Abstract:
A flat ribbon cable for interconnecting electrical components mounted in mating clamshell enclosure halves of an implantable cardiac stimulation device. The ribbon cable is configured to butterfly open when the enclosure is opened and interconnect components in each half without undergoing undue mechanical stress as the halves are distanced. The ribbon cable is also configured to fold together when the enclosure halves are mated together, without bending, in a very compact manner so as to occupy minimal room in the enclosure when the device is ready for implantation thus preserving more room for batteries, capacitors, and other electrical devices providing the sensing and stimulation functions of the device and/or allowing the overall space envelope of the stimulation device to be reduced.

Description:
FIELD OF THE INVENTION 
   The present invention relates to the field of implantable medical devices, such as pacemakers and intra-cardioverter defibrillators (ICD&#39;s) and, in particular, to a flexible electrical interconnect of such a configuration as to reliably interconnect two components in a low profile manner. 
   BACKGROUND OF THE INVENTION 
   Implantable medical devices are being used increasingly to monitor and assist functioning of the patient&#39;s organs. These types of devices includes cardiac stimulation devices e.g., pacemakers and ICDs, as well as insulin pumps and other mechanical devices. These devices are increasingly complicated thereby requiring increasingly complicated circuitry to be implanted in a casing within the body. Implanted devices are more convenient for the patient as an implanted device reduces the need for the patient to wear and accommodate an external device in their daily life. 
   Implantable devices, such as implantable cardiac stimulation devices, typically include a variety of electronic components such as batteries, sensing and stimulation circuits, microprocessors/controllers, and capacitors contained within a biocompatible enclosure. The enclosure is often made up of two clamshell halves which can be hingedly attached. The electrical components must generally be secured to a substrate such that the electrical components are secured to accommodate the movement of the implantable device when implanted within the patient. Consequently, when the casing is comprised of two clam shell halves, the electrical components are often secured to the interior surfaces of both of the clam shell halves. Both halves typically hold electrical components and the clamshell enclosures are typically positioned in an open configuration during manufacture or service of the device. Once the device is completed and ready for implantation, the clamshell halves are typically closed so as to be adjacent each other and essentially parallel. The clamshell halves form a hermetic seal in the closed position to exclude body fluids from the device electronics. 
   Many implantable medical devices, such as cardiac stimulation devices, are preferably as small as possible in order to minimize impact on the patient. The larger the casing, the more uncomfortable the implanted device is for the patient. The control, sensing, and stimulation circuitry, as well as the power supply, take up a considerable amount of room in the device enclosure. It is for these reasons that electrical components are typically installed in both halves of a clamshell enclosure. The electrical components in each clamshell half must typically be interconnected with electrical components in the opposing half. This imposes a requirement for an electrical interconnection that interconnects the various components in both halves with the enclosure in both the open and closed configuration. 
   Several methods are known in the art for interconnecting components in a plurality of relative positions. Slidable contacts, such as slip rings, are known to provide electrical contact throughout a range of sliding or rotational movement. However, slidable contacts are prone to corrosion at contact surfaces which can increase impedance and reduce signal transmission. In addition, slidable contacts, capable of conducting the relatively high voltage shocks that many implantable cardiac stimulation devices provide, tend to be large and occupy an undesirably large amount of the interior volume of the device. 
   Flat, straight ribbon cable is another known device for maintaining electrical contact between two electrical assemblies in relative motion. However, ribbon cable of known configurations is problematic with implantable medical devices as described above. In particular, the adjacent placement of the two clamshell halves in the closed position forces the ribbon cable into a tight bend such that the ribbon cable folds on itself. This places mechanical stress on the conductors and insulating material of the ribbon cable. This stress can compromise the electrical insulating ability of the insulation and lead to shorting and cross-talk between individual conductors of the cable. Further, sharp bends and other mechanical stresses can also result in the conductors breaking. In addition, the ribbon cable can only bend on itself to a limited radius and this bend or fold occupies an undesirably large interior volume in the device. 
