Abstract:
A method for managing battery longevity of an implantable medical device (“IMD”) battery includes calculating a total IMD battery longevity value for an IMD and determining whether the total IMD battery longevity is below an optimal battery longevity value. At least one IMD parameter to be modified to improve the total IMD battery longevity value is automatically identified. The at least one automatically identified IMD parameter is adjusted to improve the total IMD battery longevity. Additionally, the improved total IMD battery longevity is displayed.

Description:
This application is a divisional of presently pending U.S. patent application Ser. No. 10/915,903, filed on Aug. 10, 2004, titled SYSTEMS AND METHODS FOR MANAGING THE LONGEVITY OF AN IMPLANTABLE MEDICAL DEVICE BATTERY, the contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to systems and methods for monitoring, configuring and managing implantable medical devices, and more particularly, to systems and methods for monitoring and managing battery longevity of the implantable medical devices. 
     BACKGROUND OF THE INVENTION 
     Cardiac pacemakers, implantable cardioverter defibrillators (“ICDs”), and cardiac resynchronization therapy (“CRT”) devices are all implantable medical devices (“IMDs”). Pacemakers are designed to emit pacing stimuli to one or more chambers of the heart to treat bradyarrhythmia. ICDs typically have pacemaker functions and also include high voltage output capability that can be used to treat potentially lethal tachyarrhythmias. CRT devices provide pacing therapy to synchronize the left and right ventricles as a treatment for heart failure. CRT devices may or may not have high voltage defibrillation capability (CRT-P or CRT-D). 
     These devices are battery powered and, once implanted, require regular follow-up by a physician or health care professional to assess proper system operation and continued remaining battery capacity. The follow-ups typically occur at regular intervals, for example, every six months. Modern IMDs can communicate with an external computing device in a bi-directional fashion. This external computing device, known as a “programmer,” allows the physician or health care professional to retrieve various diagnostic data, review stored history about the patient and device operation, and change various parameters of the device. The programmer also can show information related to battery status. 
     Batteries for IMDs typically use lithium iodide (Lil), lithium silver vanadium pentoxide (SVO), or lithium carbon monoflouride (CFx) chemistries. Depending on the chemistry, battery depletion status can be assessed by the device by measuring battery voltage, the time required to charge internal capacitors, use of a coulomb charge counter, or some combination of these or other methods. Specific algorithms for determining battery status vary by manufacturer, chemistry, and individual device. 
     Overall longevity for IMDs is estimated during the product development cycle. Models of battery capacity, expected variations in circuit performance, and clinical use conditions are all taken into account in these models. From this modeling effort, longevity estimates are created for various assumed clinical use conditions. The Instructions for Use (IFU) that is included in the finished device packaging and labeling will contain these battery longevity estimates. 
     During the life of the device, the estimated battery longevity remaining may be determined from a simple calculation of the estimated total longevity minus the portion of life already consumed from the battery. Many IMDs currently marketed can make such calculations and display them to the user through a programmer. 
     The longevity of an IMD may vary widely depending upon clinical use conditions. The programmed amplitude of pacing pulses, for example, can affect CRT device longevity by a factor of two or more (i.e., half the typical lifetime), depending on the number of pacing pulses the CRT device emits. Many physicians and health care professionals are surprised at the impact these clinical use conditions and parameter settings have on device longevity and express displeasure when overall longevity varies significantly from typical values. 
     Thus, a need exists for systems and methods that can inform physicians or health care professionals of circumstances that are leading to sub-optimal (shorter than usual device longevity, and can allow the physicians or health care providers to understand (and perhaps modify) specific parameters that are causing the sub-optimal longevity. 
