Abstract:
A connector assembly for detachably coupling a proximal end of a lead and an implantable medical device. The connector assembly includes a deflectable connector clip having a first arm, a second arm and a top portion extending between the first arm and the second arm. The first arm and the second arm detachably position the proximal end of the lead within the implantable medical device. A housing portion has a first deflection portion that deflects the connector clip from a first position corresponding to a first distance between the first arm and the second arm, to a second position corresponding to a second distance between the first arm and the second arm. Subsequent advancement of the lead through the first and second arms further deflects the connector clip from the second position to a third position, which transfers all of the spring force of the connector clip to the lead.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Cross-reference is hereby made to commonly assigned related U.S. Applications, filed concurrently herewith, Ser. No. ______ docket number P-111616, entitled “CONNECTOR ASSEMBLY FOR CONNECTING A LEAD AND AN IMPLANTABLE MEDICAL DEVICE”, Ser. No. ______ docket number P-11122, entitled “SMALL FORMAT CONNECTOR CLIP OF AN IMPLANTABLE MEDICAL DEVICE”, and Ser. No. ______ docket number P-10955, entitled “ELECTRICAL CONNECTOR ASSEMBLY FOR COUPLING MEDICAL LEADS TO IMPLANTABLE MEDICAL DEVICES”, incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to medical leads of implantable medical devices and, more particularly, to a connector assembly of an implantable medical device that facilitates coupling between a lead and circuitry of the implantable medical device.  
       BACKGROUND OF THE INVENTION  
       [0003]     In the medical field, leads are used with a wide variety of medical devices. For example, leads are commonly implemented to form part of an implantable medical device (IMD), such as implantable cardiac pacemakers that provide therapeutic stimulation to the heart by delivering pacing, cardioversion or defibrillation pulses. The pulses can be delivered to the heart via electrodes disposed on the leads, e.g., typically near distal ends of the leads. In that case, the leads may position the electrodes with respect to various cardiac locations so that the pacemaker can deliver pulses to the appropriate locations. Leads are also used for sensing purposes, or both sensing and stimulation purposes.  
         [0004]     In addition, leads are used in neurological devices such as deep-brain stimulation devices, and spinal cord stimulation devices. For example, the leads may be stereotactically probed into the brain to position electrodes for deep brain stimulation. Leads are also used with a wide variety of other medical devices including, for example, devices that provide muscular stimulation therapy, devices that sense chemical conditions in a patient&#39;s blood, and the like. In short, medical leads may be used for sensing purposes, stimulation purposes, or both.  
         [0005]     An IMD typically includes one or more leads, a housing that houses circuitry of the IMD, and a connector block that couples the lead to the circuitry. In particular, the connector block includes electrical contact structures for coupling the lead to circuitry within the housing of the IMD so that therapeutic simulation can be provided through the lead, or sensed conditions can be recorded by the circuitry. One challenge in implementing medical leads in a medical device is the electrical coupling between a respective lead and circuitry of the IMD.  
         [0006]     Various connection standards have been developed in order to ensure electrical connections between the IMD circuitry and the lead are acceptable, while also maintaining a sufficient hermetic seal between the connector block and the lead to avoid ingress of body fluids into the housing. These standards continue to evolve to accommodate new lead designs, such as in-line leads that include a plurality of electrical contact areas along axial positions of the lead.  
         [0007]     In general, there remains a need for lead connector configurations that are simple to use and inexpensive to fabricate. Improved simplicity can help ensure that physicians can make the electrical connections during implantation of the IMD with minimal concern for electrical coupling malfunction. Reduced fabrication expense can help ensure that patient costs associated with an IMD can be minimized.  