   With most implantable medical devices and, in particular, implantable cardiac stimulation devices, the potential risks of conductors that are corroded or damaged as a result of the manner in which electrical components in each of the halves are interconnected is quite high. Electrical components may become disconnected potentially rendering the device inoperable. Consequently, many devices have made greater space allowances for electrical interconnect conductors which thereby either increases the size of the implantable medical device or decreases the available space for other necessary electrical components. 
   From the foregoing it will be appreciated that there is a continuing need in the implantable medical device field for an interconnection mechanism that reliably interconnects electrical components contained in opposing enclosure halves both in an open configuration and in a closed configuration as well as while moving between the two in a low profile fashion. The interconnection mechanism should not be under undue mechanical stress in either the open or closed configurations. There is a further need for an electrical interconnect that is durable and is not subject to the contact corrosion problems of slip-ring type contacts. 
   SUMMARY OF THE INVENTION 
   The aforementioned needs are satisfied by the casing of the present invention which, in one aspect, comprises a first and second enclosure halves each defining an interior space that retains a first and a second plurality of electrical components respectively. The casing further includes an electrical interconnect cable assembly that has a plurality of conductors surrounded by insulation. The plurality of conductors are preferably insulated from each other by the electrical interconnect cable and the plurality of conductors electrically interconnect the first plurality of electrical components with the second plurality of electrical components. 
   The electrical interconnect cable is preferably configured such that when the first and second enclosure halves are positioned together, the plurality of conductors each have a first and a second leg that extend in directions that are substantially parallel to each other in at least one plane. Moreover, the electrical interconnect cable is also preferably configured such that the first and second legs of each of the conductors are interconnected by a transverse section that extends in a direction transverse to the parallel directions of the first and second legs in the at least one plane. 
   Consequently, the electrical interconnect cable is preferably assembled such that the first and second legs can be positioned side-by-side in at least one plane so as to reduce the overall thickness of the electrical interconnect assembly. Moreover, due to the addition of the transverse section interconnecting the legs, allows for a change of direction of up to 180 degrees between the first and second legs to be accomplished in two smaller changes of direction thereby reducing the stress on the plurality of conductors within the electrical interconnect cable. 
   The first and second legs of the electrical interconnect cable are preferably flexible such that when the first and second enclosure halves are positioned in an open, side-by-side configuration, the first and second legs extend laterally outward from the transverse section. The first and second legs thereby extend laterally between the first and second enclosure halves when the first and second enclosure halves are in the open configuration thereby keeping the first and second plurality of electrical components interconnected. 
   Hence, the casing of the present invention allows for the interconnection between electrical components mounted in a two enclosure halves in a manner that does not require sharp bends in the conductors and also does not require the conductors to be stacked on top of each other. Hence, the electrical interconnection is thus both more reliable and consumes less space within the closed enclosure while still permitting the electrical components to remain interconnected when the enclosure halves are separated. These and other objects and advantages will be more apparent from the following description taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the present invention may be more readily understood by reference to the following description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a simplified diagram illustrating an implantable stimulation device in electrical communication with at least three leads implanted into a patient&#39;s heart for delivering multi-chamber stimulation and shock therapy; 
       FIG. 2  is a functional block diagram of a multi-chamber implantable stimulation device illustrating the basic elements of a stimulation device which can provide cardioversion, defibrillation and pacing stimulation in four chambers of the heart; 
       FIG. 3  is a top view of a cardiac device provided with a flexible electrical interconnect in an open position; 
       FIG. 4  is a perspective cutaway view of a cardiac device provided with one embodiment of a flexible electrical interconnect in the closed or implantation ready state; and 
       FIG. 5  is a perspective cutaway view of a cardiac device provided with one embodiment of a flexible electrical interconnect in an open position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The following description is of the best mode 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. 
