Implantable medical device with external recharging coil electrical connection

[0002] The present application is related to the following copending applications entitled “Implantable Medical Device With External Recharge Coil” by inventors Kast et al. (attorney docket number P8970.00), “Implantable Medical Device With Recharging Coil Electro-Magnetic Shield” by inventors Kast et al. (attorney docket number P9399.00) which are not admitted as prior art with respect to the present invention by its mention in this cross reference section.

[0003] This disclosure relates to an implantable medical device and more specifically to a rechargeable implantable medical device that produces a therapy for the human body.

[0004] The medical device industry produces a wide variety of electronic and mechanical devices for treating patient medical conditions. Depending upon medical condition, medical devices can be surgically implanted or connected externally to the patient receiving treatment. Clinicians use medical devices alone or in combination with drug therapies and surgery to treat patient medical conditions. For some medical conditions, medical devices provide the best, and sometimes the only, therapy to restore an individual to a more healthful condition and a fuller life. Examples of implantable medical devices include neuro stimulators, drug delivery pumps, pacemakers, defibrillators, diagnostic recorders, and cochlear implants. Some implantable medical devices provide therapies with significant power demands. To reduce the size of the power source and to extend the life of the power source, some of these implantable device can be recharged while implanted with a transcutaneous recharge signal.

[0005] Some implantable medical devices configured for recharging have a recharging coil that is external to the medical device housing for improved efficiency. The recharging coil can be attached to the exterior of the medical device housing or remotely located from the medical device housing. The recharging coil is electrically connected to electronics carried inside the medical device housing via recharge feedthroughs carried on the medical device housing. Typically the recharging coil is manufactured from a material with good electrical properties but with poor corrosion resistance when exposed to conditions in the human body. The electrical integrity of the electrical connection between the recharging coil and the recharge feedthroughs can be placed at risk by corrosion.

[0006] For the foregoing reasons there is a need for an implantable medical device improved electrical connection between an external recharging coil and recharging feedthroughs.

[0007] The implantable medical device improve external recharging coil electrical connection is resistant to corrosion and accomplished with at least one electrical connection having a recharge coil connection and a recharge feedthrough connection. The external recharging coil, that is carried external to the medical device housing, is electrically connected to the recharging coil connection, and the recharge feedthrough connection is electrically connected to the recharge feedthrough. The recharge feedthrough is electrically connected to electronics carried inside the medical device housing and also a rechargeable power source also carried inside the housing. The medical device housing also carries a therapy connection for delivering therapy to a patient.

[0008] FIG. 1 shows an environment of a rechargeable implantable medical device embodiment;

[0009] FIG. 2 shows a rechargeable implantable medical device neuro stimulator embodiment;

[0010] FIG. 3 shows a neuro stimulator electronics block diagram embodiment;

[0011] FIG. 4 shows a rechargeable implantable medical device block diagram embodiment;

[0012] FIG. 5ashows a neuro stimulator embodiment;

[0013] FIG. 5bshows an exploded view of the neuro stimulator embodiment shown in FIG. 5a;

[0014] FIG. 6ashows another neuro stimulator embodiment;

[0015] FIG. 6bshows a recharging coil on the neuro stimulator embodiment shown in FIG. 6a;

[0016] FIG. 6cshows an enlarged view of an electrical connection embodiment between the recharging coil and the recharge feedthrough shown in FIG. 6b;

[0017] FIG. 7ashows another neuro stimulator embodiment;

[0018] FIG. 7bshows a recharging coil on the neuro stimulator embodiment shown in FIG. 7a;

[0019] FIG. 7cshows an enlarged view of another electrical connection embodiment between the recharging coil and the recharge feedthrough shown in FIG. 7b;

[0020] FIG. 8ashows a mechanical electrical connection embodiment;

[0021] FIG. 8bshows another mechanical electrical connection embodiment;

[0022] FIG. 8cshows a chemical electrical connection embodiment; and,

[0023] FIG. 9 shows a flowchart for forming an electrical connection embodiment.

