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The evolution of computer application to assist during clinical electrophysiologic testing
The Evolution of Computer Application to Assist During Clinical Electrophysiologic Testing
P. Gillette, MD,* M. Zmijewski, M S , t a n d M. B. S h e l t o n , M S E E t
states of the microprocessor. These states dictate how the associated hardware, such as the pace-sense and user-interface hardware, are to behave. The stimulator's functional behavior as defined by the software is highly flexible and is typically limited only by the processing capabilities of the hardware. The flexibility of the controlling software allows for functional modifications and updates without necessarily changing the physical hardware; the existing software is simply exchanged with the revised software. Stimulator software, however, is generally restricted to control only a specific type of stimulator hardware due to the uniqueness of each microprocessor- and/ or microcomputer-based system. A microcomputer is an excellent hardware platform for a cardiac stimulator. Integrating the microprocessor circuitry with video, printer, and storage media (eg, a floppy disk) hardware components, a microcomputer provides the resources necessary for real-time process control, a user interface, report generation, and data collection. Given the advent of the microcomputer, increasingly sophisticated microcomputer-based stimulator applications have been developed for both clinical and commercial settings, which provide powerful tools for the electrophysiologist. One of the early microcomputer-based cardiac stimulators commercially available as a custom device was the Programmable Cardiac Stimulator, Model PCS-80, developed at the University of Montreal. 6 The Model PCS-80 is comprised of a microcomputer, a video display (CRT) and keyboard user interface, and an isolated dual-port stimulation interface. Included with the stimulator are standard stimulation protocols and the ability for the user to define protocols using a sequence of up to l0 software-defined pulse generators. Through software control, i0 real-time pulse generators with individ-
A wide variety of computer-based research stimulators have been developed for clinical and experimental use in cardiac electrophysiology.~-4 These devices provide users with stimulators whose primary logic is embodied in software, rather than hardware. Computer-based stimulators provide a system in which the user is typically able to adjust stimulation sequence timing and output parameter values manually or automatically through software control. Given the time-consuming and tedius nature of an electrophysiologic test and subsequent data analysis, 5 computer-based applications have been developed to reduce both the study and data analysis time.
Computer Application in Stimulator Design A microprocessor-based stimulator that typically combines microprocessor and analog circuitry with user interface provides a highly flexible, low-cost system upon which sophisticated functional applications may be developed. The microprocessorbased portion of the stimulator circuitry is comprised of discrete-logic integrated chips, such as the central processing unit (CPU), read-only memory (ROM), and random-access memory (RAM). In combination with software, a microprocessor can provide precise control of the analog portion of the stimulator hardware. Software is the sequence of steps defining the logic
* From the Medical University of South Carolina, Charleston, South Carolina. t From Medtronic Inc., Minneapolis, Minnesota. Reprint requests: M. Brent Shelton, Medtronic, 7000 Central Avenue MS T415, Minneapolis, MN 55432.
