Patent Publication Number: US-2007123927-A1

Title: Embolic device delivery system

Description:
FIELD OF THE INVENTION  
      The present invention is related to the delivery of embolic occlusion devices. Disclosed are occlusion device deployment systems and methods for mechanically deploying occlusion devices at a preselected location within a patient, in an accurate and rapid manner. The deployment systems and methods are particularly suited for deploying an embolic coil at a location of concern within the vasculature of a patient.  
     BACKGROUND OF THE INVENTION  
      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 cranial blood vessels. Due to the delicate tissue surrounding cranial blood vessels, especially for example brain tissue, it is very difficult and often risky to perform surgical procedures to treat defects of the cranial blood vessels. 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.  
      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.  
      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 to also provide 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.  
      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 have the potential to interfere with other surgical and monitoring equipment.  
      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 transforms the light into heat energy. The heat energy raises the temperature of the connector and opens the fingers, thereby releasing the embolic coil. This type of ball and socket connection is rigid and causes the catheter to be stiff, making it difficult to guide the catheter through the vasculature of the body. This patent, and all other patents and references identified herein are hereby incorporated herein by reference.  
      Further, the above-identified delivery systems typically require electronic equipment powered by a power source. If the electronic equipment is defective or the power source fails, the procedure may be prolonged while the equipment is repaired or replaced. Prolonging the procedure may expose the patient to additional risk.  
      Therefore, a need remains for a rapid release vascular occlusion deployment system or method that can function without electrical equipment or a power supply, does not develop chemical debris, is simple to manufacture, flexible and easy to guide through the vasculature of the body, provides excellent control over the occlusion device, and reduces the possibility of interference with other surgical and/or monitoring equipment.  
     SUMMARY OF INVENTION  
      The present invention embodies deployment systems and methods for accurately and rapidly deploying a vascular occlusion device at a location of concern within the vasculature of a patient. The deployment system can employ an elongated flexible delivery catheter for guiding a deployment unit to a location of concern within a patient. The deployment unit includes a pusher for pushing and guiding the vascular occlusion device, such as an embolic coil, through the delivery catheter to the location of concern.  
      In one embodiment, the pusher has a proximal end portion and a distal end portion, and a channel extending between the proximal end portion and the distal end portion. The pusher also includes an elongated member which is slidably located within the channel. The elongate member and the pusher are also able to rotate with respect to one another, i.e., the elongated member is able to rotate within the channel of the pusher, and the pusher is able to rotate around the elongated member.  
      The distal end portion of the elongated member includes a connecting projection, plug or cam follower extending in a generally radial direction therefrom. An embolic device can be removeably secured to the elongated member by engaging the connecting projection or cam follower with a channel or cam pathway defined by a proximal end portion of the embolic device. The connecting projection or cam follower can be engaged with the channel or cam pathway by positioning the elongated member so that the connecting projection or cam follower is at the entrance of the channel or cam pathway. The elongated member is rotated in the direction of the pathway, such as the wind, of the channel so that the connecting projection or cam follower moves within the channel or cam pathway. In one preferred embodiment, the channel or cam pathway is helically configured so that as the connecting projection or cam follower is helically threaded into the channel or cam pathway, the elongated member advances distally with respect to the embolic device and/or the embolic device advances proximally with respect to the elongated member.  
      According to one preferred method, the embolic device is released from the pusher after the device is positioned endoluminally. Prior to release, the distal end portion of the pusher is contacted with the proximal end portion of the embolic device attached to the elongated member so that the embolic device will not rotate independently of the pusher. This imparts an engaged state at which the embolic device is maintained in a substantially stationary position by engagement between the pusher and the embolic device. While in this engaged state, the elongated member is rotated in a direction opposite to the direction in which the elongated member had been rotated in order to secure the embolic device to the elongated member. The connecting projection or cam follower again moves along the channel or cam pathway until release, such as by unthreading the connecting projection or cam follower. The embolic device is thereby released from the deployment system at a desired deployment location.  
