Abstract:
An improved catheter and method of using the same is described. The catheter has at least one anchoring element at its distal tip region which is used to secure the catheter to a pre-implanted medical device, such as a stent, during the filling of an aneurysm. Such action prevents a buildup of pressure or of material from forcing the distal tip of the catheter to be forced from the aneurysm before the procedure is complete.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119(a) to U.S. Provisional Application No. 62/082,363, filed on Nov. 20, 2014, which is incorporated by referenced here in its entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates generally to medical devices. More specifically, the invention relates to a tip for a catheter which assists in keeping a distal end of a catheter stationary or relatively immobile while delivering a filling agent, such as a small intestinal submucosa (SIS) filament. Further, the present invention can be a method of delivering a filling agent to a body cavity using a catheter with a specialized tip. 
       BACKGROUND 
       [0003]    Aneurysms are characterized by swelling in the wall of a vessel which generally results in weakness in the vessel wall. If untreated, aneurysms may continue expanding until they burst thereby causing hemorrhaging. If, for example, an aneurysm is present within an artery of the brain, and the aneurysm should burst with resulting cranial hemorrhaging, death could occur. Aneurysms result from many different causes; however, most aneurysms are caused as a result of a degenerative disease which damages the muscular coating of a vessel with resulting congenital deficiency in the muscular wall of the vessel. 
         [0004]    One method for method for treating aneurysms is that of using a microcatheter for placing multiple very small embolic coils within the aneurysm with the expectation that fibrous material will become entrapped in the embolic coils to thereby stabilize the coils within the aneurysm. With this technique, it is possible to fill the aneurysm with embolic coils, thereby sealing off the walls of the aneurysm from the pressure of blood which exist in the adjacent vessel. Further, an implant may be placed across the aneurysm and embolic coils may be passed through the structure of the implant and into the aneurysm. The structure serves to hold the embolic coils within the stent until such time as these coils become stabilized by fibrous material growing into the coils. 
         [0005]    Some methods of filling an aneurysm include the use of balloon catheters, which in some cases can entirely occlude the vessel to be treated and stop blood flow. In many instances, the coils that are used are made of platinum, a relatively expensive metal which results in a non-degradable, permanent implant. 
         [0006]    There is a need for improved fillers for aneurysms and methods of delivering a biocompatible filler while having a minimal impact on the ordinary circulatory function of the patient to be treated. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    In one embodiment, a medical device comprising a catheter is described. The catheter includes a body comprising a proximal portion extending to a distal portion, the proximal portion having a proximal end and the distal portion having a distal end, the body comprising an exterior surface and a lumen formed therethrough between the proximal end and the distal end and, the distal portion being an anchoring portion comprising at least one bend formed thereon. 
         [0008]    In another embodiment, a catheter is described. The catheter has a body including a proximal portion extending to a distal portion, the proximal portion having a proximal end and the distal portion having a distal end, the body comprising an exterior surface and a lumen formed therethrough between the proximal end and the distal end and, the distal portion comprising a plurality of anchoring elements formed on the exterior surface and extending toward the proximal end of the catheter. 
         [0009]    In another embodiment, the invention comprises a method of deploying a catheter and filling an aneurysm, the aneurysm being in a body vessel in which a medical implant has been placed adjacent a neck region of an aneurysm. The method comprises the steps of introducing a catheter in the blood vessel, the catheter comprising a distal portion having a distal end and at least one anchoring element on the distal portion for enhanced placement of the distal end, positioning the distal end within the aneurysm, anchoring the at least one anchoring element to the medical implant; and delivering a filling agent through the distal end to the aneurysm for treatment thereof. 
         [0010]    In another embodiment, the present disclosure describes a catheter. The catheter includes a body comprising a proximal portion extending to a distal portion, the proximal portion having a proximal end and the distal portion having a distal end, the body comprising an exterior surface and a lumen formed therethrough between the proximal end and the distal end and, the distal portion comprising at least one slit formed through the body from the exterior surface to the lumen. 