218
Computer Application to EP Testing
ually adjustable parameters may be cascaded to deliver stimulation sequences. A description of the stimulator detailed how the device can automatically be adjusted to deliver pulse patterns with periodic and cyclic modifiers. Beat-to-beat parameter variations may be produced by periodic modifiers, while sequence-to-sequence parameter variations parameters may be produced with cyclic modifiers. Adjustable parameters include pulse amplitude, pulse duration, and stimulus coupling intervals, such as drive train and premature stimuli.7 The Cordis Corporation developed a stimulator based on the Digital Equipment PC-350. Available only as a special-order prescription device, this system includes a microcomputer, a video display and keyboard user interface, a printer, and a dual-channel stimulation module. Hardware controls on the stimulation module allow for the independent adjustment of pulse amplitude, pulse width, and sensitivity on each channel. Standard stimulation protocols as well as AAI, VVI, and DDD pacemaker emulation protocols are controlled through software. The stimulation patterns can be user-defined and stored for quick recovery. Medtronic Incorporated developed a truly programmable dual-channel stimulator. In contrast the to above-described stimulators, the Model 2319 Dysrhythmia Research Instrument (DRI) allowed the user to define a protocol's sequence of operation completely, through the use of a Medtronic developed programming language called PACE. The PACE programming language includes statements such as Pace, Delay, Goto, On Sense Goto, If Condition Exists Goto. Each PACE statement has its own characteristic parameters. The DRI, available only as a custom device, consists of three components: the controlling Host microcomputer, the Digital Controller, and the Patient Interface Module. Connected between the Digital Controller and the patient, the Patient Interface Module hardware controls pacing and sensing functions. The Digital Controller communicates with the Host microcomputer during protocol execution via a IEEE-488 Standard interface. In conjunction with the Patient Interface Module, the Digital Controller executes the PACE protocols developed on the Host computer. The Host computer not only provides a PACE protocol editor with which to develop protocols, but provides a user interface for direct protocol control during protocol execution. To date, via the IEEE-488 interface, the DRI has been configured with three different microcomputers: Hewlett-Packard HP-85, a Digital Equipment Corporation PDP 11/23, and a IBM Personal Computer. The Model EP-2 Stimulator, developed by Digital Cardiovascular Instruments Incorporated, is a corn-
9 Gillette et
al,
219
mercially available FDA-approved dual-channel stimulator intended for clinical and experimental electrophysiologic studies of the heart. The batteryoperated device is comprised of a custom-based unit housing both the microcomputer and isolated pacesense circuitry, a video monitor and keyboard user interface, and a serial communications port for the attachment of a printer. All pacing and protocol execution parameters can be manually or automatically controlled through software. Nine standard stimulation protocols and several arrhythmia termination protocol are available through a single keystroke. In addition, customized versions of the standardized protocols may be assigned to five programmable keys, thus making preset versions of any protocol available via a single keystroke.
Computer Application in Automatic Event Detection and Analysis Although a computer-based electrophysiologic stimulator allows for precise and repeatable automation of protocol execution, the true utility of a computer-based stimulator is the additional software-based applications that may be integrated into the system. These applications include patient data management, waveform digitization and archival storage, and, perhaps most significant, electrophysiologic event onset detection and interval analysis. Several successful research computer applications for poststudy and during-study analysis of electrophysiologic data have been developed. Computerbased post-study analysisapplications typically require the user to indicate the electrogram event onsets through the use of a digitization board. The user indicates event onsets by placing electrophysiologic tracings recorded on paper during the study over the digitization board, specifies the onset points to be indicated on the digitizer pad, and then moves the digitizer board's input pen or mouse to the tracing locations for each of the specified points. This process is repeated for each event to be measured. When all electrophysiologic event onsets have been identified to the computer, conduction intervals are measured and electrophysiologic data are calculated. Poststudy analysis systems with basic electrophysiologic analysis protocols have been reported to reduce total average analysis time to approximately 2 hours, 8 about one-half to one-quarter of the time taken to measure the same study manually. 9 Another institution reported their analysis time to be reduced by
220
Journal of Electrocardiology Vol. 22 Supplement