       SUMMARY  
       [0008]     In one embodiment, the invention provides an electrical connector clip for coupling a medical lead to circuitry of a medical device. The clip may comprise a first sidewall, a second sidewall, and an endwall attaching a first end of the first sidewall to a first end of the second sidewall such that the clip forms a substantially U-shaped configuration. A second end of the first side wall and a second end of the second sidewall may be spring biased toward one another. A protrusion may be formed on inner surfaces of each of the first and second side walls to facilitate electrical coupling to a medical lead upon positioning of the medical lead within the U-shape.  
         [0009]     In another embodiment, the invention provides a connector block for an implantable medical device. The connector block may include a structure formed with a channel, the structure defining an access hole to the channel and a ridge formed in the access hole to provide a biasing mechanism for U-shaped electrical connector clip. The connector block may further include the substantially U-shaped electrical connector clip in the access hole to electrically couple to a medical lead upon insertion of the medical lead into the channel. The U-shaped electrical connector clip may be biased open by the ridge prior to the insertion of the medical lead.  
         [0010]     In another embodiment, the invention provides an assembly that includes a structure formed with a channel, and a medical lead positioned in the channel. The structure may define an access hole to the channel and a ridge formed in the access hole. The assembly may further include a substantially U-shaped electrical connector clip in the access hole to electrically couple to the medical lead.  
         [0011]     In another embodiment, the invention provides an implantable medical device. The implantable medical device may comprise a housing, circuitry within the housing and a connector block connected to the housing and including a structure formed with a channel, the structure defining an access hole to the channel and a spring bias ridge formed in the access hole. The implantable medical device may further include a medical lead in the channel, and a substantially U-shaped electrical connector clip in the access hole to electrically couple the medical lead to the circuitry.  
         [0012]     In another embodiment, the invention provides a method that comprises inserting substantially U-shaped electrical connectors into holes of a lead connecting structure such that the U-shaped electrical connectors are biased open by ridges formed in the holes of the structure, and inserting a medical lead through a channel of the structure such that the lead passes through the U-shaped electrical connectors making electrical contact between the medical lead and the U-shaped electrical connectors.  
         [0013]     The invention may be capable of providing a number of advantages. For example, the invention may improve and simplify electrical connections between implantable leads and circuitry of an implantable medical device. In particular, the invention may find useful application in in-line medical lead systems that use leads having multiple electrical contacts along axial positions of the respective leads. In that case, the invention may reduce size constraints of electrical contacts in an IMD, allowing electrical contact areas to be positioned on the lead in closer spatial proximity.  
         [0014]     In addition, the invention may improve medical procedures, allowing physicians to make the electrical connections during implantation if the IMD with minimal concern for electrical coupling malfunction. The invention may also reduce costs associated with IMD fabrication, which can help minimize patient costs associated with an IMD.  
         [0015]     Additional details of various embodiments are set forth in the accompanying drawings and the description below. Other features, objects and advantages will become apparent from the description and drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0016]     Advantages and features of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein:  
         [0017]      FIG. 1  is a perspective view of an exemplary implantable medical device capable of incorporating a connector assembly according to the present invention;  
         [0018]      FIG. 2  is an exploded perspective view of components of a connector assembly of an implantable medical device according to the present invention;  
         [0019]      FIG. 3  is a cross-sectional side view of components of a connector assembly of an implantable medical device according to the present invention;  
         [0020]      FIG. 4  is a top view of components of the connector assembly of  FIG. 3 ;  
         [0021]      FIG. 5  is a perspective view of an electrical connector clip for coupling a medical lead to circuitry of an implantable medical device according to the present invention;  
