Abstract:
When a medical procedure is performed on a patient in whom an implantable medical device is implanted, the medical procedure may have undesired effects on the medical device, such as triggering a response that initiates therapy by the device that is unnecessary and potentially dangerous to the patient. Systems and methods may facilitate performing of such medical procedures on such patients by automatically reprogramming the medical device, monitoring for one or more detectable characteristics associated with the medical procedure to be performed, and automatically restoring normal operation of the IMD after the medical procedure is completed.

Description:
RELATED APPLICATIONS 
       [0001]    This application is related to copending U.S. patent application Ser. No. 12/332,768, entitled Systems and Methods for Operating an Implantable Device for Medical Procedures, filed Dec. 11, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Embodiments of the present invention generally pertain to implantable medical devices and more particularly to a non-programmable activation device that switches modes of operation of an implantable medical device and methods for using the activation device. 
         [0003]    An implantable medical device (IMD) is implanted in a patient to monitor, among other things, electrical activity of a heart and to deliver appropriate electrical therapy, as required. Implantable medical devices include pacemakers, cardioverters, defibrillators, implantable cardioverter defibrillators (ICD), neurostimulation devices, pain suppression devices, implantable spinal stimulators, implantable trauma stimulators, cardiac resynchronization therapy devices, ventricular-assist devices, implantable heart monitors, neurological stimulators, implantable drug pumps, cochlear implants, ultrasonic or electrical osteogenesis stimulators, and the like. The electrical therapy produced by an IMD may include pain suppression, pacing pulses, cardioverting pulses and/or defibrillator pulses to reverse arrhythmias (e.g., tachycardias and bradycardias) or to stimulate the contraction of cardiac tissue (e.g., cardiac pacing) to return the heart to normal sinus rhythm or to promote bone growth to accelerate healing of bone fractures, or to inject controlled amounts of fluids subcutaneously, or epidurally and the like. 
         [0004]    During different medical procedures, such as diagnostic imaging, a surgical procedure or a clinical examination, the IMD can be exposed to electric field, static magnetic fields, gradient magnetic fields, pulsed radio frequency (RF) fields or combined field effects. When the IMDs are exposed to certain external fields, such fields may interfere with normal operation of the IMD. For example, RF waves may induce energy on implanted leads or reduce the energy of pacing pulses resulting in loss of pacing capture. For example, an external magnetic field may generate magnetic forces on the IMD and on the leads and electrodes of the IMD. The magnetic forces may induce electric charges or potential on the leads and electrodes. The electric charges can cause over- or under-sensing of cardiac signals in the electrodes and leads. For example, the charges may cause the electrodes and leads to convey signals to the IMD that are not cardiac signals, but are treated by the IMD as cardiac signals. In another example, the charges may induce significant noise in sensed cardiac signals such that cardiac signals that are representative of an abnormal cardiac event go undetected by the IMD. 
         [0005]    Further, when patients who are implanted with an IMD are subjected to external electromagnetic interference, undesirable electric current and voltage could be induced by such interference and could create undesirable physiological effects, such as the induction of an arrhythmia or heat induced pain. Examples of IMD malfunctions have been traced to medical procedures, such as radiofrequency catheter ablation, electrocautary, dental procedures, magnetic resonance imaging (MRI) techniques, as well as other medical procedures. 
         [0006]    Magnetic resonance (MR) imaging systems generate relatively strong magnetic fields. For example, some known commercial MR imaging systems create magnetic fields on the order of 0.5 to 3.0 Tesla. MR Imaging systems may generate external magnetic fields of different strengths, such as 0.5 Tesla, 0.7 Tesla, 1.0 Tesla, 1.2 Tesla, 1.5 Tesla, 3 Tesla, etc. Some IMDs may operate safely while in certain modes, when exposed to lower strength magnetic fields. However, when IMDs are exposed to higher strength magnetic fields, the IMDs may not reliably operate in a physiologic safe manner in some modes. In order to safely operate in some external magnetic fields, the IMDs may switch modes to an “MR safe mode” or a “magnet mode.” The MR safe mode and magnet mode do not correspond to a particular pacing mode, but instead represents particular settings for certain parameters (e.g., pulse amplitude, pulse width, configuration, pacing mode, etc.). 
         [0007]    Methods have been proposed to reduce the effects of interference by MRI systems, or other medical procedures, on implantable medical devices. Some of these methods include reducing the effects of interference on the lead itself alone, or in combination with, changing the IMD settings. For example, certain conventional leads have increased insulation surrounding the lead body, or have wires or conductors within the lead with reduced diameter to limit the effects of the RF fields. However, adding insulation or reducing the size of wires or conductors may increase the cost of the lead and may decrease the effectiveness of the IMD. 
         [0008]    Another approach is to have a doctor or medical technologists specifically program the IMD immediately prior to the medical procedure to inhibit the IMD from delivering therapy in response to false positive of an abnormal physiological behavior. To perform the programming of the IMD, a trained programmer person manually loads the IMD with MR safe settings parameters. After the medical procedure is completed, the doctor or medical user must reprogram the IMD to the pre-procedure or patient related settings. Most doctors and medical examination personnel are not trained to operate an external IMD programming device. Instead, the doctors at the MRI facility and medical personnel are trained to perform a diagnostic imaging scan, a medical procedure or clinical examination. A separate group of doctors or medical personnel specialize in IMD implant, IMD programming and IMD related activity. Therefore, a trained IMD programmer person must also be present when a patient with an IMD undergoes certain types of scans, exams or procedures un-related to the IMD. The required presence of a trained IMD programmer person to support the IMD throughout a non-IMD related medical procedure, scan or exam adds to the cost of scan or exam procedure, and creates workflow burden. Additionally, a risk of introducing errors due to human interaction increases as an IMD is repeatedly reprogrammed before and after each scan, procedure or exam. 
         [0009]    A need remains for an improved method and device that can safely interact with an IMD before and after non-IMD related procedures. 
       SUMMARY 
       [0010]    In accordance with one embodiment, a method is provided for changing settings of an implantable medical device (IMD) prior to a medical procedure. The method includes configuring an IMD to perform tasks based on saved settings in an active parameter fields. The method also includes loading the active parameter fields with patient related settings, where the patient related settings have been configured to treat abnormal physiological behavior of a patient. The method further includes storing medical procedure related settings in long term memory of the IMD. The procedure related settings correspond to a medical procedure that may potentially be performed on the patient. Additionally, the method includes utilizing a portable external non-programmable activator (NPA) device to transmit a safe mode command to the IMD prior to the start of a medical procedure. In response to the safe mode command, the IMD automatically reconfigures to a procedure safe mode by loading the procedure related settings into the active parameter fields and operating the IMD based on the procedure related settings. The instructions to execute the method may be stored in an IMD control module. 
         [0011]    In accordance with one embodiment, a method is provided wherein upon receiving the safe mode command, the IMD performs a device state check to determine whether a present device state satisfies predetermined device state criteria. The IMD will not automatically reconfigure to the procedure safe mode when the present device state does not satisfy the predetermined device state criteria. The device state check may, by way of example, determine whether a present lead impedance satisfies lead impedance criteria. 
         [0012]    In accordance with one embodiment, a method is provided wherein upon receiving the safe mode command, the IMD performs a patient state check to determine whether a present patient state satisfies predetermined patient state criteria. The IMD will not automatically reconfigure to the procedure safe mode when the present patient state does not satisfy the predetermined patient state criteria. The patient state check will determine whether at least one heart rate, pacing threshold, and a need for pacing satisfies a corresponding patient state criteria. 
