A to 6C</figref> show a variation in which a cover is created from one or more mesh tubes <b>372.</b><figref idref="f0015">Fig. 6B</figref> illustrates inversion of the tube <b>372</b> so that a first end <b>374</b> is drawn over the tube <b>372</b> towards a second end <b>376.</b> As shown in <figref idref="f0015">Fig. 6C</figref>, this creates a double walled cover having an exterior wall <b>378</b> separated from an interior wall <b>380.</b> In one example, such a spacing or gap could range between 0.0254mm (0.001 inches) to 2.54mm (0.100 inches). However, any range is contemplated within alternative variations of the device. In some variations the inverted cover <b>350</b> is heat set to maintain a separation between layers or walls <b>378 380</b> of the cover <b>350.</b> Typically, if the cover <b>350</b> is not created from a radiopaque material, a marker band will be placed on the proximal end <b>376</b> and adjacent to a shaft or catheter to which the cover <b>350</b> is attached. In some variations the construction of the mesh material is compliant to allow for movement of a first part of the mesh relative to a second part of the mesh through compression and expansion of the mesh material. In such a case, the individual strands forming the mesh are moveable relative to one another to cause the mesh to be naturally compliant. Accordingly, this construction permits the inner wall <b>380</b> to move or deflect with the retrieval device and/or obstruction as the device is withdrawn into the cover <b>350.</b> In some variations, both ends of the mesh <b>374</b> and <b>376</b> are affixed to the catheter,shaft or wire.

0068In many variations, the cover mesh is selected to minimize friction when the interior layer <b>380</b> moves against the exterior layer <b>378.</b> For example, the braid pattern, wire, wire diameter, angle of the braid and or other features can be selected to reduce friction between the outer layer <b>378</b> and inner layer <b>380.</b> This permits the inner layer <b>380</b> to move proximally with a retrieval device while the outer layer remains stationary. Again, as discussed above, the construction of the mesh permits compression and expansion of the mesh layer to permit movement of the inner layer while the outer layer remains affixed when engaged against the vessel wall. In certain variations, the cover is heat set so that the inner layer has cushioning and the ability to deflect to assist in movement of the inner layer. <figref idref="f0012">Fig. 5C</figref> also illustrates a coer <b>350</b> having a tapered design.

0069<figref idref="f0016 f0017 f0018">Figs. 6D to 6L</figref> illustrate additional variations of cover construction to produce covers having more than two walls. For example, a mesh tube <b>372</b> is everted or drawn over a second end <b>376</b> in the direction <b>420.</b> As shown in <figref idref="f0016">Fig. 6E</figref> this produces a dual layer cover having a open ends <b>422</b> and <b>424</b> and a folded end <b>426.</b> The dual layer tube is then folded over again in the direction <b>420.</b> This creates a cover construction with an exterior layer <b>378</b> and an interior layer <b>380</b> as well as a first intermediate layer <b>381</b> and a second intermediate layer <b>383.</b> As shown in <figref idref="f0016">Fig. 6F</figref>, the cover can be set to assume the tapered shape having an opening at the first end <b>374</b> that is flared with the ends of the mesh at the second end <b>372</b>, which are ultimately affixed to a shaft, wire or other catheter device as described herein.

0070<figref idref="f0017">Fig. 6G</figref> illustrates another example of a cover construction. As shown, a first mesh tube <b>372</b> is placed coaxially with a second tube <b>372.</b> The concentric tubes are then everted in direction <b>420</b> to produce a four layer cover. As shown in <figref idref="f0017">Fig. 6H</figref>, the cover can comprise an interior mesh layer <b>380</b>, and exterior mesh layer <b>378</b> as well as any number of intermediate layers <b>381</b>, <b>383</b> depending on the number of tubes that are initially used. The second end <b>372</b> of the cover <b>350</b> includes four unconnected ends of the mesh tubes that can be affixed to a shaft or tube as discussed herein, while the first end <b>374</b> of the cover 350 can be shape set to taper from the opening.