     SUMMARY 
     A method for managing battery longevity of an implantable medical device (“IMD”) battery includes calculating a total IMD battery longevity value for an IMD and determining whether the total IMD battery longevity is below an optimal battery longevity value. At least one IMD parameter to be modified to improve the total IMD battery longevity value is automatically identified. The at least one automatically identified IMD parameter is adjusted to improve the total IMD battery longevity. Additionally, the improved total IMD battery longevity is displayed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the Figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
         FIG. 1  is a schematic drawing showing one embodiment of a system, including an implantable medical device (“IMD”), that can be used to monitor and manage battery longevity for an IMD battery; 
         FIG. 2  is a block diagram showing some components of one embodiment of an IMD that can be used in the present invention; 
         FIG. 3  is a block diagram showing some components of one embodiment of an external programming device that can be used with the present invention; 
         FIG. 4  is a flow chart illustrating one embodiment of a method for monitoring and managing battery longevity of an IMD battery; 
         FIG. 5  is a flow chart illustrating one embodiment for calculating a remaining IMD battery longevity value; 
         FIG. 6  is a screen shot of one embodiment of a user interface display screen that can be used to display battery longevity information to a user; 
         FIG. 7  is a screen shot of one embodiment of a user interface display screen that can display battery status information, including an interface for displaying and/or adjusting IMD parameters that may be affecting battery longevity; 
         FIG. 8  is a screen shot of the user interface display screen of  FIG. 6 , but showing examples of how sub-optimal battery longevity warnings can be displayed; and 
         FIG. 9  is a screen shot of the user interface display screen of  FIG. 7 , but showing examples of how IMD parameters that may be affecting battery longevity can be displayed and/or highlighted. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, the purpose of this invention not only is to inform physicians or health care professionals of the device longevity remaining, but also to specifically draw their attention to situations in which overall device longevity will be significantly shorter than for typical devices and to enable them to understand and/or modify specific parameters that are causing the sub-optimal longevity. 
     In some embodiments, the system (and/or methods) of the present invention can work in conjunction with existing algorithms for calculating and/or displaying remaining device battery longevity estimates. In accordance with these embodiments, the system can calculate the overall expected longevity for a device and notify a user, for example, via a programmer screen icon (or some other display feature), that the device longevity is sub-optimal. The system then allows the user to navigate to another screen in the programmer, which can display the current values of the various parameters that determine battery life. The algorithm determines which parameters are outside of normal use settings and indicates those to the user. The user then is allowed to enter changes to those values to determine what impact the changes would have to battery longevity. The user then is allowed to make the changes to the device, if appropriate. The result is that at follow-up visits, the physician or health care professional is notified of conditions that will lead to sub-optimal device battery longevity and can be given an opportunity to make changes that will improve longevity. 
     Referring now to  FIG. 1 , one embodiment of a system  100  for monitoring and managing battery longevity of an implantable medical device is shown. In accordance with the illustrated embodiment, system  100  includes an implantable medical device (“IMD”)  102  and an external programming device  104 . IMD  102  and external programming device  104  can communicate via a wireless communication link  112 . 
     IMD  102  can be any type of implantable medical device that includes a battery. For example, IMD  102  can be cardiac rhythm management device (“CRM”), a ventricular assist blood pump, a drug delivery pump, a drug infusion device, a neurostimulating device, or any other suitable implantable device that includes a battery. In the embodiment illustrated in  FIG. 1 , IMD  102  is a CRM device, which is implanted within a patient&#39;s body  106  and coupled to the patient&#39;s heart  108  by a lead system  110 . Examples of implanted CRM devices  102  include (but are not limited to) pacemakers, cardiac resynchronization (“CRT”) devices, implantable cardioverter/defibrillators (“ICDs”), pacer/defibrillators, and the like. 
     Referring now to  FIG. 2 , one embodiment of an IMD  102  is illustrated. In accordance with the illustrated embodiment, IMD  102  comprises a processor  202 , a battery  204 , communication circuitry  206 , therapy circuitry  208 , and a memory  210 . Communication circuitry  206 , therapy circuitry  208  and memory  210  all are in electrical communication with processor  202 , as is illustrated by arrows  212 . In addition, battery  204  is configured to provide power to some or all the power consuming components within IMD  102 . In the illustrated embodiment, for example, battery  204  provides power to communication circuitry  206 , therapy circuitry  208  and memory  210  via electrical connection  214 . In addition, as illustrated, processor  202  can receive power, as well as other battery parameters, such as current drain, depth of discharge, etc., from battery  204  via connection  216 . As discussed in more detail below, the battery parameters can be used to determine battery longevity and other battery statistics. 
     As one skilled in the art will appreciate, processors and memory devices are well known in the art, and the specific type and/or style of processor or memory device that can be used in IMD  102  is not limited. Accordingly, processor  202  can be any suitable processing device currently known or hereinafter developed, and memory device  210  can be any suitable memory device currently known or hereinafter developed. 