         [0013]    In accordance with one embodiment, a method for automatically switching the IMD between procedure related settings and patient related settings is provided. The method includes maintaining the IMD in the procedure safe mode until the IMD receives a procedure complete command from the NPA device. Also, the method includes removing the NPA device from a transmitting sensitive region, proximate to the IMD, during the medical procedure. The method excludes the NPA device transmitting the procedure related, or the patient related settings to the IMD. 
         [0014]    In accordance with one embodiment, a method for automatically switching the IMD between procedure related settings and patient related settings may include at least one of the medical procedures of image scanning, a surgical procedure and a clinical examination. Further, the medical procedure may represent at least one of an MR scan, CT scan, NM scan, PET scan, ultrasound scan, an X-Ray scan, a hemodynamic exam, a physiologic exam, an intracardiac exam and an ablation procedure. 
         [0015]    In accordance with one embodiment, the method for automatically switching the IMD between procedure related settings and patient related settings may include, after completion of the medical procedure, utilizing a non-programmable activator (NPA) device to transmit a procedure complete command to the IMD. The method may also include the IMD loading the patient related settings into the active parameter fields upon receiving the procedure complete command from the NPA device. 
         [0016]    In accordance with one embodiment, an implantable medical device (IMD) is provided. The IMD may be configured to couple to a lead located proximate to a heart of a patient. The IMD includes a control module configured to perform IMD related functions based on settings saved in active parameter fields for the control module. The IMD also includes active parameter fields being initially loaded with patient related settings, the patient related settings being configured to treat abnormal physiologic behavior of a patient. The IMD includes long term memory to store procedure related settings related to a medical procedure that may potentially be performed on the patient. The IMD further includes a transceiver. 
         [0017]    In accordance with one embodiment, the NPA device is provided. The NPA device transmits a safe mode command to the IMD. In response to the safe mode command, the IMD automatically reconfigures to a procedure safe mode by loading the procedure related settings into the active parameter fields and operating the IMD based on the procedure related settings. The IMD remains in the procedure safe mode until the IMD receives a procedure complete command transmitted from the NPA device. 
         [0018]    In an optional embodiment, after completion of the medical procedure, the NPA device is utilized to transmit a procedure complete command to the IMD. The IMD then loads the patient related settings into the active parameter fields upon receiving the procedure complete command. The embodiment also includes interrogating the IMD by the NPA device for a current state of the IMD and present IMD status information on the NPA device to the user. The embodiment includes storing a plurality of procedure related settings in the memory of the IMD associated with different medical procedures wherein the NPA device informs the IMD through the safe mode command to automatically reconfigure to a corresponding procedure safe mode by loading a select set of the procedure related settings into the active parameter fields. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
           [0020]      FIG. 1  illustrates an NPA device and an implantable medical device (IMD) coupled to a heart in accordance with one embodiment. 
           [0021]      FIG. 2  illustrates a block diagram of internal components of the NPA device shown in  FIG. 1  to switch an IMD into a procedure safe mode in accordance with an embodiment. 
           [0022]      FIG. 3  illustrates a block diagram of exemplary internal components of the IMD shown in  FIG. 1  to switch an IMD into a procedure safe mode in accordance with an embodiment. 
           [0023]      FIG. 4(   a ) illustrates a flow chart for a process to switch an IMD into a procedure safe mode in accordance with an embodiment. 
           [0024]      FIG. 4(   b ) Illustrates a flow chart to switch an IMD out of a procedure safe mode in accordance with an embodiment. 
           [0025]      FIG. 5  illustrates a flow chart for a process to query IMD status using the NPA to switch an IMD into a procedure safe mode in accordance with an embodiment. 
           [0026]      FIG. 6  illustrates a functional block diagram of an external device that is operated to interface with the IMD to switch an IMD into a procedure safe mode in accordance with an embodiment. 
           [0027]      FIG. 7  illustrates an embodiment for NPA device that can be used with multiple different procedures in accordance with an embodiment. 
           [0028]      FIG. 8  illustrates a distributed processing system in accordance with one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the present invention may be practiced. These embodiments, which are also referred to herein as “examples,” are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the embodiments may be combined or that other embodiments may be utilized, and that structural, logical, and electrical variations may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. In the description that follows, like numerals or reference designators will be used to refer to like parts or elements throughout. In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one. In this document, the term “or” is used to refer to a nonexclusive or, unless otherwise indicated. In this document, the term “patient related settings” refers to the settings of an IMD prior to a medical procedure. 
         [0030]    In the following detailed description, reference to medical procedures shall be given the broadest reasonable meaning. The term medical procedure shall include any activity directed at or performed on an individual with the object of improving health, treating disease or injury, or making a diagnosis and the like. For example, the medical procedure may be one where the patient is exposed to an electrical field, such as Electroneuronography, EEG topography, Electrical impedance tomography or the like. Similarly, the medical procedure may be one where the patient is exposed to a magnetic field, such as Magnetoencephalography, Magnetic therapy, Magnetic resonance imaging and the like. Alternatively, the medical procedure may involve introducing the individual to electromagnetic radiation, such as Scintillography, pulsed electromagnetic fields (PEMF) and the like. The medical procedure may further involve procedures that do not fall within the realm of conventional medicine. The medical procedures may also encompass surgical procedures, clinical examinations, therapies and the like. As used herein, the term normal is intended to encompass non-medical procedure conditions and operating parameters that correspond to non-medical procedure conditions. As used herein, the term “command” and the term “signal” may be used interchangeably. 
         [0031]      FIG. 1  illustrates a non-programming activator (NPA) device  144  for use with an implantable medical device (IMD)  100  coupled to a heart  102 , in accordance with an embodiment. 
         [0032]    The IMD  100  may be a cardiac pacemaker, an ICD, a defibrillator, an ICD coupled with a pacemaker, a cardiac resynchronization therapy (CRT) pacemaker, a cardiac resynchronization therapy defibrillator (CRT-D), neurostimulators and the like. The IMD  100  includes a housing  110  that is joined to leads  104 ,  106 ,  108 . The leads  104 ,  106 ,  108  are located at various locations of the heart  102 , such as an atrium, a ventricle, or both, to measure cardiac signals of the heart  102 . The leads  104 ,  106 ,  108  include the right ventricular (RV) lead  104 , the right atrial (RA) lead  106 , and the coronary sinus lead  108 . Electrodes are provided on the leads  104 ,  106 ,  108  for sensing cardiac signals and/or for delivering stimulus or stimulation pulses to the heart  102 . The housing  110  may be one of the electrodes and is often referred to as the “can”, “case”, or “case electrode.” 
         [0033]    The RV lead  104  includes an RV tip electrode  122 , an RV ring electrode  124 , and an RV coil electrode  126 . The RV lead  104  may include a superior vena cava (SVC) coil electrode  128 . The right atrial lead  106  includes an atrial tip electrode  112  and an atrial ring electrode  114 . The coronary sinus lead  108  includes a left ventricular (LV) tip electrode  116 , a left atrial (LA) ring electrode  118  and an LA coil electrode  120 . Alternatively, the coronary sinus lead  108  may be a quadropole or mulitpole lead that includes multiple electrodes  109 ,  111 ,  113 ,  115  disposed within the left ventricle. Leads and electrodes other than those shown in  FIG. 1  may be included in the IMD  100  and positioned in or proximate to the heart  102 . 