0071<figref idref="f0018">Figs. 6I to 6L</figref> illustrate another example of the construction of a multi-wall cover. As shown in <figref idref="f0018">Fig. 6I</figref>, a first end <b>374</b> of a mesh tube <b>372</b> is everted over and beyond a second end <b>376</b> in direction <b>420</b> to produce the configuration of <figref idref="f0018">Fig. 6J</figref>. Next, the first end <b>374</b> is everted or folded back in direction <b>420</b> to produce the configuration of <figref idref="f0018">Fig. 6K</figref>. Finally, the first end <b>374</b> is folded again in direction <b>420</b> so that the ends <b>374</b> and <b>376</b> are even to produce the cover configuration shown in <figref idref="f0018">Fig. 6K</figref>. Again, one end of the cover <b>350</b> can be set to form the tapered shape while the other respective end can be affixed to a catheter or shaft.

0072Although the covers of the present disclosure are presented without additional structures, it should be noted that these covers are coupled with a shaft or other member so that the cover can be advanced within the target anatomy to assist in removal of a device, structure, or debris from the site.

0073<figref idref="f0019">Figs. 7A to 7C</figref> show addition variations of covers <b>350.</b><figref idref="f0019">Fig. 7A</figref> illustrates a cover in which the cover wall as defined by the inner layer <b>380</b> and outer layer <b>378</b> is set in a shape that varies along a length of the cover. For example, the end adjacent to the cover opening <b>382</b> can be set to a bulbous shape. Such a configuration assists in maintaining separation of layers <b>378</b> and <b>380</b>, which aids in re-entry of the retrieval device. Additional configurations of cover walls that vary in thickness are within the scope of this disclosure.

0074One of the benefits of using a cover <b>350</b> as described herein is that the cover reduces flow through the vessel when deployed so that the retrieval device can remove the obstruction without the full force of the flow of blood opposing the obstruction. Typically, conventional devices relied upon the use of an inflated balloon to obstruct flow. However, use of a cover eliminates the need for total occlusion of blood flow. <figref idref="f0019">Fig. 7B</figref> illustrates a further improvement on a cover <b>350</b> that aids in flow reduction. As shown, the cover <b>350</b> includes a dense region <b>386</b> and a relatively less dense region <b>384.</b> This configuration permits greater blood flow through the region <b>385</b> while region <b>386</b> reduces or prevents blood flow. Furthermore, the distal section of the cover is more flexible and conformable. Additional mesh layers can be added to any of the cover designs to alter flow characteristics or even provide reinforcement to the cover. Alternatively, or in combination, the braid density can be altered to adjust the porosity of the braid at different sections. Furthermore, additional braid layers can also be used to affect porosity of portions of the cover or even the entire cover. Deployment of a cover can reduce blood flow by 30% to 40%. Adding additional layers or coatings can additionally reduce flow.

0075<figref idref="f0019">Fig. 7C</figref> shows another variation of a cover <b>350</b> in which the mesh partially or totally is obscured using a polymeric coating <b>388</b> that reduces the permeability of the mesh design. Furthermore, drugs or other substances can be placed within the cover wall of any of the covers or can be deposited on the cover using the polymeric coatings. In some examples, the covers described herein can range from a length of 10 mm up to 50 mm. The OD at the opening of the cover can range from 7 mm and could range between 4 mm to 10 mm. Again, any range of dimensions is contemplated within the disclosure.

0076The covers described herein can further be stacked on a device. For example, two or more covers can be placed on a device to provide added protection.

0077The cover/rentry devices described herein can be constructed of any material currently used in vascular applications, including those discussed above. Furthermore, fabrication of the cover from a DFT material can provide additional benefits as the entire cover remains radiopaque and can be imaged non-invasively. Furthermore, the covers can be provided with any type of medicament or bioactive substance either in a polymer that coats the mesh or in a delivery agent within the mesh or between layers. Such substances include tpa, urokinase, IIb/IIIa inhibitors, and other clot disruptors or inhibitors.

0078<figref idref="f0020">Fig. 8</figref> illustrates another variation of a retrieval device <b>400</b> including a distal capture portion <b>426</b> coupled to one or more leading wires in the form of a main bundle <b>402.</b> The main bundle extends through a sheath <b>106</b> that includes a proximal capture portion <b>460.</b> The configuration of the retrieval device <b>400</b> can incorporate the proximal and distal capture portions discussed herein as well as various other configurations discussed in the commonly assigned patent applications noted above.

