Abstract:
A vascular occlusion device deployment system for placing an occlusion device at a preselected site within the vasculature of a patient. The deployment system employs a pusher including a gripper located at the distal end of the pusher to releasably retain a vascular occlusion device. The gripper is expanded under the force of a collapsible chemical reaction chamber so that the gripper releases the vascular occlusion device, thereby deploying the vascular occlusion device.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related to deployment systems and methods for accurately and rapidly deploying vascular occlusion devices at a preselected location within the vascular system of a patient, and more particularly, deployment approaches that utilize a pusher having an expandable gripper which is opened by the action of a collapsible chemical reaction chamber to facilitate rapid deployment of vascular occlusion devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    The use of catheter delivery systems for positioning and deploying therapeutic devices, such as dilation balloons, stents and embolic coils, in the vasculature of the human body has become a standard procedure for treating endovascular diseases. It has been found that such devices are particularly useful in treating areas where traditional operational procedures are impossible or pose a great risk to the patient, for example in the treatment of aneurysms in intracranial blood vessels. Due to the delicate tissue surrounding intracranial blood vessels, especially for example brain tissue, it is very difficult and often risky to perform surgical procedures to treat such a defect. Advancements in catheter deployment systems have provided an alternative treatment in such cases. Some of the advantages of catheter delivery systems are that they provide methods for treating blood vessels by an approach that has been found to reduce the risk of trauma to the surrounding tissue, and they also allow for treatment of blood vessels that in the past would have been considered inoperable. 
         [0003]    Typically, these procedures involve inserting the distal end of a delivery catheter into the vasculature of a patient and guiding it through the vasculature to a predetermined delivery site. A vascular occlusion device, such as an embolic coil, is attached to the end of a delivery member which pushes the coil through the catheter and out of the distal end of the catheter into the delivery site. Some of the problems that have been associated with these procedures relate to the accuracy of coil placement. For example, the force of the coil exiting the delivery catheter may cause the coil to over shoot the predetermined site or dislodge previously deployed coils. Also, once the coil is pushed out of the distal end of the catheter, the coil cannot be retracted and may migrate to an undesired location. Often, retrieving and repositioning the coil requires a separate procedure and has the potential to expose the patient to additional risk. 
         [0004]    In response to the above mentioned concerns, numerous devices and release mechanisms have been developed in an attempt to provide a deployment system which allows control of the occlusion device after the device has been delivered by the catheter and provides a rapid release or detachment mechanism to release the device once it is in place. One such device is disclosed in Geremia et al. U.S. Pat. No. 5,108,407, which shows a fiber optic cable including a connector device mounted to the end to the optic fiber. An embolic coil is attached to the connector device by a heat releasable adhesive. Laser light is transmitted through the fiber optic cable to increase the temperature of the connector device, which melts the adhesive and releases the embolic coil. One drawback to using this type of system is the potential risk of melted adhesives contaminating the blood stream. 
         [0005]    Another coil deployment system employs a pusher member having an embolic coil attached to the pusher member by a connector fiber which is capable of being broken by heat, as disclosed in Gandhi et al. U.S. Pat. No. 6,478,773. The pusher member of this arrangement includes an electrical resistance heating coil through which the connector fiber is passed. Electrical current is supplied to the heating coil by a power source connected to the heating coil via wires extending through an internal lumen of the pusher. The power source is activated to increase the temperature of the heating coil which breaks the connector fiber. One drawback is that connecting the resistance heating coil to the power source requires running multiple wires through the pusher member. Additionally, the electrical current traveling through the wires may create stray electromagnetic fields that interfere with other surgical and/or monitoring equipment. 
         [0006]    Yet another embolic coil positioning and delivery system is described in Saadat et al. U.S. Pat. No. 5,989,242, which discloses a catheter having a shape memory alloy connector attached to the distal end of the catheter. The connector includes a socket having a pair of spaced-apart fingers which are responsive to a change in temperature. The fingers are bent towards each other and hold a ball which is connected to an end of an embolic coil. The connector absorbs laser light transmitted through an optical cable and transmits the light into heat energy. The heat energy raises the temperature of the connector and opens the fingers, thereby releasing the embolic coil. This delivery system and the other above-identified delivery systems require electronic equipment powered by a power source. If the electronic equipment is defective or the power source fails, for example a battery pack fails, the procedure may be prolonged while the equipment is repaired or replaced. Prolonging the procedure may expose the patient to additional risk. This patent, and all other patents and references identified herein are hereby incorporated herein by reference. 
