Abstract:
A cardiac pacemaker or other CRT device has one or more fine wire leads to the heart. Formed of a glass, silica, sapphire or crystalline quartz fiber with a thin metal coating, a unipolar lead can have an outer diameter as small as about 300 microns or even smaller. The thin metal conductor poses unique challenges for attachment to standardized connectors as well as to stimulation electrodes. This invention describes structures and materials for creating robust and durable electrically conductive connections between the fine wire lead body and a proximal standardized connector and distal ring and tip electrodes by utilization of fine metal coils or mesh and electrically conductive adapters to aid in stabilizing the connections.

Description:
[0001]    This application claims benefit from provisional application No. 61/277,528, filed Sep. 28, 2009, and is a continuation-in-part of application Ser. No. 12/887,388, filed Sep. 21, 2010, and also application Ser. No. 12/590,851, filed Nov. 12, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention concerns wiring for electrostimulation and sensing devices such as cardiac pacemakers, ICD and CRT devices, and neurostimulation devices, and in particular encompasses an improved implantable fine wire lead for such devices, a lead of very small diameter and capable of repeated cycles of bending without fatigue or failure. The term therapeutic electrostimulation device (or similar) as used herein is intended to refer to all such implantable stimulation and/or sensing devices that employ wire leads. A fine wire lead consists of several key components, including a lead body, a proximal connector, and one or more distal electrodes, which are affixed to the lead body. A key aspect to fabrication of a robust and durable glass or silica fiber-based fine wire lead is the manner in which the proximal connector is attached to the lead body, and the one or more electrodes to the distal end of the lead. This invention is directed towards defining a new adapter subassembly to enable a robust attachment of a connector and/or electrodes to a glass fiber fine wire lead body. 
         [0003]    Definition of a robust and durable glass fiber fine wire pacing electrostimulation lead was the subject of copending U.S. application Ser. No. 12/156,129, filed on May 28, 2008 (Pub. No. 2009/0299446), and Ser. No. 12/590,51, filed Nov. 12, 2009, incorporated entirely herein by reference. In addition, copending application Ser. No. 12/660,344, filed Feb. 23, 2010, describes several forms of connections for such leads, and is also incorporated herein by reference. 
         [0004]    This application describes further details and structure for connection of a fine wire lead with electrodes and connectors as depicted in provisional application Ser. No. 61/208,216 filed on Feb. 23, 2009, and also provisional application No. 61/277,052, filed Sep. 21, 2009, both provisional applications of which are incorporated herein by reference. 
         [0005]    It is an object of the present invention described herein to address important structural details of the fine wire glass fiber leads described in the previous referenced patent applications. Those details refer to an adapter specifically designed to facilitate permanent stable attachment of standardized connectors, such as IS-1 and IS-4 connectors, as well as electrodes, to a glass fiber fine wire lead body. The adapter described herein serves to increase the strength of attachment of connectors and electrodes to the glass fiber fine wire lead body. 
       SUMMARY OF THE INVENTION 
       [0006]    As described in referenced application Ser. No. 12/156,129, a flexible and durable fine wire lead for implanting in the body, with connection to a pacemaker, ICD, CRT or other cardiac pulse generator, is formed from a drawn silica, glass, sapphire crystalline quartz fiber core with a conductive metal buffer cladding on the core. A polymer coating can be layered over the metal buffer cladding, which may be biocompatible and resistant to environmental stress cracking or other mechanism of degradation associated with exposure and flexure within a biological system. The outer diameter of the fine wire lead preferably is less than about 750 microns, and may be 200 microns or even as small as 50 microns. Metals employed in the buffer can include aluminum, gold, platinum, titanium, tantalum, silver, or others, as well as metal alloys of which MP35N, a nickel-cobalt based alloy is one example. In one example of metal cladding, a molten metal film, such as gold or silver is applied to the drawn silica, glass, sapphire crystalline quartz fiber core immediately upon drawing and providing a protective hermetic seal over the silica, glass, sapphire crystalline quartz fiber. 
         [0007]    Alternatively, a thin film of polymer may be coated onto the fiber core immediately after drawing the core, with or without a hermetic carbon underlayment. In this case, a metallized conductor is deposited upon the polymer surface in a secondary process step. 
