Abstract:
Methods, lead retention assemblies and systems may provide a secure connection of electrical leads to an implantable medical device, such as a pacemaker or a defibrillator. The method may include: providing a lead retention assembly including a support member, a first side clamp and a second side clamp, a first port and a second port each defining a respective receptacle in conjunction with the support, and a fastener configured to urge both the first and second side clamps toward the support upon actuation of the fastener; providing at least two electrical lead bodies each including a respective proximal end portion; inserting the respective proximal end portions into the respective receptacles to be in electrical communication with a respective electrical contact in the respective receptacles; and actuating the fastener to thereby clamp the proximal end portions of the respective electrical lead bodies within the first and second ports.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to lead retention assemblies of implantable medical devices and methods for connecting implantable medical leads to such devices. More particularly, the present invention relates to methods and mechanisms for securely locking implantable medical leads within a lead retention assembly. 
   BACKGROUND OF THE INVENTION 
   Cardiac pacemakers, and other implantable stimulation devices such as cardioverters and defibrillators, are typically hermetically sealed within a housing or casing (sometimes also referred to as a “can”) to isolate the electronic circuits contained within the device from the body environment. Such devices require that electrical signals be reliably passed between the hermetically sealed circuitry and external connectors without compromising the hermeticity of the device. Depending on the configuration of the implantable device there may be multiple electrical paths required between the device and its external connectors for delivering, for example, multi-chamber or multi-site stimulation and shock therapy, and for receiving sensed cardiac signals. These paths should be electrically and mechanically integrated with the device to provide a safe, long-term lead retention assembly that does not compromise the hermetic package. 
   Typically, a hermetic housing feedthrough electrically couples the electronic circuits contained within the device housing to the lead retention assembly. The feedthrough may extend through the wall of the hermetically sealed casing into the lead retention assembly so as to couple the electronic circuits within the casing to lead-receiving receptacles within the lead retention assembly. Each lead has one or more electrical terminals on a proximal end thereof, typically in the form of a pin terminal and one or more conductive ring terminals. Typically, the pin is electrically coupled to a distal tip electrode and is therefore sometimes called the “tip terminal.” When the proximal end of the lead is inserted into the lead receptacle of a lead retention assembly, contacts within the receptacle come into contact with corresponding terminals on the lead so as to couple the lead to the electronic circuits within the implantable stimulation device via the feedthrough assembly. Needless to say, a completely dependable electrical connection is useful between the lead terminals and the corresponding lead retention assembly contacts. At the same time, the lead retention assembly being capable of releasing the lead from the lead receptacle during explantation or other subsequent surgical procedure may be useful, as may doing so while remaining tightly sealed against the entry of body fluids. 
   It is known in prior art lead retention assemblies to electrically and mechanically connect the proximal end of the lead within a receptacle of the lead retention assembly by a variety of expedients including captive fastening screw/collet arrangements and setscrews. In such prior art lead retention assemblies in which the lead is fixed within the lead receptacle using a setscrew, the setscrew is often threaded into an electrical connector block within the lead retention assembly. When the screw is advanced, it comes into contact with an associated terminal on the proximal end of the lead, mechanically and electrically coupling the lead and the lead retention assembly. 
   U.S. Pat. No. 6,984,145, issued Jan. 10, 2006, the entirety of which is incorporated herein by reference, discloses an example of a lead retention assembly mounted on an implantable cardiac stimulation device having a side-actuated mechanism for fixing and tightly sealing electrical leads inserted into lead receptacles. 
   SUMMARY 
   There is a need in the art for improved systems and methods for connecting a plurality of electrical leads to an implantable medical device. Although technology related to connection assemblies has advanced to provide various approaches, such approaches tend to be complex and/or expensive. Accordingly, it would be desirable to provide a lead retention assembly for connecting a plurality of electrical leads to an implantable medical device that is more reliable and easier to use. 
   Various embodiments of the present invention may provide a lead retention assembly in which a fastener is configured to urge both a first side clamp and a second side clamp toward a support upon actuation of the fastener. Such an approach may reduce a number of fasteners needed to secure a plurality of electrical leads. 
   Some embodiments may provide a lead retention assembly in which the various components are held together in an unclamped state. Such an approach may prevent a loss of parts, and may also facilitate clamping actuation of the lead retention assembly. 