      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 drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In describing the preferred embodiments of the present invention, reference will be made to the accompanying drawings, wherein:  
       FIG. 1  is an enlarged partially sectioned view of an occlusion device deployment system in accordance with a preferred embodiment of the present invention;  
       FIG. 2  is an exploded view of the deployment unit illustrated in  FIG. 1 ;  
       FIGS. 3 and 3   a  are enlarged perspective views of one embodiment of the embolic device headpiece;  
       FIGS. 4 and 4   a  are enlarged perspective views of one embodiment of the pusher headpiece;  
       FIG. 5  is an enlarged partially sectioned view of the deployment system of  FIG. 1  shown prior to deployment;  
       FIG. 6  is an enlarged partially sectioned view of the deployment system of  FIG. 1  shown after the embolic device has exited the delivery catheter and shown with the distal end portion of the pusher and the embolic device being separated;  
       FIG. 7  is an enlarged partially sectioned view of the deployment system of  FIG. 1  shown with the pusher engaging the embolic device after the embolic device has exited the delivery catheter; and  
       FIG. 8  is an enlarged partially sectioned view of the deployment system of  FIG. 1  shown after the embolic device has been released. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      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.  
       FIG. 1  generally illustrates a preferred embodiment of the occlusion device deployment system of the present invention. The deployment system, generally designated at  10 , includes an elongated flexible delivery catheter  12  which can be inserted into the vasculature of a patient and used to guide a deployment unit, generally designated at  14 , to a preselected site in a manner generally known in the art. One of ordinary skill in the art will appreciate that the delivery catheter  12  and the deployment unit  14  are much longer than illustrated in the figures.  
      Referring to  FIGS. 1 and 2 , the deployment unit  14  includes an elongated flexible pusher  16  which can be comprised of a delivery tube  17  and a pusher headpiece  19 . The delivery tube  17  has a proximal end portion  18  and a distal end portion  20 . An internal lumen (not shown) extends from the proximal end portion  18  of the delivery tube  17  through the pusher headpiece  19 . The delivery tube  17  can be any suitable type of delivery tube generally known in the art that has sufficient column strength to push an embolic device through a delivery catheter and sufficient flexibility to be guided through tortuous pathways within the vasculature of a patient. Additionally, the delivery tube preferably has the ability to resist torque applied to the delivery tube during release of the embolic device, as describe below. For example, the delivery tube can be comprised a coil wound wire, or the delivery tube can be a flexible polymer sheath.  
      An elongated member  24  is slidably disposed within the channel of the pusher  16 , i.e., the elongated member  24  is relatively moveable in a proximal and a distal direction with respect to the pusher  16 . Additionally, the elongated member  24  and the pusher  16  are able to rotate with respect to one another, i.e., the elongated member  24  is able to rotate within the channel of the pusher  16  and the pusher is able to rotate around the elongated member  24 .  
      The elongated member  24  is preferably comprised of a metallic or polymeric material which has tensile and flex properties that allow the elongated member to be easily guided through tortuous paths within the patient.  
      The elongated member  24  includes a proximal end portion  26  and a distal end portion  28 . The distal end portion  28  can be positioned to extend out of the pusher headpiece  19 . The elongated member  24  also includes a connecting projection, cam follower or plug  29  extending in a generally radial direction from the distal end portion  28  of the elongated member  24 . In the illustrated arrangement, the connecting projection, cam follower or plug  29  is perpendicular to the axis of the elongated member  24 . The connecting projection, cam follower or plug  29  can be used to removeably secure an embolic device  30  to the elongated member  24 , as described in more detail below.  
      The elongated member  24  and the connecting projection, cam follower or plug  29  can be of a unitary construction. For example the projection, cam follower or plug  29  can be formed as a distal bend of the elongated member  24  which may have a modified characteristic such as an end of a different size. Alternatively, the connecting projection, cam follower or plug  29  can be attached to the elongated member  24  by any suitable attachment method known in the art, such as welding, force fitting, soldering or adhering with adhesive.  
      The embolic device  30  is preferably an embolic device assembly that includes an embolic element  34  and a headpiece  36 . As illustrated in  FIGS. 2, 3  and  3   a , the embolic device headpiece  36  has a proximal end portion  38  and a distal end portion  40 . The distal end portion  40  includes a joining element  42 , which is illustratively shown as a cylindrical projection, for connecting the embolic element  34  to the headpiece  36 . The embolic element  34  and joining element  42  may be connected by weld, solder, adhesive or any other suitable attachment method known in the art. Illustratively, the embolic device  30  comprises the headpiece  36  and the embolic element  34  which are separate components that are secured together; however, it will be understood by one of ordinary skill in the art that the embolic element  34  and the headpiece  36  can be of a unitary construction to form embolic device  30 .  
