Abstract:
The disclosed methods and devices utilize various techniques to detach the distal end of a catheter from an obstruction with minimal invasiveness and effort by the surgeon. As reflux of an embolic agent or hardening material over the catheter tip is a major causative factor in the increased morbidity/mortality of embolization procedures and also a technical limitation preventing a better cure rate, a method has been developed for the detachment of the distal end of catheters within the body, preferably with no regard to the amount of reflux, and preferably at the proximal edge of the reflux, in order to be able to make embolization procedures safer and more effective.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. provisional application Ser. No. 60/789,782, filed on Apr. 6, 2006 and incorporated herein by reference in its entirety for all purposes. 
     
    
     BACKGROUND  
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to the field of catheters. More specifically, the invention relates to a method and apparatus for the treatment of vascular malformations, aneurysms, tumors, or hemorrhages.  
       BACKGROUND OF THE INVENTION  
       [0003]     Typical treatment of arteriovenous malformations (AVMs) involves endovascular treatment, surgery and radiotherapy. An AVM is a congenital disorder of the blood vessels in the brain, characterized by tangles of veins and arteries that lack the normal capillary structure. Currently the standard endovascular treatment involves obliteration of the malformation or the fistula with embolic agents such as cyanoacrylic glue, other proprietary materials (i.e. Onyx™) or in some cases by particles such as polyvinyl alcohol (PVA). Interventional treatment of tumors also involves the same endovascular tools.  
         [0004]     The chance for an endovascular cure with cyanoacrylates only is not high. This is mainly because of the technical difficulties related to the use of acrylic glue. This entails expertise, attention and adherence to a strict technique which was developed over the years to prevent either inadvertent embolization or gluing of the catheter to brain vessels. Among these two complications, gluing of the catheter tip is a well-recognized complication that may be distressing. In several series, this complication has been reported in up to 10% of procedures, sometimes with serious outcomes. The scarcity of literature data may as well be secondary to under-reporting of this complication with an unknown actual risk of permanent catheter fixation.  
         [0005]     When gluing of the catheter tip occurs, there are two methods for salvage. The first one is to leave the catheter in place, which is extending from the embolized lesion to the groin (access site). Although there are case reports documenting the incorporation of the retained catheters into the cerebral vasculature, it is also stated that epithelization does not occur quickly increasing the risk of thromboembolic events. The patients with the retained catheters need to be followed under anticoagulation or antiplatelet therapy which is not preferred in patients with cerebral vascular malformations. The number of embolizations that can be performed via the same vascular pedicle is also limited with this approach, as with each subsequent embolization, there will be the risk of retaining more than one catheter in intracranial arteries. The outcome of this approach is currently not well-known.  
         [0006]     The second method is to severe the catheter at its distal portion by pulling with a sudden thrust and leaving the distal fragment of the catheter in the cerebral vasculature. Despite the allegations of several authors that many patients tolerate this maneuver, major morbidity and mortality has been documented as a result of the performance of this maneuver either secondary to vascular avulsion/intracranial bleeding or to inadvertent embolization of polymerized glue by an adherent droplet being shorn from the tip of the microcatheter and as such, catheter fixation remains a highly undesirable event among endoneurovascular operators. Surgical removal of these catheters may sometimes be needed.  
         [0007]     The most important factor in preventing catheter adhesion is limitation or prevention of reflux along the microcatheter This not only requires considerable endovascular skills and expertise, but also limits the success of the embolization procedure. The penetration of the embolic agent into the target site is enhanced by the formation of an “intravascular plug” at the catheter tip. Generally, however, the formation of this plug necessitates a small reflux of the embolic agent along the catheter tip.  
         [0008]     Consequently, there is a need for a device which allows a surgeon to easily detach a catheter tip during treatment of AVMs.  
