Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/118,602, filed on Nov. 29, 2008. The disclosure of the above application is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure pertains to medical devices, and more particularly to conductive couplings for medical electrical leads. 
       BACKGROUND 
       [0003]    A medical electrical lead typically includes one or more elongate conductors, each of which electrically couples an electrode of the lead to a corresponding connector contact of the lead. A conductive coupling between a lead conductor and electrode should add a minimum of electrical resistance to the electrical circuit, which is formed by the electrode, conductor, and contact, and should have an adequate strength to maintain good contact under operational loading conditions. 
         [0004]    Because medical electrical leads are typically constructed to have the lowest possible profile, without compromising functional integrity, reliability and durability, relatively low profile conductive couplings, which do not significantly increase a profile of the lead are also desired. Although some low profile conductive couplings have been previously disclosed, there is still a need for improved couplings which, in addition meeting the above criteria, provide flexibility in the manufacture of various configurations of medical electrical leads. 
         [0005]    As lead bodies become smaller and the height of the connections between conductors and electrodes is reduced, it becomes increasing difficult to make low profile junctions that allow conductor coils to be welded to without damaging or significantly affecting the cable. For example, a radially symetrical crimp barrel or crimp sleeve located entirely within a lead lumen as described in U.S. patent application Ser. No. 11/549,284 filed Oct. 13, 2006 may only have a 3 mil wall due to height constraints. The thermal mass, wall thickness and available material to make an effective weld is negligible. Prior designs such as those disclosed in U.S. Pat. No. 5,676,694 issued to Boser et al and incorporated herein by reference in its entirety have provided an extension to the crimp sleeve which extends outward from the lead lumen to the exterior of the lead body, allowing the a weld to an associated electrode coil to be made spaced from the lead conductor. However, further reductions in lead profile are still desirable over leads fabricated using this connector mechanism. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is configured to provide an offset weld and crimp in a coupling component that can be located entirely within a lumen of a lead body. This end is accomplished by providing an asymmetric coupling component is provided with a crimp recess, for example a groove or a bore extending along one side of the component and a thickened portion offset laterally from the groove or bore and having a welding surface displaced laterally from the groove or bore. While the embodiments illustrated herein are those employing a crimping groove, for purposes of understanding the invention it should be understood that a bore may be substituted. In preferred embodiments, the crimp recess is used to receive a stranded or cabled conductor within the lead body and the offset portion is used to attach to one or more filars of an electrode coil by welding thereto. 
         [0007]    The component displays a generally flattened configuration, with a thickness substantially less than its width as measured perpendicular to the crimp groove or bore. This configuration in turn allows the wall thickness and mass in the area of the weld to be significantly increased and moves the weld energy away form the cable while still maintaining a low profile. In order that the component does not add to the diameter of the lead body, it is preferably located in the lead so that the thickened offset portion extends from the groove or bore along either the longitudinal axis or around the circumference of the lead body. The component may also be provided with curved inner or outer surfaces extending across its width to assist in conforming to the typically cylindrical geometry of leads&#39; internal lumens and surfaces. 
         [0008]    The flat geometry and/or curved geometry of the coupling component allows for easy orientation of the component during the welding/assembly. The invention may also comprise an optional recessed region in the offset region of the sleeve. In addition, the electrode wires can be welded together to improve the ability of placing two or more electrode wires in a single recess region. This is particularly effective when attaching flat wire electrode coils to the sleeve. As a further embodiment/option, to aid the cable joining process the inner channel of the sleeve can incorporate an interlock that is engaged when clamping the sleeve on to the cable. This interlock can be useful when the coupling component is fabricated of a material that has spring back (e.g. Titanium). 
         [0009]    In some embodiments, the conductor to which the coupling component is crimped is a cabled conductor extending parallel to the axis of the lead body and the groove or bore extends parallel to the axis of the lead body. In other embodiments, the conductor to which the coupling component is crimped is a coiled conductor having individual coils extending generally transverse to the axis of the lead body the groove or bore correspondingly extends generally transverse to the axis of the lead body. In embodiments in which employ a groove, as disclosed in more detail herein, the groove is defined is defined by first and second arms which define the groove therebetween. 
