Patent Publication Number: US-7722637-B2

Title: Heated vascular occlusion coil deployment system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a divisional of U.S. patent application Ser. No. 10/722,335, filed Nov. 25, 2003 now U.S. Pat. No. 7,179,276, which is a divisional patent application of U.S. patent application Ser. No. 09/897,819, filed Jun. 29, 2001, now U.S. Pat. No. 6,743,236, which is a divisional patent application of U.S. patent application Ser. No. 09/400,680, filed Sep. 21, 1999, now U.S. Pat. No. 6,277,126, which is a nonprovisional patent application of U.S. provisional patent application Ser. No. 60/103,087, filed Oct. 5, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a medical device for placing an embolic coil at a preselected location within a vessel of the human body, and more particularly, relates to a flexible delivery member having a heating element and a heat responsive coupling member at the distal tip of the delivery member for holding the embolic coil in order to transport the coil to a desired position within the vessel and release the embolic coil at that position. 
     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 dilatation balloons, radiopaque fluids, liquid medications and various types of occlusion devices such as balloons and embolic coils. Examples of such catheter devices are disclosed in U.S. Pat. No. 5,108,407, entitled “Method And Apparatus For Placement Of An Embolic Coil”; 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 devices for delivering embolic coils to preselected positions within vessel of the human body in order to treat aneurysms, or alternatively, to occlude the blood vessel at the particular location. 
     Coils which are placed in vessels may take the form of helically wound coils, or alternatively, may be random wound coils, coils wound within other coils or many other such configurations Examples of various coil configurations are disclosed in U.S. Pat. No. 5,334,210, entitled, “Vascular Occlusion Assembly; U.S. Pat. No. 5,382,259, entitled, “Vasoocclusion Coil With Attached Tubular Woven Or Braided Fibrous Coverings.” Embolic coils are generally formed of radiopaque metallic materials, such as platinum, gold, tungsten, or alloys of these metals. Often times, several coils are placed at a given location in order to occlude the flow of blood through the vessel by promoting thrombus formation at the particular location. 
     In the past, embolic coils have been placed within the distal end of the 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, for example, a guidewire to release the coil at the desired location. This procedure of placement of the 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 may be placed at the desired location. With these placements systems there is very little control over the exact placement of the coil since the coil may be ejected to a position some distance beyond the end of the catheter. 
     Numerous procedures have been developed to enable more accurate positioning of coils within a vessel. Still another such procedure involves the use of a glue, or solder, for attaching the embolic coil to a guidewire which, is in turn, placed within a flexible catheter for positioning the coil within the vessel at a preselected position. Once the coil is at the desired position, the coil is restrained by the catheter and the guidewire is pulled from the proximal end of the catheter to thereby cause the coil to become detached from the guidewire and released from the catheter system Such a coil positioning system is disclosed in U.S. Pat. No. 5,263,964, entitled, “Coaxial Traction Detachment Apparatus And Method.” 
     Another coil positioning system utilizes a catheter having a socket at the distal end of the catheter for retaining a ball which is bonded to the proximal end of the coil. The ball, which is larger in diameter than the outside diameter of the coil, is placed in a 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 thereby 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.” One problem with this type of coil placement system which utilizes a pusher wire which extends through the entire length of the catheter and which is sufficiently stiff to push an attachment ball out of engagement with the socket at the distal end of the catheter is that the pusher wire inherently causes the catheter to be very stiff with the result that it is very difficult to guide the catheter through the vasculature of the body. 
     Another method for placing an embolic coil is that of utilizing a heat releasable adhesive bond for retaining the coil at the distal end of the catheter. One such system uses laser energy which is transmitted through a fiber optic cable in order to apply heat to the adhesive bond in order to release the coil from the end of the catheter. Such a method is disclosed in U.S. Pat. No. 5,108,407, entitled, “Method And Apparatus For Placement Of An Embolic Coil.” Such a system also suffers from the problem of having a separate, relatively stiff element which extends throughout the length of the catheter with resulting stiffness of the catheter. 
     Still another method for placing an embolic coil is disclosed in co-pending U.S. patent application Ser. No. 09/177,848, entitled, “Embolic Coil Hydraulic Deployment System,” filed on Oct. 22, 1998 and assigned to the same assignee as the present patent application. This patent application discloses the use of fluid pressure which is applied to the distal tip of the catheter for expanding the lumen of the catheter in order to release the embolic coil. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward a vascular occlusion coil deployment system for use in placing an embolic coil at a preselected site within a vessel which includes an elongated flexible positioning member having a lumen extending therethrough. An elongated flexible delivery member having a lumen extending therethrough is slidably positioned within the lumen of the positioning member. A heating element is affixed to the distal end of the delivery member and a heat responsive coupling member adhesively bonds the embolic coil to the heating element. The heating element is adapted to be coupled to a source of energy through an energy transmission conductor which extends through the lumen in the delivery member. The heat responsive coupling member, bonding the heating element to the embolic coil, exhibits the characteristic of softening and yielding upon being heated. When energy is applied through the conductor to the heating element, the heating element causes the heat responsive coupling member to yield to thereby release the embolic coil at the preselected site. 
     In accordance with another aspect of the present invention, the heating element takes the form of resistive heating coil. At least a portion of this resistive heating coil is bonded to the interior of the heat responsive coupling member to thereby directly apply heat to the coupling when the heating coil is supplied with electrical energy. 