       BRIEF SUMMARY  
       [0009]     The disclosed methods and devices utilize various techniques to detach the distal end of a catheter from an obstruction with minimal invasiveness and effort by the surgeon. As reflux of an embolic agent or hardening material over the catheter tip is a major causative factor in the increased morbidity/mortality of embolization procedures and also a technical limitation preventing a better cure rate, a method has been developed for the detachment of the distal end of catheters within the body, preferably with no regard to the amount of reflux, and preferably at the proximal edge of the reflux, in order to be able to make embolization procedures safer and more effective.  
         [0010]     These and other needs in the art are addressed in one embodiment by a device comprising a catheter having an open distal end, wherein said catheter comprises a material having a melting point. The device also includes a heating element disposed at the distal end of said catheter, where the heating element causes the distal end to detach by the heating of said distal end to at least the melting point of said material.  
         [0011]     In an embodiment a device comprises a catheter having an open distal end. The device also comprises a support member disposed parallel to the catheter. The device further comprises a means of detaching said open distal end from said catheter coupled to the support member. The means of detaching said open distal end form said catheter may be a mechanical means or a chemical means.  
         [0012]     In yet another embodiment, a method comprises inserting a catheter having an open distal end. The method additionally comprises injecting a hardening material through the open distal end to form an obstruction. Moreover, the method comprises positioning a heating element at the open distal end. The method also comprises heating at least a portion of the open distal end using the heating element so as to detach the catheter from the open distal end and the obstruction.  
         [0013]     According to an embodiment, a method comprises inserting a catheter having an open distal end. The method additionally comprises injecting a hardening material through the open distal end to form an obstruction. The method further comprises positioning a means for detaching the catheter from the obstruction at the distal end. The means of detaching said open distal end form said catheter may be a mechanical means or a chemical means. In addition, the method comprises using the mechanical or chemical means to detach the catheter from the obstruction.  
         [0014]     The foregoing has outlined the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form various embodiments of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     For a detailed description of the embodiments of the invention, reference will now be made to the accompanying drawings in which:  
         [0016]     FIGS.  1 ( a )-( c ) illustrates various embodiments of a device with a heating element;  
         [0017]      FIG. 2  illustrates an embodiment of a device with a heating element; and  
         [0018]     FIGS.  3 A-B illustrates an embodiment of a device with a mechanical means of removing the catheter from an obstruction;  
         [0019]      FIG. 4  illustrate an embodiment of a device with a mechanical means of removing the catheter from an obstruction;  
         [0020]      FIG. 5  illustrates an embodiment of a device with an inner mechanical means of removing the catheter from an obstruction;  
         [0021]      FIG. 6  illustrates an embodiment of a device with an optical source for detaching distal end of a catheter from an obstruction;  
         [0022]      FIG. 7  illustrates an embodiment of a device utilizing a chemical substance to remove distal end of a catheter from an obstruction;  
         [0023]      FIG. 8  illustrates an experimental setup for testing embodiments of the device; and  
         [0024]      FIG. 9  is a plot of temperature versus time at the distal end of the device. 
     
    
     Notation and Nomenclature  
       [0025]     Certain terms are used throughout the following description and claims to refer to particular system components. This document does not intend to distinguish between components that differ in name but not function.  
         [0026]     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]      FIG. 1  illustrates various embodiments of a vascular device for treating vascular abnormalities such as AVMs, aneurysms, tumor vessels or bleeding sites. In an embodiment, the device  100  comprises a catheter  101  and an open distal end  103 . As defined herein, a catheter is any conduit or hollow body that may be inserted into the vasculature of a patient. Typically, catheter  101  is inserted over a guide wire (not shown). However, it is contemplated that other embodiments of the device  100  do not require use of a guide wire. The catheter  101  may be made of any suitable biocompatible material. Examples of suitable materials include plastics, copolymers, alloys, metals and the like. Examples of polymers or plastics that the catheter may be made include without limitation, polyethylene, polypropylene, polyurethane, silicone rubber, and the like. Such materials traditionally have a relatively low melting point. As used herein, melting point is the temperature at which a material begins to change from solid to liquid. In addition, device  100  may comprise any catheter  101  that is commercially available and currently used by those of skill in the art.  