   Embodiments of the present invention may provide a lead retention assembly for connecting a plurality of electrical leads to an implantable medical device. The lead retention assembly may include at least two receptacles each configured to receive a proximal end portion of a respective electrical lead. Each receptacle may include an electrical contact for electrically connecting the respective electrical lead to electrical circuitry of an implantable medical device. The lead retention assembly may further include a support member, a first side clamp configured to define a first port in conjunction with the support, a second side clamp configured to define a second port in conjunction with the support and a fastener configured to urge both the first and second side clamps toward the support upon actuation of the fastener. Such urging may cause the lead retention assembly to clamp the proximal end portions of the respective electrical leads within the first and second ports. 
   Embodiments of the present invention may provide a system for connecting electrical leads in an implantable medical device. The system may include an implantable medical device including electrical circuitry and a lead retention assembly configured to be secured to the implantable medical device. The lead retention assembly may include a support member, a first side clamp and a second side clamp. The first and second side clamps may respectively be configured to define first and second ports in conjunction with the support, which ports may include respective receptacles configured to receive a respective electrical lead body. Each receptacle may include an electrical contact for electrically connecting the respective electrical lead body to the electrical circuitry of the implantable medical device. The lead retention assembly may further include a fastener configured to urge both the first and second side clamps toward the support upon actuation of the fastener, to thereby clamp the respective electrical lead bodies within the first and second ports. The system may also include at least two electrical leads each including a proximal end portion configured to be secured in the first and second ports respectively when the first and second side clamps are urged toward the support upon actuation of the fastener. 
   Embodiments of the present invention may provide a method for connecting electrical leads in an implantable medical device. The method may include providing a lead retention assembly, or system, such as described above; inserting at least two electrical lead bodies, each including a respective proximal end portion, into the respective receptacles to be in electrical communication with a respective electrical contact in the respective receptacles; and actuating the fastener to thereby clamp the proximal end portions of the respective electrical lead bodies within the first and second ports. 
   Disclosed herein is an implantable pulse generator such as a pacemaker, defibrillator or implantable cardioverter defibrillator (ICD). The generator is configured to have at least first and second implantable cardiac electrotherapy leads secured thereto. In one embodiment, the generator includes a first clamp, a second clamp and an actuator. The first clamp is configured to secure the first lead to the generator. The second clamp is configured to secure the second lead to the generator. The actuator is configured to cause both clamps to secure their respective leads. 
   Disclosed herein is an implantable pulse generator such as a pacemaker, defibrillator or ICD. The generator is configured to have at least first and second implantable cardiac electrotherapy leads secured thereto. In one embodiment, the generator includes a pair of opposed clamps, a support positioned between the clamps, and an actuator. Rotation of at least a portion of the actuator relative to the support causes both clamps to generally simultaneously increasingly clamp the leads against the front support portion. 
   Disclosed herein is an implantable pulse generator such as a pacemaker, defibrillator or ICD. The generator is configured to have at least first and second implantable cardiac electrotherapy leads secured thereto. In one embodiment, the generator includes a pair of opposed clamps, a support positioned between the clamps, and a means for generally simultaneously impacting the positional relationship of both clamps relative to the front support portion to secure the leads between the clamps and the support. 
   While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the proximal end portion or connective end of a known bipolar lead. 
       FIG. 2  is a perspective view of an example of a lead retention assembly. 
       FIG. 3  is a side elevation view of the lead retention assembly depicted in  FIG. 2 . 
       FIG. 4  is a side elevation view of one of the side clamps of the lead retention assembly of  FIG. 2 . 
       FIG. 5  is a cross-sectional view of the side clamp of  FIG. 4 , taken along line B-B in  FIG. 4 . 
       FIG. 6  is a side elevation view of the other one of the side clamps of the lead retention assembly of  FIG. 2 . 
       FIG. 7  is a cross-sectional view of the side clamp of  FIG. 6 , taken along line C-C in  FIG. 6 . 
       FIG. 8  is a cross sectional view of the lead retention assembly of  FIG. 3 , taken along line A-A in  FIG. 3 . 
       FIG. 9  is a partial enlarged view of detail A in  FIG. 8 . 
       FIG. 10  is a side elevation view of one portion of the fastener of  FIG. 8 . 
       FIG. 11  is a cross-sectional view of the other portion of the fastener of  FIG. 8 . 
       FIG. 12  is a perspective view of a cardiac pacemaker/defibrillator unit including an example of a lead retention assembly. 
       FIG. 13  is a cross sectional view of another example of a lead retention assembly, similar to  FIG. 8 . 
       FIG. 14  is a partial enlarged view of detail A′ in  FIG. 13 . 
       FIG. 15  is a side elevation view of one portion of the fastener of  FIG. 13 . 
