Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a one-piece header assembly for connecting implantable medical devices to a body organ intended to be assisted by the medical device. The header assembly includes terminal blocks which connect directly to feedthrough wires extending from inside the medical device to a conductor leading to the body organ or tissue being assisted.  
         [0003]     2. Prior Art  
         [0004]     Header assemblies for implantable medical devices generally comprise feedthrough conductors in the form of pins or wires connected to the internal components of the medical device. The feedthrough wires extend through a wall of the medical device housing, such as a lid, and are electrically insulated therefrom by a ceramic-to-metal seal, and the like. Electrical continuity is established by connecting intermediate conductor wires between the feedthrough wires and connector blocks in the header assembly. Examples of this type of header assembly are shown in U.S. Pat. No. 4,254,775 to Langer, U.S. Pat. No. 4,262,673 to Kinney et al., U.S. Pat. No. 4,764,132 to Stutz, Jr., U.S. Pat. No. 5,282,841 to Szyszkowski and U.S. Pat. No. 5,336,246 to Dantanarayana.  
         [0005]     The intermediate conductor wires represent an electrical connection that could fail through improper connection, corrosion, breakage, and the like. The header assemblies of the present invention eliminate the intermediate conductors. Instead, the feedthrough wires from the medical device connect directly to terminal blocks in the header assembly. This is a more reliable construction than those of the conventional designs.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention is, therefore, directed to a header assembly for a medical device. The header assembly serves as a structure supporting the electrical connection between feedthrough wires extending from inside the medical device to a conductor connected to the body organ or tissue being assisted. Several different embodiments of header assemblies are described including those which are molded directly onto the lid of the medical device and pre-molded ones which are later secure to the medical device. In either case, the present header assemblies include terminal blocks which connect directly to the feedthrough wires coming from the medical device. This eliminates the need for an intermediate conductor wire connecting between the feedthrough wires and the terminal blocks as in the prior art devices.  
         [0007]     These features of the present invention will be apparent upon consideration of the following detailed description thereof presented in connection with the following drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is an exploded view of a header assembly  10  for an implantable medical device  18 .  
         [0009]      FIG. 2  is a perspective view of the header assembly  10  and medical device  18  shown in  FIG. 1 .  
         [0010]      FIG. 3  is a sectional view taken along line  3 - 3  of  FIG. 2 .  
         [0011]      FIG. 4  is a plan view, partly in phantom, of the header assembly  10 .  
         [0012]      FIG. 5  is a side elevational view of the header assembly  10 .  
         [0013]      FIG. 6  is a sectional view taken along line  6 - 6  of  FIG. 5 .  
         [0014]      FIG. 7  is a sectional view taken along line  7 - 7  of  FIG. 5 .  
         [0015]      FIG. 8  is an elevational view, partly in section and partly in phantom, of a header assembly  150  according to the present invention for the medical device  18 .  
         [0016]      FIG. 9  is a perspective view of the header assembly  150  connected to feedthrough wires  172 ,  174  from the medical device.  
         [0017]      FIG. 10  shows the header assembly being secured to the casing by a mechanical fasteners.  
         [0018]      FIG. 111  is a cross-sectional view of a book mold  250  in an opened position for manufacturing a header assembly according to the present invention.  
         [0019]      FIG. 12  is a cross-sectional view of the book mold  250  of  FIG. 11  in a closed position.  
         [0020]      FIG. 13  is a broken away view, partly in phantom, of another embodiment of a terminal  300  according to the present invention.  
         [0021]      FIG. 14  is a cross-sectional view along line  14 - 14  of  FIG. 13 .  
         [0022]      FIG. 15  is sectional view of another embodiment of a terminal  320  prior to a lead  328  being inserted therein.  
         [0023]      FIG. 16  is a sectional view of the terminal of  FIG. 15  with the lead  328  received therein.  
         [0024]      FIG. 17  is a sectional view of another embodiment of a terminal  340  prior to a lead  350  being inserted therein.  
         [0025]      FIG. 18  is a cross-sectional view along line  18 - 18  of  FIG. 17 .  