0079An end <b>464</b> of the proximal capture portion <b>460</b> is affixed to a distal end of the sheath <b>106.</b> However, as noted above, other variations are within the scope of the disclosure. The main bundle <b>402</b> can optionally terminate at a handle <b>442.</b> As noted above, in certain variations, the main bundle is joined to a stiffer wire or stiffer bundle of wires. This allows the device <b>400</b> to have a very flexible distal section with a relatively stiffer proximal section. The device <b>400</b> can have a proximal bundle <b>403</b> that comprises either the exposed wires or a covering/tube over the wires. In certain variations, the bundle or wire <b>402</b>, <b>403</b> can be encapsulated with a coating. The device also includes a cover <b>300</b> adjacent to the retrieval device.

0080The proximal end of the sheath <b>106</b> includes a sheath handle <b>444.</b> As discussed herein, axial movement of the bundle <b>402</b> or proximal bundle <b>403</b> (typically at the handle <b>442</b>) results in movement <b>126</b>, or translation of the bundle within the sheath <b>106.</b> This action moves the distal capture portion <b>426</b> (as shown by arrows <b>126</b>). In certain variations, the device <b>400</b> is loaded into a microcatheter (not shown but discussed above) that is delivered to the site of the obstruction and crosses the obstruction.

0081In some variations, the sheath hub <b>444</b> includes one or more locking hubs <b>446.</b> Where actuation (either axial or rotational) of the locking hub <b>446</b> locks the main bundle <b>402</b> relative to the sheath handle <b>444</b> and sheath <b>106.</b> It follows that such locking action also locks the distal capture portion <b>426</b> relative to the proximal capture portion <b>460.</b> A variety of methods can be employed to increase a frictional interference between the locking hub <b>446</b> and the proximal bundle <b>403.</b> As a result, when a physician determines a length of an obstruction, the physician can set a spacing between the capturing portions <b>426 460</b> by locking the proximal bundle 403 relative to the sheath hub <b>444.</b> Accordingly, the proximal bundle 403 can include any type of incremental markings to allow the physician to readily determine a spacing of the capturing portions. As illustrated, the sheath hub <b>444</b> can include additional injection ports to deliver fluid or other substances through the sheath <b>106.</b>

0082As noted above, the device <b>400</b> can be used with a micro-catheter. In those variations it is important that the device <b>400</b> is loaded without damaging the distal bundle <b>402</b>, capture portions <b>426 460</b>, and/or sheath <b>106.</b> As a result, the device <b>400</b> can include an optional cover <b>486</b> that reduces the proximal capture portion <b>460</b> (and /or the distal capture portion <b>426</b>) for loading within the microcatheter and/or sheath <b>106.</b>

0083Another variation of the device <b>400</b> includes an insertion tool <b>480</b> slidably affixed to the sheath <b>480.</b> Because variations of the device <b>400</b> can be extremely flexible, the insertion tool <b>480</b> can be used to provide column strength to the sheath <b>106</b>, bundle <b>402</b> or other components as the device <b>400</b> is pushed into the microcatheter. The insertion tool comprises a rigid section <b>482</b> and a frictional coupler <b>484.</b> The rigid section <b>282</b> has a column strength that supports the device <b>400</b> to prevent buckling. The frictional coupler <b>484</b> can be a flexible material that allows an operator to squeeze or grip the coupler <b>484</b> to create a temporary frictional interface between the loading tool <b>480</b> and the device <b>400</b> (typically the sheath <b>106</b>)<b>.</b> Such an action allows axial advancement of the device <b>400</b> as the loading tool <b>480</b> is advanced into the microcatheter. Once the rigid section <b>482</b> is fully inserted into the microcatheter, the operator releases the frictional coupler <b>484</b> and can withdraw the loading tool <b>480</b> from the catheter without withdrawing the device <b>400.</b> The insertion tool <b>480</b> can also include an optional loading tube <b>486</b> slidably coupled to the rigid section <b>482.</b> When used, the cover <b>486</b> can withdraw the proximal and distal capturing portion <b>226 260</b> within the loading tube <b>486.</b> The loading tube <b>486</b> then couples to a microcatheter allowing the capturing portions to advance therein as the rigid section <b>482</b> and frictional coupler <b>484</b> advance the device <b>400</b> relative to the loading tube <b>486.</b>