     Communication circuitry  206  is circuitry that allows IMD  102  to communicate with other devices, such as external programming device  104 , other IMDs, or other external devices. As discussed above, IMD  102  communicates with other devices via a wireless connection; e.g., wireless communication link  112 . The wireless connection can be, for example, a near-field radio frequency (RF) communication connection, a far-field RF communication connection, an acoustical communication connection, an optical communication connection, or any other suitable wireless communication connection. 
     In one embodiment, communication circuitry  206  can include circuitry for both near-field RF telemetry and far-field RF telemetry. For example, one embodiment of communication circuitry that can be used in IMD  102  is disclosed in Published U.S. Patent App. No. US 2003/0114897 A1, published on Jun. 19, 2003, and entitled “Implantable Medical Device with Two or More Telemetry Systems,” and Published U.S. Patent App. No. U.S. 2003/0114898 A1, published on Jun. 19, 2003, and entitled “Telemetry Duty Cycle Management System for an Implantable Medical Device,” both of which are incorporated by reference herein for all purposes. 
     In addition, in other embodiments, power saving wireless communication circuitry and methods can be used. For example, the IMD communication circuitry  206  can be configured to reside in a power-saving, sleep mode for a majority of the time. In accordance with this embodiment, communication circuitry  206  can be configured to “wake-up” on a periodic basis to communicate with an external device. Upon “wake-up” the external device will monitor for RF activity, and if the external device locates it, communication between the IMD and the external device can be initiated. There are a number of different ways IMD power-saving modes can be implemented, and the present invention is not limited to any particular one. Indeed, the aforementioned Published U.S. Patent App. Nos. US 2003/0114897 A1 and US 2003/0114898 A1 disclose different ways of implementing IMD power-saving modes, which, as discussed above, are incorporated herein by reference for all purposes. In addition, alternative embodiments of power management systems and methods that can be used in the present invention are disclosed in Published U.S. Patent App. No. US 2003/0149459 A1, published on Aug. 7, 2003, and entitled “Methods and Apparatuses for Implantable Medical Device Telemetry Power Management,” the entirety of which is incorporated by reference herein for all purposes. 
     Further, in accordance with other embodiments, communication circuitry  206  can be configured to communicate with an intermediary telemetry device, which, in turn, can facilitate communication with external programming device  104 . One example of this type of configuration is disclosed in Published U.S. Patent App. No. US 2003/0130708, published on Jul. 10, 2003, and entitled “Two-Hop Telemetry Interface for Medical Device,” the entirety of which is incorporated by reference herein for all purposes. Further, other configurations for RF telemetry are known, and communication circuitry  206  can embody those configurations, as well. Thus, as one skilled in the art will appreciate, communication circuitry  206  is not limited by any particular configuration or communication means. 
     Therapy circuitry  208  comprises circuitry for providing one or more therapeutic functions to a patient. For example, therapy circuitry  208  can include circuitry for providing heart pacing therapy, cardiac defibrillation therapy, and/or cardiac resynchronization therapy, drug delivery therapy, or any other therapy associated with a suitable IMD. In the case of cardiac therapy (e.g., pacing, defibrillation, etc.), therapy circuitry  208  includes cardiac leads  110  for delivering the therapy to particular locations in the heart. 
     In the embodiment illustrated in  FIG. 1 , external programming device  104  provides a user interface for system  100 . The user interface allows a physician or other healthcare provider or caregiver to interact with IMD  102  through a wireless communication link  112 . Wireless communication link  112  provides for bi-directional data communication between implanted CRM device  102  and external programming device  104 , and as discussed above, can comprise any suitable wireless communication link  112 , such as, a near-field RF communication connection, a far-field RF communication connection, an acoustical communication connection, an optical communication connection, or any other suitable wireless communication connection. 
     In one embodiment, RF telemetry link  112  provides for data transmission from IMD  102  to external programming device  104 . This may include, for example, transmitting real-time physiological data acquired by IMD  102 , extracting physiological data acquired by and stored in IMD  102 , extracting therapy history data stored in IMD  102 , and extracting data indicating an operational status of IDM  102  (e.g., lead impedance, battery status, battery longevity information, etc.). In addition, wireless communication link  112  can transmit data from external programming device  104  to IMD  102 . This may include, for example, programming IMD  102  to acquire physiological data, programming IMD  102  to perform at least one self-diagnostic test (such as for a device operational status), programming IMD  102  to deliver at least one therapy, or changing one or more therapy parameter for the IMD. 
