Method and apparatus for detecting and displaying diagnostic information in conjunction with intracardiac electrograms and surface electrocardiograms

A pacemaker generates and transmits real-time intracardiac electrogram signals to an external display device for display thereon. Simultaneously, the pacemaker senses a variety of events occurring either within the heart tissue or within the pacemaker itself and transmits signals representative of those events for display, using appropriate marker icons, along with the intracardiac electrograms. In this manner, a physician viewing the intracardiac electrograms is simultaneously apprised of the various events. In one example, events displayed along with the intracardiac electrograms include the detection of atrial and ventricular events occurring within the heart during a non-absolute refractory period following generation of a stimulation signal. Other examples of events displayed along with the intracardiac electrograms include operations triggered within the pacemaker as a result of the condition of the patient, such as an auto-mode switching event, or operations triggered within the pacemaker as a result of the condition of the pacemaker itself, such as a battery test operation. Still other examples of events include pacemaker programming operations triggered using a remote programming device by a physician. Such events include an electrophysiological artificially-induced arrhythmia operation. In the described example, the external display device also presents surface electrocardiograms along with the intracardiac electrograms and the event marker icons.

FIELD OF THE INVENTION 
The invention generally relates to implantable medical devices and to 
external programmer devices used in connection therewith and in particular 
to methods and apparatus for processing and displaying diagnostic 
information detected by the implantable medical device in conjunction with 
displays of intracardiac electrograms (IEGM's) and surface 
electrocardiograms (ECG's). 
BACKGROUND OF THE INVENTION 
A wide range of implantable medical devices are provided for surgical 
implantation into humans or animals. One common example is the cardiac 
pacemaker. Another is the implantable cardioverter defibrillator. Other 
examples include devices for stimulating or sensing portions of the brain, 
spinal cord, muscles, bones, nerves, glands or other body organs or 
tissues. 
Implantable medical devices, particularly pacemakers, are often configured 
to be used in conjunction with an external programmer device which allows 
a physician to display information sensed by the device. For a pacemaker, 
for example, the external programmer device may operate to display 
electrical cardiac signals detected by the pacemaker in the form of IEGM's 
and ECG's. An IEGM is a graphic depiction of electrical signals emitted by 
active cardiac tissue as detected by electrodes placed on or in the heart. 
An ECG is also a graphic depiction of the electrical signals emitted by 
active cardiac tissue but is detected using electrodes placed on the body 
surface rather than in or on the heart itself. 
One example of an external programmer that displays IEGM's and ECG's is an 
analyzer-programmer system (APS) identified as the APS II system which is 
provided by Pacesetter Inc. of Sylmar, Calif. More specifically, the APS 
II system displays IEGM's and surface ECG's in conjunction with icons 
representative of paced and sensed atrial and ventricular events such as 
atrial stimulus, ventricular stimulus, atrial activity outside atrial 
refractory/blanking period, ventricular activity outside ventricular 
refractory/blanking period, and the length of atrial refractory period. 
The APS II system also displays variable length horizontal lines 
representative of the length of the atrial and ventricular refractory 
periods and also displays numerical values indicative of measured 
intervals between the atrial and ventricular events. Further information 
regarding the detection and display of IEGM signals may be found in U.S. 
Pat. No. 5,620,473 to John W. Poore entitled "Calibration System for 
Pacemaker-Generated Intracardiac Electrogram" which provides for the 
display and calibration of IEGM signals. U.S. Pat. No. 5,620,473 is also 
incorporated by reference herein. 
Other components of the APS II system of Pacesetter Inc. operate to allow a 
physician to program the operation of the pacemaker to, for example, 
control the specific parameters by which the pacemaker senses the IEGM 
signals and the manner by which the pacemaker detects arrhythmia 
conditions within the heart and responds thereto. For example, the APS II 
system allows the physician to specify the sensitivity with which the 
pacemaker senses electrical signals within the heart and to further 
specify the amount of electrical energy to be employed for pacing the 
heart in circumstances where expected heart signals are not sensed. Still 
other components of the APS II system operate to display a variety of 
diagnostic information received from the pacemaker. More specifically, the 
APS II system displays the different types of diagnostic information set 
forth in TABLE I. 
TABLE I 
______________________________________ 
EVENT 
NAME EVENT TYPE 
______________________________________ 
AV A-pulse followed by a V-pulse 
AR A-pulse followed by an R-wave 
PVE Premature ventricular event 
PV P-wave followed by a V-pulse 
PR P-wave followed by an R-wave 
P@MTR-V P-wave at maximum tracking rate followed by a V-pulse 
P@MTR-R P-wave at maximum tracking rate followed by a R-wave 
MAGNET Magnet placed over the implanted device--either singly 
or in combination with an external telemetry system 
______________________________________ 
U.S. Pat. No. 5,431,691 to Snell et al. entitled "Method and System for 
Recording and Displaying a Sequential Series of Pacing Events" provides a 
detailed description of the operation of the APS II system of Pacesetter 
Inc. including a description of the processing and displaying of the 
diagnostic information set forth in TABLE I. In particular, the Snell et 
al. patent describes a technique whereby the pacemaker processes and 
records diagnostic data in the form of "event records" which allow the 
data to be efficiently stored within the pacemaker, transmitted to the APS 
II system, and displayed. U.S. Pat. No. 5,431,691 to Snell et al. is 
incorporated by reference herein. 
As can be seen from TABLE I, the events processed by the APS II system are 
primarily events sensed within the heart of the patient. Event records 
containing information pertaining to those events are recorded within the 
pacemaker for subsequent transmission to the external programmer for 
display thereon in a variety of formats including event record displays, 
event bar graphs, rate bar graphs, rate time graphs, and event time 
graphs, each under the control of the physician operating the external 
programmer. More specifically, the event record display presents the 
various detected events of TABLE I and the corresponding pacing rate with 
respect to the time of the occurrence of the event. For periods of time 
while the pacemaker is in a dual-chamber mode (such as DDD, DDI etc.), the 
events presented include PV, PR, AV (or V when the mode is VDDR or VDD), 
AR and PVC (premature ventricular contraction). For periods of time while 
the pacemaker is in a single-chamber mode (such as VVI, AAI etc.), the 
events are presented merely as paced or sensed. The event bar graph 
presents a histogram of different event types listing the total number of 
counts of each event type for a selected period of time. The event time 
graph presents histograms of event types vs. time of event occurrence. The 
rate bar graph presents histograms of sensed and paced events vs. their 
rate. The rate time graph presents histograms of rates vs. times. Further 
information regarding the different displays may be found in the Snell et 
al. patent. 
As can be appreciated, a wide range of useful information, particularly 
directed to events sensed within the heart, is thereby provided to assist 
the physician in rendering a diagnosis as to any arrhythmia or other 
condition the patient may exhibit or to assist the physician in making 
choices as to adjusting various parameters by which the pacemaker monitors 
and paces the heart. The information is displayed in a variety of 
convenient graphical formats to help the physician visualize the 
information quickly and easily to facilitate prompt and accurate 
diagnoses. 
The parent application referenced above describes various improvements to 
the APS II system. For example, the parent application describes 
improvements wherein the system records and displays numerous additional 
types of diagnostic data including data pertaining to 1) operational 
events triggered within the pacemaker as a result of the condition of the 
patient (such as automode switching events) and 2) operational events 
triggered within the pacemaker as a result of the condition of the 
pacemaker itself (such as battery tests or lead fault detection tests). 
The additional diagnostic data is displayed as part of one or more of the 
aforementioned event record displays, event bar graphs, rate bar graphs, 
rate time graphs, and event time graphs. 
Although the system described in the parent application, which displays the 
additional diagnostic information in conjunction with event records, 
represents an improvement over the ASP II system, further room for 
improvement remains. In particular, it would be desirable to also display 
at least some of the additional types of event record diagnostic 
information in conjunction with the aforementioned IEGM and surface ECG 
displays to allow the physician to view the additional event record 
diagnostic information while simultaneously viewing IEGM's or ECG's and it 
is primarily to that end that the present invention is directed. 
