Patent Publication Number: US-2016235993-A1

Title: Insulated electrical connection in an implantable medical device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/785,143, filed on May 21, 2010, the contents of which are hereby incorporated by reference herein. This application is also a continuation-in-part of U.S. application Ser. No. 13/063,435, filed on Mar. 10, 2011, which is a National Stage Application of International Patent Application No. PCT/AU2009/001185, filed on Sep. 10, 2009, which claims priority to Australian Provisional Patent Application No. 2008904717, filed on Sep. 10, 2008, and Australian Provisional Patent Application No. 2008904715, filed on Sep. 10, 2008, the contents of which are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to the formation of an implantable insulated electrical connection, and more particularly, to an implantable insulated lead connector for electrically connecting lead(s) in an implantable medical device. 
     2. Related Art 
     Medical devices having one or more implantable components, generally referred to herein as implantable medical devices, have provided a wide range of therapeutic benefits to patients (sometimes referred to herein as recipients) over recent decades. Included among implantable medical devices are active implantable medical devices (AIMDs), which are medical devices having one or more implantable components that rely for their functioning upon a source of power other than the human body or gravity, such as an electrical energy source. AIMDs often include an implantable, hermetically sealed electronics module, and a device that interfaces with a patient&#39;s tissue, sometimes referred to as a tissue interface. The tissue interface may include, for example, one or more instruments, apparatuses, sensors or other functional components that are permanently or temporarily implanted in a patient. The tissue interface is used to, for example, diagnose, monitor, and/or treat a disease or injury, or to modify a patient&#39;s anatomy or to modify a physiological process of a patient. 
     For example, an AIMD tissue interface may include one or more conductive electrical contacts, referred to as electrode contacts, which deliver electrical stimulation signals to, or receive signals from, a patient&#39;s tissue. The electrodes are typically disposed in a biocompatible electrically non-conductive carrier, and are electrically connected to the electronics module. The electrodes and the non-conductive member are collectively referred to herein as an electrode assembly. 
     An implantable medical device may also include multiple separate device components electrically connected to one another by leads. Leads extending between device components may be implanted along with the device components, and these leads may become damaged over time and require repair. 
     SUMMARY 
     In one aspect of the present invention, an implantable medical device for implantation in a recipient&#39;s body is disclosed. The implantable medical device comprises first and second elongate leads electrically connected to first and second device components of the implantable medical device, respectively, a conductor connector electrically connecting a distal end of the first lead to a distal end of the second lead, and, an impervious encasement insulating the conductor connector. The impervious encasement comprises a sleeve circumferentially surrounding and spaced from the conductor connector, and an insulative material filling the space between the conductor connector and the sleeve. 
     In another aspect of the present invention, a kit for connecting leads of implantable medical device components, comprising first and second implantable components having first and second leads, respectively, is disclosed. The kit comprises a conductor connector configured to electrically connect distal ends of the first and second leads, a sleeve physically separate from and positionable around the conductor connector so as to form a space between the conductor connector and the sleeve, and a fluent insulative material configured to substantially fill the space and to conform around the conductor connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described herein with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates an exemplary cochlear implant in which aspects of the present invention may be implemented; 
         FIG. 2A  is a perspective view of a portion of an exemplary internal component assembly of a cochlear implant, and a supplementary component that may be connected to the internal component assembly via embodiments of the present invention; 
         FIG. 2B  is a perspective view of an internal component assembly of  FIG. 2A  electrically connected to the supplementary component of  FIG. 2A  via an implantable insulated lead connector in accordance with embodiments of the present invention; 
         FIG. 2C  is a perspective view of a portion of an exemplary internal component assembly of a cochlear implant in which embodiments of the present invention may be advantageously implemented; 
         FIG. 2D  is a perspective view of a portion of an exemplary internal component assembly of a cochlear implant having a helixed lead, in which embodiments of the present invention may be advantageously implemented; 
         FIG. 2E  is a more detailed perspective view of an unhelixed region of the helixed lead illustrated in  FIG. 2D ; 
         FIGS. 3A-3D  are side views illustrating an exemplary process for connecting leads of respective device components of an implantable medical device using an implantable insulated lead connector in accordance with embodiments of the present invention; 
         FIG. 3E  is a perspective view of a longitudinally split sleeve of an implantable insulated lead connector in accordance with embodiments of the present invention; 
         FIGS. 4A-4D  are side views illustrating an exemplary process for connecting leads of respective device components of an implantable medical device using an implantable insulated lead connector in accordance with another embodiment of the present invention; 
         FIG. 4E  is a cross-sectional view of the implantable insulated lead connector of  FIG. 4D ; 
         FIG. 5A  is a cross-sectional view of portions of an implantable insulated lead connector configured to form multiple electrical connections between leads of respective device components of an implantable medical device, in accordance with embodiments of the present invention; 
         FIGS. 5B-5E  are side views illustrating an exemplary process for connecting leads of respective device components of an implantable medical device using the implantable insulated lead connector of  FIG. 5A  in accordance with embodiments of the present invention; 
         FIG. 6A  is a perspective view of components of an implantable insulated lead connector, in accordance with embodiments of the present invention; 
         FIG. 6B  is a cross-sectional view of components of an implantable insulated lead connector, in accordance with embodiments of the present invention; 
         FIG. 6C  is a side view of an implantable insulated lead connector, in accordance with embodiments of the present invention; 
         FIGS. 7A-7C  are side views illustrating an exemplary process for connecting leads of respective device components of an implantable medical device using an implantable insulated lead connector, in accordance with embodiments of the present invention; and 
         FIGS. 8A-8C  are side views illustrating an exemplary process for connecting leads of respective device components of an implantable medical device using an implantable insulated lead connector, in accordance with other embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present invention are generally directed to an implantable insulated lead connector that electrically connects components of an implantable medical device. The implantable insulated lead connector comprises a conductor connector electrically connecting conductors of two leads, and an impervious encasement formed around the conductor connector. The impervious encasement is formed by a sleeve positioned around the conductor connector and a fluent insulative material conformed around the conductor connector in a space between the conductor connector and the sleeve. Advantageously, the impervious encasement substantially prevents the ingress of body fluid and tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue from the conductor connector out of the impervious encasement, and thereby insulates the conductor connector. In certain embodiments of the present invention, the insulative material utilized to form the impervious encasement may be a curable insulative material. In such embodiments, after filling the space between the conductor connector and the sleeve with the curable insulative material, the curable insulative material may be cured in situ (e.g., cured at or proximal to the site of implantation of the implantable insulated lead connector). 
     Implantable insulated lead connectors in accordance with embodiments of the present invention provide electrical connections having superior reliability and efficiency by substantially preventing the ingress of body fluid and tissue. For example, by insulating the conductor connector with the impervious encasement, embodiments of the implantable insulated lead connector may reduce leakage current and power loss at the site of an electrical connection relative to conventional connectors that attempt to seal a potential pathway for body fluid and tissue via the compression of separate device components against one another. 
     Exemplary embodiments of the present invention are described herein with reference to one type of implantable medical device, namely, a cochlear implant. It would be appreciated that an implantable insulated lead connector in accordance with embodiments of the present invention may be used in other implantable medical devices. For example, implantable devices in which embodiments of the present invention may be implemented include, but are not limited to, implantable medical devices such as neural stimulators, pacemakers, fluid pumps, sensors, drug delivery systems, other prosthetic hearing devices, etc. It would also be appreciated that an implantable insulated lead connector in accordance with embodiments of the present invention may be used to connect a variety of different device components. For example, embodiments of the implantable insulated lead connector may be used to connect an auxiliary power source or a microphone to another device component. 
       FIG. 1  illustrates an exemplary cochlear implant in which aspects of the present invention may be implemented. In a fully functional human hearing anatomy, outer ear  101  comprises an auricle  105  and an ear canal  106 . A sound wave or acoustic pressure  107  is collected by auricle  105  and channeled into and through ear canal  106 . Disposed across the distal end of ear canal  106  is a tympanic membrane  104  which vibrates in response to acoustic wave  107 . This vibration is coupled to oval window or fenestra ovalis  110  through three bones of middle ear  102 , collectively referred to as the ossicles  111  and comprising the malleus  112 , the incus  113  and the stapes  114 . Bones  112 ,  113  and  114  of middle ear  102  serve to filter and amplify acoustic wave  107 , causing oval window  110  to articulate, or vibrate. Such vibration sets up waves of fluid motion within cochlea  115 . Such fluid motion, in turn, activates tiny hair cells (not shown) that line the inside of cochlea  115 . Activation of the hair cells causes appropriate nerve impulses to be transferred through the spiral ganglion cells and auditory nerve  116  to the brain (not shown), where they are perceived as sound. In certain profoundly deaf persons, there is an absence or destruction of the hair cells. Cochlear implants, such a cochlear implant  120 , are utilized to directly stimulate the ganglion cells to provide a hearing sensation to the recipient. 