more than two-thirds and the time between study and report production from 2 weeks to 36 hours, l~ Perhaps the greatest benefit may be obtained from systems that complete automated conduction interval measurement and analysis during the electrophysiologic study. Conduction time analysis during protocol execution provides immediate information to confirm the proper operation of each stimulation sequence and, at the end of each protocol, cumulative information regarding the net effect of all stimulation sequences. This analysis feedback allows the user to verify each stimulation sequence and the hypothesis used to investigate an arrhythmia during the study. This early recognition of corrupted or insufficient data avoids the consequences of discovering a problem during post-study analysis. A second benefit of automated interval measurement and analysis is the consistency of results. Although detection and analysis algorithms may be adjustable, once set, computer-generated results are accurate, reproducible, and free of observer bias. One of the earliest reported on-line automated detection systems uses a programmable waveform analyzer to display and measure resting electrophysiologic intervals during cardiac catheterization procedures.1 ~,~x The system measures the R-R cycle length, low right atrium-to-His, and His-to-ventricle intervals automatically. The user identifies the number of events displayed on the waveform analyzer screen and then the automatic detection algorithm uses a combination of peak detection and windowing techniques to search for the electrophysiologic events. A minicomputer-based application was developed for real-time on-line analysis of cardiac electrophysiologic data.X3 The system employs a large CRT screen to display frozen waveforms with event onsets and interevent intervals marked on the traces. In addition, the user can freeze waveform information and page backwards and forwards through on-screen data. Three different processing modes allow event detection for surface lead signals, cardiac electrode signals, and signals with pacer pulses. Two diagnostic systems integrating EP stimulators and real-time automated event detection and analysis have been reported. The AESOP (Automated Electrophysiologic Stimulation and On-Line Processing) system reported a significant reduction in the time required to complete a nontachyarrhythmia induction study (from 2-4 hours to 30-45 minutes) and a final hard copy report (from 5-8 hours to within 5 minutes of study), x4 A second system reported excellent correlation between manual and automatic measurements. 15
Computer Application for an Integrated Electrophysiologic System Analyzer An ideal electrophysiologic system analyzer would aid the user in the rapid completion of an electrophysiologic study. This system would combine electrophysiologic stimulation, digitized waveform data collection, automated electrophysiologic event detection, data analysis, and report generation into a single commercially available system. The stimulator would provide standard, dual-channel, electrophysiologic protocols and rapidly accessible antitachy and antibrady pacing therapies. Data archival would incorporate optical disk technology to allow for continuous multichannel data recording. Automated event onset detection and analysis would summarize the electrophysiologic findings in real time during the study and in hard copy report format upon completion of the study. The final report would have two unique sections, each intended for a different audience. The study summary section would include textual information regarding the patient demographics and history, procedures performed, diagnosis, and the system-supplied data analysis summary. A more detailed data disclosure section would include runby-run onset detection information presented in tabular and/or plotted formats for each type of functional study completed. User-selected waveform segments could be subject to electronic caliper measurement and may also be graphically included in the final report. To meet these objectives, Medtronic is currently developing a commercial electrophysiologic stimulator system. Referred to as MESA (Medtronic Electrophysiologic System Analyzer), the system is technologically derived from the Model 2319 DRI and AESOP research system. MESA is planned to use commercially available computer system components, Medtronic-designed digital and analog hardware, and custom-developed application software. The design is based upon the Hewlett Packard 20 MHz 80386 Vectra Personal Computer. Additional system components include HP VGA video graphics, 100 MB hard disk drive, 3.5-inch microfloppy disk drive, Laser Jet II, Medtronic developed pace-sense (Patient Interface Device) and signal acquisition (Signal Acquisition Interface) modules, commercial eight-channel analog-to-digital conversion card, and a Medtronic-developed microcomputer-based stimulator card (PACE Language Card). The system hardware components are illustrated in Figure 1. MESA application software is comprised of six TM
TM
TM
Computer Application to EP Testing
"
m
m
III
I
9 Gillette et al.
III
221
I
i .......................................................................ii)
o
0
t I
v
20 MHz 586 AT PC
~
=
VGA Graphics
\
9 =
-
N
N Laser Jet II
=,,=1;f
Commercial A / D
~
I1
|
@|174
m =_ o=
PACE Language Card
|
|
Custom EP Keyboard Signal Acquisition Patient Interface Fig. 1. Medtronic Electrophysiologic Systems Analyzer system hardware components.
is run only once after each system power on. The results of the diagnostics determine whether the system is deemed operational. If not, the user is prevented from operating the MESA TM system. The second subsystem is referred to as the System
subsystems, with each subsystem responsible for a group of related functions. Figure 2 illustrates the software hierarchy between the software functional subsystems and support software. The first subsystem is the System Diagnostics. This
System Manager
/
PLC
Detection
Analysis
\
File I/0
Data File Fig. 2. Software hierarchy.