         [0022]      FIG. 6  is a front view of the electrical connector clip of  FIG. 5  in a non-biased or preloaded position prior to insertion in a portion of a connector block of an implantable medical device;  
         [0023]      FIG. 7  is a front view of the electrical connector clip of  FIG. 5  in a pre-biased or pre-loaded position following full insertion of the connector clip within a portion of a connector block of an implantable medical device;  
         [0024]      FIG. 8A  is a cross-sectional front view of components that form a portion of a connector block of an implantable medical device, according to the present invention, with a connector clip inserted prior to insertion of a medical lead within the connector block;  
         [0025]      FIG. 8B  is a cross-sectional front view of the components of  FIG. 8A  following insertion of a medical lead within the connector block;  
         [0026]      FIG. 9  is a perspective view of an electrical connector clip for coupling an implantable medical lead to circuitry of an implantable medical device according to the present invention;  
         [0027]      FIG. 10  is a front view of the electrical connector clip of  FIG. 9  prior to insertion within a connector block of an implantable medical device;  
         [0028]      FIG. 11  is a front view of the electrical connector clip of  FIG. 9  following insertion within a connector block of an implantable medical device;  
         [0029]      FIG. 12  is a cross-sectional top view of a portion of a connector block of an implantable medical device according to the present invention; and  
         [0030]      FIGS. 13 and 14  are exemplary perspective views of components of a connector assembly of an implantable medical device according to alternate embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     The present invention is directed to an electrical connector assembly for facilitating electrical connection between a medical lead and circuitry of an implantable medical device (IMD), and implantable medical devices employing such a connector assembly. For example, an improved connector clip that forms a conductive interface between a medical lead and IMD circuitry is described. Various components that assemble with the connector clip to form at least a portion of a connector block of an IMD are also described.  FIG. 1  is a perspective view of an exemplary implantable medical device capable of incorporating a connector assembly according to the present invention. As illustrated in  FIG. 1 , an exemplary implantable medical device (IMD)  1  incorporating a connectory assembly according to the present invention includes a hermetically sealed, biologically inert housing  5 , or “can”, that houses IMD circuitry, one or more leads  2 A,  2 B that can be implanted in a patient, and a connector block  7  that receives proximal ends  9 A,  9 B of leads  2  to couple leads  2  to the circuitry in housing  5  as leads  2  are inserted within a connector port  20  formed in connector block  7 . Once fully inserted within connector block  7 , leads  2  are fixedly positioned within connector block  7  by tightening positioning screws  11  against leads  2 .  
         [0032]     As illustrated in  FIG. 1 , the proximal ends  9 A and  9 B of lead  2 A and  2 B include a plurality of electrical contact areas  8 A- 8 J (collectively contact areas  8 ). The present invention facilitates electrical coupling to one or more of contact areas  8  within connector block  7 . Moreover, the present invention improves such contact for inline configurations like  FIG. 1  in which a plurality of electrical contact areas  8  are positioned axially along a length of leads  2 . In particular, the present invention allows size reductions of contact areas  8  by improving electrical coupling clips, described below, that electrically interface with contact areas  8  inside connector block  7 .  
         [0033]     IMD  1  corresponds to any medical device that includes medical leads and circuitry coupled to the medical leads. By way of example, IMD  1  takes the form of an implantable cardiac pacemaker that provides therapeutic stimulation to the heart. Alternatively, IMD  1  may take the form of an implantable cardioverter or an implantable defibrillator, or an implantable cardiac pacemaker-cardioverter-defibrillator. IMD  1  may deliver pacing, cardioversion or defibrillation pulses to a patient via electrodes disposed on distal ends of leads  2 . In other words, leads  2  position electrodes with respect to various cardiac locations so that IMD  1  can deliver pulses to the appropriate locations.  
         [0034]     Alternatively, IMD  1  corresponds to a patient monitoring device, or a device that integrates monitoring and stimulation features. In those cases, leads  2  include sensors positioned along distal ends of the respective lead for sensing patient conditions. The sensors include, for example, electrical sensors, electrochemical sensors, pressure sensors, flow sensors, acoustic sensors, optical sensors, or the like. In many cases, IMD  1  performs both sensing and stimulation functions.  