         [0034]    The IMD  100  monitors cardiac signals of the heart  102  to determine if and when to deliver stimulus pulses to one or more chambers of the heart  102 . The IMD  100  may deliver pacing stimulus pulses to pace the heart  102  and maintain a desired heart rate and/or shocking stimulus pulses to treat an abnormal heart rate such as tachycardia or bradycardia. 
         [0035]    The IMD  100  includes a control module configured to perform IMD  100  related functions based on settings saved in active parameter fields for the control module. The active parameter fields are initially loaded with patient related settings configured to treat abnormal physiologic behavior of a patient. The IMD  100  also includes a long term memory to store procedure related settings that correspond to a medical procedure that may potentially be performed on the patient. The IMD  100  further includes a transceiver that transmits and receives signals from the NPA device  144 . 
         [0036]    The NPA device  144  is “non-programming” in that the device  144  does not have inputs, nor functionality, that allows a user to enter user-determined values for any IMD parameters. For example, unlike an IMD programmer, the NPA device  144  cannot be used to enter new values such as heart rate, pacing mode, sensing mode, stimulus strength, and the like. The NPA device  144  has limited functionality and is only able to change the IMD  100  between settings that are already stored in the IMD  100 . The NPA device  144  cannot be used to enter new (un-stored) values for settings. The NPA device  144  has a limited user-interface, namely a user interface without a keyboard. The NPA device  144 , in one embodiment, may be a portable handheld device that communicates with the IMD  100 . The portable external NPA device  144  transmits a safe mode command to the IMD  100 . The IMD  100 , in response to the safe mode command, automatically reconfigures to a procedure safe mode by loading the procedure related settings into the active parameter fields. The IMD  100  operates based on the procedure related settings while the procedure is being performed on the individual. The IMD  100  remains in the procedure safe mode even when the NPA device  144  is removed from transmit sensitive region, proximate to the IMD  100 . 
         [0037]    In one embodiment, the IMD  100  remains in the procedure safe mode until the IMD  100  receives a procedure complete command transmitted from the NPA device  144 . After completion of the medical procedure, the NPA device  144  is used to transmit a procedure complete command to the IMD  100 . Upon receiving the procedure complete command from the NPA device  144 , the IMD  100  loads the original patient related settings back into the active parameter fields from a memory. 
         [0038]    Optionally, the IMD  100  may store a plurality of procedure related settings in the memory of the IMD  100  associated with different medical procedures. The NPA device  144  informs the IMD  100  through the safe mode command to automatically reconfigure to a corresponding procedure safe mode by loading a select set of the procedure related settings. 
         [0039]    Optionally, the NPA device  144  may interrogate the IMD  100  for a current state of the IMD  100  and present IMD  100  status information on the NPA device  144  to the user. 
         [0040]    The NPA device  144  includes a safe mode ON button  140  which when pressed sends a command  142  to the IMD  100  to switch active parameter fields to procedure related settings. The NPA device  144  also includes a safe mode OFF button  130  which when pressed sends a procedure complete command  142  to the IMD  100 . In one embodiment the NPA device  144  includes a status request button  134  which when pressed sends a signal  142  to the IMD  100  requesting IMD  100  to relay the IMD&#39;s  100  status back to NPA device  144 . The NPA device  144  further includes a label  136  to display information related to a medical procedure. For example, the label  136  may display the name of a medical procedure, for which the NPA device  144  is enabled. The NPA device  144  includes an indicator red light  132  and an indicator green light  138  to inform a user of NPA device  144  the status of communication sent and received from an IMD  100 . Optionally, the NPA device  144  may include a speaker that allows users to communicate with NPA device  144  via audible sound. Optionally, the NPA device  144  includes an audio input device that takes audio command as input. The audio input activates the NPA device  144  to communicate a procedure related or status command from the NPA device  144  to the IMD  100 . Optionally, the NPA device  144  may be formed as an integral part of another system or device or the like. For example, the NPA device  144  may be built into a MR scanner to send procedure related and status commands to the IMD  100  from the MRI system console. 
         [0041]      FIG. 2  illustrates a block diagram  200  of typical internal components of the NPA device  144 . The NPA device  144  includes a telemetry circuit  216 , which enables the NPA device  144  to communicate  142  with the IMD  100 . Although telemetry commonly refers to wireless communication mechanisms, the telemetry also encompasses data transferred over other media, such as a telephone or computer network, optical link or other wired communications. Many modern telemetry systems take advantage of the low cost and ubiquity of global system for mobile communications (GSM) networks by using short message service (SMS) to receive and transmit telemetry communication. For example, the NPA device  144  may communicate safe mode signal  142  or IMD  100  status request signal  142  to the IMD  100  via the telemetry circuit  216 . Optionally, the NPA device  144  may also communicate with the programmer device via the telemetry circuit  216  to automatically program medical procedure related settings in the IMD  100 . 
         [0042]    The NPA device  144  further includes a transceiver circuit  202 , which accepts signals from a transmission medium and decodes or translates the signals into a form that can drive local circuits. For example, the transceiver circuit  202  acts as a liaison between the telemetry circuit  216  and the processor  204 . 
         [0043]    The NPA device  144  includes a processor  204  to execute a sequence of stored instructions required to perform related programs. For example, the processor  204  accepts signal input from the transceiver circuit  202  or a user interface  212 , executes related computer program and sends the output to components of the NPA device  144  that is in charge of executing the action. For example, an input command to switch safe mode parameters is issued by the user interface  212 . The processor  204  identifies the command, processes the command and sends the code to the transceiver circuit  202  to send a signal to the IMD  100 , via telemetry circuit, to switch active parameters with patient related settings or procedure related settings. In another example, the transceiver circuit receives the status signal from the IMD  100  and sends the signal to the processor  204 . The processor  204  then processes the signal, executes the computer program that activates an appropriate indicator to communicate to the user the appropriate result. In one embodiment, the processor may be a low level embedded system. In another embodiment, the processor may be a complex system and may include microprocessors, control circuitry, memory, logic and timing circuit and other input or output circuits. 
         [0044]    The NPA device  144  includes a memory  206  providing NPA device  144  the ability to store, retain, and recall information. For example, the NPA device  144  may store a temporary command in the memory  206  to be processed by the processor. Optionally, the memory  206  may store logs of communication between the NPA device  144  and the IMD  100 . The memory  206  may be a short term storage memory in one embodiment and a long term memory in another embodiment. 
         [0045]    The NPA device  144 , in one embodiment, includes a user interface  212 , allowing the user to interact with the NPA device  144 . The user interface  212  provides a means of input, allowing the users to manipulate a system. For example, the user interface  212  includes a safe mode ON button  140 , which sends a command to the IMD 100  to switch active parameter fields to procedure related settings and store patient related settings in a section within a memory. The user interface  212  may also include a status button  134 , which allows a user, of the NPA device  144 , to get current state of the IMD  100 . For example, the user interface  212  may include a safe mode OFF button  134 , which commands the IMD  100  to switch the active parameter fields back to the patient related settings. The user interface also provides a means of output, allowing the system to indicate the effect of the user&#39;s manipulation or interaction with the system. For example, the user interface  212  of the NPA device  144  may include an indicator  214  that may communicate the status of the signal sent or received from the IMD  100  to user. The indicator, in one embodiment, may be green  138  and a red  132  light emitting diode (LED). Where the green  138  light may indicate that the communication between the NPA device  144  and the IMD  100  was successful. Alternatively, the red  132  light may indicate failed communication between the NPA device  144  and the IMD  100 . For example, the user interface may include an indicator  214 , a safe mode ON button  140 , a safe mode OFF button  130 , and a check status button  134 . Alternatively, the user interface  212  may be a touch screen. In another embodiment, the user interface  212  may be audio controlled, e.g., the user interface may control the NPA device  144  by voice. In another embodiment, the user interface  212  may be a hybrid design including buttons, a touch screen, and/or audio control. 
