Abstract:
The invention concerns an electromedical implant for intracardial coronary therapy comprising an implant housing in which functional component parts of the implant, namely a circuit, a battery and the like, are disposed. It is characterized in that the battery ( 10 ) has a flat side ( 10.2 ), an underside ( 10.3 ) and a peripherally extending narrow side ( 10.1 ) and the battery ( 10 ) is arranged with its underside ( 10.3 ) on an internal base surface ( 18.1 ) of the implant housing ( 18 ) and the circuit ( 22 ) is arranged in adjacent relationship with a flat side ( 10.2 ) of the battery ( 10 ).

Description:
The invention relates to an electromedical implant for intracardial coronary therapy, having the features recited in the classifying portion of claim  1 . 
   BACKGROUND OF THE ART 
   The electrotherapeutic treatment of cardiac arrhythmias by means of implantable cardiac pacemakers has become established as a powerful, versatile, comparatively low-risk and reliable form of treatment. Electromedical implants of that kind include numerous functional individual components which are necessary for long-lasting therapeutic treatment of the heart, which is suited to the physiological factors involved and which is as trouble-free as possible. Those components can be systematically divided into components which are disposed in a housing of the implant and components which are arranged outside the housing. The latter involve for example sensors for physiological parameters and the electrodes, by way of which a pacemaker pulse is transmitted to the atrium or ventricle myocardium. The implant housing in contrast accommodates functional components such as a battery, a circuit, telemetric means and the like. 
   The electromedical implant is to have a service life which is as long as possible and good compatibility. Under some circumstances those two aspects can be in conflict. Thus on the one hand the implant should be of the minimum possible structural size so that it is not perceived as troublesome by the patient after the implantation operation or indeed give rise to unwanted physiological reactions. On the other hand the battery for a long service life must be of the maximum possible capacity, which in a practical context means that the battery generally fills up markedly more than 80% of the internal space of the housing. There is therefore always the need for making the optimum possible use of the available space. 
   As intracardial therapy in the meantime has developed into a standard procedure which has proved its worth worldwide millions of times, it is appropriate for cost reasons to automate the process for production of the implants. The construction of current electromedical implants can in that respect be described in simplified terms as follows. All functional components such as the battery, the circuit, the telemetry unit or the like are disposed in mutually juxtaposed relationship in the implant housing. The implant housing itself is generally of a flat, elongate contour with rounded-off edges and is generally formed from two half-shell portions with a kind of snap-action mechanism comprising interengaging edges. Then, in the opened condition, the conventional arrangement with functional components mounted in mutually juxtaposed relationship on an inner base surface of the half-shell portions can be clearly seen. It will be noted that such an arrangement suffers from the disadvantage that, in assembly of the individual components, it is necessary to operate on a plurality of production axes. That makes automation more difficult and leads to increased costs. In addition the available space cannot be put to optimum use, for example because generally an expensive and complicated electrical contacting means for contacting the power-consuming components with the battery additionally has to be fitted. 
   U.S. Pat. No. 6,026,325 to Weinberg et al. discloses an electromedical implant having a circuit whose electronic components are arranged in stacked relationship. The individual electronic components of such a circuit are disposed perpendicularly to the heightwise extent of the implant housing on parallel substrate planes. The circuit and the further functional components such as a battery and capacitors are mounted in conventional manner in mutually juxtaposed relationship on the base surface of the implant housing. 
   U.S. Pat. No. 6,251,124 to Youker et al. describes a cardiac pacemaker in which a plurality of capacitors is arranged in a plurality of substrate planes in the housing. All further functional components—disposed beside the capacitors—are arranged on the inner base surface of the housing. 
   Furthermore, WO 99/06107 discloses a cardiac pacemaker whose circuit includes a memory unit comprising memory chips stacked in mutually superposed relationship. That is intended to minimize the structural space required for an electrical connection between the individual memory chips. As in the above-mentioned specifications, the stacked arrangement is limited to selected partial structures of the functional components of the implant. 
   SUMMARY OF THE INVENTION 