     In accordance with still another aspect of the present invention, the vascular occlusion coil deployment system for use in placing an embolic coil at a preselected site within a vessel includes an elongated flexible positioning member having a lumen extending therethrough. An elongated flexible delivery member is slidably positioned within the lumen of the positioning member. A heating element is affixed to the distal end of the delivery member and a heat responsive coupling member adhesively bonds the embolic coil to the heating element. The heating element is adapted to be coupled to a source of energy through an energy transmission conductor. The energy transmission conductor extends from the proximal end to the distal end of the delivery member through the lumen of the positioning member and is coupled to the heating element. The heat responsive coupling member, bonding the heating element to the embolic coil, exhibits the characteristic of softening and yielding upon being heated. When energy is applied through the conductor to the heating element, the heating element causes the heat responsive coupling member to yield to thereby release the embolic coil at the preselected site. 
     In accordance with still another aspect of the present invention, the energy transmission conductor takes the form of two electrical conductors which extend through the lumen of the delivery member and are connected to the resistive heating coil for applying electrical energy to the coil to thereby cause the coil to become heated. 
     In accordance with still another aspect of the present invention, the heating element is disposed within a lumen of the embolic coil. The heat responsive coupling member bonds the embolic coil to the heating element. When the heating element is energized the heat responsive coupling member heats. Upon heating the heat responsive coupling member softens thereby reducing its yield strength. This allows the heating element to be retracted into the positioning member breaking the heat responsive coupling member to release the coil. 
     In accordance with still another aspect of the present invention, the heat responsive coupling member is comprised of a hot melt adhesive. Other suitable materials include low melting temperature metals and metal alloys such as solder. Other suitable materials are those whose yield strength decreases by at least 50 percent when heated to about 65 degrees Celsius. 
     These aspects of the invention and the advantages thereof will be more clearly understated from the following description and drawings of a preferred embodiment of the present invention: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged, partially sectioned view of the vascular occlusion coil deployment system of the present invention; 
         FIG. 2  is an enlarged partially sectioned view showing the coil deployment system prior to placement within a catheter; 
         FIGS. 3 through 6  are enlarged partially sectioned views illustrating the sequential steps of positioning the vascular coil within a vessel releasing the coil at preselected site. 
     
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
       FIG. 1  generally illustrates a preferred embodiment of a vascular occlusion coil deployment system  10  of the present invention which is comprised of an elongated flexible catheter  12  which is utilized to position a coil deployment mechanism  14 . A Luer connector  16  is connected to the proximal end of the catheter  12  and the coil deployment mechanism  14  is connected to a power supply  18  for applying energy to the coil deployment mechanism  14 . 
       FIG. 2  illustrates in more detail the construction of the coil deployment mechanism  14 . More particularly, the deployment mechanism  14  includes an elongated positioning member  22  which is approximately the same length as the outer catheter  12  and which is slidably received by the catheter  12 . Positioning member  22  has a lumen extending from its proximal end to its distal end. Coil deployment mechanism  14  also includes a tubular, delivery member  24  which is slidably positioned within the lumen of positioning member  22 . Located at the distal end of the delivery member  24  is a heating element  26 . The heating element  26  is bonded to the embolic coil  20  by a heat responsive coupling member  30 . 
     The heat responsive coupling member  30  may take the form of any biocompatible adhesive which, upon being heated, softens so that it may be stretched. Preferably, this heat responsive coupling member  30  is comprised of a hot melt adhesive, such as, for example, a hot melt adhesive manufactured by Minnesota Mining and Manufacturing sold under the name Jet Melt, Catalog No. 3783-TC. The temperature required to soften this material is on the order of 63 degrees centigrade. 
     Also, as illustrated in  FIG. 2 , the heating element  26  which is preferably a resistively heated coil is coupled to a pair of energy transmission conductors  28 ,  29 . Preferably the energy transmission conductors  28 ,  29  are electrical conductors also coupled to power supply  18 . Upon application of an electrical current to the pair of conductors  28 ,  29  the heating element  26  begins to heat to thereby cause the heat responsive coupling member  30  to increase in temperature. As the heat responsive coupling member  30  becomes warm it softens and has a lower yield strength, thus, breaking when the delivery member  24  is retracted to release the embolic coil  20 . 
     More particularly, and as illustrated in  FIGS. 3 through 6 , the vascular occlusion coil deployment system  10  is inserted into a blood vessel  40  and is moved to a position within the blood vessel  40  to a position where it is desirable to place the embolic coil  20 . When the catheter  12  has been positioned at a location slightly proximal of the preselected site for placement of the embolic coil ( FIG. 4 ), the coil deployment mechanism  14  is pushed out of the distal end of the catheter  12  and electrical energy is then applied to the heating element  26  to thereby soften the heat responsive coupling member  30 . Once the heat responsive coupling member  30  softens, the delivery member  24  is retracted, thus disengaging the heating element  26  from embolic coil  20  breaking the adhesive bond of heat responsive coupling member  30 . As the delivery member  24  is retracted, there is no longer engagement between the heating element  26  and the embolic coil  20  and the coil is released. 
     Finally, and as illustrated in  FIG. 6 , the coil deployment mechanism  14  is withdrawn back into the catheter  12  and the embolic coil  20  remains in its deployed position. 
     With the vascular occlusion coil deployment system of the present invention it is possible to place an embolic coil very precisely at a desired location within a vessel. Once the coil has been placed in a preselected location by catheter, the deployment mechanism may be activated by applying energy to a coil release mechanism to thereby cause the coil to be released and deposited at a desired location. 
     As is apparent, there are numerous modifications of the preferred embodiment described above which will become readily apparent to one skilled in the art, such as many variations and modifications of the deployment system including many different variations of the heating element, many variations of energy sources for heating the adhesive such as optical, radiofrequency, and acoustical, many variations of energy transmission conductors such as optical fiber, and many variations of heat softening adhesives. 
     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.