Abstract:
A medical device for placing an embolic device, such as an embolic coil, at a predetermined site within a vessel of the body including a delivery catheter and a flexible pusher member movably disposed within the catheter. An embolic device is detachably coupled to the pusher member and is retained in place on the distal end of the pusher member by a detachment filament. When the embolic device is advanced to the predetermined site within the vessel, the detachment filament is decoupled from the embolic device to thereby release the embolic device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This patent application claims priority from Provisional Patent Application Ser. No. 60/592,580, filed on Jul. 30, 2004. 
     
    
     BACKGROUND OF INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a medical device for placing an embolic device at a predetermined site within a vessel of the human body, and more particularly, relates to a catheter-based deployment system for delivering an embolic device. This device is particularly suited to transport an embolic device, such as an embolic coil, through the tortious vasculature of the human brain to a selected site.  
         [0004]     2. Description of the Prior Art  
         [0005]     For many years, flexible catheters have been used to place various devices within the vessels of the human body. Such devices include dilation balloons, radiopaque fluids, liquid medications, and various types of occlusion devices such as balloons and embolic coils. Examples of such catheter-based devices are disclosed in U.S. Pat. No. 5,108,407, entitled, “Method And Apparatus For Placement Of An Embolic Coil,” and U.S. Pat. No. 5,122,136, entitled, “Endovascular Electrolytically Detachable Guidewire Tip For The Electroformation Of Thrombus In Arteries, Veins, Aneurysms, Vascular Malformations And Arteriovenous Fistulas.” 0  These patents disclose catheter-based devices for delivering embolic coils to preselected positions within vessels of the human body in order to treat aneurysms, or alternatively, to occlude blood vessels at a particular location.  
         [0006]     Coils which are placed in vessels may take the form of helically wound coils, or alternatively, may take the form of randomly wound coils, coils wound within coils or other such coil configurations. Examples of various coil configurations are disclosed in U.S. Pat. No. 5,334,210, entitled “Vascular Occlusion Assembly;” and U.S. Pat. No. 5,382,259, entitled, “Vasoocclusion Coil with Attached Tubular Woven or Braided Fibrous Covering.” Embolic coils are generally formed of a radiopaque metallic material, such as platinum, gold, tungsten, or alloys of these metals. Often, several coils are placed at a given location to occlude the flow of blood through the vessel, or aneurysm, by promoting thrombus formation at the particular site.  
         [0007]     In the past, embolic coils have been placed within the distal end of a catheter. When the distal end of the catheter is properly positioned, the coil may then be pushed out of the end of the catheter with a pusher member to release the coil at the desired location. This procedure for placement of an embolic coil is conducted under fluoroscopic visualization such that the movement of the coil through the vasculature of the body may be monitored and the coil placed at the desired location.  
         [0008]     Another procedure involves the use of glue or solder for attaching the coil to a guidewire, which in turn, is placed within a flexible catheter for positioning the coil within the vessel at a preselected position. Once the coil is in the desired position, the coil is held in position by the catheter and the guidewire is pulled proximally to thereby cause the coil to become detached from the guidewire and released from the catheter. Such a coil positioning system is disclosed in U.S. Pat. No. 5,263,964 entitled, “Coaxial Traction Detachment Apparatus and Method.” 
         [0009]     Still another coil positioning procedure is that of having a catheter with a socket at the distal end of the catheter for retaining a ball which is, in turn, bonded to the proximal end of the coil. The ball, which is generally larger in diameter than the outside diameter of the coil, is placed in the socket within the lumen at the distal end of the catheter and the catheter is then moved into a vessel in order to place the coil at a desired position. Once the position is reached, a pusher wire with a piston at the end thereof is pushed distally from the proximal end of the catheter to push the ball out of the socket in order to release the coil at the desired position. Such a system is disclosed in U.S. Pat. No. 5,350,397, entitled, “Axially Detachable Embolic Coil Assembly.” 
         [0010]     Another procedure for placing an embolic coil within a vessel is that of using a heat releasable adhesive bond for retaining the coil at the distal end of the catheter. One such system uses laser energy transmitted through a fiber optic cable to apply heat to the adhesive bond in order to release the coil from the end of the catheter. Such a procedure is disclosed in the aforementioned U.S. Pat. No. 5,108,407.  
         [0011]     Yet another coil deployment system incorporates a catheter having a lumen throughout the length of the catheter and a distal tip for retaining the coil for positioning the coil at a preselected site. The distal tip of the catheter is formed of a material which exhibits the characteristic that when the lumen of the catheter is pressurized the distal tip expands radially to release the coil at the preselected site. Such a deployment system is disclosed in U.S. Pat. No. 6,113,622, entitled, “Embolic Coil Hydraulic Deployment System.” 