         [0011]    Further objects, features, and advantages of the present invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A-1C  are perspective views of a prior art catheter filling an aneurysm; 
           [0013]      FIG. 2A  is a perspective view of an inventive catheter with anchoring members at its distal tip filling an aneurysm in accordance with the principles of the present invention; 
           [0014]      FIG. 2B  is a close-up view of the plurality of anchoring members and distal tip of the catheter of  FIG. 2A ; 
           [0015]      FIG. 2C-2E  are close-up view (side view, head-on view, and perspective views, respectively) of the distal tip of  FIG. 2B ; 
           [0016]      FIG. 2F  is a perspective view of a modification to the distal tip of  FIG. 2A  for a catheter according to a further embodiment of the present invention; 
           [0017]      FIG. 3A  is a perspective view of another distal tip of a catheter in accordance with another embodiment of the present invention; 
           [0018]      FIG. 3B  is a perspective view of a modification to the distal tip of  FIG. 3A  in accordance with a further embodiment of the present invention; 
           [0019]      FIG. 3C  is a close-up view of a distal end of a catheter in accordance with a further embodiment of the present invention; 
           [0020]      FIG. 3D-3E  are schematic views of the catheter depicted in  FIG. 3C ; 
           [0021]      FIG. 4A  is a perspective view of an inventive catheter with a slitted distal end according to one embodiment of the present invention; and 
           [0022]      FIG. 4B  is a perspective view of an inventive catheter with a different slit configuration at its distal end in accordance with another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The description that follows is not intended to limit the scope of the invention in any manner, but rather serves to enable those skilled in the art to make and use the invention. 
         [0024]    It is to be understood that the figures are schematic and do not show the various components to their actual scale. In many instances, the figures show scaled up components to assist the reader. 
         [0025]    In this description, when referring to a device, a catheter, or a medical implant, the term distal is used to refer to an end of a component which in use is furthest from the physician during the medical procedure, including within a patient. The term proximal is used to refer to an end of a component closest to the physician and in practice in or adjacent an external manipulation part of the deployment or treatment apparatus. 
         [0026]    The terms “substantially” or “about” used herein with reference to a quantity includes variations in the recited quantity that are equivalent to the quantity recited, such as an amount that is equivalent to the quantity recited for an intended purpose or function. In the case of a numerical quantity, the terms “substantially” or “about” shall mean a range consisting of a value 50% less than the recited value to a value 50% greater than the recited value, inclusive. 
         [0027]    It is to be understood that any type of catheter is meant when the term “catheter” is used in this disclosure, inclusive of microcatheters. 
         [0028]      FIG. 1A-1C  is a sequential diagrammatic representation of one problem to be solved by an inventive catheter. In  FIG. 1A , aneurysm  15  is formed off of the vessel wall  11  of blood vessel  10 . Medical implant (or stent)  20  has been placed across the length of the aneurysm  15 , creating a portion of the lumen  13  of the blood vessel  10  which is distal to the aneurysm (distal vessel portion  14 ) and a portion which is proximal to it (proximal vessel portion  12 .) 
         [0029]    The stent  20  has a stent structure made of interconnected struts and connecting segments. There are empty spaces  22  within the framework of the stent, and in particular a catheter  30  can be passed through a catheter space  24  to enter the aneurysm. In doing this, the catheter  30  forms bend  32 , which in  FIG. 1A  is depicted as being about 90 degrees. 
         [0030]    The catheter has a proximal end closest to the practitioner and a distal end farthest from the practitioner, and a catheter lumen is defined therethrough and extending from the proximal end to the distal end. Further, a longitudinal axis is defined within the tubular-shaped catheter. 
         [0031]    The catheter has a distal tip  34  at the distal end of the catheter. This distal tip  34  can either be unitarily formed with the remainder of the catheter body, or it can be a separate part which is attached to the catheter body by any conventional means, reversibly or irreversibly. The distal tip  34 , at its extreme distal end, is where exit port  35  is formed. 