         [0046]    The NPA device  144  includes a battery  208 , providing electric power for the operation of the NPA device  144 . The battery  208  may be a disposable battery, designed to be used once and discarded when the batteries are exhausted, or the battery  208  may be a rechargeable battery, designed to be recharged and used multiple times. 
         [0047]    The NPA device  144  includes a connectivity  210  module that provides multiple degrees of communication between the NPA device  144  and a clinical workflow. The clinical workflow may mean any form of communication between patient, clinicians, administrators, and families through the innovative use of the data, voice, and video. Alternatively, clinical workflow may be a process that accomplishes a definite step in an activity in the clinical care of patient. 
         [0048]    The communication between the NPA device  144  and the clinical workflow may be via wired or wireless connectivity  210 . The connectivity  210  between the NPA device  144  and the clinical workflow may be internet, a voice over IP (VoIP) gateway, a local plain old telephone service (POTS) such as a public switched telephone network (PSTN), a cellular phone based network, or the like. Alternatively, the connectivity  210  may be a local area network (LAN), a campus area network (CAN), a metropolitan area network (MAN), or a wide area network (WAN). The connectivity  210  module serves to provide a network that facilitates the transfer/receipt of information such as cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, IMD  100  programming data, safe mode signal to the IMD  100 , and the like. 
         [0049]      FIG. 3  illustrates a block diagram of exemplary internal components of the IMD  100 . The IMD  100  includes the housing  300  that includes a left ventricle tip input terminal (V L  TIP)  302 , a left atrial ring input terminal (A L  RING)  304 , a left atrial coil input terminal (A L  COIL)  306 , a right atrial tip input terminal (A R  TIP)  308 , a right ventricular ring input terminal (V R  RING)  310 , a right ventricular tip input terminal (V R  TIP)  312 , an RV coil input terminal  314  and an SVC coil input terminal  316 . A case input terminal  318  may be coupled with the housing  300  of the IMD  100 . The input terminals  302 - 318  may be electrically coupled with the electrodes  112 - 128  (shown in  FIG. 1 ). 
         [0050]    The IMD  100  includes a programmable microcontroller  320 , which controls the operation of the IMD  100 . The microcontroller  320  (also referred to herein as a processor, processor module, or unit) typically includes a microprocessor, or equivalent control circuitry, and may be specifically designed for controlling the delivery of stimulation therapy and may further include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry. The microcontroller  320  may include one or more modules and processors configured to perform one or more of the operations described above in connection with the method  144 ,  250 , and  300 . An autocapture module  322  senses evoked responses of the heart  102  (shown in  FIG. 1 ) in response to delivery of stimulus pulses to the heart  102  when the IMD  100  operates in the autocapture mode described above. An autothreshold module  324  performs threshold searches when the IMD  100  operates in the autothreshold mode. For example, the autothreshold module  324  may incrementally decrease the electrical potential of stimulus pulses delivered to myocardium of the heart  102  (shown in  FIG. 1 ) until a loss of capture is detected in a first predetermined number of consecutive cardiac cycles. The autothreshold module  324  then may incrementally increase the electrical potential of the stimulus pulses until capture is detected in a second predetermined number of consecutive cardiac cycles. 
         [0051]    A fusion detection module  326  identifies fusion-based behavior in myocardium of the heart  102  (shown in  FIG. 1 ). The fusion detection module  326  determines whether fusion occurs during a cardiac cycle. For example, the fusion detection module  326  may examine the position and/or shape of cardiac signal waveforms to identify fusion in a cardiac cycle, as described above. The fusion detection module  326  maintains the fusion beat count and the total beat count over predetermined intervals. 
         [0052]    A control module  328  automatically switches the IMD  100  between the autothreshold and autocapture modes based on the presence of fusion-based behavior detected by the fusion detection module  326 . For example, the control module  328  may switch the IMD  100  from the autocapture mode to the autothreshold mode when an amount of fusion-based behavior exceeds one or more fusion thresholds. In another example, the control module  328  switches the IMD  100  from the autothreshold mode to the autocapture mode when an amount of fusion-based behavior falls below one or more fusion thresholds. The control module  328  may base the decision whether to switch from one mode to the other on a number of cardiac cycles exhibiting fusion-based behavior, as described above. 
         [0053]    An activator control module  378  is configured to control interfacing of the IMD  100  with the NPA device  144 . The module  378  automatically switches between the IMD  100  patient related settings and procedure related settings based on a command received from the external NPA device  144 . For example, the activator control module  378  may switch the IMD  100  from the patient related settings to the procedure related settings when the IMD  100  receives the safe mode command. The activator control module  378  may perform system check when the IMD  100  receives a status check command from the NPA device  144 . For example, a user by pressing the status button on NPA device  144  sends a command to the IMD  100  to check lead impedance and also check the current settings of the IMD&#39;s  100  loaded in the active parameter fields. The activation control module processes the command, checks the system status, and transmits a signal back to the NPA device  144  via the telemetry circuit  364 . 
         [0054]    The microprocessor  320  receives signals from the electrodes  112 - 128  (shown in  FIG. 1 ) via an analog-to-digital (A/D) data acquisition system  346 . The cardiac signals are sensed by the electrodes  112 - 128  and communicated to the data acquisition system  346 . The cardiac signals are communicated through the input terminals  302 - 316  to an electronically configured switch bank, or switch,  348  before being received by the data acquisition system  346 . The data acquisition system  346  converts the raw analog data of the signals obtained by the electrodes  120 - 138  into digital signals  350  and communicates the signals  350  to the microcontroller  320 . A control signal  348  from the microcontroller  320  determines when the data acquisition system  346  acquires signals, stores the signals  350  in the memory  524 , or transmits data and or signal to the NPA device  144 . 
         [0055]    The switch  348  includes a plurality of switches for connecting the desired electrodes  112 - 128  (shown in  FIG. 1 ) and input terminals  302 - 318  to the appropriate I/O circuits. The switch  348  closes and opens switches to provide electrically conductive paths between the circuitry of the IMD  100  and the input terminals  302 - 318  in response to a control signal  352 . An atrial sensing circuit  354  and a ventricular sensing circuit  356  may be selectively coupled to the leads  104 - 108  (shown in  FIG. 1 ) of the IMD  100  through the switch  348  for detecting the presence of cardiac activity in the chambers of the heart  102  (shown in  FIG. 1 ). The sensing circuits  354 ,  356  may sense the cardiac signals that are analyzed by the microcontroller  320 . Control signals  358 ,  360  from the microcontroller  320  direct output of the sensing circuits  354 ,  356  that are connected to the microcontroller  320 . An impedance measuring circuit  330  is enabled by the microcontroller  320  via a control signal  332 . The impedance measuring circuit  330  may be electrically coupled to the switch  348  so that an impedance vector between any desired pairs of electrodes  120 - 138  may be obtained. The IMD  100  additionally includes a battery  370  that provides operating power to the circuits shown within the housing  300 , including the microcontroller  320 . The IMD  100  includes a physiologic sensor  372  that may be used to adjust pacing stimulation rate according to the exercise state of the patient. 