Report File
222
Journal of Electrocardiology Vol. 22 Supplement
Manager. This subsystem's function is to display current system operation status and provide a user interface to the remaining four subsystems. The EP Stimulator subsystem provides stimulation control, data collection, data display, and data analysis functionality pertinent the EP protocols. Included w i t h the stimulator are 11 standard protocols and the ability to create user-defined versions of standard protocols. Data collected during operating of the stimulator can be graphically reviewed o n the video interface in the Data Review subsystem. The collected data include the amplitude of the w a v e f o r m versus time and the results of the automatic event onset detection superimposed u p o n the waveform. The user m a y override the automatic detection algorithm's temporal p l a c e m e n t of onset indicators by manually editing the location of detection indicator. Electronic calipers allow the user to measure and m a r k temporal differences on waveforms. The user m a y select any displayed screen graphics image for inclusion in the final report. Patient information, collected data, the results of the data analysis, and any w a v e f o r m image graphics can be placed o n hard copy via the Report Generator subsystem. The report is comprised of user- and syst e m - g e n e r a t e d data. The system-generated data include electrophysiologic event onset temporal reference times, relationships b e t w e e n these reference times, graphs of these relationships, and any userc a p t u r e d - w a v e f o r m display images. The user-generated data include patient identification and formatfree text. The Data Utilities subsystem allows the user tom a n i p u l a t e MESA TM data files and obtain current data file status information. Also, the user is able to transfer patient report files to and from the microfloppy.
Conclusion A m i c r o c o m p u t e r - b a s e d electrophysiologic system analyzer combining computer-assisted protocol operation, a u t o m a t e d event detection and analysis, data collection and archival, and patient report capability promises to provide an extremely useful and cost-effective tool for clinical and research electrophysiologic studies.
References 1. Rosenthal S, Hasan G, Ruskin J: A portable microprocessor-based system for the electrophysiological study of ventricular arrhythmias. Comput Cardiol 427, 1983 2. Gallais-Hamonno F, Lafortune R, Guardo M et al: A micro-computer based stimulator for cardiac pacing and response analysis during endocavitary investigations. Comput Cardiol 35, I980 3. Van Der Steld A, Dassen W, Gorgels A et al: Flexible multiprocessor system to support electrophysiologic investigation in animals. Comput Cardiol 525, 1984 4. Cochrane T, Nathan A, Butrous Get al: Software control of sensing and stimulation for cardiac electrophysiological study. Int J Bio-Med Comput 15:225, 1984 5. Ross D, Farre J, Bar F et al: Comprehensive clinical electrophysiologic studies in the investigation of documented or suspected tachycardias: time, staff, problems a n d cost. Circulation 61:101 O, 1979 6. Sarma J, Bhandari A, Bilitch M et al: Stimulators for cardiac electrophysiologic studies: a product review. Clin Prog Pacing and Electrophysiol 2:4, 1984 7. Billette J, Guardo R, Bertrand M e t al: A microcomputer-based stimulator for clinical and experimental investigations in cardiac electrophysiology. PACE 2:20, 1979 8. Beinlich I, Neumann G, Nash E et al: HIS-bundle electrogram interrpretation system. Comput Cardiol 509, 1982 9. Cochrane T, Dunlop A, Nathan A et al: Cardiac electrophysiological studies: computer analysis user a digitiser and interactive visual display unit. Clin Phys Physiol Meas 4:321, 10. Nash E, Beinlich I, Anderson K et al: A computerized cardiac electrophysiologic analysis system. Comput Cardiol 233, 1982 11. Gillette P, Garson A, Zinner A et al: Automated online measurement of electrophysiologic intervals during cardiac catheterization. PACE 3:456, 1980 12. Gillette P, Garcon A, Zinner A et al: Continuous computer automated measurement of electrophysiologic data during cardiac catheterization. Comput Cardiol 391, 1980 13. Cooper T, Hess R, Litvin Yet al: A computer system for electrophysiologic studies of cardiac rhythm in humans. Comput Cardiol 299, 1981 14. Biallas R, Ziimer A, Gillette P: Automated electrophysiologic stimulation and on-line proessing. Comput Cardiol 181, 1985 15. Antolini R, Kirchner M, Mongera A et al: On-line interval measurement during invasive cardiac electrophysiologic testing. PACE 11:33, 1988
