US20060015150A1 - Method For Providing A One Piece Header Assembly Over Molded To An Implantable Medical Device - Google Patents

Abstract

The present invention is directed to a header assembly attachable to a medical device for the purpose of connecting its output terminals to at least one lead, the lead terminating at a target organ or portion of the body intending to be assisted. A number of leads are connectable to the header, including single and coaxial leads. The header assembly may be molded directly to the medical device or performed and then attached to the device casing, either by mechanical fastener and/or chemical adhesive.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• 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 that connect directly to feedthrough wires extending from inside the medical device to a conductor leading to the body organ or tissue being assisted.
• 2. Prior Art
• 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 the 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.
• 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
• 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 that are molded directly onto the lid of the medical device and pre-molded ones that are later secure to the medical device. In either case, the present header assemblies include terminal blocks that 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.
• 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
• FIG. 1 is an exploded view of aheader assembly10 for an implantablemedical device18.
• FIG. 2 is a perspective view of theheader assembly10 andmedical device18 shown inFIG. 1.
• FIG. 3 is a sectional view taken along line3-3 ofFIG. 2.
• FIG. 4 is a plan view, partly in phantom, of theheader assembly10.
• FIG. 5 is a side elevational view of theheader assembly10.
• FIG. 6 is a sectional view taken along line6-6 ofFIG. 5.
• FIG. 7 is a sectional view taken along line7-7 ofFIG. 5.
• FIG. 8 is an elevational view, partly in section and partly in phantom, of aheader assembly150 according to the present invention for themedical device18.
• FIG. 9 is a perspective view of theheader assembly150 connected tofeedthrough wires172,174 from the medical device.
• FIG. 10 shows the header assembly being secured to the casing by mechanical fasteners.
• FIG. 111 is a cross-sectional view of abook mold250 in an opened position for manufacturing a header assembly according to the present invention.
• FIG. 12 is a cross-sectional view of thebook mold250 ofFIG. 11 in a closed position.
• FIG. 13 is a broken away view, partly in phantom, of another embodiment of aterminal300 according to the present invention.
• FIG. 14 is a cross-sectional view along line14-14 ofFIG. 13.
• FIG. 15 is sectional view of another embodiment of aterminal320 prior to alead328 being inserted therein.
• FIG. 16 is a sectional view of the terminal ofFIG. 15 with thelead328 received therein.
• FIG. 17 is a sectional view of another embodiment of aterminal340 prior to alead350 being inserted therein.
• FIG. 18 is a cross-sectional view along line18-18 ofFIG. 17.
• FIG. 19 is a sectional view of the terminal ofFIGS. 17 and 18 with thelead350 received therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring now to the drawings, FIGS.1 to7 illustrate aheader assembly10 according to the present invention comprising at least one pair ofterminal blocks12 and14 partially surrounded by a moldedpolymeric header16 connected to an implantablemedical device18. Theterminal blocks12,14 provide for connecting a co-axial conductor20 from the medical device to a body tissue. The implantablemedical device18 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.
• The implantablemedical device18 is contained in ahousing22 of a material such as of stainless steel, and is shown in an exemplary form comprising first and secondmain clamshell portions24 and26. Theclamshells24 and26 are mated together and hermetically sealed about their periphery to provide an enclosure for the medical device including itscontrol circuitry28 and apower supply30 such as a battery (FIG. 3). Thebattery30 is connected to thecontrol circuitry28 byelectrical leads32 and34. There may also be a capacitor for a medical device such as a defibrillator.
• In particular, thefirst clamshell24 comprises spaced apartsidewalls36 and38 extending to and meeting withend wall40. Thesidewalls36,38 and theend wall40 meet each other at rounded corners and extend to afront wall42. Opposite thefront wall42 is aperipheral edge44 ofsidewalls36,38 andend wall40 while opposite theend wall40 is anopening46.
• Thesecond clamshell26 comprises spaced apartsidewalls48 and50 (FIG. 3) extending to and meeting withend wall52. Thesidewalls48 and50 andend wall52 meet at rounded corners and extend tofront wall54. Opposite the front wall is aperipheral edge56 of thesidewalls48 and50 andend wall52 while opposite theend wall52 is anopening58. Thefirst clamshell24 is sized to fit inside the periphery of thesecond clamshell26 in a closely spaced, lap joint relationship. This assembly forms a container having an opening60 leading therein where the coincidingopenings46 and58 of therespective clamshells24 and26 reside. The container opening60 has a generally rectangular shape.
• The benefit of having a lap joint construction for themating clam shells24 and26 is that when they are hermetically sealed together, such as by laser welding, the laser beam is prevented from compromising thecontrol circuitry28 andpower supply30 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 theperipheral edges44,56 of theclam shells24,26 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 inFIG. 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.
• Alid62 is hermetically sealed to the opening60 of the matedclamshells24,26. Thelid62 consists of spaced apart upper andlower surfaces64 and66 extending to and meeting with a surrounding edge68 (FIG. 3). The surroundingedge68 includes an inverted step or rim70 to assist in the sealing connection between thelid62 and the matedclamshells24,26. Preferably, thelid62 is sealed in place, such as by laser welding (not shown), to create thehermetic housing22 for the implantablemedical device18.