       FIG. 16  is a cross-sectional view of another portion of the fastener of  FIG. 13 . 
       FIG. 17  is an end view of the female fastener portion, as viewed from the bore end of the female fastener portion. 
   

   DETAILED DESCRIPTION 
   The following description is of embodiments presently contemplated for practicing the invention. This description is not to be taken in a limiting sense but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be ascertained with reference to the issued claims. In the description of the invention that follows, like numerals or reference designators will be used to refer to like parts or elements throughout. 
   Although it should be understood that the present invention is applicable to a variety of implantable medical devices, the description herein is principally in the context of a specific example of such devices, namely, an implantable cardiac device, such as a pacemaker and/or defibrillator. However, such description is for the sake of understanding only, and is not limiting. 
   The disclosed devices, systems and associated methods are directed at connecting a plurality of electrical leads to an implantable medical device. Such connection may occur, for example, before or during implantation of the device, or after the device has been implanted, for example, to replace one or more leads. Although the methods contemplated are described in conjunction with the devices and systems illustrated herein, it should be understood that numerous variations exist for implementing the methods. 
     FIG. 1  shows a proximal end portion or connective end  10  of a conventional transvenous, bipolar pacing lead. The proximal lead end portion  10  may be configured to be secured to an implantable medical device using a lead retention assembly as described further below. In particular, the proximal lead end portion  10  may include a pair of coaxial spaced-apart terminals including a tip terminal  12  and a ring terminal  14 . The proximal lead end portion  10  may include one or more features  16  that are configured to be engaged by a lead retention assembly. 
   Such a lead is well known, as is described in the incorporated U.S. Pat. No. 6,984,145. Thus, further details are not discussed. It should be understood that the pacing lead is only an example of an electrical lead that may be used with the devices, systems and methods described herein. In particular, it should be understood that the proximal lead end portion of the electrical lead may or may not include any suitable feature(s) for cooperating with the lead retention assembly, to provide a mechanical engagement and/or a friction fit, as appropriate or desired. 
     FIG. 2  is a perspective view of an example of a lead retention assembly  22 . The lead retention assembly  22  may include a plurality of ports that define a first set of receptacles  31 ,  32 ,  33  and a second set of receptacles  34 ,  35 ,  36 . Each of the receptacles  31 - 36  may be configured to receive the proximal or connective ends  10  of electrical leads. Six total receptacles are shown to illustrate various details. However, it should be understood that any desired number of receptacles may be used. The bores of the receptacles may include various features suitable for engaging and retaining respective electrical leads, in conjunction with the lead retention assembly  22 , as described herein. Further, one or more electrical contacts may be disposed in the bores of the receptacles to provide a connection to electrical circuitry of the implantable medical device to which the lead retention assembly  22  is to be attached. 
   The lead retention assembly  22  may include a support  40 , opposed first and second side clamps  42 ,  44 , and one or more fasteners  45  for securing the side clamps to the support  40  to clamp the connective ends  10  of the leads in place. The support  40  may be molded of a material such as polysulfone or tecothane. The side clamps  42 ,  44  may be molded of material such as polysulfone or delrin or machined from a material such as titanium or stainless steel. The support  40  may include a rear portion  50  and a nose or front portion  52  that is narrower than the rear portion and defines opposed side recesses  54 ,  56  for receiving the side clamps  42 ,  44 , respectively. The rear support portion  50 , the front support portion  52  and the side clamps  42 ,  44  include curved outer surfaces that form a substantially continuous, smooth, outer lead retention assembly surface when the side clamps are in their fully clamped position, as illustrated in  FIG. 2 , for example. 
     FIG. 3  is a side elevation view of the lead retention assembly  22 .  FIG. 4  is a similar view of the first side clamp  42  removed from the lead retention assembly  22 . As shown in the cross-sectional view of the first side clamp  42  in  FIG. 5 , and with further reference to  FIGS. 6-9 , a bore  70  for receiving each fastener  45  may extend through the side clamps  42 ,  44  and the front support portion  52  of the lead retention assembly  22 . 