P. Gillette, MD,* M. Zmijewski, M S , t a n d M. B. S h e l t o n , M S E E t
states of the microprocessor. These states dictate how the associated hardware, such as the pace-sense and user-interface hardware, are to behave. The stimulator's functional behavior as defined by the software is highly flexible and is typically limited only by the processing capabilities of the hardware. The flexibility of the controlling software allows for functional modifications and updates without necessarily changing the physical hardware; the existing software is simply exchanged with the revised software. Stimulator software, however, is generally restricted to control only a specific type of stimulator hardware due to the uniqueness of each microprocessor- and/ or microcomputer-based system. A microcomputer is an excellent hardware platform for a cardiac stimulator. Integrating the microprocessor circuitry with video, printer, and storage media (eg, a floppy disk) hardware components, a microcomputer provides the resources necessary for real-time process control, a user interface, report generation, and data collection. Given the advent of the microcomputer, increasingly sophisticated microcomputer-based stimulator applications have been developed for both clinical and commercial settings, which provide powerful tools for the electrophysiologist. One of the early microcomputer-based cardiac stimulators commercially available as a custom device was the Programmable Cardiac Stimulator, Model PCS-80, developed at the University of Montreal. 6 The Model PCS-80 is comprised of a microcomputer, a video display (CRT) and keyboard user interface, and an isolated dual-port stimulation interface. Included with the stimulator are standard stimulation protocols and the ability for the user to define protocols using a sequence of up to l0 software-defined pulse generators. Through software control, i0 real-time pulse generators with individ-
A wide variety of computer-based research stimulators have been developed for clinical and experimental use in cardiac electrophysiology.~-4 These devices provide users with stimulators whose primary logic is embodied in software, rather than hardware. Computer-based stimulators provide a system in which the user is typically able to adjust stimulation sequence timing and output parameter values manually or automatically through software control. Given the time-consuming and tedius nature of an electrophysiologic test and subsequent data analysis, 5 computer-based applications have been developed to reduce both the study and data analysis time.
Computer Application in Stimulator Design A microprocessor-based stimulator that typically combines microprocessor and analog circuitry with user interface provides a highly flexible, low-cost system upon which sophisticated functional applications may be developed. The microprocessorbased portion of the stimulator circuitry is comprised of discrete-logic integrated chips, such as the central processing unit (CPU), read-only memory (ROM), and random-access memory (RAM). In combination with software, a microprocessor can provide precise control of the analog portion of the stimulator hardware. Software is the sequence of steps defining the logic
* From the Medical University of South Carolina, Charleston, South Carolina. t From Medtronic Inc., Minneapolis, Minnesota. Reprint requests: M. Brent Shelton, Medtronic, 7000 Central Avenue MS T415, Minneapolis, MN 55432.