SUMMARY OF THE INVENTION 
In accordance with one aspect of the invention, a method is provided for 
detecting and displaying information using a system having an implantable 
medical device and an external display device wherein the implantable 
medical device is capable of generating a stimulation signal within heart 
tissue connected to the implantable medical device and is capable of 
sensing electrical signals and events occurring within the heart tissue. 
The information displayed includes IEGM's along with markers 
representative of electrical events detected during a non-absolute 
refractory period following generation of a stimulation signal with the 
heart tissue. The method includes the steps of detecting IEGM signals 
representative of the electrical activity of the heart tissue connected to 
the implantable medical device; generating a stimulation signal within the 
heart tissue; and detecting electrical events occurring within the heart 
tissue during a non-absolute refractory period following generation of the 
stimulation signal. The method includes the additional steps of 
transmitting, from the implantable medical device to the external display 
device, the IEGM signals and the signals representative of the events 
detected during the non-absolute refractory period; receiving the 
transmitted signals at the external display device; and, in response to 
the received signals, graphically displaying the IEGM signals on the 
external display device along with icons representative of the detected 
events. 
In one specific example, where the implantable medical device is a 
pacemaker, the events detected during the non-absolute refractory period 
following generation of the stimulation signal include the detection of 
atrial activity and the detection of ventricular activity. The external 
display device is a computer display screen or a computer print-out 
device. The external device additionally displays surface ECG's. The 
IEGM's and ECG's generated by the external display device are presented 
substantially in real-time. 
In accordance with another aspect of the invention, a method is provided 
for detecting and displaying information using an implantable medical 
device, an external display device and a remote programming device wherein 
the information displayed includes IEGM's along with markers 
representative of programming operations that had been triggered within 
the implantable medical device as a result of programming signals received 
from the remote programming device. The method includes the steps of 
receiving programming signals from the remote programming device using the 
implantable medical device; triggering operations within the implantable 
medical device in response to the received programming signals; and 
detecting IEGM signals representative of the electrical activity of the 
heart tissue. The method also includes the steps of transmitting, from the 
implantable medical device to the external display device, the IEGM 
signals along with signals representative of the operations triggered 
within the implantable medical device; receiving the transmitted signals 
at the external display device; and, in response to the received signals, 
graphically displaying the IEGM signals on the external display device 
along with icons representative of the programming operations that had 
been triggered within the implantable medical device. 
In one specific example, wherein the implantable medical device includes a 
pacemaker, the operations triggered within the pacemaker include 
artificially induced arrhythmia (hereinafter also referred to as 
electrophysiological (EP) Lab). The remote programming device may be a 
magnet operated by a physician or may be part of a programmer unit 
operated by a physician. As before, the external display device may 
additionally display surface ECG's, and the IEGM's and ECG's generated by 
the external display device are presented substantially in real-time. 
In accordance with yet another aspect of the invention, a method is 
provided for detecting and displaying information using an implantable 
medical device and an external display device wherein the information 
displayed includes IEGM's along with markers representative of operations 
that had been triggered within the implantable medical device by 
conditions sensed by the implantable medical device. The method comprises 
the steps of sensing conditions using the implantable medical device; 
triggering operations within the implantable medical device in response to 
the sensed conditions; and detecting IEGM signals representative of the 
electrical activity of the heart tissue. The method also includes the 
steps of transmitting, from the implantable medical device to the external 
display device, the IEGM signals along with signals representative of 
operations triggered within the implantable medical device in response to 
the sensed conditions; receiving the transmitted signals at the external 
display device; and, in response to the received signals, graphically 
displaying the IEGM signals on the external display device along with 
icons representative of the operations that had been triggered within the 
implantable medical device. 
In one example, wherein the implantable medical device includes a 
pacemaker, the pacemaker is capable of sensing conditions of the heart of 
a patient in which the pacemaker is implanted. The aforementioned 
operations are triggered based upon the sensed conditions of the heart and 
include operations such as automatic pacemaker mode switching (i.e. 
automode switching), pacemaker mediated tachycardia (PMT) detection, and 
premature ventricular contraction (PVC) detection, rate hysteresis search 
and AV/PV hysteresis search. 
Also in the example wherein the implantable medical device again includes a 
pacemaker, the pacemaker is additionally capable of sensing performance 
parameters representative of its own performance. The operations triggered 
within the pacemaker include operations such as a battery test and a lead 
fault detection test triggered by the sensed performance parameters. As 
before, the external display device may additionally display surface 
ECG's, and the IEGM's and ECG's generated by the external display device 
are presented substantially in real-time. 
Hence, with the invention, various methods are provided for graphically 
displaying a wide variety of diagnostic information in combination with 
IEGM and ECG displays not heretofore presented in a single convenient 
display to the physician, to thereby assist the physician in making quick 
and informed decisions regarding, for example, the patient's condition or 
the condition of the implantable medical device. 
Other objects and advantages of the invention are achieved as well. 
Apparatus embodiments of the invention are also provided.

DETAILED DESCRIPTION OF THE INVENTION 
The invention relates to improved techniques for providing information to a 
physician regarding the events detected by an implantable medical device. 
The invention will be described primarily with reference to a pacemaker 
used in conjunction with an external programmer device, but principles of 
the invention are applicable to other implantable medical devices and 
other external devices as well. 
The Figures illustrate a pacemaker/programmer system having a pacemaker for 
implantation into a patient and an external programmer for programming the 
operation of the pacemaker and for processing and displaying information 
received from the pacemaker regarding the condition of a patient in which 
the pacemaker is implanted and regarding the condition of the pacemaker 
itself. The information is stored within the pacemaker in an event record 
format which efficiently allows a wide variety of types of information to 
be stored, along with the date and time at which the information was 
stored, within the pacemaker for subsequent transmission to the external 
programmer. The external programmer includes processing units for 
receiving event records transmitted by the pacemaker and for generating a 
wide variety of graphical displays of the information contained within the 
event records under the control of the physician operating the external 
programmer. 
The Snell et al. patent, incorporated by reference above, describes a 
predecessor pacemaker/programmer system which also operates to generate, 
store and process certain types of information within event records to 
generate certain displays based upon the information contained within the 
event records. The pacemaker/programmer system of the present invention 
operates to generate, store and process many additional types of 
information within event records to generate enhanced displays based upon 
the information contained within the event records. In the following 
descriptions, for the sake of clarity in describing pertinent features of 
the enhanced pacemaker/programmer system, many details of the operation of 
the overall pacemaker/programmer system provided in the Snell et al. 
patent are not repeated herein. Additional operational details pertaining 
to either the pacemaker, programmer or both may be found in the following 
patents, each of which is also incorporated by reference herein: U.S. Pat. 
No. 4,940,052 entitled "Microprocessor controlled rate-responsive 
pacemaker having automatic rate response threshold adjustment"; U.S. Pat. 
No. 4,809,697 entitled "Interactive Programming And Diagnostic System For 
Use With Implantable Pacemaker"; U.S. Pat. No. 4,791,936 entitled 
"Apparatus For Interpreting And Displaying Cardiac Events Of A Heart 
Connected To A Cardiac Pacing Means"; U.S. Pat. No. 5,309,919 entitled 
"Method And System For Recording, Reporting, And Displaying The 
Distribution Of Pacing Events Over Time And For Using Same To Optimize 
Programming"; U.S. Pat. No. 4,944,299 entitled "High Speed Digital 
Telemetry System For Implantable Device"; U.S. Pat. No. 5,292,341 entitled 
"Method And System For Determining And Automatically Adjusting The Sensor 
Parameters Of A Rate-Responsive Pacemaker"; U.S. Pat. No. 5,423,867 
entitled "Rate-Responsive Pacemaker Having Automatic Sensor Threshold With 
Programmable Offset"; and U.S. Pat. No. 4,944,298 entitled "Atrial Rate 
Based Programmable Pacemaker With Automatic Mode Switching Means". 