• While the medical device is shown being contained inside a housing ofmating clamshells24,26, the present invention is not intended to be so limited. Other types of housings such as prismatic, deep drawn, cylindrical are also contemplated.
• As shown inFIGS. 1 and 3, theupper surface64 of thelid62 includes a plurality of protrudinganchors72 that assist in joining theheader10 to the lid.Internal protrusions74 depend from thelower lid surface66 and assist in positioning the lid on the mated clamshells.
• Thelid62 further comprises at least twoopenings76 and78 through whichrespective feedthrough wires80 and82 pass. The feedthrough wires extend from a distal end positioned inside thehousing22 connected to thecontrol circuitry28 for themedical device18 to respective proximal ends disposed generally parallel to and spaced above theupper surface64 of thelid62. Thefeedthrough wires80,82 are electrically insulated from thelid62 by respective ceramic-to-metal seals or glass-to-metal seals84 and86.
• The proximal end offeedthrough wire80 is connected to the firstterminal block12 supported thereon while theother feedthrough wire82 is connected to a secondterminal block14 depending therefore. The terminal blocks12,14 are ring-shaped members of different diameters, sized to be in electrical contact with matching portions of thelead88 for aco-axial conductor90, as will be described in detail hereinafter.
• As shown inFIG. 3, the terminal blocks12 and14 are aligned in a co-axial relationship and encased in the moldedheader16 having abore92 providing communication to both of them. The moldedheader16 comprises spaced apart front andback walls94 and96 extending to a curvedupper wall98 and a generally planarbottom wall100. Thebottom wall100 is supported on theupper lid surface64 and retained in place by encasing the lid anchors72. Thebore92 is sized to receive theco-axial conductor lead88. 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.
• In that respect, the header assembly bore92 has afirst portion102 of a first diameter sized to receive adistal portion104 of theconductor lead88, a second,intermediate portion106 of a second, greater diameter sized to receive aproximal portion108 of thelead88 and a third portion110 of a still greater diameter than the intermediate portion. The terminal blocks12,14 have lead openings of diameters somewhat larger than the first andsecond bore portions102,106 so that theconductor lead88 is received therein in a tight fitting, electrically stable connection.
• Thefront wall94 of the moldedheader16 is provided with a pair ofpassageways112 and114 aligned perpendicularly with the longitudinal axis of thebore92.Passageway112 extends to a threadedaperture116 in the sidewall ofterminal block12 to provide for communication with thefirst bore portion102. The passageway and aperture threadingly receive asetscrew118 that contacts thedistal portion104 of theconductor lead88 to prevent loss of electrical contact between the lead and theterminal block12. Similarly,passageway114 extends to a threadedaperture120 in the sidewall ofterminal block14 to provide for communication with thesecond bore portion106. Asetscrew122 is received therein to contact theproximal portion108 of theconductor lead88, thereby maintaining electrical continuity between the lead and theterminal block14.
• An annular channel surrounds the third bore portion110 for capturing an O-ring124 therein. This helps to prevent body fluids and the like from contacting theconductor portions104 and108 received in the respective terminal blocks12 and14. A raisedseal126 further helps prevent body fluids from contacting theco-axial conductor lead88. Finally, theheader assembly10 is provideD with asuture bore128 adjacent to the conductor lead bore92. The suture bore128 aids a physician in securing the medical device inside a body.
• As known in the art, the end (not shown) of theco-axial conductor90 opposite that of thelead88 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 thelead88 andconductor90.
• FIGS. 8 and 9 show a further embodiment of aheader assembly150 according to the present invention. Theheader assembly150 comprises a polymeric material supporting a first pair ofterminal blocks152 and154 and a second pair ofterminal blocks156 and158. The terminal block pairs have lead openings aligned co-axially along respective conductor bores sized to receive the conductor leads160 and162 ofco-axial conductors164 and166. Thelid168 is provided with a ceramic-to-metal seal170 that electrically insulatesfeedthrough wires172,174,176 and178 from thelid168. The feedthrough wires are in electrical contact with respective terminal blocks152,154156 and158.
• In this respect, theheader assembly150 is similar to theheader assembly10 of FIGS.1 to8 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 that is not in a co-axial relationship with a second terminal block.
• However, theheader assembly150 differs from theheader assembly10 in that it is not secured to thehousing lid168 by anchors. Instead,header assembly150 is mounted to thelid168 by anadhesive material180, and the like. As shown inFIG. 9, this necessitates that theheader assembly150 includepassageways182 and184 extending from the lower surface186 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 pairs172,174. However, those skilled in the art will understand that there are as many passageways as there are terminal blocks and associated feedthrough wires.
• In that respect thefeedthrough wires172,174 are received in thepassageways182,184 to contact respective terminal blocks152,154 when theheader assembly150 is supported on thelid168. A laser beam as a joining device is then directed through theside passageways186,188 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.