218
Computer Application to EP Testing
ually adjustable parameters may be cascaded to deliver stimulation sequences. A description of the stimulator detailed how the device can automatically be adjusted to deliver pulse patterns with periodic and cyclic modifiers. Beat-to-beat parameter variations may be produced by periodic modifiers, while sequence-to-sequence parameter variations parameters may be produced with cyclic modifiers. Adjustable parameters include pulse amplitude, pulse duration, and stimulus coupling intervals, such as drive train and premature stimuli.7 The Cordis Corporation developed a stimulator based on the Digital Equipment PC-350. Available only as a special-order prescription device, this system includes a microcomputer, a video display and keyboard user interface, a printer, and a dual-channel stimulation module. Hardware controls on the stimulation module allow for the independent adjustment of pulse amplitude, pulse width, and sensitivity on each channel. Standard stimulation protocols as well as AAI, VVI, and DDD pacemaker emulation protocols are controlled through software. The stimulation patterns can be user-defined and stored for quick recovery. Medtronic Incorporated developed a truly programmable dual-channel stimulator. In contrast the to above-described stimulators, the Model 2319 Dysrhythmia Research Instrument (DRI) allowed the user to define a protocol's sequence of operation completely, through the use of a Medtronic developed programming language called PACE. The PACE programming language includes statements such as Pace, Delay, Goto, On Sense Goto, If Condition Exists Goto. Each PACE statement has its own characteristic parameters. The DRI, available only as a custom device, consists of three components: the controlling Host microcomputer, the Digital Controller, and the Patient Interface Module. Connected between the Digital Controller and the patient, the Patient Interface Module hardware controls pacing and sensing functions. The Digital Controller communicates with the Host microcomputer during protocol execution via a IEEE-488 Standard interface. In conjunction with the Patient Interface Module, the Digital Controller executes the PACE protocols developed on the Host computer. The Host computer not only provides a PACE protocol editor with which to develop protocols, but provides a user interface for direct protocol control during protocol execution. To date, via the IEEE-488 interface, the DRI has been configured with three different microcomputers: Hewlett-Packard HP-85, a Digital Equipment Corporation PDP 11/23, and a IBM Personal Computer. The Model EP-2 Stimulator, developed by Digital Cardiovascular Instruments Incorporated, is a corn-
9 Gillette et
al,
219
mercially available FDA-approved dual-channel stimulator intended for clinical and experimental electrophysiologic studies of the heart. The batteryoperated device is comprised of a custom-based unit housing both the microcomputer and isolated pacesense circuitry, a video monitor and keyboard user interface, and a serial communications port for the attachment of a printer. All pacing and protocol execution parameters can be manually or automatically controlled through software. Nine standard stimulation protocols and several arrhythmia termination protocol are available through a single keystroke. In addition, customized versions of the standardized protocols may be assigned to five programmable keys, thus making preset versions of any protocol available via a single keystroke.
Computer Application in Automatic Event Detection and Analysis Although a computer-based electrophysiologic stimulator allows for precise and repeatable automation of protocol execution, the true utility of a computer-based stimulator is the additional software-based applications that may be integrated into the system. These applications include patient data management, waveform digitization and archival storage, and, perhaps most significant, electrophysiologic event onset detection and interval analysis. Several successful research computer applications for poststudy and during-study analysis of electrophysiologic data have been developed. Computerbased post-study analysisapplications typically require the user to indicate the electrogram event onsets through the use of a digitization board. The user indicates event onsets by placing electrophysiologic tracings recorded on paper during the study over the digitization board, specifies the onset points to be indicated on the digitizer pad, and then moves the digitizer board's input pen or mouse to the tracing locations for each of the specified points. This process is repeated for each event to be measured. When all electrophysiologic event onsets have been identified to the computer, conduction intervals are measured and electrophysiologic data are calculated. Poststudy analysis systems with basic electrophysiologic analysis protocols have been reported to reduce total average analysis time to approximately 2 hours, 8 about one-half to one-quarter of the time taken to measure the same study manually. 9 Another institution reported their analysis time to be reduced by
220
Journal of Electrocardiology Vol. 22 Supplement