First Exemplary Embodiment 
FIG. 1 illustrates an implantable pacemaker 10 coupled to a heart 12 by way 
of a ventricular lead 14 and an atrial lead 16. Ventricular lead 14 
includes an electrode 18 positioned in the right ventricle 20 of the heart 
and atrial lead includes an electrode 22 positioned in the right atrium 24 
of the heart. 
Various internal components of the pacemaker operate to sense the 
electrical activity of the heart, such as the presence of P-waves and 
R-waves, using electrodes 18 and 22 and to selectively stimulate the heart 
in response to events sensed within the heart by conducting electrical 
stimulation pulses to the heart using the electrodes. The pacemaker may be 
configured to operate in either a single-chamber mode or a dual-chamber 
mode. Certain of the events sensed within the heart are recorded by 
internal components of the pacemaker within event records for subsequent 
transmission to an external programmer (FIG. 2) for display thereon in a 
graphical format. TABLE II provides a list of sensed events stored in 
pacemaker 10 of FIG. 1 using event records while the pacemaker is 
operating is the dual-chambered mode. Notably, the events listed in TABLE 
II include three events P.sub.REF detected, R.sub.REF detected and 
P.sub.AV detected occurring during refractory periods following the 
generation of stimulation signals. 
TABLE II 
______________________________________ 
SENSED 
EVENT 
NAME SENSED EVENT TYPE 
______________________________________ 
AV A-Pulse Followed By A V-Pulse Detected 
AR A-Pulse Followed By An R-Wave Detected 
PVE Premature Ventricular Event Detected 
PV P-Wave Followed By A V-Pulse Detected 
PR P-Wave Followed By An R-Wave Detected 
P@MTR- P-Wave At Maximum Tracking Rate Followed By A V-Pulse 
V Detected 
P@MTR- P-Wave At Maximum Tracking Rate Followed By A 
R R-Wave Detected 
P.sub.REF 
P-Wave Detected During A Relative Post-Ventricular 
Atrial Refractory Period (PVARP) Not Followed By A 
Ventricular Pulse 
R.sub.REF 
R-Wave Detected During A Relative Ventricular 
Refractory Period 
P.sub.AV 
P-Wave Detected During An Atrial Refractory Period 
During An AV/PV Interval 
______________________________________ 
For periods of time when the pacemaker is operating in the single-chamber 
mode, the pacemaker stores paced, sensed, P.sub.REF and R.sub.REF events, 
rather than all of the events of TABLE II. 
Other internal components of pacemaker 10 of FIG. 1 operate to receive 
programming signals from an external programmer (FIG. 2) and to modify the 
operation of the pacemaker in accordance with the programming signals. 
Each time the pacemaker receives programming signals, the pacemaker 
records a record of the corresponding "programming event" as an event 
record for subsequent transmission to the external programmer for display 
thereon in a graphical format. TABLE III provides a list of programming 
events stored by the pacemaker 10 of FIG. 1. 
TABLE III 
______________________________________ 
PROGRAMMING 
EVENT NAME PROGRAMMING EVENT TYPE 
______________________________________ 
Mode Pacemaker Mode Programmed 
Base Rate Heart Base Rate Programmed 
Rest Rate Heart Rest Rate Programmed 
Maximum Maximum Pacemaker Tracking Rate Programmed 
Tracking Rate 
Maximum Maximum Pacemaker Sensor Rate Programmed 
Sensor Rate 
Rate Rate Responsive AV/PV Delay Programmed 
Responsive 
AV/PV Delay 
______________________________________ 
Still other internal components operate to automatically trigger pacemaker 
operations based upon the condition of the patient as sensed by the 
pacemaker. Such "patient condition-triggered events" are also stored 
within event records for subsequent transmission to, and display on, the 
external programmer. TABLE IV provides a list of all patient 
condition-triggered events stored using event records by pacemaker 10. 
TABLE IV 
______________________________________ 
PATIENT- 
CONDITION 
TRIGGERED PATIENT-CONDITION 
EVENT NAME TRIGGERED EVENT TYPE 
______________________________________ 
Auto-mode Pacemaker Mode Automatically Switched 
Switching 
PMT Detection 
Pacemaker Mediated Tachycardia (PMT) Detected 
PVC Detection 
Premature Ventricular Contraction (PVC) Detected 
Rate Rate Hysteresis Search Performed 
Hysteresis 
______________________________________ 
Still other internal components operate to automatically trigger pacemaker 
operations based upon the condition of the pacemaker itself, such as a 
battery test operation triggered in response to the detection of a low 
battery voltage. A record of such "pacemaker condition-triggered events" 
are also stored within event records. TABLE V provides a list of all 
patient condition-triggered events stored using event records by pacemaker 
10. 
TABLE V 
______________________________________ 
EMAKER- 
CONDITION 
TRIGGERED EMAKER-CONDITION 
EVENT NAME 
TRIGGERED EVENT TYPE 
______________________________________ 
Battery Test 
Battery Voltage Test Performed 
VARIO Test 
Minimum Capture Test Performed 
Diagnostic 
Diagnostic Data Suspended 
Data 
Suspension 
Lead Lead Fault Detection Test Performed 
Supervision 
RRT Test Recommended Replacement Time (RRT) Battery Test 
Performed 
______________________________________ 
Thus TABLES II-V list exemplary events stored by the pacemaker of the 
presently-described exemplary embodiment of the invention within event 
records. In other embodiments, not all of the events listed in the TABLES 
may be recorded. In still other embodiments, additional events may also be 
recorded. As can be appreciated, a wide range of variations are 
permissible within the scope of the invention. 
As noted, the various event records are stored within the pacemaker for 
subsequent transmission to, and display using, the programmer (FIG. 2) 
within a graphical display format. Alternatively, if the external 
programmer is currently in communication with the pacemaker, the event 
records may be immediately transmitted to the programmer as they are 
recorded. 
The specific format with which the different types of events are stored and 
otherwise processed differs somewhat depending upon the type of event. In 
particular, the sensed events listed in TABLE II may be stored in a 
different format from the various operational events listed in Tables 
III-V. The format for storing the operational events of TABLE II-V is 
referred to herein as an "event control records". As will be described 
below, event control records are handled somewhat differently during the 
generation of some of the displays presented by the external programmer. 
FIG. 2 illustrates an external programmer 100 configured for receiving the 
aforementioned event records from pacemaker 10 (FIG. 1) and for generating 
graphical displays or printouts of the event records. Programmer 100 
includes a printer 102 for printing out a graphical representation of the 
information contained within the event records and a display screen 104 
for displaying the graphical representation. Generation of the graphic 
displays is subject to the control of a physician or other user operating 
the external programmer. To this end, external programmer 100 presents 
various menus on display screen 104 for use in controlling operation of 
the programmer to program pacemaker 10 (FIG. 1) to perform any of the 
functions listed above in TABLE III. Various menus are also presented on 
display screen 104 for use in controlling operation of the programmer to 
generate displays on display screen 104 of information received from the 
pacemaker including the aforementioned graphical representations of the 
event records representative of the events listed above in TABLES II-V. 
Programmer 100 receives menu selections from the physician through a touch 
screen 108 which overlays display screen 104. Actual programming of the 
pacemaker is achieved using a telemetry head 106 which, in use, is placed 
is proximity to the pacemaker. 
With reference to FIGS. 3 and 4, internal components of pacemaker 10 and 
programmer 100 that are pertinent to the processing of event records 
within the pacemaker and to the generation of event record displays using 
the external programmer will now be described. Components of programmer 
100 are shown in FIG. 3. Components of pacemaker 10 are shown are shown in 
FIG. 4. Referring first to FIG. 3, a controller 110 of programmer 100 
controls graphic display 104 to display the aforementioned menus from 
which the physician may select, among other options, to program the 
operation of the pacemaker or to generate graphical displays of the event 
records previously recorded by the pacemaker. 
