Abstract:
An apparatus includes an embolic coil including a mechanically flexible tubular member having a central lumen and a plurality of expandable sheaths spaced along the axial length of the tubular member, each expandable sheath enveloping and corresponding to the plurality of apertures, the expandable sheaths configured to have an initial low profile arrangement and upon introduction of an expansion medium to the central lumen of the tubular member radially expands to a high profile arrangement. Methods for making and using the apparatus are also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/605,313 filed Mar. 1, 2012. The contents of U.S. Provisional Application No. 61/605,313 are incorporated herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    This invention relates to coils, such as embolic coils, as well as related methods, devices and compositions. 
         [0003]    A brain aneurysm, also called an intracranial aneurysm, is an abnormal bulge or ballooning in a blood vessel supplying the brain. The weakened area forms a sac that fills with blood. Intracranial aneurysms can rupture and cause bleeding into the brain. Usually this occurs in the area between the brain and the surrounding membrane (the arachnoid), called the subarachnoid space, causing a subarachnoid hemorrhage. Subarachnoid hemorrhage resulting from a ruptured intracranial aneurysm occurs approximately 35,000 times per year in the United States. 
         [0004]    Currently, intracranial aneurysms are treated by microsurgical clipping or endovascular coiling. In the latter, the goal is to prevent aneurysm rupture by inserting a thin wire into the aneurysm forming a coiled structure which blocks blood flow into the aneurysm. In some treatment paradigms, intracranial stents are used within the blood vessel to buttress placement of coils 
       SUMMARY 
       [0005]    In a general aspect of the invention, an apparatus comprising an embolic coil including a mechanically flexible tubular member having a central lumen; and a plurality of expandable sheaths spaced along the axial length of the tubular member, each expandable sheath configured to have an initial low profile arrangement and upon introduction or withdrawal of an expansion medium to the central lumen of the tubular member radially expands to a high profile arrangement. 
         [0006]    Embodiments of this aspect of the invention may include one or more of the following features. The tubular member includes apertures, spaced along the axial length of the tubular member, each aperture corresponding to one of the expandable sheaths and each configured for introduction or withdrawal of the expansion medium. Each of the expandable sheaths includes an inflatable balloon. 
         [0007]    The expandable medium can be an embolizing agent in a variety of forms (e.g., liquid gas). For example, the embolizing agent can comprise a biocompatible polymer, prepolymer, polyethelene glycol, derivatives of polyethelene glycol, or a hydrogel. Other embolizing agents can include Onyx®, Neucrylate AN™ or other non-adhesive liquid embolic agents typically used for the pre-surgical embolization of intracranial brain Arteriovenous malformations (bAVM). 
         [0008]    The apparatus includes a microcatheter configured to deliver the embolic coil to a treatment site, the microcatheter having a guidewire and a release mechanism configured to detachably release the embolic coil from a distal end of the microcatheter. 
         [0009]    In another aspect of the invention, a method of making an embolic coil includes providing a mechanically flexible tubular member having a central lumen; providing a plurality of expandable sheaths along the axial length of the tubular member, each expandable sheath configured to have an initial low profile arrangement and upon introduction or withdrawal of an expansion medium to the central lumen of the tubular member radially expands to a high profile arrangement. 
         [0010]    Embodiments of this aspect of the invention may include one or more of the following features. The method further includes providing apertures, spaced along the axial length of the tubular member, each aperture corresponding to one of the expandable sheaths and each configured for introduction or withdrawal of the expansion medium. The method further includes forming each of the expandable sheaths as an inflatable balloon. The method further includes providing an embolizing agent comprising one or more of a biocompatible polymer, prepolymer, polyethelene glycol, derivatives of polyethelene glycol, a hydrogel, Onyx®, Neucrylate AN™. 