   An aspect of the present invention is to make better use of the structural space available in the housing and to optimize the construction of the implant from the point of view of a production process which can be automated and is as simple as possible. 
   The invention emanates from an electromedical implant for intracardial coronary therapy comprising an implant housing and functional components of the implant disposed in said housing wherein the functional components comprise a circuit and a battery and wherein the battery has a flat side, an underside and a peripherally extending narrow side and the battery is arranged with its underside on an inner base surface of the implant housing and the circuit is disposed adjacent to a flat side of the battery. 
   In a first advantageous configuration of the invention the circuit includes a component carrier with fitment set, on the top side of which the individual electronic components of the circuit are mounted. An underside of the component carrier and thus the circuit is arranged adjacent to the flat side of the battery. Advantageously, the circuit is fixedly mounted to the flat side of the battery, for example by means of known adhesive processes. In the depicted arrangement accordingly the flat circuits which are embodied on conventional component carriers are fixed directly on the battery, in which respect a mounting direction of battery and circuit is retained. It will be self-evident that an electrical connection to the voltage source between the battery and the circuit only needs to be of small dimensions and, in contrast to conventional electrical connections, does not have to be made by way of a joining procedure but can also be implemented in a direct plug-in configuration. Accordingly a short discrete join is possible, without discrete elements. 
   During discharge of the battery a slight increase in the volume of the battery occurs, as a consequence of the underlying electrochemical reaction. That discharge-induced swelling of the battery must be compensated when there is a fixed connection between the battery and the circuit as otherwise there is a threat of mechanical damage to the circuit. In a further advantageous embodiment of the invention for that purpose disposed between the flat side of the battery and the underside of the circuit are structures with which it is possible to compensate for the discharge-induced swelling of the battery. Those structures include free spaces between the battery and the circuit or joining elements which permit a relative movement of the circuit with respect to the battery. 
   In a further advantageous configuration of the invention the underside of the component carrier and thus the circuit is arranged adjacent to an inward side of the implant housing. The electronic components of the circuit then face in the direction of the battery. If the inward side of the half-shell portion is suitably structured the half-shell portion can function at the same time as the component carrier for the electronic components. At any event, it is possible to forego the structures for compensation of the discharge-induced swelling of the battery. In production of the implant, in a common production step, the circuit is introduced into the implant and the housing closed. 
   It is further advantageous if there is provided a mounting element which accommodates the circuit. The relative orientation of the fitment set or components of the circuit with respect to the battery can then be adapted to the respective requirements involved. Accordingly, the electronic components can face either in the direction of the battery or in the direction of the housing. The mounting element can be introduced into the implant without a mechanical join to the battery or only at the periphery thereof so that the mechanical stresses which occur as a consequence of the discharge-induced variation in volume cannot be diverted to the circuit. 
   In addition, it has proven to be advantageous if the battery does not fill all the internal base surface of the implant housing. The remaining free spaces are used in such a way that, after mounting of the constituent parts, electronic components of a great structural height project into those free spaces. The aim here is to ensure the best possible utilization of space with a small overall structural height without having to make cuts in terms of functionality. 
   The battery which is suitable for such single-axis construction of the electromedical implant is to be as flat as possible in terms of its contour, as the circuit and optionally further functional component parts are to be arranged adjacent to its flat side. In this connection, the use of electrochemical energy storage systems based on lithium and manganese dioxide has proven to be particularly advantageous. The equipment components of the circuit are preferably also of the minimum possible structural height. 