         [0008]    If constructed in this fashion, metallization of the polymer surface can be accomplished via a continuous passage of polymer encapsulated silica or glass fiber through a deposition chamber during the metal deposition process. Such metal deposition may be carried out by vapor deposition, electroplating—especially upon an electrically conductive carbon surface, by coating with an electrically conductive ink, or by one of numerous other metal deposition processes known in the art. In the case of vapor deposition and related processes governed by line-of-sight considerations, one or more metal targets, that is, sources for vaporized metal, may be positioned within the metal deposition chamber in such a way as to insure overlap and complete 360 degree coverage of the fiber during the metal deposition process. Alternately, the fiber may be turned or rotated within the vapor deposition field to insure complete and uniform deposition. 
         [0009]    Vapor deposition processes are typically carried out in an evacuated chamber at low atmospheric pressure (approximately 1.0×10 −6  torr). After evacuation is attained, the chamber is backfilled with a plasma-forming gas, typically argon, to a pressure of 2.0×10 −3  torr. Masking may be pre-applied to the carbon and/or polymer surface to enable a patterned coating of metal on the carbon and/or polymer surface. Such a pattern may be useful for creating two or more separate electrically conductive paths along the length of the fine wire lead, thus enabling fabrication of a bipolar or multipolar conductor upon a single fine wire lead. Inherent in the concept of a metallized fine wire lead is the ability to use more than one metal in the construction of such leads. For instance, an initial metal may be deposited on the basis of superior adhesion to the carbon and/or polymer underlayment. One or more additional metals or metal alloys could then be deposited on the first metal. Intent of the second metal would be to serve as the primary conductive material for carrying electrical current. 
         [0010]    If more than one conductor is needed, multiple unipole fibers can be used, having one conductor per fiber. Alternatively, the silica or other type fiber can serve as a dielectric with a wire in the center of the fiber core as one conductor and the metallic buffer layer on the outside of the fiber core, providing fiber protection, and acting as the coaxial second conductor or ground return. The flexibility of a composite structure consisting of multiple unipolar fibers can be controlled by employing hollow fibers. A thin wall hollow fiber core will have greater flexural response for a given applied force, than a solid fiber core of the same material, and the same overall diameter. 
         [0011]    The completed metallized lead body may be conveniently coated with a thin lubricious and protective polymeric material, such as Teflon, to provide necessary electrical insulation. Polyurethane or silicone may conveniently be used for such a jacketing material, providing biocompatibility and protection from the internal biochemical environment of the body. A composite polymeric coating can also be incorporated, consisting of a thin Teflon coating directly on the metallized glass fiber to provide insulation and lubricious protection from friction-related damage, along with an outer polymeric coating of polyurethane or silicone to provide additional electrical insulation as well as biocompatibility. As referenced earlier, a coaxial lead body design incorporating two independent electrical conductors may be constructed in which a metal conductor is embedded within the central glass or silica core, with the second conductor being applied to the carbon and/or polymer buffer residing on the outer surface of the glass or silica core. 
         [0012]    In an additional embodiment of metal cladding for the glass fiber, temporary sealing materials may be applied to the glass fiber for protection. Subsequent steps carried out in a controlled environment facilitate removal of the temporary sealing materials, followed by resurfacing the fiber with metal or other material, such as polymer or carbon. Such steps enable controlled metal surfaces to be applied directly to the glass fiber, if so desired. Temporary sealing materials may consist of polymers, carbon, or metals, which are chosen for ease of removal. In the case of polymers, removal may be facilitated by dissolution in appropriate solvent, heat, alteration in pH or ionic strength, or other known means of control. Carbon and metals may be removed by chemical or electrochemical etching, heating, or other known means of control. 
         [0013]    As indicated by the above, considerable flexibility exists for the construction of a robust and durable electrically conductive small diameter lead body for therapeutic electrostimulation. This flexibility is considered advantageous, as an additional set of requirements must be met for achieving a robust and stable attachment of proximal and distal terminals to the lead body. 
         [0014]    The above-referenced application Ser. Nos. 12/156,129 and 12/660,344 describe connectors for fine wire leads of the type described above. In addition, other metal wire member configurations are applicable. One such configuration consists of multiple wire coils, with the coils all wrapping in the same direction, or one or more coils wrapping in opposite directions. In addition, one or more straight wire segments are envisioned. These wire segments can run roughly parallel with the glass fiber. Finally, various wire mesh member configurations are applicable. Any of various electrically conductive metals or metal alloys is suitable for use in fabricating the metallic wire or metallic mesh member components. These metals include but are not limited to silver, gold, platinum, aluminum, copper or MP35N. In addition, electrically conductive, non-metallic materials such as polymers may be used. 