         [0035]     In still other applications, IMD  1  corresponds to a neurological device such as a deep-brain stimulation device or a spinal cord stimulation device. In those cases, leads  2  are stereotactically probed into the brain to position electrodes for deep brain stimulation, or into the spine for spinal stimulation. In other applications, IMD  1  provides muscular stimulation therapy, blood sensing functions, and the like. In short, IMD  1  corresponds to any of a wide variety of medical devices that implement leads and circuitry coupled to the leads.  
         [0036]     As outlined in detail below, connector block  7  of the present invention incorporates various components that improve and simplify electrical coupling between leads  2  and circuitry in housing  5 . More specifically, an electrical connector clip provides a conductive interface between a medical lead and IMD circuitry. In addition, various components that assemble with the connector clip to form at least a portion of connector block  7  of IMD  1  are also described. For example, an improved structure having a channel for mating with one or more of leads  2  is designed for use with the connector clip so that biasing of the connector clip can be achieved prior to insertion of one or more leads  2  into the channel. As described below, such biasing allows for ease of insertion of one or more of leads  2  into the channel of the structure that forms at least part of connector block  7 . In other words, the connector clip defines a desired amount of insertion force for lead pins inserted into connector block  7 .  
         [0037]      FIG. 2  is an exploded perspective view of components of a connector assembly of an implantable medical device according to the present invention. In particular, according to the present invention a portion  27  of connector block  7  includes connector port  20 , formed along a front end  23  of connector block  7  that is in fluid communication with a channel  21  formed therein for receiving a medical lead. Channel  21  extends from connector port  20  to a back end  25  ( FIGS. 3 and 4 ), so that leads  2  are received within channel  21  of connector block  7  when inserted within connector port  20 . A connector clip aperture  22  is formed along portion  27  of connector block  7  for insertably receiving an electrical connector clip  24 . Aperture  22  provides side access to channel  21  for insertion of connector clip  24 , and is sized to receive and position electrical connector clip  24  within connector block  7  so that electrical connector clip  24  electrically interfaces with contact areas  8  of leads  2  when leads  2  are inserted within channel  21  via connector port  20 . In addition, a fluid sealing aperture  26  is formed along portion  27  of connector block  7  for insertably receiving a fluid seal  28 . Similar to aperture  22 , aperture  26  provides side access to channel  21  for insertion of fluid seal  28 , and is sized to receive and position fluid seal  28  within connector block  7 . Fluid seal  28  is generally cylindrical in shape and forms a through hole  30  for sealably receiving a medical lead inserted within channel  21  via connector port  20  of connector block  7  when seal  28  is inserted within aperture  26 .  
         [0038]     In operation, one or more of proximal ends  9 A and  9 B of leads  2  are inserted within channel  21  via connector port  20  and advanced through fluid seal  28  inserted within sealing hole  26 . Fluid seal  28  is deformable and exerts sealing force against the circumference of proximal ends  9 A and  9 B of leads  2  between contact areas  8  to provide a fluid seal around leads  2 . Proximal ends  9 A,  9 B extend into channel  21  so that contact areas  8  are brought into alignment with connector clip  24 , which creates an electrical interconnection between contact areas  8  and circuitry within connector block  7 .  
         [0039]     The components illustrated in  FIG. 2  provide a number of advantages. For example, because electrical connector clip  24  is oriented perpendicular to proximal ends  9 A and  9 B when inserted within channel  21 , successive electrical connections can be placed close to one another. In other words, the pitch or “spacing” between adjacent electrodes disposed axially along the lead tip can be reduced, permitting an increased density of electrical interconnections. Accordingly, this feature is particularly useful for in-line lead systems, i.e., systems in which the medical lead includes a number of electrical contacts disposed along axial positions of the lead. In that case, connector block  7  could include a number of connector clip apertures  22  and fluid seal apertures  26  in an alternating configuration.  FIGS. 7 and 8  illustrate two such examples and are described below.  