   A further preferred configuration of the invention provides that the adjacent flat sides of the battery and the circuit have a mutually matched heightwise profile. The aim here is to minimize the overall height of the two component parts which are stacked one upon the other. Thus, in regions in which electronic components of the circuit of a relatively great structural height are disposed, the battery is of a smaller structural height than in the other regions. If further or all functional component parts disposed in the implant housing are stacked one upon the other, then the above-described matching in respect of the heightwise profile can also be applied to those component parts. 
   A further preferred embodiment of the invention is one in which the implant housing comprises two half-shell portions and one thereof is at the same time a constituent part of the battery housing. In that way it is possible to eliminate a housing half-shell portion. 
   In a further development of the last-mentioned concept of the invention, both half-shell portions at the same time also form the battery housing. In this case the circuit and all further functional component parts of the implant must hermetically sealed with respect to the electrolyte of the battery. It is possible in that way to eliminate two half-shell portions and the utilization of structural space in the arrangement can be further optimized. 
   Further preferred embodiments of the invention are set forth by the other features recited in the appendant claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail hereinafter in embodiments with reference to drawings in which: 
       FIGS. 1   a  through  1   d  are diagrammatic plan and side views of batteries for an electromedical implant, 
       FIGS. 2   a  and  2   b  are two diagrammatic plan views onto a half-shell portion of an implant housing with a battery arranged on the internal base surface, 
       FIG. 3  is a sectional view of a circuit arrangement in the implant in accordance with a first variant, 
       FIG. 4  is a sectional view of a circuit arrangement in the implant in accordance with a second variant, 
       FIGS. 5   a  and  5   b  show two sectional views of alternative arrangements of the circuit with a mounting element, 
       FIG. 6  shows a sectional view of a further alternative circuit arrangement in the implant with a free space in the region of the implant housing, 
       FIGS. 7   a  and  7   b  show two sectional views of alternative arrangements with a heightwise profile which is matched as between the battery and the circuit, 
       FIGS. 8   a  through  8   f  show perspective detail views of six alternative lead-through ducts for producing an electrical connection, 
       FIGS. 9   a  and  9   b  show a partly sectional view and a detail view on an enlarged scale through the battery, circuit and a structure for compensating for discharge-induced variations in volume, 
       FIGS. 10   a  and  10   b  show perspective side views of two joining elements for compensating for discharge-induced variations in volume in the open and closed form, 
       FIG. 11  is a sectional view of an arrangement in which the battery housing replaces a half-shell portion of the implant housing, 
       FIG. 12  shows a sectional view of an implant housing in which the battery housing replaces both half-shell portions of the implant housing, and 
       FIG. 13  shows an illustration of the single-axis production process of an electromedical implant. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The mode of operation and the area of use of electromedical implants are generally known. By virtue of an appropriate selection of functional components, all stimulation and diagnostic functions which are necessary for each individual case can be integrated into such an electromedical implant. It will be noted that in the present case only the arrangement according to the invention of the functional components in the implant housing is of significance. Therefore only the structural features, which are necessary to the invention, of the individual functional components and their relative position with respect to each other are described in the examples hereinafter. 
     FIGS. 1   a  through  1   d  are greatly simplified side and plan views showing the contours of two alternative embodiments of a battery  10 . In this example the battery  10  is of an oval basic shape. While having the same base surface, that is to say the same lengthwise and widthwise dimensions, the two batteries  10  differ only in respect of their heightwise profile. The battery  10  illustrated in  FIGS. 1   a  and  1   b  has a narrow side  10 . 1  which extends therearound at a constant height as well as a flat side  10 . 2  and an underside  10 . 3  with a flat contour, thus affording a homogenous heightwise profile. In contrast the battery  10  shown in  FIGS. 1   c  and  1   d  involves a heightwise profile in which a first portion  12  of the narrow side  10 . 1  and the flat side  10 . 2  is of a smaller height than a second portion  14 . The conditions under which the use of one or other alternative embodiment of the battery  10  is appropriate will be discussed in greater detail hereinafter. 
