Abstract:
The present invention relates to a pacer housing ( 60 ) comprising a connecter means adapted to receive a connect plug ( 110 ) on the proximal end of a lead ( 15 ) with an electrode located on the dismal end of said lead, said housing being made of metal, and connecter means comprising a tubular member having two ends and being located inside said housing, a first end ( 22, 122 ) of said tubular member being welded or bonded to an opening in a wall of said housing, the second end ( 23, 123 ) of said tubular member being closed. Said tubular member comprises a tube ( 21, 121 ) made of a metal being weldable or bondable to said metal housing, said tube being structurally intact along its entire length, all interior means ( 27, 127, 28, 128, 50, 150, 51, 151 ) in said tube for contacting the contact surfaces ( 111, 118 ) on said plug being located within the enclosure formed by said tube, said tube further containing at least one insulating ceramic plug ( 26, 126 ) being coaxial with said tube and holding said interior means for contacting said contact surfaces on said plug.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to pacer housings and more particularly to those parts of the housing intended for connection to the electrode leads. 
     2. Description of the Prior Art 
     Implantable pacers normally have a pacer housing (also called can) containing electronic circuitry and a unit for electric power as well as different electrodes which are connected to the interior parts in the pacer housing and which are to be implanted in or in the vicinity of the heart. The electrodes are connected to the pacer by means of leads. The internal parts of the pacers have to be well protected against the internal environment, especially the body fluids in the body for a long period of time, which places strict requirements on all entries into the interior of the can and especially on the connections of the leads to the housing. At the same time it should be possible to disconnect the pacer from the implanted leads for replacement or servicing of the pacer. The connective parts of the pacer and the leads have largely been standardized so as to encompass a relatively deep female socket comprising a number of contact surfaces whereas the leads are provided with a male part comprising one or several corresponding peripheral, generally circular contact surfaces. 
     At present the connective part of the pacer housing containing the female socket is made of a transparent material, normally epoxy resin, which is molded onto the housing and onto contacts extending outwardly from the housing. The male part of the leads is normally locked by means of set-screws, although other fastening means have been envisaged. The positioning and alignment of the different contact surfaces and of the fastening means or metallic threads for the set screws prior to the molding of the connective part is however very complicated and the delay in the manufacturing process incurred by the curing of the epoxy resin is considerable. 
     It would thus be desirable if the molding procedure could be dispensed with. 
     It has been discussed that these complexities could be avoided by designing the pacer with a socket located inside the metal housing. This kind of socket, sometimes termed “black holes”, is not used at present. 
     U.S. Pat. Nos 4,934,366 and 5,324,111, the teachings of both of which are incorporated herein by reference, describe two interior sockets or black holes for pacers. Both designs have a tubular member formed by a number of alternating sections made of metal and insulating ceramic, respectively. An end section of metal can be welded or bonded to an opening in the pacer housing by means of a flange. The use of different materials, however, sets high standards in regard of precision and durability of the component parts and as well as on the assembly procedure thereof. This is especially important since the interior sockets must meet very high standards regarding the integrity of the interior of the pacer housing during long times of implantation in a demanding environment. The manufacture of these known sockets thus is relatively complicated. The same is true for the device disclosed in U.S. Pat. No. 4,262,982, a ceramic socket combined with a metal flange for welding to a pacer housing and with a metallic interior contact pin. This device also has locking means in the form of an inwardly directed, circumferential rib located adjacent the opening of socket. This rib is intended to cooperate with barb-shaped sealing rings on the contact plug on the proximal end of the lead or catheter. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a pacer housing which allows the molding procedure to be avoided and the design of an interior socket to be simplified to a high degree while still meeting the required high standards 
     The above object is achieved in accordance with the principles of the present invention in a pacemaker housing having a connector arrangement which is adapted to receive a contact plug at the proximal end of a lead, the pacemaker housing having a housing enclosure made of metal and the connector arrangement forming a tubular member with two opposite ends disposed inside of the housing. A first end of the tubular member is open and is welded or bonded to an opening in the wall of the housing. The second end of the tubular member is closed. The tubular member is made of metal that is weldable or bondable to the metal housing. The tubular member is structurally intact along its entire length. A number of interior components, adapted for mechanical and electrical contact with contact surfaces of the contact plug of the lead, are held in an insulating ceramic plug which is located in the interior of the tubular member and is coaxial therewith. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a conventional pacer housing having a transparent molded connector part. 
     FIG. 2 shows a lead with a male connector plug, of the type used with the inventive pacer housing. 
     FIG. 3 shows an exploded view of various components of a connective part constructed in accordance with the principles of the present invention. 
     FIG. 4 is a side sectional view of an assembled connective part constructed in accordance with the principles of the present invention. 