         [0015]    An adapter can be defined by which the connection between connectors or electrodes and glass fiber fine wire lead is facilitated, producing a robust physically stable electrical connection. The adapter is an electrically conductive metal or non-metal component sized to fit within an IS-1 or IS-4 connector, or within a ring electrode or terminal electrode. This adapter is fabricated to contain holes sized to receive terminal ends of one or more glass fiber fine wire lead filars, which incorporate wire coils or other electrically conductive wire or mesh components such as described in the preceding paragraphs. The adapters are bonded to the metal coils by way of electrically conductive adhesive, laser welding, crimping, or a combination of methods. In addition, for glass fibers that terminate within an adapter, the adapter may be arranged so that the fiber terminates within a tubular channel that runs the length of the adapter. With this arrangement, an alternative means of sealing the terminal end of the glass fiber within the adapter is via glass welding, in which a glass composition having a melting temperature lower than either the adapter or the glass fiber is introduced into the channel with heat to seal the channel with molten glass, which is then allowed to cool. 
         [0016]    After an adapter is firmly affixed to a glass fiber, the adapter is then positioned within a IS-1 or IS-4 connector, or ring electrodes or terminal electrode. The manner of attachment of the adapter to the connector or electrode may be by electrically conductive adhesive, crimping, laser welding, or physical engagement facilitated by screw patterns or bayonet detents or other such means of material interference, as well as various combinations of these means. 
         [0017]    Use of such adapters as described here is made possible by the small diameter glass fiber fine wire lead filars utilized for fabricating lead body. The small diameter filars make it possible for multiple electrically insulated filars to pass into and/or through the adapters envisioned herein, while allowing adapters to be sized for proper incorporation into IS-1 or IS-4 connectors, as well as ring and terminal electrodes. 
         [0018]    Incorporation of adapters along with electrically conductive metallic or polymeric wire members such as the coils or mesh described above increase the intimacy of physical contact between the electrode or connector, with the glass fiber. The metal or electrically conductive polymeric coils and mesh configurations serve to protect the terminal of the glass fiber from potential crush damage resulting from crimping or other physical means used to stabilize the connection between adapter and glass fiber. The various metallic or electrically conductive wire configurations also serve as tension members. If tension is applied to the electrode or connector, the amount of force required to separate the adapter and associated electrode or connector from the glass fiber will be increased by the tensile loading of the metallic wire component or components. 
         [0019]    Attachment of the electrically conductive polymer or metal adapter with the electrically conductive wire or mesh components as described in the preceding several paragraphs to the associated lead body is by way of one or more of the means as described earlier, namely by potting with electrically conductive adhesive or solder, or with molten metal or metal alloy or via laser welding, or physical compression or crimping. Alternatively, if the adapter is attached to the lead body prior to metallizing the lead body, then a conventional non-electrically conductive adhesive will suffice. Alternatively, the adapter may be bonded to the proximal end of the lead body by employing heat, via laser, ultrasonic welding, or other means of creating a robust bond between materials. 
         [0020]    The outer surface contour of the electrically conductive polymer or metal adapter described above is designed so as to match an opposite pattern set in the pin or ring electrodes of a standardized connector for an electrostimulation or sensing device utilizing a IS-1 or IS-4 connector, or the ring or terminal electrodes at the distal end of the fine wire lead. In the case of the IS-1 or IS-4 connector, this pattern may be a screw or other detent means, exemplified by a bayonet style connection. 
         [0021]    It is among the objects of the invention to improve the durability, lifetime flexibility and versatility of wire leads for pacemakers, ICDs, CRTs and other cardiac pulse generators, as well as electrostimulation or sensing leads for other therapeutic purposes within the body. This is effectuated in part by the invention described here, involving means and materials for achieving a robust and durable attachment of a standard connector to the terminus of a glass/silica lead body, as well as ring and tip electrodes to the distal terminus of a glass/silica lead body. These and other objects, advantages and features of the invention will be apparent from the following description of preferred embodiments, considered along with the accompanying drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a schematic drawing in perspective showing a wire coil serving as a tensile member in the connection of an electrode or connector to a fine wire lead body. 
           [0023]      FIG. 2  is a schematic drawing in perspective showing a metallic wire mesh serving as a tensile member in the connection of an electrode or connector to a fine wire lead body. 
           [0024]      FIG. 3  is a schematic drawing in perspective showing a metal coil serving as a tensile member overlaying a thin-walled electrically conducting metal tube, in the connection of an electrode or connector to a fine wire lead body. 
           [0025]      FIGS. 4 and 4A  are a schematic sectional view and a section view showing a dual connector at a termination of two conductive fibers, detailing how the connection is made. 
           [0026]      FIGS. 5 and 5A  are a schematic sectional view and an end view showing a pass through adapter for two conductive fibers, one of which is electrically connected to the adapter. 
