Abstract:
In one embodiment, the present invention relates to a mechanically releasable delivery system. More specifically, this embodiment includes an implantable device secured by tether at a distal end of the delivery system. The tether is fixed to the implantable device and looped around a selectively slidable mandrel. When the mandrel is retracted to expose its distal end, the looped tether slides off the mandrel, freeing the implantable device. Alternately, the tether can be fixed to the delivery system, wrapped around a portion of the implantable device and looped on to the slidable mandrel. Preferably, movement of the mandrel is controlled by an actuation control on the handle of the delivery system, allowing the user to selectively release the implantable device during a medical procedure.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/169,632 filed Apr. 15, 2009 entitled Implant Delivery System which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to an improved delivery system for delivering an implantable medical device. More specifically, this invention relates to an implant delivery system with an improved implantable device release mechanism. 
       BACKGROUND OF THE INVENTION 
       [0003]    Implantable medical devices and their accompanying delivery systems are well known in the art. These implantable devices include stents, microcoils, valves and similar types of devices which are used to treat a variety of different medical conditions. 
         [0004]    Many implantable devices are delivered within a patient by way of a catheter-style delivery device. One type of delivery system commonly used with self-expanding implantable devices utilizes two concentrically arranged catheters or shafts. The implantable device is disposed axially around a distal end of the inner catheter or pusher and held in a compressed position by the outer sleeve. Once the implantable device is positioned at a target location, the outer shaft is withdrawn, releasing the implantable device at the target location. 
         [0005]    One drawback often associated with this type of delivery system is the inability of the user to reposition the implantable device once released. In this respect, if the implantable device deploys in an undesirable position or configuration, the user is unable to recapture or otherwise reposition the device to a desired location. Curves in the path of the catheter through the human body can cause friction and further difficulties when evenly withdrawing the outer shaft and therefore can further result in undesirable device deployment. 
         [0006]    Other deployment systems also typically include a mechanism for selectively uncoupling the implantable device from the delivery system. For example, some delivery systems for non-expandable implants include a tether fixed to both the delivery catheter and the implantable device. When the user wishes to release the implantable device, a nearby heater melts the tether, thereby releasing the device. 
         [0007]    In such a delivery system, a portion of the melted tether remains on the implantable device. In some procedures, this tether remnant may cause complications in the patient such as blood clots, especially if located within a blood vessel. In other procedures, this tether remnant may pose less risk for complications and therefore may be of less concern to a physician. 
         [0008]    There remains a need in the art for an implantable device delivery system that overcomes the drawbacks of the prior art. 
       SUMMARY OF THE INVENTION 
       [0009]    One preferred embodiment according to the present invention relates to a mechanically releasable delivery system. More specifically, this embodiment includes an implantable device secured by tether at a distal end of the delivery system. The tether is fixed (e.g., a knot, adhesive, welding, etc.) to the implantable device and looped around a selectively slidable mandrel. When the mandrel is retracted to expose its distal end, the looped tether slides off the mandrel, freeing the implantable device. Alternately, the tether can be fixed to the delivery system, wrapped around a portion of the implantable device and looped on to the slidable mandrel. Preferably, movement of the mandrel is controlled by grasping the mandrel at a proximal end of the mandrel and sliding the mandrel in a proximal direction, thereby causing the implantable device to be released within the patient. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which: 
           [0011]      FIG. 1  illustrates a side view of a preferred embodiment of a delivery system according to the present invention; 
           [0012]      FIG. 2  illustrates an exploded view of a preferred embodiment of a release mechanism according to the present invention; 
           [0013]      FIG. 3  illustrates an assembled perspective view of the release mechanism of  FIG. 2 ; 
           [0014]      FIG. 4  illustrates an enlarged view of area  4 - 4  showing the release mechanism of  FIG. 3 ; 
           [0015]      FIG. 5  illustrates an exploded view of another preferred embodiment of a release mechanism according to the present invention; 
           [0016]      FIG. 6  illustrates an assembled perspective view of the release mechanism of  FIG. 5 ; 
           [0017]      FIG. 7  illustrates an enlarged view of area  7 - 7  showing the release mechanism of  FIG. 6 ; 
           [0018]      FIG. 8  illustrates a perspective view of another preferred embodiment of a release mechanism according to the present invention; and 
           [0019]      FIG. 9  illustrates a perspective view of the release mechanism of  FIG. 8  in a released or deployed configuration. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0020]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0021]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0022]      FIG. 1  illustrates a preferred embodiment of a delivery system  100  according to the present invention. Preferably, the delivery system  100  includes an elongated body  102 , such as a pusher body for advancing within a patient (e.g., within a pre-positioned catheter or with a retractable outer sheath). 