         [0026]      FIG. 19  is a sectional view of the terminal of  FIGS. 17 and 18  with the lead  350  received therein. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     Referring now to the drawings, FIGS.  1  to  7  illustrate a header assembly  10  according to the present invention comprising at least one pair of terminal blocks  12  and  14  partially surrounded by a molded polymeric header  16  connected to an implantable medical device  18 . The terminal blocks  12 ,  14  provide for connecting a co-axial conductor  20  from the medical device to a body tissue. The implantable medical device  18  is exemplary of any one of a number of known assist devices such as cardiac defibrillators, cardiac pacemakers, drug pumps, neurostimulators, hearing assist devices, and the like.  
         [0028]     The implantable medical device  18  is contained in a housing  22  of a material such as of stainless steel, and is shown in an exemplary form comprising first and second main clam shell portions  24  and  26 . The clam shells  24  and  26  are mated together and hermetically sealed about their periphery to provide an enclosure for the medical device including its control circuitry  28  and a power supply  30  such as a battery ( FIG. 3 ). The battery  30  is connected to the control circuitry  28  by electrical leads  32  and  34 . There may also be a capacitor for a medical device such as a defibrillator.  
         [0029]     In particular, the first clam shell  24  comprises spaced apart side walls  36  and  38  extending to and meeting with end wall  40 . The side walls  36 ,  38  and the end wall  40  meet each other at rounded corners and extend to a front wall  42 . Opposite the front wall  42  is a peripheral edge  44  of side walls  36 ,  38  and end wall  40  while opposite the end wall  40  is an opening  46 .  
         [0030]     The second clam shell  26  comprises spaced apart side walls  48  and  50  ( FIG. 3 ) extending to and meeting with end wall  52 . The side walls  48  and  50  and end wall  52  meet at rounded corners and extend to front wall  54 . Opposite the front wall is a peripheral edge  56  of the side walls  48  and  50  and end wall  52  while opposite the end wall  52  is an opening  58 . The first clam shell  24  is sized to fit inside the periphery of the second clam shell  26  in a closely spaced, lap joint relationship. This assembly forms a container having an opening  60  leading therein where the coinciding openings  46  and  58  of the respective clam shells  24  and  26  reside. The container opening  60  has a generally rectangular shape.  
         [0031]     The benefit of having a lap joint construction for the mating clam shells  24  and  26  is that when they are hermetically sealed together, such as by laser welding, the laser beam is prevented from compromising the control circuitry  28  and power supply  30  of the medical device. With a coplanar or butted seam construction (not shown), it is possible for the laser beam to penetrate past the junction of the peripheral edges  44 ,  56  of the clam shells  24 ,  26  to compromise the internal device components or power supply housed therein. If a butt welded construction is used, a backing ring (not shown) is desired. An example of a backing ring for a butt weld construction is shown in FIG. 14 of U.S. Pat. No. 6,334,879 to Muffoletto et al., which is assigned to the assignee of the present invention and incorporated herein by reference.  
         [0032]     A lid  62  is hermetically sealed to the opening  60  of the mated clam shells  24 ,  26 . The lid  62  consists of spaced apart upper and lower surfaces  64  and  66  extending to and meeting with a surrounding edge  68  ( FIG. 3 ). The surrounding edge  68  includes an inverted step or rim  70  to assist in the sealing connection between the lid  62  and the mated clam shells  24 ,  26 . Preferably, the lid  62  is sealed in place, such as by laser welding (not shown), to create the hermetic housing  22  for the implantable medical device  18 .  
         [0033]     While the medical device is shown being contained inside a housing of mating clam shells  24 ,  26 , the present invention is not intended to be so limited. Other types of housings such as prismatic, deep drawn, cylindrical are also contemplated.  
         [0034]     As shown in  FIGS. 1 and 3 , the upper surface  64  of the lid  62  includes a plurality of protruding anchors  72  which assist in joining the header  10  to the lid. Internal protrusions  74  depend from the lower lid surface  66  and assist in positioning the lid on the mated clam shells.  