     FIG. 5 is a side sectional view of a portion of a pacer housing constructed in accordance with the principles of the present invention with a connector plug of ane electrode lead inserted therein. 
     FIG. 6 is a side sectional view of a further embodiment of a connective part constructed in accordance with the principles of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a conventional pacer housing  1  having a molded, transparent connective part  2 . The connective part  2  includes a female socket  3 . The inner end of the socket  3  is provided with a longitudinal bore  7  having a relatively small diameter. The bore  7  is provided with a contact surface  4  adjacent to which threads for a set or lock screw  5  are located in a bore  6  oriented orthogonally relative to the female socket. The housing  2  is hermetically sealed in relation to the molded part  2  and the contact between the interior electronics and the contact surface  4  is achieved by means of a feed-through. The feed-through is a ceramic plug, typically made of alumina, into which one or more leads have been soldered. This lead is bonded (e.g. ultrasonically welded) to the electronics and to the contact surface  4 . The ceramic plug is soldered or brazed with gold into a sleeve made of titanium. This operation may be done at any time before the assembly of the pacer housing  2 . The sleeve is welded into an opening in the housing  2  in a sealing manner during the assembly of the pacer housing  2  that normally is formed by two halves. Before the connective part is molded onto the housing, these halves are welded together and sealed. 
     FIG. 2 illustrates a lead  15  having a proximal connecting plug  10  and a distal, transvenous, intracardial electrode  16  as well as an attachment element  17  for suturing the proximal end of the lead in the body of the patient. The connecting plug  10  is designed to be received in the socket  3  and the end thereof is provided with a longitudinally projecting contact pin  11  as well as a cylindrical body provided with sealing rings  12 ,  13 ,  14  intended to engage and seal against the corresponding inner cylindrical surface of the female socket  3 . The shape of the pin  11  corresponds to the shape of the bore  7 . When the plug  10  is inserted into the socket  3  the pin  11  engages the contact surface  4  and the set-screw in the bore  6  can be tightened against the pin  11  in order to securely lock the plug  10  in the socket  3 . The complexities involved in holding the bores, contact surfaces and threads in position and keeping them open and tree from the molding material during the molding process are evident. 
     For simplicity, the above prior art device has been illustrated as being unipolar. A bipolar embodiment naturally will be more complex to manufacture. The preferred embodiments of the invention described below will relate to bipolar embodiments. 
     FIGS. 3-5 show a preferred embodiment of the invention having a tubular member  20 . For clarity, all reference signs have not been repeated throughout all drawings. 
     The member has a tube  21  with two open ends  22 ,  23 . One end  22  is to be welded into an opening in the pacer housing. The tube  21  is made of the same metal as the pacer housing, in this case titanium. The opposite end  23  of the tube  21  is provided with a ceramic plug  26  fitting snugly in the tube  21  and soldered with for instance gold against the inside of the tube  21 . A metallic tubular sleeve  27  serving as a contact sleeve has been molded or bonded into the ceramic plug  26 . 
     The ceramic plug  26  is provided with an interior bore corresponding to the shape of the proximal part of the male connector in the same way as the molded prior art female connector described above and thus includes an interior sealing surface  53  for engagement with the sealing rings on the male connector. 
     The outer side of the outer end of the contact sleeve  27  is free from ceramic and extends out past the end of the tube  21 , thus forming a contact surface for connection to the interior of the housing. 
     The inner bore of the ceramic plug is closed by a metal plug  20   28  having an inner bore at the inner end sized to correspond to the contact pin of the male connector and forming the innermost part of the inner bore of the ceramic plug. The inner bore of the metal plug  28  also comprises an inner, circumferential groove  30 . The outer end of the metal  28  plug extends out from the ceramic, past the end of the contact sleeve  27 , thus forming a second contact surface. The metal plug  28  may be molded into the ceramic plug  26  or may be a separate part inserted and bonded into the inner bore of the ceramic plug. 
     The end part  31  of the inside of the contact sleeve  27  is not covered with the ceramic material. In this way an inner circumferential groove is obtained in the inner bore of the ceramic plug  26 . The bottom of the groove consists of the metal in the contact sleeve  27 . 
     Thus, when the ceramic plug  26  has been soldered or bonded into place, the second end  23  will be completely sealed by the plug  26  although allowing electrical connection to the interior of the tube via the contact ring  27  and the metal plug  22 . It should be noted that several concentric contact rings in a staggered configuration separated by insulating ceramic material could be used. The number of the connections thus would be limited only by the constraints given by the dimensions. 
     The manufacturing steps involved in the above can be carried out in advance as desired so as to achieve a prefabricated tube. 