more than two-thirds and the time between study and report production from 2 weeks to 36 hours, l~ Perhaps the greatest benefit may be obtained from systems that complete automated conduction interval measurement and analysis during the electrophysiologic study. Conduction time analysis during protocol execution provides immediate information to confirm the proper operation of each stimulation sequence and, at the end of each protocol, cumulative information regarding the net effect of all stimulation sequences. This analysis feedback allows the user to verify each stimulation sequence and the hypothesis used to investigate an arrhythmia during the study. This early recognition of corrupted or insufficient data avoids the consequences of discovering a problem during post-study analysis. A second benefit of automated interval measurement and analysis is the consistency of results. Although detection and analysis algorithms may be adjustable, once set, computer-generated results are accurate, reproducible, and free of observer bias. One of the earliest reported on-line automated detection systems uses a programmable waveform analyzer to display and measure resting electrophysiologic intervals during cardiac catheterization procedures.1 ~,~x The system measures the R-R cycle length, low right atrium-to-His, and His-to-ventricle intervals automatically. The user identifies the number of events displayed on the waveform analyzer screen and then the automatic detection algorithm uses a combination of peak detection and windowing techniques to search for the electrophysiologic events. A minicomputer-based application was developed for real-time on-line analysis of cardiac electrophysiologic data.X3 The system employs a large CRT screen to display frozen waveforms with event onsets and interevent intervals marked on the traces. In addition, the user can freeze waveform information and page backwards and forwards through on-screen data. Three different processing modes allow event detection for surface lead signals, cardiac electrode signals, and signals with pacer pulses. Two diagnostic systems integrating EP stimulators and real-time automated event detection and analysis have been reported. The AESOP (Automated Electrophysiologic Stimulation and On-Line Processing) system reported a significant reduction in the time required to complete a nontachyarrhythmia induction study (from 2-4 hours to 30-45 minutes) and a final hard copy report (from 5-8 hours to within 5 minutes of study), x4 A second system reported excellent correlation between manual and automatic measurements. 15
Computer Application for an Integrated Electrophysiologic System Analyzer An ideal electrophysiologic system analyzer would aid the user in the rapid completion of an electrophysiologic study. This system would combine electrophysiologic stimulation, digitized waveform data collection, automated electrophysiologic event detection, data analysis, and report generation into a single commercially available system. The stimulator would provide standard, dual-channel, electrophysiologic protocols and rapidly accessible antitachy and antibrady pacing therapies. Data archival would incorporate optical disk technology to allow for continuous multichannel data recording. Automated event onset detection and analysis would summarize the electrophysiologic findings in real time during the study and in hard copy report format upon completion of the study. The final report would have two unique sections, each intended for a different audience. The study summary section would include textual information regarding the patient demographics and history, procedures performed, diagnosis, and the system-supplied data analysis summary. A more detailed data disclosure section would include runby-run onset detection information presented in tabular and/or plotted formats for each type of functional study completed. User-selected waveform segments could be subject to electronic caliper measurement and may also be graphically included in the final report. To meet these objectives, Medtronic is currently developing a commercial electrophysiologic stimulator system. Referred to as MESA (Medtronic Electrophysiologic System Analyzer), the system is technologically derived from the Model 2319 DRI and AESOP research system. MESA is planned to use commercially available computer system components, Medtronic-designed digital and analog hardware, and custom-developed application software. The design is based upon the Hewlett Packard 20 MHz 80386 Vectra Personal Computer. Additional system components include HP VGA video graphics, 100 MB hard disk drive, 3.5-inch microfloppy disk drive, Laser Jet II, Medtronic developed pace-sense (Patient Interface Device) and signal acquisition (Signal Acquisition Interface) modules, commercial eight-channel analog-to-digital conversion card, and a Medtronic-developed microcomputer-based stimulator card (PACE Language Card). The system hardware components are illustrated in Figure 1. MESA application software is comprised of six TM
TM
TM
Computer Application to EP Testing
"
m
m
III
I
9 Gillette et al.
III
221
I
i .......................................................................ii)
o
0
t I
v
20 MHz 586 AT PC
~
=
VGA Graphics
\
9 =
-
N
N Laser Jet II
=,,=1;f
Commercial A / D
~
I1
|
@|174
m =_ o=
PACE Language Card
|
|
Custom EP Keyboard Signal Acquisition Patient Interface Fig. 1. Medtronic Electrophysiologic Systems Analyzer system hardware components.
is run only once after each system power on. The results of the diagnostics determine whether the system is deemed operational. If not, the user is prevented from operating the MESA TM system. The second subsystem is referred to as the System
subsystems, with each subsystem responsible for a group of related functions. Figure 2 illustrates the software hierarchy between the software functional subsystems and support software. The first subsystem is the System Diagnostics. This
System Manager
/
PLC
Detection
Analysis
\
File I/0
Data File Fig. 2. Software hierarchy.
