Patent Publication Number: US-7711435-B2

Title: Pre-positioned storable implantable medical device assembly allowing in package charging and method

Description:
RELATED APPLICATION 
   This application claims priority from provisional U.S. Application Ser. No. 60/508,199, filed Oct. 2, 2003, and is a division of U.S. application Ser. No. 10/836,312, issued as U.S. Pat. No. 7,308,316 on 11 Dec. 2007 filed Apr. 30, 2004, which are hereby incorporated by reference in their entirety. 

   FIELD OF THE INVENTION 
   This invention relates to implantable medical devices and, in particular, to charging devices, systems and methods for implantable medical devices. 
   BACKGROUND OF THE INVENTION 
   Implantable medical devices for producing a therapeutic result in a patient are well known. 
   Examples of such implantable medical devices include implantable drug infusion pumps, implantable neurostimulators, implantable cardioverters, implantable cardiac pacemakers, implantable defibrillators and cochlear implants. Of course, it is recognized that other implantable medical devices are envisioned which utilize energy delivered or transferred from an external device. 
   A common element in most of these implantable medical devices is the need for electrical power in the implanted medical device. The implanted medical device typically requires electrical power to perform its therapeutic function whether it be driving an electrical infusion pump, providing an electrical neurostimulation pulse or providing an electrical cardiac stimulation pulse. This electrical power is derived from a power source. 
   Typically, a power source for an implantable medical device is a rechargeable power source such as rechargeable batteries and, in particular, lithium ion batteries. Such batteries can have a capacity which is exhausted much earlier than the useful life of the implantable medical device. 
   Electrical power can be transcutaneously transferred to the implanted medical device to recharge the rechargeable batteries through the use of inductive coupling. An external power source temporarily positioned on the surface of the skin of the patient can recharge the implanted medical device&#39;s batteries. In fact, many systems and methods have been used for transcutaneously inductively recharging a rechargeable power source used in an implantable medical device. 
   Transcutaneous energy transfer through the use of inductive coupling involves the placement of two coils positioned in close proximity to each other on opposite sides of the cutaneous boundary. The internal coil, or secondary coil, is part of or otherwise electrically associated with the implanted medical device. The external coil, or primary coil, is associated with the external power source or external charger, or recharger. The primary coil is driven with an alternating current. A current is induced in the secondary coil through inductive coupling. This current can then be used to charge, or recharge, an internal power source. 
   BRIEF SUMMARY OF THE INVENTION 
   Implantable medical devices are commonly shipped from the manufacturer to a medical facility where implantation of the device is performed. It is preferable that the implantable medical device not be in a fully charged state following manufacture and during shipment, storage and ultimately use. Ultimate battery life can be improved if the implantable medical device is not fully charged when shipped. Typically, an implantable medical device can be far from a fully charged and typically about eighty percent (80%) charged when shipped. 
   However, implanting an implantable medical device without a full charge is not desirable. Soon after implantation, it is generally desirable for the newly implanted medical device to be programmed, if necessary, utilized while initially implanted in the patient and monitored by medical personnel soon. 
   As noted above, inductive charging of the implanted medical device usually requires placing an external antenna directly on the skin of the patient at the site of implantation. However, the implantation site will typically still be recovering from the trauma of implantation immediately or soon after implantation. The implantation site can be adversely affected by the external charging unit if charging of the newly implanted medical device is attempted. Therefore, it is desirable to put off charging a newly implanted medical device for as long as possible, or typically one full charge period of the implanted medical device. 
   Contrary to conventional shipping techniques designed to ensure maximum battery life, it is desirable for an implantable medical device to be fully charged at the time of implantation. This will allow a maximum amount of time for the implantation site to heal before transcutaneous charging is attempted. 
   During shipment and storage, an implantable medical device is usually contained in a sterile environment in a storage container, such as a box. This would help to prevent contamination of the implantable medical device with germs, for example, and would help prevent subsequent infection of the patient upon implantation. Removal of the implantable medical device from the sterile environment of the shipping and/or storage container could subject the implantable medical device to the risk of contamination. 
   However, as noted above, charging of implantable medical device usually requires very close placement of an external antenna to the secondary coil of the implantable medical device in order to achieve effective inductive coupling. Such close placement is extremely difficult with the implantable medical device contained in the sterile environment of the shipping and/or storage container. 