         [0035]     The lid  62  further comprises at least two openings  76  and  78  through which respective feedthrough wires  80  and  82  pass. The feedthrough wires extend from a distal end positioned inside the housing  22  connected to the control circuitry  28  for the medical device  18  to respective proximal ends disposed generally parallel to and spaced above the upper surface  64  of the lid  62 . The feedthrough wires  80 ,  82  are electrically insulated from the lid  62  by respective ceramic-to-metal seals or glass-to-metal seals  84  and  86 .  
         [0036]     The proximal end of feedthrough wire  80  is connected to the first terminal block  12  supported thereon while the other feedthrough wire  82  is connected to a second terminal block  14  depending therefore. The terminal blocks  12 ,  14  are ring-shaped members of different diameters, sized to be in electrical contact with matching portions of the lead  88  for a co-axial conductor  90 , as will be described in detail hereinafter.  
         [0037]     As shown in  FIG. 3 , the terminal blocks  12  and  14  are aligned in a co-axial relationship and encased in the molded header  16  having a bore  92  providing communication to both of them. The molded header  16  comprises spaced apart front and back walls  94  and  96  extending to a curved upper wall  98  and a generally planar bottom wall  100 . The bottom wall  100  is supported on the upper lid surface  64  and retained in place by encasing the lid anchors  72 . The bore  92  is sized to receive the co-axial conductor lead  88 . Those skilled in the art will readily understand that the exact shape of the molded header is exemplary. In fact, the molded header can have a myriad of different shapes only limited by the design specifications of the associated medical device and its intended use.  
         [0038]     In that respect, the header assembly bore  92  has a first portion  102  of a first diameter sized to receive a distal portion  104  of the conductor lead  88 , a second, intermediate portion  106  of a second, greater diameter sized to receive a proximal portion  108  of the lead  88  and a third portion  110  of a still greater diameter than the intermediate portion. The terminal blocks  12 ,  14  have lead openings of diameters somewhat larger than the first and second bore portions  102 ,  106  so that the conductor lead  88  is received therein in a tight fitting, electrically stable connection.  
         [0039]     The front wall  94  of the molded header  16  is provided with a pair of passageways  112  and  114  aligned perpendicularly with the longitudinal axis of the bore  92 . Passageway  112  extends to a threaded aperture  116  in the side wall of terminal block  12  to provide for communication with the first bore portion  102 . The passageway and aperture threadingly receive a set screw  118  that contacts the distal portion  104  of the conductor lead  88  to prevent loss of electrical contact between the lead and the terminal block  12 . Similarly, passageway  114  extends to a threaded aperture  120  in the side wall of terminal block  14  to provide for communication with the second bore portion  106 . A set screw  122  is received therein to contact the proximal portion  108  of the conductor lead  88 , thereby maintaining electrical continuity between the lead and the terminal block  14 .  
         [0040]     An annular channel surrounds the third bore portion  110  for capturing an O-ring  124  therein. This helps to prevent body fluids and the like from contacting the conductor portions  104  and  108  received in the respective terminal blocks  12  and  14 . A raised seal  126  further helps prevent body fluids from contacting the co-axial conductor lead  88 . Finally, the header assembly  10  is provided with a suture bore  128  adjacent to the conductor lead bore  92 . The suture bore  128  aids a physician in securing the medical device inside a body.  
         [0041]     As known in the art, the end (not shown) of the co-axial conductor  90  opposite that of the lead  88  is positioned in a body tissue, such as a heart muscle, for transmitting physiological information to the medical device and for administering a medical theory as needed. An example of this is in a cardiac defibrillator where the medical device may monitor the heart rate for extended periods of time. Then, when a potentially fatal irregular, rapid heartbeat known as tachyarrhythmia is detected, the defibrillator delivers an electrical shock to the heart through the lead  88  and conductor  90 .  
         [0042]      FIGS. 8 and 9  show a further embodiment of a header assembly  150  according to the present invention. The header assembly  150  comprises a polymeric material supporting a first pair of terminal blocks  152  and  154  and a second pair of terminal blocks  156  and  158 . The terminal block pairs have lead openings aligned co-axially along respective conductor bores sized to receive the conductor leads  160  and  162  of co-axial conductors  164  and  166 . The lid  168  is provided with a ceramic-to-metal seal  170  that electrically insulates feedthrough wires  172 ,  174 ,  176  and  178  from the lid  168 . The feedthrough wires are in electrical contact with respective terminal blocks  152 ,  154   156  and  158 .  
