Patent Publication Number: US-2012035707-A1

Title: Methods of using implantable medical device detachment system

Description:
This is a divisional of U.S. patent application Ser. No. 11/461,245, filed Jul. 31, 2006, hereby incorporated by reference hereinto. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to interventional medical device systems that are navigable through body vessels of a human subject. More particularly, this invention relates to detachment systems for deploying an implantable medical device to a target location of a body vessel and methods of using the same. 
     DESCRIPTION OF RELATED ART 
     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 ensuring the complete release and deployment of the coil. For example, U.S. Pat. No. 5,250,071 to Palermo, which is hereby incorporated herein by reference, describes a detachment system whereby interlocking clasps of the system and the coil are held together by a control wire. The control wire is moved proximally to disengage the clasps from each other. However, the system does not include any positive means for separating the disengaged clasps from each other, so merely retracting the control wire does not ensure release and deployment of the coil. Numerous other detachment systems currently in use suffer from similar problems. 
     Therefore, a need remains for a rapid release detachment system or method that can ensure release and deployment of an implantable medical device. 
     Further advantages could be realized with a detachment system or method incorporating a simple and inexpensive locking and deployment system. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment or aspect of the present invention, a detachment system for delivering an implantable medical device to a target location of a body vessel is provided with a generally hollow tubular carrier member having a distal end and an engagement member associated with the distal end. The distal end includes a compressible portion that is axially adjustable between a compressed condition and an elongated condition. The engagement member is adapted to engage an implantable medical device when the compressible portion is in the compressed condition. 
     According to another embodiment or aspect of the present invention, a detachment system for delivering an implantable medical device to a target location of a body vessel is provided with a generally hollow tubular carrier member having a distal end and an engagement member associated with the distal end. The distal end includes a compressible portion that is axially movable from a compressed condition to an elongated condition. The engagement member is adapted to engage an implantable medical device when the compressible portion is in the compressed condition. Movement of the compressible portion to the elongated condition causes an implantable device engaged by the engagement member to be actively separated from the engagement member and deployed to the target location of the body vessel. 
     According to yet another embodiment or aspect of the present invention, a method of connecting an implantable medical device to a detachment system includes providing a generally hollow tubular carrier member. The carrier member has a distal end with a compressible portion that is axially movable from an elongated condition to a compressed condition. The compressible portion is moved to the compressed condition to expose at least a portion of an engagement member associated with the distal end. The exposed portion of the engagement member is then connected to an implantable medical device. 
     According to another embodiment or aspect of the present invention, a method of deploying an implantable medical device to a detachment system includes providing a generally hollow tubular carrier member. The carrier member has a distal end with a compressible portion in a compressed condition. An engagement member associated with the distal end is releasably connected to an implantable medical device. The thusly provided system is introduced into a body vessel and the implantable medical device is positioned generally adjacent to a target location of the vessel. When the implantable medical device is properly positioned, it is disengaged from the engagement member, which causes the compressible portion of the carrier member to axially elongate and actively deploy the implantable medical device. 
     Special application for the present invention has been found for deploying embolic coils to aneurysms in the neurovascular system. However, the present invention is also applicable to the deployment of other devices, including stents, to other portions of the vascular system, so it will be understood that the products and methods described herein are not limited to particular medical devices or particular surgical applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevational view of a carrier member of a detachment system according to an aspect of the present invention, in an elongated condition; 
         FIG. 1A  is a bottom plan detail view of an anchor portion of the carrier member of  FIG. 1 ; 
         FIG. 2  is a front perspective detail view of a distal end of the carrier member of  FIG. 1 ; 
         FIG. 3  is a front elevational view of the carrier member of  FIG. 1 , in a compressed condition; 
         FIG. 4  is a front perspective detail view of a distal end of the carrier member of  FIG. 3 ; 
         FIG. 5  is a front perspective view of a carrier member having a pusher portion according to an alternative embodiment; 
         FIG. 6  is a plan view of an engagement member according to an alternative embodiment; 
         FIG. 7  is a front perspective detail view of the opening of the engagement member of  FIG. 6 , in an up-turned condition; 
         FIG. 8  is a front perspective view of the distal end of the carrier member of  FIG. 1  and a rear perspective view of an implantable medical device in a pre-connection condition; 
         FIG. 9  is a front elevational view of a connection step for connecting the distal end and implantable medical device of  FIG. 8 ; 
         FIG. 9   a  is a front elevational view of the proximal end of the pusher portion of  FIG. 5  and illustrating a connection step by which the distal end of the pusher engages the proximal portion of the implantable medical device; 
         FIG. 10  is a front perspective detail view of the distal end of the carrier member and a rear perspective view of the implantable medical device of  FIG. 8 , in a connected condition; 
         FIG. 11  is a plan view of the distal end of the carrier member and proximal end of the implantable medical device of  FIG. 8 , in a disengaged condition; and 
         FIG. 12  is a front perspective view of a head piece for an implantable medical device. 