   Depending on the embodiment, the lead retention assembly  22  may have one, two or more bores  70  and one, two or more fasteners  45 . For example, as can be understood from  FIGS. 2-8 , in one embodiment, the lead retention assembly  22  may have two bores  70  with a fastener  45  within each bore  70 . While the various cross-sectional views in the figures are such that only a single one of the multiple bores  70  and fasteners  45  are portrayed in full cross-section, it should be understood that, in at least one embodiment, the configurations of all bores  70  and fasteners  45  of the lead retention assembly  22  are generally identical. Thus, the bore and fastener configurations depicted in FIGS.  5  and  7 - 11 , can be considered to apply equally to all bores  70  and fasteners  45  of an embodiment of the lead retention assembly  22  employing more than one bore  70  and fastener  45 . Depending on the embodiment, the statements in this paragraph are also similarly applicable to the embodiments depicted in  FIGS. 12-16 . 
   As illustrated in  FIGS. 4-9 , the bores  70  may include various diameters, threads or other features for cooperating with the fasteners  45 . As shown in  FIG. 5 , the portion of the bore  70  extending through the first side clamp  42  may provide a first outer shoulder  71 . 
     FIG. 6  is a side elevation view of the second side clamp  44 . As shown in the corresponding cross-sectional view of the second side clamp  44  in  FIG. 7 , the portion of the bore  70  extending through the second side clamp  44  may provide a second outer shoulder  72 . The portion of the bore  70  extending through the second side clamp  44  may further provide an internal clamp thread  73  and a first inner shoulder  74 . 
   As shown in  FIG. 8 , and in detail in  FIG. 9 , the portion of the bore  70  extending through the front support portion  52  may provide additional features in the front support portion  52 . In particular, the portion of the bore  70  extending through the front support portion  52  may define a second inner shoulder  75 , a third inner shoulder  76 , and a cavity  220 . The fastener  45  may include corresponding features that cooperate with the features of the bore  70 , as described below. 
   The fastener  45  may include a first or male fastener portion  46  and a second or female fastener portion  48 .  FIG. 10  shows details of the male fastener portion  46 .  FIG. 11  shows details of the female fastener portion  48 .  FIGS. 8 and 9  show the male and female fastener portions  46 ,  48  engaged to render the fastener  45  operative in the lead retention assembly  22  such that a portion of the male fastener portion  46  is received in a portion of the female fastener portion  48 . 
   With reference to  FIG. 10 , the male fastener portion  46  may include a wide diameter shaft section  199 , a narrow diameter shaft section  64 , and a ridge or ring  200  located between the two shaft sections. In one embodiment, the ring  200  extends circumferentially about shaft of the male fastener portion  46 . 
   A free end of the wide diameter shaft section  199  of the male fastener portion  46  may include a first threaded end  61  configured to engage the internal clamp thread  73  in the second side clamp  44 . The male fastener portion  46  may include a first shoulder  62  between the first threaded end  61  and the ring  200 . The first shoulder  62  of the male fastener portion  46  may be configured to abut the first inner shoulder  74  in the second side clamp  44 , for example, when the first threaded end  61  of the male fastener portion  46  is fully engaged in the internal clamp thread  73  of the second side clamp  44 . 
   The ring  200  of the male fastener portion  46  may form a second shoulder  63  configured to abut the second inner shoulder  75  in the front support portion  52 , for example, when the lead retention assembly  22  is fully opened to the maximum extent, as depicted in  FIG. 9  for one embodiment. 
   The narrow diameter shaft section  64  of the male fastener portion  46  may extend from the ring  200 . The free end of the narrow diameter shaft section  64  may include a second threaded end  65 . As described below and depicted in  FIG. 9 , the narrow diameter shaft section  64  may be configured to allow the second threaded end  65  of the male fastener portion  46  to cooperate with the female fastener portion  48 . 
   With reference to  FIG. 11 , the female fastener portion  48  may include a head  81  configured to engage the first outer shoulder  71  of the first side clamp  42 , as depicted in  FIG. 9 . The head  81  and shoulder  71  engage when the lead retention assembly  22  is fully closed (clamped). Also, the head  81  engages the shoulder  71  so the head  81  can drive the first side clamp  42  towards the front support portion  52  when the first side clamp  42  is being moved towards the fully clamped state. 
   As indicated in  FIG. 11 , the head  81  also includes a tool engagement feature  205  for engagably receiving a screwdriver, wrench, etc. Thus, a tool can be used to cause the female fastener portion  48  to rotate within the bore  70  and relative to the male fastener portion  46 , thereby causing the male fastener portion  46  to be threadably received within the female fastener portion  48 , as indicated in  FIG. 9 . 
   As shown in  FIG. 11 , the female fastener portion  48  may include a cavity or bore  210  extending axially into the female fastener portion  48 . The bore  210  may include a first internal thread  82  and a second internal thread  83  longitudinally separated by an unthreaded or threadless portion  84 . 
