Patent Publication Number: US-8118829-B2

Title: Clot removal device

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 10/689,893, filed Oct. 21, 2003. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to intravascular medical devices. More particularly, the present invention pertains to devices for capturing and removing blood clots from a blood vessel. 
     BACKGROUND 
     The present invention pertains generally to emboli collection and removal. 
     Blood thrombus, may form a clot in a patient vasculature. Sometimes such clots are harmlessly dissolved in the blood stream. At other times, however, such clots may lodge in a blood vessel where they can partially or completely occlude the flow of blood. If the partially or completely occluded vessel feeds blood to sensitive tissue such as, the brain, lungs or heart, for example, serious tissue damage may result. 
     When symptoms of an occlusion are apparent, such as an occlusion resulting in a stroke, immediate action should be taken to reduce or eliminate resultant tissue damage. One approach is to treat a patient with clot dissolving drugs. These drugs, however, do not immediately dissolve the clot from the patient. 
     BRIEF SUMMARY 
     The present invention pertains to devices for removing blood clots from blood vessels. In at least some embodiments, a clot removal device includes a shaft and one or more strut members. Each of the one or more strut members may include a proximal end that is attached to the shaft, a loop region, and a distal end that is coupled to the shaft. These and some of the other structural features and characteristics are described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional side view of an example medical device; 
         FIG. 2  is a perspective view of an example medical device; 
         FIG. 3  is a partial cross-sectional side view of an example medical device collapsed within a delivery or retrieval sheath; 
         FIG. 4  is a partial cross-sectional plan view of an example medical device disposed within a blood vessel; and 
         FIG. 5  is a another partial cross-sectional plan view of an example medical device disposed within a blood vessel where the device has transitioned between differing blood vessels or vascular regions. 
     
    
    
     DETAILED DESCRIPTION 
     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings illustrate example embodiments of the claimed invention. 
     For a number of reasons, it may be desirable to capture and/or remove clots from the vasculature.  FIG. 1  is a partial cross-sectional side view of an example clot pulling medical device  10  disposed in a blood vessel  12 . Blood vessel  12  can be essentially any vessel. Device  10  may include a plurality of struts  14  coupled to an elongate shaft or guidewire  16 . Struts  14  may define a basket member or region  18 , suitable for capturing a blood clot  20  disposed in the vasculature. In general, device  10  can be advanced through the vasculature to a suitable location, for example adjacent clot  20 , and configured so that clot  20  can be captured in basket region  18 . Device  10  and the captured clot  20  can be removed from the vasculature. 
     In at least some embodiments, struts  14  may include a proximal end region  24  and a distal end region  30 . End regions  24 / 30  generally define the position where struts  14  and shaft  16  are coupled to one another. The form or configuration of this coupling may vary. For example, end regions  24 / 30  may be wound or coiled about shaft  16 . Alternatively, end regions  24 / 30  may be coupled to shaft by a mechanical connection or connector, thermal bond, weld, adhesive bond, and the like, or combinations thereof. In some embodiments, end regions  24 / 30  are fixedly attached to shaft  16 . For example, end regions  24 / 30  may be wound so that a mechanical bond is formed between shaft  16  and struts  14 . Alternatively, end regions  24 / 30  may be fixedly attached via the other coupling means described above or in any other suitable way. 
     Instead of being fixedly attached, proximal end region  24 , distal end region  30 , or both end regions  24 / 30  may be slidable along shaft  16 . For example, either end region  24  or end region  30  can be slidable along shaft  16  with the non-slidable end region being fixedly attached. Alternatively, both end regions  24 / 30  can be slidably coupled to shaft  16 . The manner in which end regions  24 / 30  are slidably coupled to shaft  16  may vary. For example, end region  24 / 30  may be coiled about shaft  16  in a manner that allows the coiled end regions  24 / 30  to slide or move along shaft  16 . Alternatively, end regions  24 / 30  may be attached to a tubular structure or member that is slidably disposed along shaft  16 . Slidability is illustrated in  FIG. 1  by double-headed arrows located below end regions  24 / 30 , which indicate that end regions  24 / 30  may be movable in either the proximal or distal direction. Slidability may be desirable, for example, by allowing one or both of end regions  24 / 30  to be moved in order to collapse or expand device  10 . For example, proximal end region  24  can be moved in the proximal direction, distal end region  30  can be moved in the distal direction, or both end regions  24 / 30  can be moved in these directions so that device  10  (i.e., basket region  18 ) collapses. Collapsing may be desirable, for example, by reducing the profile of device  10  so as to improve transportation (e.g., delivery and/or retrieval) of device  10  through the vasculature. 
