Abstract:
A medical device system having an improved interface and method of operation that more efficiently facilitates interaction with a user. In one aspect the medical device system and method graphically displays a hierarchy of input mechanism that each correspond to a set of arrhythmic episodes having a common data characteristic, such as zone of detection of arrhythmia type. By selecting one of the input mechanisms, the user is able to quickly view detailed information of the set of arrhythmic episodes. Among other features, the medical device system also displays cardiac events in a histogram format such that the histogram has an axis representing a range of heart beat rates. According to the invention, the system scales the histogram as a function of all of the stored event in a normal view and scales the histogram as a function of a subset of the events in a magnification view, thereby allowing the user to better see the events along a portion of the histogram.

Description:
TECHNICAL FIELD 
     The present invention relates generally to medical devices and in particular to a an improved display interface and method of operation for a medical device system that more efficiently facilitates interaction with a user. 
     BACKGROUND OF INVENTION 
     Implantable cardiac defibrillators (ICDs) are well established therapeutic devices for treating patients who have experienced one or more documented episodes of hemodynamically significant ventricular tachycardia or ventricular fibrillation. Since their clinical inception more than two decades ago, ICDs have evolved from basic to sophisticated electronic devices that provide physicians with a variety of clinically useful functions with which to treat patients. 
     Presently, even the most basic of ICDs typically has more than one tachycardia detection criterion, tiered therapy which combines bradycardia support pacing with various antitachycardia pacing modes, low-energy cardioversion, defibrillation, and data logging capabilities. The data logging capabilities within ICDs have become increasingly important, since the amount of data required for the ICDs operation increases proportionally with the increase in ICD functions. Efficiently processing this large amount of data has become possible with the incorporation of microprocessors and memory within the ICD. 
     Even with the advances in ICD data logging and processing capabilities, arrhythmia event recording capabilities have been limited, making it difficult to verify the adequacy and efficacy of arrhythmia detection and therapy settings. Furthermore, ICDs have been designed to record electrocardiogram and diagnostic channel data which can indicate to the physician the ICDs behavior during multiple tachyarrhythmic episodes. These ICDs also include arrhythmic event counters which log the number of episodes detected and the success or failure of each programmed therapy. Moreover, monitoring capability in some ICDs allow for recording of electrocardiogram waveforms, which can assist the physician in assessing the efficacy of the implanted ICD. 
     Once an ICD has been implanted, the physician interacts with the ICD through a clinical programmer. The clinical programmer is used to establish a telemetric link with the implanted ICD. The telemetric link allows for instructions to be sent to the electronic circuitry of the ICD and clinical data regarding the occurrence and treatment of a patient&#39;s cardiac arrhythmias and the ICD&#39;s operation to be sent from the electronic circuitry of the ICD to the clinical programmer. The typical programmer is a microprocessor-based unit that has a wand for creating the telemetric link between the implanted ICD and the programmer, and a graphics display screen that presents a patient&#39;s recorded cardiac data and ICD system information to the physician. 
     As the amount of cardiac data recorded by ICDs increases with each new generation of ICD, manufacturers and clinicians alike are becoming more sensitive to the role that time-efficient programming and data interpretation plays in the physician&#39;s clinical visit with the patient. As ICDs become increasingly complex, the interpretation of recorded arrhythmic episodes and the programming of the ICD can be challenging and time-consuming tasks for some users. 
     Therefore, a need exists for improved ICD and programmer technology that facilitates the identification of relevant information regarding the patient&#39;s clinical status. There is a need in the art for a system that helps the user quickly and efficiently interact with the ICD and programmer including programming the IDC, viewing cardiac data and assessing the patient&#39;s current status. 
     SUMMARY OF THE INVENTION 
     The present disclosure describes a medical device system having an improved interface and method of operation that more efficiently facilitates the interaction with a user. In one embodiment, the invention is directed toward a medical device system and method of storing cardiac data indicative of a plurality of arrhythmic episodes, displaying a plurality of user input mechanisms in a graphical, hierarchical arrangement on a display screen of a medical device programmer unit such that each input mechanism corresponds to subset of the episodes having a common data characteristic. When one of the input mechanisms is selected by a user, detailed information regarding the corresponding subset of the arrhythmic episodes is displayed. The common data characteristic used catagorize the episodes can be, for example, a zone of detection for or a type of arrhythmic episode. 
     In another embodiment, the invention is directed toward a medical device system and method that displays cardiac events in a histogram format on a display screen of a medical device programmer unit such that an axis of the histogram represents a range of rates. When a user selects a normal view the system scales the histogram as a function of all of the stored events. When the user selects a magnification view the system scales the histogram as a function of a subset of the events that are graphically depicted along a portion of the histogram rate axis. The portion of the histogram can be defined by an atrial tachyarrhythmia response (ATR) trigger rate or can correspond to one or more zones of detection. 
     In another embodiment, the invention is directed toward a medical device system and method that displays cardiac data on a display of a medical device programmer unit using a plurality of screens including a device activity screen that primarily presents information regarding a status of a patient. According to the invention, the medical device system defaults into displaying the device activity screen when the programmer is operated by a user and the patient is experiencing an arrhythmia. 
     In yet another embodiment, the invention is directed toward a medical device system and method that displays a summary screen having a plurality of sections. The summary screen associates and displays a shortcut link with each section such that a corresponding portion of the cardiac data is displayed in a detailed format when a user selects one of the shortcut links. 
    