           [0027]      FIG. 6  is a schematic sectional view showing a four conductor lead and connector, at the termination of four conductive fibers. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]      FIG. 1  shows a connection between the glass fiber lead,  10  (such as shown and described in referenced application Ser. No. 12/156,129), and an electrode or connecter body  12 . A wire coil  14  is wrapped around the glass fiber to make a connection between the coating on the glass fiber, not shown, and the electrode or connector body  12 . The wire coil  14  provides electrical connection and strain relief between the glass fiber lead  10  and the connection body  12 . The wire coil  14  also acts to maintain the electrical connection when the joint between the glass fiber lead  10  and the electrode or connecter body  12  is flexed. 
         [0029]      FIG. 2  shows a connection between the glass fiber lead  10  and the electrode or connecter body  12 . A wire mesh  16  is wrapped around the glass fiber to make a connection between the coating on the glass fiber, not shown, and the electrode or connector body  12 . The wire mesh  16  provides electrical connection and strain relief between the glass fiber lead  10  and the connection body  12 . The wire mesh  16  also acts to maintain the electrical connection when the joint between the glass fiber lead  10  and the electrode or connecter body  12  is flexed. 
         [0030]      FIG. 3  shows a connection between the glass fiber lead  10  and the electrode or connecter body  12 . A metal coil  18  is wrapped around the glass fiber to make a connection between the coating on the glass fiber, not shown, and a thin-walled electrically conducting metal tube  20 . The metal coil  18  provides electrical connection and strain relief between the glass fiber lead  10  and the connection body  12 . The metal coil  18  also acts to maintain the electrical connection when the joint between the glass fiber lead  10  and the electrode or connecter body  12  is flexed. 
         [0031]      FIG. 4  shows a two pin conductor and termination for conductive fibers  31  and  32 , and these can be as described in application Ser. No. 12/156,129. Metal coils  34  act as strain relief for the fibers  31  and  32 . As illustrated, the metal coils  34  are anchored within respective generally cylindrical receiving bodies  36 ,  38  where the coils are wrapped closely around the metallized conductive fibers  31  and  32 . The metal coils are welded to the receiving bodies  36 ,  38 , the welds being indicated at  40 ,  40   a  and  42 . At the end of each conductive fiber  31 ,  32  is a guide  44 ,  46 , respectively, these guides being secured to the ends of the fibers by sealed glass  48 . Each of the receiving bodies  36 ,  38  is filled with conductive adhesive as indicated at  50 , thus assuring conductive contact among the conductive fiber, the coil and the receiving body. The guides  44  and  46  center the conductive fibers  31  and  32  into their corresponding receiver bodies. The receiving bodies preferably are swaged as shown at  52  and  54  to help retain the components in place in the receiving bodies. As illustrated, the entire volume around the conductive fiber within the receiving body need not be filled. 
         [0032]    The illustrated connector includes an outer connector segment or connector body  56  which is adapted to fit with a standard connector (not shown) for an electrostimulation device or other electrical connector which can be implanted. Both the conductive fiber terminal assemblies are placed appropriately within the outer connector segment  56 , such that the receiving body  36  is in contact with the connector segment  56  at an internal wall and the other receiving body  38  is at a prescribed position for receiving a connecting pin, as shown in both  FIGS. 4 and 4A , and the components are potted in place with insulating material  58 . This forms a connector device to be fit with a standard connector, by which the outer surface of the connector segment or body  56  makes contact with one terminal and a pin connector socket  60  is positioned to receive a pin as a second terminal. This is an end that for reference purposes can be called a distal end. As illustrated, the receiving body  38  can have a swage at  62 , forming an inner annular ridge, for gripping a pin connector. 
         [0033]    Note that the weld  42  on the receiving body  38  can be made before assembly into the outer connector segment  56 , as can a portion of the weld  40 . The weld  40  is then extended after insertion of the receiving body  36  into the outer body  56 , to secure the receiving body  36  and conductive fiber assembly to the outer shell or body or outer connector segment  56 . 