   The battery itself is in particular an electrochemical cell based on lithium/manganese oxide elements. Batteries  10  of that kind are distinguished by their particularly high energy density and also their flexible design so that they are suitable as a flat unit or sandwich unit.  FIGS. 2   a  and  2   b  show the relative position of two batteries  10  involving different base shapes in a half-shell portion  16  of an implant housing  18 . As will be clearly apparent the battery  10  in each case does not take up an entire internal base surface  18 . 1  of the half-shell portion  16 . Rather, free spaces  20  of differing sizes remain, and the use thereof will also be discussed in greater detail hereinafter. 
   A highly diagrammatic sectional view in  FIG. 3  shows an electromedical implant including two functional component parts, namely the battery  10  and a circuit  22 . The circuit  22  includes all electronic components  24  which are necessary for the functional logic of the implant and which are arranged in the form of an equipment set on a component carrier  26  with a circuit board. The electronic components  24  are preferably SMT-units which are produced in per se known manner from the point of view of a structural height which is as small as possible. An electrical connection between the battery  10  and the circuit  22  can be produced by the lead-through duct  28  indicated here. The circuit  22  is now fitted with its underside  22 . 1  onto the flat side  10 . 2  of the battery  10 , in such a way that electrical contact is produced and the circuit  22  is arranged in adjacent relationship to the flat side  10 . 2  of the battery  10 —possibly being fixed by adhesive means. Then the implant housing  18  is closed by a second half-shell portion  30  being put onto the first half-shell portion  16 . The two half-shell portions  16 ,  30  are for that purpose preferably in the form of snap-action shell portions with mutually interengaging edges. 
   In an arrangement which is an alternative to  FIG. 3  the circuit  22  is arranged with its underside  22 . 1  in adjacent relationship to an inward side  30 . 1  of the second half-shell portion  30  ( FIG. 4 ). The equipment set of the circuit  22  then faces in the direction of the battery  10 . An electrical connection is in turn made by way of the lead-through duct  28  when the two half-shell portions  16 ,  30  of the implant housing  18  are brought together. The inward side  30 . 1  of the second half-shell portion  30  can possibly be suitably structured to carry the electronic components  24  of the circuit  22 . Thus for example a component carrier can be introduced directly into the inward side  30 . 1  of the half-shell portion  30 . 
   The following is to be noted in regard to the dimensioning of the individual constituent parts of the variants in  FIGS. 3 and 4 : an overall thickness of the battery  10  in all of the regions in opposite relationship to the circuit  22  is preferably &lt;3.9 mm, a component height of all electronic components  24  is preferably &lt;2 mm and the thickness of the component carrier  26  is &lt;0.25 mm. Finally the battery  10  and the circuit  22  preferably extend over &gt;85%, in particular over &gt;90%, particularly preferably over &gt;95%, of the overall housing volume. The circuit  22  preferably extends over &gt;80% in particular over &gt;90% and particularly preferably over &gt;95% of the flat side of the battery  10 . 
     FIGS. 5   a  and  5   b  show the circuit  22  and the battery  10  in a stacked arrangement which is in principle the same, as in  FIGS. 3 and 4 . However, the circuit  22  does not bear directly against the battery  10  or the half-shell portion  30  but is accommodated by a mounting element  32 . The mounting element  32  has structures which are suitable for that purpose and in which the component carrier  26  can be clamped. The specific design configuration of the structures must be adapted to the respective structural aspects involved. Measures of that nature are adequately known to the man skilled in the art so that they will not be discussed in greater detail here. After accommodating the circuit  22  the mounting element  32  is arranged in adjacent relationship with the battery  10 , in which case the component mounting side thereof faces selectively in the direction of the half-shell portion  30  ( FIG. 5   a ) or in the direction of the battery  10  ( FIG. 5   b ). Such a mounting element  32  affords the advantage that stresses which can occur in the region of the battery  10  as a consequence of variations in volume are not transmitted directly to the circuit  22  and there result in mechanical damage. In addition, this arrangement affords options in terms of joining technologies which are suited to single-axis mounting operations. 
   If the battery  10  does not occupy the entire base surface of the half-shell portion  16  of the implant housing  18  and thus free spaces  20  remain, it is possible to embody the alternative arrangement of the component parts of the implant, as is diagrammatically shown in  FIG. 6 . In accordance with that arrangement electronic components  24  of particularly great structural height are placed on the circuit  22  in such a way that they project into the free spaces  20 , after the two component parts have been assembled. 