    
     BRIEF DESCRIPTION OF DRAWING 
     In the drawings, where like numerals describe like components throughout the several views: 
     FIG. 1 is an embodiment of an implantable cardiac defibrillator implanted into a heart of a patient, from which portions have been removed to show detail; 
     FIG. 2 is a block diagram of an implantable cardiac defibrillator according to one embodiment of the present invention; 
     FIG. 3 is a perspective view of an external programming unit, according to one embodiment of the present invention, which is used for communicating with the implantable cardiac defibrillator of FIG. 1; 
     FIG. 4 illustrates a display screen presenting one embodiment of a system summary window that displays essential information regarding the status of programer, including the patients condition, and which acts as a home page for a user; 
     FIG. 5 illustrates a display screen presenting one embodiment of a conversion summary window that presents a graphical summary of the episodes that have occurred; 
     FIG. 6A illustrates a display screen presenting one embodiment of a histogram window graphically depicting cardiac event information. 
     FIG. 6B illustrates a display screen presenting one embodiment of the histogram window of FIG. 6A where the user has elected to magnify a portion of the histogram; and 
     FIG. 7 illustrates a display screen presenting one embodiment of a device activity window that presents essential information regarding the patient. 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice and use the invention, and it is to be understood that other embodiments may be utilized and that electrical, programmatic, and structural changes may be made without departing from the spirit and 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. 
     The embodiments of the present invention illustrated herein are described as being included in an implantable cardiac defibrillator, which may include numerous pacing modes known in the art, and an external medical device programmer. However, the medical system and method of the present invention could also be implemented in an external cardioverter/monitor system as are known in the art. Also, the medical system and method of the present invention could also be implemented in an implantable atrial cardioverter-defibrillator, which may include numerous pacing modes known in the art. Furthermore, although the present invention is described in conjunction with an implantable defibrillator having a microprocessor based architecture, it will be understood that the implantable cardiac defibrillator (or other implanted device) may be implemented in any logic based, custom integrated circuit architecture, if desired. 
     Referring now to FIG. 1 of the drawings, there is shown one embodiment of a medical device system which includes an implantable cardiac defibrillator  20  electrically and physically coupled to at least one intracardiac catheter  22 . In one embodiment, the intracardiac catheter  22  includes one or more pacing electrodes and one or more intracardiac defibrillation electrodes. 
     The intracardiac catheter  22  is implanted in a human body  24  with portions of the intracardiac catheter  22  inserted into a heart  26  to detect and analyze electric cardiac signals produced by the heart  26  and to provide electrical energy to the heart  26  under certain predetermined conditions to treat cardia arrhythmias, including ventricular fibrillation, of the heart  26 . 
     In one embodiment, the intracardiac catheter  22  is an endocardial lead adapted to be releasably attached to the cardiac defibrillator  20 . The intracardiac catheter  22  has an elongate body with a proximal end  28  and a distal end  30  and is shown as having a pacing electrode  32  located at, or adjacent, the distal end  30  of the intracardiac catheter  22 . In one embodiment, the pacing electrode  32  is a tip electrode positioned at the distal end  30  of the intracardiac catheter  22 . Alternatively, the pacing electrode  32  is an annular, or a semi-annular ring electrode positioned adjacent the distal end  30 . 
     The intracardiac catheter  22  also includes one or more defibrillation electrodes. In one embodiment, the intracardiac catheter  22  has a first defibrillation electrode  34  and a second defibrillation electrode  36 , where the first defibrillation electrode  34  and the second defibrillation electrode  36  are defibrillation coil electrodes as are known in the art. The first defibrillation electrode  34  is spaced apart and proximal from the pacing electrode  32 , and the second defibrillation electrode  36  is spaced apart and proximal from the first defibrillation electrode  34  such that when the intracardiac catheter  22  is positioned within the heart  26  the pacing electrode  32  and the first defibrillation electrode  34  reside within a right ventricle  38  of the heart  26 , with the pacing electrode  32  in an apex location within the right ventricle  38 , and the second defibrillation electrode  36  is positioned within the right atrium chamber  40  of the heart  26  or a major vein leading to the right atrium chamber  40  of the heart  26 . 