   As shown in  FIG. 1 , there is a stimulation device  10  in electrical communication with a patient&#39;s heart  12  by way of three leads,  20 ,  24  and  30 , suitable for delivering multi-chamber stimulation and shock therapy. To sense atrial cardiac signals and to provide right atrial chamber stimulation therapy, the stimulation device  10  is coupled to an implantable right atrial lead  20  having at least an atrial tip electrode  22 , which typically is implanted in the patient&#39;s right atrial appendage. 
   To sense left atrial and ventricular cardiac signals and to provide left chamber pacing therapy, the stimulation device  10  is coupled to a “coronary sinus” lead  24  designed for placement in the “coronary sinus region” via the coronary sinus os for positioning a distal electrode adjacent to the left ventricle and/or additional electrode(s) adjacent to the left atrium. As used herein, the phrase “coronary sinus region” refers to the vasculature of the left ventricle, including any portion of the coronary sinus, great cardiac vein, left marginal vein, left posterior ventricular vein, middle cardiac vein, and/or small cardiac vein or any other cardiac vein accessible by the coronary sinus. 
   Accordingly, an exemplary coronary sinus lead  24  is designed to receive atrial and ventricular cardiac signals and to deliver left ventricular pacing therapy using at least a left ventricular tip electrode  26 , left atrial pacing therapy using at least a left atrial ring electrode  27 , and shocking therapy using at least a left atrial coil electrode  28 . For a complete description of a coronary sinus lead, see U.S. Pat. No. 5,466,254, “Coronary Sinus Lead with Atrial Sensing Capability” (Helland), which patent is hereby incorporated herein by reference. 
   The stimulation device  10  is also shown in electrical communication with the patient&#39;s heart  12  by way of an implantable right ventricular lead  30  having, in this embodiment, a right ventricular tip electrode  32 , a right ventricular ring electrode  34 , a right ventricular (RV) coil electrode  36 , and a superior vena cava (SVC) coil electrode  38 . Typically, the right ventricular lead  30  is transvenously inserted into the heart  12  so as to place the right ventricular tip electrode  32  in the right ventricular apex so that the RV coil electrode  36  will be positioned in the right ventricle and the SVC coil electrode  38  will be positioned in the superior vena cava. Accordingly, the right ventricular lead  30  is capable of receiving cardiac signals and delivering stimulation in the form of pacing and shock therapy to the right ventricle. 
   As illustrated in  FIG. 2 , a simplified block diagram is shown of the multi-chamber implantable stimulation device  10 , which is capable of treating both fast and slow arrhythmias with stimulation therapy, including cardioversion, defibrillation, and pacing stimulation. While a particular multi-chamber device is shown, this is for illustration purposes only, and one of skill in the art could readily duplicate, eliminate or disable the appropriate circuitry in any desired combination to provide a device capable of treating the appropriate chamber(s) with cardioversion, defibrillation and pacing stimulation. 
   The housing  40  for the stimulation device  10 , shown schematically in  FIG. 2 , is often referred to as the “can”, “case” or “case electrode” and may be programmably selected to act as the return electrode for all “unipolar” modes. The housing  40  may further be used as a return electrode alone or in combination with one or more of the coil electrodes,  28 ,  36  and  38 , for shocking purposes. The housing  40  further includes a connector  120  ( FIGS. 4 and 5 ) having a plurality of terminals,  42 ,  44 ,  46 ,  48 ,  52 ,  54 ,  56 , and  58  (shown schematically and, for convenience, the names of the electrodes to which they are connected are shown next to the terminals). As such, to achieve right atrial sensing and pacing, the connector  120  includes at least a right atrial tip terminal (A R  TIP)  42  adapted for connection to the atrial tip electrode  22 . 