     Turning now to  FIG. 2 , it can be seen that struts  14  (which are individually indicated in  FIG. 2  as struts  14   a ,  14   b , and  14   c ) may define a mouth or opening  22  of basket region  18 . For example, struts  14  may include a number of bends or curves so mouth  22  may be “petal shaped” or otherwise extend around shaft  16  in a manner that defines a petal-shaped opening  22 . According to this embodiment, each strut  14   a/b/c  may include a proximal end  24   a/b/c  coupled to shaft  16  and disposed adjacent end region  24 , an arched or looped region  26   a/b/c  adjacent proximal end  24   a/b/c , a distally-extending strut region  28   a/b/c , and a distal end  30   a/b/c  coupled to shaft  16  and disposed adjacent end region  30 . Additionally, struts  14   a/b/c  may be connected or coupled with one another (at one or more connection points) in a folded sheet configuration or construction. Proximal ends  24   a/b/c  may be attached to shaft  16  in a number of different manners. For example, proximal ends  24   a/b/c  may be wound about shaft  16 , mechanical bonded (e.g., by crimping, attached by placing a sleeve over ends  24   a/b/c , etc.), thermally bonding, welding, brazing, adhesively bonding, or in any other suitable manner. In some embodiments, proximal ends  24   a/b/c  are directly attached to shaft  16  while in other embodiments, proximal ends  24   a/b/c  may be attached to another structure that is disposed over or otherwise coupled to shaft  16 . For example, ends  24   a/b/c  may be coupled to a tube or tubular sleeve coupled to shaft  16 . As described above, ends  24   a/b/c  (and/or end region  24 ) may be fixedly attached to shaft  16  or slidable over shaft  16 . 
     Looped regions  26   a/b/c  may generally loop circumferentially about a portion of shaft  16 . The extent that each looped region  26   a/b/c  loops about shaft  16  may vary depending on the number of struts included. For example,  FIG. 2  illustrates that mouth  22  and/or basket region  18  can include three struts  14   a/b/c . However, this number of struts is only illustrative in nature as any suitable number (e.g., 1, 2, 3, 4, 5, 6, or more) of struts may used. Thus, by including three struts  14   a/b/c , it may be desirable for each looped region  26   a/b/c  to extend around about one-third or more (i.e., about 120 degrees or more) of the circumferential area around shaft  16 . 
     In addition, it may be desirable for adjacent looped regions  26   a/b/c  to overlap. For example, overlapping looped regions  26   a/b/c  or allowing these regions to overlap may allow mouth  22  to be adapted to appose blood vessels of differing sizes. This characteristic is described in more detail below. It can be appreciated that overlapping looped regions  26   a/b/c  may also vary the amount of circumferential area that each looped region  26   a/b/c  extends around shaft  16 . For example, it may be desirable to overlap adjacent looped regions  26   a/b/c  in the range of about 5 percent to about 30 percent, or more. Accordingly, looped regions  26   a/b/c  may extend about 120 degrees (no overlap) or about 126 degrees (5 percent overlap) to about 156 degrees (30 percent overlap), or more. The amount of circumferential area that each looped region  26   a/b/c  need not be the same as each may span differing portions and overlap to differing degrees. 
     In some embodiments, particularly those where looped regions  26   a/b/c  overlap, it may be desirable for looped regions  26   a/b/c  to be somewhat angled so that adjacent loops  26   a/b/c  do not interfere with one another. For example, one end of looped regions  26   a/b/c  (e.g., the end closer to proximal ends  24   a/b/c ) may be further away from shaft  16  than another end of looped regions  26   a/b/c  (e.g., the end closer to distally-extending regions  28   a/b/c ). Accordingly, looped regions  26   a/b/c  can freely overlap without adjacent looped regions  26   a/b/c  distorting or displacing one another. Alternatively, the mere fact that looped regions  26   a/b/c  are curved may allow sufficient space adjacent overlapped regions. In still other alternative embodiments, it may be desirable or acceptable for adjacent, overlapping looped regions  26   a/b/c  to contact one another. 
     Looped regions  26   a/b/c  may be formed in a number of different ways. For example, looped regions  26   a/b/c  may be formed by disposed a shaft about a mandrel or other suitable molding device. In embodiments where struts  14   a/b/c  are comprised of a shape-memory material, the molded or bended shaft may be heat treated to set the desired shape, corresponding to looped regions  26   a/b/c , within the material. It can be appreciated that any of the other portions of struts  14   a/b/c  may be analogously worked so as to have the desired shape, characteristics, and features. 