         [0007]    Therefore, a need remains for a rapid release vascular occlusion deployment system or method that does not rely on electrical equipment or a power supply, is simple to manufacture, flexible and easy to guide through the vasculature of the body, provides better control over the occlusion device, and reduces the possibility of interference with other surgical and/or monitoring equipment. 
       SUMMARY OF INVENTION 
       [0008]    The present invention embodies deployment systems and methods for accurately and rapidly deploying a vascular occlusion device at a preselected site within the vasculature of a patient. The deployment system may employ an elongated flexible delivery catheter for guiding a deployment unit to the preselected site. The deployment unit includes a pusher which has a gripper located at a distal end portion of the pusher. The gripper has an expandable gripping element, for example a plurality of gripping jaws, for releasably attaching a vascular occlusion device, such as an embolic coil, to the deployment system. The pusher guides the vascular occlusion device through the delivery catheter to the preselected site. 
         [0009]    A collapsible or contractible reaction chamber operatively communicates with the gripper. A first reactant is housed within the collapsible reaction chamber. The delivery system also includes a dispensing unit for dispensing a second reactant into the reaction chamber. When the second reactant is dispensed into the chamber, the first and second reactants react to form a product that has a volume that is less than the volume of the first reactant prior to reacting. The reduction of the volume occupied by the substances inside of the reaction chamber causes the pressure within the reaction chamber to decrease which results in a collapse of the reaction chamber. As the reaction chamber collapses, it pulls the proximal end of the gripping element inward causing the distal end of the gripping element to outwardly expand or open so that the gripping element releases the vascular occlusion device, thereby deploying the vascular occlusion device at the preselected location. 
         [0010]    Other aspects, objects and advantages of the present invention will be understood from the following description according to the preferred embodiments of the present invention, specifically including stated and unstated combinations of the various features which are described herein, relevant information concerning which is shown in the accompanying drawing. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    In describing the preferred embodiments of the present invention, reference will be made to the accompanying drawings, wherein: 
           [0012]      FIG. 1  is an enlarged, partially sectioned view of the vascular occlusion device deployment system of a preferred embodiment of the present invention; 
           [0013]      FIG. 2  is an enlarged partially sectioned view showing the distal end portion of the deployment system of  FIG. 1  prior to deployment of the occlusion device; 
           [0014]      FIG. 3  is an enlarged partially sectioned view of the distal end portion of the deployment system of  FIG. 1  shown just after deployment of the vascular occlusion device; and 
           [0015]      FIG. 4  is an enlarged partially sectioned view of the distal end portion of the deployment system of  FIG. 1  shown after deployment of the vascular occlusion device. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriate manner. 
         [0017]      FIG. 1  generally illustrates a preferred embodiment of the vascular occlusion device deployment system of the present invention. The deployment system, generally designated at  10 , includes an elongated flexible guiding catheter  12  which is inserted into the vascular system of a patient, such as blood vessel  13 , and used to guide a deployment unit, generally designed  14 , to a preselected site in a manner generally known in the art. The deployment unit  14  includes an elongated flexible pusher or delivery tube  16  having a proximal end portion  18  and a distal end portion  20 . 
         [0018]    As best illustrated in  FIG. 2 , a gripper  22  is located at the distal end portion  20  of the pusher  16 . The gripper  22  includes an outwardly expandable gripping element  24 , which is generally illustrated as a plurality of jaws  25 . Typically, the gripping element  24  and the jaws  25  will be not occupy the full circumference of the distal end portion  20  and the jaws  25  may, for example, take the form of two fingers protruding distally. The gripping element  24  releasably engages a protruding portion or headpiece  26  of a vascular occlusion device  28 , such as an embolic coil. As will be discussed in more detail below, when the gripping element  24  expands outwardly or opens, it releases the headpiece  26  of the vascular occlusion device  28 . 