   To achieve left chamber sensing, pacing and shocking, the connector  120  includes at least a left ventricular tip terminal (V L  TIP)  44 , a left atrial ring terminal (A L  RING)  46 , and a left atrial shocking terminal (A L  COIL)  48 , which are adapted for connection to the left ventricular ring electrode  26 , the left atrial tip electrode  27 , and the left atrial coil electrode  28 , respectively. 
   To support right chamber sensing, pacing and shocking, the connector  120  further includes a right ventricular tip terminal (V R  TIP)  52 , a right ventricular ring terminal (V R  RING)  54 , a right ventricular shocking terminal (R V  COIL)  56 , and an SVC shocking terminal (SVC COIL)  58 , which are adapted for connection to the right ventricular tip electrode  32 , right ventricular ring electrode  34 , the RV coil electrode  36 , and the SVC coil electrode  38 , respectively. 
   At the core of the stimulation device  10  is a programmable microcontroller  60  which controls the various modes of stimulation therapy. As is well known in the art, the microcontroller  60  typically includes a microprocessor, or equivalent control circuitry, designed specifically for controlling the delivery of stimulation therapy and may further include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. Typically, the microcontroller  60  includes the ability to process or monitor input signals (data) as controlled by a program code stored in a designated block of memory. The details of the design and operation of the microcontroller  60  are not critical to the present invention. Rather, any suitable microcontroller  60  may be used that carries out the functions described herein. The use of microprocessor-based control circuits for performing timing and data analysis functions are well known in the art. 
   As shown in  FIG. 2 , an atrial pulse generator  70  and a ventricular pulse generator  72  generate pacing stimulation pulses for delivery by the right atrial lead  20 , the right ventricular lead  30 , and/or the coronary sinus lead  24  via an electrode configuration switch  74 . It is understood that in order to provide stimulation therapy in each of the four chambers of the heart  12 , the atrial and ventricular pulse generators  70  and  72  may include dedicated, independent pulse generators, multiplexed pulse generators, or shared pulse generators. The pulse generators  70  and  72  are controlled by the microcontroller  60  via appropriate control signals  76  and  78 , respectively, to trigger or inhibit the stimulation pulses. 
   The microcontroller  60  further includes timing control circuitry  79  which is used to control the timing of such stimulation pulses (e.g., pacing rate, atrio-ventricular (AV) delay, atrial interconduction (A—A) delay, or ventricular interconduction (V—V) delay, etc.) as well as to keep track of the timing of refractory periods, PVARP intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, etc., which is well known in the art. 
   The switch  74  includes a plurality of switches for connecting the desired electrodes to the appropriate I/O circuits, thereby providing complete electrode programmability. Accordingly, the switch  74 , in response to a control signal  80  from the microcontroller  60 , determines the polarity of the stimulation pulses (e.g., unipolar, bipolar, combipolar, etc.) by selectively closing the appropriate combination of switches (not shown) as is known in the art. 
   Atrial sensing circuits  82  and ventricular sensing circuits  84  may also be selectively coupled to the right atrial lead  20 , coronary sinus lead  24 , and the right ventricular lead  30 , through the switch  74  for detecting the presence of cardiac activity in each of the four chambers of the heart  12 . Accordingly, the atrial (ATR. SENSE) and ventricular (VTR. SENSE) sensing circuits  82  and  84  may include dedicated sense amplifiers, multiplexed amplifiers, or shared amplifiers. The switch  74  determines the “sensing polarity” of the cardiac signal by selectively closing the appropriate switches, as is also known in the art. In this way, the clinician may program the sensing polarity independent of the stimulation polarity. 
   Each sensing circuit  82  and  84  preferably employs one or more low power, precision amplifiers with programmable gain and/or automatic gain control, bandpass filtering, and a threshold detection circuit, as known in the art, to selectively sense the cardiac signal of interest. The automatic gain control enables the device  10  to deal effectively with the difficult problem of sensing the low amplitude signal characteristics of atrial or ventricular fibrillation. The outputs of the atrial and ventricular sensing circuits  82  and  84  are connected to the microcontroller  60  which, in turn, are able to trigger or inhibit the atrial and ventricular pulse generators  70  and  72 , respectively, in a demand fashion in response to the absence or presence of cardiac activity in the appropriate chambers of the heart  12 . 