         [0056]    The clock  334  may measure time relative to the cardiac cycles or cardiac signal waveforms of the heart  102  (shown in  FIG. 1 ). The clock  334  measures elapsed amounts of time based on start and stop control signals  336  from the microcontroller  320  to determine the ventricular and atrial heart rates. Additionally, the clock  334  may track the amount of time elapsed between threshold searches. The elapsed time may be compared to a predetermined time period to determine whether to perform another threshold search, as described above. 
         [0057]    The memory  324  may be embodied in a computer-readable storage medium such as a ROM, RAM, flash memory, or other type of memory. The microcontroller  320  is coupled to the memory  324  by a suitable data/address bus  362 . The memory  324  may store programmable operating parameters and thresholds used by the microcontroller  320 , as required. For example the stored programmable operating parameters and thresholds may be used to customize the operation of the IMD  100  to suit the needs of a particular patient. For example, the memory  324  may store the safe mode parameters used to switch the active parameters of the IMD  100  prior to a medical procedure. In another example, the memory  324  may store data indicative of cardiac signal waveforms, the fusion thresholds, predetermined time periods, fusion beat counts, total beat counts, and the like. 
         [0058]    The safe mode parameters of the IMD  100  may be non-invasively programmed into the memory  324  through a telemetry circuit  364  in communication with the NPA device  144 , such as a trans-telephonic transceiver or a diagnostic system analyzer. For example, the external device that telemetry circuit communicates with may be a NPA device  144 . The telemetry circuit  364  is activated by the microcontroller  320  by a control signal  366 . The telemetry circuit  364  allows intra-cardiac electrograms, cardiac waveforms of interest, detection thresholds, status information relating to the operation of IMD  100 , and the like, to be sent to the NPA device  144  through an established communication link  368 . 
         [0059]      FIG. 4(   a ) is a flow chart illustrating a process to switch an IMD into a procedure safe mode in accordance with an embodiment. The process  400  starts with a determination of which medical procedures or types of procedures the IMD  100  is to be configured  402 . The determination of the procedure or procedure type includes determining one or more groups of settings for the parameters of the IMD  100 . For example, the settings may include disabling sensing (e.g., DOO, pacing OFF), fixing the pacing rate at a predetermined rate (e.g., 80 bpm) and the like. The settings may include enabling atrial sensing and disabling ventricular sensing or vice versa, based on the medical procedure associated with the settings. At  404 , the groups of settings associated with the medical procedure are loaded into a section  382  of a long-term memory  324  in the IMD  100  that is designated to store medical procedure related settings. Optionally, multiple groups of settings may be loaded in connection with multiple different medical procedures. For example, one group of settings may be loaded in connection with MRI procedures using up to 2 Tesla MRI scanners, while a second group of settings may be loaded in connection with MRI procedures using over 2 Tesla scanners. Third, fourth and/or fifth groups of settings may be loaded for surgical procedures, clinical examinations or emergency room situations, respectively. The medical procedure related settings are programmed for one or multiple medical procedures well in advance of the medical procedure. For example, the settings may be loaded at the time of the implant of an IMD  100  or by the manufacturer at the time of manufacture of an IMD  100 . 
         [0060]    At  408 , prior to the initiation of a medical procedure, a user utilizes the NPA device  144  to instruct the IMD  100  to switch the active parameter fields from patient related settings to a procedure safe mode. For example, the user may be a technician or a nurse practitioner. The user interface  212  provides a means of input, allowing the users to manipulate the NPA device  144 . For example, the user interface  212  includes a safe mode ON button  140 , which sends the IMD  100  command to switch the IMD&#39;s  100  active parameter fields from patient related settings to procedure related settings. 
         [0061]    At  410 , the NPA device  144  performs a system self check to verify if the NPA device  144  was enabled for the medical procedure. For example, the NPA device  144  may test if the NPA device  144  is wirelessly coupled to the IMD  100 . Optionally, the NPA device  144  may refer to a medical procedure enablement checklist, to confirm if the NPA device  144  is enabled for the medical procedure. For example, the check list may be part of a database, accessible by the NPA device  144  via the connectivity  210  module. The NPA device  144  may look up the database to check if the medical procedure has been authorized by the clinic and the like. If the NPA device  144  is not enabled, the flow moves to  412 . The process stops at  412  and the NPA device  144  ends communication. Optionally, the NPA device  144  may notify the user that the NPA device  144  is not enabled. 
         [0062]    Returning to  410 , if the NPA device  144  is enabled, the flow moves to  414 . At  414 , the NPA device  144  sends the command to switch the IMD  100  to procedure related settings. The NPA device  144  sends the signal via a telemetry circuit  414 . Although telemetry commonly refers to wireless communication mechanisms, the telemetry also encompasses data transferred over other media, such as a telephone or computer network, optical link or other wired communications. Optionally, the telemetry system may use a GSM network by using SMS to receive and transmit telemetry communications. The IMD  100  receives the command to switch the active parameter fields to procedure related settings at  416  and the flow moves to  418 . 
         [0063]    In an alternate embodiment, the NPA device  144  may have a safety feature requiring the user to confirm if the IMD  100  should switch active parameter fields. For example, the NPA device  144  may request the user to press the safe mode ON button  140  a second time, as a confirmation step, to switch the active parameter fields to the procedure related settings. 
         [0064]    At  413 , the IMD  100  analyzes the received signal to determine whether the received signal is valid. For example, a header or data in the received signal may be analyzed to confirm that the received signal was transmitted from an authorized NPA device  144 . The content of the received signal may be analyzed to confirm that the content corresponds to an instruction that the IMD  100  is capable of performing. 
         [0065]    At  413 , the IMD  100  also determines whether the IMD  100  is “enabled” to carry out NPA instructions in the received signal. For example, an external IMD programmer may be used separately to disable or enable NPA mode control of the IMD  100  by the NPA device  144 . An IMD-trained physician or programmer may determine that it is not desirable for a particular patient&#39;s IMD  100  to be switchable to a procedure safe mode by an MR technician through the NPA device  144 . Instead, the IMD-trained physician or programmer may want an IMD-trained person to be present when the IMD  100  is switched to the procedure safe mode. Hence, the IMD-trained physician or programmer disables an NPA enabled flag such as through an IMD programmer device. At  413 , if the NPA enabled flag is set, the IMD  100  is enabled to switch modes in response to instructions from the NPA device  144  and flow moves to  418 . If the NPA enabled flag is not set, the IMD  100  is not permitted to switch modes in response to instructions from the NPA device  144 , and flow moves to  415 . 
         [0066]    At  415 , an invalid signal flag and/or an NPA disabled flag is set. The invalid signal flag is set when the received signal is invalid as explained above. The NPA disabled flag is set when the IMD  100  determines at  413  that the NPA enabled flag is not set. Next, flow moves to  426 , where the invalid signal flag or NPA disabled flag is transmitted back to the NPA device  144  to inform the user. 
         [0067]    At  418 , the IMD  100  performs one or more tests to check the state of the IMD  100  relative to predetermined device state criteria. For example, the device state check of the IMD  100  may perform a lead impedance test to verify if the lead impedance is within a predetermined range. Optionally, the device state test of the IMD  100  may test the sensing circuit or perform other diagnostics on the IMD  100 . The lead impedance predetermined range may be set by the IMD&#39;s  100  manufacturer. Alternatively, the predetermined range may be prescribed by a clinician. Each lead is typically electrically isolated from other leads and is encased within an outer sheath that electrically insulates the lead conductors from body tissue and fluids. Cardiac leads are continuously flexed by the beating of the heart. Stress can also be applied to a lead body by patient movement, during implantation, during lead repositioning, or during IMD  100  changeout. Such stresses may lead to fracture of one or more conductors of the lead. Additionally, the electrical connection between the IMD  100  and the lead can be intermittently or continuously disrupted, which may result in intermittent or continuous changes in lead impedance. 