       FIG. 1  also illustrates the positioning of cochlear implant  120  relative to outer ear  101 , middle ear  102  and inner ear  103 . Cochlear implant  120  comprises external component assembly  122  which is directly or indirectly attached to the body of the recipient, and an internal component assembly  124  which is temporarily or permanently implanted in the recipient. External assembly  122  comprises microphone  125  for detecting sound which is output to a behind-the-ear (BTE) speech processing unit  126  that generates coded signals which are provided to an external transmitter unit  128 , along with power from a power source (not shown) such as a battery. External transmitter unit  128  comprises an external coil  130  and, preferably, a magnet (not shown) secured directly or indirectly in external coil  130 . 
     In the cochlear implant embodiment illustrated in  FIG. 1 , internal component assembly  124  comprises an internal coil  132  of a stimulator unit  134  that receives and transmits power and coded signals received from external assembly  122  to other elements of stimulator unit  134  which apply the coded signal to cochlea  115  via an implanted electrode assembly  140 . Connected to stimulator unit  134  is a flexible cable  154 . Flexible cable  154  electrically couples stimulator unit  134  to electrode assembly  140 . Electrode assembly  140  comprises a carrier member  142  having one or more electrodes  150  positioned on an electrode array  146 . Electrode assembly  140  enters cochlea  115  at cochleostomy region  152  and is positioned such that electrodes  150  are substantially aligned with portions of tonotopically-mapped cochlea  115 . Signals generated by stimulator unit  134  are typically applied by the array  146  of electrodes  150  to cochlea  115 , thereby stimulating auditory nerve  116 . 
     Although embodiments of the present invention are described herein with reference to a cochlear implant  120  having external and internal components, it would appreciated that embodiments of the present invention may also be implemented in a totally implantable cochlear implant. In such totally implantable devices, the sound processor and/or the microphone may be implanted in the recipient. Such totally implantable devices are described in, for example, H. P. Zenner et al. “First implantations of a totally implantable electronic hearing system for sensorineural hearing loss”, in HNO Vol. 46, 1998, pp. 844-852; H. Leysieffer et al. “A totally implantable hearing device for the treatment of sensorineural hearing loss: TICA LZ 3001”, in HNO Vol. 46, 1998, pp. 853-863; and H. P. Zenner et al. “Totally implantable hearing device for sensorineural hearing loss”, in The Lancet Vol. 352, No. 9142, page 1751, the contents of which are hereby incorporated by reference herein. 
       FIG. 2A  is a perspective view of a portion of an exemplary internal component assembly  224 A of an implantable medical device, namely a cochlear implant, and a supplementary component  237  that may be connected to the internal component assembly  224 A via embodiments of the present invention. As illustrated in  FIG. 2A , internal component assembly  224 A, which is an embodiment of internal component assembly  124  of  FIG. 1 , comprises a primary component  235  having a lead  254  that extends from primary component  235  to an electrode assembly (not shown), such as electrode assembly  140  of  FIG. 1 . In the illustrative embodiment of  FIG. 2A , primary component  235  is an embodiment of stimulator unit  134  of  FIG. 1  and is fully functional without supplementary component  237 . Primary component  235  is implanted with a lead  270  having a proximal end  275  connected to primary component  235  and a distal end  273  that is not connected to any other module. In the illustrative embodiment of  FIG. 2A , lead  270  is a flying lead, and is completely insulated when implanted with primary component  235 . As used herein, a “flying lead” is a lead that, when implanted, is connected at a first end to an implantable component of an implantable medical device and that is not connected to any other component at a second end. A flying lead may be used to connect a primary component to a supplementary component via a post-manufacture connection procedure utilizing an implantable insulated lead connector in accordance with embodiments of the present invention. 
     Supplementary component  237  of  FIG. 2A  comprises a lead  260  having a proximal end  265  connected to supplementary component  237  and a distal end  263  that is not connected to any other component when manufactured.  FIG. 2B  is a perspective view of an internal component assembly  224 A electrically connected to a supplementary component  237  via an implantable insulated lead connector  299  in accordance with embodiments of the present invention. In the illustrative embodiment of  FIGS. 2A and 2B , flying lead  270  extends from primary component  235  and is not connected to any other component at distal end  273  when initially implanted. During a subsequent surgical procedure to implant supplementary component  237 , primary component  235  is electrically connected to supplementary component  237  by electrically connecting leads  260  and  270  via implantable insulated lead connector  299  in accordance with embodiments of the present invention. 
     In some embodiments of the present invention, supplementary component  237  is an upgrade module. In such embodiments, the upgrade module may be connected to primary component  235  to provide additional functionality to primary component  235 . Providing additional functionality via an upgrade module is advantageous because the additional functionality may be provided without replacing primary component  235  and other components connected to it, such as an electrode assembly, for example. 
     In other embodiments, supplementary component  237  is a repair module. In such embodiments, when a primary component  235  malfunctions, a repair module is connected to primary component  235  to provide internal component assembly  224 A with the capabilities lost due to the malfunction. Providing the lost capabilities via a repair module is advantageous because repairing the cochlear implant may be accomplished without replacing primary component  235  and other components connected to it, and without explanting primary component  235  for repairs. 
     Accordingly, providing one or more flying leads  270  extending from primary component  235  allows internal component assembly  224 A to be upgraded and/or repaired via upgrade and repair modules with less invasive surgery than would be required to replace a complete cochlear implant. Such upgrades and repairs are also less surgically invasive than explanting primary component  235  for repairs or replacing primary component  235  and other components connected to it, such as an electrode assembly. In accordance with embodiments of the present invention, an upgrade or repair module may be connected to a primary component via an implantable insulated lead connector that substantially prevents the ingress of body fluid or tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue out of the connector. 
       FIG. 2C  is a perspective view of a portion of an exemplary internal component assembly  224 C of a cochlear implant, in which embodiments of the present invention may be advantageously implemented. Primary and supplementary components  235  and  237  are similar to those described with regard to  FIGS. 2A and 2B , except that they are electrically connected by a lead  276  when manufactured, and are implanted together. Primary and supplementary components  235  and  237  may be referred to as distributed implantable components of internal component assembly  224 C. In such embodiments, supplementary component  237  may provide additional or redundant functionality to primary component  235 . As described further below, embodiments of the present invention may be advantageous for repairing the connection between primary and supplementary components  235  and  237 . The connection may require repair when, for example, one or more conductors of lead  276  become exposed or a break in lead  276  occurs. Lead  276  may be repaired using an implantable insulated lead connector  299  in accordance with embodiments of the present invention. A lead  276  repaired using implantable insulated lead connector  299  will result in an electrical connection of primary and supplementary components  235  and  237  similar to that shown and described in relation to  FIG. 2B . 
     Alternatively, embodiments of the present invention may be used to connect primary component  235  to a replacement component. For example, to replace supplementary component  237 , lead  276  may be severed and a replacement component may be connected to the portion of lead  276  extending from primary component  235 . More specifically, a lead extending from the replacement module may be electrically connected to the portion of lead  276  extending from primary component  235  using an implantable insulated lead connector  299 , similar to the manner in which leads  260  and  270  are connected via implantable insulated lead connector  299  as illustrated in  FIG. 2B . 
       FIG. 2D  is a perspective view of a portion of another exemplary internal component assembly  224 D of a cochlear implant, in which embodiments of the present invention may be advantageously implemented. Internal component assembly  224 D is similar to internal component assembly  224 C, but includes a helixed lead  277  electrically connecting primary and supplementary components  235  and  237  rather than lead  276 . Helixed lead  277  includes helixed regions  278  and an unhelixed region  279 , which is illustrated in more detail in  FIG. 2E . As will be described further below, when replacing supplementary component  237  with a replacement component unhelixed region  279  provides an advantageous location at which a lead extending from the replacement component may be coupled to lead  277  via an implantable insulated lead connector  299 . 