     
    
    
     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. 
       FIGS. 1-4  illustrate a distal portion of a generally hollow or tubular structure according to the present invention. When used herein, the terms “tubular” and “tube” are to be construed broadly and are not limited to a structure that is a right cylinder or strictly circumferential in cross-section or of a uniform cross-section throughout its length. For example, the tubular structure or system is generally designated at  10  and shown as a substantially right cylindrical structure. However, the tubular system may have a tapered or curved outer surface without departing from the scope of the present invention. 
     The detachment system  10  is comprised of a generally hollow tubular carrier member  12  having a distal end portion  14  with a compressible portion  16  and a pusher portion  18 . Preferably, the carrier member  12  is a hypotube that may be comprised of a biocompatible material, such as stainless steel. The hypotube typically will have a diameter of between about 0.010 inch and about 0.015 inch, a preferred tube having a diameter of approximately 0.013 inch. Such a carrier member  12  is suitable for delivering and deploying embolic coils to target locations, typically aneurysms, within the neurovasculature, but differently sized carrier members comprised of other materials may be useful for different applications and are within the scope of the present invention. 
     The compressible portion  16  of the distal end portion  14  is axially adjustable between an elongated condition ( FIGS. 1 and 2 ) and a compressed condition ( FIGS. 3 and 4 ). Preferably, the compressible portion  16  comprises a spiral-cut portion of the carrier member  12 , formed by a laser-cutting operation. However, any other arrangement allowing axial adjustment (e.g., a wound wire or spiral ribbon) is also suitable for use with detachment systems according to the present invention. Most preferably, the compressible portion  16  is in the elongated condition at rest and automatically or resiliently returns to the elongated condition from the compressed condition, unless otherwise constrained. The function of the compressible portion  16  will be described in greater detail herein. 
     When the compressible portion  16  is in the elongated condition, the distal end  14  receives and shields at least a portion of an engagement member  20 , as shown in  FIG. 2 . The engagement member  20  is relatively small, having the thickness of a hair in some embodiments, so it may be preferred for it to be entirely shielded by the distal end  14  to prevent damage from accidental contact. In the embodiment of  FIGS. 1-4 , the engagement member  20  comprises an elongated wire loosely bent in half to define an opening  22 . The ends  23  of the engagement member  20  are fixedly connected to the carrier member  12  at a position proximal to the compressible portion  16 , for example at an anchor portion  26  ( FIG. 1A ). 
     In an alternative embodiment, illustrated in  FIGS. 6 and 7 , the engagement member  20   a  comprises a flat ribbon defining an opening  22   a  at a distal portion thereof.  FIG. 7  shows the opening  22   a  in an up-turned condition suitable for engaging an implantable medical device  24 , as shown in  FIGS. 9  and  10  and described in greater detail herein. The engagement member  20  of  FIGS. 1-4  is preferably similarly deformable to the up-turned condition of  FIGS. 9 and 10 . Most preferably, the engagement member  20 ,  20   a  is elastically deformable to the up-turned condition of  FIGS. 7 ,  9 , and  10 , such that it will return to the substantially flat condition of  FIGS. 1-4  and  6  when not otherwise constrained. The engagement member  20 ,  20   a  may be comprised of any of a number of materials, including nitinol and stainless steel. The function of the engagement member  20 ,  20   a  will be described in greater detail herein. 
     As shown in  FIGS. 1-4 , the detachment system  10  further includes a locking member  26  received within the lumen of the carrier member  12  and movable with respect to the engagement member  20 . The locking member  28  is preferably substantially longer than the engagement member  20 , stretching beyond the anchor portion  26  to at least a proximal end portion (not illustrated) of the carrier member  12 . In some embodiments, the locking member  28  stretches beyond a proximal end of the carrier member  12  to be directly manipulated by the user. The locking member  28  may be a wire comprised of any of a number of materials, including nitinol. The function of the locking member  28  will be described in greater detail herein. 
     The pusher portion  18  is positioned adjacent to and distally of the compressible portion  16 . As shown in  FIGS. 1-4 , the pusher portion  18  preferably is not a simple right cylindrical member, but is a modified cylinder having a slot-like component, being defined by two arcuate extensions  30  and  32 . 