         [0010]    The electrode preferentially takes the form of an electrode coil mounted around the outer circumference of the lead body and preferably includes a portion or component that component that extends through the outer insulation sidewall of the lead and into the interior lumen or space within the lead that encloses the lead conductor and the coupling component. The weld is thus located entirely within the outer diameter and preferably within the inner diameter of the lead body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The following drawings are illustrative of particular embodiments of the present disclosure and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
           [0012]      FIG. 1  is a plan view of an exemplary medical electrical lead that may include embodiments of the present invention. 
           [0013]      FIG. 2A  is a perspective view of a coupling component, according to some embodiments. 
           [0014]      FIGS. 2B-C  are each a perspective view of a portion of the lead shown in  FIG. 1 , wherein an outer insulation sidewall is cut away to show alternative conductive couplings, according to some alternate embodiments. 
           [0015]      FIG. 2D  is a cross-section view of an exemplary conductor. 
           [0016]      FIG. 3  is a perspective view of a portion of the lead shown in  FIG. 1 , wherein an outer insulation sidewall is cut away to show a conductive coupling, according to yet further embodiments. 
           [0017]      FIGS. 4A-B  are perspective views of coupling components, according to some alternate embodiments. 
           [0018]      FIG. 5  is a cross-section through the lead of  FIG. 1  showing a conductive coupling within an alternative insulative sidewall configuration, according to some alternate embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements employ that which is known to those of skill in the field of the disclosure. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. 
         [0020]      FIG. 1  is a plan view of an exemplary medical electrical lead  100  that may include embodiments of the present invention.  FIG. 1  illustrates lead  100  including an outer insulation sidewall  110  that extends between a proximal portion  116  and a distal portion  117 ; proximal portion  116  includes electrical contact surfaces  12 ,  14  and  15 , which are shown mounted on connector legs of proximal portion  116 ; and distal portion  117  includes electrode surfaces  120 ,  140  and  151 . Dashed lines in  FIG. 1  schematically illustrate conductors  220 ,  240  and  250  which extend within outer insulation sidewall  110  to couple each of electrode surfaces  120 ,  140 ,  151  to a corresponding contact surface  12 ,  14 ,  15 . Thus, lead  100  is a tripolar lead that may provide pacing and sensing, via electrode surfaces  120  and  140 , and defibrillation, via electrode surface  151 . According to some preferred embodiments, conductor  220  is formed as a coil to provide torque transfer between proximal portion  116  and distal portion and to electrically couple electrode surface  120  to contact surface  12 , and conductors  240 ,  250  are each formed as a cable to electrically couple electrode surfaces  140 ,  150  to contact surfaces  14 ,  15 , respectively. According to embodiments described herein, electrode surface  151  is a first portion of an electrode component  150 , and a second portion of electrode component  150  extends within outer insulative sidewall  110  for coupling with conductor  250 . It should be noted that either or both of the components including electrode surfaces  120  and  140  may also include portions which are coupled to the corresponding conductors  220 ,  240  in a manner similar to embodiments described herein. 
         [0021]    Two exemplary lead configurations, or arrangements of conductors  220 ,  240 ,  250  will be described herein (a first in conjunction with  FIGS. 2B-C  and  3 , and a second in conjunction with  FIG. 5 ), but any suitable arrangement of conductors  220 ,  240 ,  250 , within outer insulation sidewall  110 , is within the scope of the present invention. Furthermore, it should be noted, that embodiments are not limited to inclusion in tripolar pacing and defibrillation leads, like lead  100 , and lead  100  is only an exemplary type of lead used for the purpose of illustration. 
         [0022]      FIG. 2A  is a perspective view of a coupling component  225 , according to some embodiments, which may be incorporated into lead  100  to form the coupling between conductor  250  and the aforementioned second portion of electrode component  150 .  FIG. 2A  illustrates coupling component  225 , which is formed from a slug of conductive material, including a first side  211 , a second side  212 , which extends opposite first side  211 , a third side, which extends between first and second sides  211 ,  212 , and a fourth side  214 , which also extends between first and second sides  211 ,  212 , opposite third side  213 .  FIG. 2A  further illustrates component  225  including a continuous bulk  25  of the slug of conductive material, which defines third side  213 , and first and second arms  21 ,  22 , each of which extend over a length L, from continuous bulk  25  to fourth side  214 ; each arm  21 ,  22  is shown having a width W, which is defined between first and second sides  211 ,  212 . According to the illustrated embodiment, a space g between first and second arms  21 ,  22  of component  225  is intended to receive a length of an elongate conductor, for crimping between the arms, for example, conductor  250 , as shown in  FIGS. 2B-C . Although  FIG. 2A  shows length L being approximately the same for both arms  21 ,  22 , it should be noted that, according to alternate embodiments, arms  21 ,  22  extend over different lengths; the differing lengths may facilitate an overlapping of arms  21 ,  22  when conductor is crimped therebetween, according to these alternate embodiments. 