         [0012]     Still another coil deployment system incorporates an interlocking mechanism on the coil. The interlocking end on the embolic coil couples with a similar interlocking mechanism on a pusher assembly. A control wire which extends through the locking mechanism secures the coil to the pusher assembly. The pusher assembly and embolic coil are initially disposed within the lumen of a catheter. When the embolic coil is pushed out of the end of the catheter for placement, the control wire is retracted and the coil disengages from the pusher assembly. Such a deployment system is disclosed in U.S. Pat. No. 5,925,059, entitled, “Detachable Embolic Coil Assembly.” 
         [0013]     Yet another coil deployment system incorporates an embolic device detachably mounted on the distal portion of a pusher member and held in place with a connector thread or fiber. The fiber passes through a cutter member that may be activated to cut the connector fiber. Once the connector fiber is cut, the embolic device is released. Such a deployment system is disclosed in Published U.S. patent application No. 2002/0165569, entitled, “Intravascular Device Deployment Mechanism Incorporating Mechanical Detachment.” 
         [0014]     Still another coil deployment system incorporates an embolic device with a stretch resistant member therethrough. The distal end of the stretch resistant member attaches to the embolic coil and the proximal end of the stretch resistant member is detachably mounted on the pusher member through various means such as adhesive, or by a connector fiber adhered to or tied to the pusher member, and is detachable by the application of heat. Such a deployment system is disclosed in Published U.S. patent application No. 2004/0034363, entitled, “Stretch Resistant Therapeutic Device.” 
         [0015]     Still another coil deployment system incorporates a pusher wire with a stiff wavy-shaped end segment which is coupled to the embolic coil and is placed in the lumen of the catheter. The coil is advanced through the catheter until it reaches a predetermined site in the vessel at which time the pusher wire is retracted and the embolic coil is released. Such a system is disclosed in U.S. Pat. No. 6,203,547, entitled, “Vaso-occlusion Apparatus Having A Manipulable Mechanical Detachment Joint And A Method For Using The Apparatus.” 
         [0016]     Still another embolic device deployment system includes an elongated flexible pusher member slidably disposed within a lumen of a catheter. The embolic device is retained at the end of the pusher member with a detachment filament. When the embolic device is advanced to the predetermined site within the vessel, the detachment filament is withdrawn releasing the embolic device.  
       SUMMARY OF THE INVENTION  
       [0017]     The present invention is directed toward a vasooclusive embolic device deployment system for use in placing an embolic device at a predetermined site within a vessel including an elongated flexible catheter and an elongated pusher member, preferably having a lumen therethrough and being slidably disposed within the catheter. An embolic device, preferably taking the form of a helically wound embolic coil having a plurality of turns, is releasably coupled to the distal end of the pusher member. The detachment system also includes a detachment filament which extends through the lumen of the catheter, or preferably through the lumen of the pusher member. The detachment filament extends around a turn of the embolic coil and then back through the lumen of the catheter, or preferably through a lumen of the pusher member. When the embolic coil is at the predetermined site within the vessel, the detachment filament may be pulled proximally to decouple the detachment filament from engagement of the turn of the embolic coil to thereby release the embolic coil.  
         [0018]     In accordance with another aspect of the present invention, the vasooclusive embolic device deployment system includes a retaining clamp assembly mounted on the proximal end of the pusher member. The retaining clamp preferably takes the form of an adjustable chuck which applies a clamping pressure to the fiber to retain the filament until the chuck is opened to release the filament. The detachment filament extends through the clamp then through and the lumen of the pusher member and then around a turn of the embolic coil, and then back through the lumen of the pusher member and through the retaining clamp. Upon loosening the retaining clamp, one of the ends of the detachment filament may be pulled proximally to decouple the detachment filament from the embolic coil to thereby release the embolic coil at the predetermined site.  
         [0019]     These and other aspects of the present invention and the advantages thereof will be more clearly understood from the following description and drawings of a preferred embodiment of the present invention:  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is an enlarged, partially sectional view of an embodiment of an embolic device deployment system in accordance with the present invention;  
         [0021]      FIG. 2  is an enlarged, sectional view, illustrating in more detail the coil deployment system of  FIG. 1 ;  
         [0022]      FIGS. 3, 3   a,    3   b,  and  3   c  are enlarged, sectional views of the coil deployment system shown in  FIGS. 1 and 2  illustrating the sequential steps in the advancement of the embolic device, removal of a detachment filament, and release of the embolic device. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]      FIG. 1  generally illustrates one embodiment of an embolic device deployment system  10  of the present invention having an elongated flexible catheter  12  having a lumen  14  extending therethrough. An elongated flexible pusher member  16  is slidably disposed within the lumen  14  of the catheter  12 . The pusher member  16  includes a proximal end  18  and a distal end  20 , and the distal end  20  includes a tip portion  22  having an increase in diameter. Retractably mounted on the pusher member  16  at its distal end  20  is an embolic device, which preferably takes the form of an embolic coil  24 , formed of a plurality of helical turns  28  connected to an atraumatic distal bead  26 . While the embolic coil  24  is a preferred configuration of the embolic device, alternative device configurations are suitable such as embolic filaments, braids, expandable meshes, foams and stents. The tip portion  22  at the distal end  20  of the pusher member  16  engages the embolic coil  24 . Mounted on the proximal end  18  of the pusher member  16  is a retaining clamp assembly  30 , which includes a cap  32  which engages a chuck  44 . A detachment filament  35  having ends  36  and  38  extends through the retaining clamp assembly  30  and serves to retain the embolic coil  24  in position at the distal end  20  of the elongated pusher member  16 .  
