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 slidably disposed within the lumen of the catheter. An embolic device is retained within the delivery catheter by a mechanical interlocking mechanism which includes a deflectable engagement member attached to the distal end of the pusher member and extends through a retaining ring at the proximal end of the embolic device. A detachment member extends through an aperture at the distal end of the engagement member thereby locking the embolic device onto the pusher member. When the detachment member is withdrawn from the aperture of the engagement member the engagement member deflects to release the embolic device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS(S) 
     This patent application is a continuation-in-part of U.S. patent application Ser. No. 11/143,052, filed on Jun. 2, 2005, entitled, “Stretch Resistant Embolic Coil Delivery System With Mechanical Release Mechanism.” 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a medical device for placing a stretch resistant 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 a stretch resistant embolic coil, through the tortious vasculature of the human brain to a selected site within the vessel or within an aneurysm. 
     2. Description of the Prior Art 
     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.” 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. 
     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. 
     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. 
     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.” 
     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.” 
     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 U.S. Pat. No. 5,108,407, entitled “Method and Apparatus for Placement of an Embolic Coil.” 
     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.” 
     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.” 
     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.” 
     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.” 
     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.” 
     A still further embolic device deployment system for placement of an embolic device, or coil, includes a delivery catheter and a flexible pusher member. The embolic device is retained by an interlocking mechanism which includes a detachment member which extends through an aperture in an engagement member. The engagement member engages a ring on the embolic device. When the detachment member is withdrawn from the aperture, the embolic device is released. One such deployment system is disclosed in a concurrently filed patent application U.S. Ser. No. 11/143,051, entitled, “Embolic Coil Delivery System With Mechanical Release Mechanism,” and assigned to the same assignee as the present application. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a vascular occlusive embolic device deployment system for use in placing an embolic device at a predetermined site within a vessel which includes an elongated flexible catheter, an elongated pusher member having a lumen extending therethrough and being slidably disposed within the lumen of the catheter. The embolic device takes the form of an embolic coil defining a central lumen extending between the proximal and distal ends of the coil and having a retaining ring disposed on the proximal end of the coil. A resilient engagement member is fixedly attached to the distal end of the pusher member and includes an aperture extending through the distal end thereof. The engagement member has a normally biased position which extends in a plane parallel to the control axis of the lumen of the pusher member but the distal end of the engagement member is deflected out of this plane toward this central axis and extends through the retaining ring of the stretch-resistant embolic device. The deployment system also includes a support member which takes the form of an elongated projection member extending from the distal end of the pusher member and parallel to the plane of the retaining ring to thereby support the retaining ring during the withdrawal of the engagement member. In addition, the deployment system includes an elongated detachment member which extends from the proximal end of the pusher member, through the lumen of the pusher member and through the aperture of the engagement member such that when the detachment member is pulled proximally of the deployment catheter the distal end of the detachment member is withdrawn from the aperture of the engagement member to thereby release the embolic device. 
     In accordance with another aspect of the present invention, the embolic device takes the form of an embolic coil having a fiber such as a platinum wire extending between the distal end of the coil and the retaining ring. 
     In accordance with another aspect of the present invention, there is provided a deployment system for use in placing an embolic device at a predetermined site within a vessel which includes an elongated flexible catheter, an elongated pusher member being slidably disposed within the lumen of the catheter. The embolic device takes the form of an embolic coil defining a central lumen extending between the proximal and distal ends of the coil. A stretch resistant member having first and second ends in which the first end of the stretch resistant member is attached to the distal section of the coil and the second end of the stretch resistant member is attached to a retaining ring. A resilient engagement member is fixedly attached to the distal end of the pusher member and includes an aperture extending through the distal end thereof. The engagement member has a normally biased position which extends in a plane parallel to the central axis of the lumen of the pusher member but the distal end of the engagement member is deflected out of this plane toward this central axis and extends through the retaining ring of the stretch-resistant embolic device. The deployment system also includes a support member which takes the form of an elongated projection member extending from the distal end of the pusher member and parallel to the plane of the retaining ring to thereby support the retaining ring during the withdrawal of the engagement member. In addition, the deployment system includes an elongated detachment member which extends from the proximal end of the pusher member, through the lumen of the pusher member and through the aperture of the engagement member such that when the detachment member is pulled proximally of the deployment catheter the distal end of the detachment member is withdrawn from the aperture of the engagement member to thereby release the embolic device. 
     In accordance with another aspect of the present invention, the second end of the stretch-resistant member is attached to the proximal section of the coil, as opposed to the retaining ring, to prevent the coil from stretching, and the proximal end of the coil is attached to the retaining ring. 