         [0028]     In a further embodiment, device  100  comprises a heating element  107  disposed at distal end of catheter  101 . According to an embodiment, heating element  107  is disposed within distal end  103  of catheter  101  as shown in  FIG. 1 ( a ). Alternatively, heating element  107  may be disposed circumferentially around distal end as shown in FIGS.  1 ( b )-( c ) to form a heating lasso or loop. Heating element  107  serves to detach distal end  103  from catheter  101  by site-specific melting of catheter  101  near heating element  107 , thereby detaching distal end  103  from catheter  101 .  
         [0029]     Heating element  107  is typically coupled to a power source  131  via a support member  109  which is preferably longitudinally coaxial or parallel to catheter  101 . Typically, support member  109  is a wire which provides power to heating element  107 . However, support member  109  may be any structure that allows positioning of heating element  107  to the desired location of the catheter  101 . Depending on the embodiment, support member  109  may be disposed external to catheter  101  as shown in  FIG. 1 ( a ) or may be disposed within catheter  101  as in FIGS.  1 ( b )-( c ). In embodiments where support member  109  is disposed externally to catheter  101 , support member  109  may be run through an auxiliary catheter  112 . Auxiliary catheter  112  may be positioned parallel to catheter  101 . Alternatively, an outer or guiding catheter  114  may be disposed coaxially around catheter  101 , support member  109 , and heating element  107 . In an embodiment, support member  109  comprises a waveguide to pass a beam of light to heating element  107 . In other embodiments, support member  109  comprises a conductive metal such as without limitation, platinum, gold, silver, copper, or combinations thereof  
         [0030]     Referring now to  FIG. 2 , heating element  107  may be attached to the balloon portion  118  of a balloon catheter  110 . In this embodiment, balloon catheter  110  is disposed coaxially within catheter  101 . When balloon portion  118  of balloon catheter  110  is expanded, heating element  107  may be brought into close proximity with the catheter wall. When balloon portion  118  is deflated, heating element  107  may also contract. When heating element  107  is activated in balloon catheter&#39;s expanded state, the increase in temperature causes detachment of distal end  103  from catheter  101  by melting. Preferably, balloon portion  118  is made of a heat-resistant material such that as heating element  107  heats catheter  101 , balloon portion  118  remains intact. Any suitable heat-resistant materials known to those of skill in the art may be used.  
         [0031]     Heating element  107  may comprise any number of devices known to cause an increase in temperature. Examples of such devices including high resistance coils, lasers, radiofrequency emitter, microwave devices, ultrasound devices, etc. Power is provided to heating element  107  by power supply  131 . Power supply  131  may be any apparatus known to those of skill in the art that provides power. Examples include without limitation, batteries, DC power unit, generators, solar power, AC power supplies, or combinations thereof.  
         [0032]     In an embodiment, device  100  includes a temperature probe disposed at distal end  103  of catheter  101 . Temperature probe may be any device used to monitor temperature or provide temperature information. The temperature probe may be coupled to power supply  131  to provide a feedback loop for heating element  107 . The feedback loop serves to prevent power supply  131  from overheating element  107  and causing damage to the vasculature.  
         [0033]     As illustrated in  FIGS. 3-5  and  6 , embodiments of the device may comprise a means for detaching the distal end of catheter from an obstruction or embolism. The means for detaching the distal end of catheter from an obstruction or embolism may be a chemical means or a mechanical means. As used herein, mechanical means refers to any means using physical force (i.e. cutting, friction) to detach distal end of catheter. On the other hand, chemical means refers to any means of using a chemical substance or fluid to dissolve the catheter wall to detach distal end of catheter.  
         [0034]     Referring now to  FIG. 3 , according to an embodiment, catheter  201  may include an elongate support member  209  running longitudinally along catheter body  201 . Elongate member  209  typically comprises a wire. Furthermore, mechanical means may comprise a loop  207  surrounding distal end of catheter. In an embodiment, loop  207  is coupled to elongate support member  209 . Elongate member  209  serves to mechanically move loop longitudinally along catheter  201 . As described above, elongate member  209  may also be disposed within auxiliary catheter  212 .  