         [0019]    The gripper  22  may be comprised of polymer, such as FEP Teflon, PTFE Teflon, polyvinyl chloride, a polyolefin or a neoprene, or any other suitable polymer, and may be constructed as disclosed in Bennett et al. U.S. Pat. No. 5,609,608, hereby incorporated herein by reference. Alternatively, the gripper  22  may be constructed of any suitable metal, or the gripper could comprise a microtube which has been slit. A suitable microtube may be made of stainless steel or of a nickel-titanium alloy such as Nitinol, or other suitable material. Further, in the illustrated embodiment, the gripper  22  and pusher  16  are shown as a unitary structure. However, it will be understood that the gripper  22  could be a separate unit which is attached to the pusher  16  in any suitable manner, for example by a silicone or cyanoacrylate adhesive. 
         [0020]    As stated above, the occlusion device  28  may be an embolic coil which may take various forms and configurations, and may also be filled with a fibrous material or may be coated with a beneficial substance, such as a biogel to promote clotting. Alternatively, the occlusion device also may be any other occlusion device or approach known in the art such as hydrogels, foams, bioactive coils, braids, cables, and hybrid devices. 
         [0021]    A collapsible or contractible reaction chamber  30  is positioned in the distal end portion  20  of the pusher  16 , preferably within the gripper  22 . The reaction chamber  30  comprises a cavity  31  that houses a first reactant  33  which is preferably a gas or a liquid. The cavity  31  is defined by a proximal wall  32 , a distal wall  34  and inner surface  36  of a sidewall  37  of the cavity  31 . The sidewall  37  is constructed such that it will deform inwardly or collapse in response to forces acting on it that are generated as described herein. In the embodiment where the jaws  25  are relatively narrow, the sidewall  37  can have an area of weakness in general alignment therewith to facilitate movement of the jaws during operation as described herein. The first reactant  33  occupies the defined volume of the cavity  31 . This can be considered to create a pressure within the chamber  30  that is equal to or slightly higher than the external pressure outside of the chamber. 
         [0022]    The proximal wall  32  and distal wall  34  are preferably comprised of an elastic membrane which may be attached to the inner surface  36  of the gripper  22  by an adhesive, such as a cyanoacrylate adhesive, or by any other suitable manner. The elastic membranes may be constructed from materials that do not significantly degrade while in contact with the reactant materials or the product formed therefrom. Typically, these will be an elastic polymer, such as silicone, a polyamide, a nylon, or a polyolefin such as polyethylene. Furthermore, the respective membranes will have different Durometer hardness values. For reasons that will be discussed in more detail below, the proximal wall  32  preferably is made of a lower Durometer polymer which can be easily flexed or bent in response to changes of pressure within the reaction chamber  30 . On the other hand, the distal wall  34  preferably is made from a higher Durometer polymer that resists bending or flexing in response to changes of pressure within the chamber  30 . 
         [0023]    The delivery unit  14  also includes a dispensing unit  38  for dispensing a second reactant  40  into the cavity  31  of the reaction chamber  30 . The illustrated dispensing unit  38  comprises a plunger-activated dispensing tube  42  which extends within the pusher  16  from the proximal end portion  18  to the distal end portion  20  of the pusher  16 . A distal end portion  43  of the dispensing tube  42  extends through the proximal wall  32  of the reaction chamber  30  into the cavity  31 . The proximal wall  32  and dispensing tube  42  may be attached and sealed together by an adhesive, such as a silicone or cyanoacrylate adhesive. 
         [0024]    The second reactant  40  may be dispensed from the dispensing tube  42  into the cavity  31  by activating a plunger  44  (which can be seen in  FIG. 1 ) located at a proximal end portion of the dispensing tube  42 . The plunger  44  includes a plunger head  45  which forces the second reactant  40  into the cavity  31  of reaction chamber  30 . Typically, the second reactant  40 , prior to dispensing, is secured within the dispensing tube  42  by a breakable seal  46 . Such seals should be selected to be made of a material that does not significantly degrade while in contact with the reactant materials. 
         [0025]    As illustrated in  FIG. 3 , when the first and second reactants  33 ,  40  are mixed, they produce a product  48  which occupies a volume that is less than the volume occupied by the first reactant  33  prior to mixing. The reduction of the volume occupied by the material within the cavity  31  of the chamber  30  causes activation of the release action to deploy the occlusion device  28 . Activation in this regard effects a reduction in the spacing between opposing inner surfaces  36 . Such reduction in spacing can be caused by a decrease of the pressure within the cavity when the reduced volume product  48  creates a void that is filled by inward movement of the sidewall. Alternatively, or additionally, the product  48  can have adhesive-like properties to assist in such sidewall inward movement. 