Assuming first that the physician chooses to program the pacemaker, a 
program function selection unit 112 controls graphic device 104 to display 
a list of the programming options corresponding to the programming events 
listed in TABLE II, i.e. the graphic device displays a list of the 
following programming options: Mode, Base Rate, Rest Rate, maximum 
Tracking Rate, Maximum Sensing Rate, and Rate Responsive AV/PV Delay. 
(Further information regarding these programming options may be found in 
the above-referenced patents.) The physician selects one or more of the 
programming options from the list then enters any pertinent parameters, 
such as the applicable pacemaker mode, rate value or delay value, on one 
or more display screens (not separately shown) presented by programmed 
function selection unit 112 using graphical display 104. A command 
transmitter unit 114 of telemetry head 106 transmits the appropriate 
command signals to pacemaker 10 to program the pacemaker in the selected 
manner. 
Referring to FIG. 4, the programming signals transmitted by programmer 100 
are received by a command receiver unit 116. A controller 118 operates in 
response to the received commands to program the appropriate pacemaker 
functional units (not shown) to perform the selected operations in 
response to the programming signals. Additionally, the programming signals 
are forwarded by command receiver unit 116 to a programmed function 
storage unit 120 which stores information pertaining to the received 
programming command as an event control record (along with the date and 
time that the command was received) in an event data storage unit 122 to 
thereby maintain a record of the receipt of the programming signal for 
subsequent access. Event data storage unit 122 may be a circular buffer 
configured as described in the Snell et al. patent. 
The event data storage unit additionally stores a wide variety of other 
pacemaker event information including event records corresponding to any 
of the other events listed within TABLES II-V. To this end, pacemaker 10 
additionally includes pacemaker condition-triggered function unit 123, a 
patient condition-triggered function unit 125 and a sensed event detection 
unit 127, each of which operates continuously and automatically within the 
pacemaker (subject to the overall control of controller 118) to detect 
particular events, trigger responsive operations and record information 
pertaining to the detected events within event data storage unit 122. The 
specific information to be recorded along with each event varies depending 
upon the particular event. For example, for the sensed events of TABLE II, 
the rate at which the event was detected is stored along with an 
identification of the type of sensed event and the date and time at which 
the event was detected. For the events of Tables III-V, the corresponding 
event control record that is stored includes an identification of the type 
of event, the date and time at which the event occurred and any additional 
pertinent information. For example, for an automode switching event, the 
event control records stored additionally contains an identification of 
the previous pacemaker mode and the new pacemaker mode. For a battery test 
event, the event control record additionally stores an indication of 
whether the battery failed the test. 
Now the purpose of the various functional units of the pacemaker of FIG. 4 
will be described. Pacemaker condition-triggered function unit 123 
continuously monitors the operation of other units of the pacemaker, such 
as the pacemaker battery (not shown) and triggers appropriate operations 
in response thereto. More specifically, pacemaker condition-triggered 
function unit 123 triggers a battery test, a VARIO test, a lead 
supervision test and an RRT criteria test. The battery test is 
periodically performed to determine if the battery has sufficient power 
by, for example, determining if the battery voltage has fallen below a 
predetermined minimum threshold and, if so, appropriate warning signals 
are generated. Also, the pacemaker may modify its own operations, perhaps 
to suspend further diagnostic data acquisition to save battery power. The 
VARIO test is a minimum capture test performed to determine the minimum 
voltage of a stimulation pulses sufficient to be captured and responded to 
by the heart. Typically, the voltage level for stimulation pulses is then 
set based upon the minimum capture threshold to ensure that a minimum 
amount of energy is used in each stimulation pulse while still ensuring 
adequate capture of the pulse. The lead fault detection test (also 
referred to a Lead Supervision test) is periodically performed to test the 
integrity of the electrical leads (FIG. 1) perhaps by sensing the 
impedance thereof. The recommended replacement time (RRT) test is 
periodically performed to determine if the battery, or other power source 
of the pacemaker, should be replaced and, if so, appropriate warning 
signals are generated. The RRT test differs from the previously-described 
battery test in that a more sophisticated set of tests are performed. 
Additionally, pacemaker condition-triggered function unit 123 may 
selectively suspend the further acquisition of diagnostic data. This is 
typically done if the battery begins to lose power. By suspending 
diagnostic data acquisition, a greater amount of remaining battery power 
is thereby preserved for sensing and pacing the heart. 
Each time an operation is triggered by pacemaker condition-triggered 
function unit 123, the unit also operates to store an event control record 
within data storage unit 122 representative of the triggered event. 
Accordingly, each of the events listed in TABLE III, above, may be 
recorded within the data storage unit. 
Patient condition-triggered function unit 125 continuously monitors the 
status of the patient's heart via an electrical sensor unit 129 connected 
to leads 14 and 16 (FIG. 1) and triggers appropriate operations in 
response to certain detected conditions. More specifically, patient 
condition-triggered function unit 125 triggers automode switching, PMT 
detection, PVC detection and an rate hysteresis operation. Automode 
switching is performed to automatically switch the pacing mode of the 
heart to, for example, switch from a dual mode to a single chamber mode. 
PMT detection is performed continuously to detect a pacemaker mediated 
tachycardia such as an endless loop tachycardia, a tracking atrial 
fibrillation. PMT is also referred to as pacemaker reentry tachycardia, 
circus tachycardia or endless loop tachycardia. If PMT is detected, 
appropriate responsive therapy is automatically performed by the pacemaker 
in an attempt to terminate the PMT. For example, atrial sensing may be 
terminated via an automode switching operation. PVC detection is performed 
continuously to detect premature ventricular contractions (i.e. 
ventricular contractions occurring during a pre-defined refractory 
period). The physician may elect to shorten the refractory period to 
ensure that PVC pulses are properly sensed. Proper sensing of PVC's may be 
helpful in eliminating or preventing PMT's. The rate hysteresis search is 
performed periodically to set the hysteresis escape rate. The hysteresis 
escape rate is typically set to a value less than the base rate to inhibit 
pulse generation in some circumstances to allow the heart further time to 
generate its own pulse. 
Each time an operation is triggered by patient condition-triggered function 
unit 125, the unit also operates to store an event control record within 
data storage unit 122 representative of the triggered event. Accordingly, 
each of the events listed in TABLE IV, above, may be recorded within the 
data storage unit. 
Sensed event detection unit 127 continuously monitors the signals received 
from the patient's heart to detect selected events and records pertinent 
information pertaining to the events within the data storage unit. More 
specifically, sensed event detection unit 127 detects each of the events 
listed in TABLE II. The last three events, namely P.sub.REF,R.sub.REF and 
P.sub.AV, are events occurring during a refractory period following 
generation of a stimulation pulse. Knowledge of these refractory events is 
helpful to the physician in setting refractory periods and the like. 
Thus while pacemaker 10 of FIG. 1 is in operation, it continuously monitors 
various aspect of its condition and the condition of the patient in which 
it is implanted and stores appropriate diagnostic information as event 
records in event data storage unit 122. Additionally, as noted above, the 
pacemaker may receive programming commands which are also stored in the 
data storage unit. 
Ultimately, the physician may wish to display diagnostic information 
pertaining to any of the events previously recorded. Such may be desirable 
during a follow-up session with the patient in which the pacemaker is 
implanted. To display the diagnostic information, the physician then 
selects for the display of recorded events (by using appropriate menus not 
separately shown herein displayed by graphic device 104 of FIG. 3). 
Controller 110 forwards appropriate event record retrieval commands to 
pacemaker 10 (FIG. 4) via command transmitter unit 114 of telemetry head 
106. The retrieval commands are received by command receiver unit 116 of 
the pacemaker of FIG. 4 and forwarded to an event record access unit 131 
which retrieves all stored event records from event data storage unit 122 
for transmission to the programmer via a data transmitter unit 130. The 
event records are received by a data receiver unit 132 of telemetry head 
106 of the programmer of FIG. 3 and forwarded to an event display 
generation unit 134. The event display generation unit operates to display 
a representation of the event records using either graphic device 104, 
printer 102, or both. Additionally, the event display generation unit may 
trigger an annunciator 136 to generate an audible sound upon the display 
of certain event records to help direct the physician's attention to the 
display. 