     In one embodiment, the two extensions  30 ,  32  of the pusher portion  18  accommodate therebetween an aperture-defining proximal end portion  34  of an implantable medical device  24 , which may be wider than the lumen of the carrier member  12 , as shown in  FIG. 11 . Thus, the spacing that separates the two arcuate extensions  30  and  32  accommodates the proximal end member  34  and allows the engagement member  20  to engage the implantable medical device  24  ( FIGS. 9 and 10 ), as described in greater detail herein. Furthermore, the engaged implantable medical device  24  may be rotated by rotating the carrier member  12  until at least one of the arcuate extensions  30 ,  32  bears against and turns the aperture-containing proximal end member  34  of the implantable medical device  24 . 
     The arcuate extensions  30  and  32  of  FIGS. 1-4  and  8 - 11  are illustrated with different lengths. As shown in  FIG. 9 , this creates a gap between the first arcuate extension  30  and a proximal end portion  36  of the implantable medical device  24 , which may simplify connection of the device  24 , as will be described in greater detail herein. However, according to an alternative embodiment of  FIG. 5 , the arcuate extensions  30  and  32  may have the same length without departing from the scope of the present invention. The function of the pusher portion  18  will be described in greater detail herein. 
     As for the implantable medical device  24 , an embolic coil having a proximal end portion  36  with an aperture  34  is illustrated in  FIGS. 8-11 . However, it will be appreciated that virtually any implantable medical device may be delivered and deployed by detachment systems according to the present invention. 
     To connect the implantable medical device  24 , the compressible portion  16  of the carrier member  12  is shortened in axial length to a compressed condition ( FIGS. 3 and 4 ) to expose at least a portion of the engagement member  20 . In particular,  FIG. 3  shows a distance “D” by which the carrier member  12  is axially foreshortened in moving the compressible portion  16  from the elongated condition to the compressed condition. If the locking member  28  of the carrier member  12  is oriented to extend beyond the engagement member  20 , as shown in  FIGS. 3 and 4 , it is withdrawn into the carrier member  12  sufficiently to position it clear of at least a portion of the opening  22  of the engagement member  20  ( FIG. 9 ). 
     With the engagement member  20  exposed and clear of the locking member  28 , the aperture-containing proximal end member  34  of the implantable medical device  24  is placed adjacent to opening  22 , which is then deformed to the up-turned condition of  FIG. 9 . Alternatively, the opening  22  may be moved to the up-turned condition prior to placement of the implantable medical device  24 . In the up-turned condition, at least a portion of the opening  22  passes through the aperture-containing portion  34 , as best shown in  FIG. 10 . If the device is not provided with a suitable aperture, then a head piece  38  may be affixed to a proximal end portion thereof ( FIG. 12 ) to provide an aperture  34   a  to receive the engagement member  20 . 
     If the first arcuate extension  30  of the pusher portion  18  is relatively short compared to the second arcuate extension  32 , then the second extension  32  will bear against the implantable medical device  24 , while a gap is defined between the device  24  and the first arcuate extension  30 , as illustrated in  FIG. 9 . The gap allows improved access to the engagement member  20 , thereby simplifying movement thereof through the aperture  34  of the implantable medical device  24 . 
     As described herein, the engagement member  20  is preferably elastically deformable to the up-turned condition of  FIG. 9 , so it will tend to return to a substantially flat condition. In order to prevent this, and to consequently lock the implantable medical device  24  to the engagement member  20 , the locking member  28  is moved axially through the opening  22  to the position of  FIG. 10 . In this connected condition, the locking member  28  holds the engagement member  20  in the up-turned condition, and the engagement member  20  holds the proximal end portion  36  of the implantable medical device  24  against at least one arcuate extent  30 ,  32  of the pusher portion  18 , preventing the compressible portion  16  from moving to the elongated condition. 
     Although an engagement system according to the preceding description is preferred for use with a detachment system of the present invention, other engagement systems may be used without departing from the present invention. For example, it is known to use heat-release adhesive to detach an implantable medical device from a delivery system. 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. Such an engagement system may be incorporated into the present invention by orienting the engaged embolic coil to bear against the pusher portion  18  and hold the compressible portion  16  in the compressed condition while the adhesive is intact. Of course, the adhesive should be sufficiently strong to prevent release by the force of the compressible portion  16  acting on the embolic coil through the pusher portion  18 . 