         [0011]    In still another aspect of the invention, a method of treating a patient includes affixing, to a distal end of a microcatheter, an embolic coil including a mechanically flexible tubular member having a central lumen and a plurality of expandable sheaths spaced along the axial length of the tubular member; delivering the microcatheter with the embolic coil through the vasculature of the patient to a treatment site; and providing an expansion medium to at least one of the plurality of expandable sheaths to expand the at least one sheath from an initial low profile arrangement to a high profile arrangement. 
         [0012]    Among other advantages, an embolic coil having expandable sheaths allows for complete occlusion and embolism of an aneurysm. Once the embolic coil is positioned within the aneurysm thrombosis is enhanced. Introducing the embolic coil within the aneurysm using a delivery system (e.g., catheter) is made easier because the coil is introduced in a low profile arrangement. Once properly positioned with the aneurysm, the expandable sheaths of the embolic coil are expanded into a higher profile arrangement. In this higher profile arrangement, blood flow in the aneurysm is blocked by virtue of the expandable sheaths filling the volume within the aneurysm. Furthermore, in their expanded, higher profile condition, the embolic coil is contained. 
         [0013]    Furthermore, the extent to which the expandable sections of the embolic coil are expanded to fill the volume of the aneurysm can be controlled by the surgeon or operator. For example, the surgeon or operator can position the embolic coil and then fill the expandable sheaths such that the coil loops establish a foothold within the aneurysm. In this way, once the embolic coil is detached from the delivery catheter, the risk of the embolic coil are portions of the coil being released from the aneurysm outside the neck of the aneurysm and into the vasculature is minimized, which otherwise might lead to distal embolism and stroke with undesirable clinical effects. 
         [0014]    Modes for carrying out the present invention are explained below by reference to an embodiment of the present invention shown in the attached drawings. The above-mentioned object, other objects, characteristics and advantages of the present invention will become apparent from the detailed description of the embodiment of the invention presented below in conjunction with the attached drawings. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is a schematic side sectional view representation of an embolization delivery system including a microcatheter; 
           [0016]      FIG. 2  is a side view of a portion of an embolic coil shown in its unfurled state and configured to be detachably connected to the distal end of the microcatheter of  FIG. 1 ; 
           [0017]      FIG. 3  is the embolic coil of  FIG. 2  disposed within an aneurysm and in its unexpanded state; and 
           [0018]      FIG. 4  is the embolic coil of  FIG. 2  disposed within an aneurysm and in its expanded state. 
           [0019]      FIG. 5  is an alternative embodiment of an embolic device. 
       
    
    
     DESCRIPTION 
       [0020]    Referring to  FIG. 1 , an embolization delivery system  10  includes a microcatheter  12  having a proximal end  14  and a distal end  16 , a connector  18 , a detachable embolic coil  20 , and a release mechanism  22 . The proximal end  14  of the microcatheter  12  may be coupled to or pass through a manifold  24  for use with procedures that include a microcatheter  12  or other delivery mechanisms. In general, embolization delivery system  10  establishes a pathway through the vasculature  25  of a patient. In this embodiment, microcatheter  12 , here coupled to manifold  24 , is first inserted into the vasculature  25  of the patient to a preselected or targeted location. In this particular application, the microcatheter  12  is delivered to an aneurysm  26 . The distal end  16  of the microcatheter  12  is capable of being inserted into the vasculature  25  of the patient and positioned proximate to an aneurysm  26  or other abnormality in the vasculature  25 . In other embodiments, embolization delivery system  10  includes a stainless-steel, nitinol, or other metallic guidewire for facilitating delivery of the embolic coil  20  to the aneurysm  26 . 
         [0021]    Connector  18  has a proximal portion that is disposed around and permanently coupled to the distal end  16  of the microcatheter  12 . A proximal end  28  of embolic coil  20  is disposed within the connector  18  and securely held in place by compressive forces. In addition, the embolic coil  20  is substantially linear as it progresses through the microcatheter  12  due to the boundary constraints placed upon the coil  20  by the microcatheter  12 . However, upon exiting the distal end  16  of the microcatheter  12 , the distal end  32  of the embolic coil  20  will curl or coil in a pre-determined shape previously effected during the design and manufacturing stage order to occlude the flow of fluid to the aneurysm  26  or other abnormality in the vasculature  25 . 