         [0035]     Now referring to  FIG. 4 , in an embodiment, loop  407  or lasso may comprise a plurality of cutting elements  411  such as without limitation, teeth or blades. Loop  407  may additionally include a noose or other mechanism to tighten loop around catheter. As loop  407  is tightened, plurality of cutting elements  411  engage catheter  401  and cut distal end  403  from catheter  401 . That is, the tightening of loop  407  serves to detach distal end  403  from catheter  401 .  
         [0036]     In an embodiment, mechanical means  507  may be disposed within catheter  501  as shown in  FIG. 5 . For example, mechanical means  507  may comprises an inner cutting element  506  that is coupled to an inner support member  502 . In one aspect, inner support member  502  comprises an inner catheter. According to one embodiment, inner cutting element  506  may be expandable i.e. having an expanded position and a collapsed position. In particular, inner cutting element  506  may comprise an expandable disk. Moreover, inner cutting element  506  may have sharpened or serrated edges  508  to cut through the catheter wall. In an embodiment, inner cutting element  506  comprises a plurality of overlapping leaves  512  which contract and expand radially. Alternatively, inner cutting element  506  may comprise an umbrella-type configuration in which inner cutting element  506  collapses and folds against inner support member  502 .  
         [0037]     Referring to  FIG. 6 , in yet another embodiment, the device may utilize a laser to detach the distal end  603  of catheter  601 . A laser beam  621  may be directed down a waveguide  602  which is inserted coaxially into catheter  601 . According to an embodiment, waveguide  602  comprises a fiber optic cable. Distal end  619  of waveguide  602  may also comprise a beam splitter  620 . Splitter  620  may split beam  621  into a plurality of beams directed at the catheter  601  wall. Furthermore, splitter  620  may comprise at least two different glass elements  622 ,  624  with refractive indices n 1  and n 2  , respectively, may be disposed at the distal end  619  of waveguide  602 . Glass element  624  may have a conical shape and a tip angle, α, in which α is selected so that the incoming laser beam  621  is directed to the inner surface of catheter  601 . The re-directed beams heat the inner surface of catheter  601  so as to melt the catheter wall and detach distal end  619 .  
         [0038]     According to an embodiment, device  700  comprises an inner catheter  702  having a closed distal tip  716  (See  FIG. 7 ). Distal tip  716  of the inner catheter  702  may comprise a plurality of openings  714  on its outer surface. In an embodiment, the plurality of openings  714  are arranged circumferentially around inner catheter  702  at the distal end  716  of catheter  702  in a band. However, openings  714  may be arranged in any configuration which may optimally allow ejection of a chemical substance for detachment of distal end  703  of catheter  701 . Distal end  716  is generally closed so as to allow ejection of fluid from openings  714  to inner surface of catheter  701 .  
         [0039]     In an embodiment of a method, the above disclosed device  100  is inserted through the vasculature to the site of the AVM or other vascular abnormality. The device  100  may be inserted with the assistance of a guide wire. In addition, the method may comprise injecting a hardening material (i.e. an embolic agent) through catheter  101  to the AVM to form an obstruction. The obstruction prevents blood from reaching the AVM.  
         [0040]     Any suitable material known to those of skill in the art may be used. Examples of suitable materials include without limitation, cyanoacrylate glue, acrylic glue, fibrin glue, adhesives, hydrogels, polymers, or combinations thereof. Recently a commercial precipitating agent or hardening material, Onyx™, has been approved for the endovascular treatment of AVMs. Since this agent is non-adhesive, it permits prolonged injections for embolization. It has become apparent that using this agent with its fall potential entails an intentional reflux of this material at the catheter tip to be able to form an “intravascular plug.” This permits a higher rate of penetration to AVMs with a higher obliteration rate, at the expense of entrapment (instead of adhesion) of the catheter within the vessels in as much as 10% of the lesions embolized in a randomized controlled trial. A shift from the manufacturing of flow guided catheters to that of over-the-wire catheters was noted on the side of the company producing this embolic agent as the latter maybe recovered better in case entrapment occurs.  