         [0026]    Preferably, the plunger head  45  has a sufficiently tight seal with the dispensing tube  42  to ensure that the cavity  31  is completely sealed and to maintain the pressure within the cavity after the reactants react. In the situation where a pressure difference assists in activation of the release action in response to the product reduced volume, the external pressure outside of the chamber  30  acts on the proximal wall  32  and the portion  37  of the gripper  22  defining the cavity to cause the lower Durometer proximal wall  32  and said portion  37  of the gripper to collapse inward, as illustrated in  FIGS. 3 and 4 . The higher Durometer distal wall  34  of the reaction chamber  30  is sufficiently rigid to resist the external pressure and substantially retains its original size and shape. The distal wall  34  can provide a fulcrum or pivot point  50  that assists in opening or expanding the gripping element  24  in an outward direction. In other words, the portion  37  of the gripper  22  which is proximal the distal wall  34  collapses inwardly. The collapsing of the portion  37  causes the gripping element  24 , which is located distal the distal wall  34 , to expand outwardly or open about fulcrum  50 . 
         [0027]    The first and second reactants  33 ,  40  can be any reactants that produce a product  48  that occupies a volume less than the first reactant  33 . Preferably, the first and second reactants  33 ,  40  are substances in the gaseous phase which react to form a gas, solid or liquid product  48  that occupies a volume which is less than the volume occupied by the first reactant  33 . Alternatively, the first reactant  33  can be a substance in the gaseous phase that reacts with the second reactant  40  (a substance in the gas, solid or liquid phase) to produce a liquid or solid product  48  that has a volume less than the first reactant  33 . It is also contemplated that the first reactant  33  could be a substance in the liquid phase that reacts with the second reactant  40  (a substance in the gas, solid or liquid phase) to produce a solid product  48  that has a volume less than the first reactant. 
         [0028]    In operation, the catheter  12  is inserted into the vasculature system of a patient and positioned at a preselected location within a blood vessel  13 , typically in conjunction with other devices and professional procedures as generally known in the art. The delivery unit  14  is inserted into and advanced through the catheter  12 . Once the desired location is reached, the delivery unit  14  is advanced, and/or the catheter  12  is moved in a retrograde manner, such that the delivery unit moves with respect to and within the catheter until the occlusion device  28  moves out of the distal end of the catheter. During the procedure and before the occlusion device  28  has been deployed, if it is determined that the distal end of the catheter  12  or the occlusion device  28  is not in the correct location, the occlusion device may be retrieved back into the distal end of the catheter by retracting the delivery unit  14  proximally or advancing the catheter distally. Once the occlusion device has been retrieved, the catheter and/or the occlusion device may be repositioned. 
         [0029]    When the occlusion device  28  is in the correct position, the plunger  44  may be activated to break the seal  46  and to dispense the second reactant  40  into the cavity  31  of the reaction chamber  30  so that the first and second reactants  33 ,  40  mix within the cavity  31 . Referring to  FIG. 3 , the first and second reactants  33 ,  40  react to form a product  48  which has a volume less than the volume of the first reactant  33  prior to mixing. As described above, the reduction of the volume of the material within the cavity  31  of chamber  30  typically causes the pressure within the cavity to decrease which in turn causes the proximal wall  32  and/or the sidewall  37  of the gripper defining the cavity to collapse. This collapsing action causes the gripping element  24  to pivot about fulcrum  50  and expand outwardly or open, thereby deploying the occlusive device. 
         [0030]    Referring to  FIG. 4 , after the occlusive device has been deployed, the delivery unit  14  can be retracted back into the delivery catheter  12 . If desired, the delivery unit  14  can be completely retracted from the catheter  12  and a new delivery unit having similar features can be advanced through the delivery catheter to deploy additional occlusion devices. 
         [0031]    It will be understood that the embodiments of the present invention which have been described are illustrative of some of the applications of the principles of the present invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention, including those combinations of features that are individually disclosed or claimed herein.