         [0022]    In one embodiment, the microcatheter  12  includes a release mechanism  40  for detaching the embolic coil  20  once it is positioned with the aneurysm  26 . For example, the release mechanism can include a wire  42  that is manipulated by a physician or other attendant. Manipulating the wire  42  reduces or eliminates the compressive forces exerted by the connector  18  onto the proximal end  28  of the embolic coil  20 , thereby, allowing the coil to detach from the microcatheter  12 . For example, manipulation of wire  42  by the surgeon can involve pulling or moving the wire  42  in a manner that causes the coil  20  to be released into the vasculature, in particular, the aneurysm  26 . 
         [0023]    Alternative detachment or release mechanisms may also be used to detach the embolic coil from the distal end of the microcatheter. For example, an electrolytic, a mechanical ball-socket arrangement or through the use of a local electrically generated heating of a polymeric attachment zone are suitable means of releasing the embolic coil. 
         [0024]    Referring to  FIG. 2 , embolic coil  20  is shown in its spread and unfurled state. Embolic coil  20  includes a flexible cylindrical member  50  having a central lumen  52  and a series of spaced-apart apertures  54  along its length. Each aperture  54  is enclosed by an expandable sheath  56  which envelopes the cylindrical member  50  around the aperture. 
         [0025]    Embolic coil  20  is formed of a metal filament such as platinum, platinum alloy (e.g., platinum-tungsten alloy), stainless steel, or shape-memory alloys (e.g., Nitionol). In certain embodiments, embolic coil  20  can be formed of one or more polymers, such as polyolefins, polyurethanes, block copolymers, polyethers, and polyimides, The expandable sheaths are formed of, for example, an elastomeric material which may comprise, but is not limited to, polymeric materials, latex, rubber, silicon rubber, Pebax®, urethane, pelothane, Tecothane®, polyester isobutyl styrene, epoxies and thermoplastics 
         [0026]    It is important to appreciate that the size and spacing of apertures  54  as well as the associated expandable sheaths  56  may be non uniform or irregular. Furthermore, the stiffness of the membrane of the expandable sheaths may be non-uniform with each unit or between units 
         [0027]    In certain embodiments, a catalyst or an accelerant may be coated on the balloon at different concentrations to affect the reaction. Alternatively the surface coating of the balloon may be conductive and a current could be passed through the microcatheter  12  so as to start a catalyst process or to induce a swelling reaction of a local hydrogel or affect the rate of a chemical reaction needed for solidification of the liquid polymer, hydrogel or other liquid embolic material. The current to the balloon coating surface could be provided by another embedded wire or conductor within the delivery microcatheter or guidewire. 
         [0028]    Referring to  FIG. 3 , in operation, microcatheter  12  is guided, for example, via a guidewire to the aneurysm  26 . Once the microcatheter  12  is positioned near the neck of the aneurysm  26 , embolic coil  20  is extended within the aneurysm. As the embolic coil  20  is pushed from the distal end  16  of microcatheter  12  into the aneurysm  26 , the distal end  32  of the embolic coil begins to curl or coil thereby filling the volume of the aneurysm. Even at this point, embolic coil  20  can initiate a clotting or thrombotic reaction within the aneurysm that can decrease bleeding from the aneurysm. In certain procedures a stent may be passed first into the parent artery to serve as a scaffold for the coils (“stent-assisted coiling”), for example, as discussed in WO 2012/102919, which is incorporated herein by reference. 
         [0029]    Referring to  FIG. 4 , to further fill the volume of and embolize the aneurysm  26 , an embolizing agent  58  is introduced through microcatheter  12 , through central lumen  52  and into expandable sheaths  56 . As the embolizing agent is introduced, each expandable sheath  56  swells to fill the volume within the aneurysm  26 . The embolizing agent generally has sufficient viscosity for being retained in the expandable sheaths  56 . 