A variety of graphical displays of information contained within the event 
records may be generated under control of the physician. In the presently 
described exemplary embodiment, the following graphical displays of 
information contained within the event records may be displayed under the 
control of the physician: event record displays, event bar graphs, rate 
bar graphs, rate time graphs, and event time graphs. The event record 
display presents the various detected events of Tables II-V and the 
corresponding pacing rate with respect to the time of the occurrence of 
the event. Briefly, for periods of time while the pacemaker is in a 
dual-chamber mode (such as DDD, DDI etc.), the events presented include 
PV, PR, AV (or V when the mode is VDDR or VDD), AR and PVC (premature 
ventricular contraction). For periods of time while the pacemaker is in a 
single-chamber mode (such as VVI, AAI etc.), the events are presented 
merely as paced or sensed. The event bar graph presents a histogram of 
different event types listing the total number of counts of each event 
type for a presented period of time. The event time graph presents 
histograms of event types vs. time of event occurrence. The rate bar graph 
presents histograms of sensed and paced events vs. their rate. The rate 
time graph presents histograms of rates vs. times. In other embodiments, 
more or fewer displays may be generated. Details of the manner by which 
the various event record displays are generated are provided in the Snell 
et al. patent. Accordingly, the following descriptions will be directed 
primarily to the portions of selected displays containing additional 
information not provided by the display screens of the Snell et al. 
patent. 
FIG. 5 illustrates an exemplary event record display screen 140 for events 
recorded during a period of time when the pacemaker was in a dual-chamber 
mode. The event record display screen includes a graphical display 142 of 
recorded events shown using various graphical icons distributed along a 
horizontal time-axis and a vertical rate axis. The events displayed may 
include any of the events listed in the TABLES above. The sensed events of 
TABLE II are represented each by a unique icon positioned along the 
time-axis of the graphic display at the time at which the events as sensed 
are recorded within the corresponding event record and positioned along 
the rate axis at a location representative of the rate at which the event 
was sensed. In the example of FIG. 5, rates are scaled between 30 and 190 
pulses per minute (ppm). Legend 144 provides a summary of the unique 
graphical icons presented in display 142 such as: an A for an AR event; a 
P for PR event; a square black box with a reverse video A' for an AV 
event; a square black box with a reverse video P' for a PV event; a *' for 
a PVE event; a white square box for a P.sub.AV event; an upside down black 
triangle for P.sub.REF event; a back triangle for R.sub.REF event; etc. 
All other events (i.e. the events listed in Tables III-V) are identified 
as event markers' and are graphically represented by sequential arabic 
numerals each within a circle, such as a 1 in a circle. The event markers 
themselves are displayed along a top portion 145 of graphical display 142 
at a point along the time-axis corresponding the time at which the event 
was recorded by the pacemaker. The event markers, however, are not scaled 
along the vertical rate axis. For an automode switching event, in addition 
to providing an arabic numeral in a circle, the previous and subsequent 
pacemaker modes are also displayed (e.g. DDD v. DDI). 
For data collected during a period of time when the pacemaker was in a 
single-chamber mode, the event record display shows a solid black square 
box with a reverse video s' for a paced event, an a' for a sensed event, 
an upside down black triangle for a P.sub.REF event and a black triangle 
for an R.sub.REF event 
In the dual-chamber example of FIG. 5, a variety of AV, PV, AR and PR 
events are shown, along with four refractory period events 147: one 
P.sub.AV event followed by two P.sub.REF events and a single R.sub.REF 
event. The latter R.sub.REF event is followed by a star icon indicated the 
first subsequent sensed event. 
The event record display also provides a selectable time scale list 150 to 
allow the physician to select the time scale over which data is to be 
displayed within graphical display 142. As shown, exemplary time scales 
include fifteen seconds, one minute, five minutes, fifteen minutes and 
thirty minutes. Although not shown, additional time scales include one 
hours, two hours, five hours, twelve hours, thirty hours, sixty hours, one 
hundred twenty hours, one week, two weeks, four weeks, eight weeks, 
sixteen weeks, thirty weeks, and fifty-two weeks. Depending upon the time 
scale, the event record display may not be able to show all individual 
events. If so, the event record display presents a compressed display with 
time slots providing the maximum, minimum and average rates of the events 
within the time slots. 
The event record display also provides a ZOOM button 152 which, upon 
selection, causes the external programmer to selectively display only a 
portion of the previous event record display. At that time, the ZOOM 
button is replaced with an UN-ZOOM button to allow for a return to the 
previous display. Furthermore, the event record display includes a time 
bar 154 which graphically indicates the portion of the total amount of 
event record data received from the pacemaker that is currently displayed. 
In the example of FIG. 5, only about one third of the total event record 
data retrieved from the pacemaker is displayed. Selection of one of the 
arrow buttons 156 and 158 causes the graphical display to be scrolled to 
the left or right, respectively, to display other portions of the event 
record data received from the pacemaker. Additionally, a vertical line 160 
is displayed to provide a marker to assist the physician in scrolling or 
otherwise examining data. Although not shown, still other buttons may be 
presented on the display including, for example, a PRINT button or a 
CANCEL button. 
A selectable event marker list 162 displays a list of the displayed event 
markers by number. Upon selection of one the events listed in the event 
marker list, programmer 100 (FIG. 3) generates a pop-up display providing 
pertinent information pertaining to the selected event marker. 
FIG. 6 provides an example of a pop-up display providing information 
pertaining to one event marker, specifically a "base rate change" 
programming event recorded by the pacemaker (and identified within FIG. 5 
as event marker 1'). As can be seen from FIG. 6, the pop-up display 
provides a textual description of the base rate programming operation 
including the new base rate as well as the date and time at which the base 
rate change occurred. Selection of a CONTINUE button 148 within the pop-op 
display causes the external programmer to redisplay the event record 
display of FIG. 5 to allow for selection of another event marker for 
generation of another pop-up display or for selection of any other 
appropriate function. 
For each different event marker, different information may be provided 
within the pop-up display. Generally speaking, all pertinent information 
stored as part of the event control record is displayed. Thus, for 
example, in the pop-up display generated from a battery test event marker, 
the pop-up display indicates whether the battery failed the test and 
additionally displays the date and time. Additional diagnostic information 
may be presented as well. For example, for a pop-up display generated from 
an RRT test event marker wherein the recommended replacement has been 
reached, the following information is presented along with the date and 
time of the RRT: 
"Pulse generator has reached RRT for the following possible reasons: 
1. Battery is RRT; 
2. Battery is near RRT. 
3. RRT Triggered because of high output pacing. 
4. RRT was possibly triggered by applied defibrillator/discharge 
5. RRT could have been triggered by implantable defibrillator." 
Referring to FIG. 7, an exemplary event bar graph display 170 is shown 
having a bar graph 172 providing a set of bars each separately 
corresponding to one of the sensed events listed in TABLE II, namely PV, 
PR, AV, AR, PVE and the three refractory period events P.sub.REF, 
R.sub.REF and P.sub.AV. The bars are distributed along a vertical axis of 
the bar graph and extend upwardly along a vertical axis representative of 
Percentage of Total Time'. Each of the bars for the PV, PR, AV, AR events 
are sub-divided into different sections. More specifically, a PV 174 bar 
is split into three sections to show the relative percentages of data 
collected either @MTR-V, above the base rate or below the base rate. A PR 
bar 176 is split into two sections to show the relative percentages of 
data collected either above the base rate or below the base rate. An AV 
bar 178 is split into three sections to show the relative percentages of 
data either sensor driven, collected above the base rate or collected 
below the base rate. An AR bar 180 is also split into three sections to 
show the relative percentages of data either sensor driven, collected 
above the base rate or collected below the base rate. The remaining bars: 
a PVE bar 182, a P.sub.REF bar 184, a R.sub.REF bar 186, and a P.sub.AV 
bar 188 are not individually sub-divided. An event count table 190 is also 
provided which lists the actual numerical counts of each category of event 
shown in the event bar graph. For event records recorded during periods of 
time when the pacemaker was in a single-chamber mode, the event histogram 
includes only histogram bars for sensed, paced, P.sub.REF and R.sub.REF. 