       FIGS. 3A-3D  are side views illustrating an exemplary process for connecting leads  360  and  370  of respective device components of an implantable medical device using an implantable insulated lead connector  399  in accordance with embodiments of the present invention. As shown in  FIG. 3A , lead  370  includes a conductor  374  partially covered by transparent insulation  372 . In other embodiments, lead  370  may include more than one conductor  374 . In still other embodiments, insulation  372  may be opaque. As illustrated in  FIG. 3A , insulation  372  does not cover conductor  374  at distal end  373  of lead  370 . In some embodiments, lead  370  is a flying lead connected at a proximal end to a primary component  235  of a cochlear implant and manufactured with insulation  372  completely covering conductor  374 . In such embodiments, insulation  372  is stripped from conductor  374  at distal end  373  prior to connecting lead  370  to lead  360 . Insulation  372  may be stripped using any suitable tool, and may be stripped during a surgical procedure to implant the secondary implantable module, for example. In addition, lead  370  may be shortened, if desired, before it is electrically connected to lead  360 . In such embodiments, a distal portion of lead  370  is severed, and insulation  372  is then stripped from conductor  374  at the distal end  373  remaining after shortening lead  370 . 
     As illustrated in  FIG. 3A , lead  360  includes a conductor  364  covered by transparent insulation  362 . In other embodiments, lead  360  may include more than one conductor  364 . In still other embodiments, insulation  362  may be opaque. Lead  360  also comprises a conductor connector for electrically connecting conductors of leads  360  and  370  to thereby electrically connect leads  360  and  370 . In the illustrative embodiment of  FIG. 3A , the conductor connector is a conductive tube  366  having a flared region  365 A and a connection region  368  at which tube  366  is crimped to conductor  364  and thereby electrically connected to conductor  364 . Insulation  362  covers a portion of tube  366 , including connection region  368 . In certain embodiments, a proximal end of lead  360  is connected to a supplementary component  237  (see  FIG. 2A ). In such embodiments, supplementary component  237  may be manufactured with tube  366  forming part of lead  360  so that lead  360  may be connected to another lead without the need for additional preparation of lead  360  (e.g., the stripping of insulation  362 ) prior to electrically connecting lead  360  to another lead. 
     In the illustrative embodiment of  FIG. 3A , a sleeve  380  is positioned around a portion of lead  360  before electrically connecting leads  360  and  370 . Alternatively, sleeve  380  may be positioned around a portion of lead  370  before electrically connecting leads  360  and  370 . In embodiments of the present invention, sleeve  380  may be a sleeve, collar, boot, or the like (collectively and generally referred to as a “sleeve”), and in alternative embodiments may have any suitable shape. In the illustrative embodiment of  FIGS. 3A-3D , sleeve  380  comprises a lumen  386  that extends through sleeve  380 , and external indentations  388  located at both ends of sleeve  380 . Sleeve  380  is configured to be longitudinally displaced (e.g., moved or slid) along leads  360  and  370 , and is formed of a biocompatible material. In certain embodiments, sleeve  380  is formed of a non-conductive material such as silicone. In the embodiment illustrated in  FIG. 3A , sleeve  380  is transparent, which may be beneficial for curing ultraviolet (UV) curable silicone disposed in sleeve  380 . 
       FIG. 3B  is a side perspective view of several components of implantable insulated lead connector  399  after electrically connecting leads  360  and  370 , in accordance with embodiments of the present invention. Referring to  FIGS. 3A and 3B , the portion of conductor  374  exposed at distal end  373  of lead  370  is inserted into tube  366  through flared region  365 A to electrically connect leads  360  and  370 . After the insertion of conductor  374 , a portion of tube  366  (including flared region  365 A) is crimped to form a crimped region  367 . Once crimped region  367  is formed, conductors  364  and  374  are each electrically connected to conductive tube  366 , and as such, leads  360  and  370  are electrically connected by tube  366 . Tube  366  may be crimped using any suitable crimping tool, such as surgical needle holders or forceps. 
     Referring to  FIGS. 3B and 3C , sleeve  380  is longitudinally displaced along lead  360  and onto a portion of lead  370  until it is positioned around and encasing tube  366 . As shown in  FIG. 3C , the diameter of lumen  386  is large enough that, once sleeve  380  is positioned around tube  366 , a space  350  is present between an inner surface of sleeve  380  and an outer surface of tube  366 . In certain embodiments, after sliding sleeve  380  over tube  366 , a distal end  393  of a needle  390  may be inserted through one end of sleeve  380  and into lumen  386 . In other embodiments, while sleeve  380  is positioned such that it is not covering tube  366 , needle  390  may be positioned such that distal end  393  is adjacent or proximal to crimped region  367 . Sleeve  380  may then be longitudinally displaced along lead  360  until it is positioned around tube  366  and distal end  393  of needle  390 . Space  350  disposed within sleeve  380  may then be filled with a insulative material  385 A via needle  390  such that insulative material  385 A occupies substantially all of space  350 . In certain embodiments, insulative material  385 A is a fluent insulative material that is capable of flowing from needle  390  into sleeve  380 . While filling space  350 , insulative material  385 A conforms around tube  366  and other portions of leads  360  and  370  disposed in sleeve  380 . For example, in the illustrative embodiment of  FIGS. 3A-3D , insulative material  385 A will conform around tube  366  and the portion of conductor  374  that is exposed within sleeve  380  prior to filling space  350  with insulative material  385 A. In embodiments of the present invention, insulative material  385 A may be a liquid, a viscous liquid, or a semisoft material such as a paste or gel. 
     In the illustrative embodiment of  FIGS. 3A-3D , insulative material  385 A is dispensed from distal end  393  of needle  390  into lumen  386  of sleeve  380  and retained in space  350  between sleeve  380  and tube  366 . In certain embodiments, insulative material  385 A is a curable insulative material, such as curable silicone. For example, insulative material  385 A may be a type of room-temperature vulcanizing (RTV) silicone. In certain embodiments, insulative material  385 A may be a type of silicone curable by one or more of ultraviolet (UV) light, heat, moisture (such as moisture in the body), etc. In preferred embodiments, insulative material  385 A is curable in situ. As used herein “in situ curable insulative material” is insulative material that is curable via exposure to conditions that will not significantly damage a recipient&#39;s bodily tissue when the insulative material is cured in close proximity to the bodily tissue. In certain applications, it may be necessary to cure the insulative material relatively near a recipient&#39;s bodily tissue. For example, when an implantable insulated lead connector  399  is used to connect leads of device components while at least one of the device components is implanted in a recipient, curable insulative material  385 A may be cured while the implanted component(s) remain implanted in the recipient. In such applications, curable insulative material  385 A is preferably capable of being cured at or in close proximity to a surgical opening in a recipient&#39;s skin without harming the recipient. 
     After filling sleeve  380  and removing needle  390  from lumen  386 , the curable insulative material  385 A is cured using any suitable means in order to form an impervious encasement  384  around tube  366  and to thereby form implantable insulated lead connector  399 . In the illustrative embodiment of  FIG. 3D , implantable insulated lead connector  399  comprises tube  366  and an impervious encasement  384 , which is disposed around tube  366 . Impervious encasement  384  includes sleeve  380  and cured insulative material  385 B. Insulative material  385 A is cured while it is conformed around tube  366  and any other exposed conductors. As such, once insulative material  385 A is cured, there is no passageway between cured insulative material  385 B and lead  360  or  370  for any substantial amount of body fluid or tissue to reach tube  366  or any other conductor covered by cured insulative material  385 B. Accordingly, impervious encasement  384 , which includes cured insulative material  385 B, substantially prevents the ingress of body fluid and tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue from tube  366  out of impervious encasement  384 , and thereby insulates tube  366 . 
     Lumen  386  may be further sealed by securing ends  387  and  389  of sleeve  380  to leads  370  and  360  via sealing elements, such as sutures, O-rings, and/or toroidal springs that will compress ends  387  and  389 . Such sealing elements may be applied so that ends  387  and  389  may resist the entrance of moisture, such as body fluid, into sleeve  380 . In the illustrative embodiment of  FIG. 3D , sutures  396  are applied to indentations  388  located at ends  387  and  389  of sleeve  380  to compress portions of sleeve  380  to secure sleeve  380  to leads  360  and  370 . In the illustrative embodiment of  FIG. 3D , more than one suture is applied to sleeve  380  at each indentation. In other embodiments, sleeve  380  may be secured with more or fewer sutures  396  than the number shown in  FIG. 3D , and may be secured to leads  360  and  370  with a single suture  396  in each indentation  388 . Alternatively, O-rings made from silicone or rubber, for example, may be placed around indentations  388  to further seal lumen  386  (see, e.g.,  FIG. 4D ). Also, in other embodiments, toroidal springs may be placed around indentations  388  to further seal lumen  386  (see, e.g.,  FIG. 6C ). Each of the toroidal springs may have an inner diameter, in an equilibrium or unstretched state, that is smaller than the outer diameter of the lead  360  or  370  and/or the indentation  388  around which it is to be placed so that the toroidal spring compresses sleeve  380  to the lead  360  or  370  when placed around indentation  388 . 