     Referring now to  FIG. 3 , one embodiment of an external programming device  104  is shown. In the illustrated embodiment, external programming device  104  comprises a processor  302  (and associated memory (not shown)), a user interface display  304 , communication circuitry  306  and a user date entry interface  308 . User interface display  304 , communication circuitry  306 , and patient interface  308  all are in electrical communication with processor  302 , as is illustrated by arrows  312 . 
     As one skilled in the art will appreciate, and as discussed above with reference to IMD  102 , processors and memory devices are well known in the art, and the specific type and/or style of processor or memory devices that can be used in external programming device  104  are not limited. Accordingly, processor  302  can be any suitable processing device currently known or hereinafter developed. Similarly, the memory (not shown) can be any suitable memory device currently known or hereinafter developed. 
     In addition, communication circuitry  306  is circuitry that allows external programming device  104  to communicate with IMD  102 , and perhaps other devices. Thus, if IMD  102  is communicating via an RF connection, communication circuitry  306  comprises RF communication circuitry, as well. Similarly, if optical or acoustical communication connections are used, communication circuitry  306  is adapted to facilitate such connections. Thus, communication circuitry  306  can be any circuitry adapted to facilitate the wireless communications with IMD  102 . As one skilled in the art will appreciate, such circuitry is known in the art, and therefore, will not be discussed in detail herein. 
     In the embodiment illustrated in  FIG. 3 , external programming device  104  includes a user interface display  304  and a user data entry interface  308 , both of which facilitate communication with a user, such as a physician, or other health care provider or caregiver. For example, user interface display  304  is adapted to visually display or otherwise communicate various different IMD parameters and information for a user to view, and can be an electronic graphical user interface, a print-out display, or any other suitable interface display. Such interfaces are well known in the art, and thus, the present invention is not limited to any particular interface display. Examples of a few visual screens that may be displayed by user interface display  304  are shown in  FIGS. 6-9 , and are discussed in more detail below. 
     Similarly, user data entry interface  308  is an interface that allows a user to enter data and/or adjust IMD parameter values. Data entry interface  308  can be a keyboard device, a mouse, a touch screen, voice recognition technology, or any other suitable data entry interface. Again, data entry interfaces are well known in the art, and thus, the present invention is not limited to any particular data entry device or technology. 
     Referring now to  FIG. 4 , one embodiment of a method for monitoring and/or managing battery longevity for an IMD battery is illustrated by flow chart  400 . In accordance with the illustrated embodiment, the method comprises the steps of: (1) calculating an elapsed IMD battery longevity value (block  410 ); (2) calculating a remaining IMD battery longevity value (block  420 ); (3) calculating a total IMD battery longevity value from the elapsed value and the remaining value (block  430 ); (4) determining if the IMD battery longevity value is sub-optimal (block  440 ); (5) displaying and/or analyzing IMD parameters or settings that may be causing the sub-optimal longevity (block  450 ); and (6) adjusting parameters to perhaps improve the IMD battery longevity (block  460 ). 
     As one skilled in the art will appreciate, calculating an elapsed IMD battery longevity value is relatively straight forward, and in one embodiment, it merely is the elapsed battery life of the device since it was implanted in a patient. Also, there are a number of different methods and algorithms that can be used to calculate or determine a remaining battery longevity value; some of which are device and/or battery type dependent. Thus, any device longevity calculation algorithm or method can be used within the scope of the present invention. 
     Referring to  FIG. 5 , one embodiment of a method that can be used to calculate a remaining IMD battery longevity value (block  420 ) for a CRM device, such as a pacemaker, is illustrated by flow chart  500 . While the exemplary method illustrated in  FIG. 5  will be described herein with reference to a pacemaker, one skilled in the art will appreciate that a similar method can be used to determine a remaining battery longevity value for other CRM devices and other IMDs, such as defibrillators, CRT devices, drug delivery devices, blood pumps, etc. 