   As can be understood from  FIG. 9 , the male and female fastener portions  46 ,  48  may be secured together by threading the second threaded end  65  of the male fastener portion  46  into the second internal thread  83  of the female fastener portion  48 . By threading past the second internal thread  83 , the second threaded end  65  of the male fastener portion  46  may be movable within the unthreaded portion  84  of the female fastener portion  48 , for example, to provide a limited amount of play or relative movement of the male and female fastener portions  46 ,  48  while connected. This amount of play or relative movement of the male and female fastener portions  46 ,  48  provides the side clamps  42 ,  44  with sufficient play relative to the front support portion  52  to accommodate a lead connective end  10  without having to rotate the female fastener portion  48  within the bore  70 . 
   As illustrated in  FIG. 11 , the female fastener portion  48  may optionally include a full diameter shaft section  215  and a reduced diameter shaft section  85 . The reduced diameter shaft section  85  of the female fastener portion  48  may facilitate connecting an anchor  90  to the female fastener portion  48 , as shown in  FIGS. 8 and 9 . The anchor  90  may be made of nitinol, for example, and may be fixedly attached to the female fastener portion  48 , for example, by welding. It should be understood that any other suitable metal or non-metal material may be used for the anchor  90  and that the anchor  90  may be attached in any suitable manner, such as with a mechanical or frictional engagement, or with adhesive. 
   The anchor  90  may include one or more outwardly extending flange  92 . The outwardly extending flange  92  may be of any suitable shape and/or size, as may the anchor  90 . For example, the anchor  90  and/or the outwardly extending flange  92  may be annular. Alternatively, the outwardly extending flange  92  may include one or more protrusions or tabs. 
   As shown in  FIG. 9 , the outwardly extending flange  92  may be configured to retain the female fastener portion  48  in the cavity  220  inside the support  40  by cooperating with the third inner shoulder  76 . Thus, the first side clamp  42 , the front support portion and the female fastener portion  48  may be held together, with a suitable amount of play to allow insertion of electrical leads into the lead retention assembly  22 . Further, the outwardly extending flange  92  of the anchor  90  may be configured to abut the third inner shoulder  76  on the front support portion  52 , for example, when the lead retention assembly  22  is fully opened to the maximum extent. 
   As can be understood from  FIGS. 8 and 9 , the second shoulder  63  of the male fastener portion  46  encountering the front support portion  52 , specifically, the second inner shoulder  75 , prevents the second side clamp  44  from overly moving away from the front support portion  52 , thereby preventing the male fastener portion  46  from exiting the bore  70  on the side of the front support portion  52  having the second side clamp  44 . Similarly, the flange  92  encountering the front support portion  52 , specifically, the third inner shoulder  76 , prevents the first side clamp  42  from overly moving away from the front support portion  52 , thereby preventing the female fastener portion  48  from exiting the bore  70  on the side of the front support portion  52  having the first side clamp  42 . 
   As discussed above and can be understood from  FIG. 9 , the male fastener portion  46  may be secured to the second side clamp  44 . In one embodiment, this may occur after the male fastener portion  46  is inserted through the bore  70  of the front support portion  52  from the side of the first clamp  42 . The large diameter shaft sections  199 ,  215  of the fastener portions  46 ,  48  may have generally the same diameter, which is less than the diameter of the bore  70 . As a result, the fastener portions  46 ,  48  can be passed into the bore  70  by entering the bore from the side of the front support portion  52  having the first side clamp  42 . The male fastener portion  46  is entered into the bore  70  first with the first threaded end  61  of the male fastener portion  46  leading. The second shoulder  63  of the male fastener portion  46  encountering the second inner shoulder  75  in the front support portion  52  prevents the male fastener portion  46  from overly extending through the bore  70 . 
   In one embodiment, as can be understood from  FIG. 9 , the female fastener portion  48 , with the anchor  90  mounted thereon, is passed anchor end first through the bores  70  of the first side clamp  42  and the front support portion  52 . As the anchor  90  passes through the bores  70 , the flanges  92  deflect against the sides of the reduced diameter portion  85  of the shaft of the female fastener portion  48 , thereby providing sufficient clearance for the anchor end of the female fastener portion  48  to extend through the bores  70 . When the flanges  92  clear the third inner shoulder  76  of the front support portion  52  as the anchor end of the female fastener portion  48  enters the cavity  220  of the front support portion  52 , the flanges  92  bias outwardly to engage the third inner shoulder  76  and prevent the withdrawal of the female fastener portion  48  from the front support portion  52 . 