   For arrhythmia detection, the device  10  utilizes the atrial and ventricular sensing circuits  82  and  84  to sense cardiac signals to determine whether a rhythm is physiologic or pathologic. As used herein “sensing” is reserved for the noting of an electrical signal, and “detection” is the processing of these sensed signals and noting the presence of an arrhythmia. The timing intervals between sensed events (e.g., P-waves, R-waves, and depolarization signals associated with fibrillation which are sometimes referred to as “F-waves” or “Fib-waves”) are then classified by the microcontroller  60  by comparing them to a predefined rate zone limit (i.e., bradycardia, normal, low rate VT, high rate VT, and fibrillation rate zones) and various other characteristics (e.g., sudden onset, stability, physiologic sensors, and morphology, etc.) in order to determine the type of remedial therapy that is needed (e.g., bradycardia pacing, anti-tachycardia pacing, cardioversion shocks or defibrillation shocks, collectively referred to as “tiered therapy”). 
   Cardiac signals are also applied to the inputs of an analog-to-digital (A/D) data acquisition system  90 . The data acquisition system  90  is configured to acquire intracardiac electrogram signals, convert the raw analog data into a digital signal, and store the digital signals for later processing and/or telemetric transmission to an external device  102 . The data acquisition system  90  is coupled to the right atrial lead  20 , the coronary sinus lead  24 , and the right ventricular lead  30  through the switch  74  to sample cardiac signals across any pair of desired electrodes. 
   The microcontroller  60  is further coupled to a memory  94  by a suitable data/address bus  96 , wherein the programmable operating parameters used by the microcontroller  60  are stored and modified, as required, in order to customize the operation of the stimulation device  10  to suit the needs of a particular patient. Such operating parameters define, for example, pacing pulse amplitude, pulse duration, electrode polarity, rate, sensitivity, automatic features, arrhythmia detection criteria, and the amplitude, waveshape and vector of each shocking pulse to be delivered to the patient&#39;s heart  12  within each respective tier of therapy. 
   Advantageously, the operating parameters of the implantable device  10  may be non-invasively programmed into the memory  94  through a telemetry circuit  100  in telemetric communication with the external device  102 , such as a programmer, transtelephonic transceiver, or a diagnostic system analyzer. The telemetry circuit  100  is activated by the microcontroller by a control signal  106 . The telemetry circuit  100  advantageously allows intracardiac electrograms and status information relating to the operation of the device  10  (as contained in the microcontroller  60  or memory  94 ) to be sent to the external device  102  through an established communication link  104 . 
   In the preferred embodiment, the stimulation device  10  further includes a physiologic sensor  108 , commonly referred to as a “rate-responsive” sensor because it is typically used to adjust pacing stimulation rate according to the exercise state of the patient. However, the physiological sensor  108  may further be used to detect changes in cardiac output, changes in the physiological condition of the heart  12 , or diurnal changes in activity (e.g., detecting sleep and wake states). Accordingly, the microcontroller  60  responds by adjusting the various pacing parameters (such as rate, AV Delay, V—V Delay, etc.) at which the atrial and ventricular pulse generators  70  and  72  generate stimulation pulses. 
   The stimulation device additionally includes a battery  110  which provides operating power to all of the circuits shown in  FIG. 2 . For the stimulation device  10 , which employs shocking therapy, the battery  110  must be capable of operating at low current drains for long periods of time, and then be capable of providing high-current pulses (for capacitor charging) when the patient requires a shock pulse. The battery  110  must also have a predictable discharge characteristic so that elective replacement time can be detected. Accordingly, the device  10  preferably employs lithium/silver vanadium oxide batteries, as is true for most (if not all) current devices. 