Thus a few exemplary displays of the event record data have been 
specifically illustrated. Additionally, a variety of other displays are 
generated by the exemplary embodiment of the invention including the 
aforementioned event bar graphs, rate bar graphs, rate time graphs, and 
event time graphs, which each provide different graphical representations 
of the sensed events of TABLE II. Additionally details regarding the 
characteristics of those displays are provided in the Snell et al. patent. 
Of course, it should be understood, that in the exemplary embodiment 
herein described, each of those displays is modified as appropriate to 
additionally incorporate the refractory period events P.sub.REF, R.sub.REF 
and P.sub.AV. Also, it should be noted that a wide variety of other types 
of displays of the event records may alternatively be generated in 
accordance with the principles of the invention. For example, a graphical 
display may be generated that merely provides a list of all of the event 
records along with the date and time at which the events were recorded, 
perhaps arranged in chronological order. 
Eventually, the physician terminates the presentation of graphical 
representations of the event records by selecting an appropriate menu 
option, such as a CANCEL menu option (not shown), and can thereafter 
select other programmer operations. 
What has been described this far is a first exemplary embodiment of the 
invention wherein the external programmer generates various printouts or 
displays of event records based upon information received from the 
pacemaker. In the following, a second exemplary embodiment of the 
invention will be described wherein an external programmer generates 
various printouts or displays of IEGM's and surface ECG's with selected 
event markers displayed long with the IEGM's and surface ECG'S. 
Second Exemplary Embodiment 
Referring to FIGS. 8-13, the second exemplary embodiment of the invention 
will now be described. An external programmer 200 (shown in block diagram 
form in FIG. 8) receives signals from an implanted pacemaker 201 (shown in 
block diagram form in FIG. 9) and generates various displays therefrom. 
Preferably, pacemaker 201 is capable of transmitting all of the same event 
record information described above in connection with the system of FIGS. 
1-7 and external programmer 200 is capable of displaying or printing out 
all of the same event record displays. Additionally, though, pacemaker 201 
also transmits data from which external programmer 200 generates real-time 
IEGM displays and printouts. Some of the events described above that are 
displayed using the event record displays, such as automatic mode 
switching events, are also displayed by external programmer 200 along with 
the real-time IEGM's. The events are displayed using marker icons 
positioned adjacent to the IEGM displays. Furthermore, pacemaker 201 
transmits some additional types of event information beyond those which 
are described above, such as atrial or ventricular events detected during 
a non-absolute refractory period, which are also displayed by the external 
programmer using event marker icons positioned along with IEGM's. Also, 
external programmer 200 receives signals from a surface ECG monitoring 
unit 203 (shown in FIG. 8) from which the external programmer additionally 
generates displays or printouts of real-time surface ECG's along with the 
IEGM's and the event markers. As before, the pacemaker can operate in 
either a dual-chamber mode or a single-chamber mode and the information 
transmitted by the pacemaker and the displays and printouts generated by 
the external programmer may differ depending upon the mode. 
The components of the system of FIGS. 8-13 are similar to the components of 
the system of FIGS. 1-7 and only pertinent differences will be described 
in detail. In particular, the following descriptions will be directed 
primarily to those components that generate the real-time IEGM/ECG 
displays and to those components that process event data for displaying 
event markers along with the real-time IEGM/ECG displays. 
TABLES VI-IX set forth the various events that are processed as event 
marker data and displayed using marker icons in connection with the 
real-time IEGM/ECG displays. 
TABLE VI is a list of sensed events displayed by the external programmer 
along with IEGM/ECG's for data collected while the pacemaker is operating 
is the dual-chamber mode. Notably, the events listed in TABLE VI include 
two events P' and R' detected during non-absolute refractory periods. P' 
symbolizes atrial activity detected during a non-absolute refractory 
period and R' symbolizes ventricular activity detected during a 
non-absolute refractory period. 
TABLE VI 
______________________________________ 
SENSED 
EVENT 
NAME SENSED EVENT TYPE 
______________________________________ 
A Atrial Stimulus 
V Ventricular Stimulus 
P Atrial Activity Outside Atrial Refractory/Blanking 
Period 
R Ventricular Activity Outside Ventricular 
Refractory/Blanking Period 
Length End of Atrial Refractory Period 
of A 
Ref. 
Length End of Ventricular Refractory Period 
of V 
Ref. 
P' Atrial Activity During Non-Absolute Refractory Period 
R' Ventricular Activity During Non-Absolute Ventricular 
Period 
______________________________________ 
For periods of time when the pacemaker is operating in the single-chamber 
mode, the pacemaker may store fewer types of event information such as, 
for example, only A, P, Length of A Ref. and P', rather than all of the 
events of TABLE VI. 
TABLE VII is a list of "programming events" displayed by the external 
programmer along with IEGM/ECG's. 
TABLE VII 
______________________________________ 
PROGRAMMING 
EVENT NAME PROGRAMMING EVENT TYPE 
______________________________________ 
EP Test Electro-Physiological Test (i.e. Physician- 
Controlled Arrhythmia Event) 
______________________________________ 
TABLE VIII is a list of "patient condition-triggered" events displayed by 
the external programmer along with the IEGM/ECG's. 
TABLE VIII 
______________________________________ 
PATIENT- 
CONDITION 
TRIGGERED 
EVENT NAME 
PATIENT-CONDITION TRIGGERED EVENT TYPE 
______________________________________ 
Auto-mode Pacemaker Mode Automatically Switched 
Switching 
PMT Detection 
Pacemaker Mediated Tachycardia (PMT) Detected 
PVC Detection 
Premature Ventricular Contraction (PVC) Detected 
Rate Rate Hysteresis Search Performed 
Hysteresis 
AV/PV AV/PV Hysteresis Search Performed 
Hysteresis 
______________________________________ 
TABLE IX is a list of "patient condition-triggered events" displayed by the 
external programmer along with the IEGM/ECG's. 
TABLE IX 
______________________________________ 
EMAKER- 
CONDITION 
TRIGGERED EMAKER-CONDITION 
EVENT NAME TRIGGERED EVENT TYPE 
______________________________________ 
Battery Test Battery Voltage Test Performed 
VARIO Test Minimum Capture Test Performed 
Lead Lead Fault Detection Test Performed 
Supervision 
______________________________________ 
Thus TABLES VI-IX list exemplary events displayed by the external 
programmer along with IEGM/ECG's. In other embodiments, not all of the 
events listed in TABLES VI-IX are necessarily displayed. In still other 
embodiments, additional events may also be displayed including, for 
example, some of the additional events listed above in TABLES II-V. As can 
be appreciated, a wide range of variations are permissible within the 
scope of the invention. 
Referring now to FIG. 8, programmer 200 includes a printer 202 and a 
display screen 204. External programmer 200 presents various menus on 
display screen 204 for use in controlling operation of the programmer to 
program pacemaker 201 (FIG. 9). Various menus are also presented on 
display screen 204 for use in controlling operation of the programmer to 
generate displays of information received from the pacemaker including the 
aforementioned real-time IEGM/ECG displays containing event markers 
representative of the events listed above in TABLES VI-IX. A controller 
210 controls graphic display 204 to display the aforementioned menus. 
Programmer 200 receives menu selections from a physician through a touch 
screen 208 which overlays display screen 204. Actual programming of the 
pacemaker is achieved using a telemetry head 206 which, in use, is placed 
in proximity to the pacemaker. 