• Aco-axial conductor164 is then inserted into theheader assembly150 in electrical contact with the terminal blocks, as previously discussed with respect toheader assembly10 shown in FIGS.1 to7. The lead of theco-axial conductor164 is retained in place in the terminal blocks byrespective set screws190 extending throughpassageways186,188 and apertures in the side walls of the terminal blocks to contact the conduction leads.
• Another distinction between theheader assemblies10 and150 is the method of closing the housing for the medical device in the latter embodiment. In the case ofheader assembly150, 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 thelid168 on one of theclamshells24,26. Theheader assembly150 is then secured to thelid168 such as by adhesive, and the like. Next, the feedthrough wires are connected to the internal components of the medical device. Finally, the other clamshell is mated to the first clam shell and sealed thereto to complete the hermetic housing. Asuture bore192 is also provided.
• FIG. 10 shows another embodiment of aheader assembly200 according to the present invention. This header assembly is similar to theheader assembly150 of FIGS.8 and9 in that it is not molded to anchors provided on the lid. Rather,header assembly200 is molded as a separate piece and later connected to alid202 having first and secondupstanding lugs204 and206. Thelugs204,206 are provided with throughapertures208 and210 generally aligned parallel to the upper surface of thelid202.
• The header is provided with a pair of spaced apartinlets212 and214 sized and positioned to receive thelugs202,206. Theheader assembly200 is further provided with throughbores216 and218 that align with theapertures208,210 when the header assembly is positioned on thelid202. As theheader assembly200 is positioned on thelid202,feedthrough wires220 and222 previously connected to the terminal blocks (not shown) by welding through setscrew passageways (not shown) are received inrespective openings224,226 in the lid. As in the other header assembly embodiments, thewires220,222 are insulated from the lid by ceramic-to-metal seals228,230, and the like.Pins232 and234 are then inserted into the respective throughbores216,218 andapertures208,210 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.
• FIGS. 11 and 12 show abook mold250 for molding any one of theheader assemblies10,150 and200 according to the present invention. Thebook mold250 comprises first andsecond mold portions252 and254 connected together by ahinge256. The benefit of a book mold is that either or both of the first andsecond mold portions252,254 can be changed to provide a header assembly having a desired shape without necessarily having to change the entire mold.
• Thesecond mold portion254 includesposts258 and260 on which respective terminal blocks262 and264 are supported. When the molding process is complete, theposts258 and260 coincide with the passageways through which the welds between the feedthrough wires and the terminal blocks are made forheader assemblies150 and200, 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.
• Apin266 having the shape of the lead of a co-axial conductor is positioned in thesecond mold portion254 received in the respective terminal blocks262 and264.Inserts268 and270 are supported on thesecond mold portion254 abutting the shapedpin266 from the back of the molded portion, i.e., that portion of the mold lying in the plane of the paper forFIG. 11 and extending toward the reader. Theseinserts268,270 coincide withpassageways182,184 for theheader assembly150. Thesecond mold portion254 is then secured to thefirst mold portion252 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 thatsurface272 of thesecond mold portion254 forms thefront wall94 ofheader assembly10 whilesurface274 of thefirst mold portion252 forms theback wall96 thereof.Mold structure276 forms the suture openings of the various header assemblies.
• Theclosed book mold250 is provided with achannel278 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.
• FIGS. 13 and 14 show another embodiment of aterminal sleeve300 for connecting a feedthrough wire to the lead of a conductor according to the present invention.Terminal sleeve300 is a generally cylindrical member having alead opening302 disposed along its longitudinal axis and aligned along a bore304 for the lead. A threadedaperture306 receives a setscrew (not shown) and the like, for securing the lead insidesleeve300. The sleeve is supported in abody308 of polymeric material having apassageway310 aligned with theaperture306. Thepassageway310 serves to admit a joining device, such as a laser, for welding the feedthrough wire to thesleeve300 and for positioning the setscrew in the threadedaperture306.
• FIGS. 15 and 16 show another embodiment of a terminal320 comprising acylinder322 supporting aninternal coil spring324. Thecylinder322 andspring324 have coincident openings aligned along abore326 for receiving thelead328 of a conductor. The opposed ends330 and332 of the cylinder are curled inwardly to retain the coil spring in place. When thelead328 is moved along thebore326 and into the terminal320, the spring expands in a radial manner to capture the lead therein in a tight-fitting relationship. This terminal eliminates the need for a setscrew, and the like, although one can be used if desired. Afeedthrough wire334 is connected to the terminal supported in a body ofpolymeric material336.
• FIGS.17 to19 illustrate another embodiment of a terminal340 comprising acylinder342 supporting at least oneleaf spring344. Thecylinder342 has anopening346 aligned along abore348 for receiving thelead350 of a conductor. The opposed ends352 and354 of the cylinder are crimped to retain the leaf spring in place, disposed parallel to the longitudinal axis of thebore348. When the lead is moved along thebore348 and into the terminal340, theleaf spring344 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 thecylinder342 and bore348. This terminal eliminates the need for a setscrew, although one can be used if desired. Afeedthrough wire356 is connected to the terminal supported in a body ofpolymeric material358.
• 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.