   As indicated in  FIG. 9 , in one embodiment, the first threaded end  61  of the male fastener portion  46  is threaded into the internal clamp thread  73  of the second side clamp  44 . Thus, the male fastener portion  46 , the second side clamp  44  and the front support portion  52  may be held together, with a suitable amount of play to allow insertion of lead connector ends  10  into the lead retention assembly  22 . 
   In another embodiment, the male fastener portion  46  does not have the first threaded end  61 . Instead, the region of male fastener portion  46  having the first threaded end  61  depicted in  FIG. 10  is without threads. This threadless area of the male fastener portion  46  is affixed to the hole  73  in the second side clamp  44 , the hole  73  being threadless in this embodiment. In one embodiment, the fixation between the male fastener portion  46  and the hole  73  is via adhesive or mechanical or friction fit. 
   As shown in  FIG. 9 , the head  81  of the female fastener portion  48  engages the first outer shoulder  71  of the first side clamp  42 , and the flange  92  on the shaft of the female fastener portion  48  engages the third inner shoulder  76  of the front support portion  52 . As a result, the first side clamp  42 , the front support portion  52  and the female fastener portion  48  may be held together, with a suitable amount of play to allow insertion of lead connector ends  10  into the lead retention assembly  22 . 
   As indicated in  FIG. 9 , in one embodiment, the fastener portions  46 ,  48  are engaged with each other with the second threaded end  65  of the male fastener portion  46  being received in the bore  210  of the female fastener portion  48 . Specifically, a tool is utilized to rotate the female fastener portion  48  in a first direction relative to the male fastener portion  46  such that the second threaded end  65  of the male fastener portion  46  threadably engages the second internal thread  83  of the female fastener portion  48 . Further rotation of the female fastener portion  48  in the first direction causes the second threaded end  65  of the male fastener portion  46  to extend deeper into the bore  210  of the female fastener portion  48  until the second threaded end  65  enters the threadless region  84  of the bore  210  of the female fastener portion  48 . At this point, the first and second side clamps  42 ,  44  are secured to the front support portion  52  in such a manner that there is a suitable amount of play between the front support portion  52  and the side clamps  42 ,  44  to allow insertion of lead connective ends  10  into the lead retention assembly  22 . 
   In one embodiment and as can be understood from  FIGS. 2 ,  8  and  9 , subsequent to the insertion of lead connective ends  10  into the appropriate receptacles  31 - 36 , the side clamps  42 ,  44  are pressed towards the front support portion  52  to cause the second threaded end  65  of the male fastener portion  46  to move across the threadless region  84  of the bore  210  of the female fastener portion  48  to be able to threadably engage the first internal thread  82  of the female fastener portion  48 . Further rotation of the female fastener portion  48  in the first direction causes the second threaded end  65  of the male fastener portion  46  to threadably engage and travel along the first internal thread  82  of the female fastener portion  46 . As a result, both fastener portions  46 ,  48  converge inwardly towards the cavity  220 , drawing the side clamps  42 ,  44  towards the front support portion  52  and clamping the lead connective ends  10  within their respective receptacles  31 - 36 . To release the lead connective ends  10  from their respective receptacles  31 - 36 , the aforementioned process is reversed. 
   The preceding discussion pertains to various embodiments wherein the female fastener portion  48  includes the head  81  and is free to rotate relative to the male fastener portion  46 , which is fixed to the second side clamp  44  and prevented from rotating relative to the front support portion  52 . However, in other embodiments, the male fastener portion  46  includes the head and is free to rotate relative to the female fastener portion  48 , which is fixed to the first side clamp  42  and prevented from rotating relative to the front support portion  52 . 
   The preceding discussion pertains to various embodiments wherein the male fastener portion  46  includes a ring  200 , the female fastener portion  48  includes an anchor  90  with a flexible flange  92 , and the fastener portions  46 ,  48  are passed into the bore  70  of the front support portion  52  via the side of the front support portion  52  having the first side clamp  42 . However, in other embodiments, the ring  200  of the male fastener portion  46  can be replaced with an anchor similar to the anchor  90  on the female fastener portion  48 . With such an embodiment, the male fastener portion  46  could pass into the bore  70  of the front support portion  52  via the side of the front support portion  52  having the second side clamp  44 . 