[0024] FIG. 1 shows the general environment of one rechargeable implantable medical device 20 embodiment. An implantable neuro stimulator 22 is shown in FIG. 1, but other embodiments such as drug delivery pumps, pacemakers, defibrillators, diagnostic recorders, cochlear implants, and the like are equally applicable. Implantable medical devices 20 are often implanted subcutaneously approximated about one centimeter below the surface of the skin with an electrical lead or catheter extending to one or more therapy sites. The rechargeable implantable medical device 20 is recharged with a recharging device such as a patient charger or programmer that also has a charging capability.

[0025] Recharging an implanted medical device 20 generally begin with placing a recharging head containing a recharge coil near the proximal side of the medical device 20. Some rechargers have an antenna locator that indicates when the recharge head is aligned closely enough with the implanted medical device for adequate charge coupling. The recharge power transfer signal is typically a frequency in the range from 5.0 KHz to 10.0 KHz. The power transfer signal is converted into regulated DC power that is used to charge the power source. Once the recharge module fully changes the power source, the recharge module can be configured to serves as a power source for the implanted medical device while power is still received. Telemetry can also be conducted between the recharger and the implanted medical device 20 during recharging. Telemetry can be used aid in aligning the recharger with the implanted medical device 20, and telemetry can be used to manage the recharging process. Telemetry is typically conducted at a frequency in the range from 150 KHz to 200 KHz using a medical device telemetry protocol. For telemetry the recharger and implanted medical device 20 typically have a separate telemetry coil. The recharge coil can be multiplexed to also serve as a telemetry coil.

[0026] FIG. 2 shows a rechargeable implantable neuro stimulator 22 with a lead extension 24 and a lead 26 having electrical contacts 27. FIG. 3 shows a neuro stimulator electronics block diagram embodiment. The neuro stimulator 22 generates a programmable electrical stimulation signal. The neuro stimulator 22 electronics comprises a processor 28 with an oscillator 30, a calendar clock 32, memory 34, and system reset 36, a telemetry module 38, a recharge module 40, a power source 42, a power management module 44, a therapy module 46, and a therapy measurement module 48. All component of the neuro stimulator 22 are contained within or carried on a housing 50.

[0027] FIG. 4 shows an implantable medical device 20 with recharging coil block diagram. The implantable medical device 20 with recharging coil electrical connection comprises a housing 50, electronics 52, a rechargeable power source 42, a recharge coil 54, and at least one electrical connection 56 having a recharge coil connection 58, a connection wire 59, and a recharge feedthrough connection 60. The housing 50 has an interior cavity 62, an exterior surface 64, a therapy connection 66, and a recharge feedthrough 68. The therapy connection 66 can be any type of therapy connection 66 such as a stimulation feedthrough, a drug infusion port, a physiological sensor, and the like. There can also be more than one therapy connection 66 and a combination of different types of therapy connections 66. The housing 50 is hermetically sealed and manufactured from a biocompatible material such as titanium, ceramic, epoxy, and the like. The housing 50 contains electronics 52.

[0028] The electronics 52 are carried in the housing interior cavity 62 and configured to perform a medical therapy. The electronics 52 are electrically connected to both a therapy module 46, and the recharge feedthrough 68. The rechargeable power source 42 is carried in the housing interior cavity 62 and coupled to the electronics 52. The rechargeable power source 42 can be a physical power source such as a capacitor or a chemical power source such as a battery. The battery can be a hermetically sealed rechargeable battery such as a lithium ion (L+) battery and the like. The electronics 52 are coupled to the recharging coil 54.

[0029] The recharging coil 54 is carried on the housing exterior surface 64 such as the proximal face of the medical device 20. The recharging coil 54 is manufactured from a material with electromagnetic properties such as copper wire, copper magnet wire, copper litz woven wire, gold alloy and the like. The recharging coil 54 can be manufactured from a wide variety of wire sizes such as wire diameters in the range from about 0.040 cm (26 AWG, American Wire Gauge) to 0.016 cm (34 AWG), or any other suitable diameter. The recharging coil 54 is coupled to the recharging feedthroughs 68 with an electrical connection 56.