      The embolic element  34  is preferably an embolic coil which can be of the type which takes a substantially linear configuration for being advanced through the delivery catheter and a randomly oriented relaxed condition after it is released from the catheter. Alternatively, the embolic element  34  may be any other type of embolic element which may take on various forms and configurations, such as hydrogels, foams, bioactive coils, braids, cables and hybrid devices.  
      In the illustrated embodiment, the headpiece  36  includes a circumferential wall  44  which defines a cavity  46 . The circumferential wall  44  also includes a channel or cam pathway  48  into which the connecting projection, cam follower or plug  29  of the elongated member  24  can be threaded to secure the embolic device  30  to the elongated member  24 . Illustratively, the channel or cam pathway  48  extends through the circumferential wall  44 . It is also contemplated that the channel or cam pathway  48  could be comprised of a groove located on the inner surface of circumferential wall, but does not extend through the circumferential wall. Additionally, the channel or cam pathway  48  is preferably configured in the illustrated helical configuration; however, it is contemplated that the channel or cam pathway  48  can be of a substantially circular configuration or other turn configuration.  
      Preferably, including when the channel or cam pathway  48  is of a helical configuration, the channel or cam pathway  48  includes an entrance  50  which can include a notch  52  that is sized to accommodate movement of the connecting projection, cam follower or plug  29  therealong. For example, the notch  52  can be slightly larger than the approximate dimensions of the connecting projection, cam follower or plug  29 . The notch  52  aids in advancing the connecting projection, cam follower or plug  29  into the channel or cam pathway  48  and withdrawing the connecting projection, cam follower or plug  29  from the channel or cam pathway  48  when the headpiece  36  is engaged with headpiece  19 . The channel or cam pathway  48  also includes an end wall  54  which is located distally of the entrance  50 .  
      To connect the embolic device  30  to the elongated member  24 , the connecting projection, cam follower or plug  29  is positioned within the notch  52  of the entrance  54  of the channel or cam pathway  48 . The elongated member  24  is then rotated to thread the connecting member, cam follower or plug  29  into the channel or cam pathway  48 . In the illustrated embodiment, the elongated member  24  is rotated in a clockwise direction to thread the connecting projection, cam follower or plug  29  into the channel or cam pathway  48  (if the helical configuration of the channel is wound in the opposite direction, the elongated member would be rotated counterclockwise to thread the connecting projection). When the connecting projection, cam follower or plug  29  is threaded in a helically shaped channel or cam pathway  48 , the elongated member  24  moves distally within the cavity  46  of the headpiece  36 . The elongated member is rotated until the connecting projection, cam follower or plug  29  contacts end wall  54  of the channel or cam pathway  48  and is thus set into a closed condition.  
      The proximal end portion  38  of the headpiece  36  includes an arrangement for positively engaging the pusher, typically a headpiece thereof. By such an engagement, the embolic device headpiece and the pusher headpiece will not rotate circumferentially in a manner independent of each other.  
      A preferred engagement arrangement in this regard includes an engagement member  56  of the headpiece  36  which mates with a corresponding engagement member  58  of a pusher headpiece  19 . As shown in  FIGS. 3, 3   a ,  4  and  4   a , the illustrated respective engagement members  56 ,  58  each embody a partial circumferential projection in the axial direction, and such projections contact one another and can be complementary with each other. When desired, the projections combine to form a circumference with engaging surfaces that contact one another. In a preferred embodiment, the projections combine to form a shape having an axial or central axis, such as a cylinder.  
      The engagement surfaces  62 ,  62   a  and  64 ,  64   a  can be along an axis aligned parallel to the central axis of the cylinder formed by the mated engagement members  56 ,  58 . The engaging surfaces also need not be parallel to the central axis but can be at an acute angle to the central axis of the cylinder. Also, each engagement surface can be along a common plane that is parallel to the central axis of the cylinder. Alternatively, the engagement surfaces of each headpiece can be along separate planes that do not intersect. For example, each engagement surface could be along a different plane wherein each plane is separated by a distance. This would also include engagement surfaces of the same headpiece that are beveled in the same direction at the same angle.  