     In accordance with another aspect of the present invention, the engagement member is deflected into an L-shaped configuration and one of the legs is attached to the pusher member and the other leg extends through the retaining ring. The aperture of the engagement member extends through the leg which extends through the retaining ring such that when the detachment member extends through the retaining ring of the embolic device such that the embolic device is interlocked onto the engagement member until the detachment member is withdrawn. 
     In accordance with another aspect of the present invention, the aperture of the engagement member has a central axis which extends generally at a right angle to the central axis of the retaining ring. In addition, the embolic device takes the form of a helically wound embolic coil having a central axis which extends at a right angle to the central axis of the retaining ring. The stretch resistant member is attached to and extends from a distal section to a proximal section of the helically wound coil. 
     In addition, the vascular embolic device deployment system preferably includes a retaining clamp mounted on the proximal end of the pusher member, and the detachment member extends from a position proximal of the retaining clamp and through a lumen in the clamp in order that the detachment member may be clamped in a fixed position prior to the release of the embolic device. Upon release of the clamp, the detachment member may be withdrawn from the aperture of the engagement member to thereby release the embolic device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged, partially sectional view of an embodiment of an embolic device deployment system in accordance with the present invention; 
         FIG. 1A  is an enlarged, partially sectional view of a second embodiment of an embolic device deployment system in accordance with the present invention; 
         FIGS. 2A ,  2 B,  2 C and  2 D are enlarged, sectional views, illustrating in more detail the coil deployment system of  FIG. 1A ; 
         FIGS. 3 ,  3 A,  3 B, and  3 C are enlarged, sectional views of the coil deployment system shown in  FIG. 1A  illustrating the sequential steps in the advancement of the embolic device, removal of a detachment member, and release of the embolic device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  generally illustrates one embodiment of a vascular occlusive embolic device deployment system  10  which includes a sheath introducer  12  having a lumen  14  extending therethrough and having an elongated pusher member  16  slidably disposed within the lumen  14  of the sheath introducer  12 . An elongated engagement member  18  extends distally from the pusher member  16  and has an aperture (to be described hereinafter) extending through the distal end thereof. The engagement member  18  is preferably formed from a distal section of the wall and of the pusher member  16  but may be formed as a separate member attached to the distal end of the pusher member  16 . 
     The deployment system  10  also includes an embolic device  23 , which as illustrated, preferably takes the form of a helically wound embolic coil, which is disposed in the distal section of the sheath introducer  12 . While the embolic device as illustrated is shown as a helically wound coil various other types of embolic devices, such as filaments, braids, foams, expandable meshes and stents, could be delivered using the present deployment system and various other coil configurations could be delivered using this system. A weld, or solder, bead  24  is formed at the distal end of the embolic device  23  to provide an atraumatic tip for the embolic device. In addition, the distal end of a stretch-resistant member  25 , which preferably takes the form of a platinum wire, is attached to the distal bead  24  and extends proximally through the central lumen of the coil. While the stretch-resistant member preferably takes the form of a platinum wire, other materials or composites such as polymers, metals and ceramics, having a low elongation relative to the coil elongation may also be suitable. Alternatively, the distal end of the stretch-resistant member could be attached to the coil at a more proximal location in the distal section of the coil. A headpiece  21 , which takes the form of a cylindrical member is disposed on the proximal end of the embolic device  23 . The headpiece  21  includes a retaining ring  28  which extends proximally from the cylindrical shaped headpiece. The proximal end of the stretch resistant member is then attached to the distal edge of the headpiece  21 . Preferably, the retaining ring  28  has a central axis which extends at right angles to the central axis of the sheath introducer  12  and also extends at right angles to the central axis of the helically wound embolic coil. 
       FIG. 1A  illustrates another variation of the stretch-resistant embolic device  23  in which the distal end of a stretch-resistant member  27  is attached to the bead  24  at the distal end of the coil and the proximal end of the stretch-resistant member is attached to the turns in the proximal section of the coil by use of a weld, or solder, bead  29 . 