     Referring now to FIG. 2, there is shown an embodiment of a block diagram of a cardiac defibrillator  20 . The cardiac defibrillator  20  includes electronic control circuitry  42  for receiving cardiac signals from a heart  26  and delivering electrical energy to the heart  26 . The electronic control circuitry  42  includes terminals, labeled with reference numbers  44 ,  46 , and  48  for connection to electrodes attached to the surface of the intracardiac catheter  22 . The pacing electrode  32  is electrically connected to terminal  44  and to the electronic control circuitry  42  through an electrically insulated conductor provided within the elongate body of the intracardiac catheter  22 . The first defibrillation electrode  34  and the second defibrillation electrode  36  are connected to terminals  46  and  48 , respectively, and to the electronic control circuitry  42  through electrically insulated conductors provided within the elongate body of the intracardiac catheter  22 . 
     In one embodiment, the electronic control circuitry  42  of the cardiac defibrillator  20  is encased and hermetically sealed in a housing  50  suitable for implanting in a human body. In one embodiment, titanium is used for the housing  50 , however, other biocompatible housing materials as are known in the art may be used. A connector block  52  is additionally attached to the housing  50  of the cardiac defibrillator  20  to allow for the physical and the electrical attachment of the intracardiac catheter  22  and the electrodes to the cardiac defibrillator  20  and the encased electronic control circuitry  42 . 
     The electronic control circuitry  42  of the cardiac defibrillator  20  is a programmable microprocessor-based system, with a microprocessor  54  and a memory circuit  56 , which contains parameters for various pacing and sensing modes and stores data indicative of cardiac signals received by the electronic control circuitry  42 . 
     A transmitter circuit  58  is additionally coupled to the electronic control circuitry  42  and the memory circuit  56  to allow the cardiac defibrillator  20  to communicate with a programmer unit  60 . In one embodiment, the transmitter circuit  58  and the programmer unit  60  use a wire loop antenna  62  and a radio frequency telemetric link, as is known in the art, to receive and transmit signals and data to and from the programmer unit  60  and the electronic control circuitry  42 . In this manner, programming commands or instructions are transferred to the microprocessor  54  of the cardiac defibrillator  20  after implant, and stored cardiac data pertaining to sensed arrhythmic episodes within the heart  26  and subsequent therapy, or therapies, applied to correct the sensed arrhythmic event are transferred to the programmer unit  60  from the cardiac defibrillator  20 . 
     The embodiment of the cardiac defibrillator block diagram shows the pacing electrode  32  coupled to a sense amplifier  64 . In an additional embodiment, the housing  50  of the cardiac defibrillator  20  is also coupled to the sense amplified  64  at  65  to allow for unipolar cardiac rate sensing between the pacing electrode  32  and the housing  50  of the cardiac defibrillator  20 . The output of the sense amplifier  64  is shown connected to an R-wave detector  66 . These components serve to sense and amplify the QRS waves of the heart, and apply signals indicative thereof to the microprocessor  54 . Among other things, microprocessor  54  responds to the R-wave detector  66  by providing pacing signals to a pace output circuit  68 , as needed according to the programmed pacing mode. Pace output circuit  68  provides output pacing signals to terminals  44  and  65 , which connect to the pacing electrode  32  and the housing  50  of the cardiac defibrillator  20 , for cardiac pacing. 
     The first defibrillation electrode  34  and the second defibrillation electrode  36  are coupled to a sense amplifier  70 , whose output is connected to a cardiac morphology detector  72 . These components serve to sense and amplify the QRS-waves of the cardiac cycle from the ventricular region of the heart  26 , and apply signals indicative thereof to the microprocessor  54 . In one embodiment, the cardiac morphology detector  72  includes an analog filter for filtering cardiac signal noise sensed by the electrodes. The cardiac signals are then bandlimited before arriving at an analog-to-digital filter. The cardiac signals are then A/D converted into a digital signal and subsequently received by the microprocessor  54 . In an alternative embodiment, the cardiac signals are filtered through an analog peak detector to extract the maximum and minimum cardiac signal values for each sensed cardiac interval. 
     The microprocessor  54  responds to the cardiac signals sensed within the heart  26  using the intracardiac catheter  22  by providing signals to cardioversion/defibrillation output circuitry  74  to provide either cardioversion or defibrillation electrical energy to the heart  26  depending upon nature of the arrhythmia sensed by the cardiac defibrillator  20 . Power to the cardiac defibrillator  20  is supplied by an electrochemical battery  76  that is housed within the cardiac defibrillator  20 . 
     For each arrhythmic episode sensed, cardiac defibrillator  20  stores episode data in memory circuit  56  as illustrated in Table 1. Other arrhythmic episode data can also be recorded and stored in the memory circuit  56 . 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 STORED DATA 
                 DESCRIPTION 
               