         [0040]     Another advantageous feature of connector block  7  according to the present invention is a generally rectangular shaped ridge  29  that is formed within access hole  22 . In particular, ridge  29  simplifies insertion of electrical connector clip  24  into hole  22 , and facilitates spring biasing of electrical connector clip  24  upon insertion. Ridge  29  tends to bias clip  24  outward to accommodate insertion of proximal end  9 A,  9 B of leads  2  within clip  24  with reduced insertion force. Additional details of the advantages of one or more ridges are described in detail below with reference to  FIGS. 8A and 8B .  
         [0041]     In accordance with various embodiments, connector clip aperture  22  and fluid seal aperture  26  may be oriented in any direction along the relevant portion of connector block  7 . For example, connector block  7  may be oriented so that apertures  22 ,  26  are positioned along the top of connector block  7 , or along the bottom of connector block  7 . In the later case, electrical connector clip  24  would be oriented such that a top contact surface of electrical connector clip  24  faced down for electrical coupling to the circuitry in housing  5 .  
         [0042]      FIG. 3  is a cross-sectional side view of components of a connector assembly of an implantable medical device according to the present invention.  FIG. 4  is a top view of components of the connector assembly of  FIG. 3 . As shown in  FIGS. 3 and 4 , channel  21  is formed through a portion of connector block  7  to define a path for receiving medical lead  2 A or  2 B. Electrical connector clip  24  is positioned within aperture  22  for electrical coupling to contact areas  8  of one of lead  2 A,  2 B, and seal  28  is positioned within aperture  26  for sealing leads  2  when inserted within channel  21  of connector block  7 . Both connector clip  24  and seal  28  are positioned within connector block  7  so as to be perpendicular to proximal end  9 A,  9 B of lead  2 A or  2 B when lead  2 A or  2 B is inserted within channel  21  of connector block  7  via connector port  20 .  
         [0043]      FIG. 5  is a perspective view of an electrical connector clip for coupling a medical lead to circuitry of an implantable medical device according to the present invention.  FIG. 6  is a front view of the electrical connector clip of  FIG. 5  in a non-biased or preloaded position prior to insertion in a portion of a connector block of an implantable medical device, and  FIG. 7  is a front view of the electrical connector clip of  FIG. 5  in a pre-biased or pre-loaded position following full insertion of the connector clip within a portion of a connector block of an implantable medical device.  
         [0044]     As described above, electrical connector clip  24  is used for coupling a medical lead  2 A or  2 B to circuitry contained within housing  5  of implantable medical device  10 . As illustrated in  FIGS. 5-7 , electrical connector clip  24  includes a first sidewall  91 , a second sidewall  92 , and an endwall  93  extending between a first end of first sidewall  91  to a first end of second sidewall  92  such that connector clip  24  forms a substantially U-shaped configuration with a second end  95  of first side wall  91  and a second end  96  of second sidewall  92  being spring biased toward one another. Electrical connector  90  may also include protrusions  94 A,  94 B formed on respective inner surfaces of each of first and second side walls  91 ,  92 . In particular, protrusions  94 A,  94 B can be formed to facilitate electrical coupling to the medical lead upon positioning of the medical lead within the U-shape of connector clip  24 .  
         [0045]     An outer surface of endwall  93  may define a location for welding a wire that couples to circuitry of the IMD (such as illustrated in  FIGS. 8A and 8B ). Protrusions  94 A,  94 B each define an electrical coupling surface offset from a major inner surface of the first and second side walls  91 ,  92 . In other words, the surface of protrusions  94 A,  94 B defines electrical contact points for coupling to a medical lead.  