Claims (12)

1. A method for connecting an implantable medical device to a conductor terminating at a body organ intended to be assisted by the medical device, comprising the steps of:

a) providing the medical device having a housing containing control circuitry, at least one electrical energy storage device and at least a first and second feedthrough wires extending from the control circuitry through a wall of the housing to first and second distal ends located outside the housing;

b) connecting the first and second distal ends of the first and second feedthrough wires to respective first and second terminals, wherein the terminals includes first and second lead openings aligned in a first co-axial relationship; and

c) molding a body of polymeric material secured to the wall of the housing with the body having a bore communicating from outside the body to the first co-axial first and second lead openings of the terminals.

2. The method ofclaim 1 including providing the housing having third and fourth feedthrough wires extending from the control circuitry and through the wall of the housing to respective third and fourth terminals having third and fourth lead openings aligned in a second co-axial relationship along a second bore communicating from outside the body to the third and fourth terminals.

3. The method ofclaim 1 including providing the wall of the housing having anchors encased by the polymeric material to secure the body to the housing.

4. The method ofclaim 1 wherein the wall of the housing is a lid.

5. The method ofclaim 1 including providing the housing for the medical device comprising mating first and second clam shell housing portions closed by a lid.

6. The method ofclaim 1 including providing the first and second terminals having first and second apertures.

7. The method ofclaim 6 including inserting a lead of the conductor into the bore of the body and into the first and second lead openings of the first and second terminals aligned in the first co-axial relationship and then threading a threaded member into the first and second apertures of the respective first and second terminals to retain the lead in place.

8. The method ofclaim 6 including providing the body having first and second passageways in communication with first and second apertures in the respective first and second terminals.

9. The method ofclaim 1 including providing the bore having an annular channel supporting an O-ring for sealing about a lead of the conductor received in the first and second terminals.

10. The method ofclaim 1 including selecting the electrical energy storage device from a battery and a capacitor.

11. The method ofclaim 1 including selecting the medical device from the group consisting of hearing assist device, neurostimulator, cardiac pacemaker, drug pump and cardiac defibrillator.

12. The method ofclaim 1 including selecting the first and second terminals from the group consisting of a terminal block, a sleeve, a ring-shaped member supporting a coil spring and a ring shaped member supporting at least one leaf spring.

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