   With a differing structural height in respect of the electronic components  24  of the circuit  22 , two further alternative possible design options present themselves for such a single-axis arrangement of the component parts ( FIGS. 7   a  and  7   b ). Both alternatives are based on a battery  10  with heightwise profile as has already been described with reference to  FIG. 1   b . As shown in  FIG. 7   a  the contour of the circuit  22  including the component carrier  26  is adapted to the heightwise profile of the battery  10 . The electronic components  24  of the greatest structural height are obviously disposed in the region  12  of the battery  10  which involves the smallest heightwise extent ( FIG. 7   a ). Alternatively, as shown in  FIG. 7   b , a circuit  22  with a flat component carrier  26  is arranged in adjacent relationship with the half-shell portion  30 , more specifically in such a way that the highest electronic components  24 , after the mounting procedure, are arranged above the region  12  of the battery  10  which is of the smallest structural height. 
     FIGS. 8   a  through  8   f  show a total of six alternative embodiments of a lead-through duct  28  which can be used to produce the electrical connection between the battery  10  and the circuit  22 . The ducts  28  can be soldered on during an SMT-mounting process as constituent parts of the circuit  22 . It is necessary in each individual case to decide at what locations ultimately a soldering operation is to be effected or what orientation individual elements of the duct  28  have relative to the position of the component parts to be connected therewith. It will be noted that in principle the single-axis construction of the functional component parts permits a marked simplification in the electrical circuitry as only small distances have be bridged. That affords savings of material and gains in terms of structural space. The ducts  28  which are set forth by way of example are electrically connected to the circuit  22  by way of nail heads ( FIG. 8   a ), adaptors ( FIGS. 8   b  and  8   c ), bent pins ( FIGS. 8   d ), flattened pins ( 8   e ) or conventional solder joins ( 8   f ). In accordance with the variants in  FIGS. 8   b  and  8   c , it is possible to forego bonding joining processes for producing the electrical connection. It will be appreciated that for that purpose it is possible to provide electrical plug elements of varying configurations, which engage into each other when the implant is assembled. Here too the description will not go into these aspects in greater depth as such plug elements are sufficiently known to the man skilled in the art and have to be adapted to the respective functional and structural requirements involved, from one case to another. 
   When the circuit  22  is fixedly connected to the battery  10 , measures must be taken to prevent damage to the circuit  22  as a consequence of a gradual variation in volume of the battery  10 . Such a variation in volume results from the electrochemical reactions which take place during the discharge process in the battery  10 . To compensate for the discharge-induced swelling of the battery  10 , special structures  34  are arranged between the flat side  10 . 2  of the battery  10  and the underside  22 . 1  of the circuit  22 .  FIGS. 9   a  and  9   b —in part as a detail view on an enlarged scale—show a view in section through the battery  10  and the circuit  22  in the region of the structures  34 . They are in the form of free spaces between the battery  10  and the circuit  22 , into which parts of the battery  10  can penetrate in the discharge process and the increase in volume which is related thereto. Those structures  34  can be an integral constituent part of the component carrier  26 , for example etched copper structures, and they can be inexpensively produced using standard procedures in production of the component carrier. 
   As an alternative thereto, it is also possible to provide between the battery  10  and the circuit  22  joining elements  36  as are shown in  FIGS. 10   a  and  10   b  prior to and after mounting of the component parts. The joining elements  36  involve a male and a female contour which, when the component parts are stacked in mutually superposed relationship, engage one into each other and hold the component parts at a defined spacing. It will be appreciated that it is possible here to have recourse to a large number of alternative embodiments of the joining elements  36 , as are sufficiently known from the state of the art. The only essential criterion in regard to the joining elements  36  is that they permit a relative movement of the two component parts with respect to each other. For automation reasons the illustration snap-action connection particularly presents itself in that respect. 