         [0068]    The lead impedance test is one type of lead integrity test that may be performed by the IMD  100  at  418 . Electrical lead integrity may be assessed soon after the IMD  100  receives the signal from the NPA device  144 . If the lead impedance is uncharacteristically high, a lead fracture may be indicated. Detecting lead fractures is desirable because lead fractures may prevent delivery of effective therapeutic shocks to cardiac tissue. Alternatively, if the lead impedance is uncharacteristically low, this may indicate a breach in lead insulation. 
         [0069]    Optionally, other types of device state checks may be performed on the IMD  100  and compared to corresponding device state criteria. If the test of the device state does not satisfy predetermined device state criteria, flow moves to  420  where the IMD  100  raises a fail flag. The fail flag indicates that the device state did not satisfy the predetermined device state criteria. When more than one device test is performed, multiple separate flags may exist. One or more flags may be set at  420  depending upon which device state checks are performed and which device state checks satisfy or do not satisfy the corresponding predetermined device state criteria. Optionally, values associated with the device state test(s) may be stored at  420  separately, or in combination, with the flags. Flow moves to  426  and the IMD  100  sends the fail flag(s) and/or values associated with the tests, to the NPA device  144 . The process stops at  426  and the IMD  100  does not alter the active parameter fields if one or more device fail flags are raised. 
         [0070]    Returning to  418 , when the state of the IMD  100  is tested and determined to be within the predetermined device state criteria, flow moves to  421 . 
         [0071]    At  421 , the IMD  100  performs one or more tests to assess a state of the patient relative to predetermined patient state criteria. For example, the assessment of the patient state may include measurements of one or more physiologic variables, such as heart rate, a need for pacing, sensing, the patient&#39;s pacing threshold, patient diagnostics and the like. The IMD  100  compares the measurements with predetermined patient state criteria. The predetermined patient state criteria may be set at the time of manufacture or programmed by a physician at the time of implant or thereafter. At  421 , if it is determined that the patient state exceeds or falls below the one or more predetermined patient state criteria, then flow moves to  423 . 
         [0072]    At  423 , the IMD  100  raises or sets one or more flags based on which patient state tests are performed and on whether the corresponding predetermined patient state criteria are satisfied. For example, patient heart rate may be too high, but the pacing threshold may be acceptable. In this example, the heart rate flag would be set/raised and the pacing threshold flag would not be set/raised. Optionally, the IMD  100  may store, at  423 , the values measured at  421  (e.g., the heart rate, pacing threshold, etc.) 
         [0073]    After  423 , flow moves to  426  where the IMD  100  sends the flag(s) and/or measured value(s) to the NPA device  144 . 
         [0074]    Returning to  421 , if it is determined that the patient state satisfies each of the predetermined patient state criteria then flow moves to  422 . At  422 , the IMD  100  performs another system check to verify if the prescribed medical procedure related settings are loaded in the section  382  of the memory  324 . If the medical procedure related settings are not loaded, flow moves to  424  where the IMD  100  raises a non-procedures settings flag. At  426 , the IMD  100  communicates the raised non-procedure settings flag to the NPA device  144 . The process stops at  426  and the IMD  100  does not alter the active parameter fields if procedure related settings are not loaded. 
         [0075]    Returning to  422 , if the prescribed medical procedure settings are loaded in the memory  324 , flow moves to  428 . At  428 , the IMD  100  stores the patient related settings from the active parameter fields to a section  384  of the micro-controller memory  380 . Once patient related settings are saved in memory  380 , the IMD  100  loads the procedure related settings into the active parameter fields. Thereafter, the IMD  100  operates based on the procedure related settings until the IMD  100  receives a command to switch the settings back to the original patient related settings. 
         [0076]    Optionally, one or more of the checks performed at  418 ,  421  and  422  may be omitted entirely or the order changed. 
         [0077]    At  431 , a safe mode timer is started. As explained below in connection with  FIG. 4(   b ), IMD  100  will automatically revert back to the patient related settings after a predetermined period of time has passed. For example, the IMD  100  may have stored therein a safe mode time limit (e.g. 2 hours, 1 day, etc.). The IMD  100  will only remain in the procedure safe mode for the safe mode time limit which may be set at the time of manufacture or programmed at the time of implant or after implantation. 
         [0078]      FIG. 4(   b ) Illustrates a flow chart to switch an IMD  100  out of a procedure safe mode in accordance with an embodiment. The process of  FIG. 4(   b ) includes three parallel flow paths, namely  459  to  464 ,  452  to  464  and  451  to  464 . The flow along  452  to  464  concerns the process to end the procedure safe mode at the command of the NPA device  144 . The flow along  459  to  464  concerns the process to end the procedure safe mode in response to an alert from the remote monitoring system. The flow along  451  to  464  concerns the process to automatically end the procedure safe mode after a predetermined period of time. 
         [0079]    At  451 , the IMD  100  updates the safe mode timer after a set increment of time (e.g., 1 minute, 1 hour, etc.). At  453 , the present value of the safe mode timer is compared to a safe mode time limit. If the current value of the safe mode timer does not exceed the safe mode time limit, the flow returns along  455  to  451 , where the current value of the safe mode timer is incremented. At  453 , when the safe mode timer exceeds the safe mode time limit, flow moves along  457  to  462  which is discussed below. 
         [0080]    The flow along  452 - 462  concerns when a user utilizes the NPA device  144  to communicate a procedure complete command  452  to the IMD  100 . For example, the user sends the procedure complete command  452  at the completion of a medical procedure. Alternatively, the user may send a procedure complete command prior to completion of a medical procedure. 
         [0081]    At  454 , the NPA device  144  transmits a command to the IMD  100 , via the telemetry circuit  216 , to switch out of safe mode. For example, the NPA device  144  may communicate procedure complete command  142  to the IMD  100  via the telemetry circuit  216 . 
         [0082]    At  456 , the IMD  100  receives the procedure complete command from the NPA device  144 . At  458 , upon receiving the procedure complete command, the IMD  100  checks for the validity of the signal. The activator control module  378 , which is configured to control interfacing of the IMD  100  with the NPA device  144 , performs the check based on the instructions from the program microcontroller  320 . For example, the user may mistakenly command to switch to procedure related settings when the IMD  100  is already in the safe mode. If the signal received at  456  is something other than the procedure complete command and the IMD  100  currently has procedure related settings loaded, the IMD  100  will send a communication back to the NPA device  144  indicating that the signal sent does not correspond to the correct next workflow step that the IMD  100  expects. When the received signal is not valid, the process stops at  460  and the IMD  100  does not alter the active parameter fields. 
         [0083]    Returning to  458 , if the signal received is a procedure complete command, the activator control module  378 , commands the IMD  100  to perform a patient and device state check at  462 . For example, the device and patient state checks may be similar to those discussed above in connection with  FIG. 4(   a ) at  418 ,  420 ,  421  and  423 . For example, the device state check may assess the lead impedance, and the like, while the patient state check may assess the pacing threshold, heart rate, diagnostics, and the like. If the device and/or patient state does not satisfy the assessment at  462 , flow moves to  463  where a corresponding flag is set. Optionally, at  463 , one or more values may be stored in connection with the checks performed at  462 . 