     Distally-extending regions  28   a/b/c  generally extend from looped regions  26   a/b/c  toward distal ends  30   a/b/c . Regions  28   a/b/c  generally extend along shaft  16 . In some embodiments, regions  28   a/b/c  extend generally parallel to shaft  16  while in other embodiments, regions  28   a/b/c  may converge inward toward shaft  16 . The length of regions  28   a/b/c  may vary depending on the desired configuration of device  10  and/or basket region  18 . It can be appreciated that as the length of regions  28   a/b/c  increases, the area of basket region  18  increases. It may be desirable to use devices  10  with generally increased basket  18  area to capture relatively large clots or when used in relatively large vessel. Conversely, it may be desirable to use devices  10  with generally decreased area in sensitive or small vascular areas. 
     Distal ends  30   a/b/c  may be attached to shaft  16  in a manner similar to how proximal ends  24   a/b/c  are attached. For example, distal ends  30   a/b/c  may be wound about shaft  16 . In some embodiments, distal ends  30   a/b/c  may be fixedly attached to shaft  16  while in others the windings of distal ends  30   a/b/c  may be slidable or otherwise moveable along shaft  16 . This later embodiment may be desirable, for example, by allowing device  10  and/or basket region  18  to be collapsed by pulling or shifting the position of distal ends  30   a/b/c  in the distal direction. Accordingly, basket  18  can be collapsed and, for example, be disposed in a delivery sheath. Proximally retracting the sheath relative to device  10  may allow distal ends  30   a/b/c  to shift or move proximally and expand basket  18 . In some embodiments, the slidability of distal ends  30   a/b/c  may be enhanced by coupling ends  30   a/b/c  to a tubular member  32  slidably disposed over shaft. Tube  32  may comprise a hypodermic tube (i.e., a “hypotube”), metal or polymer sleeve, or any other suitable structure. Although tube  32  is shown with respect to distal ends  30   a/b/c  and distal end region  30 , the use of tube  32  at proximal end region  24  is contemplated and may be used in some embodiments of device  10 . 
     The manufacturing of device  10  may generally include forming struts  14   a/b/c  into the desired shape and coupling them to shaft  16 . In some embodiments, forming struts  14   a/b/c  may include disposing a shaft material on a mandrel or otherwise working the material so as to define the various regions of struts  14   a/b/c . Coupling struts  14   a/b/c  to shaft  16  may include winding proximal ends  24   a/b/c  and/or distal ends  30   a/b/c  about shaft  16 . In addition or in the alternative, distal ends  30   a/b/c  may be attached to tubular member  32  as described above. It should also be noted that although shaft  16  is described above as being a guidewire, shaft  16  should not be interpreted to being limited to being just a guidewire. It can be appreciated that shaft  16  could be any intravascular device or be any device designed to pass through an opening or body lumen. For example, the device may comprise a catheter (e.g., therapeutic, diagnostic, or guide catheter), endoscopic device, laproscopic device, or any other suitable device. Additionally, in embodiments where shaft  16  is a structure other than a guidewire, the steps of attaching struts  14   a/b/c  can be varied slightly in order accommodate the differing sizes and shapes of these structures. 
     In some other embodiments, device  10  may be manufactured by laser-cutting, laser etching, chemical etching, or photo-chemical etching a tubular structure so as to define struts  14   a/b/c  and basket  18 . For example, basket  18  and struts  14   a/b/c  can be defined by laser-cutting a tubular structure such as a hypodermic tube (i.e., a “hypotube”). This manufacturing method may be desirable for a number of reasons. For example, this method may allow struts  14   a/b/c  and basket  18  to be formed in a relatively simple manner, with relatively few manufacturing steps. Additionally, following this method may allow shaft  16  to be defined by the proximal region of the hypotube. Accordingly, the manufacturing method may be further simplified by not requiring any welding or attaching steps to connect various structures of device  10 . Alternatively, device  10  may be manufactured by cutting or forming the appropriate structures into a generally planar sheet of material and then, if necessary, attaching the ends of the planar structure or attaching one or more planar structures together in any suitable manner. For example, the opposing sides of a sheet of material may be attached, welded, adhesively bonded, bonded with a polymer strip, thermally bonded, a mechanically connected, and the like, or in any other suitable manner. 