         [0024]      FIG. 2  illustrates in more detail the configuration of the embolic device deployment system  10  of  FIG. 1 . The pusher member  16 , preferably has a lumen  40  therethrough and is slidably disposed within the lumen  14  of the catheter  12 . Preferably, the pusher member  16  is constructed from nitinol, but alternatively, the pusher member may be constructed from many materials that are pushable and flexible such as stainless steel, nylon, PTFE, other metals or polymers and composites. Additionally, the pusher member  16  should have an outside diameter in the range of about 0.002 to 0.020 centimeters.  
         [0025]     As shown, the embolic coil  24  is helically wound but may take various other forms. Such as for example, a randomly wound coil. The distal bead  26  is connected to the distal end of the embolic coil  24 . The embolic coil  24  also includes a lumen  42  extending therethrough created by the plurality of helical turns  28 . The diameter of the lumen  42  of the embolic coil  24  is slightly greater than the diameter of the distal end  20  of the pusher member  16 . With this configuration, the embolic coil  24  may be pushed distally by the distal end  20  of the pusher member  16 .  
         [0026]     A detachment filament  35  includes ends  36  and  38  which extend proximally from the proximal end of the clamp assembly  30 . The detachment filament  35  extends through the retaining clamp assembly  30  and through the lumen  40  of the pusher member  16 . The detachment filament  35  also loops around one of the plurality of helical turns  28  of the embolic coil  24  and is returned through the lumen  40  of the pusher member  16 , exits the pusher member  16  and extends through the lumen  46  of the chuck  44  of the clamp assembly  30  and then exits at the proximal end of the clamp assembly  30 . The cap  32  applies pressure to the chuck  44 , such that the chuck  44  applies squeezing pressure to the ends  36  and  38  of the detachment filament  35  thereby preventing movement of the detachment filament  35 . The embolic coil  24  may not be disengaged from the distal end  20  of the pusher member  16 , so long as the cap  32  remains tight on the chuck  44  and the detachment filament  35  is secured relative to the pusher member  16 . Finally, the detachment filament  35  is preferably constructed of nitinol, but alternatively may be formed from various other materials such as platinum, nylon, PTFE, flexible metals, polymers, or composites. Preferably, the material used for the detachment filament  35 should be very flexible, have a high tensile strength and a low elongation when a tensile force is applied to the filament. The diameter of the detachment filament  35  is in the range of about 0.001 to 0.090 centimeters and preferably on the order of about 0.002 to 0.020 centimeters.  
         [0027]      FIGS. 3, 3   a,    3   b,  and  3   c  generally illustrate the operation of the embolic device deployment system  10  and demonstrate the detachment filament release mechanism. More particularly,  FIG. 3  illustrates the catheter  12  positioned at a predetermined location, analogous to placement in a vessel and the pusher member  16  advanced through the lumen  14  of the catheter  12 , such that the embolic coil  24  exits the distal end of the catheter  12 . In addition, the retaining clamp assembly  30  maintains tension on the ends  36  and  38  of detachment filament  35 , such that the embolic coil  24  is retained at the distal end  20  of the pusher member  16 .  
         [0028]      FIG. 3   a  illustrates the embolic device deployment system  10  with the embolic coil  24  positioned at a desired location adjacent the distal section of the catheter  12 . The cap  32  is loosened to permit one end  36  of the detachment filament  35  to be pulled proximally. As the end  36  of the detachment filament  35  is pulled proximally from the retaining clamp assembly  30 , the other end  38  of the detachment filament  35  moves distally through the lumen  40  of the pusher member  16 .  
         [0029]      FIG. 3   b  illustrates the embolic device deployment system  10  with the end  36  of the detachment filament  35  pulled further proximally from the retaining clamp assembly  30  and the other end  38  of the detachment filament  35  withdrawn from its position around one of the plurality of helical turns  28  of the embolic coil  24 .  
         [0030]      FIG. 3   c  illustrates the embolic device deployment system  10  with the end  38  of the detachment filament  35  completely removed from the helical turn  28  of the embolic coil  24 . Finally, the embolic coil  24  disengages from the distal end  20  of the pusher member  16  and is released at the predetermined site within the vessel.  
         [0031]     As is apparent, there are numerous modifications of the preferred embodiment described above which will be readily apparent to one skilled in the art, such as many variations and modifications of the coil including numerous coil winding configurations, or alternatively other types of implant devices. There are obviously variations in the path and attachment of the detachment filament. Additionally, the retaining clamp assembly could also be modified with other methods used to apply pressure to the detachment filament ends. These modifications would be apparent to those having ordinary skill in the art to which this invention relates and are intended to be within the scope of the claims which follow.