         [0084]    At  460 , the flag(s) and/or measured value(s) are transmitted to the NPA device  144 , along with a communication indicating that one or both of the device and patient state checks failed, and that the IMD  100  will remain in its current procedure safe mode. The process stops at  460  and the IMD  100  does not alter the active parameter fields. 
         [0085]    Optionally, the check at  462  may be omitted entirely. Alternatively, the check at  462  may check only the device state or only the patient state, not both. 
         [0086]    Returning to  462 , if the device and patient state checks are passed, at  464  the activator control module  378  automatically switches the IMD  100  from the procedure related settings back to the patient related settings. For example, the IMD  100  loads the stored original patient related settings back into the active parameter fields from the microcontroller memory  380 . Alternatively, the IMD  100  may load the stored original patient related settings into the active parameter fields from long term memory  362 . 
         [0087]    In an alternate embodiment, the IMD  100  may have a safety feature requiring the user to confirm if the IMD  100  should switch active parameter fields. For example, the IMD  100  may want the user to press the safe mode OFF button  138  a second time, as a confirmation step, to switch the IMD&#39;s  100  active parameter fields from procedure related setting back to the patient related settings stored in the IMD  100  memory  380 . 
         [0088]    At  459 , the IMD  100  receives an alert communication, such as from a remote monitoring system (e.g., the Merlin.net patient care network or the Merlin@Home transmitter offered by S.J. Medical, Inc.). The alert command is verified at  458 . When the alert command is verified, flow moves to  462 , otherwise flow moves to  460  as discussed above. 
         [0089]      FIG. 5  illustrates a flow chart for a process to query IMD  100  status, using the NPA device  144 , to switch an IMD  100  into a procedure safe mode in accordance with an embodiment.  FIG. 5  describes the process for interrogating the IMD  100  using the NPA device  144  for the current state of the IMD  100 , and presents the IMD  100  status information on the NPA device  144  to the user. The process  500  starts at  502  whereby a user requests the status of the IMD  100  using the NPA device  144 . For example, the user may press a check status button  134  on the NPA device  144 . Alternatively, the NPA device  144  may use audio signal as an input from the user, via the user interface  212 . Alternatively, the user may input a request using a touch screen user interface  212 . In another embodiment, the user may input a request using a hybrid of buttons, touch screen, and or audio control user interface  212 . 
         [0090]    The flow moves to  504  where the NPA device  144  communicates the system status request to the IMD  100  via the telemetry circuit  216 . At  506  the IMD  100  receives a status check request from the NPA device  144 . Upon receiving the status checks signal, at  508 , the IMD  100  determines if the lead impedance is within a predetermined range. An impedance measuring circuit  330  is enabled by the activator control module  378  via a control signal  332 . The impedance measuring circuit  330  may be electrically coupled to the switch  348  so that an impedance vector between any desired pairs of electrodes  120 - 138  may be obtained. The lead impedance range can be a predetermined range defined by the IMD&#39;s  100  manufacturer or a predetermined range prescribed by a clinician. 
         [0091]    If the lead impedance is not within the predetermined range, flow moves to  510 . At  510  the IMD  100  raises a lead impedance fail flag. Once the lead impedance fail flag is raised, flow moves to  516  and the IMD  100  sends the fail flag to the NPA device  144 . The process stops at  518 , where the NPA device  144  notifies user the status of the IMD  100 . For example, the user interface  212  may include an indicator  214  that may communicate the status of the IMD  100  to user. 
         [0092]    Returning to  508 , when the IMD  100  lead impedance is within the predetermined range, flow moves to  512  and the IMD  100  performs another system check to verify if the prescribed medical procedure related settings are loaded in memory  324 . If the medical procedure related settings are not loaded, flow moves to  514  where the IMD  100  raises a non-procedures settings flag. At  516 , the IMD  100  communicates the raised non-procedure settings flag to the NPA device  144  via the telemetry circuit  364 . The process stops at  518 , where the NPA device  144  notifies user the status of the IMD  100 . For example, the user interface  212  of the NPA device  144  may include an indicator  214  that may communicate the status of signal sent or received from the IMD  100  to the user. The indicator, in one embodiment, may be green  138  and a red  132  light emitting diode (LED). Where the green  138  light may indicate that the communication between the NPA device  144  and the IMD  100  was successful. 
         [0093]    Returning to  512 , if the prescribed medical procedure settings are loaded in the IMD  100  memory  324 , flow moves to  516  where the IMD  100  sends the status signal to the NPA device  144  via the telemetry circuit  364 . The status signal is used by the NPA device  144 , to notify the user, that the IMD  100  passed system check test. 
         [0094]      FIG. 6  illustrates a functional block diagram of the external device  552 , such as a programmer, that is operated to interface with the IMD  100  (shown in  FIG. 1 ). The external device  552  includes an internal bus  600  that connects/interfaces with a Central Processing Unit (CPU)  602 , ROM  604 , RAM  606 , a hard drive  608 , the speaker  610 , a printer  612 , a CD-ROM drive  614 , a floppy drive  616 , a parallel I/O circuit  618 , a serial I/O circuit  620 , the display  622 , a touch screen  624 , a standard keyboard connection  626 , custom keys  628 , and a telemetry subsystem  630 . The internal bus  600  is an address/data bus that transfers information between the various components described herein. The hard drive  608  may store operational programs as well as data, such as waveform templates and detection thresholds. 
         [0095]    The CPU  602  typically includes a microprocessor, a micro-controller, or equivalent control circuitry, is configured to control interfacing of the IMD  100  with the external device  552  and with the IMD  100  (shown in  FIG. 1 ). The CPU  602  may include RAM or ROM memory, logic and timing circuitry, state machine circuitry, and I/O circuitry to interface with the IMD  100 . The display  622  (e.g., may be connected to the video display  632 ) with a touch screen  624  provides graphic information relating to the IMD  100 . The touch screen  624  accepts a user&#39;s touch input  634  when selections are made. The keyboard  626  (e.g., a typewriter keyboard  636 ) allows the user to enter data to the displayed fields, as well as interface with the telemetry subsystem  630 . Furthermore, custom keys  628  turn on/off  638  (e.g., EWI) the external device  552 . The printer  512  prints copies of reports  640  for a physician to review or to be placed in a patient file, and speaker  610  provides an audible warning (e.g., sounds and tones  642 ) to the user. The parallel I/O circuit  618  interfaces with a parallel port  644 . The serial I/O circuit  620  interfaces with a serial port  646 . The floppy drive  616  accepts diskettes  648 . Optionally, the floppy drive  616  may include a USB port or other interface capable of communicating with a USB device such as a memory stick. The CD-ROM drive  614  accepts CD ROMs  650 . 
         [0096]    The telemetry subsystem  630  includes a central processing unit (CPU)  652  in electrical communication with a telemetry circuit  654 , which communicates with both an ECG circuit  656  and an analog out circuit  658 . The ECG circuit  656  is connected to ECG leads  660 . The telemetry circuit  654  is connected to a telemetry wand  662 . The analog out circuit  658  includes communication circuits to communicate with analog outputs  664 . The external device  552  may wirelessly communicate with the IMD  100  and utilize protocols, such as Bluetooth, GSM, infrared wireless LANs, HIPERLAN, 3G, satellite, as well as circuit and packet data protocols, and the like. Alternatively, a hard-wired connection may be used to connect the external device  552  to the IMD  100  (shown in  FIG. 1 ). 