0084<figref idref="f0021">Figs. 9A to 9C</figref> show cross sectional views taken along the line 9A-9A in <figref idref="f0002">Fig. 2A</figref>. As shown, the wire form construction described herein allows for a number of configurations depending on the particular application. For example, the individual wires <b>254</b> (as discussed herein) may themselves comprise a bundle of smaller wires or filaments. In addition, the wires can be selected from materials such as stainless steel, titanium, platinum, gold, iridium, tantalum, Nitinol, alloys, and/or polymeric strands. In addition, the wires used in a device may comprise a heterogeneous structure by using combinations of wires of different materials to produce a device having the particular desired properties. For example, one or more wires in the device may comprise a shape memory or superelastic alloy to impart predetermined shapes or resiliency to the device. In some variations, the mechanical properties of select wires can be altered. In such a case, the select wires can be treated to alter properties including: brittleness, ductility, elasticity, hardness, malleability, plasticity, strength, and toughness.

0085The device may include a number of radiopaque wires, such as gold and platinum for improved visibility under fluoroscopic imaging. In other words, any combination of materials may be incorporated into the device. In addition to the materials, the size of the wires may vary as needed. For example, the diameters of the wires may be the same or may vary as needed.

0086In addition, the individual wires may have cross-sectional shapes ranging from circular, oval, d-shaped, rectangular shape, etc. <figref idref="f0021">Fig. 9A</figref> illustrates one possible variation in which a number of circular wires <b>254</b> are included around another larger wire <b>256.</b> Moreover, the device is not limited to having wires having the same cross-sectional shape or size. Instead, the device can have wires having different cross-sectional shapes. For example, as shown in <figref idref="f0021">Fig. 9B</figref>. one or more wires <b>256</b> can have a different cross-sectional shape or size than a reminder of the wires <b>254.</b> Clearly, any number of variations is within the scope of this disclosure. This construction can apply to the retrieval portion, capturing portion and/or the covering portion of the device.

0087To illustrate one such example, a device can have 8-12 wires made of 0.0762mm (.003") round superelastic material (e.g., Nitinol). The device may additionally have 2-4 wires made from 0.0508mm (.002") platinum for fluoroscopy. Of the 8-12 Nitinol wires, 1-4 of these wires can be made of a larger diameter or different cross-section to increase the overall strength of the device. Finally, a couple of polymer fibers can be added where the fibers have a desired surface property for clot adherence, etc. Such a combination of wires provides a composite device with properties not conventionally possible in view of other formation means (such as laser cutting or etching the shape from a tube or joining materials with welds, etc.). Clearly, any number of permutations is possible given the principles of the invention.

0088In another example, the device may be fabricated from wires formed from a polymeric material or composite blend of polymeric materials. The polymeric composite can be selected such that it 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't affect the surrounding tissues) allowing the device to increase in stiffness so that it doesn't stretch as the thrombus is pulled out. For example, shape memory polymers would allow the device to increase in stiffness.

0089In another variation, one or more of the wires used in the device may comprise a Drawn Filled Tube (DFT) such as those provided by Fort Wayne Metals, Fort Wayne, Indiana. As shown in <figref idref="f0021">Fig. 9C</figref>, such a DFT wire <b>252</b> comprises a first material or shell <b>258</b> over a second material <b>260</b> having properties different from the outer shell. While a variety of materials can be used, one variation under the present devices includes a DFT wire having a superelastic (e.g., Nitinol) outer tube with a radiopaque material within the super-elastic outer shell. For example, the radiopaque material can include any commercially used radiopaque material, including but not limited to platinum, iridium, gold, tantalum, or similar alloy. One benefit of making a capturing portion from the DFT wire noted above, is that rather than having one or more markers over the capturing portion, the entire capturing portion can be fabricated from a super-elastic material while, at the same time, the super-elastic capturing portion is made radiopaque given the core of radiopaque material within the super-elastic shell. Clearly, any composite DFT wire <b>252</b> can be incorporated into the system and capturing portions described herein.