     FIG. 11  diagrammatically shows a further alternative arrangement with a single-axis component construction. In its broad outlines it corresponds to the arrangement of the circuit  22  and the battery  10 , which has already been described with reference to  FIG. 3 . It will be noted that in this case a battery housing  38  is used at the same time to form the lower half-shell portion of the implant housing  18 . For that reason, at least in that region, the battery housing  38  is made from a biocompatible material, in particular titanium. In that way it is possible to forego one of the two half-shell portions of the implant housing  18  and the resulting structural space can be used for the functional component parts. In addition, a production step is eliminated from the production process, namely the step of placing the battery  10  in one of the half-shell portions of the implant housing  18 . When turning over a seam between the battery housing  38  and the half-shell portion  30 , if necessary (for example because of a thermal loading in the joining procedure), it is possible to implement subsequent filling of the battery  10  with electrolyte or activation in some other manner by way of an additional filling opening, whereby it is possible to determine the moment in time of the commencement of energy-consuming operation of the implant. 
   In an extension of the last embodiment  FIG. 12  is a diagrammatic sectional view of an electromedical implant in which the implant housing  18  is completely replaced by the battery housing  38 . All functional component part—in this case the illustrated circuit  22  with its electronic components  24 —are disposed within the battery  10  and to protect them have to be hermetically sealed in relation to the electrolyte of the battery  10 . Sealing of the circuit  22  can be effected for example by a dipping process with inert resins/dipping lacquers. The dried resins/dipping lacquers form a protective layer through which the electrolyte cannot pass or which it cannot attack. It is possible in that way to eliminate two housing half-shell portions. 
     FIG. 13  is intended to illustrate once again by way of example the single-axis mounting of the functional component parts during manufacture of an implant (as indicated by an arrow). Firstly the battery  10 , then the circuit  22  and finally the half-shell portion  30  are respectively fitted into or onto the half-shell portion  16 , in each case from the same approach direction. That substantially simplifies automation and enhances the degree of precision in terms of placement of the individual components. The arrangement and the mounting sequence may vary. 
   The implants produced in the above-described manner are intended to correspond in their dimensions to the dimensions of known implants. They are therefore of an overall height of between 5 and 7 mm. Of that, the metal case of the implant housing  18  including applied films for insulation and the free space for fixing of the component parts occupies between about 0.6 and 0.9 mm. In embodiments in which the battery  10  has a heightwise profile ( FIGS. 7   a  and  7   b ) the thickness of the battery generally varies between 1.5 and 4.5 mm, with the remaining structural space being used for the circuit  22 . 
   
     
       
             
           
             
             
           
         
             
                 
             
             
               List of references 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               10 
               battery 
             
             
                 10.1 
               narrow side of the battery 10 
             
             
                 10.2 
               flat side of the battery 10 
             
             
                 10.3 
               underside of the battery 10 
             
             
               12 
               portion of low structural height 
             
             
               14 
               portion of larger structural height 
             
             
               16 
               lower half-shell portion 
             
             
               18 
               implant housing 
             
             
                 18.1 
               internal base surface 
             
             
               20 
               free space 
             
             
               22 
               circuit 
             
             
                 22.1 
               underside of the circuit 22 
             
             
               24 
               electronic components 
             
             
               26 
               component carrier 
             
             
               28 
               lead-through duct 
             
             
               30 
               upper half-shell portion 
             
             
                 30.1 
               inward side of the upper half-shell portion 30 
             
             
               32 
               mounting element 
             
             
               34 
               structures for compensation of discharge-induced swelling 
             
             
               36 
               joining element 
             
             
               38 
               battery housing