   As further shown in  FIG. 2 , the device  10  is shown as having an impedance measuring circuit  112  which is enabled by the microcontroller  60  via a control signal  114 . 
   In the case where the stimulation device  10  is intended to operate as an implantable cardioverter/defibrillator (ICD) device, it must detect the occurrence of an arrhythmia, and automatically apply an appropriate electrical shock therapy to the heart  12  aimed at terminating the detected arrhythmia. To this end, the microcontroller  60  further controls a shocking circuit  116  by way of a control signal  118 . The shocking circuit  116  generates shocking pulses of low (up to 0.5 Joules), moderate (0.5–10 Joules), or high energy (11 to 40 Joules), as controlled by the microcontroller  60 . Such shocking pulses are applied to the patient&#39;s heart  12  through at least two shocking electrodes and, as shown in this embodiment, selected from the left atrial coil electrode  28 , the RV coil electrode  36 , and/or the SVC coil electrode  38 . As noted above, the housing  40  may act as an active electrode in combination with the RV electrode  36 , or as part of a split electrical vector using the SVC coil electrode  38  or the left atrial coil electrode  28  (i.e., using the RV electrode as a common electrode). 
   Cardioversion shocks are generally considered to be of low to moderate energy level (so as to minimize pain felt by the patient), and/or synchronized with an R-wave and/or pertaining to the treatment of tachycardia. Defibrillation shocks are generally of moderate to high energy level (i.e., corresponding to thresholds in the range of 5–40 Joules), delivered asynchronously (since R-waves may be too disorganized), and pertaining exclusively to the treatment of fibrillation. Accordingly, the microcontroller  60  is capable of controlling the synchronous or asynchronous delivery of the shocking pulses. 
     FIG. 3  illustrates the housing  40  comprising a first  122  and a second  124  enclosure halves. The first  122  and second  124  enclosure halves provide mounting surfaces for electrical components of the device  10  as well as hermetically seal a portion of the device  10  against exposure to body fluids. The first  122  and second  124  enclosure halves are made of biocompatible, electrically conductive material, such as medical grade stainless steel or titanium. In certain embodiments, the first  122  and second  124  enclosure halves are hingedly connected to each other. 
   The device  10  also comprises a flexible electrical interconnect  130 . The flexible electrical interconnect  130  electrically interconnects the electrical components mounted in the first  122  and second  124  enclosure halves. The flexible electrical interconnect  130  is configured such that the flexible electrical interconnect  130  does not fold upon itself when the first  122  and second  124  enclosure halves are positioned adjacent each other and extends between the first  122  and second  124  enclosure halves when the first  122  and second  124  enclosure halves are distanced from each other. The flexible electrical interconnect  130  is configured such that the flexible electrical interconnect  130  is not subjected to undue mechanical strain when the first  122  and second  124  enclosure halves are adjacent each other or are distanced from each other. In one embodiment, the flexible electrical interconnect  130  describes a curved path loop substantially adjacent the periphery of an interior cavity  126  defined by the first  122  and second  124  enclosure halves when positioned adjacent each other. It is to be understood that a portion of the device  10 , including the first enclosure half  122 , is not shown in  FIG. 4  for clarity in viewing the remaining components. 
     FIGS. 4 and 5  illustrate one embodiment of the housing  40  comprising the first  122  and second  124  enclosure halves. The first  122  and second  124  enclosure halves are generally oblate and concave in contour and are configured to closely mate together so as to hermetically seal together and thereby define the sealed interior cavity  126  in a closed configuration  144  ( FIG. 4 ). The housing  40  provides a surface for mounting the electrical components of the stimulation device  10  previously described in an open configuration  146  ( FIG. 5 ). The hermetic seal of the first  122  and second  124  enclosure halves in the closed configuration  144  isolates the electrical components of the device  10  from body fluids that are typically found within the thoracic cavity of the implantee. 