0090Another aspect applicable to all variations of the devices is to configure the devices or portions thereof that engage the obstruction to improve 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 wires may be coated with a hydrogel or adhesive that bonds to a thrombus. Accordingly, as the device secures about a clot, the combination of the additive and the mechanical structure of the device may improve the effectiveness of the device in removing the obstruction. Coatings may also be combined with the capturing portions or catheter to improve the ability of the device to encapsulate and remove the obstruction (e.g., a hydrophilic coating).

0091Such improvements may also be mechanical or structural. Any portion of the capturing portion can have hooks, fibers, or barbs that grip into the obstruction as the device surrounds the obstruction. The hooks, fibers, or barbs <b>370</b> can be incorporated into any portion of the device. However, it will be important that such features do not hinder the ability of the practitioner to remove the device from the body.

0092In addition to additives, the device can be coupled to an RF or other power source (such as <b>14</b> or <b>16</b> in <figref idref="f0001">Fig. 1</figref>), 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<figref idref="f0022">Figs. 10A to 10E</figref> illustrate additional variations of covers <b>300</b> for use as described above. For example, as show in <figref idref="f0022">Fig. 10A</figref>, a cover <b>300</b> can comprise a single wire, coil, or laser cut tube <b>350.</b> Alternatively, as shown in <figref idref="f0022">Fig. 10B</figref>, the cover <b>300</b> can comprises two or more <b>350</b>, <b>352</b> wires or coils. <figref idref="f0022">Fig. 10C</figref> shows a cover <b>300</b> comprising a coil <b>350</b> inside a mesh structure <b>354.</b> A variation of the device shown in <figref idref="f0022">Fig. 10C</figref> can include a compliant atraumatic mesh <b>354</b> that is radially supported by the coil (whether interior or exterior to the mesh). The coil <b>350</b> provides the outward force against the vessel. <figref idref="f0022">Fig. 10D</figref> illustrates a polymeric film or membrane <b>356</b> coupled to a coil <b>350.</b> The polymeric film <b>356</b> can be permeable to fluid flow or impermeable. <figref idref="f0022">Fig. 10E</figref> illustrates a dual layer braid construction having an inner braid <b>358</b> and an outer braid <b>360.</b> The braids can be constructed to have unique properties. For example, the inner braid <b>358</b> can be composed of fewer wires or larger diameter wires, such that it provides an expansion force against the vessel wall. The outer braid <b>360</b> can comprise a softer construction and increased compliance. Accordingly, it can be comprised of a number of smaller diameter wires having a denser pattern to provide increased surface area to protect the obstruction as it is removed from the body. Alternatively, these two constructional elements (e.g., braids of varying diameters) can be combined into a single layer or even multiple layers for the cover.

0094<figref idref="f0023">Fig. 11A</figref> illustrates yet another variation of a device <b>100</b> having a retrieval structure <b>200</b> and cover <b>300</b> where the cover is simply fabricated from the same material as the retrieval structure so long as it functions as described herein. The variation can optionally include one or more barbs <b>370</b> to increase resistance against a vessel wall.

0095<figref idref="f0023">Fig. 11B and 11C</figref> illustrate a variation where the cover 300 comprises a balloon material. <figref idref="f0023">Fig. 11B</figref> illustrates the balloon cover 370 prior to deployment. <figref idref="f0023">Fig. 11C</figref> illustrates the balloon cover 370 once deployed.

0096The retrieval devices described herein can optionally comprise elongated stents 400 as shown in <figref idref="f0024 f0025 f0026">Figs. 12A to 12E</figref>. These stents 400 can include any number of features to better assist the stent 400 in becoming enmeshed into the obstruction. For example, <figref idref="f0024">Fig. 12A</figref> illustrates a variation of a stent 400 affixed to a shaft 412. As noted herein, the shaft 412 can include a lumen extending therethrough. Alternatively, the shaft 412 can include a solid member with the stent 400 affixed to a distal end thereof. The variation shown in <figref idref="f0024">Fig. 12A</figref> includes a stent where a distal end 414 that is "closed off" by intersecting elements or wires 402 403. Accordingly, any of the variations of the stents disclosed herein can include an open lumen type stent or a closed lumen type stent as shown in <figref idref="f0024">Fig. 12A</figref>. As noted herein, the wires forming the stent 400 can comprise a single wire that is wound from a first direction (e.g., from proximal to distal) and then wound back in a second direction (e.g., from distal to proximal).