     In the illustrative embodiment of  FIG. 3D , sutures  396  are applied after curing insulative material  385 A. In other embodiments, a sealing element may be provided at end  389  prior to filling lumen  386  with insulative material  385 A to resist the movement of insulative material  385 A out of end  389  before insulative material  385 A is cured. In such embodiments, a sealing element may also be provided around end  387  once lumen  386  is filled with insulative material  385 A to resist the movement of insulative material  385 A out of lumen  386  prior to curing. 
     Alternatively, one or more ends of sleeve  380  may be self-sealing. As used herein, an end of a sleeve is “self-sealing” when the end provides a seal around a lead extending through it without the assistance of any additional devices or mechanisms. An example of a self-sealing end is shown in  FIG. 4E . As illustrated, the inner diameter of sleeve  480  near end  489  is small enough to provide a seal around lead  460  via a friction or interference fit. 
     In the illustrative embodiment of  FIG. 3D , neither of ends  387  and  389  is self-sealing. In other embodiments, end  389  is self-sealing while end  387  is not. In such embodiments, self-sealing end  389  resists the movement of insulative material  385 A out of end  389  prior to curing while leading end  387  allows needle  390  to be readily inserted into lumen  386 . After filling lumen  386  with insulative material  385 A, end  387  may be sealed using a sealing element as described above, if desired. In other embodiments, both ends  387  and  389  are self-sealing. In such embodiments, needle  390  may be inserted under the seal of end  387 , which will resume its seal around lead  370  when needle  390  is removed to resist the movement of insulative material  385 A out of lumen  386 . Alternatively, in some embodiments, when ends  387  and  389  are both self-sealing, sleeve  380  comprises a one-way valve (not shown) that allows insulative material  385 A to be provided into lumen  386  but resists the movement of insulative material  385 A out of the valve. In the illustrated embodiment of  FIGS. 3A-3E , the encasing element is a sleeve  380 . However, the encasing element may have any suitable shape, and is not limited to the shape of sleeve  380 , or any other sleeve. 
     In certain embodiments, lead  360  is an embodiment of lead  260  of  FIG. 2A , lead  370  is an embodiment of flying lead  270  of  FIG. 2A , and implantable insulated lead connector  399  is an embodiment of implantable insulated lead connector  299 . In alternative embodiments, an implantable insulated lead connector  399  may be used to connect internal component assembly  224 D of  FIG. 2D  with a replacement component. As illustrated in  FIG. 2D , internal component assembly  224 D includes a helixed lead  277 , having helixed and unhelixed regions  278  and  279 , electrically connecting primary and supplementary components  235  and  237 . In certain embodiments, supplementary component  237  may be replaced with a replacement component having a lead  360  substantially similar to lead  360  of  FIGS. 3A-3D . To replace supplementary component  237  with the replacement component, helixed lead  277  is severed at unhelixed region  279 , with a portion of helixed lead  277  remaining connected to primary component  235 . Insulation is then stripped from one or more conductors  274  at unhelixed region  279  and subsequently inserted into a tube  366  of lead  360  connected to the replacement component. Conductors  274  are then crimped within tube  366 . The formation of an implantable insulated lead connector  399  may then be completed as described above in relation to  FIGS. 3B-3D . 
     In the illustrative embodiment of  FIG. 2E , helixed lead  277  comprises multiple conductors  274 . In other embodiments, helixed lead may comprise a single conductor  274 . When helixed lead  277  comprises a single conductor  274  (e.g., a single-core conductor  274 ) or a plurality of electrically connected conductors  274  (e.g., a multi-core conductor  274 ), an implantable insulated lead conductor  399  in accordance with embodiments of the invention may be used to connect helixed lead  277  to a lead extending from the replacement component. When helixed lead  277  comprises a plurality of electrically isolated conductors  274 , an insulated lead conductor  599  (described below in relation to  FIGS. 5A-5E ) in accordance with embodiments of the invention may be used to connect helixed lead  277  to a lead extending from the replacement component and also having a plurality of electrically isolated conductors. Providing an unhelixed region facilitates the severing of helixed lead  277 , the stripping of conductor(s)  274 , and the insertion of conductor(s)  274  into conductive tube(s). Additionally, when helixed lead  277  comprises a plurality of electrically isolated conductors, unhelixed region  279  provides a region in which conductors  274  may be organized to facilitate connection via an implantable insulated lead connector  599 . For example, in the illustrative embodiment of  FIG. 2E , conductors  274  are arranged side-by-side in unhelixed region  279 . In certain embodiments, this arrangement will facilitate insertion of the conductors into respective tubes  566  when connecting helixed lead  277  to a lead  570  of a replacement component. 
       FIG. 3E  is a perspective view of a longitudinally split sleeve of an implantable insulated lead connector in accordance with embodiments of the present invention. Longitudinally split sleeve  382  is similar to sleeve  380  shown and described in relation to  FIGS. 3A-3D , except that sleeve  382  is split into two longitudinal sleeve sections  381  and  383  configured to mate to thereby form sleeve  382  having a lumen  386  (see  FIG. 3C ). That is, a lumen  386  is formed between sleeve sections  381  and  383  when they are mated. In some embodiments of the present invention, sleeve  382  may be used to form an implantable insulated lead connector  399  instead of sleeve  380 . In such embodiments, after crimping tube  366  to conductor  374  to electrically connect leads  360  and  370 , longitudinal sleeve sections  381  and  383  are mated around tube  366  such that tube  366  is encased in a lumen  386 . The diameter of lumen  386  is large enough that, once sleeve  382  is positioned around tube  366 , a space  350  is present between an inner surface of sleeve  382  and an outer surface of tube  366 . Longitudinal sleeve sections  381  and  383  may then be secured together using sealing elements, such as sutures, O-rings, and/or toroidal springs. In certain embodiments, the sealing elements may be applied at ends  387  and  389  of sleeve  382  (see  FIG. 3C ). After longitudinal sleeve sections  381  and  383  are secured together, an implantable insulated lead connector  399  may be completed as described above with reference to  FIGS. 3C and 3D . A longitudinally split sleeve may also be used in other implantable insulated lead connectors in accordance with embodiments of the present invention. 
       FIGS. 4A-4D  are side views illustrating an exemplary process for connecting leads  460  and  470  of respective device components of an implantable medical device using an implantable insulated lead connector  499  in accordance with embodiments of the present invention.  FIG. 4E  is a cross-sectional view of implantable insulated lead connector  499  of  FIG. 4D . In certain embodiments, lead  470  is a flying lead that is implanted with insulation  472  completely covering conductor  474 , and lead  460  is manufactured with insulation  462  completely covering conductor  464 . In the illustrative embodiment of  FIGS. 4A-4E , prior to connecting leads  460  and  470 , insulation  462  is stripped from conductor  464  at distal end  463  and insulation  472  is stripped from conductor  474  at distal end  473 . 
     As illustrated in  FIG. 4A , a sleeve  480  is positioned around a portion of lead  460 . Sleeve  480  is similar to sleeve  380 , except that sleeve  480  is opaque and is self-sealing at ends  487  and  489 . In alternative embodiments, sleeve  480  may be transparent, and one or both of ends  487  and  489  may not be self-sealing. Referring to  FIGS. 4A and 4B , once the insulation has been stripped from conductors  464  and  474 , the exposed portions of conductors  464  and  474  may be inserted into a conductor connector. In the illustrative embodiment of  FIGS. 4A-4E , the conductor connector is a conductive tube  466  comprising flared ends  465 A and  465 B. The exposed portions of conductors  464  and  474  are be inserted into flared ends  465 A and  465 B of tube  466 , respectively, as illustrated in  FIG. 4B . 
     Referring to  FIG. 4C , a portion of tube  466  may be crimped to conductor  464  to form a crimped region  467 A and another portion of tube  466  may be crimped to conductor  474  to form a crimped region  467 B. Once conductive tube  466  is crimped to conductors  464  and  474 , conductors  464  and  474  are electrically connected via conductive tube  466 . Sleeve  480  is then longitudinally displaced along lead  460  until it is positioned around and encasing tube  466 . As shown in  FIG. 4E , the diameter of a lumen  486  of sleeve  480  is large enough that, once sleeve  480  is positioned around tube  466 , a space  450  is present an inner surface of sleeve  480  and an outer surface of tube  466 . Space  450  disposed within sleeve  480  is then filled with an insulative material, such as one of the insulative materials described above in relation to the embodiment of  FIGS. 3A-3D . While filling space  450 , the insulative material conforms around tube  466  and other portions of leads  460  and  470  disposed in sleeve  380 . As described above, the insulative material may be a curable insulative material.  FIG. 4E  is a cross-sectional view of implantable insulated lead connector  499  of  FIG. 4D . Referring to  FIG. 4E , when a curable insulative material is used, the curable insulative material is then cured to form an impervious encasement  484  around tube  466  to thereby form implantable insulated lead connector  499 . Implantable insulated lead connector  499  comprises tube  466  and impervious encasement  484 . Impervious encasement  484  includes sleeve  480  and cured insulative material  385 B. Impervious encasement  484  is similar to impervious encasement  384  described above in relation to  FIGS. 3A-3E . 