   Thus, medical practitioners are often faced with a dilemma of removing the implantable medical device from the sterile environment of the container and being able to implant a fully charged medical device, or ensuring that the implantable medical device remains sterile but only being able to implant a partially charged medical device which could limit early use of the medical device or subject the already traumatized implantation site to the additional trauma of an external antenna soon after implantation. 
   In one embodiment, the present invention provides a storable implantable medical device assembly. An implantable medical device has a secondary coil operatively coupled to therapeutic componentry. A container for holding the implantable medical device has a first face. The implantable medical device is arranged in the container with the secondary coil positioned within a distance of the first face allowing charging of the implantable medical device without disturbing the container. The container has indicia representative of a lateral location on the first face aligned with the secondary coil of the implantable medical device. Thus, the indicia may be utilized to place an external antenna in order to charge the implantable medical device without disturbing the container. 
   In another embodiment, the present invention provides a shipping container for an implantable medical device having a secondary coil operatively coupled to therapeutic componentry. A container for holding the implantable medical device has a first face. The container is configured to hold the implantable medical device in the container with the secondary coil positioned within a distance of the first face allowing charging of the implantable medical device without disturbing the container. The container has indicia representative of a lateral location on the first face aligned with the secondary coil of the implantable medical device. Thus, the indicia may be utilized to place an external antenna in order to charge the implantable medical device without disturbing the container. 
   In another embodiment, the present invention provides a method of supplying an implantable medical device assembly having a secondary coil operatively coupled to therapeutic componentry. The implantable medical device is held in a container having a first face. The implantable medical device is arranged in the container with the secondary coil positioned within a distance of the first face with the distance allowing charging of the implantable medical device without disturbing the container. Indicia on the container is positioned on the container representative of a lateral location on the first face aligned with the secondary coil of the implantable medical device. The implantable medical device is charged without disturbing the container. 
   In a preferred embodiment, a center of the secondary coil and the indicia are centered on the first face of the container. 
   In a preferred embodiment, the indicia is placed on the first face of the container. 
   In a preferred embodiment, the indicia is placed on at least one face of the container adjacent to the first face. 
   In a preferred embodiment, the indicia is placed on a plurality of faces of the container adjacent to the first face. 
   In a preferred embodiment, an interior of the container holding the implantable medical device is sterile. 
   In a preferred embodiment, the container is an internal container contained within an outer container. 
   In a preferred embodiment, the indicia is positioned inside an outer layer of the container and with at least a portion of the outer container covering at least a portion of the indicia being transparent. 
   In a preferred embodiment, the indicia is represented by the implantable medical device and transparency of at least a portion of the first face of the container. 
   In another embodiment, the present invention provides a storable implantable medical device assembly. An implantable medical device has a secondary coil operatively coupled to therapeutic componentry. A container for holding the implantable medical device in the container with the secondary coil positioned within a distance of the first face allowing charging of the implantable medical device without disturbing the container. The implantable medical device is located in a predetermined position within the container. Thus, an external antenna may be placed with respect to the predetermined position in order to charge the implantable medical device without disturbing the container. 
   In another embodiment, the present invention provides a shipping container for an implantable medical device having a secondary coil operatively coupled to therapeutic componentry. A container holds the implantable medical device with the secondary coil positioned within a distance of the first face allowing charging of the implantable medical device without disturbing the container. The implantable medical device is located in a predetermined position within the container. Thus, an external antenna may be placed with respect to the predetermined position in order to charge the implantable medical device without disturbing the container. 
   In another embodiment, the present invention provides a method of supplying an implantable medical device assembly having a secondary coil operatively coupled to therapeutic componentry. The implantable medical device is held in a container with the secondary coil positioned within a distance of the first face allowing charging of the implantable medical device without disturbing the container. The implantable medical device is located in a predetermined position within the container. An external charging antenna is positioned with respect to the predetermined position. The implantable medical device is charged without disturbing the container. 