         [0023]    The distal end of the delivery system  100  includes an implantable device  104  (e.g., stent, valve, microcoil, etc.). A proximal end of the delivery device  100  may include a grip or handle  106  for grasping the device  100  and advancing it into the patient. Preferably, an outer sheath is used to introduce a microcatheter to a desired target location. The delivery system is introduced into the microcatheter and advanced to the target location. 
         [0024]    The proximal end of the delivery device  100  further includes an implantable device release control  108  which allows the user to cause the implantable device  104  to be released from the delivery system and left within the patient. More specifically, and as discussed in greater detail below, the release control  108  allows the user to retract (i.e., move proximally) a detachment mandrel  118  (i.e., an implant capture member, actuating member, or an elongated locking member). As a distal end of the detachment mandrel  118  retracts, it releases a tether  116  that secures the implantable device  104  to the delivery system  100 . 
         [0025]    Preferably, the release control  108  is formed by the proximal end of the detachment mechanism which slides relative to the body  102  or the handle  106 . A hypotube can be further included near or in the handle  106 , through which the detachment mandrel  118  slides. 
         [0026]    While the proximal end of the detachment mandrel  118  may simply be exposed to allow the user to move as desired, a wire can also be connected to the detachment mandrel  118 , allowing a user to pull the wire and therefore pull the detachment mandrel  118  proximally. Further, the detachment mandrel  118  can be spring biased to a closed position, for example, by disposing a spring at a proximal end of the detachment mandrel  118 , within the handle  106 . 
         [0027]    In other examples, this release control  108  may be a slider, lever, mechanical button, electrical button or any other type of actuation mechanism. The release mechanism  110  is preferably located within a passage of the body  102  near a distal end of the body  102 . 
         [0028]      FIG. 2  illustrates an exploded view of the release mechanism  110  according to a preferred embodiment of the present invention.  FIG. 3  illustrates an assembled view of the mechanism  110 , while  FIG. 4  illustrates a magnified view of area  4 - 4 . 
         [0029]    As explained in further detail below, the release mechanism  110  selectively releases an implantable device  104  by sliding a detachment mandrel  118  to release a tether  116  that is looped around the detachment mandrel  118 . More specifically, a free end (e.g., a distal free end) of the mandrel  118  is slid past an opening, free space or aperture located near a distal end of the delivery device  100 . The tether  116  is attached to the implantable device  104  (e.g., by adhesive, a knot, clip, etc.). Therefore, when the free end of the detachment mandrel  118  is retracted to a predetermined location (e.g., such that it is exposed or moved past the aperture), the loop of the tether  116  slides off the mandrel  118 , releasing the implantable device  104  from the delivery system  100 . 
         [0030]    Alternately, both ends of the tether  116  can be fixed to the delivery system  100  (e.g., the outer coil  112 ), positioned through a portion of the implantable device  104  (e.g., a loop or coil), then looped over the mandrel  118 . In this respect, the mandrel  118  acts as a sliding or lateral moving latch member. 
         [0031]    Preferably, the mandrel  118  is an elongated cylindrical member that extends to the proximal end of the delivery device  100 , or is attached to other mechanisms that extend to the distal end of the delivery device  100 , thereby allowing control of the mandrel  118  from a user at the proximal end. It should be understood that the mandrel may have a variety of cross sectional shapes, such as circular, square, rectangular and hexagonal. Additionally, this mandrel  118  preferably either extends to the proximal end or the delivery device  100  or mechanically connects to the proximal end to allow a user at the proximal end to manipulate the mandrel  118  and thereby cause the release of the implant. 
         [0032]    The release system  110  is at least partially contained within an outer coil  112 , which provides support and protection for the release mechanism  110 . Preferably, this outer coil  112  is located at the distal end of the body  102 ; however, it may also be fully or partially embedded in the body  102 , an outer sheath or outer layer. The outer coil  112  is preferably composed of a semi-rigid material (e.g., Nitinol, stainless steel, or radiopaque material) to maintain the overall shape of the device, yet flex as it is passed through a patient. 
         [0033]    The release system  110  further comprises a distal tube member  122  and a proximal tube member  124 , each of which are attached to a support mandrel  114  along their outer surface. Preferably, the tube members  122  and  124  are positioned in line with each other so as to leave a gap or open space large enough for the tether  116  to pass through, as seen best in  FIG. 3 . The tube members  122  and  124  are preferably sized to fit within the passage of the body  102  (i.e., within coil  112 ) and are further composed of a rigid or semi-rigid material such as Nitinol or stainless steel. The support mandrel  114  is also preferably composed of a rigid material such as Nitinol or stainless steel and is fixed to the tubes  122 ,  124  and outer coil  112 . 