         [0023]      FIGS. 2B-C  are each a perspective view of a portion of lead  100 , generally coinciding with section line A-A of  FIG. 1 , wherein outer insulation sidewall  110  is cut away to show alternative couplings between electrode component  150  and conductor  250 , via coupling component  225 .  FIGS. 2B-C  illustrate conductor  250  extending between an inner insulation sidewall  210  and outer insulation sidewall  110 , and coupling component  225  also located between sidewalls  210 ,  110  to receive a length of conductor  250 , between arms  21 ,  22 , for a crimp joint, and to receive a second portion  152  of electrode component  150  over a surface  20  thereof for a weld joint. Although not shown, it should be appreciated that conductor  220 , which couples electrode surface  120  to contact surface  12  ( FIG. 1 ), extends within inner insulation sidewall  210 . Conductor  240  is also not shown, for the purpose of clarity in the illustration of the coupling; but, it should be appreciated that conductor  240  also extends between inner insulation sidewall  210  and outer insulation sidewall  110  to couple electrode surface  140  to contact surface  14 . Dashed lines in  FIGS. 2B-C  illustrate an optional extension of conductor  250  beneath first portion  151  of electrode component  150 , beyond the crimped junction with component  225 , for example, to another junction with electrode component  150 , at an opposite end thereof, according to some embodiments. 
         [0024]    According to the embodiments of  FIGS. 2B-C , a length of conductor  250 , about which arms  21 ,  22  are crimped, extends along width W of arms  21 ,  22  and, generally, in a direction of a longitudinal axis  11  of lead  100 . Conductor  250  may include a 1×19 cable configured from a plurality of wire strands, for example, formed from MP35N alloy, which is known to those skilled in the art; a cross-section view of conductor  250  including such a cable is shown in  FIG. 2D . Silver cored MP35N may also be employed. This present invention is even more important in this context as silver has lower melting point. The conductor wires may alternatively can be cable or solid conductors such as Ta or Ag cored MP35N.  FIG. 2D  illustrates cable  290  surrounded by an insulative jacket  295 , for example, formed from a fluoropolymer, such as PTFE or ETFE; a portion of jacket  295  is removed from about cable  290 , along the length of conductor  250  which is crimped between arms  21 ,  22 , either prior to, or during the formation of the crimp.  FIG. 2D  further illustrates cable  290  made up of a plurality of wire strands  209 , for example, each having a diameter between approximately 0.0005 inch and approximately 0.005 inch; strands  210  may be stranded with a pitch between approximately 0.3 inch and 0.6 inch. Another exemplary cable, that may form conductor  250 , is known as a 7×7 cable, which includes seven cabled bundles of seven wire strands, and is described in commonly-assigned U.S. Pat. No. 5,760,341, which is hereby incorporated by reference. 
         [0025]    According to some embodiments, width W of arms is at least approximately 0.02 inch, and, if a diameter of conductor  250  is approximately 0.006 inch (with insulative jacket  295  removed for the coupling), the space g between arms  21 ,  22  is approximately 0.008 inch and a length L over which arms  21 ,  22  extend is at least approximately 0.01 inch. A length of arms  21 ,  22  may be such that ends of arms do not overlap when the arms are crimped about the conductor, for example, by confronting crimp heads that indent arms  21 ,  22  on either side of conductor  250 ; but, according to alternate embodiments, for example, as will be describe below in conjunction with  FIG. 3 , a length of arms  21 ,  22  is such that one of arms overlaps the other when crimped. 