         [0046]      FIG. 8A  is a cross-sectional front view of components that form a portion of a connector block of an implantable medical device, according to the present invention, with a connector clip inserted prior to insertion of a medical lead within the connector block.  FIG. 8B  is a cross-sectional front view of the components of  FIG. 8A  following insertion of a medical lead within the connector block. As illustrated in  FIGS. 8A and 8B , portion  27  of connector block  7  defines channel  21  within which medical lead  2 A or  2 B is inserted. Electrical connector clip  24  is positioned within aperture  22  and seal  28  is positioned within aperture  26  (not shown in  FIGS. 8 and 8 B) of portion  27  of connector block  7  prior to insertion of lead  2 A or  2 B within channel  21 , as described above. Upper ridge  29  defines a guide path to simplify insertion of electrical connector clip  24  by directing and spring biasing electrical connector clip  24  when connector clip  24  is inserted within aperture  22 . Lower ridge  32  defines a biased position of electrical connector clip  24  prior to insertion of lead  2 A or  2 B. If desired, lower ridge  32  and/or upper ride  29  can include a slight taper  33  to simplify insertion of electrical connector clip  24  within aperture  22 .  
         [0047]     This spring bias defined by lower ridge  32  brings electrical connector clip  24  into a spring force range that is desirable for insertion of a lead  2 A or  2 B into channel  21  ( FIG. 2 ). In other words, ridge  32  functions to bias electrical connector clip  24  into a position in which subsequent insertion of a medical lead into channel  21  causes slight residual spring-forced opening of electrical connector clip  24 . This residual spring-forced opening of electrical connector clip  24  may be specifically defined for desired resistance of the insertion of a medical lead into channel  21  while ensuring adequate electrical contact pressure between clip  24  and a corresponding electrode carried by the lead with minimal motion of sidewalls  91 ,  92  of clip  24 . Accordingly, the present invention enables a physician to insert a medical lead within channel  21  with less insertion force and less concern for electrical coupling malfunction.  
         [0048]     The use of lower ridge  32  to bias electrical connector clip  24  may also achieve a relatively high electrical contact force between electrical connector clip  24  and an inserted lead, with minimized residual movement of side walls  91 ,  92  of electrical connector clip  24  upon insertion of the lead. As further illustrated in  FIG. 8B , a small gap exists between electrical connector clip  24  and lower ridge  32  following insertion of medical lead  31  because electrical connector clip  24  is biased open by lead  31 . Accordingly a good electrical interface between electrical connector clip  24  and lead  31  can be ensured.  
         [0049]     In particular, according to the present invention, prior to insertion within portion  27  of connector block  7 , connector clip  24  is in the non-biased or preloaded position, as illustrated in  FIG. 6 . The non-biased connector clip  24  is inserted within aperture  22  so that an upper portion  38  of ridge  29  is advanced between inner walls  97  of sidewalls  91 ,  92  so that end  95  and end  96  follow side walls  39  of ridge  29  as connector clip  24  is advanced within aperture  22 . The distance between ends  95  and  96  of sidewalls  91 ,  92  is then further increased as ends  95  and  96  are advance along taper  33  of lower ridge  32  and further along side walls  40  of lower ridge  32  until connector clip  24  is fully advanced within aperture  22 , with lower ridge  32  placing connector clip  24  in the biased or preloaded position, as illustrated in  FIGS. 7 and 8 A. As can be seen in  FIG. 8A , once connector clip  24  is fully inserted in aperture  22  to be in the biased or pre-loaded position, protrusions of sidewalls  91 ,  92  project over channel  21  to provide contact points that come in contact with lead  2 A or  2 B when lead  2 A or  2 B is inserted within channel  21  and which define electrical contact points for coupling to medical lead  2 A or  2 B when fully inserted within connector block  7 .  
         [0050]     As illustrated in  FIG. 8B , subsequent advancement of medical lead  2 A or  2 B within channel  21  causes further residual spring-forced opening of electrical clip  24  so that the distance between ends  95 ,  96  of respective sidewalls  91 ,  92  is further increased from the distance between ends  95 ,  96  when connector clip  24  is in the biased or pre-loaded position of  FIGS. 7 and 8 A. As a result, ends  95 ,  96  are no longer in contact with ridge  32 , but rather extend outward from side walls  40  of lower ridge  32 , transferring all of the spring-force of biased connector clip  24  toward proximal end  9 A or  9 B of lead  2 A or  2 B to fixedly position lead  2 A or  2 B within connector block  7  and ensure electrical contact pressure between connector clip  24  and a corresponding one of contact areas  8 .  