0097<figref idref="f0024">Fig. 12A</figref> also illustrates a stent 400 comprised of twisted wires 402 or elements. For example, <figref idref="f0024">Fig. 12B</figref> shows a magnified view of the section 12B in <figref idref="f0024">Fig. 12A</figref>. As illustrated, the elements 402 403 are twisted to increase the surface area at the exterior perimeter of the stent 400. The twisting or spiraling of the elements 402 403 creates additional surface area to increase the ability of the stent 400 to capture debris, thrombus, foreign body, etc. as the stent is expanded against the debris. The twisting elements 402 403 can twist along the entire length of the stent 400 or along one or more portions of the stent. In certain variations, the twisting of the elements 402 403 is sufficiently loose such that as the stent expands into a clot or obstruction, the twisted pairs slightly separate to allow material to become trapped between the elements making up the pairs. The construction shown in <figref idref="f0024">Figs. 12A and 12B</figref> also provide an additional benefit to a retrieval stent. In the illustrated variation, the twisted or spiraling elements interlock with crossing elements to form intersections 405 that provided added radial expansive force. As shown, a first twisted element 407 passes in between elements 402 403 of an intersecting element 409. When in an expanded state, the element on the interior of the intersection 405 (in this case element 403) provides an added outward radial force against the intersection 405. However, since the elements are not affixed but instead are slidable at the intersection 405, the force required to linearlize and compress the stent 400 is reduced due to the fact that the intersections are not affixed but slidable over the adjacent elements. This reduced linearization force allows the stent to be compressed to a small diameter for positioning within a microcatheter but allow for a significant radial expansive force once removed from the microcatheter. This design allows for a reduction in radial force of the stent against the vessel wall when the stent is pulled and removed from the vessel. However, this design also provides a high degree of radial force due to the interweaving of elements when the stent is deployed in the vessel prior to withdrawal of the stent.

0098<figref idref="f0025 f0026">Figs. 12C to 12F</figref> illustrate another variation of types of stents 400 that have an irregular surface at an exterior of the stent 400 that is formed by an intersection of elements 402 403. The intersection or crossing of the elements forms a type of barb or knuckle 416 that creates an irregular surface on the exterior of the stent 400. <figref idref="f0025">Fig. 12C</figref> illustrates a variation of a stent 400 having a plurality of knuckles 52 that are radially spaced about an axis 390 of the stent 400. <figref idref="f0026">Fig. 12E</figref> shows another variation of a stent 400 with knuckles 416 aligned with an axis 390 of the stent 400 as shown in <figref idref="f0025">Fig. 12D</figref>. Although the figures show the axial and radial aligned knuckles 416 on separate devices, both types of knuckles 416 can be incorporated into a single stent structure. Varying the alignment of knuckles can permit increased radial force as the stent expands into the obstruction or increased flexibility as the stent navigates through tortuous anatomy.

0099<figref idref="f0027">Fig. 12G</figref> illustrates a proximal end of the stent structure 400 as shown, a plurality of elements 402 and 403 extend along the shaft 412 and diverge to form the fluid permeable closed proximal end of the stent structure 400. The elements 402 and 403 that extend along the shaft 412 can be covered by a sheath, tube, spiral cut tube, or any structure 418 that prevents separation of the elements 402 403. A variation of the stent structure 402 includes a construction where the elements 402 403 are not glued, welded, or have any similar type of joint in the distal portion 420 of the shaft 412. Instead, the joint 411 is located proximal to the distal section of the shaft 412 in an intermediate section 422. Because joints or other similar features reduce flexibility of the joined structure, positioning the joints 411 in a proximal area allows the the distal portion 420 of the shaft to remain flexible.

0100The exemplary 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.

0101As 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. 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.

0102Various 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 scope of the invention as claimed. 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.

0103It is important to note that where possible, aspects of the various described embodiments, or the embodiments themselves can be combined. Where such combinations are intended to be within the scope of this disclosure.