         [0034]    The detachment mandrel  118  and the interior passages within the tubes  122  and  124  are sized such that the detachment mandrel  118  can freely move through these passages axially. Preferably, a distal end of the detachment mandrel  118  can further slide at least partially past the gap or open space, exposing the distal end (so that the tether  116  can slide off, releasing the implant  104 ). In this respect, the tubes  122  and  124  act as a housing for the detachment mandrel  118 . 
         [0035]    The delivery system  100  also includes an inner coil  120  that acts as a guide or passage for the detachment mandrel  118  as it slides back and forth to release the tether  116  and provides kink resistance. In this respect, the inner coil  120  is disposed around the detachment mandrel  118  and is further fixed to proximal tube  124 . The inner coil  120  also includes a different pitch than the outer coil  112  which helps prevent the inner coil  120  from wedging between the loops of the outer coil  112 . Preferably, the inner coil  120  is composed of a rigid material such as Nitinol or stainless steel and extends proximally past the outer coil  112  as seen best in  FIG. 3 . 
         [0036]    In operation, the user advances the distal end of the delivery system  100  to a target location within a patient. When the user is satisfied with the placement of the implantable device  104 , the implantable device release control  108  is actuated (e.g., the detachment mandrel  118  is pulled proximally), causing the distal end of the detachment mandrel  118  to move in a proximal direction. The distal end of the detachment mandrel  118  moves past the proximal end of distal tube  122 , creating a gap between the mandrel  118  and the tube  122 . Preferably, the tether  116  is under tensions and therefore immediately slides off the mandrel  118  as soon as the previously mentioned gap opens up. At this point, the implantable device  104  is free from the delivery system  100  and the delivery system  100  can be removed from the patient. 
         [0037]    It should be understood that additional delivery controls or options known in the art are possible with the delivery system  100 . For example, a sheath can be used over the body  102  to control the expansion of implantable device  104  (e.g., prevents a stent from expanding until the sheath is pulled away from the device  104 ). In another example, additional lumens containing additional tools or controls are possible. 
         [0038]      FIGS. 5-7  illustrate another preferred embodiment of a implantable device release mechanism  130  according to the present invention. Generally, the release mechanism  130  is similar to the previously described release mechanism  110 . However, the present release mechanism  130  includes a single tube  132  instead of the two previous tubes  122  and  124 . 
         [0039]    In the present preferred embodiment, the single tube  132  includes an aperture or cut-away portion  132 A. The tether  116  is looped over the detachment mandrel  118  and passes through the cut-away portion  132 A. In this respect, as the detachment mandrel  118  is moved proximally by the previously described device release control  108 , the looped portion of the tether  116  slides off the detachment mandrel  118  and out the cut-away portion  132 A, releasing the device  104 . 
         [0040]    Preferably, the aperture or cut-away portion  132 A can be formed by laser or mechanical cutting of a tube or adhering two tubes together. Also, the cut-away portion  132 A preferably includes an angled cut (i.e., an edge surface not at 90 degrees to the length of the tube  132 ) to prevent rubbing or friction against the tether  116  and thereby minimizing damage to the tether  116 . Preferably, at least the distal portion of the aperture  132 A has a non 90 degree cut angle (i.e., the portion on which the tether  116  rests). In one example, at least the distal portion of the aperture  132 A has a cut angle between about 10 and 80 degrees relative to an axis of the length of the tube  132 . 
         [0041]    As previously described with regard to release mechanisms  110  and  130 , the free ends of the tether  116  can be connected to the delivery device  100  (e.g., coil  112 ) for procedures when the tether  116  may pose a high risk of complications to a patient. Alternately, the tether  116  may remain with the implant  104  after implantation (i.e., both free ends of the tether are connected to the implant  104 ) for procedures when the tether  116  may pose a low risk of complications to a patient. The tether  116  either remains in the patient or degrades if composed of a biodegradable material. 
         [0042]      FIGS. 8 and 9  illustrate an alternative tether configuration as part of another preferred embodiment of a release mechanism  140  according to the present invention. As seen best in the unreleased position of  FIG. 8 , the free ends of the tether  116  are fixed (e.g., adhesive, tying, or similar methods of fixation) to the outer coil  112 . The tether  116  passes through apertures or around spokes or coils of the device  104 , then through cut-away portion  132 A and around the detachment mandrel  118 . 
         [0043]    As seen in  FIG. 9 , when the detachment mandrel  118  moves proximally, the loop portion of the tether  116  slides off the detachment mandrel  118 . The tether  116  slides through the device  104 , releasing the device  104 . In this respect, the tether  126  is removed from the patient with the delivery system  100 , preventing the tether  116  from otherwise causing complications in the patient (e.g., blood clots when used with stents). 
         [0044]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.