               
                   
               
             
             
               
                 Number 
                 Episode number stored in chronological order. 
               
               
                 Time stamp 
                 Date and time of the episode. 
               
               
                 Type 
                 The type of episode detected such as spontaneous, 
               
               
                   
                 induced, pacemaker-mediated tachycardia (PMT), 
               
               
                   
                 atrial tachyarrhythmia response (ATR), 
               
               
                   
                 sustained or magnet activated. 
               
               
                 Zone 
                 The zone of detection which can be (VF), (VT), VT-1, 
               
               
                   
                 Commanded, Accelerated. 
               
               
                 Rate 
                 The average rate of the episode in beats per minute. 
               
               
                 Therapy 
                 Therapy that was delivered to the patient prior to 
               
               
                   
                 detecting including: none, one ATP, more than one 
               
               
                   
                 ATP, one shock, more than one shock, ATP and 
               
               
                   
                 shock. 
               
               
                 Enhancement 
                 Any detection enhancement criteria. 
               
               
                 R-R Intervals 
                 The time intervals between consecutively sensed 
               
               
                   
                 R- waves for the episode. 
               
               
                 EGMs 
                 Data representing the sensed electrocardiogram 
               
               
                   
                 signal such as a ventricular signal and an atrial signal. 
               
               
                 Duration 
                 The duration of the episode. 
               
               
                   
               
             
          
         
       
     