      In yet another alternative, the engagement surfaces can be along separate planes that intersect. For example, in the illustrated embodiment the engagement surfaces  62 ,  62   a  of the headpiece  36  could be beveled inwardly toward each other, or the engagement surfaces could be beveled outwardly away from each other. The engagement surfaces typically can be planar, or flat, but can have a curved configuration or component. For example, the engagement surfaces could have a tongue and groove mating configuration wherein an engagement surface of one headpiece could have a tongue, and the corresponding engagement surface of the other headpiece could have a corresponding groove which mates with the tongue when the engagement members are engaged.  
      The engagement surfaces interact with each other to provide interference with independent circumferential movement of the headpieces while allowing independent movement of the embolic device  30  and the pusher  16  axially when it is desired to deploy the embolic device. The illustrated engagement member  56  of the embolic device headpiece  36  is a semi-circular projection  60  which includes engagement surfaces that are flats  62 ,  62   a  located on either side or edge of the projection  60 . The flats  62 ,  62   a  in this illustrated embodiment engage corresponding engagement surfaces, such as flats  64 ,  64   a , located on a semi-circular projection  66  of engagement member  58  of the pusher headpiece  19  shown in  FIGS. 4 and 4   a.    
      As will be explained in more detail below, the arrangement for positively engaging the respective headpieces  19  and  36  functions as follows according to the illustrated preferred embodiment. The pusher headpiece  19  and the embolic device headpiece  36  engage each other to either resist or counteract torque applied to the proximal end portion  26  of the elongated member  24 . Alternatively, the engagement of pusher headpiece  19  and embolic headpiece  36  can be used to rotate embolic device  30  by rotating pusher  16 .  
      As illustrated in  FIGS. 4 and 4   a , the illustrated pusher headpiece  19  also includes a proximal end portion  68 . The proximal end portion  68  includes a joining element  70 , which is illustratively shown as a tubular projection, for joining the headpiece  19  to the delivery tube  17 . The distal end portion  20  of the delivery tube  17  engages, such as by fitting over, the joining member  70 . The joining member  70  and the delivery tube  17  can be connected by weld, solder, adhesive or any other suitable method. The headpiece  19  also includes a passageway  72  which allows the elongated member  24  to extend therethrough and project from headpiece  19  of the pusher  16 .  
      To secure the embolic device in the vascular occlusion deployment system, the embolic device  30  is preferably attached to the elongated member  24  of the pusher  16  by contacting the engagement member  56  of the embolic device  30  with engagement member  58  of the pusher  16  so that the flats or engagement surfaces  62 ,  62   a  and  64 ,  64   a  respectively of the respective engagement members  56  and  58  mate with each other. The elongated member  24  is then advanced distally within the pusher  16 , and the connecting projection, cam follower or plug  29  is aligned with the notch  52  of the channel or cam pathway  48 . The elongated member  24  is rotated in a direction that moves the connecting projection, cam follower or plug  29  within the channel or cam pathway  48 . The elongated member  24  is rotated until the connecting projection, cam follower or plug  29  contacts the end wall  54  of the channel or cam pathway  48 .  
      An alternative method of connecting the embolic device  30  to the elongate member  24  would be to position the elongated member  24  so that it extends out of the headpiece  19  of the pusher  16 . The distal end portion  28  of the elongated member  24  is then positioned so that the connecting projection, cam follower or plug  29  is located at the notch  52  of the channel or cam pathway- 48 . The embolic device  30  is maintained in a substantially stationary position, such as by grasping by hand or by some other mechanism, and the elongated member  24  is rotated to move the connecting projection, cam follower or plug  29  into the channel or cam pathway  48 . In lieu of rotating the elongated member  24 , the elongated member  24  can be maintained in a stationary position, and the embolic device  30  can be rotated by hand or some other method to position the connecting projection, cam follower or plug  29  into the channel or cam pathway  48 .  
      After the embolic device  30  has been attached to the elongated member  24 , referring to  FIGS. 5-8 , the delivery catheter  12  can be inserted into the vasculature system of a patient, and the distal end portion  74  of the catheter  12  can be positioned at a preselected location within a blood vessel, typically in conjunction with other devices and professional procedures as generally known in the art. The delivery unit  14  is inserted into a proximal end portion  76  of the catheter  12 , and preferably the delivery unit  14  is advanced through the delivery catheter  12  until the embolic device  30  reaches the distal end portion  74  of the delivery catheter  12 . If desired, the pusher headpiece  19  and the embolic device headpiece  36  can be engaged to increase column strength during the advancement of the pusher  16 .  