         [0051]     As illustrated in  FIGS. 8A and 8B , end wall  93  of electrical connector clip  24 , e.g., the surface connecting the two side-walls  91 ,  92  of generally U-shaped electrical connector clip  24 , defines a welding surface. Accordingly, an electrical wire  34  can be welded via weld  35  to electrical connector clip  24  to facilitate connection to electrical components of IMD  1 . Portion  27  of connector block  7  then defines a conduit  37  through which electrical wire  34  passes. An end  36  of wire  34  is coupled to circuitry of IMD  1 . A sealing compound, such as silicone, an epoxy or the like, can then be placed over aperture  22  to seal clip  24  and wire  34  within portion  27  of connector block  7 .  
         [0052]      FIG. 9  is a perspective view of an electrical connector clip for coupling an implantable medical lead to circuitry of an implantable medical device according to the present invention.  FIG. 10  is a front view of the electrical connector clip of  FIG. 9  prior to insertion within a connector block of an implantable medical device, and  FIG. 11  is a front view of the electrical connector clip of  FIG. 9  following insertion within a connector block of an implantable medical device. In particular,  FIGS. 9-11  illustrate a slight modification of the electrical connector clip  90  illustrated in  FIGS. 5-7 , which can further improve insertion of a medical lead.  
         [0053]     Like connector clip  24 , a connector clip  120  according to an embodiment of the present invention includes a first sidewall  121 , a second sidewall  122 , and an endwall  123  attaching a first end of first sidewall  121  to a first end of second sidewall  122  such that clip  120  forms a substantially U-shaped configuration with an end  195  of first side wall  121  and an end  196  of second sidewall  122  being spring biased toward one another when connector clip  120  is in a non-biased, preloaded position, illustrated for example in  FIG. 10 , prior to insertion of connector clip  120  within aperture  22  of portion  27  of connector block  7 . Also, electrical connector  120  includes protrusions  124 A,  124 B formed on inner surfaces of each of first and second side walls  121 , which are formed to facilitate electrical coupling to the medical lead upon positioning of the medical lead within the U-shape connector clip  120 .  
         [0054]     Also similar to connector clip  24 , in connector clip  120 , an outer surface of endwall  123  defines a location for welding a wire that couples to circuitry of the IMD (such as illustrated in  FIGS. 8A and 8B ). Protrusions  124 A,  124 B each define an electrical coupling surface offset from a major inner surface the of the first and second side walls  121 ,  122 .  
         [0055]     Unlike connector clip  24 , however, protrusions  124 A,  124 B of clip  120  each define a tapered region  128  between the respective major inner surface of sidewall  121  or  122  and the electrical coupling surface of the respective protrusion  124 A or  124 B. In particular, region  128  is tapered to facilitate gradual opening of connector clip  120  during insertion of the medical lead through connector clip  120  in a direction perpendicular to connector clip  120 . As lead is inserted through connector clip  120 , proximal end  9 A or  9 B comes in contact with and advances within connector clip  120  along tapered region  128  and advances over an upper surface  129  of protrusion  124 A and  124 B as lead  2  is further advanced through connector clip  120 . In this way, tapered region  128  of connector clip  120  improves the functionality of connector clip  120  by reducing the force required for insertion of a medical lead through connector clip  120  and therefore through channel  21  as outlined above. With the inclusion of tapered region  128  on clip  120 , a physician can insert the medical lead with greater ease, but the contact force between the lead and electrical contact surfaces of protrusions  124 A,  124 B after insertion of a lead is unchanged from that of the electrical contact clip illustrated in  FIGS. 5-7 .  