   In a preferred embodiment, the predetermined position results in the secondary coil being laterally centered on the first face of the container. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates an implantable medical device implanted in a patient; 
       FIG. 2  is a block diagram of an implantable medical device; 
       FIG. 3  is a detailed block diagram of an implantable medical device implanted sub-cutaneously and an associated external charging device in accordance with an embodiment of the present invention; 
       FIG. 4  is a cross-sectional side view of an implantable medical device implanted sub-cutaneously and an associated bracket for use with an external antenna; 
       FIG. 5  is a cross-section of a container holding implantable medical device in accordance with an embodiment of the present invention; 
       FIG. 6  is a top view of the embodiment illustrated in  FIG. 5 ; 
       FIG. 7  is a cross-section similar to  FIG. 5  with external antenna positioned to charge implantable medical device, and 
       FIG. 8  illustrates an alternative embodiment with the charging location centered on the face of the container. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The entire content of provisional U.S. Application Ser. No. 60/508,199, filed Oct. 2, 2003, and from U.S. application Ser. No. 10/836,312, filed Apr. 30, 2004, is hereby incorporated by reference. 
     FIG. 1  shows implantable medical device  16 , for example, a drug pump, implanted in patient  18 . The implantable medical device  16  is typically implanted by a surgeon in a sterile surgical procedure performed under local, regional, or general anesthesia. Before implanting the medical device  16 , a catheter  22  is typically implanted with the distal end position at a desired therapeutic delivery site  23  and the proximal end tunneled under the skin to the location where the medical device  16  is to be implanted. Implantable medical device  16  is generally implanted subcutaneously at depths, depending upon application and device  16 , of from 1 centimeter (0.4 inches) to 2.5 centimeters (1 inch) where there is sufficient tissue to support the implanted system. Once medical device  16  is implanted into the patient  18 , the incision can be sutured closed and medical device  16  can begin operation. 
   Implantable medical device  16  operates to infuse a therapeutic substance into patient  18 . Implantable medical device  16  can be used for a wide variety of therapies such as pain, spasticity, cancer, and many other medical conditions. 
   The therapeutic substance contained in implantable medical device  16  is a substance intended to have a therapeutic effect such as pharmaceutical compositions, genetic materials, biologics, and other substances. Pharmaceutical compositions are chemical formulations intended to have a therapeutic effect such as intrathecal antispasmodics, pain medications, chemotherapeutic agents, and the like. Pharmaceutical compositions are often configured to function in an implanted environment with characteristics such as stability at body temperature to retain therapeutic qualities, concentration to reduce the frequency of replenishment, and the like. Genetic materials are substances intended to have a direct or indirect genetic therapeutic effect such as genetic vectors, genetic regulator elements, genetic structural elements, DNA, and the like. Biologics are substances that are living matter or derived from living matter intended to have a therapeutic effect such as stem cells, platelets, hormones, biologically produced chemicals, and the like. 
   Other substances may or may not be intended to have a therapeutic effect and are not easily classified such as saline solution, fluoroscopy agents, disease diagnostic agents and the like. Unless otherwise noted in the following paragraphs, a drug is synonymous with any therapeutic, diagnostic, or other substance that is delivered by the implantable infusion device. 
   Implantable medical device  16  can be any of a number of medical devices such as an implantable therapeutic substance delivery device, implantable drug pump, cardiac pacemaker, cardioverter or defibrillator, as examples. 
   In  FIG. 2 , implantable medical device  16  has a rechargeable power source  24 , such as a Lithium ion battery, powering electronics  26  and therapy module  28  in a conventional manner. Therapy module  28  is coupled to patient  18  through one or more therapy connections  30 , also conventionally. Rechargeable power source  24 , electronics  26  and therapy module  28  are contained in hermetically sealed housing  32 . Secondary charging coil  34  is attached to the exterior of housing  32 . Secondary charging coil  34  is operatively coupled through electronics  26  to rechargeable power source  24 . In an alternative embodiment, secondary charging coil  34  could be contained in housing  32  or could be contained in a separate housing umbilically connected to electronics  26 . Electronics  26  help provide control of the charging rate of rechargeable power source  24  in a conventional manner. Magnetic shield  36  is positioned between secondary charging coil  34  and housing  32  in order to protect rechargeable power source  24 , electronics  26  and therapy module  28  from electromagnetic energy when secondary charging coil  34  is utilized to charge rechargeable power source  24 . 
   Rechargeable power source  24  can be any of a variety power sources including a chemically based battery or a capacitor. In a preferred embodiment, rechargeable power source is a well known lithium ion battery. 