         [0043]     In this respect, the header assembly  150  is similar to the header assembly  10  of FIGS.  1  to  8  except there are two pairs of terminal blocks instead of one. Those skilled in the art will understand that a header assembly according to the present invention can have terminal blocks in addition to the one or two pairs shown. There can be three, four or more pairs. Additionally, it may be desired to have a header assembly where a bore only communicates with one terminal block which is not in a co-axial relationship with a second terminal block.  
         [0044]     However, the header assembly  150  differs from the header assembly  10  in that it is not secured to the housing lid  168  by anchors. Instead, header assembly  150  is mounted to the lid  168  by an adhesive material  180 , and the like. As shown in  FIG. 9 , this necessitates that the header assembly  150  include passageways  182  and  184  extending from the lower surface  186  thereof to communicate with the terminal blocks. For the sake of clarity, this drawing only shows one set of passageways for one of the feedthrough wire pairs  172 ,  174 . However, those skilled in the art will understand that there are as many passageways as there are terminal blocks and associated feedthrough wires.  
         [0045]     In that respect the feedthrough wires  172 ,  174  are received in the passageways  182 ,  184  to contact respective terminal blocks  152 ,  154  when the header assembly  150  is supported on the lid  168 . A laser beam as a joining device is then directed through the side passageways  187 ,  188  to weld the feedthrough wires in place, electrically contacted to the terminal blocks. Other joining means are contemplated such as soldering, brazing, epoxy, and the like.  
         [0046]     A co-axial conductor  164  is then inserted into the header assembly  150  in electrical contact with the terminal blocks, as previously discussed with respect to header assembly  10  shown in FIGS.  1  to  7 . The lead of the co-axial conductor  164  is retained in place in the terminal blocks by respective set screws  190  extending through passageways  186 ,  188  and apertures in the side walls of the terminal blocks to contact the conduction leads.  
         [0047]     Another distinction between the header assemblies  10  and  150  is the method of closing the housing for the medical device in the latter embodiment. In the case of header assembly  150 , the feedthrough wires are connected to the terminal blocks before being connected to the medical device circuitry. This necessitates that the hermetic housing be constructed by first mounting the lid  168  on one of the clam shells  24 ,  26 . The header assembly  150  is then secured to the lid  168  such as by adhesive, and the like. Next, the feedthrough wires are connected to the internal components of the medical device. Finally, the other clam shell is mated to the first clam shell and sealed thereto to complete the hermetic housing. A suture bore  192  is also provided.  
         [0048]      FIG. 10  shows another embodiment of a header assembly  200  according to the present invention. This header assembly is similar to the header assembly  150  of FIGS.  8  and  9  in that it is not molded to anchors provided on the lid. Rather, header assembly  200  is molded as a separate piece and later connected to a lid  202  having first and second upstanding lugs  204  and  206 . The lugs  204 ,  206  are provided with through apertures  208  and  210  generally aligned parallel to the upper surface of the lid  202 .  
         [0049]     The header is provided with a pair of spaced apart inlets  212  and  214  sized and positioned to receive the lugs  204 ,  206 . The header assembly  200  is further provided with through bores  216  and  218  which align with the apertures  208 ,  210  when the header assembly is positioned on the lid  202 . As the header assembly  200  is positioned on the lid  202 , feedthrough wires  220  and  222  previously connected to the terminal blocks (not shown) by welding through setscrew passageways (not shown) are received in respective openings  224 ,  226  in the lid. As in the other header assembly embodiments, the wires  220 ,  222  are insulated from the lid by ceramic-to-metal seals  228 ,  230 , and the like. Pins  232  and  234  are then inserted into the respective through bores  216 ,  218  and apertures  208 ,  210  to complete the connection. Preferably, the exposed ends of the pins are sealed by a polymeric plug, such as a silicon septum plug, and the like, to prevent them from working loose and to provide a smooth outer surface for the header assembly.  