     Regardless of the engagement means employed to secure the implantable medical device  24 , a device thus engaged is preferably delivered to a target location within a body vessel by a separate catheter or introducer. According to one method of delivering the device  24 , a tubular catheter is fed into a body vessel until a distal end thereof is adjacent to a target location. Thereafter, the detachment system  10  and associated implantable medical device  24  are advanced through the catheter until the device  24  is itself generally adjacent to the target location. Alternatively, the detachment system  10  and associated device  24  may be pre-loaded in the catheter, with the combination being fed through a body vessel to a target location. Other methods of positioning the implantable medical device  24  generally adjacent to a target location may also be practiced without departing from the scope of the present invention. 
     To more accurately position the engaged device  24 , radiopaque markers (not illustrated) may be attached to the carrier member  12  or the device  24  itself. 
     When the engaged device  24  has been properly positioned and oriented, it is disengaged from the engagement member  20 . In the illustrated embodiment, this is achieved by moving the locking member  28  proximally from the position of  FIG. 10  to the position of  FIG. 9 . In the position of  FIG. 9 , the engagement member  20  is allowed to return to its original substantially flat condition ( FIGS. 3 and 4 ), thereby disengaging the aperture-containing end portion  34  of the implantable medical device  24 . The locking member  28  may be provided with a radiopaque portion to provide visual feedback to indicate when the device  24  has been released. 
     One suitable method of withdrawing the locking member  28  is described in greater detail in an application entitled “Interventional Medical Device System Having an Elongation Retarding Portion and Method of Using the Same” (Attorney Docket No. 0805-0356), filed herewith on Jul. 31, 2006, which is hereby incorporated herein by reference. Briefly, the carrier member  28  may include a proximal portion with an elongatable portion defined by a series of alternating cut sections and frangible bridge members arranged in a spiral or helical pattern. A proximal end of the locking member  28  (not illustrated) is fixedly attached to the carrier member  12  at a location proximal to the elongatable portion. The elongatable portion is elongated by a user, thereby retracting the locking member  28 . In one embodiment, the locking member  28  is adapted such that it will not disengage the engagement member  20  until a sufficient pull force is applied to break the frangible bridge members and more fully elongate the elongatable portion. Such an embodiment functions as a safety mechanism, because the implantable medical device  24  cannot be released until a minimum pull force is applied by the user. 
     When the implantable medical device  24  is disengaged from the engagement member  20 , the compressible portion  16  automatically or resiliently moves from the compressed condition of  FIG. 9  to the elongated condition of  FIG. 11 . At least one of the arcuate extensions  30 ,  32  of the pusher portion  18  bears against the device  24 , completely separating it from the engagement member  20 . Preferably, the pusher portion  18  bears against the proximal end portion  36  of the device  24  without contacting the aperture-containing proximal end portion  34 , as illustrated in  FIG. 10 , because the proximal end portion  36  is typically sturdier than the aperture  34 . 
     In the embodiment of  FIG. 5  and  FIG. 9   a , the pusher portion  18   a  is designed to bear against one or more of the coils of the illustrated embolic device  24  when separating the aperture-containing end portion  34  of the device  24  from the engagement member  22 . First arcuate extension  30  has a distal end surface that engages an upper edge (as viewed in  FIG. 9   a ) of the distal-most turn of the device  24  (or a distal-most surface of a portion of some other device to be implanted). This engagement securely holds the device and protects the rest of the device, especially the extending portion  34 , during disengagement. It also is contemplated that the second arcuate extension  32  has a distal end surface that engages a lower edge (as viewed in  FIG. 9   a ) of the distal-most turn at this portion of the device  24  (or distal-most surface of some other device). This engagement securely holds this portion of the device during disengagement. By combining engagement between the device at locations that flank the aperture-containing proximal end portion  34  by the arcuate extensions  30 ,  32  respectively, an especially protective engagement is effected during pushing and disengaging action. 
     Ultimately, the force of the compressible portion  16  automatically or resiliently moving from the compressed condition to the elongated condition will force the implantable medical device  24  some distance from the engagement member  20 , as shown in  FIG. 11 . The distance is exaggerated in  FIG. 11  for illustrative purposes, as the compressible portion  16  is preferably calibrated such that its elongation will move the device  24  away from the engagement member  20  without expelling the same a significant distance from the pusher portion  18 . 
     It will be seen from the preceding description that detachment systems according to the present invention eliminate numerous problems associated with known devices. In particular, detachment systems and associated methods of use according to the present invention ensure that the implantable device is completely separated from the engagement system and deployed to the target location. 
     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.