     FIG. 3  illustrates an alternative embodiment of implantable medical device  16  situated under cutaneous boundary  38 . Implantable medical device  16  is similar to the embodiment illustrated in  FIG. 2 . However, charging regulation module  42  is shown separate from electronics  26  controlling therapy module  28 . Again, charging regulation and therapy control is conventional. Implantable medical device  16  also has internal telemetry coil  44  configured in conventional manner to communicate through external telemetry coil  46  to an external programming device (not shown), charging unit  50  or other device in a conventional manner in order to both program and control implantable medical device and to externally obtain information from implantable medical device  16  once implantable medical device has been implanted. Internal telemetry coil  44 , rectangular in shape with dimensions of 1.85 inches (4.7 centimeters) by 1.89 inches (4.8 centimeters) constructed from 150 turns of 43 AWG wire, is sized to be larger than the diameter of secondary charging coil  34 . Secondary coil  34  is constructed with 182 turns of 30 AWG wire with an inside diameter of 0.72 inches (1.83 centimeters) and an outside diameter of 1.43 inches (3.63 centimeters) with a height of 0.075 inches (0.19 centimeters). Magnetic shield  36  is positioned between secondary charging coil  34  and housing  32  and sized to cover the footprint of secondary charging coil  34 . 
   Internal telemetry coil  44 , having a larger diameter than secondary coil  34 , is not completely covered by magnetic shield  36  allowing implantable medical device  16  to communicate with the external programming device with internal telemetry coil  44  in spite of the presence of magnetic shield  36 . 
   Rechargeable power source  24  can be charged while implantable medical device  16  is in place in a patient through the use of external charging device  48 . In a preferred embodiment, external charging device  48  consists of charging unit  50  and external antenna  52 . Charging unit  50  contains the electronics necessary to drive primary coil  54  with an oscillating current in order to induce current in secondary coil  34  when primary coil  54  is placed in the proximity of secondary coil  34 . Charging unit  50  is operatively coupled to primary coil by cable  56 . In an alternative embodiment, charging unit  50  and antenna  52  may be combined into a single unit. Antenna  52  may also optionally contain external telemetry coil  46  which may be operatively coupled to charging unit  50  if it is desired to communicate to or from implantable medical device  16  with external charging device  48 . Alternatively, antenna  52  may optionally contain external telemetry coil  46  which can be operatively coupled to an external programming device, either individually or together with external charging unit  48 . 
     FIG. 4  is cross-sectional view of implantable medical device  16  implanted in patient  18  approximately one centimeter under cutaneous boundary  38  creating bulging area  110 , an area of the body of patient  18  in which the skin of patient  18  is caused to bulge slightly due to the implantation of implantable medical device  16 . Bulging area  110  is an aid to locating the position of external antenna  52  relative to secondary coil  34 . Bracket  84  can be positioned roughly in the area where implantable medical device  16  is implanted. Opening  108  in bracket  84  can aid is establishing the location of implantable medical device. Bracket  84  can be roughly centered over bulging area  110 . After external antenna  52  is coupled to bracket  84 , then primary coil  54  can be generally centered on implantable medical device  16 . 
   However, secondary coil  34  may not be centered with respect to implantable medical device  16 . This can occur due to a variety of reasons such as the need for operatively coupling secondary coil  34  to charging regulation module  42 . Connections to make this operative coupling may require physical space on one side of internal antenna  68  which may cause secondary coil  34  not to be centered on implantable medical device  16 . It is also possible that the attachment of internal antenna  68  to housing  32  can cause secondary coil  34  not to be centered on implantable medical device  16 . Regardless of the cause, if secondary coil  34  is not centered on implantable medical device  16 , then centering bracket  84  on bulging area  110  may not optimally position primary coil  54  with respect to secondary coil  34 . Any offset in the position of primary coil  54  and secondary coil  34  may not result in the most efficient energy transfer from external antenna  52  to implantable medical device  16 . 
   Inductive coupling between primary coil  54  of external antenna  52  and secondary coil of implantable medical device  16  is accomplished at a drive, or carrier, frequency, f carrier , in the range of from eight (8) to twelve (12) kiloHertz. In a preferred embodiment, the carrier frequency f carrier , of external antenna  54  is approximately nine (9) kiloHertz unloaded. 