         [0050]      FIGS. 11 and 12  show a book mold  250  for molding any one of the header assemblies  10 ,  150  and  200  according to the present invention. The book mold  250  comprises first and second mold portions  252  and  254  connected together by a hinge  256 . The benefit of a book mold is that either or both of the first and second mold portions  252 ,  254  can be changed to provide a header assembly having a desired shape without necessarily having to change the entire mold.  
         [0051]     The second mold portion  254  includes posts  258  and  260  on which respective terminal blocks  262  and  264  are supported. When the molding process is complete, the posts  258  and  260  coincide with the passageways through which the welds between the feedthrough wires and the terminal blocks are made for header assemblies  150  and  200 , and the apertures which receive set screws for securing the electrical connection between the lead of a co-axial conductor and the terminal blocks for all of the present invention header assemblies.  
         [0052]     A pin  266  having the shape of the lead of a co-axial conductor is positioned in the second mold portion  254  received in the respective terminal blocks  262  and  264 . Inserts  268  and  270  are supported on the second mold portion  254  abutting the shaped pin  266  from the back of the mold portion, i.e., that portion of the mold lying in the plane of the paper for  FIG. 11  and extending toward the reader. These inserts  268 ,  270  coincide with passageways  182 ,  184  for the header assembly  150 . The second mold portion  254  is then secured to the first mold portion  252  to provide a cavity having the shape of the to be manufactured header assembly. In that respect, the header assembly is formed laying on its side such that surface  272  of the second mold portion  254  forms the front wall  94  of header assembly  10  while surface  274  of the first mold portion  252  forms the back wall  96  thereof. Mold structure  276  forms the suture openings of the various header assemblies.  
         [0053]     The closed book mold  250  is provided with a channel  278  which mates with the barrel of a molding machine (not shown) to inject a charge of polymeric material therein to form the header assembly. Various polymeric materials are contemplated by the scope of the present invention including high durometer polyurethane or polysulfane resins.  
         [0054]      FIGS. 13 and 14  show another embodiment of a terminal sleeve  300  for connecting a feedthrough wire to the lead of a conductor according to the present invention. Terminal sleeve  300  is a generally cylindrical member having a lead opening  302  disposed along its longitudinal axis and aligned along a bore  304  for the lead. A threaded aperture  306  receives a set screw (not shown) and the like, for securing the lead inside sleeve  300 . The sleeve is supported in a body  308  of polymeric material having a passageway  310  aligned with the aperture  306 . The passageway  310  serves to admit a joining device, such as a laser, for welding the feedthrough wire to the sleeve  300  and for positioning the set screw in the threaded aperture  306 .  
         [0055]      FIGS. 15 and 16  show another embodiment of a terminal  320  comprising a cylinder  322  supporting an internal coil spring  324 . The cylinder  322  and spring  324  have coincident openings aligned along a bore  326  for receiving the lead  328  of a conductor. The opposed ends  330  and  332  of the cylinder are curled inwardly to retain the coil spring in place. When the lead  328  is moved along the bore  326  and into the terminal  320 , the spring expands in a radial manner to capture the lead therein in a tight-fitting relationship. This terminal eliminates the need for a set screw, and the like, although one can be used if desired. A feedthrough wire  334  is connected to the terminal supported in a body of polymeric material  336 .  
         [0056]     FIGS.  17  to  19  illustrate another embodiment of a terminal  340  comprising a cylinder  342  supporting at least one leaf spring  344 . The cylinder  342  has an opening  346  aligned along a bore  348  for receiving the lead  350  of a conductor. The opposed ends  352  and  354  of the cylinder are crimped to retain the leaf spring in place, disposed parallel to the longitudinal axis of the bore  348 . When the lead is moved along the bore  348  and into the terminal  340 , the leaf spring  344  deflects to exert a biasing force on the lead captured therein. The ends of the leaf spring are captured in the cylinder such that the spring does not misalign as the lead moves into and out of the cylinder  342  and bore  348 . This terminal eliminates the need for a set screw, although one can be used if desired. A feedthrough wire  356  is connected to the terminal supported in a body of polymeric material  358 .  
         [0057]     Now, it is therefore apparent that the present invention accomplishes its intended objects. While embodiments of the present invention have been described in detail, that is for the purpose of illustration, not limitation.

Technology Category: 1