     The end of the prefabricated tube can be welded to the pacer housing and the housing parts can be welded together after the connection of interior leads from the interior electronics to the contact ring and the plug, should this be desired. The remaining parts, i.e. the means achieving the contact between the contact rings and the contact surfaces on the male connector part on the lead and the means locking or fixating the male connector part in the socket, can easily be inserted afterwards. This means for instance that these parts would not interfere with the standard helium-based procedures for testing the housing with connector for leaks or that these parts would not be affected by the leak testing procedure. 
     FIG. 3 shows the main components of the tubular member, the tube  21  with the ceramic plug  26 , a locking arrangement  40  and two circular spring contacts  50 ,  51 . The spring contacts are similar to the spring contacts used in U.S. Pat. No. 4,934,366. 
     The locking arrangement  40  is designed in a similar way as the lead locking device disclosed in U.S. Pat. No. 4,262,982, herewith incorporated by reference. 
     The tube  21  preferably is of the same material as the pacer housing, which normally is made of titanium. The ceramic plug may for instance be made of alumina A1 O   3 , and the contact rings may for instance be made of stainless steel or of titanium. 
     FIG. 4 shows the tubular connective member in an assembled state and FIG. 5 shows the tubular connective member mounted in a pacer housing  60 . The male connector plug  110  is shown inserted into the connective member. 
     The lead locking arrangement  40  has a resilient ring  70  mounted in an interior, circumferential groove  71  in an inner sealing surface  54  in a hollow locking cylinder  41  fitting in the open end of the tube  21 . The resilient ring is mounted so as to be located directly behind the hindmost sealing ring  116  on the plug  110 . The resilient ring has an inner circumferential locking flange  72  biased inwardly into the central bore. When the plug  110  is inserted into the connective member, the sealing rings  112 ,  113 ,  114  and  116  thus will pass the flange and the hindmost sealing ring  116  will be held by the flange  72  against a movement outwardly from the connective member  40 . Other lead locking means that could be used in this embodiment are for instance disclosed in U.S. Pat. No. 4,934,366, the teachings of which are incorporated herein by reference. 
     FIG. 5 shows how the tube has been mounted in a pacer housing  60  and welded to an opening  61  in the housing via flanges located on the outside of the tube ends. FIG. 5 also shows a male connector plug  110  inserted in the tubular member. The plug has a contact pin  111 , a contact surface  118  and four sealing rings  112 ,  113 ,  114 ,  116 . The sealing rings  112 - 114 ,  116  are in engagement with the interior sealing surfaces  53 ,  54  and the spring contacts are in contact pin  111  respectively with the contact surface  118 . 
     The connector means can be achieved in a simple way compared with the prior art molded connector means. 
     As mentioned above, the ceramic part can be soldered into the tube in advance by similar methods as used when obtaining the feed-through in the prior art. The tube then is placed in the opening in one of the pacer housing halves and may supported by a support  62  located in the housing, should this prove desirable. The support in this case is a bracket being a part of the inner module in the pacer housing having an opening that is complementary to the outside of the tube. Conductors  55 ,  56  are bonded (typically by means of ultrasonic welding) to the connecting parts of the an electronic circuit board  57  and to the parts of the contact ring and the metal plug that are accessible at the end of the tube. The housing halves then are assembled and the two halves and the ends of the tube are welded together by means of a laser beam to form a sealed unit. This unit then is tested for leakage, for instance by means of standard helium-based procedures. It should be noted that no other kinds of work operations than those already used in the prior art are necessary. 
     The pacer then is finished by slipping the resilient spring contacts into the respective interior grooves in the ceramic plug and by inserting and bonding the lead locking means into place in the open end of the tube. 
     The new connective part thus is very simple to manufacture and to mount in the pacer housing. The welding and sealing of the housing only includes the additional step of welding the ends of the tube to the edges of the openings in the housing, which is performed in the same operation as the welding of the two housing halves. After the welding operation, no further operations are necessary, except for the simple insertion of spring contact rings and lead-locking mechanism. 
     Since the tube after the welding operation in principle forms an integral part of the pacer housing, a high degree of tightness and integrity is obtained. The tube will ensure a high strength and a high durability of the connective part, whilst the ceramic plug will ensure a high degree of tightness in view of the large contact area between ceramic plug and tube that can used for soldering, i.e. sealing. 
     One important feature of the invention is the ability to achieve a high capacitance between contact ring and tube. The ring and tube will be separated by the ceramic, which is chosen to be insulating and thus is a dielectricum. 
     The preferred embodiment naturally has a high capacitance since the contact ring has to extend a long way along the tube. This capacitance of course can be increased if a capacitor is connected in-between the outer tube and the contact ring. 