Report File
222
Journal of Electrocardiology Vol. 22 Supplement
Manager. This subsystem's function is to display current system operation status and provide a user interface to the remaining four subsystems. The EP Stimulator subsystem provides stimulation control, data collection, data display, and data analysis functionality pertinent the EP protocols. Included w i t h the stimulator are 11 standard protocols and the ability to create user-defined versions of standard protocols. Data collected during operating of the stimulator can be graphically reviewed o n the video interface in the Data Review subsystem. The collected data include the amplitude of the w a v e f o r m versus time and the results of the automatic event onset detection superimposed u p o n the waveform. The user m a y override the automatic detection algorithm's temporal p l a c e m e n t of onset indicators by manually editing the location of detection indicator. Electronic calipers allow the user to measure and m a r k temporal differences on waveforms. The user m a y select any displayed screen graphics image for inclusion in the final report. Patient information, collected data, the results of the data analysis, and any w a v e f o r m image graphics can be placed o n hard copy via the Report Generator subsystem. The report is comprised of user- and syst e m - g e n e r a t e d data. The system-generated data include electrophysiologic event onset temporal reference times, relationships b e t w e e n these reference times, graphs of these relationships, and any userc a p t u r e d - w a v e f o r m display images. The user-generated data include patient identification and formatfree text. The Data Utilities subsystem allows the user tom a n i p u l a t e MESA TM data files and obtain current data file status information. Also, the user is able to transfer patient report files to and from the microfloppy.
Conclusion A m i c r o c o m p u t e r - b a s e d electrophysiologic system analyzer combining computer-assisted protocol operation, a u t o m a t e d event detection and analysis, data collection and archival, and patient report capability promises to provide an extremely useful and cost-effective tool for clinical and research electrophysiologic studies.
References 1. Rosenthal S, Hasan G, Ruskin J: A portable microprocessor-based system for the electrophysiological study of ventricular arrhythmias. Comput Cardiol 427, 1983 2. Gallais-Hamonno F, Lafortune R, Guardo M et al: A micro-computer based stimulator for cardiac pacing and response analysis during endocavitary investigations. Comput Cardiol 35, I980 3. Van Der Steld A, Dassen W, Gorgels A et al: Flexible multiprocessor system to support electrophysiologic investigation in animals. Comput Cardiol 525, 1984 4. Cochrane T, Nathan A, Butrous Get al: Software control of sensing and stimulation for cardiac electrophysiological study. Int J Bio-Med Comput 15:225, 1984 5. Ross D, Farre J, Bar F et al: Comprehensive clinical electrophysiologic studies in the investigation of documented or suspected tachycardias: time, staff, problems a n d cost. Circulation 61:101 O, 1979 6. Sarma J, Bhandari A, Bilitch M et al: Stimulators for cardiac electrophysiologic studies: a product review. Clin Prog Pacing and Electrophysiol 2:4, 1984 7. Billette J, Guardo R, Bertrand M e t al: A microcomputer-based stimulator for clinical and experimental investigations in cardiac electrophysiology. PACE 2:20, 1979 8. Beinlich I, Neumann G, Nash E et al: HIS-bundle electrogram interrpretation system. Comput Cardiol 509, 1982 9. Cochrane T, Dunlop A, Nathan A et al: Cardiac electrophysiological studies: computer analysis user a digitiser and interactive visual display unit. Clin Phys Physiol Meas 4:321, 10. Nash E, Beinlich I, Anderson K et al: A computerized cardiac electrophysiologic analysis system. Comput Cardiol 233, 1982 11. Gillette P, Garson A, Zinner A et al: Automated online measurement of electrophysiologic intervals during cardiac catheterization. PACE 3:456, 1980 12. Gillette P, Garcon A, Zinner A et al: Continuous computer automated measurement of electrophysiologic data during cardiac catheterization. Comput Cardiol 391, 1980 13. Cooper T, Hess R, Litvin Yet al: A computer system for electrophysiologic studies of cardiac rhythm in humans. Comput Cardiol 299, 1981 14. Biallas R, Ziimer A, Gillette P: Automated electrophysiologic stimulation and on-line proessing. Comput Cardiol 181, 1985 15. Antolini R, Kirchner M, Mongera A et al: On-line interval measurement during invasive cardiac electrophysiologic testing. PACE 11:33, 1988