   The device  10  also comprises a capacitor  136 . The capacitor  136  of this embodiment, is adhered to the second enclosure half  124  in a known manner. The capacitor  136  facilitates delivery of therapeutic shocks in the manner previously described. 
   The device  10  also comprises the flexible electrical interconnect  130 . The flexible electrical interconnect  130 , of this embodiment, is a generally planar assembly with a first end  132  and a second end  134 . The flexible electrical interconnect  130  comprises a flat ribbon cable comprising a plurality of electrical conductors  131  (obscured from view), each conductor  131  electrically isolated from the other conductors  131  by a bulk insulative material surrounding each conductor  131 . Each conductor  131  extends from the first end  132  to the second end  134  such that electrical signals are communicated between the first  132  and second  134  ends of the flexible electrical interconnect  130  in a known manner. 
   The flexible electrical interconnect  130  is configured such that, in an unstressed condition as would occur in the closed configuration  144 , the first end  132  is adjacent the second end  134  as illustrated in  FIG. 4 . In particular, the flexible electrical interconnect  130  describes a flat spiral, generally U-shaped structure approximately 0.010 inches thick by 0.50 inches wide by 1.5 inches long. It will be appreciated that the flexible electrical interconnect  130 , having a thickness of only 0.010 inches occupies minimal space inside the housing  40 . 
   A first leg  138  and a second leg  140  of the flexible electrical interconnect  130  are joined by a junction  142 . The first  138  and second  140  legs are generally elongate portions of the flexible electrical interconnect  130  and the first  138  and second  140  legs extend substantially parallel to each other when the flexible electrical interconnect  130  is in the closed configuration  144  as illustrated in  FIG. 4 . The junction  142  is also a portion of the flexible electrical interconnect  130  and physically and electrically joins the first  138  and second  140  legs while further facilitating resilient movement of the first  138  and second  140  legs while maintaining electrical communication therebetween. 
   The first end  132  is physically and electrically connected to the connector  120  and the second end  134  is physically and electrically connected to electrical components mounted in the second enclosure half  124  in a known manner, such as by soldering mechanical terminations and the like. Distancing the first  122  and second  124  enclosure halves, as illustrated in  FIG. 5 , places the device  10  in the open configuration  146 . The open configuration  146  facilitates servicing the device  10 , such as replacing the battery  110 , as well as installing the component parts of the device  10  during initial manufacture. 
   Positioning the housing  40  in the open configuration  146  distances the first  132  and second  134  ends of the flexible electrical interconnect  130  and also induces the first  138  and second  140  legs out of a parallel, planar orientation. In particular, positioning the housing  40  in the open configuration  146  partially twists the first  138  and second  140  legs and the junction  142 . However, as can be seen in  FIG. 5 , the configuration of the flexible electrical interconnect  130  is such that placement of the first  122  and second  124  enclosure halves, as illustrated in  FIG. 5 , in approximately a 180° orientation induces only approximately a 90° twist in each of the first  138  and second  140  legs. Displacing the first  122  and second  124  enclosure halves in a 180° orientation is the most that would typically be required for normal manufacture and servicing of the device  10 . The 90° twist in each of the first  138  and second  140  legs does not unduly stress the flexible electrical interconnect  130  and the flexible electrical interconnect  130 , of this configuration, can withstand repeated cycling between the closed  144  and open  146  configurations as herein described. 
   More specifically, as is illustrated in  FIG. 4 , each of the conductors  131  within the flexible electrical interconnect  130  extend in a first direction  161  in the first leg  138  of the flexible electrical interconnect when the enclosure  40  is in the closed configuration. Similarly, each of the conductors in the second leg  140  extend in a second direction  163  that is preferably parallel to the first direction  161 . However, each of the conductors  131  in the junction section  142  travel in a third direction  165  that is transverse to the first  161  and second  163  directions. The length of the portion of the conductors  131  extending in the transverse direction  165  in the junction section  142  of the flexible electrical interconnect  130  are preferably individually sized so that the first and second legs  138 ,  140  of electrical interconnect  130  are positioned immediately adjacent each other in the manner shown in  FIG. 4  when the enclosure  40  is in the closed configuration  144  to thereby reduce the amount of space within the enclosure  40  that is occupied by the electrical interconnect  130 . 