         [0032]    In the embodiment of  FIG. 1A , a fiber or filamentary material is being used to fill the aneurysm. The filamentary material could be of any type deemed suitable for performing a medical function and could be a polysaccharide, a biocompatible polymeric thread, or other biocompatible material. Specific examples include but are not limited to: woven polyester (such as DACRON®); polyamide (such as Nylon); expanded polytetrafluoroethylene (ePTFE, GORE-TEX®); and bioremodelable materials such as extracellular matrix (ECM) material, such as submucosa, renal capsule membrane, dermal collagen, dura mater, pericardium, fascia lata, serosa, peritoneum, and basement membrane layers. Examples of submucosa include intestinal submucosa, stomach submucosa, urinary bladder submucosa, and uterine submucosa. 
         [0033]    In one embodiment, this fiber may be made of a biological material. In a specific embodiment, the biological material may be derived from extracellular matrix (ECM) or small intestinal submucosa (SIS). The biological material is formed into a thin fiber and provided on a bobbin or spool within a handle portion of a catheterization device. The spool may have just one fiber wound around it, or may hold two fibers, or any other number of fibers depending on the needs of the application. 
         [0034]      FIG. 1A  illustrates a point in time at which fiber  40  has just been forced from the catheter body through exit port  35 . A receptacle containing a substantial amount of the fibrous material may be part of the system. Such a receptacle can, for instance, be substantially spherical, and may therefore contain a substantially spherical spool of fibrous material, free to rotate in any direction, within it. Ejecting the material can be done by providing a pressurized liquid, such as saline solution, through the catheter  30  in order to force the fiber  40  out of the catheter and into the aneurysm  15 . In another embodiment, rather than a spooled SIS fragment or other biological material, the filler is a series of platinum coils which are loaded consecutively in the catheter. 
         [0035]    Further progression of this process is shown in  FIG. 1B . At this point, most of the filler is out of the catheter, and the aneurysm  15  is becoming quite full. Thus, the procedure has nearly concluded. 
         [0036]    However, a problem emerges and the result is shown in  FIG. 1C . When the aneurysm is nearly full, spatial constraints and/or pressure cause the catheter distal tip  34  to be dislodged and in some cases completely removed from the aneurysm. This can lead to the delivery of filler outside of the aneurysm, underfilling of the aneurysm, and other issues. 
         [0037]    To solve this problem, the catheter  130  of  FIG. 2A  has been given hooks or prongs  150 . In one embodiment, there is one hook  150  present at the distal portion  134  of the catheter  130 . In another embodiment, there are at least two hooks  150  circumferentially spaced at any convenient interval around the distal portion  134 . When the prongs  150  engage the stent  120 , the added pressure and special constraints as the aneurysm  115  fills with fiber  140  does not permit the catheter  130  to dislodge; rather, the hooks  150  catch on the stent and the catheter stays in place. 
         [0038]      FIG. 2B  is a close up view of the plurality of hooks  150  which are formed on the exterior surface of the distal portion  134  of the catheter. These hooks jut out from the catheter body and in the depicted embodiment, point back in the proximal direction. The hooks may be made of any material—a plastic, a rubber, a shape memory metal, or the like—so long as it is strong enough to withstand the additional pressure imparted by the filling process. In one embodiment, the prongs  150  are made of a resilient but flexible material, such that a pushing force generated by the filling of the aneurysm keeps the hooks  150  in their original shape, but a stronger pulling force in the proximal direction, such as by the hand of the practitioner conducting the procedure, causes the hooks  150  to start to bend distally such that the catheter can be retracted from the body of the patient. 
         [0039]    The plurality of anchoring elements or prongs  150  can be of a variety of designs. In one embodiment, the prongs or anchoring elements may be formed on the exterior surface of the catheter at an anchoring point, and the anchoring elements extend proximally from the anchoring point toward the proximal end of the catheter. In such an instance, the anchoring element does not extend distally beyond the distal end of the catheter body. In another embodiment, no portion of the anchoring element extends distally beyond the anchoring point. 
         [0040]    In one embodiment, the anchoring elements are formed at the distal end of the catheter body. In another embodiment, the anchoring elements are formed on the distal portion of the catheter, but proximal to the distal end. 