      Once the embolic device  30  reaches the distal end portion  74  of the delivery catheter  12 , the embolic device  30  may be moved out of the distal end portion  74  of the delivery catheter  12  in one of several ways. The delivery catheter  12  may be moved in a retrograde manner as indicated by arrow A. Alternatively, the pusher  16  may be advanced as indicated by arrow B. As a further alternative, the embolic device  30  may be advanced out of the delivery catheter  12  by advancing the elongated member  24  in a distal direction. Yet another alternative can be to use any of the above methods in conjunction with one another.  
      The embolic device  30  preferably includes a radiopque marker so that the position of the embolic device  30  can be monitored by fluoroscopy. Referring to  FIG. 6 , after the embolic device  30  has exited the delivery catheter  12 , if required, the elongated member  24  can be manipulated to more precisely place the embolic device  30  at the desired location. If it is determined that the embolic device  30  is in the wrong position and/or a different embolic device is required, the pusher  16  and the elongated member  24  can be retracted to move the embolic device  30  back into the delivery catheter  12 . Once in the delivery catheter  12 , the embolic device  30  can be repositioned or completely removed from the patient.  
      After it has been determined that the embolic device  30  is at the desired location within the patient, and if not already in engagement, the headpieces are so engaged. Typically, the pusher headpiece  19  is engaged with the embolic device headpiece  36  so that the corresponding flats  62 ,  62   a  and  64 ,  64   a  engage each other, as illustrated in  FIG. 7 . Engagement of the headpieces  19  and  36  can be accomplished as needed by advancing the pusher  16  in a distal direction as indicated by arrow C. It is also contemplated that in certain situations, it may be advantageous to engage the headpieces  19  and  36  by moving the elongated member  24  in a proximal direction as indicated by arrow D.  
      After the headpieces  19  and  36  have been engaged according to this illustrated embodiment, the embolic device  30  can be released by rotating the elongated member  24  so that the connecting projection, cam follower or plug  29  disengages and clears the channel or cam pathway  48 . Preferably, the connecting projection, cam follower or plug  29  is unthreaded from the channel or cam pathway  48  by rotating the elongated member  24  circumferentially to provide torsional force to the elongated member, as illustrated by arrow E (or in the opposite circumferential direction if the channel or cam pathway is helically wound in the opposite direction). The torque applied to the elongated member  24  is resisted by the delivery tube  17  and headpiece  19 . Additionally, the engagement along the headpieces  36  and  19 , such as between the flats  62 ,  62   a  and  64 ,  64   a  respectively, limits or reduces rotational movement of the headpiece  36  of the embolic device  30  which causes the connecting projection, cam follower or plug  29  to unthread from channel or cam pathway  48  of the substantially stationary headpiece  36 . The headpieces  36  and  19  maintain contact during release of the embolic device  30 . The engagement between the headpieces  36  and  19  also limits or reduces any undesired rotational movement of the embolic device  30 . When the pusher  16  is comprised of a coiled wire, it is preferable that the channel or cam pathway  48  of the embolic headpiece  36  be configured so that the elongated member  24  is rotated in a direction opposite of the wind of the coil during unthreading to avoid buckling or kinking the pusher  16 .  
      It is also contemplated that there may be situations where it would be advantageous to disengage the connecting projection, cam follower or plug  29  from the channel or cam pathway  48  by rotating the embolic device  30  while maintaining the elongated member  24  in a substantially stationary position. By this approach, the pusher  16  is rotated and the rotational movement of the pusher  16  is translated therealong, through the headpieces, to the embolic device. At the same time, the elongated member is maintained in a substantially stationary position, resulting in the unthreading in the connecting projection, cam follower or plug  29  from the channel or cam pathway  48 .  
      As illustrated in  FIG. 8 , after the connecting projection, cam follower or plug  29  has been rotated and moved so as to clear the channel or cam pathway  48 , the embolic device  30  can be released for deployment at a desired location within the patient such as within or at an aneurysm. The pusher  16  can now be retracted through the delivery catheter  12  and removed from the patient.  
      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.