     As illustrated in  FIGS. 1 ,  1 A,  2 A and  2 B, the engagement member  18  extends through the retaining ring  28 . The resilient engagement member  18  extends from the distal end of the pusher member  16  and is normally biased in a direction parallel to the longitudinal axis of the pusher member  16 . The engagement member  18  is shown deflected towards the central axis of the lumen of the pusher member  16  forming a generally L-shaped configuration as it extends through the retaining ring  28 . An elongated detachment member  30  extends from the proximal end of the deployment system  10  and through a lumen in the pusher member  16  and then through the aperture  22  ( FIG. 2B ) of the engagement member  18  and serves the function of interlocking the embolic device  23  to the pusher member  16  until such time as the detachment member  30  is withdrawn proximally. In order to improve the release mechanism an elongated support member  17  extends distally from the pusher member  16  generally in a direction parallel to the longitudinal axis of the pusher member and preferably formed from a distal section of the wall of the pusher member, but may be formed as a separate member attached to the distal end of the pusher member. The support member  17  preferably has an aperture  17 A which extends therethrough. 
     The detachment member  30  preferably takes the form of a small diameter elongate filament, however, other forms such as wires or tubular structures are also suitable. While the detachment member  30  is preferably formed of nitinol, other metals and materials such as, stainless steel, PTFE, nylon, ceramic or glass fiber and composites may also be suitable. 
     A Tuohy-Borst type of clamp  32  is mounted on the proximal end of the pusher member  16  and when tightened onto the detachment member  30  serves to prevent movement of the detachment member until such time as the clamping cap  34  is loosened to release the grip onto this member. 
       FIGS. 2A and 2B  illustrate the interlocking arrangement between the embolic device  23  and the pusher member  16  as shown in  FIG. 1A , however, these figures illustrate the operation of the deployment system once the pusher member  16  has been moved distally to a position so that the distal end of the pusher member  16  extends slightly out of the distal end of the sheath introducer  12  or a delivery catheter thereby exposing the embolic device  23 . 
     As illustrated in  FIGS. 2C and 2D , once the embolic device  23  has been moved out of the end of the sheath introducer  12  the detachment member  30  may be pulled proximally to withdraw the detachment member from the aperture  22  of the engagement member  18  to thereby cause the engagement member to disengage from the retaining ring  28  of the embolic device thereby releasing the embolic device  23  at a preselected position. The support member  17  functions to ensure the release of the embolic device  23  by restricting the movement of the retaining ring  28  as the engagement member  18  returns to its normally biased position generally parallel to the longitudinal axis of the pusher member  16  to thereby release the embolic device. Alternatively, if desired, the detachment sequence described above and illustrated in  FIGS. 2A through 2D  may be executed while the embolic device  23  is still within the lumen of sheath introducer  12  or a delivery catheter. 
     One of the important advantages of the present invention is that the embolic device may be placed at a desired location within a vessel, or within an aneurysm, with the configuration of the device deployment system as shown in  FIGS. 2A and 2B . If it is determined that the embolic device is improperly positioned, the embolic device  23  may then be withdrawn from that location and placed at another location, or even removed from the body by first withdrawing the pusher member  16  and the embolic device totally back into the delivery catheter. Once the embolic device has been entirely withdrawn back into the delivery catheter, the catheter may then be moved to a more desirable location and the embolic device may then be released at the new location. With the addition of the stretch resistant member  27 , the embolic device may be withdrawn without concern that the coil will stretch and become very difficult to remove. 
       FIGS. 3 ,  3 A and  3 B generally illustrate the sequence of placing an embolic device, such as a helical wound coil into an aneurysm  36  which extends from a vessel wall  38 . More particularly,  FIG. 3  illustrates the vascular occlusive embolic device deployment system  10  in the same configuration as shown in  FIG. 1A  after the pusher member and associated embolic device have been inserted into a delivery catheter  35  and advanced into a position for deployment of the embolic device  23 , shown as a helical embolic coil, into the aneurysm  36 .  FIG. 3A  illustrates the deployment device having a configuration similar to  FIG. 2A  with the embolic device  23  being placed within the aneurysm  36  but prior to withdrawal of the detachment member  30 . At this point, prior to the withdrawal of the detachment member  30 , as previously mentioned, if it is determined that the embolic device has been improperly placed, the pusher member may be withdrawn thereby withdrawing the embolic device back into the delivery catheter  35  for repositioning to a different location, or alternatively, to remove the embolic coil entirely from the body. 
       FIG. 3B  illustrates the deployment device after the detachment member  30  has been removed from the engagement member  18  thereby releasing the embolic device within the aneurysm  36 , and  FIG. 3C  illustrates the deployment device after the pusher member  16  has been withdrawn back into the delivery catheter  35  at the completion of the procedure or alternatively in order to insert a second coil through the delivery catheter  35  and into the same aneurysm. 
     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 embolic device including numerous coil winding configurations, or alternatively other types of embolic devices. Also, there are many possible variations in the materials and configurations of the release mechanism. 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.