         [0041]    In one embodiment, an anchoring element is preformed and then attached to the catheter body, such as by an adhesive. 
         [0042]    In one embodiment, the catheter body has a substantially constant wall thickness from the proximal end of the catheter body to the distal end of the catheter body. In this case, the size of the lumen is unchanged from the proximal end at any point at which a cross section is taken. In such a case, the thickness of the wall of the catheter may also be uniform at least through the part of the distal portion at which the anchoring elements are formed. In other cases, the catheter may taper toward the distal end, but at or proximal to the portion where the anchoring elements have been formed. In some embodiments, the anchoring elements may be formed of the side wall of the catheter body. 
         [0043]    In one embodiment, the anchoring elements are individually and unitarily formed, with no portion of one anchoring element being in contact with another anchoring element. The anchoring elements may be separately formed from one another. Because there may be limited space such as between struts of a medical implant that is positioned at the neck of the aneurysm to be treated, the anchoring elements should be sized such they are able to be positioned within the structure of the implant, and can provide enhanced positioning and anchoring thereon. Hence, the anchoring element should not be interconnected with another element, such as by a webbing or a woven element, or any other structural support that will impede interaction with the implant. 
         [0044]    In one embodiment, the catheter may be formulated comprising polyurethane as a structural binder (i.e. resin) ingredient, for example polyether-polyurethane or polyester-polyurethane. The plastic formulation that makes up the remainder of the catheter can comprise a structural binder ingredient that is sealingly compatible with polyurethane, or if the tip is other than polyurethane, then the structural binder ingredient can be sealingly compatible with any material which constitutes the structural binder of the distal tip. Generally, the structural binders of the distal tip and the remainder of the catheter comprise the same, or similar, formulations for the best sealing compatibility; i.e. when the distal tip comprises polyurethane, the remainder of the catheter also comprises polyurethane. 
         [0045]    The distal tip and the remainder of the catheter body to comprise polyurethane, but other inert plastic materials besides polyurethane may be used to manufacture catheters, for example, polyethylene, poly(ethylene terephthalate) and other polyesters, polypropylene, polyamides such as nylon, and the like. 
         [0046]    Additionally, radiopaque elements can be used in portions of the catheter to aid in visualization of the process for which the catheter is employed. Radiopaque elements can be used solely toward the distal tip region, or can be placed at intervals through the length of the catheter. 
         [0047]      FIG. 2C-2E  illustrate an embodiment in which the anchoring elements are represented by six hooks. The hooks are oriented such that they point back in the proximal direction. The six hooks are spaced substantially evenly around the circumference of the catheter body, with approximately 60 degrees separating the anchoring elements. They lie adjacent the exit port  135  formed at the end of the distal portion  134 . 
         [0048]    Turning now to  FIG. 2F , a modification to the distal tip of the catheter of  FIG. 2A-2E  is illustrated. In this embodiment, the catheter has two sets of anchoring members, in this case hooks, placed around its exterior at its distal portion  134 . The first set of hooks  150   a  is more distal than the second set of hooks  150   b . The first set of hooks  150   a  creates a first set of implant contact points at a first location  151  near the distal end of the catheter. The second set of hooks  150   b  creates a second set of implant contact points at a second location  155  proximal to the distal end of the catheter. The length between first location  151  and second location  155  is represented as a length X. Such a configuration can allow for variable placement of the catheter for improved filling and adjustment depending on the depth of the aneurysm. In another aspect, the multiple sets of hooks  150   a  and  150   b  can allow for a stronger grip on the implant by providing multiple points of contact on the structure of the implanted device. 
         [0049]    In another embodiment, the catheter has three sets of anchoring members at its distal tip region in a similar configuration to those shown in  FIG. 2F . In a further embodiment, the catheter has four sets of anchoring members arranged circumferentially around the distal tip region of the catheter at different distances from the distal end. Further embodiments can include five sets of anchoring members, six sets of anchoring members, or more than six sets of anchoring members. 