   As can be understood from  FIGS. 2 ,  8  and  9 , in one embodiment, the lead retention assembly  22  is advantageous for a number of reasons. For example, a physician can cause both side clamps  42 ,  44  to generally simultaneously clamp against the front support portion  52  by applying a tool (e.g., screw drive or wrench) to the heads  81  of the fasteners  45  on a single side of the lead retention assembly  22 . In other words, each fastener  45  is coupled to both side clamps  42 ,  44  such that rotating the head  81  of a single fastener  45  results in generally simultaneous translation of both side clamps  42 ,  44  relative to the front support portion  52 . Thus, connection of lead connective ends  10  to an implantable pulse generator (e.g., pacemaker, defibrillator, etc.) via the above-described lead retention assembly  22  is more efficient than other lead retention assemblies that have head equipped fasteners on each side clamp and require a physician to rotate fasteners associated with a first side clamp to cause the first side clamp to clamp before rotating fasteners associated with a second side clamp to cause the second side clamp to clamp. 
     FIG. 12  shows an example of an implantable medical device  20  incorporating an embodiment of a lead retention assembly  22 ′. In this example, the lead retention assembly  22 ′ includes four ports/receptacles  30 ′,  32 ′,  34 ′,  36 ′. Further, the lead retention assembly  22 ′ includes a single fastener  45 . As described above, the single fastener  45  is similar to that depicted in  FIGS. 9-11  and facilitates the generally simultaneous actuation of both side clamps  42 ,  44  to clamp lead connector ends  10  into the receptacles  30 ′,  32 ′,  34 ′,  36 ′. In particular, the clamping action may be performed by actuating the fastener  45  from only one side such that both side clamps  42 ,  44  move toward the front support portion  52  generally simultaneously via rotating engagement of a head  81  of a single fastener  45 . Thus, the number of fasteners needed is reduced, for example, from two to one, the number fasteners heads that need to be accessed is reduced, for example, from two to one, and the number of sides of an lead retention assembly that need to be accessed is reduced from two to one. 
   The mounting of the lead retention assembly  22 ′ on the implantable medical device  20  may be in any known or hereafter developed manner, and thus is not described herein. It should be understood that any suitable location of the lead retention assembly  22 ′ on the implantable medical device  20  may be employed, for example, depending on the particular configuration of the implantable medical device  20 . 
     FIGS. 13-16  are generally the same views depicted in  FIGS. 8-11 , except of another embodiment of a lead retention assembly  122 . In the embodiment depicted in  FIGS. 13-16 , various elements may be substantially identical to the embodiments discussed with respect to  FIGS. 2-12 . However, the embodiment depicted in  FIGS. 13-16  differs with respect to the fastener and the bore in which the fastener is inserted. These features of the embodiment depicted in  FIGS. 13-16  are discussed in detail below, with minimal detail regarding the features similar to the embodiments depicted in  FIGS. 2-12 . 
   As shown in  FIGS. 13 and 15 , the lead retention assembly  122  may include a plurality of ports that define a first set of receptacles  131 ,  132 ,  133  and a second set of receptacles  134 ,  135 ,  136 . The lead retention assembly  122  may include a support  140  with a rear support portion  150  and a front support portion  152 , opposed first and second side clamps  142 ,  144 , and one or more fasteners  145  for securing the side clamps to the front support portion  152  to clamp lead connective ends in place. 
   As shown in detail in  FIGS. 13-16 , a bore  170  for receiving each fastener  145  may extend through the side clamps  142 ,  144  and the front support portion  152  of the lead retention assembly  122 . As shown in  FIGS. 13 and 14 , the bore  170  may provide a first outer shoulder  171  in the first side clamp  142  and a second outer shoulder  172  in the second side clamp  144 . 
   The bore  170  may provide an internal clamp thread  173  and a first inner shoulder  174  in the second side clamp  144 . The bore  170  may provide a second inner shoulder  175  in the front support portion  152 . The fastener  145  may include corresponding features that cooperate with the features of the bore  170 , as described below. 
   The fastener  145  may include a first or male fastener portion  146  and a second or female fastener portion  148 .  FIG. 15  shows details of the male fastener portion  146 .  FIG. 16  shows details of the female fastener portion  148 .  FIGS. 13 and 14  show the fastener portions  146 ,  148  engaged to render the fastener  145  operative in the lead retention assembly  122 . 
   With reference to  FIG. 15 , the male fastener portion  146  may include a first threaded end  161  configured to engage the internal clamp thread  173  in the second side clamp  144 . The male fastener portion  146  may include a first shoulder  162  configured to abut the first inner shoulder  174  in the second side clamp  144 , for example, when the first threaded end  161  is fully engaged in the internal clamp thread  173 . 