     After curing the insulative material, ends  487  and  489  of sleeve  480  may be secured to leads  460  and  470  via sealing elements such as sutures, O-rings, and/or torodial springs, as described above in relation to  FIGS. 3A-3E . Application of the sealing elements may further seal lumen  486 . In the illustrative embodiment of  FIG. 4D , O-rings  497  are applied to sleeve  480  at indentations  488 . As described above, ends  487  and  489  of sleeve  480  are self-sealing. However, one or more sealing elements may additionally be applied to sleeve  480  to further resist the movement of material from the implanted environment (e.g., bodily fluid and tissue) into sleeve  480 . 
     As illustrated in  FIG. 4E , ends  487  and  489  of sleeve  480  are self-sealing and form a friction or interference fit with leads  470  and  460 , respectively. As illustrated, an inner diameter of sleeve  480  at end  489  is smaller than an outer diameter of lead  460  so that end  489  will form an interference fit with lead  460 . Similarly, an inner diameter of sleeve  480  at end  487  is smaller than an outer diameter of lead  470  so that end  487  will form an interference fit with lead  470 . Cured insulative material  385 B is illustrated schematically via small dots in  FIG. 4E . Cured insulative material  385 B substantially fills space  450 , is conformed to tube  466 , and substantially prevents the ingress of body fluid and tissue. 
     Implantable insulated lead connector  499  may be used to replace supplementary component  237  of an implanted internal component assembly  224 C. In an exemplary embodiment, after surgically accessing supplementary component  237  and lead  276 , lead  276  may be severed and supplementary component  237  may be explanted. Subsequently, a new supplementary component may be implanted, and a lead extending from the new supplementary component may be connected to the portion of lead  276  connected to primary component  235  substantially as described above in relation to  FIGS. 4A-4E . Alternatively, in certain embodiments, the new supplementary component includes a lead similar to lead  360 , and the new supplementary component may be connected to the portion of lead  276  connected to primary component  235  substantially as described above in relation to  FIGS. 3A-3D . 
     In the embodiments described above in relation to  FIGS. 4A-4E , conductors  464  and  474  are inserted into a conductive tube  466  to electrically connect leads  460  and  470 . In alternative embodiments, a conductive pin may be attached to one or more of conductors  464  and  474  to facilitate the electrical connection of leads  460  and  470 . For example, in certain embodiments, after stripping insulation from distal ends  463  and  473  of leads  460  and  470 , a conductive pin is attached to each of the exposed conductors  464  and  474 . The pins may be attached to the conductors using any suitable method, such as adhesives, welding, crimping, etc. Once attached, the pins are inserted into flared ends  465 A and tube  466  is then crimped around the pins. In other embodiments, a pin is attached to conductor(s) of only one of leads  460  and  470 . Additionally, in some embodiments, a lead may be manufactured with a conductive pin extending from the distal end of the lead. For example, in embodiments in which implantable insulated lead connector  499  is used to connect a primary component to a supplementary component, as described above in relation to  FIGS. 2A and 2B , lead  460  of the supplementary component may be manufactured with a conductive pin electrically connected to conductor(s)  464  and disposed at distal end  463  to simplify the electrical connection of lead  460  and  470 . In such embodiments, the pin may be inserted into tube  466 , and as such, lead  460  may be electrically connected to tube  466  without the need to first strip insulation  462  from conductor(s)  464 . Additionally, when lead  460  is manufactured with a pin at the distal end, the pin may be partially encapsulated to further secure the pin to the lead and to facilitate handling of the pin. 
     An advantage of embodiments described above in relation to  FIGS. 4A-4E  is that an implantable insulated lead connector  499  may be used to create an encapsulated electrical connection between any two leads, and at nearly any location along either of the leads. Implantable insulated lead connector  499  does not require leads manufactured with any particular connectors, and may even be used to connect leads with incompatible connectors by first severing the incompatible connectors from the distal ends of the leads. Implantable insulated lead connector  499  may also be used to repair a lead extending between device components. 
     Referring to  FIG. 2C , for example, implantable insulated lead connector  499  may be used to repair lead  276 , which electrically connects primary and supplementary components  235  and  237 . Lead  276  may require repair when, for example, one or more conductors of lead  276  becomes exposed, a break in lead  276  occurs, etc. When a complete break has occurred in lead  276 , the portion of lead  276  connected to primary component  235  and the portion of lead  276  connected to supplementary component  237  may be connected via an implantable insulated lead connector  499 , as described above in relation to  FIGS. 4A-4E . Alternatively, if a fault other than a complete break has occurred, then lead  276  may be cut at the site of the fault, or a portion of lead  276  containing the fault may be removed. Thereafter, the portion of lead  276  connected to primary component  235  and the portion of lead  276  connected to supplementary component  237  may be connected via an implantable insulated lead connector  499 , as described above in relation to  FIGS. 4A-4E . Repairing lead  276  in accordance with embodiments of the invention is simpler and less surgically invasive than explanting and replacing internal component assembly  224 C when a lead of internal component assembly  224 C has failed. 
     Additionally, embodiments of implantable insulated lead connector  499  may be used to customize the length of a lead of an implantable medical device. To shorten a lead, for example, a section of the lead may be removed and the remaining portions of the lead may be reconnected using an implantable insulated lead connector  499  in accordance with embodiments of the invention. To lengthen a lead, the lead may be severed and then an additional lead section may be connected between the severed portions of the original lead via two implantable insulated lead connectors  499 . As such, a daisy chain of leads may be created using implantable insulated lead connectors  499  to link the leads together. Similar advantages may be provided by other embodiments described herein in which the leads are first stripped of insulation before being electrically connected. 
       FIG. 5A  is a cross-sectional view of portions of an implantable insulated lead connector  599  configured to form multiple electrical connections between leads of respective device components of an implantable medical device in accordance with embodiments of the present invention.  FIGS. 5B-5E  are side views illustrating an exemplary process for connecting leads  560  and  570  of respective device components of an implantable medical device using an implantable insulated lead connector  599  in accordance with embodiments of the present invention. 
     An exemplary process for connecting multi-conductor leads  560  and  570  via implantable insulated lead connector  599  in accordance with embodiments of the present invention is described below with reference to  FIGS. 5A-5D . In the illustrative embodiment of  FIG. 5A , lead  570  includes conductors  574 A and  574 B, which are partially covered by insulation  572 D. Conductor  574 A is partially covered by insulation  572 A and conductor  574 B is partially covered by insulation  572 B and thus conductors  574 A and  574 B are electrically isolated from one another. As such, in certain embodiments, implantable insulated lead connector  599  is capable of connecting multipolar leads  560  and  570 . In some embodiments, each of conductors  574 A and  574 B is a plurality of conductors. In other embodiments, lead  570  includes three or more conductors electrically isolated from one another. In the illustrative embodiment of  FIG. 5A , lead  570  also includes a lead sleeve  582  having a lumen  584  and an open distal end  588 . Lead sleeve  582  may be longitudinally displaced along lead  570 . 
     In the illustrative embodiment of  FIGS. 5A-5E , lead  570  is a flying lead in which conductors  574 A and  574 B are electrically isolated from the surrounding environment when lead  570  is initially implanted. As shown in  FIG. 5B , for example, lead  570  may be initially implanted with lead sleeve  582  covering conductors  574 A and  574 B, with distal end  588  covered by a removable cover  590 , such as a removable lid or layer of insulation. Referring to  FIGS. 5B and 5C , before electrically connecting leads  560  and  570 , removable cover  590  is removed and lead sleeve  582  is longitudinally displaced away from distal end  573  along lead  570  to expose portions of conductors  574 A and  574 B. Alternatively, lead  570  may be implanted with the portions of conductors  574 A and  574 B disposed at distal end  573  positioned in any suitable insulating sheath, cover, package, or the like (collectively and generally referred to as a “package”). The package is removed prior to electrically connecting leads  560  and  570 . 