   It will be appreciated that the directions  161  and  163  need only be parallel in a single plane to permit the flexible electrical interconnect  130  to have reduced thickness when the enclosure  40  is in the closed configuration  144 . Each of the legs  138 ,  140  may be slightly mis-aligned in a direction perpendicular to the plane of the enclosure  40  as the connection point at the ends of the legs  138 ,  140  are offset from each other in the vertical direction. By positioning the legs  138 ,  140  so as to be side by side, with the transverse section  142  laterally spanning the two legs, the electrical interconnect  130  does not require the legs  138 ,  140  to be stacked on top of each other and thereby results in less volume between the two enclosure halves  122 ,  124  to be occupied by the electrical interconnect  130 . 
   As is also illustrated in  FIG. 4 , each of the conductors  131  in the electrical interconnect  130  achieves a 180 degree change of direction in two separate smaller angle turns. Specifically, the conductors  131  in the leg  138  are extending in a direction that, in at least one plane, is 180 degrees different than the direction of the conductors  131  in the leg  140 . By forming the electrical interconnect  130  to have the transverse junction section  142 , that extends in the transverse direction  165 , each of the conductors  131  achieves the 180 degree change of direction through a first interconnection  170  between the first leg  138  and the junction section  142  and a second interconnection  172  between the junction section  142  and the second leg  140 . In the embodiment illustrated in  FIG. 4 , the first and second interconnections  170 ,  172  result in a 90 degree turn of the conductors respectively. By dividing the change of direction between two separate interconnections  170 ,  172 , mechanical strain on the conductors  131  is reduced. Specifically, since the conductors  131  have two reduced bend points as opposed to a single higher angle bend point, the likelihood that the conductors  131  will break or separate at the bend point is reduced. 
   Moreover, as is illustrated in  FIG. 5 , when the enclosure halves  122 ,  124  are separated, the lateral separation between the legs  138 ,  140  that permits the separation is achieved by both rotating the legs  138 ,  140  about their interconnection with the junction section  142  and also by bending the legs  138 ,  140  in a direction that is perpendicular to the plane of the legs  138 ,  140  in the manner illustrated in  FIG. 5 . Hence, two separate degrees of motion provide the increase in the lateral separation between the legs  138 ,  140  which further reduces the tension on the conductors  131  contained within the interconnect  130 . 
   Thus, the flexible electrical interconnect  130  of this embodiment interconnects electrical components mounted in both the first  122  and second  124  enclosure halves. The flexible electrical interconnect  130  is a thin, planar assembly and thus occupies minimal space inside the housing  40 . The flexible electrical interconnect  130  is easily installed with common tools and procedures already known in the art. The flexible electrical interconnect  130  is also not under undue stress in either the closed  144  or open  146  configurations and thus avoids the high stress bending of flex cables in the prior art. 
   It should be appreciated that, although the embodiment described herein is with respect to a cardiac stimulation device  10 , the flexible electrical interconnect  120  can be readily adapted to other implanted medical devices by one of ordinary skill in the art. In alternative embodiments, the first  122  and second  124  enclosure halves are made of electrically non-conductive material. 
   Although the preferred embodiments of the present invention have shown, described and pointed out the fundamental novel features of the invention as applied to those embodiments, it will be understood that various omissions, substitutions and changes in the form of the detail of the device illustrated may be made by those skilled in the art without departing from the spirit of the present invention. Consequently, the scope of the invention should not be limited to the foregoing description but is to be defined by the appended claims.