         [0026]    With further reference to  FIGS. 2A-C , a surface  20  of component  225 , which faces outer insulation sidewall  110 , is intended to receive an overlapping of second portion  152  of electrode component  150 , for welding thereto, for example, via a solid state YAG type laser, known to those skilled in the art.  FIG. 2A  illustrates surface  20  of component  225  including a first part  201 , which extends over continuous bulk  25 , and a second part  202 , which extends over first arm  21 ; a spot weld joint between second portion  152  of electrode component  150  and component  225  is preferably located along first part  201  of surface  20  so that a maximum thickness of conductive material, which is present in continuous bulk  25 , as opposed to in arm  21 , is available to maximize the weld pool for the joint. Locating the weld on first part  201  of surface  20  also helps to offset the weld joint from the crimp joint formed between arms  21 ,  22  and conductor  250 , so that the formation of the two joints are less likely to compromise one another, while still allowing the entire coupling, between electrode component  150  and conductor  250 , to reside beneath outer insulation sidewall  110 . According to embodiments illustrated by  FIG. 2B , second portion  152  of electrode component  150  extends, over first part  201  of surface  20  of component  225 , in a direction transverse to the direction of longitudinal axis  11 ; while, according to embodiments illustrated by  FIG. 2C , second portion  152  extends, over first part  201  of surface  20 , in the general direction of longitudinal axis  11 , similar to the extent of the crimped portion of conductor  250 . 
         [0027]    Suitable materials from which all, or at least second portion  152  of electrode component  150  may be formed include, without limitation, platinum-iridium alloy, tantalum, tantalum alloys, platinum-iridium clad tantalum and platinum-iridium clad tantalum alloys. Corresponding suitable materials from which component  225  may be formed, in order to accommodate laser welding between bulk  25  and second portion  152  of component  225 , include, without limitation, platinum-iridium alloy, tantalum, tantalum alloys, titanium and titanium alloys. According to some preferred embodiments, if space g and length L of arms  21 ,  22  are dimensioned as described above, for conductor  250  as described above, and electrode component  150  is formed by a multi-filar coil, as illustrated, and each filar of the coil has a diameter between approximately 0.005 inch and approximately 0.01 inch, a thickness of bulk  25  (between surface  20  and an opposite surface  20 ′) is between approximately 0.014 inch and approximately 0.02 inch, and an approximate area of first part  201  of surface  20  is the product of width W, which ranges from approximately 0.02 inch to approximately 0.06 inch, and a depth D, which ranges from approximately 0.01 inch to approximately 0.02 inch ( FIG. 2A ). Dimensions may correspondingly be reduced if smaller conductor cables are used. According to some alternate embodiments, electrode component  150  is a coil formed from a single filar, or wire, for example, having a diameter of between approximately 0.005 inch and approximately 0.01 inch. The single or multiple filars forming electrode component  150 , according to some preferred embodiments, are formed from flattened, or ribbon, wire, rather than round wire; a cross-section of the flattened, or ribbon, wire may be defined by a width that is between approximately 0.005 inch and approximately 0.013 inch and a thickness, or height, that is between approximately 0.002 inch and approximately 0.005 inch. 
         [0028]      FIG. 3  is a perspective view of a portion of lead  100  ( FIG. 1 ), generally coinciding with section line A-A of  FIG. 1 , wherein outer insulation sidewall  110  is cut away to show a conductive coupling, according to yet further embodiments.  FIG. 3  illustrates an alternative orientation of both component  225  and the length of conductor  250 , which is crimped between arms  21 ,  22  of component  225 . According to the illustrated embodiment, conductor  250  is wound about inner insulation sidewall  210 , and component  225  is oriented such that length L of arms  21 ,  22  extends generally in the direction of longitudinal axis  11  and the length of conductor  250 , which is crimped between arms  21 ,  22 , extends in the general direction of the winding of conductor  250 , which is transverse to longitudinal axis  11 . Although conductor  240  ( FIG. 1 ) is not shown in  FIG. 3 , for the purpose of clarity in the illustration of the coupling, it should be appreciated that conductor  240  may also be wound about inner insulation sidewall  210 , alongside conductor  250 , and extends beneath electrode surface  151 , being routed to a coupling with electrode surface  140  ( FIG. 1 ).  FIG. 3  further illustrates arm  21  overlapping arm  22  in the crimp about conductor  250 , for example, having been formed by bending, either as an alternative to, or in addition to indenting, as described above. 