     All or portions of device  10  may be manufactured from any suitable material including metals, metal alloys, polymers, etc. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316L stainless steel; linear-elastic or super-elastic nitinol or other nickel-titanium alloys, nickel-chromium alloy, nickel-chromium-iron alloy, cobalt alloy, tungsten or tungsten alloys, MP35-N (having a composition of about 35% Ni, 35% Co, 20% Cr, 9.75% Mo, a maximum 1% Fe, a maximum 1% Ti, a maximum 0.25% C, a maximum 0.15% Mn, and a maximum 0.15% Si), hastelloy, monel 400, inconel 825, or the like; or other suitable material. 
     Some examples of suitable polymers may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM), polybutylene terephthalate (PBT), polyether block ester, polyurethane, polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example a polyether-ester elastomer such as ARNITEL® available from DSM Engineering Plastics), polyester (for example a polyester elastomer such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysulfone, nylon, perfluoro(propyl vinyl ether) (PFA), other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments portions or all of device  10  can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 5% LCP. 
     In some embodiments, a coating, for example a lubricious, a hydrophilic, a protective, or other type of coating may be applied over portions of or all of device  10 . Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves device exchanges. Lubricious coatings improve steerability and improve lesion crossing capability. Suitable lubricious polymers are well known in the art and may include silicone and the like, hydrophilic polymers such as polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers may be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. Some other examples of such coatings and materials and methods used to create such coatings can be found in U.S. Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein by reference. In some embodiments, the sheath or coating may be applied over basket region  18 . This may provide extra surface area to contain clots that might be captured therein. 
     The sheath or polymeric layer coating may be formed, for example, by coating, by extrusion, co-extrusion, interrupted layer co-extrusion (ILC), or fusing several segments end-to-end. The layer may have a uniform stiffness or a gradual reduction in stiffness from the proximal end to the distal end thereof. The gradual reduction in stiffness may be continuous as by ILC or may be stepped as by fusing together separate extruded tubular segments. The outer layer may be impregnated with a radiopaque filler material to facilitate radiographic visualization. Those skilled in the art will recognize that these materials can vary widely without deviating from the scope of the present invention. 
     Device  10 , or portions thereof, may also be coated, plated, wrapped or surrounded by, doped with, or otherwise include a radiopaque material. For example, struts  14   a/b/c  may be made from a radiopaque material or may include a radiopaque marker member or coil coupled thereto. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of device  10  in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, plastic material loaded with a radiopaque filler, and the like. 
     In some embodiments, a degree of MRI compatibility may be imparted into device  10 . For example, to enhance compatibility with Magnetic Resonance Imaging (MRI) machines, it may be desirable to make portions of device  10 , in a manner that would impart a degree of MRI compatibility. For example, device  10 , or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (artifacts are gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image. Device  10 , or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, Elgiloy, MP35N, nitinol, and the like, and others. 
     As stated above, device  10  and/or basket region  18  may be configured to shift between a first generally collapsed configuration and a second generally expanded configuration. In at least some embodiments, shifting between these configurations includes the longitudinal movement of distal ends  30   a/b/c  as described above. In some embodiments, device  10  or portions thereof may be made of a shape-memory material (such as nickel-titanium alloy) that can assume a pre-defined shape when unconstrained or when subjected to particular thermal conditions. According to this embodiment, device  10  can be manufactured to be “self-expanding” so that it can be delivered in a collapsed configuration (i.e., with distal ends  30   a/b/c  pulled or moved distally to collapse basket  18 ) then shift to the expanded configuration when a constraint (e.g., a delivery sheath) is removed or when device  10  is subject to the thermal conditions within blood vessel  12 . This feature could also be used at proximal ends  24   a/b/c . Alternatively, shifting may occur by mechanically moving proximal ends  24   a/b/c  or distal ends  30   a/b/c , for example, by an attached or separately provided shaft. 
     When device  10  and/or basket region  18  are in the collapsed configuration, it may be suited for being delivered via a suitable catheter or delivery sheath  34  as shown in  FIG. 3 . For example, it may be desirable to collapse basket region  18  and dispose it within a lumen  36  within sheath  34 . It can be seen in  FIG. 3  how distally moving distal end region  30  and/or distal ends  30   a/b/c  can help collapsed device  10  so that it may be easily be disposed in lumen  36 . Additionally, it can be seen that as ends  30   a/b/c  are shifted, basket region  18  elongates. Accordingly, looped regions  26   a/b/c  also begin to straighten and elongate. Because the collapsing of device  10  and/or basket region  18  includes the longitudinal shifting of ends  30   a/b/c  and the elongation of basket region  18 , outward radial forces may be reduced. This may allow device  10  to more easily be disposed in or otherwise advance through sheath  34 . Moreover, the length of distally-extending regions  28   a/b/c  can be altered so that collapsing forces and radial forces can be further reduced. For example, elongating regions  28   a/b/c  may reduce the forces needed to collapse device  10  and reduce radial forces that might be exerted on the inside surface of sheath  34 . 