         [0034]      FIGS. 5 and 5A  show a pass through adapter  65  which utilizes some of the connector principles described relative to  FIGS. 4 and 4A . This pass through adapter is conductively connected to only one conductive silica fiber, the upper fiber  66  as seen in  FIGS. 5 and 5A . Since only the conductive fiber  66  is to be electrically connected to the outer ring  70  of the adapter, provision is made to connect the fiber  66  and a strain relieving coil  34  secured around the fiber to the metal outer shell or ring  70 . This is shown in the upper portion of  FIG. 5 , where the strain relieving coil  34  wraps closely around the conductive fiber  66  and is welded at  72  to the body  70  of the adapter, at both left and right as seen in  FIG. 5 . The lower conductive fiber  68 , however, is not grounded to the adapter body  70 . For this purpose a pair of discs are included, one insulated and one metal and conductive. The discs are shown at both left and right of the adapter, at  74  (insulative) and at  76  (conductive). These discs are shaped generally as defined by the entire outer ring  70  as seen in  FIG. 5A , with upper and lower holes for the fiber assemblies. They may be retained by fastener pins  77  ( FIG. 5A ), provided they are non-conductive, or by adhesives. The upper holes in the insulative and conductive discs  74  and  76  are larger, as can be seen in the upper part of  FIG. 5A , so as to provide room for welding of the coil  34  to the metal conductive adapter body  70 . The welds  72  do not touch the outer conductive disc layer  76 . 
         [0035]    However, in the lower part of  FIG. 5  the welds  78  connect the coil  34  to the outer conductive disc  76  (at both left and right), but not to the conductive body  70  of the adapter. Here, the holes through the discs  74  and  76  are smaller so that the weld can engage with the outer disc layer  76 . As shown in the drawing, the conductive body  70  is spaced away from the welds. Thus, the upper conductive fiber  66  is firmly grounded to the adapter body or outer ring  70 , while the lower conductive fiber  68  is not. 
         [0036]    Both openings through the conductive metal adapter body  70  are filled with adhesive. For the upper fiber  66 , this is a conductive adhesive  80 , while the lower assembly has a non-conductive adhesive  82 . This adhesive  82  serves the insulation function described above. Note also that the assembly can include a mechanical swage  84  (which can be annular, but is not shown at the top of the drawing). To prevent this swage from contacting the coil  34  on the conductive fiber  68 , an insulative sleeve  86  preferably is included, lining the hole in which the lower assembly is made. The device of  FIG. 5  retains the fiber lead  68  while allowing electrical connection to the fiber lead  66 . The fiber lead  68  may be connected to an electrode or other connection distally or proximally of the pass through connector  65 . Note also, the non-connected fiber lead  68  could terminate at the device  65 , ending therein, in a case where retention of the pair together is desired. 
         [0037]      FIG. 6  shows a four conductor lead end connector  90  schematically, in cross section. This connector has a pin connector  92  at its end and three separate connection rings  94 ,  96  and  98  at its outer surface, each insulated from the others and from the pin connector  92 . Each of four conductive fiber leads  100 ,  102 ,  104  and  106  is covered with an insulating tube  108  up to the point where it makes electrical connection with the respective conductive ring  94 ,  96 ,  98  or, in the case of the pin connector,  110 . Insulation between adjacent conductive portions is shown at  112 ,  114  and  116 . The positions of the fibers  100 ,  102 ,  104  and  106 , although appearing to be within one plane within the cylindrically shaped connector body  90 , actually are preferably rotated relative to one another, as schematically indicated at the top of the drawing. 
         [0038]    Each conductive fiber ( 100 ,  102 ,  104 ,  106 ) enters from a bundle or tubular pipe  118 , within which they may be held in respective positions by insulating adhesive material  120 , and extends into the conductive portion within which it is electrically connected. As seen in the drawing, the insulative sleeve or tube  108  insulates the conductive fiber until the point where it enters the conductor, such as  94  or  96 , to which it is connected. Coils  122  can be connected around each fiber end, primarily for the purpose of making a good electrical connection in this case. Conductive adhesive  124  fills space between the coil and the metal of the bore within which the conductive fiber end resides, providing good electrical contact between the fiber and the metal bore and between the coil and the metal bore. 
         [0039]      FIG. 6  shows a weld  125  at the end of the fiber lead  104 , and this can be a glass/metal weld and can further connect the fiber lead to the metal that surrounds the pin connector  92 . Other welds can be used at the ends of the other fiber leads, as indicated. 
         [0040]    Note that the insulating tube or sleeves  108  can provide mechanical strength as well as insulation for each of the conductive fibers.  FIG. 6  also shows a large strain relief coil  126  which can be firmly secured to the connector body and can provide strain relief for a distance away from the connector. 
         [0041]    The strain relief referred to herein, achieved by the coils as discussed above, is a function of allowing some bending of the conductive fibers but restricting that bending to a uniform bending, without any severe bend portions. These strain relieving coils, applied to very fine conductive glass fibers to provide strain relief by preventing sharp bending, such as implanted as electrostimulation leads, in the environment of extremely high cycles of bending, is an important feature of the invention. 
         [0042]    The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.