         [0041]     As the hardening material sets to form a solid obstruction to the AVM or other vascular deformity, the distal end  103  of catheter  101  may be entrapped by the material. Heating element  107  is then guided either through or over catheter  101  to the AVM site as shown in FIGS.  1 ( a )-( c ). Power may be applied to heating element  107  through support member  109  and power supply  131  to heat heating element  107 . The heating element  107  causes an increase in temperature to the melting point of the catheter material, which melts only the portion of catheter  101  in close proximity to heating element  107 . Generally, heating element  107  completely melts through catheter wall, completely detaching distal portion  103  from catheter  101 . However, in some embodiments, heating element  107  may only melt a portion of catheter  101 , causing distal portion  103  to be partially detached from catheter  101 . Once heating element  107  has been either completely or partially detached, catheter  101  may then be removed from distal portion  103 , leaving distal portion  103  entrapped by the hardening material. As shown in FIGS.  1 ( a )-( c ), heating element  107  may heat or melt catheter from the inside or outside of catheter  101 .  
         [0042]     In an embodiment, after hardening material is injected and set, a balloon catheter  110  including heating element  107  may be inserted through catheter  101  as shown in  FIG. 2 . Typically, balloon catheter  110  is inserted with balloon portion  118  in its deflated state. Balloon portion  118  may then be expanded, bringing heating element  107  in close proximity to catheter  101 . Voltage or current is applied to heating element  107  to melt the portion of catheter  101  near heating element  107 . Any suitable voltages or currents may be applied to heating element  107 . Distal end  103  may then be detached from catheter  101  and catheter  101  along with balloon catheter  110  may be withdrawn from the vasculature.  
         [0043]     Balloon portion  118  is preferably made of a heat resistant material such that when heating element  107  is heated, balloon portion  118  remains intact and unaffected by the rise in temperatures. An example of such a material includes without limitation, silicone rubber.  
         [0044]     As depicted in  FIG. 6 , in another aspect of the method, after hardening material has set or cured, a heating element  607  utilizing an optical or laser source may be inserted through catheter  601 . The distal end of heating element  607  is positioned at the desired location. When properly positioned, a laser beam  621  may be directed down the waveguide  602 . Beam splitter  619  divides beam into multiple beams  626  and directs these beams to inner portion of catheter  601 . The plurality of beams  626  heat at least a portion of the catheter wall to either detach or partially detach distal end  603  from catheter  601 .  
         [0045]     In other embodiments, a chemical or mechanical means may be used in place of heating element  107  to detach or partially detach distal end of catheter. For example, a device  200  as shown in FIGS.  3 A-B is inserted into the vasculature. As explained above, hardening material is then injected through catheter  201  to form an obstruction  290  or embolus. If distal tip  203  of catheter  201  is trapped by the hardened obstruction  290 , a user may use support member  209  and loop  207  to mechanically force distal end  203  from obstruction  290  as shown in  FIG. 3 . That is, the force of the support member  209  and loop  207  pushing against the obstruction  290  provide leverage for user to pull catheter  201  from obstruction  290 .  
         [0046]     In an embodiment, a device  400  with loop  407  which includes a plurality of cutting elements  411  (see  FIG. 4 ) may be used in accordance with the methods described above. After the material hardens, loop  407  may be tightened around distal end  403  of catheter  401  using a wire  409 . The plurality of cutting elements disposed on loop  407  then sever or cut distal end  403  from catheter  401 , allowing withdrawal of catheter  401  from the vasculature. In some cases, loop  407  may be rotated around catheter  401  to cut into the catheter wall.  
         [0047]     In an alternative embodiment, a device  500  as shown in  FIG. 5  may be used. After injection and hardening of the hardening material, inner support member  502  coupled to inner cutting element  508  is inserted through catheter  501 . The inner cutting element  506  may be in a collapsed state to facilitate insertion to distal end  503  of catheter  501 . Once inner cutting element  508  is inserted to its desired position, inner cutting element  506  may be expanded to its expanded position. Inner cutting element  506  may have a diameter which is equal or greater than catheter  101 . Inner cutting element  506  may then be rotated to cut or detach distal end  503  from catheter  501 .  