         [0056]     By way of example, first sidewall  121 , second sidewall  122  and endwall  123  may be integrally formed of a continuous material. A metal may be used to ensure good conductivity, and a biocompatible metal is generally preferred since the clip  120  forms part of an implantable medical device. Suitable materials for creating clip  120  of  FIGS. 12-14  or clip  90  of  FIGS. 9-11  may include stainless steals, MP35N, titanium alloys, platinum alloys, or any suitable metal with a correct balance of stiffness, strength, and surface oxided characteristics.  
         [0057]      FIG. 12  is a cross-sectional top view of a portion of a connector block of an implantable medical device according to the present invention. As illustrated in  FIG. 12 , a plurality of connector clip apertures  22 A- 22 C for receiving a plurality of connector clips  24 ,  120  and a plurality fluid seal apertures  26 A- 26 D for receiving seals  28 A- 28 D can be defined in portion  27  of connector block  7 . In particular, apertures  22 A- 22 C for receiving electrical connector clips and apertures  26  for receiving seals are arranged in an alternating configuration so that each respective seal can separate consecutive electrical connector clips inserted into consecutive apertures  22 A- 22 C.  
         [0058]     As further illustrated in  FIG. 12 , portion  27  of connector block  7  is formed to receive a set screw  63 . Upon insertion of a medical lead  64  within channel  21  to a desired location, set screw  63  can be inserted to secure medical lead  64  in a final position.  
         [0059]     As mentioned above, one advantage of the electrical connector clip described herein is the perpendicular orientation of the electrical connector clip relative to channel  21 . Such perpendicular orientation can help reduce the distance between successive electrical contact points of lead  64 , which is particularly useful for in-line lead systems. In particular, as illustrated in  FIG. 12 , use of the described electrical connector clips reduces a pitch (P) to less than approximately 20 millimeters between electrical contacts.  
         [0060]      FIGS. 13 and 14  are exemplary perspective views of components of a connector assembly of an implantable medical device according to alternate embodiments of the present invention. In particular, as illustrated in  FIG. 13 , portion  27  of connector block  7  includes a single row of alternating connector clip apertures  22 A- 22 C for receiving connector clips  24 ,  120  and fluid seal apertures  26 A- 26 C for receiving seals  28 , as described herein. Also, each of apertures  22 A- 22 C include ridge  29  and  32  as described herein to reduce (or possibly increase) insertion force of electrical connector clips into the respective access holes, and to bias the electrical connector clips in order to achieve a desired degree of insertion force for a lead inserted into channel  21 .  
         [0061]     As illustrated in  FIG. 14 , portion  27  of connector block  7  may also be formed with a plurality of channels  81 ,  82  so that more than one lead can be inserted within connector block  7 . In the example of  FIG. 14 , each channel  81 ,  82  includes a plurality of connector clip apertures  83 A- 83 F, each sized to receive electrical connector clip  24 ,  120  as described herein to bias the electrical connector clips in order to achieve a desired resistance for insertion of a lead into channel  81 .  
         [0062]     The present invention improves and simplifies electrical connections between implantable leads and circuitry of an implantable medical device. In particular, the present invention may find useful application in in-line medical lead systems that use leads having multiple electrical contacts along axial positions of the respective leads. In that case, the present invention reduces size constraints of electrical contacts in an IMD, allowing electrical contact areas to be positioned on the lead in closer spatial proximity.  
         [0063]     In addition, the present invention improves medical procedures, allowing physicians to make the electrical connections during implantation if the IMD with minimal concern for electrical coupling malfunction. The invention also reduces costs associated with IMD fabrication, which can help minimize patient costs associated with an IMD.  
         [0064]     While particular embodiments of the present invention have been shown and described, modifications may be made. It is therefore intended in the appended claims to cover all such changes and modifications, which fall within the true spirit and scope of the invention.