         [0050]    Another embodiment of the present invention is shown in  FIG. 3A . In this embodiment, the anchoring elements of catheter  230  are represented by flared flaps  260 . The flaps  260  lie adjacent the exit port  235  of the catheter  230  at its distal tip  234 . The flaps can be cut from the wall of the catheter  230  and biased to flare away from the catheter body when unconstrained. The flaps create a space  262  which is in fluid communication with the lumen of the vessel. Such fluid communication may assist in the operation of the device, for example by allowing for release of pressure or excess filling fluid, which would otherwise cause dislodging of the distal end of the catheter. 
         [0051]    In the embodiment of  FIG. 3A , the flaps can catch on the strut structure of a foraminous medical implant at an aneurysm, such as a stent, or they can serve to simply increases the diameter of the device when it has passed through an opening in the implant. However, the flaps  260  must be pliant enough that a practitioner can still effect removal of the catheter  230  while providing a force in the proximal direction. The flaps  260 , also allow for pressure release, as excess saline solution or other loading fluid can be at least in part expelled via spaces  262 . 
         [0052]    The depicted embodiment of  FIG. 3A  only shows a cylindrical catheter with two flaps, but other configurations can include more, such as 3, 4, 5, 6, 8, or more flaps  262 . 
         [0053]    Turning now to  FIG. 3B , a modification to the distal tip of the catheter of  FIG. 3A  is illustrated. In this embodiment, the catheter has two sets of flaps cut or formed around its exterior at its distal tip region  234 . The first set of flaps, comprising flaps  260   a  and  260   b , is more distal than the second set of flaps, comprising flaps  260   c  and  260   d . The first set of flaps  260   a / 260   b  creates a first set of implant contact points within spaces  262   a  and  262   b  at a first location  261  near the distal end of the catheter. The second set of flaps  260   c / 260   d  creates a second set of implant contact points within spaces  262   c  and  262   d  at a second location  265  proximal to the distal end of the catheter. The length between first location  261  and second location  265  is represented as a length X. Such a configuration can allow for variable placement of the catheter for improved filling and adjustment depending on the depth of the aneurysm. In another aspect, the multiple sets of flaps  260   a / 260   b  and  260   c / 260   d  can allow for a stronger grip on the implant by providing multiple points of contact in spaces  262   a / 262   b / 262   c / 262   d  on the structure of the implanted device. 
         [0054]    In another aspect, the number of flaps cut or formed in one set, circumferentially, in the distal tip region  234  of the catheter  230  can be three. In another aspect, the number can be four. There can also be five, six, eight, or more flaps in such arrangements. The number of flaps  260   a  does not have to be equal to the number of flaps  260   b , nor do their positions circumferentially around the catheter have to align. 
         [0055]    In another embodiment, the catheter has three sets of flaps at its distal tip region in a similar configuration to those shown in  FIG. 3B . In a further embodiment, the catheter has four sets of flaps arranged circumferentially around the distal tip region of the catheter at different distances from the distal end. Further embodiments can include five sets of flaps, six sets of flaps, or more than six sets of flaps. 
         [0056]      FIG. 3C-3E  illustrate another embodiment of the device of the present disclosure. Here, the anchoring elements comprise bends in the distal tip  334  of the catheter  330 . The catheter  330  has a proximal end, then a first bend  332  of about 90 degrees. Following the catheter body distally, second bend  333  is formed distal to first bend  332 , and is also about 90 degrees. Distal to second bend  333  is third bend  336 , which is also about 90 degrees, and fourth bend  338  which is a final bend of about 90 degrees. 
         [0057]    The angles of these bends need not be 90 degrees; any configuration of bends in the distal tip  334  of a catheter  330  which will allow it to be locked into position when deployed in an aneurysm for filler delivery will suffice. In one embodiment, the distal tip  334  is made of a shape memory material that can be straightened but maintains a bent configuration as illustrated. 