   However, implantable medical device  16  is shipped to the implantation location and, possibly, stored before implantable medical device  16  can be implanted into patient  16 . A preferred embodiment of the present invention (see  FIG. 5 ) allows implantable medical device  16  to be shipped, and possibly, stored in a partially charged state, or even a completely discharged state. Container  120  holds implantable medical device  16  securely utilizing packing material  122  and  124 . Implantable medical device  16  is positioned with secondary coil  34  located distance  126  away from one face  128  of container  120 . Distance  126  is selected such that implantable medical device  16  can be charged using external antenna  52  positioned near or against face  128  on container  120  without opening the sterile portion of container  120  or removing implantable medical device  16  from container  120 . In a preferred embodiment, distance  126  has the same guidelines as the distance implantable medical device  16  is implanted below the skin surface, or from 1 centimeter (0.4 inches) to 2.5 centimeters (1 inch). Of course, distance  126  could be greater or less than these dimensions depending upon charging requirements and cushioning requirements. Generally, charging conditions in container  120  are not as stringent as charging conditions in an implanted condition so, in appropriate circumstances, the requirements on distance  126  may be relaxed. 
   As shown in  FIG. 4 , secondary coil  34  is not centered on implantable medical device  16 . In  FIG. 6  indicia  130  on face  128  of container  120  is indicative of the center of secondary coil  34  (shown by dashed lines although not visible in  FIG. 6 ). Indicia  130  may be any marking which would indicate the approximate laterally centered location of secondary coil  34  on face  128 . Indicia  130  is shown as cross hairs but may also be any other suitable indicia, as for example, a bulls eye or outline or shadow of antenna  52 . Indicia  130  may be applied to face  128  or may be formed into face  128 , painted or marked on face  128 . Indicia  130  may appear separate or may be incorporated into other markings or designs on face  128 . It is also possible that indicia  128  is not actually on face  128  but could be located on adjacent sides of container  120 , for example, but still giving an indication of the approximate lateral (to face  128 ) location of secondary coil  34 . It is only important that indicia  130  be visible enough to allow a user to properly located external antenna  52  in order to charge implantable medical device  16 . 
     FIG. 7  illustrates container  120  holding implantable medical device  16  with external antenna  52  containing primary coil  54  properly positioned with respect to indicia  130  on, or near, face  128  to be able to properly charge implantable medical device  16  without disturbing the sterile environment of implantable medical device  16 . 
   In a preferred embodiment, the center of indicia  130 , i.e., the indication of the center of secondary coil  34 , be nearly exactly the center of face  128  of container  120  as shown in  FIG. 8 . Making the center of indicia  130  also the center of face  128  eliminates the possibility of misalignment if a box lid is attached incorrectly to the rest of container, for example. 
   Alternatively, with implantable medical device  16  having been located in a predetermined position within container  120 , e.g., with secondary coil  34  laterally centered on face  128 , indicia  130  may be completely omitted. Knowing that secondary coil  34  is centered on face  128  of container  120 , external antenna  52  may simply be positioned laterally centered on face  128  of container  120 , i.e., matching the predetermined location of implantable medical device  16 , and secondary will be properly positioned for charging. In this alternative, indicia  130  in  FIG. 8  would be eliminated. 
   Although implantable medical device  16  has been illustrated as being held in a single container  120 , it is to be recognized and understood that other configurations are possible and contemplated to be within the scope of the present invention. For example, implantable medical device  16  could be contained in a smaller, sterile container which in turn is shipped in a larger container providing, for example, cushioned during shipment. Implantable medical device  16  could still be charged by opening the larger container without disturbing the sterile container and charging implantable medical device  16  therein. In this case, indicia  130  could be represented on either the larger container, the smaller container or some combination as long as external antenna can be properly located for charging. 
   It is also contemplated that other, non-standard forms of indicia  130  could be utilized. For example, sterile container  120 , or a sub-container, could be transparent and indicia  130  could be located within container  120 , or sub-container, and could even be implantable medical device  16  itself or evidenced on implantable medical device  16 . 
   It is recognized that implantable medical device  16  could be shipped or stored fully discharged, partially charged or essentially fully charged. Charging, full or partial, could still be desired, as for example, topping off the charge of implantable medical device  16  before implantation. 
   It is also recognized and understood that secondary coil  34  could be separate from, completely apart from or only semi-attached to the remainder of implantable medical device  16 . In this case, the positioning and indicia  130  would still apply to the portion of the apparatus or assembly containing secondary coil  34  or to secondary coil  34  separately. 
   Thus, embodiments of the external power source for an implantable medical device having an adjustable magnetic core and system and method related thereto are disclosed. 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.