     Lead  560  is similar to lead  360  illustrated in  FIGS. 3A-3D , except that lead  560  includes multiple conductors electrically isolated from one another by insulation  562 A and  562 B, and includes a conductor connector electrically connected to each of those conductors. As illustrated in  FIG. 5A , lead  560  includes conductors  564 A and  564 B, which are partially covered by insulation  562 D. Conductor  564 A is partially covered by insulation  562 A and conductor  564 B is partially covered by insulation  562 B and this conductors  564 A and  564 B are electrically isolated from one another. Like lead  570 , in alternative embodiments, lead  560  may include three or more conductors that are isolated from one another. In certain embodiments, each of the electrically isolated conductors is a plurality of conductors. 
     Lead  560  includes a plurality of conductor connectors respectively connected to the electrically isolated conductors of lead  560 . In the illustrative embodiment of  FIG. 5A , the conductor connectors are tubes  566 A and  566 B. Conductor  564 A is electrically connected to conductive tube  566 A having a flared distal end and conductor  564 B is electrically connected to conductive tube  566 B having a flared distal end. Tubes  566 A and  566 B may be crimped to conductors  564 A and  564 B, respectively, and are electrically isolated from one another by insulation  562 C, which covers a portion of tube  566 A. In the illustrative embodiment of  FIG. 5A , the flared ends of tubes  566 A and  566 B are offset from one another. Alternatively, the ends of tubes  566 A and  566 B may be even with one another. 
     Lead  560  also includes a lead sleeve  581  having a lumen  583  and an open distal end  587 . Distal end  587  of lead sleeve  581  is configured to mate with distal end  588  of lead sleeve  582 , and a seal may be formed where distal ends  587  and  588  mate. In the illustrative embodiment of  FIG. 5A , distal ends  587  and  588  have substantially the same diameter. In certain embodiments, lead sleeve  581  is secured to insulation  562 D of lead  560 , and may not be longitudinally displaced along lead  560 . In other embodiments, lead sleeve  581  is not secured to lead  560  may be longitudinally displaced along lead  560 . Each of lead sleeves  581  and  582  is formed of a biocompatible, non-conductive material, such as silicone. In the illustrative embodiment of  FIGS. 5A-5E , lead sleeve  581  is shorter than lead sleeve  582 . In other embodiments, lead sleeve  581  may be longer than lead sleeve  582 , or they may have equal lengths. In certain embodiments, one or both of lead sleeves  581  and  582  are capable of being longitudinally displaced along leads  560  and  570 , respectively. 
     As illustrated in  FIGS. 5A and 5C , insulation  572 D does not cover conductors  574 A and  574 B at distal end  573  of lead  570 . As illustrated in  FIG. 5D , the exposed ends of conductors  574 A and  574 B are inserted into tubes  566 A and  566 B, respectively. More specifically, conductor  574 A is inserted into flared end  569 A of tube  566 A and conductor  574 B is inserted into flared end  569 B of tube  566 B. Tubes  566 A and  566 B are crimped to secure conductors  574 A and  574 B within tubes  566 A and  566 B, respectively, thereby completing the electrical connection of leads  560  and  570 . Specifically, after crimping the conductors within the tubes as described above, conductor  574 A is electrically connected to conductor  564 A via conductive tube  566 A, and conductor  574 B is electrically connected to conductor  564 B via conductive tube  566 B. Tubes  566 A and  566 B may be crimped using any suitable crimping tool, such as surgical needle holders or forceps, as described above with regard to the embodiment of  FIGS. 3A-3D . 
     Referring to  FIG. 5E , after crimping the conductors within the tubes as described above, lead sleeve  582  is longitudinally displaced along lead  570  toward lead sleeve  581  to mate distal end  588  of lead sleeve  582  with distal end  587  of lead sleeve  581  to form a laterally split sleeve  580  around and encasing tubes  566 A and  566 B. In alternative embodiments, lead sleeve  581  may be longitudinally displaced along lead  560  toward lead sleeve  582  to mate lead sleeves  581  and  582 , or both lead sleeves  581  and  582  may be longitudinally displaced toward one another to mate. 
     In certain embodiments, sleeve  580  is sealed where distal ends  587  and  588  mate. For example, distal ends  587  and  588  may be bonded together. In one embodiment, the above bonding is performed by disposing a glue layer on one or more of distal ends  587  and  588  and pressing together distal ends  587  and  588 . Alternatively, a liquid glue may be applied between distal ends  587  and  588 . In one preferred embodiment, the liquid glue sets and/or cures rapidly. In another embodiment, a UV-cured glue is pre-applied to one or more of distal ends  587  and  588 , or is applied as a liquid, or is a separate component that is inserted between distal ends  587  and  588 . In one embodiment, a liquid perfluoropol polymer such as that described in International Application WO 2007/021620 A2 may be utilized. International Application WO 2007/021620 A2 is hereby incorporated by reference herein in its entirety. Other adhesives include, but are not limited to, fibrin glues, cyanoacrylates, polyurethane adhesives, silicone adhesives, and UC-cured acrylics. In another embodiment, chemical surface modification may be utilized to attain a desired bonding. 
     After mating lead sleeves  581  and  582  to form sleeve  580 , tubes  566 A and  566 B are positioned in a lumen  583 ,  584  of sleeve  580 . Lumen  583 ,  584  is large enough that a space  550 A,  550 B is present between an inner surface of sleeve  580  and outer surfaces of tubes  566 A and  566 B. With lead sleeves  581  and  582  mated, space  550 A,  550 B within sleeve  580  is then filled with insulative material as described above in relation to the illustrative embodiment of  FIGS. 3A-3D . While filling space  550 A,  550 B, the insulative material conforms around each of tubes  556 A and  566 B and other portions of leads  560  and  570  disposed in sleeve  580 . As described above, the insulative material may be a curable insulative material. When a curable insulative material is used, the curable insulative material is then cured using any suitable means to form an impervious encasement  584  around tubes  566 A and  566 B to thereby form an implantable insulated lead connector  599 . Implantable insulated lead connector  599  comprises tubes  566 A and  566 B, and impervious encasement  584 . Impervious encasement  584  includes sleeve  580  and cured insulative material  385 B (see, e.g.,  FIG. 4E ) filling space  550 A,  550 B. As described above in relation to impervious encasement  384 , impervious encasement  584  substantially prevents the ingress of body fluid and tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue from tubes  566 A and  566 B out of impervious encasement  584 , and thereby insulates tubes  566 A and  566 B. 
     In preferred embodiments, the insulative material is an in situ curable insulative material, as described above. In certain embodiments, one or more of proximal ends  585  and  586  of lead sleeves  581  and  582  are self-sealing. Additionally or alternatively, proximal ends  585  and  586  may be secured to leads  560  and  570  to further seal lumen  583 ,  584  using sealing elements such as sutures, O-rings, and/or toroidal springs, as described above. 
       FIGS. 6A-6C  illustrate an exemplary process for connecting leads  660  and  670  of respective device components of an implantable medical device using an implantable insulated lead connector  699  in accordance with embodiments of the present invention.  FIG. 6A  is a perspective view of components of an implantable insulated lead connector  699  in accordance with embodiments of the present invention. 
     An exemplary process for connecting leads  660  and  670  via an implantable insulated lead connector  699  in accordance with embodiments of the present invention will be described below with reference to  FIGS. 6A-6C . In the illustrative embodiment of  FIG. 6A , lead  670  includes a conductor  674  covered by insulation  672 . In other embodiments, lead  670  may include more than one conductor  674 . In certain embodiments, lead  670  is implanted with insulation  672  completely covering conductor  674 . Lead  660  includes a conductor  664  covered by insulation  662  and, in some embodiments, insulation  662  completely covers conductor  674 . In certain embodiments, lead  660  may include more than one conductor  664 . 
     Unlike the embodiments described in relation to  FIGS. 3 and 4 , in the illustrative embodiment of  FIGS. 6A-6C , leads  660  and  670  may be electrically connected without stripping insulation  662  and  672  at distal ends  663  and  673  of leads  660  and  670 . Rather, leads  660  and  670  are electrically connected via an insulation displacement connection (IDC). In the illustrative embodiment of  FIG. 6A , the conductor connector that electrically connects leads  660  and  670  is a blade connector  690  (see  FIG. 6A ) comprising blade connector halves  690 A and  690 B. Blade connector half  690 A includes a plurality of blades, spikes, teeth, or the like (collectively and generally referred to as “blades”)  692 A capable of penetrating insulation  672  and  662  to make contact with conductors  674  and  664 . Similarly, blade connector half  690 B includes a plurality of blades  692 B capable of penetrating insulation  672  and  662  to make contact with conductors  674  and  664 . 