     The first step of the method of  FIG. 5  is to calculate a current drain for the IMD (e.g., pacemaker). In accordance with this particular embodiment, total pacemaker current drain at battery voltage can be calculated by:
 
 I   d   =I   q   +I   a   +I   v  
 
where I d  is the total pacemaker current drain, I q  is the quiescent current drain of the pacemaker control circuitry (typically 7-10 μA depending on mode), I a  is the Atrial pacing current, and I v  is the ventricular pacing current.
 
     Pacing current for a paced chamber can be calculated by: 
               I   via     =       P   100     ×     K   eff     ×     V   set     ×     C   eq     ×     LRL   60     ⁢     (     1   -     ⅇ   ⁢           ⁢     (       -   PW       Z   ×     C   eq         )         )     ×     10   6     ⁢           ⁢     (   µA   )             
where I v/a  is the pacing current for the appropriate atrial or ventricular chamber in μA, P is the percent paced, K eff  is an effective voltage multiplier setting (2.0 for pacing output of 3.5 volts), V set  is the output voltage in volts, C eq  is the equivalent pacing output capacitance formed by the series combination of the pacing supply capacitor and the output blocking capacitor (typically 2 μF) in Farads, LRL is the programmed lower rate limit (pacing rate) in pulses per minute (ppm), PW is the programmed pulse width in seconds, and Z is the pacing impedance in Ohms.
 
     Thus, for example, pacing a chamber at 100%, 60 ppm, with a 0.4 ms pulse width, and a 3.5 V pacing output into a 500 ohm load requires approximately 4.6 μA of pacing current. Total current drain when both chambers are being paced at 100% is about 18 μA. 
     Next, in accordance with the method illustrated in  FIG. 5 , a total pacemaker battery capacity is determined (block  520 ). Total battery capacity Q typically is current drain dependent for a Lithium Iodide based pacemaker (i.e., Q=f(I d )). Thus, as one skilled in the art will appreciate, overall capacity is lower at high current drain settings. A lookup table can provide the total battery capacity Q for the calculated current drain. A typical battery capacity at 20 μA current drain is about 1000 mAmp hours. 
     Next, an estimated battery longevity value L can be calculated as a function of current drain and total battery capacity as follows: 
             L   =       Q     I   d       ×     10   3     ×     1     8760   ⁢     (     hours/year     )                 
where L is battery longevity in years, Q is total battery capacity in mAmp hours (e.g. 1000), and I d  is current drain in μA.
 
     Thus, for a battery with a 1000 mA-hr capacity and a current drain of 18 μA, the estimated battery longevity is about 6.3 years. 
     Next, depth of battery discharge is determined (block  540 ). As one skilled in the art will appreciate, internal battery measurements determine depth of discharge. While historically, this measurement has been a direct measurement of battery voltage, a more accurate measurement is the time required to charge the internal pacing supply capacitors. In one embodiment, depth of discharge is determined from this measurement under defined conditions using a lookup table. The output is a percent discharged. 
     Finally, the remaining battery longevity can be calculated as a function of the total longevity and the percent battery discharged (block  550 ), as follows:
 
 T   ERT   =L− ( L×D   % )
 
where D %  is the percent battery discharged.
 
     After the remaining battery longevity value has been calculated, it can be displayed to a user, for example, using external programming device  104 . For example, as illustrated on screen  600  in  FIG. 6 , a battery longevity remaining value can be displayed on a screen for a user to view (see  602  and  604  in  FIG. 6 ). For pacemakers that use lithium iodide batteries, accuracy of remaining longevity typically increases toward elective replacement time (ERT). Thus, in the illustrated embodiment, the display can indicate “&gt;5.0 years” for calculations that indicate a longevity of greater than 5.0 years, and can show more accurate values as the time remaining gets smaller. 
     In the illustrated embodiment, if a user wants additional information about battery longevity and perhaps IMD parameter settings that may affect the battery longevity, the user can select a battery icon, such as icon  606  on screen  600 , to display more detail about battery status (see  FIG. 7 ). 