         [0058]    The catheter tip may comprise at least one shape memory material. Shape memory materials reversibly transform between a lower temperature phase (martensite) and a higher temperature phase (austenite) while passing through a transition temperature therebetween. Shape memory alloys have the desirable property of becoming rigid when heated above the transition temperature. 
         [0059]    A shape memory alloy suitable for the present invention is an alloy comprising nickel and titanium. When a nickel-titanium shape memory alloy is heated above the transition temperature, the material undergoes a phase transformation from martensite to austenite, such that the material starts with a substantial amount of elasticity but at the transition temperature begins to become rigid. The transition temperature is dependent on the relative proportions of the alloying elements nickel (Ni) and titanium (Ti) and the optional inclusion of alloying additives. Often the proportions of Ni and Ti are selected so that the material is austenite at body temperature. 
         [0060]    To deploy the catheter  330  through the structure of the medical implant or stent  320 , in one embodiment the distal tip  334  is straightened.  FIG. 3D  shows straightening with a straightening member  370 . In one embodiment, the straightening member  370  is a wire guide. In another embodiment, the straightening member  370  is an inner dilator.  FIG. 3E  shows the tip reverting to its heat-set shape after retraction of the straightening member  370 . This allows the distal tip region to catch within the aneurysm and resist the pressure as the aneurysm fills. 
         [0061]    In another embodiment, the anchoring members are not bends at the distal region, but a series of concentric loops, such as in a spiral. In another embodiment, a pigtail catheter configuration is employed. 
         [0062]      FIG. 4A  shows yet another embodiment of the present invention. Because one problem to be addressed by the anchoring element is resistance to pressure, a solution to this problem can reduction of pressure rather than adaptation to it. In this instance, slits  438  having slit boundaries  439  are cut or formed through the walls of the catheter  430 . These slits allow fluid to flow through so that additional pressure from fluids (such as excess saline flushing solution) in the aneurysm are allowed to escape the aneurysm as it fills. The slits  438  formed in distal tip  434  as illustrated in  FIG. 4A  do not extend all the way to the distal end of the catheter body and thus do not have fluid connections with exit port  435 , although they do have fluid connections with lumen  437 . This is shown by tip space  431 , surrounded by a dotted boundary, being of a solid construction. However, in another embodiment, such as the embodiment of  FIG. 4B , the slits  438  do continue all the way to the distal end. Such a variant may help to realize a higher release of fluid pressure due to greater flexibility at the distal end of the catheter body. 
         [0063]    In another embodiment, the inventive catheter tip may be formed as its own separate element and then attached to the distal end of any conventional catheter body. Thus, a catheter having an inventive tip structure may either be formed monolithically; have its anchoring elements (such as hooks) formed separately and attached to the distal end of a standard catheter; or a tip portion having a lumen and the anchoring elements formed thereon may be attached as one part, reversibly or irreversibly, to a separate catheter body. 
         [0064]    Further, the present invention can comprise a method of using a catheter having any of the foregoing inventive anchoring elements to fill an aneurysm. The method comprising a number of steps, the first of which is providing a medical implant (such as a stent with a strut structure) near a neck region of the aneurysm; providing a catheter as described throughout this disclosure and comprising at least one anchoring element formed thereon; introducing the catheter to the patient&#39;s body; positioning the exit port within the aneurysm; engaging the medical implant with the anchoring element (for example, in the case where the anchoring element is a hook, catching said hook on the wire struts of the stent already present in the body of the patient); filling the aneurysm with a filling agent, such as SIS fiber or platinum microcoils; and removing the catheter from the patient. 
         [0065]    A person having skill in the art will readily appreciate that the method will be adjusted based on the particular embodiment of the tip of the catheter. For instance, when a catheter having a slit rather than a hook is used, the method will not include a step of engaging the medical implant with the anchoring element; rather, the catheter will simply be passed into the aneurysm and fill it without such an engagement step. 
         [0066]    While the apparatus of the invention has been described above with reference to certain specific embodiments thereof, it is to be clearly understood that these embodiments have been given for purposes of illustration only and are not intended to be limiting. The scope of the invention is bounded only by the scope of the claims which are set out hereafter.