       FIG. 6B  is a cross-sectional view of components of an implantable insulated lead connector  699  in accordance with embodiments of the present invention. Referring to  FIG. 6B , blade connector halves  690 A and  690 B are mated such that blade connector  690  encloses distal ends  663  and  673  of leads  660  and  670 , respectively, within a lumen  686  extending through blade connector  690 . When blade connector  690  is mated around leads  660  and  670 , as illustrated in  FIG. 6B , blades  692 A and  692 B pierce (or otherwise displace) insulation  662  and  672  and make contact with conductors  664  and  674 . In certain embodiments, blades  692 A and  692 B are sharp enough to penetrate insulation  692 A and  692 B when blade connector  690  is squeezed by hand to mate blade connector halves  690 A and  690 B around distal ends  663  and  673 . 
     In the illustrative embodiment of  FIGS. 6A-6C , blades  692 A and  692 B are conductive, as are blade connector halves  690 A and  690 B. As such, when blades  692 A and  692 B make contact with conductors  664  and  674 , as shown in  FIG. 6B , conductors  664  and  674  are electrically connected via blades  692 A and the conductive body of blade connector half  690 A, and via blades  692 B and the conductive body of blade connector half  690 B. In the illustrative embodiment of  FIG. 6B , blades  692 A and blade connector half  690 A are unitary, and blades  692 B and blade connector half  690 B are unitary. Alternatively, blades  692 A may be formed separately from blade connector half  690 A and subsequently physically and electrically connected to blade connector half  690 A, and blades  692 B may be formed separately from blade connector half  690 B and subsequently physically and electrically connected to blade connector half  690 B. In other embodiments, instead of blade connector  690 , implantable insulated lead connector  699  may include an insulation displacement connector having at least two conductive screws. In such embodiments, two halves of the insulation displacement connector may be mated such that they enclose distal ends  663  and  673  like blade connector  690 . Once mated, the at least two screws may be operated such that one screw penetrates distal end  663  to contact conductor  664  and the other screw penetrates distal end  673  to contact conductor  674 , to thereby electrically connect leads  660  and  670 . 
       FIG. 6C  is a side view of an implantable insulated lead connector  699  in accordance with embodiments of the present invention. Referring to  FIGS. 6B and 6C , after mating blade connector halves  690 A and  690 B around leads  660  and  670  to electrically connect leads  660  and  670 , a sleeve  380  (as described above in relation to  FIGS. 3A-3D ) is positioned around and encasing blade connector  690 . As shown in  FIG. 6C , the diameter of lumen  386  is large enough that, once sleeve  380  is positioned around blade connector  690 , a space  650  is present between an inner surface of sleeve  380  and an outer surface of blade connector  690 . Space  650  disposed within sleeve  380  is then filled with an insulative material, such as one of the insulative materials described above in relation to  FIGS. 3A-3D . While filling space  650 , the insulative material conforms around blade connector  690  and other portions of leads  660  and  670  disposed in sleeve  380 . As described above, the insulative material may be a curable insulative material. When a curable insulative material is used, after filling space  650  with the curable insulative material, the curable insulative material is cured using any suitable means in order to form an impervious encasement  684  and to thereby form an implantable insulated lead connector  699 . In the illustrative embodiment of  FIG. 6C , implantable insulated lead connector  699 , comprises blade connector  690  and impervious encasement  684 , which is disposed around blade connector  690 . Impervious encasement  684  includes sleeve  380  and cured insulative material  385 B. As described above in relation to impervious encasement  384 , impervious encasement  684  substantially prevents the ingress of body fluid and tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue from blade connector  690  out of impervious encasement  684 , and thereby insulates blade connector  690 . 
     Additionally, in certain embodiments, lumen  386  may be further sealed by securing ends  387  and  389  of sleeve  380  to leads  670  and  660  via sealing elements, such as sutures, O-rings, and/or toroidal springs, as described above. In the illustrative embodiment of  FIG. 6C , toroidal springs  698  are applied to sleeve  380 . Each of toroidal springs  698  has an inner diameter, in an equilibrium or unstretched state, that is smaller than the outer diameter of the lead  660  or  670  and/or indentations  388 . In use, each of toroidal springs  698  is stretched to expand its inner diameter, positioned over one of indentations  388 , and subsequently released so that the toroidal spring compresses sleeve  388  around lead  660  or  670  as it constricts toward its equilibrium or unstretched state. In alternative embodiments, other types of encasing elements my be used instead of sleeve  380 . In accordance with embodiments of the present invention, implantable insulated lead connector  699  may use insulation displacement connectors other than those described above in relation to  FIGS. 6A-6C . 
     Implantable insulated lead connector  699  may be advantageously used to repair a lead extending between device components of an implantable medical device. For example, referring to  FIG. 2B , implantable insulated lead connector  699  may be used to repair lead  276 , which electrically connects primary and supplementary components  235  and  237 . When a complete break has occurred in lead  276 , for example, blade connector  690  may be used to connect the two separate halves of lead  276  and then insulated via an impervious encasement  684 , as shown and described above in relation to  FIGS. 6A-6C . 
     Additionally, if a fault other than a complete break has occurred, then blade connector  690  may be used to bypass the faulty portion of lead  267  by enclosing the fault with blade connector  690  such that a first pair of blades  692 A and  692 B is disposed on one side of the fault and a second pair of blades  692 A and  692 B is disposed on the other side of the fault. Blade connector  690  may then be insulated via an impervious encasement  684 , as shown and described above in relation to  FIGS. 6B-6C . Alternatively, lead  276  may first be cut at the site of the fault, and thereafter blade connector  690  may be used to connect the two separate halves of lead  276 . Blade connector  690  may then be insulated via an impervious encasement  684 , as shown an described above in relation to  FIGS. 6A-6C . In addition, as described in relation to implantable insulated lead connector  499 , implantable insulated lead connector  699  may be used to create an electrical connection between any two leads, and at nearly any location along either of the leads, and may be also used to customize the length of a lead of an implantable medical device. 
       FIGS. 7A-7C  are side views illustrating an exemplary process for connecting leads  760  and  770  of respective device components of an implantable medical device using an implantable insulated lead connector  799  in accordance with embodiments of the present invention. An exemplary process for connecting leads  760  and  770  via an implantable insulated lead connector  799  in accordance with embodiments of the present invention will be described below with reference to  FIGS. 7A-7C . Lead  760  comprises a conductor  764  partially covered by insulation  762 , and lead  770  comprises a conductor  774  partially covered by insulation  772 . In certain embodiments, lead  770  is a flying lead that is implanted with insulation  772  completely covering conductor  774 . As shown in  FIG. 7A , insulation  772  is stripped from conductor  774  at distal end  773  prior to connecting lead  770  to lead  760 . In certain embodiments, lead  760  is manufactured with insulation  762  completely covering conductor  764 . In such embodiments, insulation  762  is stripped from conductor  764  at distal end  763  prior to connecting lead  760  to lead  770 . Alternatively, lead  760  may be manufactured with conductor  764  exposed, or connected to a pin as described above, in order to facilitate electrically connecting lead  760  to another lead. 
     Referring to  FIGS. 7A and 7B , once the insulation has been stripped from conductors  764  and  774  at distal ends  763  and  773 , respectively, the exposed portions of conductors  764  and  774  may each be connected to a portion of a conductor connector. In the illustrative embodiment of  FIG. 7B , conductor  774  is secured and electrically connected to a male connector  790 A having a conductive pin  794 , and conductor  764  is secured and electrically connected to a female connector  790 B having a lumen  797  configured to receive pin  794 . Male and female connectors  790 A and  790 B are electrically connected to one another by inserting pin  794  into lumen  797 . Together, male and female connectors  790 A and  790 B form a conductor connector referred to herein as male/female connector  790 . Male and female connectors  790 A and  790 B may be secured and electrically connected to conductors  774  and  764 , respectively, in any suitable manner. In the illustrative embodiment of  FIG. 7B , a conductive connection region  768 A of male connector  790 A is crimped to conductor  774  and thereby secured and electrically connected to conductor  774 , and a conductive connection region  768 B of female connector  790 B is crimped to conductor  764  and thereby secured and electrically connected to conductor  764 . In other embodiments, lead  760  is manufactured with female connector  790 B disposed at distal end  763  and electrically connected to conductor  764  to simplify the process for connecting lead  760  to lead  770 . 