         [0048]     In another embodiment, a device  700  utilizing a chemical means, as shown in  FIG. 7 , may be used in conjunction with the method. Once the hardening material has been injected and allowed to cure, an inner catheter  702  may be inserted into catheter  701 . A chemical substance  718  may then be injected into inner catheter  702  via a syringe or other device. Chemical substance  718  may be forced through the plurality of openings  714 , which may eject the chemical substance in a radial direction toward inner portions of the catheter  701 , as shown in  FIG. 7 . Once ejected, chemical substance  718  may dissolve a portion of the catheter  701  and, thus, either completely or partially detach distal end  703  from catheter  701 . Examples of chemical substances  718  include without limitation, solvents, acids, or combinations thereof The chemical substance  718  is preferably biocompatible and non-toxic. Once chemical substance  718  has dissolved at least a portion of the catheter  701 , the proximal portion of catheter  701  may then be removed from the hardened material, leaving the distal end  703 .  
         [0049]     It is envisioned that the above methods and devices will not be limited to embolus applications, but may also be used to detach the balloon portions of a balloon catheter or also puncture intravascular devices such as catheters, stents, stent-grafts, covered stents, or surgical grafts.  
         [0050]     To further illustrate various illustrative embodiments of the invention, the following example is provided.  
       EXAMPLE  
       [0051]     An experimental setup for the testing of the detachment procedure was constructed, which can be seen in  FIG. 8 . As shown in  FIG. 8 , a plastic tube  801  was used to simulate an artery, a catheter  803  with non-braided tip and an embolic agent (Onyx® 18 or 50% acrylic glue, Histoacryl® [n-butyl cyanoacrylate in Lipiodol®]) was used and placed in to a water bath  805 . The tip of the catheter  803  was positioned within the tube  801  and embolic agent was injected through the catheter to fill the tube. The lumen of the catheter  803  was then flushed with DMSO or D5W for Onyx and glue respectively.  
         [0052]     A Micrus-10 coil (with the coil detached)  811  was then advanced into the catheter  803  so that its tip was located within or just adjacent to the embolic cast. A fiber optic temperature probe  807  (FISO Technologies, Ste. Foy, Quebec, and Canada) was inserted near the tip of the coil pusher, which was also connected to the data acquisition device  813  to directly monitor the temperature on the screen of the computer  815 . The Micrus-10 wire  811  was connected to a DC switching power supply  817  and voltages from 5 Volts to 15 Volts were applied corresponding to different types of catheters. During the procedure, catheter detachments were visualized by fluoroscopic imaging.  
         [0000]     Results  
         [0053]     In the experiments, for the embolizations with ONYX, Ultraflow, Baltacci™ 18 and Fastracker® 325 catheters were used and for the embolizations with acrylic glue, Baltacci™, Spinnaker 18 and Ultraflow™ catheters were used. For the experiments, where the coil pusher was within the embolic cast, all the catheters could be detached successfully. On the other hand, no detachment was observed when the tip of the coil pusher was adjacent (outside) the embolic cast. This shows us that the correct placement of the coil pusher tip is crucial (carrying the electrical resistance coil) for a successful catheter detachment. Bubble formation from detachment of the catheters was observed with fluoroscopic imaging.  
         [0054]     During the experiments the catheter temperature at the detachment region was monitored continuously. Corresponding to the detachment of the Ultraflow catheter with input voltage of 10 volts, the temperature-time graph was observed in  FIG. 9 . Here, power was given for 25 seconds and detachment was successful. From  FIG. 9 , one can see that the maximum change in the temperature was around 14 degrees Celsius.  
         [0055]     In summary, independent of their brands, all of the catheters with non-braided tips could be detachable by the method that we have explained above. Furthermore this method can be applicable to puncture or ablate intravascular tools like endovascular balloons or stent grafts as well as tissues like vessel wall or membranous tissues.  
         [0056]     While embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.