         [0030]    Embolizing agent can be in a variety of forms and can include a number of different compositions. For example, the embolizing agent can be in the form of a liquid embolizing agent such as Onyx®, a product of ev3 Endovascular, Inc., Plymouth, Minn. The liquid embolizing agent can also include a non-adhesive liquid embolic agent such as Neucrylate AN™, typically used for the pre-surgical embolization of intracranial brain Arteriovenous malformations (bAVM). Other suitable liquid embolizing agents can include biocompatible polymers, prepolymers, or polyethelenes (e.g., polyethelene glycol). The embolizing agent may also be 1-Hexyl n-cyanoacrylate compound (Neucrylate™ AN) or include a hydrogel. 
         [0031]    Once the expandable sheaths  56  are filled or inflated, the surgeon can use the release mechanism  40  to release the embolic coil and then withdraw the microcatheter  12  from the vasculature  25 . Because the expandable sheaths  56  are expanded after being introduced into the aneurysm the risk of the embolic coil  20  or portions of the coil being released into the vasculature  25  are virtually eliminated. Furthermore, the embolic coil  20  with its expandable sheaths  56  expanded serves a scaffolding framework that is controllable by the surgeon. 
         [0032]    It is important to appreciate that once the embolizing agent  58  is introduced within the expandable sheaths  56 , the surgeon can withdraw all or some of the embolizing agent  58  using suction to reduce the degree to which the expandable sheaths  56  are filled. For example, the surgeon may wish to withdraw a portion of the embolizing agent, reposition the emboli coil  20  and then re-expand the expandable sheaths  56 . 
         [0033]    As discussed above, a variety of liquid embolic agents having different viscosities can be used. Moreover, after introducing a liquid embolic agent to the expandable sections, a different agent serving as a catalyst can be introduced to cause the liquid embolic agent to change characteristics (e.g., harden). 
         [0034]    The structure described above in conjunction with  FIGS. 1-4  was also linear in nature. Other embodiments of the embolic coil may have arrangements that when released into the aneurysm is 3-dimensional or stent-like. 
         [0035]    Referring to  FIG. 5 , for example, an embolic coil  60  has an umbrella-like structure with each hollow rib or vane  62  of the umbrella structure including spaced parts expandable sheaths  64 , each sheath corresponding to an aperture (not shown) on the rib. 
         [0036]    Although the structure described above in conjunction with  FIGS. 1-4  are in the form of a single channel lumen, in other embodiments, embolic coil  20  can include other structures such as multiple channel structures that may be nested. In such embodiments, the multiple channels provide an initial structure that is multi-dimensional and may be advantageous for larger aneurysms. Furthermore, in such situations multiple embolic coils can be introduced, either together or sequentially, into the aneurysm and are individually controlled. 
         [0037]    The structure described above in conjunction with  FIGS. 1-4  was also linear in nature. Other embodiments of the embolic coil may have arrangements that when released into the aneurysm is 3-dimensional or stent-like. For example, in one embodiment, the embolic coil has an umbrella-like structure with each rib or vane of the umbrella structure including spaced parts expandable sheaths. Thus, the term “coil” is not intended to be restricted to linear single path structures but is intended to encompass a wide variety of geometries suitable for filling the aneurysm. 
         [0038]    It is to be understood that the foregoing description is intended to illustrate and not to limit the scope of the invention, which is defined by the scope of the appended claims. Other embodiments are within the scope of the following claims. For example, other structures for flexible catheters used to deliver detachable/releasable embolic coils, as well as the structures for the embolic coils themselves are encompassed by the claims. The variety of delivery systems (e.g., catheters)and coils described in U.S. Provisional Application No. 61/605,313 are also encompassed by the claims. For example,  FIG. 8  of U.S. Provisional Application No. 61/605,313 and the accompanying description in the specification shows an embolic coil having expandable sheaths delivered by a microcatheter to an aneurysm. The description of silk-based as well as other non-silk compositions suitable for use as an embolizing agent U.S. Provisional Application No. 61/605,313 are also encompassed by the claims.