     Referring to  FIG. 7 , user interface display screen  700  shows additional detail about battery status. In addition, screen  700  includes a longevity calculator  702  that can display (and modify) IMD parameters that may affect battery longevity. For example, in the illustrated embodiment, the relevant IMD parameters include pacing output amplitude  704 , pulse width  706 , percent paced  708 , lead impedance  710  and pulse rate  712  for both the atrial and ventricle chambers. In addition, screen  700  can include a “gas gauge” display  714  showing battery life parameters, such as beginning of life (BOL), elective replacement near (ERN), elective replacement time (ERT), and end of life (EOL) parameters. When in this screen, a physician or clinician can modify the IMD parameters (e.g., parameters  704 - 712 ) on screen and analyze how remaining longevity would be impacted with the changes. This will be discussed in more detail below. 
     As mentioned above, once remaining battery longevity has been calculated, the system can determine if the overall or total battery longevity is sub-optimal (i.e., below the expected or average longevity). Overall or total battery longevity is the sum of the longevity already achieved by the device and the remaining longevity expected according to the calculations. Note that the longevity already achieved (also referred to as elapsed longevity) is a function of implant date and present date, both of which are available parameters in most IMDs. In accordance with one embodiment of the invention, external programming device  104  can analyze the overall or total battery longevity for IMD  102  and compare it to a nominal battery longevity value. In accordance with this embodiment, nominal longevity can be defined as the total battery longevity achieved when a pacemaker is paced 100% into both chambers at standard settings (e.g., pacing rate of 60 ppm, pacing output of 3.5 volts, and a pulse width of 0.4 ms) with a 500 ohm loads. In one embodiment, for example, the external programming device  104  can identify any IMD that will achieve a battery longevity of less than 80% of this nominal value. 
     Alternately, in accordance with another embodiment, the external programming device can identify any IMD that has an estimated total battery longevity that is less than a predetermined value. For example, in the case of a pacemaker, the predetermined value might be 4.0 years, or some other relevant value. Also, as one skilled in the art will appreciate, there may be other ways to classify a battery life as sub-optimal, which also can be used in the present invention. Thus, as one skilled in the art will appreciate, the present invention is not limited to any particular method for classifying a device longevity as sub-optimal. 
     If a device battery longevity is determined to be sub-optimal, a system summary screen, for example, screen  800  in  FIG. 8 , can display warning information for the user, such as displaying an exclamation mark  802  near the longevity remaining display and/or posting a battery longevity related clinical event  804  on the screen. Alternatively, other warning signals could be used, as well. 
     As a final step in the process, the external programming device can determine which IMD parameter settings, if any, are set to values that cause higher than normal current drain, thus resulting in a sub-optimal battery situation. For example, as illustrated on screen  900  of  FIG. 9 , parameters causing higher than normal current drain or parameters affecting the battery longevity can be highlighted. On screen  900 , suspect parameters  902 ,  904  and  906  are circled. However, other highlights can be used, such as, red text, a bright background, etc. If IMD parameters have already been set back to nominal or lower values, no parameters will be highlighted on the screen. 
     By highlighting the suspect parameters, the physician and/or clinician can identify the parameters and use the longevity calculator or other user interface to determine how best to optimize or improve remaining battery longevity. That is, a physician can modify IMD parameter settings using the longevity calculator or other interface to determine how changing parameters will affect battery longevity. The physician can perform multiple combinations and permutations of parameter changes to test battery longevity improvements, while still providing proper therapy to the patient. Once the physician determines a proper setting for the IMD, the external programming device can communicate the new settings to the IMD, which, in turn, will implement the changes. 
     While the example set forth above has focused on a dual-chamber pacemaker, one skilled in the art will appreciate that the methods and systems described herein can be applied to other implantable medical devices as well, including implantable defibrillators and cardiac resynchronization devices. Thus, the present invention is not limited to any particular IMD configuration. In addition, while the embodiment discussed above describes the external programming device as performing the steps necessary to calculate the remaining device longevity value and total device longevity value, and to determine whether total battery longevity is sub-optimal, one skilled in the art will appreciate that in other embodiments, some or all of these functions could be performed within the IMD itself. In those embodiments, the external programming device would perform the functions that the IMD does not. In most cases, however, the external programming device will be used to display device longevity information to the user, and the external programming device will be used to adjust IMD parameters to optimize or improve battery longevity. 
     In conclusion, the present invention provides novel systems and methods for monitoring and managing battery longevity for IMD batteries. While detailed descriptions of one or more embodiments of the invention have been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art without varying from the spirit of the invention. Therefore, the above description should not be taken as limiting the scope of the invention, which is defined by the appended claims. 
     Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.