   The male fastener portion  146  may also include a ring  200  and a second shoulder  163  configured to abut the second inner shoulder  175  in the front support portion  152 , for example, when the lead retention assembly  122  is fully opened to the maximum extent, as depicted in  FIG. 13 . 
   A narrower diameter portion  164  of the male fastener portion  146  may extend from the second ring  200  to provide a second threaded end  165 . As described below, the narrower diameter portion  164  of the male fastener portion  146  may be configured to allow the second threaded end  165  to cooperate with the female fastener portion  148 . In particular, the narrower diameter portion  164  of the male fastener portion  146  may include a flange  166  that extends radially outwardly. The flange  166  may include a chamfer  167 . 
   With reference to  FIGS. 14 and 16 , the female fastener portion  148  may include a head  181  configured to engage the first outer shoulder  171  of the first side clamp  142 , for example, when the lead retention assembly  122  is fully closed or the head  181  is driving the first side clamp  142  to the closed or clamped state. 
   As indicated in  FIG. 16  and  FIG. 17 , which is an end view of the female fastener portion  148  as viewed from the bore end of the female fastener portion  148 , the female fastener portion  148  may include a bore  210  with an internal thread  182  that is longitudinally separated from a flanged end  186  by an unthreaded portion  184 . The flanged end  186  includes flanges  235 . The cylindrical shaft portion  230  of the female fastener portion  148  forms unthreaded portion  184  and may include one or more longitudinal slots  187  that segments the cylindrical shaft portion  230  into two or more radial shaft segments  230   a ,  230   b ,  230   c ,  230   d , as best understood from  FIG. 17 . The radially segmented configuration of the cylindrical shaft portion  230  of the female fastener portion  148  allows the flange  166  of the male fastener portion  146  to pass the flanges  235  of the flanged end  186  of the female fastener portion  148 , for example, by allowing the flanged end  186  to flex outwardly. Alternatively, the flanged end  186  and/or the unthreaded portion  184  may be sufficiently flexible for such purpose and not require the radially segmented configuration of the cylindrical shaft portion  230  of the female fastener portion  148 . 
   The flanges  235  of the flanged end  186  of the female fastener portion  148  may also include chamfers  188  that cooperate with the chamfer  167  of the flange  166  of the male fastener portion  146  to facilitate insertion of the flange  166  of the male fastener portion  146  past the flanged end  186  into the unthreaded portion  184  of the female fastener portion  148 . Thus, the fastener portions  146 ,  148  may be secured together by pushing them longitudinally towards each other. In such a condition, the second threaded end  165  may be movable within the unthreaded portion  184 , for example, to provide a limited amount of play or relative movement of the fastener portions  146 ,  148  while connected and, as a result, a limited amount of movement of the side clamps  142 ,  144  relative to the front support portion  152 . 
   As with the embodiments discussed with respect to  FIGS. 2-12 , rotating the female fastener portion  148  relative to the male fastener portion  146 , which, in one embodiment, is fixed to the second side clamp  144 , causes the second threaded end  165  of the male fastener portion  146  to engage the first threaded portion  182  of the female fastener portion  148 . Thus, the engaged threads cause the fastener portions  146 ,  148  to translate toward each other. Such translation causes both the first and second side clamps  142 ,  144  to move toward the front support portion  152  to thereby lead connective ends  10  that are inserted into the receptacles. 
   As can be understood from the preceding discussion, the fasteners  45  act as actuators  45  for actuating the side clamps  42 ,  44  to secure the leads to the pulse generator (e.g., defibrillator, pacemaker, or ICD)  20 . Lead connective ends  10  are placed in their respective receptacles  31 - 36 , and the actuators  45  are manipulated to cause both of the clamps  42 ,  44  connected thereto to clamp the lead connective ends between the front support portion  52  and the respective clamp. As can be understood from the preceding discussion, in one embodiment, each actuator  45  is operably coupled to both clamps  42 ,  44 . Actuation of a single actuator  45  impacts the positional relationship of both clamps  42 ,  44  relative to the front support portion  52 . Thus, rotating a single actuator  45  in a first direction relative to the generator  20  can cause both clamps  42 ,  44  to generally simultaneously increasingly clamp lead connective ends  10  against the front support portion  52 . Conversely, rotating a single actuator  45  in a second direction relative to the generator  20  can cause both clamps  42 ,  44  to generally simultaneously decreasingly clamp lead connective ends  10  against the front support portion  52 . 
   Although the present invention has been described with reference to particular embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.