     Referring now to FIG. 3, there is shown one embodiment of a medical device programmer  60  of the medical device system. As previously mentioned, one embodiment of programmer  60  for the implantable cardiac defibrillator  20  takes the form of an external controller as are known in the art. However, in an alternative embodiment, the medical device system is a completely external device such as an external cardioverting/defibrillator system as are known in the art, where the programmer unit is physically and electronically integrated into electronic control circuitry similar to the electronic control circuitry  42  of the cardiac defibrillator  20 . An example of this latter embodiment is for an external cardiac monitor and defibrillation unit, electrically connected to the heart by any combination of intracardiac catheters, epicardial electrodes and/or externally cardiac electrodes, all of which are known in the art. 
     FIG. 3 shows one embodiment of programmer  60  designed to be positioned external of the human body  24  for communicating with an implantable medical device, such as the cardiac defibrillator  20  from FIG. 1, via RF telemetry. Programmer  60  has programmer electronic circuitry, including a microprocessing unit and related circuitry, such as digital memory, which is coupled to a graphics display screen  102 . 
     In one embodiment, programmer  60  comprises an outer housing  100  which is made of a thermal plastic or other suitable lightweight durable material. The graphics display screen  102  is disposed on the upper surface of housing  100 . The graphics display screen  102  folds down into a closed position when programmer  60  is not in use, thereby reducing the size of programmer  60  and protecting the display surface of graphics display screen  102  during transportation and storage. 
     In an additional embodiment, the external programmer additionally has a floppy disk drive and a hard drive disposed within the housing. Air vents are provided at various points in the housing  100  so that an internal fan can circulate air within the housing  100  and prevent overheating of components therein. 
     Programmer  60  is shown with the graphics display screen  102  positioned in one of a plurality of possible open positions such that a display on the graphics display screen  102  is visible to a user situated in front of programmer  60 . In one embodiment, the graphics display screen  102  is of a liquid crystal display (LCD). The graphics display screen  102  is operatively coupled to the electronic circuitry disposed with the housing  100  and is adapted to provide a visual display of graphics and/or data under control of the programmer electronic circuitry. 
     Programmer  60  further includes a user input device coupled to the electronic circuitry. In one embodiment, the user input device is the graphics display screen  102 , which is provided with touch-sensitive capability, such that a user can interact with the programmer electronic circuitry by touching the display area on the graphics display screen  102  with a stylus  104 , or even the user&#39;s finger. In one embodiment, the touch-sensitive graphics display screen is primary input for programmer  60 . Programmer  60  further includes a programming head  106 , which is place over a patient&#39;s body near the implant site of an implanted device, such as the cardiac defibrillator  20 , in order to establish a telemetry link between the cardiac defibrillator  20  and programmer  60 . The telemetry link between the cardiac defibrillator  20  and programmer  60  allows the electronic circuitry coupled to the graphics display screen to be coupled to the electronic control circuitry of the cardiac defibrillator  20 . The programming head  106  is coupled to the electronic circuitry of programmer  60  and a receiver circuit for receiving signals from the transmitter circuit indicative of cardiac signals by a cable  108 . 
     The stylus  104  used to interact with the touch-sensitive graphics display screen  102  is coupled to the programmer electronic circuitry within the housing  100  by a cable  110 . Alternatively, programmer  60  may be equipped with a conventional computer “mouse”-type pointing device, rather than a stylus. In the absence of either a stylus or a mouse, on-screen cursor control for enabling user interaction with programmer  60  may be facilitated through cursor control keys  112  (arrow keys or the like) disposed on programmer  60 . 
     Programmer  60  further includes a receiver circuit for receiving signals from the transmitter circuit indicative of cardiac signals. Through the telemetric contact with the cardiac defibrillator  20 , programmer  60  is capable of capturing and storing recorded electrocardiogram data transmitted from the cardiac defibrillator  20  and displaying the electrocardiogram data on its graphics display screen  102 . 
     FIG. 4 illustrates display screen  102  presenting one embodiment of a system summary window  400  that displays all essential information regarding the status of programer  60  including the patient&#39;s condition. Upon initial interrogation, the programer  60  immediately defaults to the system summary window  400 . 
     In order to facilitate interaction with a user, system summary window  400  acts as a home page for the user. System summary page  400  comprises several sections that display the following information: an abbreviated listing of the programmed parameters, a clinical events section  402  that lists a summary of the episodes and other device and system events that have occurred since last interrogation of cardiac defibrillator  20 , threshold test results  404  that indicate current pulse thresholds, brady counters  406 , a battery status  408  that indicates a current voltage and status of the battery, and a daily measurement graph section  412  that includes one or more daily graphs over a period of time such as the prior year. Examples of such graphs include an intrinsic amplitude graph, a pace impedance graph, and a shock impedance graph. 
     In addition to displaying high-level cardiac data in various sections, system summary window  400  associates and displays a shortcut link  405  for each section such that the user can quickly view detailed cardiac data by presented by specific display screens by clicking on the appropriate shortcut  405 . Therefore, shortcut links  405  reduce the time required for the user to perform standard follow-up tests and reach the specific programming screens offered by programmer  60 . 
     Navigation buttons  415  and  420  are another feature of system summary window  400  that results in time savings to the user. With the navigation buttons  415  and  420  the user is able to quickly move from one of the programming screens to another rather than having to memorize the sequence of screens that enabled him or her to reach the desired programming screen. Navigation button  415  allows navigation to screens that programmer  60  has previously displayed on display screen  120 . Once the user has displayed previous screens, navigation button  420  allows a user to advance toward the most recently viewed screen. Thus, after programmer  60  displays a sequence of screens to the user based on user input, the user can traverse throughout the sequence using navigation buttons  415  and  420 . 