[0030] The electrical connection 56 has a recharge coil connection 58, a connection wire 59, and a recharge feedthrough connection 60. The electrical connection 56 couples the recharge coil 54 to the recharge feedthrough 68 to couple the recharge coil 54 to the electronics 52. There is at least one electrical connection 56 and there can be additional electrical connections 56. The electrical connection 56 serves as a means for connecting the recharging coil 54 to the recharge feedthrough 68 to couple the recharging coil 54 to the electronics 52. The electrical connection 56 is composed of an inert conductive metal resistant to corrosion such as niobum, titanium, tantalum, and the like. Niobum (Nb) wire is available from Anomet Products, Inc., Shrewsbury, Mass. The electrical connection 56 includes a connection wire 59 selected to form an electrical connection between the recharge coil connection 58 and the recharge feedthrough connection 60 such as a wire diameter such as in the range from about 0.025 cm (24 AWG) to 0.051 cm (30 AWG) or any other suitable diameter composed of an inert conductive metal resistant to corrosion such as niobum, titanium, tantalum, and the like.

[0031] The recharge coil connection 58 is connected to the recharging coil 54 with a mechanical connection, a chemical connection, or a combination of both types of connection. The mechanical connection can be any mechanical connection that provides a physically connection and an electrical connection such as a crimp joint, a twist joint, or the like. The crimp joint can be manufactured from a material such as copper, niobium, titanium, and the like. The chemical connection can be chemical connection that provides a physical connection and an electrical connection such as a weld, braze joint, solider joint, or the like. A hermetic seal 70 is placed over the electrical connection 56.

[0032] The hermetic seal 70 for the electrical connection 56 protects the electrical connection 56 from being exposed to biological tissue or fluids. The hermetic seal 70 is a biocompatible material and can take may forms including potting material, epoxy, polysulforne, polyurethane, silicone rubber, polymer encapsulation, coil cover with polymer seal, and the like.

[0033] FIG. 5ashows an embodiment of a neuro stimulator 22 and FIG. 5bshows the neuro stimulator 22 with some external components in an exploded view. The external components include a coil cover 72, a recharging coil 54, a magnetic shield 74, and a coil carrier 76. The coil carrier 76 has at least one positioning detail 78 located between the recharging coil 54 and the recharging feedthrough 68 for positioning the electrical connection 56. The positioning detail 78 secures the electrical connection 56.

[0034] FIGS. 6a-6cshow a neuro stimulator 22 embodiment with an electrical connection 56 embodiment. The recharge coil 54 is attached to an inert conductive metal with a crimp joint 58 embodiment that is secured in position with positioning details 78. FIGS. 7a-7cshow the neuro stimulator 22 embodiment with another electrical connection 56 embodiment. The recharge coil 54 is attached to an inert conductive metal with another crimp joint 58 embodiment that is secured in position with positioning details 78. FIGS. 8a-8bshow an enlarged view of the recharging coil 54 wire, crimp joint 58 embodiment, and connection wire 59. FIG. 8cshows an enlarged view of the recharging coil 54 wire, solder joint 58 embodiment, and connection wire 59.

[0035] FIG. 12 shows a flowchart for creating an electrical connection 56. The method for connecting a recharging coil 54 to a recharge feedthrough 68 in an implantable medical device 20 comprises the following elements. Placing 80 a recharging coil 54 on the housing exterior 64 of a medical device 20. Connecting the recharging coil 54 to an electrical connector. Connecting 82 the electrical connector 56 to a recharge feedthrough 68. Fixing 86 the electrical connector 56 in relation to the housing exterior 64. The method can also include protecting the electrical connection 56 with a hermetic seal 70.

[0036] Thus, embodiments of an implantable medical device 20 with an external recharging coil electrical connection are disclosed to provide an improved electrical connection between a external recharging coil 54 and a feedthrough 68. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.