         [0029]      FIG. 4A  is a perspective view of a coupling component  325 , according to some alternate embodiments, which may be employed, as a substitute for component  225 , in the embodiments illustrated by  FIGS. 2B-C  and  3 . It should be noted that suitable materials and dimensions for coupling component  325  may be the same as previously described for component  225 .  FIG. 4A  illustrates coupling component  325  including the four sides  211 ,  212 ,  213 ,  214 , the two arms  21 ,  22 , and the continuous bulk  25 , as previously described, such that component  325  has the same general form as component  225 .  FIG. 4A  further illustrates a surface  30  of component  325  including a first portion  301 , which extends over continuous bulk  25 , a second portion  302 , which extends over arm  21 , and a groove  315 , which is formed in first part  301  of surface  30  and extends orthogonally with respect to length L over which arms  21 ,  22  extend. According to the illustrated embodiment, groove  315  is located to receive one or both filars of second portion  152  of electrode component  150 , so as to provide a positively identified position for second portion  152 , for repeatability of welding, from one coupling to the next; and, according to some embodiments, groove  315  may be sized to be a friction fit about second portion  152 , to further hold portion  152  in place for welding. 
         [0030]    Dashed lines in  FIG. 4A  illustrate multiple alternate and/or additional locations and orientations for grooves, according to alternate embodiments of component  325 . According to some alternate embodiments, component  325  includes an additional groove, which extends alongside groove  315 , so that each filar of second portion  152  of electrode component  150  can extend in an independent corresponding groove. According to some further alternate embodiments, component  325  includes one or more grooves that extend at an angle less than 90 degrees with respect to length L over which arms  21 ,  22  extend. In order to make embodiments of component  325  less sensitive to orientation, and thereby increase manufacturing flexibility, a duplicate groove or set of grooves may be formed in a first part  301 ″ of a surface  30 ″ of component  325 , which surface  30 ″ is opposite surface  30 . 
         [0031]      FIG. 4B  is a perspective view of a coupling component  425 , according to yet further alternate embodiments, which may also be employed, as a substitute for component  225 , in the embodiments illustrated by  FIGS. 2B-C  and  3 . It should be noted that suitable materials and dimensions for coupling component  425  may be the same as previously described for component  225 .  FIG. 4B  illustrates coupling component  425  including the four sides  211 ,  212 ,  213 ,  214  and the continuous bulk  25 , as previously described for component  225 ; in contrast to component  225 , a first arm  41  of component  425  includes a terminal end  411  that extends toward a second arm  42  of component  425 , and second arm  42  includes a terminal end  412  that extends toward first arm  41 .  FIG. 4B  further illustrates each of terminal ends  411 ,  412  including an interlocking feature, so that arms  41 ,  42  mate together when crimped about a conductor, for example, conductor  250 , as illustrated in  FIG. 5 . Like coupling components  225  and  325 , component  425  includes continuous bulk  25  defining third side  213  and from which arms  41  and  42  extend; a surface  40  of coupling component includes a first part  401 , which extends over continuous bulk  25 , and a second part  402 , which extends over first arm  41 . According to the illustrated embodiment, and similar to the previously described embodiments, a spot weld joint between second portion  152  of electrode component  150  and component  425  is preferably located along first part  401  of surface  40  so that a maximum thickness of conductive material, which is present in continuous bulk  25 , as opposed to in arm  41 , is available to maximize the weld pool for the joint; such a joint is illustrated in  FIG. 5 . 
         [0032]      FIG. 5  is a cross-section through medical electrical lead  100 , at section line A-A of  FIG. 1 , showing a conductive coupling within an alternative insulative sidewall configuration, according to some alternate embodiments.  FIG. 5  illustrates an inner insulative sidewall  510  of lead  100  being integral with outer insulative sidewall  110  in a multi-lumen tube configuration, wherein sidewalls  110  and  510  together form a first lumen  501 , in which conductor  220  extends, a second lumen  502 , in which conductor  240  extends, and a third lumen  503 , in which conductor  250  extends.  FIG. 5  further illustrates, a conductive coupling between conductor  250  and electrode component  150  located in third lumen  503 ; the illustrated coupling is formed by interlocking arms  41 ,  42  of coupling component  425  crimped about a length of conductor  250  and by a weld joint formed between second portion  152  of electrode component  150  and continuous bulk  25  of coupling component  425 . 
         [0033]    In the foregoing detailed description, specific embodiments have been described. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims.

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