     Referring to  FIGS. 7B and 7C , male and female connectors  790 A and  790 B are electrically connected by inserting pin  794  into lumen  797  to thereby electrically couple leads  760  and  770 . A sleeve  380 , as described above, is then longitudinally displaced along lead  760  or  770  until positioned around and encasing male/female connector  790 , as illustrated in  FIG. 7C . In certain embodiments, sleeve  380  will also cover portions of leads  760  and  770  extending from male and female connectors  790 A and  790 B. As shown in  FIG. 7C , the diameter of lumen  386  is large enough that, once sleeve  380  is positioned around male/female connector  790 , a space  750  is present between an inner surface of sleeve  380  and an outer surface of male/female connector  790 . Space  750  disposed within sleeve  380  is then filled with an insulative material, such as one of the insulative materials described above in relation to  FIGS. 3A-3D . While filling space  750 , the insulative material conforms around male/female connector  790  and other portions of leads  760  and  770  disposed in sleeve  380 . As described above, the insulative material may be a curable insulative material. When a curable insulative material is used, after filling space  750  with the curable insulative material, the curable insulative material is cured using any suitable means in order to form an impervious encasement  784  and to thereby form an implantable insulated lead connector  799 . In the illustrative embodiment of  FIG. 7C , implantable insulated lead connector  799 , comprises male/female connector  790  and impervious encasement  784 , which is disposed around male/female connector  790 . Impervious encasement  784  includes sleeve  380  and cured insulative material  385 B. As described above in relation to impervious encasement  384 , impervious encasement  784  substantially prevents the ingress of body fluid and tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue from male/female connector  790  out of impervious encasement  784 , and thereby insulates male/female connector  790 . 
     In certain embodiments, sealing elements may be applied to sleeve  380 , as described above. In the illustrative embodiment of  FIG. 7C , sleeve  380  is filled with a curable insulative material that is subsequently cured, and then secured with sutures  396  to form implantable insulated lead connector  799 . As illustrated in  FIG. 7C , sutures  396  compress sleeve  380  to leads  760  and  770  to secure sleeve  380  to leads  760  and  770 . Alternatively, other sealing elements, such as O-rings and/or toroidal springs, may be used to secure sleeve  380  to leads  760  and  770  and/or to further seal lumen  386 . In other embodiments, implantable insulated lead connector  799  is formed without sealing elements. 
     Implantable insulated lead connector  799  may be used to repair a lead extending between device components of an implantable medical device. For example, when a complete break has occurred in the lead, then the separated portions of lead may be connected using an implantable insulated lead connector  799  as described above for connecting leads  770  and  760 . Distal ends of the separate portions of the lead may be stripped, if necessary, as described above in relation to leads  770  and  760 . Alternatively, if a fault other than a complete break has occurred, then lead may be cut at the site of the fault, and thereafter the two portions of the lead may be connected as described above for leads  770  and  760 . In addition, as described in relation to implantable insulated lead connector  499 , implantable insulated lead connector  799  may be used to create an electrical connection between any two leads, and at substantially any location along either of the leads, and may be also used to customize the length of a lead of an implantable medical device. 
       FIGS. 8A-8C  illustrate an exemplary process for connecting leads  860  and  870  of respective device components of an implantable medical device using an implantable insulated lead connector  899  in accordance with embodiments of the present invention. In the illustrative embodiment of  FIGS. 8A-8C , the conductor connector that electrically couples leads  860  and  870  is a screw connector (or “grub screw” connector)  890  comprising male and female screw connectors  890 A and  890 B. Referring to  FIGS. 8A and 8B , lead  870  comprises conductors  874 A and  874 B substantially covered by insulation  872 A. In the illustrative embodiment of FIGS,  8 A- 8 C, conductors  874 A and  874 B are surrounded by insulation  871 A and  871 B such that they are electrically isolated from one another. In certain embodiments, lead  870  is manufactured and initially implanted with male screw connector  890 A disposed at a distal end  873  of lead  870 . Male screw connector  890 A comprises a contact pin  894  having a diameter that tapers in a substantially stepwise manner. Contact pin  894  includes a ring contact  876 A having a relatively small diameter and a ring contact  876 B which has a larger diameter than ring contact  876 A. Ring contacts  876 A and  876 B are electrically connected to conductors  874 A and  874 B, respectively. In certain embodiments, male screw connector  890 A is similar to an IS-1 connector used for pacemaker leads. 
     Lead  860  comprises conductors  864 A and  864 B covered by insulation  861 A and  861 B, respectively, such that conductors  864 A and  864 B are electrically isolated from one another. In certain embodiments, lead  860  is manufactured with female screw connector  890 B disposed at a distal end  863  of lead  860 . Female screw connector  890 B comprises a lumen  897  configured to receive contact pin  894 . The inner diameter of lumen  897  tapers in a substantially stepwise manner such that it may receive contact pin  894 . Female screw connector  890 B also comprises coupling screws  892 A and  892 B, which are electrically connected to conductors  864 A and  864 B, respectively. 
     An exemplary process for coupling leads  860  and  870  via an implantable insulated lead connector  899  in accordance with embodiments of the present invention will be described below with reference to  FIGS. 8A-8C . In certain embodiments, lead  870  may be a flying lead that is initially implanted with conductor contacts  876 A and  876 B covered by any suitable insulating package (not shown). The package is removed prior to electrically connecting leads  860  and  870 . 
     Referring to  FIGS. 8A and 8B , male and female screw connectors  890 A and  890 B are electrically connected by inserting contact pin  894  into lumen  897  and tightening coupling screws  892 A and  892 B to thereby electrically connect leads  860  and  870 . In the illustrative embodiment of  FIGS. 8A-8C , contact pin  894  is inserted into lumen  897  such that coupling screw  892 A surrounds a portion of ring contact  876 A and coupling screw  892 B surrounds a portion of ring contact  876 B. Coupling screw  892 A may be tightened via screw access  894 A to constrict around contact  876 A and thereby electrically connect to ring contact  876 A. Similarly, coupling screw  892 B may be tightened via screw access  894 B to constrict around ring contact  876 B and thereby electrically connect to ring contact  876 B. After tightening coupling screws  892 A and  892 B, leads  860  and  870  are electrically connected via screw conductor  890 . In alternative embodiments, coupling screws of female screw connector  890 B may be configured to penetrate insulation of male connector  890 A to thereby electrically connect to respective conductors of lead  870 . 
     Referring to  FIGS. 8B and 8C , after electrically connecting male and female screw connectors  890 A and  890 B, a sleeve  380 , as described above, is longitudinally displaced along lead  860  or  870  until it is positioned around and encasing screw connector  890 , as illustrated in  FIG. 8C . In certain embodiments, sleeve  380  will also cover portions of leads  860  and  870  extending from male and female screw connectors  890 A and  890 B. As shown in  FIG. 8C , the diameter of lumen  386  is large enough that, once sleeve  380  is positioned around screw connector  890 , a space  850  is present between an inner surface of sleeve  380  and an outer surface of screw connector  890 . Space  850  disposed within sleeve  380  is then filled with an insulative material, such as one of the insulative materials described above in relation to  FIGS. 3A-3D . While filling space  850 , the insulative material conforms around screw connector  890  and other portions of leads  860  and  870  disposed in sleeve  380 . As described above, the insulative material may be a curable insulative material. When a curable insulative material is used, after filling space  850  with the curable insulative material, the curable insulative material is cured using any suitable means in order to form an impervious encasement  884  and to thereby form an implantable insulated lead connector  899 . In the illustrative embodiment of  FIG. 8C , implantable insulated lead connector  899 , comprises screw connector  890  and impervious encasement  884 , which is disposed around screw connector  890 . Impervious encasement  884  includes sleeve  380  and cured insulative material  385 B. As described above in relation to impervious encasement  384 , impervious encasement  884  substantially prevents the ingress of body fluid and tissue to prevent the formation of any substantial conductive path of body fluid and/or tissue from screw connector  890  out of impervious encasement  884 , and thereby insulates screw connector  890 . 
     In certain embodiment, sealing elements may be applied to sleeve  380 , as described above in relation to  FIGS. 3A-3D . In the illustrative embodiment of  FIG. 8C , sleeve  380  is filled with a curable insulative material that is subsequently cured and is then secured with sutures  396  to form implantable insulated lead connector  899 . As illustrated in  FIG. 8C , sutures  396  compress sleeve  380  to leads  860  and  870  to secure sleeve  380  to leads  860  and  870 . Alternatively, other sealing elements, such as O-rings and/or toroidal springs may be used to secure sleeve  380  to leads  860  and  870  to further seal lumen  386 . In other embodiments, implantable insulated lead connector  899  is formed without applying any sealing element to sleeve  380 . 
     As noted above, in certain embodiments of the present invention, an implantable insulated lead connector may be used to form a reliable, insulated electrical connection between leads of device components of an implantable medical device. According to some embodiments, the implantable insulated lead connector may be used to create an insulated electrical connection between any two leads at nearly any location along either of the leads. Additionally, implantable insulated lead connectors according to embodiments of the present invention may be used to repair leads connecting distributed components of an implantable medical device. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. All patents and publications discussed herein are incorporated in their entirety by reference thereto.