         [0097]      FIG. 7  illustrates an embodiment for an NPA device  700  that can be used with multiple different medical procedures. The variation in types of diagnostic imaging or medical procedures that can affect the IMD  100  and the possibility of having multiple IMD&#39;s  100  in a patient is encompassed in  FIG. 7 . Therefore, the IMD  100  may have one or more groups of settings loaded in the memory  324  of the IMD  100 . 
         [0098]    In one embodiment, the settings may include disabling sensing. For example, the NPA device  700  may command the IMD  100  to stop processing the electrical manifestation of naturally occurring heart beats as sensed by the heart electrodes. Furthermore, the NPA device  700  may command the IMD  100  to switch to a fixed pacing rate. The fixed pacing rate may be a predetermined rate (e.g., 80 bpm) and the like. The settings may include enabling atrial sensing and disabling ventricular sensing or vice versa, based on the medical procedure associated with the settings. For example, the settings may include parameters like single or dual chamber pacing, single chamber sensing or double chamber sensing or no sensing, or disabling rate response or single site pacing or multisite pacing (e.g., DOO, pacing OFF), and the like. 
         [0099]    In one embodiment, the buttons  702 , 704 , 706 , 708 ,  710  on the NPA device  700  may be used to switch the IMD&#39;s  100  active parameter fields for different configuration of a diagnostic imaging. For example, the buttons  702 , 704 , 706 , 708 ,  710  may be used to switch the IMD&#39;s  100  settings for 0.7 Tesla, 1.0 Tesla, 1.2 Tesla, 1.5 Tesla, 3 Tesla MRI systems. Alternatively, the buttons  702 , 704 , 706 , 708 ,  710  on the NPA device  700  may be used to switch the IMD&#39;s  100  active parameter fields for a particular anatomy. For example, the buttons  702 , 704 , 706 , 708 ,  710  may be used to switch procedure related settings for pacemakers, cardioverters, defibrillators, implantable cardioverter defibrillators, implantable heart monitors respectively. Optionally, the NPA device  700  may be used to switch the settings of multiple IMD&#39;s manufactured by a vendor. 
         [0100]    Optionally, the NPA device  700  may be personalized to a patient, whereby the NPA device  700  switches active parameter fields for the IMD&#39;s  100  in a particular patient. For example, if a patient has multiple IMD&#39;s  100  each button  702 , 704 , 706 , 708 ,  710  may be configured to switch the settings for a particular IMD  100 . For example, the buttons  702 , 704 , 706 , 708 ,  710  may be used to switch procedure related settings for a pacemaker, pain suppression devices, implantable heart monitors, implantable drug pumps and neurological stimulators. Alternatively, the NPA device  700  may be personalized to a patient, whereby the NPA device  700  switches active parameter fields for different medical procedures that such patient may undergo. 
         [0101]      FIG. 8  illustrates a distributed processing system  800  in accordance with one embodiment. The distributed processing system  800  includes a server  802  connected to a database  804 , a programmer  806  (e.g., similar to external device  552  (shown in FIG.  5 )), a local RF transceiver  808 , a NPA device  144  and a user workstation  810  electrically connected to a communication system  812 . The communication system  812  may be the internet, a voice over IP (VoIP) gateway, a local plain old telephone service (POTS) such as a public switched telephone network (PSTN), a cellular phone based network, and the like. Alternatively, the communication system  812  may be a local area network (LAN), a campus area network (CAN), a metropolitan area network (MAN), or a wide area network (WAM). The communication system  812  serves to provide a network that facilitates the transfer/receipt of information such as cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, IMD  100  programming data, safe mode signal to the IMD  100 , and the like. 
         [0102]    The server  802  is a computer system that provides services to other computing systems over a computer network. The server  802  controls the communication of information such as cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, and the like. The server  802  interfaces with the communication system  812  to transfer information between the programmer  806 , the local RF transceiver  808 , the NPA device  144 , the user workstation  810  as well as a cell phone  814  and a personal data assistant (PDA)  816  to the database  804  for storage/retrieval of records of information. On the other hand, the server  802  may upload a command to switch to procedure related settings from a NPA device  144  via the local RF transceiver  808  to an IMD  100 . 
         [0103]    The database  804  stores information such as cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, IMD  100  programming data, safe mode signal to the IMD  100 , and the like, for a single or multiple patients. The information is downloaded into the database  804  via the server  802  or, alternatively, the information is uploaded to the server from the database  804 . The programmer  806  is similar to the external device  552  and may reside in a patient&#39;s home, a hospital, or a physician&#39;s office. The programmer  806  interfaces with the surface ECG unit  822  and the IMD  100 . The programmer  806  may wirelessly communicate with the IMD  100  and utilize protocols, such as Bluetooth, GSM, infrared wireless LANs, HIPERLAN, 3G, satellite, as well as circuit and packet data protocols, and the like. Alternatively, a hard-wired connection may be used to connect the programmer  806  to the IMD  100 . The programmer  806  is able to acquire cardiac signals from the surface of a person (e.g., ECGs), intra-cardiac electrogram (e.g., IEGM) signals from the IMD  100 , and/or cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, and the like, from the IMD  100 . The programmer  806  interfaces with the communication system  812 , either via the internet or via POTS, to upload the information acquired from the surface ECG unit  820  or the IMD  100  to the server  802 . 
         [0104]    The local RF transceiver  808  interfaces with the communication system  812  to upload one or more of cardiac signal waveforms, ventricular and atrial heart rates, and detection thresholds  246  (shown in  FIG. 2 ) to the server  802 . In one embodiment, the surface ECG unit  820  and the IMD  100  have a bi-directional connection  824  with the local RF transceiver  808  via a wireless connection. The local RF transceiver  808  is able to acquire cardiac signals from the surface of a person, intra-cardiac electrogram signals from the IMD  100 , and/or cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, and the like, from the IMD  100 . On the other hand, the local RF transceiver  808  may download stored cardiac signal waveforms, fusion-thresholds, fusion beat counts, total beat counts, and the like, from the database  804  to the surface ECG unit  820  or the IMD  100 . 
         [0105]    The user workstation  810  may interface with the communication system  812  via the Internet or POTS to download cardiac signal waveforms, fusion thresholds, fusion beat counts, total beat counts, NPA unit log and the like via the server  802  from the database  804 . Alternatively, the user workstation  810  may download raw data from the IMD  100  via either the programmer  806  or the local RF transceiver  808 . The user workstation  810  may download the information and notifications to the cell phone  814 , the PDA  816 , the local RF transceiver  808 , the programmer  806 , or to the server  802  to be stored on the database  804 . For example, the user workstation  810  may communicate to the activation device  144  via a wireless communication link  826  to send the safe mode ON or procedure complete command to the IMD  100 . 
         [0106]    The NPA device  144  may communicate with the IMD  100  remotely via a local RF transceiver, local area network or wireless. Alternatively, the NPA device  144  may send IMD  100  status directly to a cell phone  814 , PDA  816  or a workstation  810 . Alternatively, the NPA device  144  may send IMD  100  status to a cell phone  814 , PDA  816  or a workstation  810  via the server  802  from the database  804 . Alternatively, the NPA device  144  may communicate with the programmer device to program procedure related settings if the NPA device  144  detected procedure related settings not loaded in IMD  100  memory. 
         [0107]    It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments of the invention without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments of the invention, the embodiments are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. 
         [0108]    The written description uses examples to disclose the various embodiments of the invention, including the best mode, and also to enable any person skilled in the art to practice the various embodiments of the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or if the examples include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
         [0109]    It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions, types of materials and coatings described herein are intended to define the parameters of the invention, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means—plus-function format and are not intended to be interpreted based on 35 U.S.C. §112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.