     With basket region  18  collapsed within lumen  36 , sheath  34  and device  10  can be advanced to the desired position (e.g., adjacent a clot) and sheath  34  can be proximally retracted so that device  10  emerges therefrom and can shift to the expanded configuration. Alternatively, device  10  can be delivered by first positioning sheath  34  at the desired location and then advancing device  10  through sheath  34 . Regardless of how device  10  and basket  18  are moved into position, expanded basket  18  can be used to capture clot  20 . In some embodiments, sheath  34  may also be used to aspirate clot  20  or other clots captured by device  10  by applying a vacuum to the sheath lumen  36 . 
     Removal of device  10  may be accomplished in a number of different ways. For example, device  10  may be removed by simply retracting it proximally from the vasculature. This may include retracting basket  18  up to an introducer sheath disposed at the vascular access site. Once at the introducer sheath, the clot can be aspirated from basket  18  or removed together with basket  18 . Alternatively, device  10  may be retracted up to or otherwise be disposed within a suitable retrieval sheath or catheter. 
     In some embodiments, catheter or sheath  34  may be a microcatheter. The dimensions and general configuration of the microcatheter can vary. For example, catheter  34  may have an inside lumen diameter of about 0.016 to about 0.022 inches, or more or less. These dimensions may allow sheath  34  to be suitably sized to access a number of different vascular targets while having a lumen sized sufficient to allow device  10  to advance through or otherwise be disposed therein. In addition or in the alternative, sheath  34  may include a distal housing section configured for having basket region  18  (or other portions of device  10 ) disposed therein. Of course, a number of other delivery devices may be used including essentially any suitable structure. 
       FIGS. 4 and 5  illustrate some of the other uses and features of device  10 . For example,  FIG. 4  illustrates that by configuring looped regions  26   a/b/c  so that mouth  22  is generally concentric with shaft  16 , navigation through the vasculature can occur without spillage of captured clots  20  into the blood stream. This is because the concentric orientation of mouth  22  and shaft  16  allows mouth  22  to maintain apposition to the blood vessel wall. For example, when mouth  22  of device  10  is disposed in a side vessel  12   a , the concentric orientation helps keep device  10  centered within vessel  12   a . As device is retracted into the parent blood vessel  12 , mouth  22  can quickly become centered within this vessel  12 . Without the ability to center within a vessel or vessels, mouth  22  could end up being positioned so that a portion of it is pointed “downstream” so that clot  20  could flow out of basket region  18  and into the blood stream. Improved wall apposition may also be desirable by allowing basket region  18  to essentially filter the entire cross-sectional area of the vessel. Accordingly, it is less likely that clot  20  could by-pass basket region  18  and avoid capture. 
       FIG. 5  illustrates that mouth region  22  may also be adaptable to appose vessel of differing sizes. For example, device  10  may be navigating vessels  12  and  12   a , and vessel  12   a  may have a cross-sectional area that is smaller than vessel  12 . Accordingly, if mouth  22  was not configured to appose vessel of differing sizes, a portion of the bigger vessel  12  may be left unfiltered. 
     This adaptability may be accomplished in a number of ways. For example, struts  14   a/b/c  may be comprised of a shape-memory or super elastic material (including any of those described herein or any other suitable material) and set to a shape that is sized to appose a relatively large vessel (e.g., vessel  12 ). Other materials including linear elastic materials may also be used to have essentially the same effect. Regardless of what material is used, mouth  22  may be generally be amenable to being deformed to smaller sizes by constricting it within a smaller container (e.g., vessel  12   a ). However, mouth  22  can be configured so that constricting will not generally result in a plastic deformation in the material. Therefore, device  10  may be used in a small vessel, wherein mouth  22  is constrained somewhat to a smaller size, and still be able to expand to accommodate larger vessels. There may be a number of ways to account for the reduced mouth  22  size. For example, when mouth  22  is configured within a smaller vessel, adjacent looped regions  26   a/b/c  may overlap to a greater extent then when mouth  22  is disposed in a larger vessel. Because the shape-memory or linear material may be set or otherwise biased to be in a shape conforming to a generally larger vessel, when device  10  is then retracted to larger vessel  12 , mouth  22  can then expand to appose the inside surface of that vessel  12 . Thus, the use of overlapping looped regions  26   a/b/c  may help allow for mouth  22  to shift between a variety of different sizes while in use. 
     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.