As far as the generation of real-time IEGM/ECG displays is concerned, the 
physician selects for display of IEGM/ECG data via one of the menus 
presented by display screen 204 under the control of controller 210. 
Appropriate signals are sent under the control of controller 210 to 
command transmitter unit 214 of telemetry head 206 for transmission to a 
command receiver unit 216 (FIG. 9) of the pacemaker 201. A controller 218 
of the pacemaker operates to control an electrical sensor unit 229 to 
begin detecting signals representative of IEGM's using electrical leads 
(shown in FIG. 1) implanted in the heart. The IEGM signals are forwarded 
to an IEGM and event marker data transmitter unit 230 for transmission to 
the external programmer. 
An IEGM and marker data receiver unit 232 (FIG. 8) of the telemetry head 
206 of external programmer 200 receives the IEGM data and forwards the 
data to an IEGM/Marker display generation unit 234. IEGM/Marker display 
generation unit 234 processes the data to generate real-time IEGM displays 
for presenting on either graphic display device 204, printer 202, or both. 
If so configured, external programmer 200 also receives ECG data from 
surface ECG monitoring unit 203 via an ECG data receiver unit 233. The ECG 
data is also forwarded to IEGM/Marker display generation unit 234 which 
simultaneously generates ECG displays along with the IEGM displays. 
The IEGM/ECG displays are presented in real-time with the data scrolling 
left to right across the display screen. An exemplary scrolling IEGM/ECG 
display generated by IEGM/Marker display generation unit 234 is provided 
in FIG. 10. The IEGM and ECG portions of the display are identified, 
respectively, by reference numerals 250 and 252. At any time, the 
scrolling IEGM/ECG display may be frozen, but pressing a button labeled 
"Freeze" 254, to allow the user to more closely scrutinize potions of the 
displayed data. Thereafter, the display may be switched back to a 
continuously scrolling real-time display. An exemplary frozen IEGM/ECG 
display is provided in FIG. 11. The IEGM and ECG portions of the display 
are identified, respectively, by reference numerals 256 and 258. 
While IEGM/ECG displays are being presented, pacemaker 201 (FIG. 9) may 
detect any of the various events listed in TABLES VI-IX. If so, event 
records representative of the detected events are created within the 
pacemaker and stored within an event data storage unit 222 and also 
forwarded in real-time to IEGM and event marker data transmitter unit 230 
for transmitting, along with the aforementioned IEGM signals, to the 
external programmer. The event marker data is received along with the IEGM 
data by IEGM and marker data receiver unit 232 (FIG. 8) of external 
programmer 200 and forwarded to IEGM/marker display generation unit 234. 
IEGM/Marker display generation unit 234 processes the marker data to 
generate icons for displaying along with the IEGM/ECG displays. 
Exemplary markers illustrative of sensed events are shown in the examples 
of FIGS. 10 and 11. More specifically, the scrolling real-time display of 
FIG. 10 illustrates two automode switching events (both represented by an 
m') along with various sensed atrial and ventricular stimulus events 
(represented by A and V, respectively), and various atrial and ventricular 
events sensed during non-absolute refractory periods (represented by P' 
and R'). As to the automode switching events, when the mode is switched, 
an m' with a right-facing bracket is displayed adjacent to the IEGM 
display and a textual notification is provided on the bottom of the 
display identifying the new mode (e.g. Mode Switched to DDI'). When the 
mode switches back, an m' with a left-facing bracket is displayed and a 
textual notification is provided on the bottom of the display identifying 
the mode to which the pacemaker has returned. 
As to the choice of particular icons for representing the various other 
events of TABLES VI-IX, in the presently described example the following 
icons are used to represent the sensed events of TABLE VI: A' for atrial 
stimulus; V' for ventricular stimulus; P' for atrial activity outside 
atrial refractory/blanking period; R' for ventricular activity outside 
ventricular refractory/blanking period; P" for atrial activity during 
non-absolute refractory period; R" for ventricular activity during 
non-absolute ventricular period. (In other embodiments, P' is instead 
represented using a P with an overbar and R' is represented using an R 
with an underbar.) Horizontal bars of appropriate length are provided to 
illustrate the lengths of the atrial and ventricular refractory periods. 
The following icons are used to represent the other events of TABLES 
VII-IX: B' for battery test; V' for VARIO test; the aforementioned m' for 
automode switching; and X' for all of the other events. 
The presentation of markers within the frozen display of FIG. 11 are 
similar to that of the scrolling display of FIG. 10 but, instead of 
displaying an m' with a left- or right-facing bracket, the specific modes 
associated with automode switching events (such as VVI or DDI) are 
displayed with the appropriate left or right-facing bracket such that the 
user need not look to the textual display at the bottom of the screen to 
see that associated modes. Also, rather than use an X' to represent a 
variety of different events as in the real-time display, when the system 
is presenting a freeze mode display, RHS' is used for rate hysteresis; A/P 
VHS' for AV/PV hysteresis search; PMT' for PMT detection; PVC' for PVC 
detection; EP' for EP test; and Lead Supv.' for a lead fault detection 
test. 
Although FIGS. 10 and 11 illustrates only a few selected events, in the 
presently described exemplary embodiment, any of the events listed in 
TABLES VI-IX are to be displayed within the IEGM/ECG display. In other 
embodiments, additional events may also be displayed including any of 
those listed in TABLES II-V. 
The manner by which the system processes the various events of TABLES VI-IX 
for display will now be briefly described with continued reference to 
FIGS. 8 and 9. As far as the programming events of TABLE VII are 
concerned, a program function selection unit 212 controls graphic device 
204 to display a list of the available programming options, including the 
induced arrhythmia (EP Test) operation listed in TABLE VII, and the 
physician selects one or more of the programming options from the list. 
(As will be described below, the programming options are presented on the 
right hand side of the real-time IEGM/ECG display (FIG. 10). 
Alternatively, the programming options are presented using other menu 
display screens.) Command transmitter unit 214 of telemetry head 206 
transmits the appropriate command signals to pacemaker 202 to program the 
pacemaker in the selected manner. The AV/PV Hysteresis Search is performed 
to set the AV/PV delay value. The EP Test is performed to temporarily 
induce arrhythmia. Details regarding EP Tests may be found in U.S. Pat. 
No. 5,653,737 to van Lake entitled Programmable pacemaker for noninvasive 
EP testing for atrial tachycardias with ventricular support' which is 
incorporated by reference herein. 
Referring to FIG. 9, the programming signals transmitted by programmer 200 
are received by a command receiver unit 216. Controller 218 operates in 
response to the received commands to program the appropriate pacemaker 
functional units (not separately shown) to perform the selected operations 
in response to the programming signals. Additionally, the programming 
signals are forwarded by command receiver unit 216 to a programmed 
function storage unit 220 which stores information pertaining to the 
received programming command as an event control record in event data 
storage unit 222. The event record for that programming event is also 
forwarded in real-time via IEGM and event marker data transmitter unit 230 
for transmission to external programmer 200 (FIG. 8) for display thereon 
using appropriate icons within the real-time IEGM/ECG display. 
As to the non-programming events of TABLES VI and VIII-IX, pacemaker 202 
employs a pacemaker condition-triggered function unit 223, a patient 
condition-triggered function unit 225 and a sensed event detection unit 
227, each of which operates continuously and automatically within the 
pacemaker (subject to the overall control of controller 218) to detect 
particular events, trigger responsive operations and record information 
pertaining to the detected events within event data storage unit 222. The 
specific information to be recorded along with each event varies depending 
upon the particular event. 
Pacemaker condition-triggered function unit 223 continuously monitors the 
operation of other units of the pacemaker, such as the pacemaker battery 
(not shown) and triggers appropriate operations in response thereto. For 
example, pacemaker condition-triggered function unit 223 triggers a 
battery test, a VARIO test and a lead supervision test (described above in 
connection with FIG. 4.) Each time an operation is triggered by pacemaker 
condition-triggered function unit 223, the unit also operates to store an 
event control record within data storage unit 222 representative of the 
triggered event and the event record for that event is also forwarded in 
real-time via IEGM and event marker to data transmitter unit 230 for 
transmission to external programmer 200 for display thereon using 
appropriate icons within the real-time IEGM/ECG display. 