     In an alternative embodiment, illustrated in FIG. 6, a tube  121  has opposite ends  122 ,  123  and the mid-section of the tube  121  is provided with two relatively small lateral openings  124 ,  125 . The openings  124 ,  125  are sealed by means of a ceramic plug  126  fitting snugly in the tube and soldered with gold or otherwise bonded against the inside of the tube. Two contact rings  127 ,  128  have been molded into the ceramic plug. 
     The ceramic plug  126  is provided with an interior bore corresponding to the shape of the proximal part of the male connector in the same way as the molded prior art female connector described above. The ceramic plug thus includes an interior-sealing surface  153  for engagement with sealing rings on the male connector. 
     The central part of the inside of each of the contact rings is not covered with the ceramic material. In this way two inner circumferential grooves  130 ,  131  are obtained in the inner bore of the ceramic plug. The bottom of the grooves consists of the metal in the contact rings. Two openings  132 ,  133  are also provided in the outer surface of the ceramic plug  126  that may be made to coincide with the lateral openings  124 ,  125  in the tube wall. These openings allow access to the contact rings  127 ,  128  when the ceramic plug  126  has been mounted correctly in the tube  121 . Leads for contacting the interior of the housing can be bonded to the parts of the contact rings  127 ,  128  accessible through the openings  124 ,  125  and  132 ,  133 . 
     Typical dimensions for a tube intended to house a standard IS-1 male connector are for instance an inner diameter of 5 mm, a wall thickness of 0.3 mm (i.e. the same as the thickness of typical pacer housing walls) and a diameter of the holes  124 ,  125  of about 2 mm. A minimum area of about 4 mm 2  is necessary for the equipment presently used for bonding leads to metallic surfaces. The length of the tube is of course adapted to the specific housing into which it is to be placed, but might typically be about 25 mm. 
     Thus, when the ceramic plug  126  has been soldered or bonded into place, the openings  124 ,  125  will be completely sealed by the plug  126  although allowing electrical connection between the interior of the tube and the interior of the housing via the contact rings  127 , 128 . 
     The inner end  123  of the tube  121  is closed by means of a ceramic plug  170  soldered into the tube. The plug  170  may be made in one piece with the plug  126  or, as illustrated, in a separate piece. 
     The grooves  130 ,  131  contain spring contact rings  150 ,  151  of the same type as the ones described in the preferred embodiment described above. 
     The locking arrangement  140  is located in the same place and are identical to the locking arrangement described in the above preferred embodiment. The locking arrangement therefore is not described in more detail here. 
     It should be noted that the size of the openings  124 ,  125  being necessary to allow the bonding of the leads to the parts of the contact rings accessible through the openings  124 ,  125  and  131 ,  132  is small, in relation to the entire circumference and to the length of the tube. The openings thus do not affect the structural integrity of the tube. The contact rings  127 ,  128  moreover overlap the openings and are bonded thereto by means of the intermediate layer of ceramics, in this way strengthening the area in which the openings are located. 
     Typical dimensions for a tube intended to house a standard IS-1 male connector are for instance an inner diameter of 5 mm, a wall thickness of 0.3 mm (i.e. the same as the thickness of typical pacer housing walls) and a diameter of the holes  124 ,  125  of about 2 mm. A minimum area of about 4 mm 2  is necessary for the equipment presently used for bonding leads to metallic surfaces. The length of the tube is of course adapted to the specific housing into which it is to be placed, but might typically be about 25 mm. 
     These dimensions of course can be varied as long as the tube remains structurally intact, i.e. as long as the tube has a strength and rigidity that is sufficient to prevent loads, including thermal stresses, on the housing and/or the connector to be transferred as tensile forces to the ceramic parts. Of course, low tensile forces not exceeding the tensile strength of the ceramic could be accepted. Since there are standards regarding the loads a pacer housing and connector should be able to withstand and regarding the overall tightness of the housing, variations of the dimensions only would involve standard stress calculations and dimensioning well within the scope of the man in the art. It should be noted that this also could take the degree of soldering between ceramic plug and tube into account, since this would determine the extent to which tube and ceramic would function as a composite without going outside the ordinary skill of the man skilled in the art. 
     The number of lateral openings of course only is limited by the length of the tube and by the above considerations regarding the structural integrity. 
     It should also be noted that the main design features of the above two embodiments could be combined in different ways. One or several of the connections of the above first embodiment thus could be combined with one or several connections according to the above second embodiment. For instance, should it be desired to provide four contact means for a lead with four conductors, two of them could for instance be connected via an end plug designed in accordance with the first embodiment and the other two by means of lateral openings designed in accordance with the second embodiment. 
     It should also be noted that the ceramic material in the connector partly or entirely could be replaced by another insulating material, for instance a suitable plastics material. 
     Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.