     Another time saving feature of system summary window  400  is toolbox  410  where common programming tasks are grouped in a single section for the benefit of the user. In the embodiment illustrated in FIG. 4, eight tool buttons are grouped in order from left to right with the first being the most common programming task i.e., viewing the system summary window  400 . The remaining common programming tasks include: a quick system check, tachy parameter programming, brady parameter programming, general programmer setup, viewing therapy history, diagnostic evaluation and electrophysiologic test. By grouping the most commonly occurring tasks together at the most accessible section of the system summary window  400 , the user spends less time navigating through complex screens. 
     Yet another efficient and time saving feature of system summary window  400  is the ability to concurrently interrogate programmer  60  while printing episodes to a strip recorder. More specifically, when the user selects print button  425  programmer  60  will print the summary information to a strip recorder. Other cardiac information, such as the stored electrograms along with the corresponding intervals and markers, can also be printed from other screens. More specifically, the cardiac data will be printed in the background and batch printed in order to save time. Furthermore, according to the invention, programmer  60  can concurrently print episode data and interrogate defibrillator  20  to retrieve more episode data. The user does not need to wait until the print out is complete before moving to the next area of interest. 
     FIG. 5 illustrates display screen  102  presenting one embodiment of a conversion summary window  500  that presents a graphical summary of the episodes that have occurred. Conversion summary screen  500 , displays a global summary of the episodes that have occurred in the patient. According to the invention, this global summary is displayed in a graphical, hierarchical fashion in order to give the user quick access to episodes of interest and the pertinent information of the episodes. Because the episodes are grouped by a common data characteristic, such as the zone of detection or type, there is no need for the user to individually select an episode in order to examine the details of an episode of interest. 
     Using date range selection  510 , the user has the ability of displaying episodes that have occurred over the lifetime of cardiac defibrillator  20  or episodes that have occurred since cardiac defibrillator  20  was last reset. Section  520  of conversion summary window  500  displays, in a graphical, hierarchical arrangement, the episodes that have a common data characteristic such as having a common zone of detection or being of the same episode type. At the top level of the hierarchy  505 , the total number of episodes is displayed. The second level of the hierarchy  520  displays a plurality of user input mechanisms that catagorize the episodes based on the common data type. For example, episodes may be organized by zone of detection such as VF (ventricular fibrillation), VT (ventricular tachycardia), VT-1 (ventricular tachycardia), commanded and accelerated. Also, episodes may be organized by type episode type such as, PMT (pacemaker-mediated tachycardia) and ATR (atrial tachyarrhythmia response). 
     When a particular user input mechanisms is selected, such as user input mechanisms  525 , the user is presented a screen that displays specific details of the corresponding episodes, thereby saving the user time in navigating through several software screens in order to locate particular episodes of interest. 
     Summary window  500  also includes histogram button  530  by which the user is able to view atrial and ventricular events in a histogram format. FIG. 6A illustrates display screen  102  presenting one embodiment of a histogram window  600  having a histogram display area  620  for presenting the information. Using date range input  605  the user is able to specify whether programmer  60  should display all of the events, only those events that have occurred since device  20  was reset or those events falling within a particular date range. 
     Within histogram display area  620 , two histograms are illustrated an atrial event histogram and a ventricular event histogram. Both histograms have a horizontal axis that illustrates the rate of the event which, in this embodiment, ranges from 30 to 250 beats per minute (BPM). Magnification selection  610 , however, controls the vertical axis and allows the user to select a normal view or a magnified view for histogram display area  620 . In normal view, the histogram display area  620  presents the total number and percentage of paced and sensed events. In magnified view programmer  60  changes the vertical axes of histogram display area  620  from a percentage to an actual count and scales the vertical axis based on events falling within a portion of the horizontal axis. Thus, by selecting the magnification button  612  the user is able to easily view in enhanced detail the ventricular and atrial events that fall along the higher end of the horizontal axis. 
     FIG. 6B illustrates one embodiment of histogram window  600  where the user has elected to magnify a portion of the histogram. Here, the histogram display area  620 , has magnified the event data. The magnification of each graph is based on the events above triggers  630  such that all magnified data above triggers  630  will be visible and will not exceed the top line of the graph. Events, however, below the triggers  630  may appear clipped during magnification. In the illustrated embodiment programmer  60  has scaled the vertical axis to display up to 500 events. This feature is useful because the events that typically occur at higher rates, and in higher zones, are much less frequent than those that occur at lower rates. Therefore, in conventional systems, the resolution of those higher rates is difficult to see by the user. By including an option that allows the user to magnify the small section of higher rates, the user can view the data clearer without permanently altering the display of other lower rates. 
     Another inventive feature of programmer  60  is the ability to automatically default to a device activity screen anytime programmer  60  is interrogated and the patient is in an arrythmia at the time of interrogation. FIG. 7 illustrates display  102  presenting one embodiment of a device activity window  700  that displays essential information regarding the patient. In this manner, programmer  60  displays device activity window  700  and thereby allows for quick and efficient assessment of the status of the device and of the patient.