Patient condition-triggered function unit 225 continuously monitors the 
status of the patient's heart via electrical sensor unit 229 and triggers 
appropriate operations in response to certain detected conditions. In 
particular, patient condition-triggered function unit 225 triggers 
automode switching, PMT detection, PVC detection, a rate hysteresis search 
operation and an AV/PV hysteresis search operation. As with the 
aforementioned pacemaker condition-triggered events, each time an 
operation is triggered by patient condition-triggered function unit 223, 
the event record for that event is forwarded in real-time to the external 
programmer for display thereon using appropriate icons within the IEGM/ECG 
display. 
Sensed event detection unit 227 continuously monitors the signals received 
from the patient's heart to detect selected events and records pertinent 
information pertaining to the events within the data storage unit. More 
specifically, sensed event detection unit 227 detects each of the events 
listed in TABLE VI. The last two events, namely P' and R', are events 
occurring during a non-absolute refractory period. Knowledge of these 
events is helpful to the physician in setting refractory periods and the 
like. 
Thus a variety of events are detected by pacemaker 201 of FIG. 9 and 
forwarded in real-time for display by programmer 200 of FIG. 8 along with 
IEGM and surface ECG displays. Referring again to the exemplary displays 
of FIGS. 10 and 11, other information presented in the displays in 
additional to the aforementioned IEGM/ECG and event markers displays will 
now be described. Both the scrolling real-time display of FIG. 10 and the 
frozen display of FIG. 11 provide labels adjacent to the IEGM and ECG 
waveforms identifying the particular waveform (e.g. Surface ECG' and 
Atrial IEGM BI') and provide labels at the bottom of the display 
identifying the current pacing mode (e.g. DDD'), the current heart rate 
(e.g. 70 ppm), and the current A-V delay value (e.g. 175 msec). Both 
displays also provided calculated A-V delays and A and V timing intervals 
along with each displayed complex. For example, for the fourth complex 
shown in FIG. 10, a calculated A-V delay of 172 msecs is shown along with 
calculated A and V timing intervals of 680 and 852 msecs. 
The scrolling display of FIG. 10 also provides a test window 258 for 
allowing the user to select any of a variety of tests including the 
aforementioned EP test. Other selectable tests include V sense, A sense, V 
Capture-Amp, A Capture-Amp, V Capture-Width, A Capture-Width, V Capture 
Auto, A Capture Auto, V Sense Auto and A Sense Auto. These later tests are 
not particularly pertinent to the present invention and will not be 
described in detail. The selected test is triggered by pressing a Start 
Test' button 260 and terminated by pressing a Stop Test' button 262. As 
noted, activation of the EP Lab Test is detected by the pacemaker (FIG. 9) 
and ultimately causes a corresponding marker to be displayed along with 
the IEGM and ECG displays. Alternatively, the programmer (FIG. 8) itself 
may simply insert the EP Test marker into the IEGM/ECG display once the 
test has been activated. However, by having the pacemaker sense the EP 
Test and send an event record back to the programmer indicative thereof, 
feedback is thereby provided confirming that the pacemaker did indeed 
initiate the EP Test. 
Further with regard to the scrolling display of FIG. 10, at any time the 
user may press a Display Options' button (not separately shown) to present 
the display of FIG. 12 wherein the user can set or modify a variety of 
parameters. More specifically, the user may select any of the following: 
______________________________________ 
Surface ECG [ON / OFF] 
IEGM [OFF / A IEGM UNI / A IEGM BI / 
A IEGM SPE / V IEGM UNI / 
V IEGM BI / V IEGM SPE] 
Markers [ON / OFF] 
Surface ECG Gain 
[8.0 / 4.0 / 2.0 / 1.0 / 0.5] 
mv/div 
IEGM Gain [40 / 20 / 10 / 5 / 2.5 / 1 / 0.5] 
mv/div 
Sweep [25.0 / 12.5 ] mm/sec 
Surface ECG Filter 
[ON / OFF] 
IEGM Option [Filtered / Unfiltered] 
Pulses/Step [4 / 5 / 6 / 7 / 8 / 9 / 10] 
Sinus Node 
Recovery Delay [OFF / 2 / 3 / 4 /5] Seconds 
Auto Freeze [OFF / 1 / 2 / 3 / 4 / 5] Seconds 
Pulse Amplitude 
Step Size [.25 / .5] Volts 
______________________________________ 
Within the display of FIG. 12, the currently selected parameter is 
displayed in bold. The Sinus Mode Recovery Delay can only be set in 
conjunction with the EP Test. The Auto Freeze mode is only set in 
conjunction with a Auto Sense Test. The Surface ECG filter and IEGM Option 
parameters control the operation of ECG and IEGM filters within the 
programmer (not separately shown in the figures) which filter the IEGM and 
ECG data to provide a cleaner display of the data. Also, within the 
options display of FIG. 12, the user may trigger a freeze mode using 
button 266 or a start or stop ECG displays using button 268. 
Also with regard to the scrolling display of FIG. 10, at any time the user 
may press a Temp Parameters' button 270 to activate the usage of 
alternative temporary programmer parameters rather than the primary 
programmed parameters. More specifically, the user may temporarily re-set: 
the pacing mode (e.g. DDDR instead of VVIR) the rate (e.g. 70 instead of 
60 ppm); the sensor state (e.g. passive instead of active); the A-V delay 
value (e.g. 150 instead of 125); the ventricular pulse configuration (e.g. 
bipolar instead of unipolar); the ventricular sense configuration (e.g. 
bipolar instead of unipolar tip), the atrial pulse configuration (e.g. 
bipolar instead of unipolar) and the atrial sense configuration (e.g. 
bipolar instead of unipolar tip). Upon selection of the Temp Parameters 
button, an appropriate display (not shown in the figures) is presented to 
the user to allow for selection of any of the aforementioned temporary 
alternative parameters. 
As to the freeze display of FIG. 11, alternative control buttons are 
provided instead of those of the continuously scrolling display of FIG. 
10. In particular, left and right scroll bars 272 and 274 are provided to 
allow the user to selectively and slowly scroll the display to the left or 
right to see additional graphical information not currently displayed. 
Also a Center Vertical button 276 allows the display to be vertically 
centered. Additionally, the user may select IEGM gain, Surface Gain and 
Sweep Speed via input windows 278. Finally, a Start ECG' button 280 allows 
for the surface ECG display to be selectively activated and de-activated. 
At any time while the frozen or continuously scrolling IEGM/ECG displays 
are presented, the user may select for a printout of a portion of the 
displayed data by pressing an appropriate display button (not shown). FIG. 
13 provides an exemplary printout. As can be seen, the printout provides 
IEGM/ECG displays with appropriate markers and additionally provides a 
variety of other information including patient information, a list of 
pertinent ECG/IEGM parameters and a list of the primary vs. temporarily 
programmed parameters. 
Eventually, the physician terminates the presentation of the IEGM/ECG 
displays by selecting an appropriate menu option and can thereafter select 
other programmer operations such as the generation of event record 
displays as described above in connection with FIGS. 1-7. 
What has been described are systems for generating, storing, processing and 
graphically displaying a wide variety of information pertaining to events 
detected by a pacemaker. The various functional components of the 
exemplary system may be implemented using any appropriate technology 
including, for example, microprocessors running software programs or 
application specific integrated circuits (ASIC'S) executing hard-wired 
logic operations. Although described with respect to a pacemaker used in 
conjunction with an external programmer, aspects of the invention are 
applicable to other systems, such as systems employing other implantable 
medical devices or systems employing other types of external interfaces 
for use with the implantable device. The exemplary embodiments of the 
invention described herein are merely illustrative of the invention and 
should not be construed as limiting the scope of the invention.